Optimizing Inventory and Yield Data Collection for Forest Management Planning - Horacio Gilabert; Marc E. McDill (Forest Science, 2010)
This work uses a Cost+Loss approach to estimate the optimal investment in inventory information for forest planning. A bootstrapping approach is used to simulate the impact of different inventory intensities on the quality of decisions in a linear programming harvest scheduling model. Multiple formulations of the harvest model based on varying inventory intensities are used to calculate the value of a variable labeled Loss that measures the monetary losses resulting from the use of imperfect yield information in the harvest model. The variable Loss and the cost of obtaining the inventory information are used to estimate empirical relationships between their expected value and the amount of inventory information (number of inventory plots and number of experimental plots) used in the harvest models. These two relationships are combined to give an explicit estimate of the expected Cost+Loss as a function of the inventory intensity variables. This Cost+Loss relationship is minimized to estimate optimal number of inventory plots and the optimal number of experimental plots. An example is developed with radiata pine information from southern Chile. Results for this example suggest that current practice uses too many experimental plots and too few inventory plots.

Private Net Benefits from Afforesting Marginal Cropland and Shrubland with Cork Oaks in Spain - Paola Ovando; Pablo Campos; José L. Oviedo; Gregorio Montero (Forest Science, 2010)
We estimate the private net benefits from afforesting marginal shrubland and cropland with cork oaks at two Spanish cork oak sites, Aljibe and Gavarres, in different time horizon frames. The analysis integrates market and nonmarket (landowner amenity) private capital incomes, including government afforestation grants. We apply cost-benefit analysis techniques for estimating the investment present value in the periods analyzed, taking residual values of cork oak woodland into account. The results show that the profitability rate of cork oak afforestation strongly depends on government subsidies. The value of private amenities, at least in Aljibe, seems to be positively affected by the forest area's share of the total estate surface. Thus, an increase in the afforested area would enhance the private amenity annual income with respect to maintaining the original property land's treeless uses. A higher level of private amenities attached to the forest area may imply a reduction in government grants for encouraging cork oak afforestation.

Compatibility of Stand Basal Area Predictions Based on Forecast Combination - Xiongqing Zhang; Yuancai Lei; Quang V. Cao (Forest Science, 2010)
Stand growth and yield models include whole-stand models, individual-tree models, and diameter-distribution models. Based on the growth data of Chinese pine (Pinus tabulaeformis Carr.) in Beijing, forecast combination was used to adjust predicted stand basal areas from these three types of models. The forecast combination method combines information and disperses errors from different models to improve forecast performance. In this study, weights of the three model estimates used in the forecast combination estimator were determined by the optimal weight method. Results showed that the forecast combination method provided overall better predictions of stand basal area than the three types of models. It also improved the compatibility of stand basal area growth predicted from models of different resolutions and provided a method for integration of stand basal area.

Sediment Trapping by Streamside Management Zones of Various Widths after Forest Harvest and Site Preparation - William A. Lakel; Wallace M. Aust; M. Chad Bolding; C. Andrew Dolloff; Patrick Keyser; Robert Feldt (Forest Science, 2010)
Recommended widths for streamside management zones (SMZs) for sediment protection vary. The objectives of this study were to compare the effects of SMZ widths and thinning levels on sediment moving through SMZs. Four SMZ treatments were installed within 16 harvested watersheds where intermittent streams graded into small perennial streams. Sites were clearcut, prescribed burned, and planted with loblolly pine (Pinus taeda L.). Treatments were 30.4-, 15.2-, and 7.6-m-wide SMZs without thinning and 15.2-m-wide SMZs with thinning. Three to seven treatments replicated within four blocks created a randomized incomplete block design. Erosion rates from watersheds and sediment trapping within SMZ treatments were monitored with modeling and sediment pins. A second study evaluated 24 subwatersheds within eight watersheds. Three subwatersheds were located within each watershed so sediment traps collected inputs into SMZs from harvest site-prepared areas, firelines, or at streams. SMZ treatments had no significant differences regarding sediment trapping. All SMZs widths were generally effective in trapping sediment. Within the 16 intermittent-perennial watersheds and 24 ephemeral subwatersheds, erosion to sediment delivery ratios from harvests ranged from 3 to 14%. For ephemeral stream subwatersheds, firelines adjacent to SMZs contributed 14% of total sediment. Sediment trap data collected within SMZs indicated that 97% of watershed erosion was trapped before reaching streams. In three subwatersheds, sediment penetrated SMZs due to channelized flow from failed or inadequate water controls on roads and firelines. Results support the common recommendation for SMZ widths of 15.2 m in which partial harvests may occur and emphasize the importance of implementation of best management practices for roads and firelines.

Bootstrap Evaluation of a Young Douglas-Fir Height Growth Model for the Pacific Northwest - Nicholas R. Vaughn; Eric C. Turnblom; Martin W. Ritchie (Forest Science, 2010)
We evaluated the stability of a complex regression model developed to predict the annual height growth of young Douglas-fir. This model is highly nonlinear and is fit in an iterative manner for annual growth coefficients from data with multiple periodic remeasurement intervals. The traditional methods for such a sensitivity analysis either involve laborious math or rely on prior knowledge of parameter behavior. To achieve our goals, we incorporate a bootstrap approach to obtain estimates of the distribution of predicted height growth for any set of input variables. This allows for a sensitivity analysis with knowledge of the probability of a given outcome. The bootstrap distributions should approximate the variation we might expect from running the model on numerous independent datasets. From the variation in the model parameters, we are able to produce ranges of height growth prediction error falling under a given probability of occurrence. By evaluating these ranges under several combinations of input variables that represent extreme situations, we are able to visualize the stability of the model under each situation. Each of the four components of the model can be investigated separately, which allows us to determine which components of the model might benefit from reformulation. In this case we find that the model is less stable in extremely high site index, especially under low vegetation competition. Other than the computing time involved with the bootstrap, most of the analysis is fairly quick and easy to perform.

Measuring the Value of Information in Multicriteria Decisionmaking - Annika S. Kangas; Paula Horne; Pekka Leskinen (Forest Science, 2010)
Decisions in forestry typically include uncertainty. The decisionmaker then has two options: either to make the optimal choice between different alternative actions with the current information or to try to reduce the uncertainty by collecting more information. The value of information is due to the ability to make better decisions with new information. When the decisions only affect provision of goods that have market value, evaluation of alternative decisions is in principle a straightforward exercise of cost-benefit analysis. In sustainable forest management, however, multiple objectives typically exist, and these objectives may be related to provision of public goods and services. Because such goods and services cannot be directly measured in monetary terms, the problem of value of information is more complicated. The possible solutions are to assess the monetary value separately for all goods and services and evaluate the decisions with cost-benefit analysis or to evaluate the decisions in terms of utility with multicriteria analysis and calculate the (monetary) value of decisions based on these utilities. The aim of this study was to present these two cases for evaluating decisions and analyze their similarities and differences and to discuss the usefulness of these approaches in evaluating the value of information from different perspectives.

Taper Models for Commercial Tree Species in the Northeastern United States - James A. Westfall; Charles T. Scott (Forest Science, 2010)
A new taper model was developed based on the switching taper model of Valentine and Gregoire; the most substantial changes were reformulation to incorporate estimated join points and modification of a switching function. Random-effects parameters were included that account for within-tree correlations and allow for customized calibration to each individual tree. The new model was applied to 19 species groups from data collected on 2,448 trees across the northeastern United States. A comparison of fit statistics showed considerable improvement for the new model. The residuals occurred near the tree base, whereas the residuals standardized in relation to tree diameter were generally constant along the length of the stem. There was substantial variability in the rate of taper at the base of the tree, particularly for trees with relatively Similar trends were found in independent validation data. The use of random effects allows uncertainty in computed tree volumes to compare favorably with another regional taper equation that uses upper-stem diameter information for local calibration. However, comparisons with a locally developed model showed that the local model provided more precise estimates of volume.

Evaluation of Parameter Estimation Methods for Fitting Spatial Regression Models - Junfeng Lu; Lianjun Zhang (Forest Science, 2010)
Two types of spatial regression models, a spatial lag model (SLM) and a spatial error model (SEM), were applied to fit the height-diameter relationship of trees. SEM had better model fitting and performance than both SLM and ordinary least squares. Moran's I coefficients showed that SEM effectively reduced the spatial autocorrelation in the model residuals. Both real data and Monte Carlo simulations were used to compare different parameter estimation methods for the two spatial regression models, including maximum likelihood estimation (MLE), Bayesian methods, two-stage least squares (for SLM) and generalized method of moments (GMM) (for SEM). Our results indicated that GMM was close to MLE in terms of model fitting, much easier in computation, and robust to non-normality and outliers. The Bayesian method with heteroscedasticity did not effectively estimate the spatial autoregressive parameters but produced very small biases for the regression coefficients of the model when few outliers existed.

Valuation of Timber Harvest Contracts as American Call Options with Modified Least-Squares Monte Carlo Algorithm - Stanislav Petrasek; John M. Perez-Garcia (Forest Science, 2010)
This article presents a Monte Carlo methodology for the valuation of timber harvest contracts in the presence of stochastic timber prices, flexibility in harvest timing, and penalty clauses. Harvest contracts are treated as American call options on the value of timber. The modifications to the least-squares Monte Carlo algorithm necessary to incorporate penalty clauses are presented. The application of the proposed methodology is then demonstrated on a valuation problem characteristic of harvest contracts sold by the Washington Department of Natural Resources.

The Effects of Irrigation and Fertilization on Specific Gravity of Loblolly Pine - Kimberly R. Love-Myers; Alexander Clark; Laurence R. Schimleck; Phillip M. Dougherty; Richard F. Daniels (Forest Science, 2010)
The effects of two treatments, irrigation and fertilization, were examined on specific gravity (SG)-related wood properties of loblolly pine trees (Pinus taeda L.) grown in Scotland County, North Carolina. The effects on the core as a whole, on the juvenile core, on the mature core, and from year to year were all analyzed. The results indicate that fertilization significantly lowered latewood SG, overall SG, and percent latewood and did so consistently throughout the period of study. Irrigation significantly lowered earlywood SG during the phase of juvenile wood production but significantly raised latewood SG during the period of mature wood production. Significant interaction between fertilization and irrigation indicated that irrigation helped overall SG and percent latewood of fertilized trees to increase to the level of untreated trees. Therefore, this study provides evidence that although fertilization significantly affects several SG-related properties, water availability is beneficial to the fertilization process; over time, an adequate water supply may help fertilized trees to maintain SG levels similar to those of unfertilized trees.

Ponderosa Pine Characteristics Associated with Attack by the Roundheaded Pine Beetle - Melissa J. Fischer; Kristen M. Waring; Richard W. Hofstetter; Thomas E. Kolb (Forest Science, 2010)
The roundheaded pine beetle (Dendroctonus adjunctus Blandford [Coleoptera: Curculionidae, Scolytinae]) is an aggressive (tree-killing) bark beetle species that attacks several species of pine. Characteristics of ponderosa pine (Pinus ponderosa Dougl. ex Laws.) trees chosen for attack by this beetle were studied in a current outbreak in northern Arizona. We found significant differences in basal area increment, crown width, lengths of internodes, subbranches, and needles, phloem thickness, and resin composition between attacked and unattacked trees. Attacked trees had significantly lower basal area increment and internode and needle lengths but longer subbranch lengths at the top of the crown and longer crown widths. Attacked trees also had thicker phloem and contained a significantly higher percentage of α-pinene in resin, but a lower percentage of longifolene than unattacked trees. A baited tree experiment showed that attacks by the roundheaded pine beetle did not affect resin composition through time. Overall, our results suggest that host selection by the roundheaded pine beetle may not be random and that tree growth characteristics and resin composition are probably important factors in host selection.

Genetic Variation of Stem Forking in Loblolly Pine - Jin S. Xiong; Fikret Isik; Steven E. McKeand; Ross W. Whetten (Forest Science, 2010)
Forking defects were studied in loblolly pine (Pinus taeda L.) in 6-year-old genetic tests from the second cycle of breeding in the North Carolina State University Cooperative Tree Improvement Program. Data were available from 268 test series (each with two 6-parent half-diallel mating designs, with 12 parents, 30 crosses, and 144 progeny per cross) over six geographic regions. A subset of 123 series with average forking between 20 and 80% was used for genetic analysis. Forking differed significantly among regions, with the highest in the Upper Gulf Coastal Plain (24%) and the lowest in the Georgia-Florida Coastal Plain (12%). The individual-tree heritabilities were low (0.06), but the half-sib (0.76), narrow-sense full-sib (0.59), and broad-sense full-sib (0.71) family-mean heritabilities were moderately high. This result suggests that forking is partially under genetic control at the family level, but at the individual tree level, it is mostly determined by the environment. Genetic gain was estimated for half-sib family selection with a selection differential of 20%. Gain ranged from 12 to 23% reduction in forking across different regions. A weak unfavorable genetic correlation (0.18) was found between forking and height, suggesting that selection for growth alone will negatively affect forking in loblolly pine. A favorable genetic correlation (0.33) was found between forking and straightness.

Forest Harvesting and Environmental Protection Based on the Goal Programming Approach - Matias Silva; Andres Weintraub; Carlos Romero; Carmen De la Maza (Forest Science, 2010)
This study focuses on a medium-term forest harvesting problem considering the protection of environmental components such as soil, water resources, and landscape. A mathematical model that elaborates different environmental protection alternatives for each environmental component and the net present value of the forest company was developed. This is a mixed-integer linear programming model based on the lexicographic goal programming approach. The results obtained using this model show clearly the conflict that exists between the environmental protection and the net present value of the forest company, but, more important, this model allows one to obtain equilibrated solutions in terms of both the environmental components and the economic criterion.

Effects of Planting Density and Seed Source on Loblolly Pine Stands in Southeastern Oklahoma - Rodney Will; Thomas Hennessey; Thomas Lynch; Randal Holeman; Robert Heinemann (Forest Science, 2010)
Since the early 1970s, loblolly pine (Pinus taeda L.) plantations have been established west of the native range of the species in the Ouachita Mountains of Oklahoma, using faster-growing seed sources from coastal North Carolina (NCC) rather than Oklahoma or Arkansas (O/A). Although the NCC sources outperform O/A sources early in stand development, it is not known how these provenances will perform later in stand development when density-dependent mortality is occurring. We tested the effects of planting density (1,075, 1,680, 2,990, and 6,725 trees ha−1) and seed source (NCC and O/A) on stand and tree attributes for 25-year-old plantations located on a droughty, mountain soil in southeastern Oklahoma. Survival decreased with increasing stand density but did not differ among sources. Average tree diameter also decreased with increasing planting density (25.5 to 15.8 cm), and, again, the pattern was consistent across provenances. Average tree heights decreased with stand density (18.6 to 16.8 m); however, the NCC seed source was taller than the O/A seed source (18.4 versus 17.0 m). This resulted in NCC stands maintaining greater stand volume than O/A stands (329 versus 301 m3 ha−1). Basal area was similar among seed sources and did not significantly differ among densities (average 49.0 m2 ha−1). These results indicate that over 25 years, the NCC seed source performed better than the regional seed source even when grown under extremely high densities and experiencing density-dependent mortality.

Evaluating the Financial Performance of Timberland Investments in the United States - Bin Mei; Michael L. Clutter (Forest Science, 2010)
Timberland properties have gained increasing attention in recent decades. The attractiveness of this asset primarily lies in its unique feature—the biological growth, which is independent of traditional financial markets. Using both parametric and nonparametric approaches, in this study we reexamine the financial performance of private- and public-equity timberland investments in the United States. Private-equity timberland returns are proxied by the National Council of Real Estate Investment Fiduciaries Timberland Index, whereas public-equity timberland returns are proxied by the value-weighted returns on a dynamic portfolio of the US publicly traded forestry firms that had or have been managing timberlands. The parametric analyses reveal that private-equity timberland assets outperform the market and have low systematic risk, whereas public-equity timberland assets fare similarly to the market. The nonparametric analyses reveal that both private- and public-equity timberland assets have higher excess returns.

A New Look at Spread Rates of Exotic Diseases in North American Forests - Alexander M. Evans; Alex J. Finkral (Forest Science, 2010)
Exotic pathogens threaten ecosystems in novel ways, particularly where they are facilitated by stresses such as climate change and forest fragmentation. Although chestnut blight (CB), Dutch elm disease (DED), beech bark disease (BBD), and white pine blister rust (WPBR) are well-studied pathogens, this investigation is the first to provide estimated rates of spread based on an expansive geospatial database and a consistent, rigorous analytical framework. We use quantile regression to analyze 850 records of infection over the last (20th) century. The results show that in the past, forest disease complexes have spread at rates between 7.4 and 31 km year−1, and two-thirds of the estimates were less than 17 km year−1. We estimated the spread of CB at 31 km year−1, DED in eastern North America at 25 km year−1, DED in western North America at 14 km year−1, BBD at 16 km year−1, WPBR in eastern North America at 7.4 km year−1, and WPBR in western North America at 10 km year−1. These results do not predict the rate of spread of future exotic pathogens in North American forests; rather they provide context for predictive models and a heuristic guide until more scientific data are available.

Adoption of Woodland Management Practices by Private Forest Owners in Virginia - Maminiaina S. Rasamoelina; James E. Johnson; R. Bruce Hull (Forest Science, 2010)
Sustainable management of private forests is a key issue to ensure sound rural economics and a flow of ecosystem benefits. Logistic regression models for the adoption of woodland management practices by Virginia private forest owners were developed, and they correctly classified between 66 and 89% of the cases. Separate models were developed for specific practices that improve forest health and productivity or protection and general practices associated with any type of rural landownership, such as surveying property boundary lines. For specific practices, adoption was most influenced by the use of technical assistance, followed by use of a written management plan, economic motivations, and attendance at educational programs. Probabilities of adoption ranged from 3% for forest owners who did not have any technical assistance nor used a management plan and had low economic motivations to 70% for owners who had technical assistance, used a management plan, and had high economic motivation. The general management practices were adopted at a higher rate (from 51 to 99%) and were predicted by landowners’ use of financial assistance, recreational motivations, and economic motivations.

Population Estimation Using Partial Double Sampling - Craig Loehle (Forest Science, 2010)
Detectability issues create uncertainty in field surveys of populations. Methods to overcome this problem include mark-recapture methods and double sampling. Partial double sampling involves estimating detectability, <inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="carrot-p.tif"/>, and using this to correct the estimate in areas sampled only once. Results of this study indicate that, if population density is not uniform across sample units, there is a tradeoff for a given sampling effort, with lower population estimation error for double sampling only a portion of the area when spatial variance and/or detectability are lower but lower error for partial double sampling when spatial variance and/or detectability are higher. Thus, whereas standard double sampling increases precision, it does not give adequate accuracy in the face of spatial variation unless the entire area can be surveyed twice, which is more expensive.

Synthesis of Regional Wildlife and Vegetation Field Studies to Guide Management of Standing and Down Dead Trees - Bruce G. Marcot; Janet L. Ohmann; Kim Mellen-McLean; Karen L. Waddell (Forest Science, 2010)
We used novel methods for combining information from wildlife and vegetation field studies to develop guidelines for managing dead wood for wildlife and biodiversity. The DecAID Decayed Wood Advisor presents data on wildlife use of standing and down dead trees (snags and down wood) and summaries of regional vegetation plot data depicting dead wood conditions, for forests across the Pacific Northwest United States. We combined data on wildlife use by snag diameter and density and by down wood diameter and cover, across studies, using parametric techniques of meta-analysis. We calculated tolerance intervals, which represent the percentage of each species' population that uses particular sizes or amounts of snags and down wood, and rank-ordered the species into cumulative species curves. We combined data on snags and down wood from > 16,000 field plots from three regional forest inventories and calculated distribution-free tolerance intervals compatible with those compiled for wildlife to facilitate integrated analysis. We illustrate our methods using an example for one vegetation condition. The statistical summaries in DecAID use a probabilistic approach, which works well in a risk analysis and management framework, rather than a deterministic approach. Our methods may prove useful to others faced with similar problems of combining information across studies in other regions or for other data types.

Two-Component Mixture Models for Diameter Distributions in Mixed-Species, Two-Age Cohort Stands - Rafał Podlaski (Forest Science, 2010)
The objectives of this study were to investigate the suitability of two-component Weibull and gamma mixtures to model the dbh distribution of a mixed-species, two-age cohort stands and for age cohort determination and to compare several methods to choose initial parameter values for maximum likelihood estimation of mixture models. Investigations were carried out in near-natural, fir (Abies alba Mill.)–beech (Fagus sylvatica L.), two-age cohort stands in the Świętokrzyski National Park (Central Poland), where unusually high mortality of fir followed by its recovery and revitalization has been observed. The age cohort YG1 is composed of trees from 60 to ∼150 years of breast height age, and the age cohort YG2 is composed of trees less than 60 years of breast height age. The empirical distributions for the stands in this study were equally well fit by both the mixture Weibull and gamma models. It has been assumed that the estimated values, the weights (fractions), the means, and the standard deviations of two-component mixture models, are the predicted values of dbh statistics of age cohorts. The mean absolute relative errors used to evaluate this assumption were least for age cohort YG2 (from 14.8 to 29.6%) and largest for age cohort YG1 (from 17.7 to 45.0%). The dbh component 1 of mixture models can be identified in the stands investigated with age cohort YG2 and to a lesser degree the dbh component 2 with age cohort YG1. The multistart method for choosing initial values for the numerical procedure (a combination of the expectation-maximization algorithm with the Newton-type method) was best but also the most labor-intensive. The optimal way to estimate parameters in two-component mixtures with the Weibull or the gamma distributions is to apply min/max and 0.5/1.5/mean methods and, additionally, but only if necessary, a multistart method.

Using Linear Mixed Effects in Helicopter Logging Data - Kevin Lyons; Li Xing; John D. Nelson (Forest Science, 2010)
This article applies a linear mixed-effects model (LME) to an unpublished helicopter logging productivity data set. The data were clustered in units, and the silviculture treatments varied between units, where units are cutblocks. When the covariance matrix was considered, it was found that the interunit variance was significant and the intraunit variance was heterogeneous. The significant interunit variance results in significant intraunit correlation, and this indicates the need to use LME to analyze these data. When turn time was considered, unit 4, which had the lowest level of group retention, had a conditional predicted value that was significantly less than the marginal predicted value. When turn weight was considered, unit 2, which had small patch cuts, had a conditional predicted value that was significantly less than the marginal predicted value, and unit 4 had a conditional predicted value that was significantly higher than the marginal predicted value. When productivity was considered, the conditional predicted value for unit 4 was significantly greater than the marginal predicted value, and unit 2 was significantly less than the marginal predicted value. In this data set it is interesting to note that productivity is independent of the number of logs in a turn and that turn weight was relatively insensitive to the available explanatory variables.

Stand Density Relationships in Baldcypress - Richard F. Keim; Thomas J. Dean; Jim L. Chambers; William H. Conner (Forest Science, 2010)
Stand density indices (SDIs) are surrogate measures of site occupancy useful for developing quantitative management tools for forest types that have not been extensively studied. For example, there has been little research of growth-density relationships for baldcypress (Taxodium distichum [L.] L.C. Rich.). We used published data, forest inventory data, and a 25-year-old thinning study to identify maximum densities and density of incipient self-thinning in baldcypress. Results suggest that a maximum Reineke's SDI is approximately 1,200 (SI units) in baldcypress, which agrees with practical experience and the theoretical limit derived from observed correlations between a species wood density and maximum SDI. Thinning a baldcypress stand to ≥58% of maximum SDI did not affect tree-level or stand-level growth, but thinning to 40% of maximum SDI increased diameter increment and net volume increment (at α = 0.07) in the first 25 years after thinning. These results are consistent with expectations based on stand density-growth relationships for other species, which supports the general utility of management tools based on stand density concepts.

Estimating Individual Stand Size–Density Trajectories and a Maximum Size–Density Relationship Species Boundary Line Slope - Curtis L. VanderSchaaf (Forest Science, 2010)
Understanding self-thinning patterns of a species helps resource managers make decisions about proper planting densities and timings of thinnings. It is generally assumed that size–density trajectories of even-aged, monospecific, self-thinning stands consist of three phases: first, a curved approach to a linear portion that represents moderate rates of intraspecific mortality; second, a linear portion where tree density/ha (N) is at its maximum for a particular quadratic mean diameter (Dq), often termed the maximum size–density relationship (MSDR) dynamic thinning line; and third, a divergence from the linear portion. In this article, segmented regression was used to determine what observations are within various phases of self-thinning for a loblolly pine (Pinus taeda L.) planting density trial located in central Mississippi. Those observations estimated to be within the MSDR dynamic thinning line phase of individual plots were combined to estimate a MSDR species boundary line slope (−1.640) using a linear mixed-effects model approach. Based on the N and Dq, where the MSDR dynamic thinning line phase was estimated to begin using segmented regression analyses, and the estimated MSDR species boundary line slope of −1.640, planting density-specific maximum values of Reineke's stand density index were predicted.

Implications of Alternative Field-Sampling Designs on Landsat-Based Mapping of Stand Age and Carbon Stocks in Oregon Forests - Maureen V. Duane; Warren B. Cohen; John L. Campbell; Tara Hudiburg; David P. Turner; Dale L. Weyermann (Forest Science, 2010)
Empirical models relating forest attributes to remotely sensed metrics are widespread in the literature and underpin many of our efforts to map forest structure across complex landscapes. In this study we compared empirical models relating Landsat reflectance to forest age across Oregon using two alternate sets of ground data: one from a large (n ∼ 1500) systematic forest inventory and another from a smaller set of plots (n < 50) deliberately selected to represent pure conditions along predefined structural gradients. Models built with the smaller set of targeted ground data resulted in lower plot-level mapping error (root mean square error) and higher apparent explanatory power (R2) than those built with the larger, more widely distributed inventory data. However, in two of the three ecoregions considered, predictions derived from models built with the smaller ground data set displayed a bias relative to those built with the larger but noisier inventory data. A modeling exercise, wherein mapped forest age was translated into carbon, demonstrated how nonlinear ecological models can magnify these prediction biases over landscapes. From this study, it is clear that for mapping purposes, inventory data are superior to project-specific data sets if those data sets are not representative of the full region over which mapping is to be done.

Implications of Expanding Bioenergy Production from Wood in British Columbia: An Application of a Regional Wood Fiber Allocation Model - Brad K. Stennes; Kurt Niquidet; G. Cornelis van Kooten (Forest Science, 2010)
Energy has been produced from woody biomass in British Columbia for many decades, primarily within the pulp and paper sector, using residual streams from timber processing to create heat and electricity for on-site use. More recently, there has been some stand-alone electricity production and an increase in the capacity to produce wood pellets, both using “waste” from the sawmill sector. Hence, most of the low-cost feedstock sources associated with traditional timber processing are now fully employed. Although previous studies modeled bioenergy production in isolation, we used a fiber allocation and transportation model of the British Columbia forest sector with 24 regions to demonstrate that it is necessary to consider the interaction between use of woody feedstock for pellet production and electricity generation and its traditional uses (e.g., production of pulp, oriented-strandboard, and others). We find that, despite the availability of large areas of standing mountain pine beetle-killed timber, this wood does not enter the energy mix in a dedicated salvage timber harvest to energy system. Further expansion of biofeedstock for energy is met by a combination of woody debris collected at harvesting sites and/or bidding away of fiber from existing users.

Harvest Choice and Timber Supply Models for Forest Forecasting - Maksym Polyakov; David N. Wear; Robert N. Huggett (Forest Science, 2010)
Timber supply has traditionally been modeled using aggregate data, whereas individual harvest choices have been shown to be sensitive to the vintage and condition of forest capital stocks. In this article, we build aggregate supply models for four roundwood products in a seven-state region of the US South directly from stand-level harvest choice models applied to detailed forest inventories. These models allow for a more precise accounting of the biological and economic underpinnings of supply and support forecasting of changes in forest inventories with a high degree of detail. Estimation results support use of the approach. The elasticities of softwood and hardwood sawtimber supply, 0.34 and 0.31, respectively, are consistent with the elasticities reported by previous studies. The elasticities of softwood and hardwood pulpwood supply (respectively, 0.062 and 0.025) are much lower than previous studies found for pulpwood supply, and cross-price elasticities indicate a dominant influence of sawtimber markets on pulpwood supply. Results generally indicate complementarity between sawtimber and pulpwood supply in the short run. This approach can provide a means of predicting the supply consequences of exogenous factors that could alter forest inventories, e.g., climate change and invasive species, and support regular updating of supply models as new inventory data are recorded.

Trivariate Distribution Modeling of Tree Diameter, Height, and Volume - Mingliang Wang; Anoop Upadhyay; Lianjun Zhang (Forest Science, 2010)
Trivariate distribution models were constructed for tree diameter (D), height (H), and volume (V) using a normal copula (a mathematical function that joins or links marginal distribution functions to form multivariate distribution functions). The model parameters were estimated by a two-stage semiparametric method as follows: univariate distribution models were fitted separately for each tree variable, and then the copula dependency (correlation) parameters were independently estimated using empirical distribution functions to approximate the marginal models. Our results indicated that, for the available trivariate data in this study, the log-logistic (a limiting form of the logit-logistic distribution) best described both D and V distributions, whereas the logit-logistic, Johnson's SB, and Weibull marginal models provided roughly the same fitting for the H distribution. The trivariate distribution models produced satisfactory estimates of trivariate frequencies for the three variables, as well as the volume predictions from the resulting median regression models, which were comparable with commonly used volume regression models. The advantage of the normal copula method is that one can use any marginal models suitable for modeling tree diameter, height, and volume distributions separately, rather than being restricted to the SB marginal model in Johnson's SBBB system.

A Hedonic Approach to Value Pinus radiata Log Traits for Appearance-Grade Lumber Production - Rosa M. Alzamora; Luis A. Apiolaza (Forest Science, 2010)
This study used a hedonic approach to estimate the economic value of radiata pine log attributes (small-end diameter, form, and internode length) for appearance-grade lumber, including molding and better, shop, and industrial finger joint. Models were also built at the tree level to investigate the effect of selection as conducted by breeders. A Chilean sawing study provided information on wood traits and log out-turn for 156 logs divided into three classes: pruned butt log, second log, and third log. The conversion return of logs, instead of log prices, was used as the measure of log economic value. The economic values of log small-end diameter were 0.33, 0.19, and 0.10 US$/mm for the first, second, and third log, respectively. Concerning form, those values were US$2.6, US$1.4, and US$0.63 for a marginal improvement of this characteristic. The value of mean internode length was 0.19 US$/cm for second unpruned logs. Values for other internode length indices are also presented in this article. Branch variables were not statistically significant to explain the log recovery value. Finally, log recovery value was found to be elastic to the changes in small-end diameter and form, but inelastic to changes in the mean internode length.

Light Detection and Ranging-Based Measures of Mixed Hardwood Forest Structure - Todd J. Hawbaker; Terje Gobakken; Adrian Lesak; Eric Trømborg; Kirk Contrucci; Volker Radeloff (Forest Science, 2010)
Light detection and ranging (LiDAR) is increasingly used to map terrain and vegetation. Data collection is expensive, but costs are reduced when multiple products are derived from each mission. We examined how well low-density leaf-off LiDAR, originally flown for terrain mapping, quantified hardwood forest structure. We measured tree density, dbh, basal area, mean tree height, Lorey's mean tree height, and sawtimber and pulpwood volume at 114 field plots. Using univariate and multivariate linear regression models, we related field data to LiDAR return heights. We compared models using all LiDAR returns and only first returns. First-return univariate models explained more variability than all-return models; however, the differences were small for multivariate models. Multiple regression models had R2 values of 65% for sawtimber and pulpwood volume, 63% for Lorey's mean tree height, 55% for mean tree height, 48% for mean dbh, 46% for basal area, and 13% for tree density. However, the standard error of the mean for predictions ranged between 1 and 4%, and this level of error is well within levels needed for broad-scale forest assessments. Our results suggest that low-density LiDAR intended for terrain mapping is valuable for broad-scale hardwood forest inventories.

The Bivariate Gompertz Diffusion Model for Tree Diameter and Height Distribution - Petras Rupšys; Edmundas Petrauskas (Forest Science, 2010)
With this research we present a new method for describing the bivariate diameter and height distribution of trees growing in a pure, uneven-aged forest. We use a stochastic differential equation framework to derive a bivariate age-dependent probability density function of tree diameter and height when the tree diameter and height follow a bivariate stochastic Gompertz shape growth process. We also adopt the two-dimensional transition probability function methodology for growth modeling of forest stands. The bivariate stochastic Gompertz model is fit to diameter and height observations for 1,575 pine trees in the Dubrava district of Lithuania. A considerable advantage of the bivariate stochastic Gompertz growth model is that the model parameters are easily interpretable. All results are implemented in the symbolic algebra system MAPLE.

Identifying the Presence of Assessment Errors in Forest Inventory Data by Data Mining - Antti M. Mäkinen; Annika S. Kangas; Timo Tokola (Forest Science, 2010)
All forest inventory methods are susceptible to assessment errors, and although the majority of these errors are relatively minor, some can be exceptionally large. Errors reduce data reliability and increase the probability of nonoptimal decisions in forest planning. We propose that outlier detection techniques based on data mining could be used to detect some of the assessment errors in forestry databases. We tested four outlier detection algorithms presented in previous data mining studies for detecting the errors in compartment-wise field inventory data used in forest planning and examined the relations between the outliers and assessment errors. There was a clear relation between outliers and assessment errors, but this varied somewhat among the algorithms. Compartments with large assessment errors had a higher probability of being classified as outliers. The findings suggest that outlier detection techniques based on data mining could provide a cost-efficient tool for detecting some of the largest assessment errors in inventory data and thus improve the reliability of the whole forest planning process.

Estimation of Forest Stand Parameters from Airborne Laser Scanning Using Calibrated Plot Databases - Virpi Junttila; Tuomo Kauranne; Vesa Leppänen (Forest Science, 2010)
Airborne laser scanning (also known as LiDAR) is rapidly turning into a popular method for operational forest assessment. In the course of this development, classic regression methods have been replaced by nonparametric or Bayesian methods. Accurate estimates with such methods require a large collection of several hundreds of sample plots, which is costly. We propose replacing most of these sample plots by ones collected during earlier missions in different, but similar, forests. However, using such replacement plots requires resolution of two problems. The first one is overcoming differences between different LiDAR scanners, scanning parameters, and scanning conditions, and the second one is avoiding bias due to use of alien plots. We propose a method that resolves both problems and uses only approximately 50 new plots. The method is tested for accuracy in total forest parameters and shown to provide satisfactory estimates for total forest parameters and to be robust against random variation in the selection of the few new plots.

Selection Efficiency for Solid Wood Traits in Pinus taeda using Time-of-Flight Acoustic and Micro-Drill Resistance Methods - Jonathan T. Eckard; Fikret Isik; Bronson Bullock; Bailian Li; Marcia Gumpertz (Forest Science, 2010)
Conventional sampling and laboratory analysis of solid wood properties to facilitate clonal screening in tree improvement programs are prohibitively time-consuming and expensive. Alternative methods—time-of-flight acoustics and micro-drilling resistance—were assessed for efficiency in screening clones for wood stiffness (modulus of elasticity [MOE]), strength (modulus of rupture [MOR]), and density. Ninety clones, consisting of 30 from each of 3 full-sib families, were screened in an 8-year-old loblolly pine (Pinus taeda L.) field test using a TreeSonic time-of-flight tool and Resistograph drill resistance tool. The same clones were sampled for wood specimens for laboratory tests of MOE, MOR, and density. TreeSonic stress wave speed measurements produced highly repeatable clonal phenotypes that facilitated efficient selection for MOE and to a lesser extent for MOR. Resistograph amplitude measurements had a strong genetic correlation with wood density and facilitated highly efficient selection for density, with correlated responses for MOR and MOE. Combining the indirect traits into a selection index improved gain for mechanical wood traits. Both tools provided high measurement rates that resulted in cost efficiencies. Indirect measurements of solid wood properties should be attractive for clonal selection programs that must screen thousands of clones under a finite budget.

Forest Management and Carbon Sequestration in Size-Structured Forests: The Case of Pinus sylvestris in Spain - Renan-Ulrich Goetz; Natali Hritonenko; Ruben Javier Mur; Angels Xabadia; Yuri Yatsenko (Forest Science, 2010)
The Kyoto protocol allows Annex I countries to deduct carbon sequestered by land use, land-use change, and forestry from their national carbon emissions. J. Thornley and M. Cannell (2000. Managing forests for wood yield and carbon storage: A theoretical study. Tree Physiol. 20:477–484) have demonstrated that the objectives of maximizing timber and carbon sequestration are not complementary. Based on this finding, this article presents a model that takes into account the dynamics of timber and carbon in the form of an integro-partial differential and an ordinary differential equation. The integrated biophysical and economic model allows the optimal selective management regime to be determined. The results show that an increase in the carbon price leads to a notable increase in the number of trees. The findings also suggest that carbon sequestration costs are significantly lower for a change in a forest management regime than for a change in land use (afforestation).

A Critique of Silviculture: Managing for Complexity (Forest Science, 2010)

Genetic Contributions to Phenotypic Variation in Physiology, Growth, and Vigor of Western Aspen ( Populus tremuloides ) Clones - Samuel B. St. Clair; Karen E. Mock; Eric M. LaMalfa; Robert B. Campbell; Ronald J. Ryel (Forest Science, 2010)
In aspen and other plant species the effects of environment on phenotype are generally better characterized than genotypic influences. Furthermore, little is known about how genetic influences on tree phenotype change over time. We assessed clonal differences in 417 ramets, representing 18 clones, in a common garden of quaking aspen (Populus tremuloides Michx.) that have developed over 27 years. Genetic contributions to variation in physiology, growth, and vigor were determined over seasonal and multidecadal time scales. The 18 aspen clones exhibited wide-ranging phenotypic variation with two- to threefold differences in physiology and growth traits and more than sevenfold differences in canopy decline and mortality. For growth traits, strong genetic correlations (typically greater than 0.70) and heritability (estimates maintained in a range of 0.25 to 0.36), indicate that genotype had a moderate and consistent influence on growth over the three decades of the study. Physiological traits had much lower genetic correlations and heritability estimates, and they changed significantly within a single growing season. Climatic data suggest that dry conditions in the common garden as the summer progressed may have had a controlling influence on physiological trait responses. Characterizing genetically based phenotypic variation and how it contributes to clone vigor provides a critical link to understanding constraints to aspen viability in its western range.

Conservation Contracts for Forest Biodiversity: Theory and Experience from Finland - Artti Juutinen; Markku Ollikainen (Forest Science, 2010)
We examined the Finnish biodiversity conservation pilot project, called Trading in Natural Values (TNV), using a simulated biodiversity auction model. We found, first, that the share of the most valuable old stands in the key ecological forest habitats was higher in the actual TNV program than in a simulated auction. Second, the actual bids in the TNV program were on average €400–1,200 lower per ha than the bids generated by the auction model. These findings indicate the presence of strong conservation motives among the Finnish landowners. Third, because the number of stands with high biodiversity values is limited in the study area and conservation costs are high for these stands, increasing the size of the conservation budget enrolls more stands in the program but with lower biodiversity values.

Net Benefits of Wildfire Prevention Education Efforts - Jeffrey P. Prestemon; David T. Butry; Karen L. Abt; Ronda Sutphen (Forest Science, 2010)
Wildfire prevention education efforts involve a variety of methods, including airing public service announcements, distributing brochures, and making presentations, which are intended to reduce the occurrence of certain kinds of wildfires. A Poisson model of preventable Florida wildfires from 2002 to 2007 by fire management region was developed. Controlling for potential simultaneity biases, this model indicated that wildfire prevention education efforts have statistically significant and negative effects on the numbers of wildfires ignited by debris burning, campfire escapes, smoking, and children. Evaluating the expected reductions in wildfire damages given a change in wildfire prevention education efforts from current levels showed that marginal benefits exceed marginal costs statewide by an average of 35-fold. The benefits exceeded costs in the fire management regions by 10- to 99-fold, depending on assumptions about how wildfire prevention education spending is allocated to these regions.

Effectiveness of Litter Removal to Prevent Cambial Kill-Caused Mortality in Northern Arizona Ponderosa Pine - James F. Fowler; Carolyn Hull Sieg; Linda L. Wadleigh (Forest Science, 2010)
Removal of deep litter and duff from the base of mature southwestern ponderosa pine (Pinus ponderosa Laws.) is commonly recommended to reduce mortality after prescribed burns, but experimental studies that quantify the effectiveness of such practices in reducing mortality are lacking. After a pilot study on each of four sites in northern Arizona, we monitored 15–16 sets of 8 matched trees on areas designated to be burned and adjacent not-burned sites and randomly assigned one of four litter and duff removal (to mineral soil) treatments: (1) rake to a distance of 23 cm from the bole, (2) leaf blow to a distance of 23 cm, (3) rake to a distance of 1 m, and (4) no litter or duff disturbance or removal. By 3 years postburn, no trees had died because of any of the treatments, but litter and duff removal prevented most cambial kill. However, 17% of the burned, no removal trees had some cambial kill. Litter and duff removal to 23 cm was as effective in preventing cambial kill and bole char as removal to 1 m, and there was no difference between removal by raking versus leaf blower removal. These results suggest that litter and duff removal is not needed to prevent ponderosa pine mortality after fall prescribed burns, but removal to 23 cm is adequate to prevent spots of cambial kill or moderate bark char.

Age–Age Correlations and Early Selection for Height in a Clonal Genetic Test of Norway Spruce - Kani Isik; Jochen Kleinschmit; Wilfried Steiner (Forest Science, 2010)
Heights of rooted cuttings from 40 clones of Norway spruce (Picea abies [L.] Karst) were measured at ages 3, 5, 8, 10, 13, and 17 from rooting at seven test environments in northern Germany. To determine the optimal age for juvenile selection for height, age-related changes in variance components, clone-mean heritability, and age–age correlations were estimated. Partitions of variance components were essentially constant after age 8. Clone-mean heritabilities were highest at age 3 (0.94) and were essentially stable after age 5. Age–age correlations were generally high between similar ages but declined as the difference between pairs of measurement ages increased. Genetic correlations were greater than corresponding phenotypic correlations but were similar in value. Trait–trait correlations between height and diameter (rG = 0.83) and height and volume (rG = 0.90) at age 17 were also high. Simple linear regressions of genetic and phenotypic age–age correlations on LAR (natural log of the ratio of younger age to older age) were significant (R2 ≥ 0.76). Predicted efficiencies of selection suggested that for a rotation age of 60 years, the optimum selection age would be as early as 13 years. Furthermore, gains per year would be increased by about 1½ times if selections were made at about age 15 rather than age 60.

Forestry Practices and Veneer Log Value—Manufacturer's Assessments of Veneer Log Attributes - Delton R. Alderman; David Brinberg; Jan Wiedenbeck (Forest Science, 2010)
Hardwood veneer logs comprise less than 1% of the eastern hardwood forest resource in the United States; yet the typical range for veneer log prices is 2–10 times greater than that of grade 1 sawlogs. In this article we examine attributes and defects known to affect the value of veneer logs and shed light on forest management considerations that affect veneer log production. Veneer attribute data were collected for black cherry (Prunus serotina Ehrh.), black walnut (Juglans nigra L.), northern red oak (Quercus rubra L.), sugar maple (Acer saccharum Marsh.), and white oak (Quercus alba L.). Social judgment theory was used to assess veneer attributes and defects. Color (hue and consistency) and rings (density and texture) are the drivers in veneer log selection, and the results are also indicated by a “Species by Color” interaction and a “Species by Rings” interaction. Other cues are important but do not appear to drive log selection. Hardwood forest management practices, in which partial cuttings are performed, can affect the potential product value of face veneer quality residual stems by changing the rate of diameter growth.

Response of the Photosynthesis and Antioxidant Systems to High-Temperature Stress in Euonymus japonicus Seedlings - Song-Heng Jin; Xue-Qin Li; Bing-Song Zheng; Jun-Gang Wang (Forest Science, 2010)
To uncover the adaptive mechanisms of photosynthesis under high temperatures (HTs), changes in the activity of ribulose-1,5-bisphosphate carboxylase/oxygenase (rubisco), the photosynthetic electron transport system, and antioxidant system were examined in a subtropical forest tree seedling, Euonymus japonicus. Compared with the control, the activity of rubisco and the quantum yield of photosystem (PS) II electron transport (ΦPSII) decreased in HT-treated seedlings, whereas energy-dependent quenching of chlorophyll (Chl) fluorescence (qE) increased. An analysis of the redox change of P700 and the oxygen uptake by PSI indicated that the cyclic electron transport around PSI operated at high rates in E. japonicus seedlings exposed to HT conditions. Furthermore, the levels of reactive oxygen species (ROS), the activities of superoxide dismutase, and the activities of ascorbate peroxidase were increased in HT-treated seedlings. Therefore, it is likely that an enzyme-based water-water cycle was initiated in E. japonicus seedlings in response to HT stress and that the HT-induced ROS might play an important function in HT conditions. Enhancement of cyclic electron transport around PSI and water-water cycles might help maintain a transthylakoid energy potential under HT conditions. This coordinated defense may play an important role in adaptation of E. japonicus cells to HT.

Influence of Crown Biomass Estimators and Distribution on Canopy Fuel Characteristics in Ponderosa Pine Stands of the Black Hills - Tara Keyser; Frederick W. Smith (Forest Science, 2010)
Two determinants of crown fire hazard are canopy bulk density (CBD) and canopy base height (CBH). The Fire and Fuels Extension to the Forest Vegetation Simulator (FFE-FVS) is a model that predicts CBD and CBH. Currently, FFE-FVS accounts for neither geographic variation in tree allometries nor the nonuniform distribution of crown mass when one is estimating CBH and CBD. We develop allometric equations specific to ponderosa pine (Pinus ponderosa Dougl. ex Laws.) in the Black Hills to predict crown mass and use the Weibull distribution to model the vertical distribution of crown mass within individual trees. We present parameter prediction models that, in turn, predict the vertical distribution of crown mass based on stand- and tree-level attributes. With use of an FFE-FVS executable incorporating local crown mass equations and the parameter prediction models, new estimates of CBD and CBH were produced. Locally derived biomass equations predicted substantially greater estimates of foliage mass than currently predicted by FFE-FVS. The increase in CBD resulting from the local biomass and vertical distribution models averaged 78% over original estimates. Our results suggest that locally derived crown mass equations in addition to nonuniform estimates of crown mass distribution be used to calculate CBH and CBD as used in fire prediction models.

Challenges to Estimating Tree Height via LiDAR in Closed-Canopy Forests: A Parable from Western Oregon - Demetrios Gatziolis; Jeremy S. Fried; Vicente S. Monleon (Forest Science, 2010)
We examine the accuracy of tree height estimates obtained via light detection and ranging (LiDAR) in a temperate rainforest characterized by complex terrain, steep slopes, and high canopy cover. The evaluation was based on precise top and base locations for > 1,000 trees in 45 plots distributed across three forest types, a dense network of ground elevation recordings obtained with survey grade equipment, and LiDAR data from high return density acquisitions at leaf-on and leaf-off conditions. Overall, LiDAR error exceeded 10% of tree height for 60% of the trees and 43% of the plots at leaf-on and 55% of the trees and 38% of the plots at leaf-off. Total error was decomposed into contributions from errors in the estimates of tree top height, ground elevation model, and tree lean, and the relationships between those errors and stand- and site-level variables were explored. The magnitude of tree height error was much higher than those documented in other studies. These findings, coupled with observations that indicate suboptimal performance of standard algorithms for data preprocessing, suggest that obtaining accurate estimates of tree height via LiDAR in conditions similar to those in the US Pacific Northwest may require substantial investments in laser analysis techniques research and reevaluation of laser data acquisition specifications.

Variability in Nest Density, Occupancy, and Home Range Size of Western Bluebirds after Forest Treatments - Sarah Hurteau; Thomas Sisk; Brett Dickson; William Block (Forest Science, 2010)
Complex land use and fuels management histories have resulted in significant changes in composition, structure, and function of southwestern forests and subsequent changes in the extent and quality of wildlife habitats. We evaluated how several currently used fuel reduction treatments (e.g., mechanical thinning and prescribed fire alone and in combination) affect nest attributes, nest density, nest tree occupancy, and home range size of Western Bluebirds (Sialia mexicana) in ponderosa pine (Pinus ponderosa)-dominated forests of northern Arizona. Nest attributes, such as number of eggs or nestlings, varied among treatments, but did not differ statistically. Western Bluebird nest density was significantly influenced by treatment, with densities higher in treated areas, even though snag density was lower in treated areas than in control areas. The average (± SE) area of the 50% contour, across all treatment units, was 0.42 ± 0.07 ha, and the average area of the 90% contour was 2.36 ± 0.30 ha. Home range sizes for both probability contours evaluated were 1.5 times larger in the thin-only treatments than in the control units. Conversely, home range area in thin-and-burn treatments was approximately 30% smaller than in control units. The largest home ranges occurred in the burn-only treatments. Our results suggest that forest treatments, such as thinning and prescribed fire are, in general, beneficial to Western Bluebirds, but that low snag retention may be problematic in areas receiving prescribed fire as part of their treatment action.

Thinning and Burning in Dry Coniferous Forests of the Western United States: Effectiveness in Altering Diameter Distributions - Andrew Youngblood (Forest Science, 2010)
Western United States land managers are conducting fuel reduction and forest restoration treatments in forests with altered structural conditions. As part of the National Fire and Fire Surrogate (FFS) study, thinning and burning treatments were evaluated for changing forest structure. Shifts between pretreatment and posttreatment diameter distributions at seven western FFS study sites were determined by assessing live tree diameter frequency distributions and the 10th and 90th percentile and mean diameter. Diameter distributions were based on 31,517 live trees within 76 pretreatment units and 25,061 live trees within 85 posttreatment units. Cross-site comparisons were made using meta-analysis. Values for 10th percentile diameter increased at two sites, values for 90th percentile diameter increased at six sites, and values for mean diameter increased at five sites (P < 0.05) after active treatments (thin, burn, or thin + burn) compared with control sites. Across the seven western FFS study sites, the overall effect size of the thin treatment increased for 90th percentile and mean diameter, the overall effect size of the burn treatment increased for 10th percentile, 90th percentile, and mean diameter, and the overall effect size of the thin + burn treatment increased for 10th percentile, 90th percentile, and mean diameter. This work indicates that although each of the active treatments was effective in shifting diameter distributions toward larger trees, no single treatment or entry will probably mitigate nearly a century of fire exclusion and fuel accumulation in dry coniferous forests of the western United States.

Restoration Treatment Effects on Stand Structure, Tree Growth, and Fire Hazard in a Ponderosa Pine/Douglas-Fir Forest in Montana - Carl E. Fiedler; Kerry L. Metlen; Erich K. Dodson (Forest Science, 2010)
Crown fires that burned thousands of ha of ponderosa pine (Pinus ponderosa Dougl. ex Laws.) forests in recent years attest to the hazardous conditions extant on the western landscape. Managers have responded with broad-scale implementation of fuel reduction treatments; however. because threats to pine forests extend beyond fire, so too must the approaches to address them. This western Montana study evaluated four treatments in a randomized complete block experiment for their effects on stand structural characteristics, growth increment, and crown fire potential. Evaluation of control, burn-only, thin-only, and thin-burn treatments showed that the combined thin-burn treatment had the greatest number of desired effects, the burn-only had the fewest, and the thin-only was intermediate. The thin-burn significantly reduced stand density, canopy cover, torching hazard, and crowning hazard and increased average diameter, height-to live-crown, and basal area increment; the thin-only reduced stand density, canopy cover, and crowning hazard and increased average diameter and basal area increment; and the burn-only reduced torching hazard and increased height-to-live crown. These structural and growth effects are related to or influence numerous stand/ecosystem properties at our site, including diameter distributions, species composition, large-tree development potential, overall tree vigor, potential for shade-intolerant tree regeneration, and resiliency to fire. Results demonstrate that well-designed restoration treatments can promote key short-term stand and ecosystem responses while significantly reducing crown fire potential.

Ecological Consequences of Alternative Fuel Reduction Treatments in Seasonally Dry Forests: The National Fire and Fire Surrogate Study - James D. McIver; Christopher J. Fettig (Forest Science, 2010)

Editor's Note - Edwin J. Green (Forest Science, 2010)

Short-Term Effects of Fuel Reduction Treatments on Herpetofauna from the Southeastern United States - Eran S. Kilpatrick; Thomas A. Waldrop; Joseph D. Lanham; Cathryn H. Greenberg; Tom H. Contreras (Forest Science, 2010)
Path analysis of fuel reduction treatments on herpetofauna across four southeastern sites of the National Fire and Fire Surrogate Study provided quantitative evidence relating changes in vegetation and fuels to herpetofauna response. Fuel reduction treatments included prescribed burning (B), a mechanical treatment (M), mechanical treatment followed by prescribed burning (MB), and an untreated control (C). Treatment effects on herpetofauna response variables were predicted by the direct and indirect effects of stand basal area, coarse woody debris volume, native herb cover, and forest floor depth. Path models were solved for lizard, snake, and reptile response to fuel reduction treatments. Lizard and reptile abundance were higher in B and MB plots than in C and M plots. Increasing native herb cover best predicted lizard and reptile abundance within B and MB plots. Native herb cover, lizard, and reptile abundance were highest in B and MB plots, and each of these response variables responded positively to B and MB.

Microhabitat Selection of Bark-Foraging Birds in Response to Fire and Fire Surrogate Treatments - Kerry L. Farris; Steve Zack; Andrew J. Amacher; Jennifer C. Pierson (Forest Science, 2010)
We examined the short-term response of the bark-foraging bird community to mechanical thinning, prescribed fire, and thinning/prescribed fire combination treatments designed to reduce fuel loads at study sites throughout the continental United States as part of the national Fire and Fire Surrogate (FFS) project. We modeled the effects of study site, treatment, treatment category, and time since treatment on the foraging encounter rate of four individual species (red-breasted nuthatch [Sitta canadensis], mountain chickadee [Poecile gambeli], hairy woodpecker [Picoides villosus], and brown creeper [Certhia americana]) and assessed the relative importance of several tree and snag characteristics in the selection of foraging trees by these same species. The foraging encounter rate of all four species responded inconsistently across both treatment categories and study sites. Substrate diameter was the strongest and most consistent characteristic positively influencing the selection of foraging habitat structures for all species across all treatment categories. Other influential variables included the presence of bark beetles for red-breasted nuthatches, hairy woodpeckers, and brown creepers in control and burn-only treatment areas and tree species for brown creepers in burn-only and thin-only treatment areas. Although this study did not detect any major negative treatment response by any species, our results suggest that there is substantial variability in the reaction of this particular bird community to fuel reduction treatments and that managers may need to evaluate the effects of these treatments on a site-by-site and species-by-species basis.

Short-Term Response of Ground-Dwelling Arthropods to Prescribed Fire and Mechanical Fuel Reduction in a Southern Appalachian Upland Hardwood Forest - Cathryn H. Greenberg; T. G. Forrest; Thomas Waldrop (Forest Science, 2010)
As part of the multidisciplinary National Fire and Fire Surrogate Study, we used drift fences with pitfall traps to determine how three fuel reduction treatments affected ground-dwelling macroarthropods in the southern Appalachian Mountains of North Carolina. Four experimental units, each >14 ha, were contained within each of three replicate blocks. Treatments were (1) prescribed burning, (2) mechanical felling of shrubs and small trees, (3) mechanical felling + burning, and (4) untreated controls. Mechanical understory felling was conducted in winter 2001–2002, and prescribed burning was conducted in March 2003. Mechanical felling + burning resulted in greater canopy openness compared with the other treatments as a result of hotter fires and elevated levels of subsequent tree mortality. Burning reduced leaf litter depth in both burned treatments by >80%. We captured 6,776 individual macroarthropods (460 g of dry biomass) within 22 identified orders and 59 identified families. Coleoptera and Hymenoptera were numerically dominant (27.3 and 25.9%, respectively); Lepidoptera larvae also were a dominant component of dry biomass (37%). We found no differences among treatments in the relative abundance or dry biomass of total ground-dwelling macroarthropods or within most orders; Hymenoptera (predominantly Formicidae) dry biomass was greater with mechanical felling + burning than with mechanical felling. Total relative abundance and dry biomass were low in spring and higher in late summer. Our results indicate that prescribed burning and mechanical fuel reduction treatments conducted in winter or early spring have little impact on the community composition, relative abundance, or biomass of total arthropods or most arthropod orders and families, at least in the short term. However, because we did not use a killing agent, our trapping method probably undersampled macroarthropods that could climb or fly from traps, and results for those groups should be interpreted cautiously. Our study suggests that the fuel reduction methods studied may be used as a land management tool in upland hardwood forest with little effect on macroarthropod communities or the ground-dwelling arthropod prey base for vertebrates.

Short-Term Effects of Thinning and Burning Restoration Treatments on Avian Community Composition, Density, and Nest Survival in the Eastern Cascades Dry Forests, Washington - William Gaines; Maryellen Haggard; James Begley; John Lehmkuhl; Andrea Lyons (Forest Science, 2010)
We monitored the short-term (<3 years) response of land birds to restoration treatments (thin, burn, and thin-burn) in dry forests located on the eastern slope of the Cascade Range in Washington. Overall avian community composition did not change among the treatments. However, individual species responses varied with the chipping sparrow showing lower density in treatments, whereas hermit thrush, mountain chickadee, white-headed woodpecker, western bluebird, American crow, and common raven increased in treatment units. Daily survival rates of nesting guilds were similar in treated versus control stands; however, burn-only showed lower daily survival rates compared with other treatments. Additional research is needed to validate this result. Cavity-nesters (mountain chickadee, red-breasted nuthatch, and house wren) and foliage-nesters (chipping sparrow) used trees that were larger in diameter than available regardless of the treatment. Our results, in combination with other results from this study area, provide important implications for managers: (1) thin-burn treatments were effective at restoring habitat for several avian focal species; (2) spring burn treatments should be carefully designed to achieve desired restoration objectives; (3) large trees provide important habitat functions and are a key component for maintaining or restoring the viability of focal avian species; and (4) additional research is needed to better understand the effects of spring burning and the long-term effects of dry forest restoration treatments.

Thinning and Prescribed Fire Effects on Snag Abundance and Spatial Pattern in an Eastern Cascade Range Dry Forest, Washington, USA - Paul F. Hessburg; Nicholas A. Povak; R. Brion Salter (Forest Science, 2010)
Mechanical thinning and prescribed burning practices are commonly used to address tree stocking, spacing, composition, and canopy and surface fuel conditions in western US mixed conifer forests. We examined the effects of these fuel treatments alone and combined on snag abundance and spatial pattern across 12 10-ha treatment units in central Washington State. A snag census was conducted before and immediately after treatments on each unit where all snags were measured and classified as either “new” (<1 year as a snag) or “old” (>1 year as a snag) mortality, and bark beetle species were censused on the bottom 3-m of the bole. Before treatment, snags were found in all units and more than two-thirds of the snags were ponderosa pine. Burning (burn-only and thin + burn combined) treatments led to increases in total snag abundance in all but the largest diameter class. Snag abundance in the large snag class (>60 cm dbh) decreased in most treatment units indicating that units with high abundance before treatment had the potential to lose more snags with treatment or time. Treatments also affected the spatial distribution of snags. The thin-only treatment reduced clumpiness, leading to a more random snag distribution, whereas the burn-only and thin + burn treatments generally retained or enhanced a clumped snag distribution. Bark beetles attacked >75% of snags across all units before and after treatments, and red turpentine beetle (Dendroctonus valens LeConte) occurrence tended to increase after prescribed burning. Managers can use this information to tune silvicultural prescriptions to meet stocking, spacing, and fuel reduction objectives while retaining or recruiting snags, thereby increasing the utility of conditions for certain wildlife species.

Effects of Fire and Fire Surrogate Treatments on Bark Beetle-Caused Tree Mortality in the Southern Cascades, California - Christopher Fettig; Robert Borys; Christopher Dabney (Forest Science, 2010)
We examined bark beetle responses to fire and fire surrogate treatments 2 and 4 years after the application of prescribed fire in a mixed-conifer forest in northern California. Treatments included an untreated control (C), thinning from below (T), and applications of prescribed fire (B) and T + B replicated three times in 10-ha experimental units. A total of 1,822 pine and fir trees (5.1% of all trees) were killed by bark beetles. Mountain pine beetle (Dendroctonus ponderosae Hopkins) was found infesting ponderosa pine (Pinus ponderosa Dougl. ex Laws.), sugar pine (Pinus lambertiana Dougl.), and lodgepole pine (Pinus contorta Dougl. ex Loud.); western pine beetle (Dendroctonus brevicomis LeConte) was found infesting ponderosa pine; and fir engraver (Scolytus ventralis LeConte) was found infesting white fir (Abies concolor [Gord. & Glend.] Lindl. ex Hildebr.). Significantly higher rates of bark beetle-caused tree mortality occurred on B (9.2%) than on C (3.2%), T (<1%), or T + B (3.3%) cumulatively during the 4-year period. A total of 723 pines (4.4% of all pines) were killed by bark beetles, primarily mountain pine beetle. Attacks resulted in significantly more pine mortality on B (5%) than on C, T, or T + B (all <1%) 2 years after the application of prescribed fire. No significant treatment effects were found during the second sample period or cumulatively during the 4-year period. A total of 1,098 white fir trees (5.8% of all white fir) were killed by the fir engraver. Attacks resulted in significantly higher rates of fir mortality on T + B than on T during both sample periods but not cumulatively during the 4-year period. Overall, bark beetle-caused tree mortality was concentrated in the smaller diameter classes. The implications of these and other results to forest management are discussed.

Fuels and Predicted Fire Behavior in the Southern Appalachian Mountains After Fire and Fire Surrogate Treatments - Thomas Waldrop; Ross A. Phillips; Dean A. Simon (Forest Science, 2010)
This study tested the success of fuel reduction treatments for mitigating wildfire behavior in an area that has had little previous research on fire, the southern Appalachian Mountains. A secondary objective of treatments was to restore the community to an open woodland condition. Three blocks of four treatments were installed in a mature hardwood forest in western North Carolina. Fuel reduction treatments included chainsaw felling of small trees and shrubs (mechanical treatment), two prescribed fires 3 years apart, a combination of mechanical and burning treatments, and an untreated control. Mechanical treatment eliminated vertical fuels but without prescribed burning; the mechanical treatment added litter (11%) and woody fuels (1 hour 167%; 10 hours 78%) that increased several measures of BehavePlus4-simulated fire behavior (rate of spread, flame length, spread distance, and area burned) for 5 years. Prescribed burning reduced litter mass by 80% and reduced all simulated fire behavior variables for 1 year but had no residual effect by the third year. The combined mechanical and burning treatments had hot prescribed fires (mean temperature of 517°C at 30 cm aboveground) during the first burn that killed some overstory trees, resulting in increased amounts of woody fuels on the forest floor. All active treatments (fire, mechanical, and combined) reduced simulated wildfire behavior, even after a severe ice storm that added fine fuels. Prescribed burning in combination with the mechanical treatment was the most effective in reducing all measures of fire behavior and advancing restoration objectives. Each of the active treatments tested must be repeated to reduce fuels and lower wildfire behavior, but prescribed burning must be repeated frequently.

On Conducting a Multisite, Multidisciplinary Forestry Research Project: Lessons from the National Fire and Fire Surrogate Study - James Duncan McIver; Charles Phillip Weatherspoon (Forest Science, 2010)
The National Fire and Fire Surrogate (FFS) study is described, from its conceptual stage in early 1996 to the completion of its short-term phase in May 2006. Comprising 12 sites, the FFS study is a comprehensive multidisciplinary experiment designed to evaluate the economics and ecological consequences of alternative fuel reduction treatments in seasonally dry forests of the United States. The FFS study uses a common experimental design across the 12-site network, with each site consisting of a fully replicated experiment that compares four treatments: an unmanipulated control, prescribed fire, mechanical treatments, and mechanical + fire. We measured operational costs and variables within several components of the ecosystem, including vegetation, the fuel bed, soils, bark beetles, tree diseases, and wildlife in the same 10-ha experimental units. This design allowed us to assemble a fairly complete picture of ecosystem response to treatment at the site scale, and to compare treatment response across sites representing a wide variety of conditions. We offer the FFS study as a model for conducting a complex multidisciplinary management experiment focused on natural resource issues. We then discuss why we believe it was successful and how it could be improved. We discuss seven key features that we believe must be considered to conduct a successful multidisciplinary experiment: funding, design, partnerships, organization, standardization, data management, and outreach. Although experiments such as the FFS study are difficult to execute, they may be our best hope for answering some of our more pressing questions in the field of natural resource management.

Long-Term Changes in Forest Productivity: A Consistent Assessment in Even-Aged Stands - Jean-Daniel Bontemps; Jean-Christophe Hervé; Jean-François Dhôte (Forest Science, 2009)
The objective of the study was to provide a stand-scale assessment of long-term productivity changes in even-aged stands and to depict their chronology over the 20th century. We focused on dominant height growth as a proxy for productivity, reconstructed from stem analyses in temporary plots. Height increments from two generations of stands were compared. Stands were associated in pairs to ensure accurate control of intrinsic site fertility conditions. The historical evolution of the growth rate was estimated using a statistical modeling approach based on a mixed-effects model, with a control of both site and developmental stage effects. We placed emphasis on a model formulation that leads to a meaningful interpretation of growth rate evolution. We applied the methodology to a sample of 14 stand pairs and 84 stem analyses of common beech in northeastern France. An accelerated increase in growth rate was identified, reaching +50% over the 20th century. The trend also displayed short-term growth anomalies.

Profit Efficiency in Timber Supply: Marginalization and Other Relevant Influences - Sjur Baardsen; Gudbrand Lien; Ståle Størdal (Forest Science, 2009)
The objective of this article was to explore how marginalization of revenues from timber sales relative to income from agriculture and employment affects profit efficiency (the ratio of actual profit to maximum obtainable profit). We also sought to identify and measure the effects of other relevant inefficiency factors. A translog profit frontier function with an inefficiency module was estimated using a panel of 2,265 observations of 385 active Norwegian forest owners for 1991–2004. We found that profit efficiency decreases as the revenues from timber sales fall relative to agricultural or wage income. Other factors decreasing the efficiency were logging distance (beyond what can be explained by logging costs), fragmentation of the forest property, and time. Factors increasing profit efficiency were experience (age), information (possession of a management plan), and geographical location (centrality). On the basis of our results we make recommendations on how forest owners can improve their profit efficiency. We also suggest further developing and streamlining contract regimens as policy instruments for promoting efficiency.

Effects of Timber Prices, Ownership Objectives, and Owner Characteristics on Timber Supply - Ibrahim M. Favada; Heimo Karppinen; Jari Kuuluvainen; Jarmo Mikkola; Corinne Stavness (Forest Science, 2009)
In this article, we examine factors affecting nonindustrial private timber supply using a consistent estimation method for a limited dependent variable model. The survey data, collected in 1999 from 3,051 Finnish forest owners, includes information on objectives for ownership as well as annual harvest volumes between 1994 and 1998. Ownership objectives are identified using principal component analysis, and five forest ownership objective groups are generated using K-means clustering: multiobjective owners, investors, self-employed owners, recreationists, and indifferent owners. Along with stumpage price, reforestation costs and forest and owner characteristics, including the above objective groups, are used as explanatory variables in estimating the supply equation. A consistent estimation method allowing for heteroscedasticity and non-normality is used. Statistically significant elasticity of the unconditional mean harvest with respect to timber price is 1.3. Recreationists and indifferent forest owners, ceteris paribus, harvest about 2 m3/ha/year less than multiobjective owners and self-employed owners, whereas investors and indifferent owners are more price-responsive than the other groups.

Effect of the Inclusion of Mushroom Values on the Optimal Management of Even-Aged Pine Stands of Catalonia - Marc Palahí; Timo Pukkala; José Antonio Bonet; Carlos Colinas; Christine R. Fischer; Juan R. Martínez de Aragón (Forest Science, 2009)
Mushrooms are an important product of the pine stands of the Central Pyrenees of Catalonia. In places where the microclimate is reasonably moist, the value of mushrooms may be clearly higher than the value of timber production. This study examines the optimal economic management for both timber and mushrooms in even-aged Scots pine and Black pine stands in Catalonia. Empirical mushroom yield models were integrated in a stand growth simulator, which was linked with an optimization algorithm to find the optimal management schedule for Pinus sylvestris and Pinus nigra stands on different sites and with different mushroom prices. The results showed that on sites where the potential mushroom yield is high, mushrooms should be taken into account in stand management. Thinning treatments, which usually are unprofitable, were included in the optimal management schedule when mushroom production was included in the analysis. Although thinnings have a negative short-term effect on mushroom yields, their long-term effect is often positive because they reduce stand density to a level that is favorable for mushrooms. At elevations that are suitable for P. sylvestris (900–1,500 m above sea level), the soil expectation value (SEV) of mushroom yields was commonly 4–10 times higher than the SEV of timber production. At somewhat lower elevations, where P. nigra dominates, the effect of mushrooms on the optimal stand management was smaller because mushroom yields are typically lower in P. nigra stands.

Fertilization and Seeding Effects on Vegetative Cover After Wildfire in North-Central Washington State - David W. Peterson; Erich K. Dodson; Richy J. Harrod (Forest Science, 2009)
Land surface treatments are often applied after severe wildfires to mitigate runoff and erosion threats. However, questions remain about treatment effectiveness, even as treatment costs continue to rise. We experimentally evaluated the effects of seeding and fertilization treatments on vegetative and total soil cover for two growing seasons after the Pot Peak wildfire in the eastern Cascade Mountains. Without treatments, vegetative cover averaged 15% the first year and 27% the second year after wildfire. Fertilization significantly increased vascular plant cover and reduced bare soil area in both years, but differences between low and high fertilization levels were not significant. Fertilization also increased cryptogam cover. Seeding alone was generally ineffective; however, the combination of fertilization with a seed mixture containing the native forb, yarrow (Achillea millefolium L.), produced the highest vascular plant cover and lowest bare soil area. Our results suggest that fertilization may be more effective than seeding, probably providing a degree of protection from erosion, especially the second year after fire. However, treatment effectiveness must be evaluated in context against costs and potential ecosystem impacts.

An Evaluation of Spatial Autocorrelation and Heterogeneity in the Residuals of Six Regression Models - Lianjun Zhang; Zhihai Ma; Luo Guo (Forest Science, 2009)
Spatial effects include spatial autocorrelation and heterogeneity. Ignoring spatial effects in a modeling process causes misleading significance tests and suboptimal model prediction. In this study, we used three forest plots with different spatial patterns of tree locations (i.e., clustered, random, and regular patterns) to investigate the spatial distributions and heterogeneity in the model residuals from six regression models with the ordinary least squares (OLS) as the benchmark. Our results revealed that when significant spatial autocorrelations and variations existed in the relationship between tree height and diameter, as in the softwood plot (clustered) and hardwood plot (random), OLS was not appropriate for modeling the relationship between tree variables. Spatial regression models (i.e., spatial lag and spatial error models) were effective for accounting for spatial autocorrelation in the model residuals, but they were insufficient to deal with the problem of spatial heterogeneity. It was evident that the model residuals in both spatial lag and spatial error models had a similar pattern and magnitudes of spatial heterogeneity at spatial scales different from those of the OLS model. In contrast, the linear mixed model and geographically weighted regression incorporated the spatial dependence and variation into modeling processes, and consequently, fitted the data better and predicted the response variable more accurately. The model residuals from both the linear mixed model and geographically weighted regression had desirable spatial distributions, meaning fewer clusters of similar or dissimilar model residuals over space.

A Multivariate Linear Mixed-Effects Model for the Generalization of Sample Tree Heights and Crown Ratios in the Finnish National Forest Inventory - Kalle Eerikäinen (Forest Science, 2009)
The aim of this article was to develop a prediction model that could use the geographically representative but locally sparse sample tree data of the Finnish National Forest Inventory (FNFI) efficiently and account for the correlation structures in these data when generalizing sample tree characteristics over tally trees by species. The sample tree characteristics modeled were tree height and the ratio of live crown length to tree height. These are needed for all FNFI tally trees to obtain their stem volumes and biomasses. As a result, a multivariate linear mixed-effects model with species-specific parameters designed for the multiresponse FNFI data was developed. The fixed parts of the two linear models of the simultaneous system consist of both tree and stand-level independent variables such as dbh, mensurable stand characteristics, and site quality indicators. Because of the hierarchically correlated data, the intercepts and the slopes (i.e., the coefficients associated with tree characteristics) in the two models were assumed to vary randomly over clusters and forest stands within them. The random coefficients were also associated with components for random species effects. The selected formulation of the random parts of the models makes it possible to obtain localized species-specific curves for clusters and forest stands even with one measured sample tree. The results show that the multivariate mixed-effects model with species-specific components is a stable, efficient predictor and well applicable to locally sparse but geographically representative data of the FNFI type.

Investments in Timberland and Softwood Timber as Parts of Portfolio Selection in the United States: A Cointegration Analysis and Capital Asset Pricing Model - Xianchun Liao; Yaoqi Zhang; Changyou Sun (Forest Science, 2009)
In this article we investigated the financial performance of investments in timberland and timber and their correlations with nonforestry financial assets in the United States. Cointegration analysis and the capital asset pricing model were used to examine the long-run and short-run correlations with quarterly data from January 1992 to June 2006. The results of the cointegration analysis revealed that investment return on timberland tended to increase by 1.3% as Southern softwood stumpage price increased by 1%, indicating that a shift from pulpwood to sawtimber production might increase timber price and thus benefit timberland investment. The results also indicated that there were positive correlations between farmland return and Southern softwood stumpage price and between the stock market and timberland, indicating that treatments such as high-intensity site preparation might increase land quality and, hence, enlarge timber size and increase timber price. However, investors need to be cautious with the stock market because any change in the stock market has a potential effect on the timberland market. The results of the capital asset pricing model showed that timberland generated significant excess returns over the study period, but softwood timber did not. Timberland or softwood did not reduce systematic risk in a portfolio with stocks in the short run. In the short run, abnormal returns on timberland did occur, and timberland would be a desirable investment vehicle mixed with real estate.

Testing for Change in Structural Elements of Forest Inventories - Melinda Vokoun; David Wear; Robert Abt (Forest Science, 2009)
In this article we develop a methodology to test for changes in the underlying relationships between measures of forest productivity (structural elements) and site characteristics, herein referred to as structural changes, using standard forest inventories. Changes in measures of forest growing stock volume and number of trees for both hardwood and softwood on forestland in North Carolina are evaluated using plot-level data aggregated at both the state and survey unit level from the last three available completed Forest Inventory and Analysis surveys using exploratory data analysis and nonparametric statistics. When the survey data are aggregated at the state level, we accept the null hypothesis of no discernible between-survey differences in the means of the forest productivity measures for at least 90% of the plots in each of the four models. We also accept the null hypothesis of no discernible between-survey differences in the variance or higher moments of these forest productivity measures for at least 82% of comparisons. At a finer scale, our results show that structural stability is questionable in the Coastal Plain units of North Carolina. Overall, results provide evidence of some structural change in the forests of North Carolina but do not address the causes of such changes. The systematic comparison of forest inventories conducted in this article constitutes a new approach to testing for structural changes in forest relationships, one that can be implemented as a monitoring protocol within standard repeated forest inventories.

The Interaction among Provenances of Melaleuca leucadendra (Weeping Paperbark), Salt, and Aluminum - Nguyen T. Nguyen; Hirofumi Saneoka; Ryuichi Suwa; Kounosuke Fujita (Forest Science, 2009)
The expansion in salt-affected acid sulfate soil areas induced by the rise in sea level calls for studies on plant tolerance to combined aluminum (Al) and salt (NaCl) stress. We investigated the difference in tolerance to Al and NaCl alone and in combination among 16 Melaleuca leucadendra (L.) L. provenances. Two-month-old seedlings were grown with or without 10 mM Al and/or 50 mM NaCl at pH 3.8 for 3 months. Plant growth was reduced most by combined Al and NaCl stress and then by NaCl and least by Al, and provenance variation in stress tolerance increased with an increase in the level of the stress effect. Al and NaCl enhanced each other's effects in nine provenances, but they alleviated each other's effects in two provenances. There were significant differences in plant growth among provenances in every treatment; however, positive relationships were found among Al tolerance, NaCl tolerance, and combination tolerance. Combined Al and NaCl stress greatly increased Na concentration, whereas it decreased K concentration in leaf sap. Tolerance to combination stress tended to have negative relationships with both stress-induced reduction in leaf osmotic potential and leaf K concentration among provenances, suggesting that provenance variability in tolerance to combined Al and NaCl stress is partly due to differences in the ability to limit ionic stress through an adjustment in K uptake.

Estimating Forest Attributes Using Observations of Canopy Height: A Model-Based Approach - Lauri Mehtätalo; Jukka Nyblom (Forest Science, 2009)
An airborne laser scanner can be used to make observations of canopy height at given locations within a forest stand. In recent years, foresters have developed methods to extract information on forest attributes, such as stand density and size distribution of the trees, from laser data for forest inventory purposes. These methods are based on empirical relationships rather than on theory about how observations are generated by tree canopies. We recover the relationship between canopy height and forest attributes, based on assumptions about the shape of a single tree crown, the distribution of tree height, and the spatial distribution of tree locations. This work improves our understanding of how stand characteristics are related to observations collected by airborne laser scanners and links the problem to the theory of germ-grain models and random closet sets in spatial statistics. Furthermore, we use the derived relationship to develop a model-based approach for estimating stand density and distribution of tree heights using observations of canopy height. A simulation study showed that the method is capable of producing fairly accurate estimates for the number of stems and mean tree height, yielding only slight biases in mean tree height and stand density.

Long-Term Effects of Site Preparation Treatments, Complete Competition Control, and Repeated Fertilization on Growth of Slash Pine Plantations in the Flatwoods of the Southeastern United States - Dehai Zhao; Michael Kane; Bruce Borders; Mike Harrison (Forest Science, 2009)
Data through age 26 from a well-designed study established in 1979 were analyzed with a repeated-measures analysis of variance approach to evaluate effects of site preparation treatments, complete competition control, and repeated fertilization on growth of slash pine (Pinus elliottii Engelm.) plantations on Spodosols and non-Spodosols in the flatwoods region of southern Georgia and northern Florida. Complete and sustained vegetation control and repeated fertilization consistently and significantly increased slash pine productivity, with greater responses occurring on Spodosols than on non-Spodosols; their combination had less than additive effects on Spodosols and additive effects on non-Spodosols. Complete and sustained vegetation control resulted in greater cumulative responses than repeated fertilization over more than 20 years, and then the gains from repeated fertilization had caught or surpassed the gains from complete vegetation control. Bedding resulted in significant responses in the early ages. Burning improved stand basal area and volume growth rather than average tree height and dbh on non-Spodosols and had little effect on Spodosols. Chopping had no significant effect on either soil group. Results of this study emphasize the need for site-specific silvicultural prescriptions.

Fifty Years of Fertilization Experiments on Pinus pinaster in Southwest France: The Importance of Phosphorus as a Fertilizer - Pierre Trichet; Mark R. Bakker; Laurent Augusto; Pierre Alazard; Dominique Merzeau; Etienne Saur (Forest Science, 2009)
Data from 50 years of fertilization trials on Maritime pine (Pinus pinaster) were compiled to investigate how growth was affected by fertilization or improved nutrient availability. The results demonstrated that only trees fertilized with phosphorus (P) fertilizers showed an overall improvement in productivity. The effects were significant mainly at wetter sites and were less effective at drier sites. The form of P fertilizer does not seem to be important, and a rate of about 17–35 kg of P ha−1 applied as a single dose at stand establishment was found to be sufficient to obtain a significant improvement in growth. Foresters can expect an increase of 20–40% cumulative volume at rotation age or a reduction of 4–5 years in rotation length due to fertilization with P. The duration of the effect of P fertilization on the annual increment varied (up to 20 years after application in the best cases). The high P-fixing capacity of these soils appears to be the most important factor in explaining differential responsiveness to P fertilizers, but stand developmental stage or the appearance of other limitations such as nitrogen may also explain the decline in the effectiveness of P fertilization with age.

Cavity Size and Copper Root Pruning Affect Production and Establishment of Container-Grown Longleaf Pine Seedlings - Mary Anne Sword Sayer; James D. Haywood; Shi-Jean Susana Sung (Forest Science, 2009)
With six container types, we tested the effects of cavity size (i.e., 60, 93, and 170 ml) and copper root pruning on the root system development of longleaf pine (Pinus palustris Mill.) seedlings grown in a greenhouse. We then evaluated root egress during a root growth potential test and assessed seedling morphology and root system development 1 year after planting in central Louisiana, USA. Seedling size was increased by copper root pruning in small cavities but was unaffected by this treatment in larger cavities. Before planting, copper root pruning increased taproot and secondary lateral root dry weights at the expense of primary lateral root dry weight and increased root growth potential in the top 5 cm of the root plug. Across treatments, survival was 97%, and all seedlings were in the grass stage. Of the lateral root dry weight that elongated during the first year after planting, 33% more occurred in the upper 5 cm of soil when seedlings were treated with copper. Within each cavity size, copper root pruning did not affect the general morphology of 1-year-old seedlings. However, relationships between root collar diameter and root egress by depth indicated that this treatment has the potential to increase the range of cavity sizes used for seedling production.

Motivations and Land-Use Intentions of Nonindustrial Private Forest Landowners: Comparing Inheritors to Noninheritors - Indrajit Majumdar; David Laband; Lawrence Teeter; Brett Butler (Forest Science, 2009)
The documented importance of intergenerational human capital transfers in agriculture generally gives us reason to suspect that such transfers may be important in a forestry context and that there may be important implied differences between first-generation woodland owners and multigeneration woodland owners with respect to their motivations and future intentions. In turn, knowledge of the motivations and intentions of nonindustrial private landowners may be extremely important because such knowledge may be vital in terms of our ability to predict future timber supply and the availability of nontimber amenities. Also, the effectiveness of public policies targeting nonindustrial private forest landowners may depend critically on their motivations and intentions. In this article, we analyzed 8,373 responses to the National Woodland Owner Survey to compare characteristics, motivations, and intentions of multigeneration forest landowners against those of single-generation forest landowners. In brief, we found there were significant differences in their motivations and management behavior; inheritors are more active forest managers and manage for both timber and nontimber forest products more aggressively than noninheritors who typically value esthetics, privacy, protection of biodiversity, and nonhunting recreation.

Note on the Variance of Radial Sampling Strategies with Random Versus Purposively Located Pivot Points - Tomas B. Lynch (Forest Science, 2009)
Several radial sampling strategies have recently been proposed, including sector sampling, radial line sampling for estimation of area of coverage, and radial line sampling for planar area estimation. These strategies are based on either sector or line samples that emanate from a common interior point (pivot point) within the land area to be sampled. It has usually been assumed that the pivot point will be purposively located so that its location will not be random. However, random location of the pivot point within the sampling area is conceptually possible, so that it is of interest to compare the variance of estimators with purposively located pivot points with those with randomly located pivot points. When this is done, it can be determined that the variance of the estimator with a randomly located pivot point is the expected value of the conditional (on pivot point location) variance of the estimator with respect to the distribution of possible pivot point locations. Thus, for instance, if each point in the area to be sampled is equally likely to be chosen, then the variance under a random pivot point location is the mean or expected value of the conditional variance with respect to every possible pivot point location within the sample area.

Terrain Trafficability Prediction with GIS Analysis - Antti Suvinen; Timo Tokola; Martti Saarilahti (Forest Science, 2009)
The aim of this article is to test a GIS-based model for predicting terrain trafficability. The resistance forces restricting the movement of a forest tractor are estimated using a digital soil map, a 25 × 25-m digital elevation model (DEM) and an improved elevation model. Virtual total resistances along the 1,150-m test track were measured using the controller area network (CAN) bus-based technique. Rolling resistance prediction based on the soil type map was quite successful on frictional soils, but the predictions were clear underestimations on cohesive soils because the characteristics of Finnish soil types as substrates for vehicle motion are not well known. The 25 × 25-m DEM seems to be too inaccurate to predict the slope resistance and total resistance, whereas the results obtained with the improved DEM support the null hypothesis that the prediction is adequate enough from a terramechanical point of view and that the method could be used as a tool for predicting terrain trafficability.

Toward Agroforestry Design: An Ecological Approach - Eric J. Holzmueller (Forest Science, 2009)

Describing Maritime Pine Diameter Distributions with Johnson's SB Distribution Using a New All-Parameter Recovery Approach - Teresa Fidalgo Fonseca; Carlos Pacheco Marques; Bernard R. Parresol (Forest Science, 2009)
Forest growth and yield models that describe the heterogeneity of a stand by implicitly defining size classes are valuable tools for sustainable forest management. In stand-level growth and yield models, often stand tables representing numbers of trees by diameter class are projected through the use of probability density functions (PDFs). Theoretical knowledge shows and empirical studies corroborate that the four-parameter Johnson's SB PDF provides greater generality in fitting diameter distributions than many of the commonly applied PDFs in forestry, such as the beta, gamma, and Weibull PDFs. Distinct parameter estimation methods are available for the Johnson's SB distribution. However, few studies have been conducted that estimate the Johnson's SB PDF using a parameter recovery approach. Also, for those studies that have used a parameter recovery approach, often one (i.e., the location) or two (i.e., the location and the range) of the four parameters are assumed to be known. In this article, we present a parameter recovery approach to recover all four parameters of the Johnson's SB PDF for diameter distributions from stand variables. The location, range, and shape parameters are recovered from the median and the first three noncentral moments of the diameter distribution. The first two of these noncentral moments correspond to the average and quadratic mean diameter. The third moment is interpreted as the product of the mean diameter for the diameter distribution based on basal area, rather than stems per ha, and the squared quadratic mean diameter. The proposed methodology is demonstrated for maritime pine (Pinus pinaster Ait.) stands in Portugal.

Modeling Tree Mortality in Low- to Medium-Density Uneven-Aged Hardwood Stands Under a Selection System Using Generalized Estimating Equations - Diane Kiernan; Eddie Bevilacqua; Ralph Nyland; Lianjun Zhang (Forest Science, 2009)
Tree mortality was modeled through time in uneven-aged northern hardwood stands managed under a selection system using long-term remeasurement data. Two models were fitted and compared: a traditional logistic regression model that predicted the probability of individual tree mortality over discrete time periods and a logistic regression model estimated using generalized estimating equations (GEEs) to account for autocorrelation in the longitudinal data. Model evaluation was based on the mean prediction error, mean absolute prediction error, variance of prediction errors, and mean square error calculated using an independent validation data set. The GEE model produced smaller evaluation statistics, especially for the smaller diameter classes. The predicted probability of mortality from the two models was compared with the observed mortality across 5-cm diameter classes for two time periods. Our results indicate that the GEE model was better able to capture the change in the probability of mortality over time, especially for the smaller diameter classes, than the more traditional logistic model.

Relationship between Soil Productivity and Tree Volume in Primeval Forest Ecosystems in Northeastern China - John Yang; Yuanman Hu; Rencang Bu (Forest Science, 2009)
Soil properties are well known to influence plant productivity. Site-specific studies were conducted in primeval forest ecosystems in northeastern China to determine a quantitative relationship between soil productivity and tree volume. Three species-dominant primeval forest ecosystems (subalpine, spruce and fir, and Korean pine and hardwood) within the Changbai Mountain Natural Reserve area were selected as study sites. Soil properties of three landscape positions (convex, linear, and concave) in each of the three ecosystems were characterized, and the productivity was quantified using a soil-based productivity index (PI) model. On-site measurements of tree volume were used to assess their correlation with the soil PI values. A range of soil PI values occurred in landscape positions because of differential soil properties in each forest ecosystem. The PI values generally increased along the convex to concave transect and decreased with elevation. Soil pH and depth were identified as primary factors that limited the soil productivity, accounting for 52–56% of the PI variance. Tree volumes of each of the three ecosystems were positively correlated with soil PI values, with R2 of 0.82 to 0.87. The tree volume response to soil PI was dependent on the forest types. This field study demonstrated that the soil-based PI model would be a useful tool in identifying undesirable soil conditions of tree growth for site management and effectively predicting tree productivity based on soil properties within the site- and species-specific forest ecosystems.

Automated Analysis of in Situ Canopy Images for the Estimation of Forest Canopy Cover - Lauri Korhonen; Jaakko Heikkinen (Forest Science, 2009)
Forest canopy cover is a commonly used ecological indicator variable, but its reliable estimation in the field with, e.g., the line intersect sampling method is laborious. One alternative for obtaining this information quickly is to sample a larger area of canopy from each prespecified location within a sample plot by using digital cameras and then use image analysis techniques to extract canopy cover from the images. The first aim of this study was to implement an automated method for the estimation of canopy cover from skyward-looking canopy images obtained with standard digital cameras. The second aim was to compare the estimates obtained with the cameras and the automated analysis technique to control values measured with a vertical tube by using two different plot types and a varying angular field of view (1–50°). The results indicate that the automated analysis technique, involving an automated image thresholding algorithm and morphological image processing operations to eliminate the effect of within-crown gaps, can reliably replace manual postprocessing. With the tested sampling schemes, a 40° angle of view yielded the best approximation of the control.

Analysis of Holm Oak Intraspecific Competition Using Gamma Regression - Guillermo Gea-Izquierdo; Isabel Cañellas (Forest Science, 2009)
Analysis of plant competition is a major issue in ecology and forestry, as it influences plant growth and plant-environment interactions. Competition is expected to be lower in the sparse tree stratum of open woodlands and agroforestry systems than in closed forests. We have analyzed competition in open woodlands of Quercus ilex in the Iberian Peninsula by studying a 10-year diameter growth increment from collected samples and from consecutive National Forest Inventories. Density was the competition index selected in all models, outperforming more complex distance-dependent indices. The models showed that competition is playing a role in growth but that the covariate most correlated with growth is age or dbh as a surrogate of age. Therefore, below-ground competition is likely to be limiting tree growth, but below-ground competition is lower in open woodlands compared with that in denser forests and thus potential growth (which is strongly linked to age) is almost expressed. Model behavior was improved when data were fitted directly using generalized linear models, which do not require transforming of the dependent variable. Our results showed that modeling growth with the gamma probability distribution resulted in better models compared with Gaussian linear models. Gamma regression offers a great potential for many forestry applications.

A Plotless Density Estimator Based on the Asymptotic Limit of Ordered Distance Estimation Values - Barry J. Kronenfeld (Forest Science, 2009)
Estimation of tree density from point-tree distances is an attractive option for quick inventory of new sites, but estimators that are unbiased in clustered and dispersed situations have not been found. Noting that bias of an estimator derived from distances to the kth nearest neighbor from a random point tends to decrease with increasing k, a method is proposed for estimating the limit of an asymptotic function through a set of ordered distance estimators. A standard asymptotic model is derived from the limiting case of a clustered distribution. The proposed estimator is evaluated against 13 types of simulated generating processes, including random, clustered, dispersed, and mixed. Performance is compared with ordered distance estimation of the same rank and with fixed-area sampling with the same number of trees tallied. The proposed estimator consistently performs better than ordered distance estimation and nearly as well as fixed-area sampling in all but the most clustered situations. The estimator also provides information regarding the degree of clustering or dispersion.

Gregoire, T.G., Q.F. Lin, J. Boudreau, and R. Nelson. Regression estimation following the square-root transformation of the response For. Sci. 54(6):597–606 (Forest Science, 2009)

Effects of Timber Harvest on Aquatic Macroinvertebrate Community Composition in a Northern Idaho Watershed - John A. Gravelle; Timothy E. Link; Justin R. Broglio; Jeff H. Braatne (Forest Science, 2009)
Annual macroinvertebrate sampling was performed from 1994 to 2005 in the Mica Creek Experimental Watershed in northern Idaho to examine the relationship between contemporary timber harvest practices and the structure and diversity of aquatic macroinvertebrate assemblages. Four years of calibration, 4 years of postroad, and 4 years of postharvest (roads + harvest) data were used to analyze treatment effects. Metrics used to assess change included functional feeding group composition, organism densities, taxa richness indices, species diversity, and sediment tolerance indices. These assessments included changes to three macroinvertebrate taxa commonly used as bioindicators of stream habitat quality: Ephemeroptera (mayflies), Plecoptera (stoneflies), and Trichoptera (caddis flies) (EPT). In relation to pretreatment conditions, there were generally no major changes in functional feeding group composition or species diversity. Increases were observed in overall abundance and EPT abundance, but they largely can be explained by natural population variability. These results suggest that little or no change in macroinvertebrate communities resulted from road construction and timber harvest activities in the watershed. Substantial interannual variability was also observed, suggesting that infrequent biomonitoring may not provide adequate information to assess subtle disturbance effects in watersheds but can be an effective part of a comprehensive watershed monitoring program when coupled with other biotic and abiotic metrics.

Magnussen, S. A Balanced Repeated Replication Estimator of Sampling Variance for Apparent and Predicted Species Richness For. Sci. 55(3):189–200. (Forest Science, 2009)

An Accurate Approximation for Distance Distributions Arising in Airtanker Positioning and Related Problems - Serge B. Provost; David A. Stanford; Kaiqi Yu (Forest Science, 2009)
A moment-based methodology is proposed for approximating the distribution of the distance between two random points belonging to sets that are composed of convex polygons. The resulting density approximants are expressed as the product of a beta density function and a polynomial adjustment. Because points and line segments are merely polygons projected to lower dimensions, the method can readily be used to determine the distribution of the distance between a fixed point or a line segment and polygons. In this way, it is possible to determine the distribution of the distance from an airtanker base to an initial attack zone, represented by either a convex polygon or line segment. Several illustrative examples as well as applications to the distance between an airtanker's base and its initial attack zone, and between a transportation corridor and a wildland-urban interface are presented.

Modeling Stand Density Effects on Taper for Jack Pine and Black Spruce Plantations Using Dimensional Analysis - Mahadev Sharma; John Parton (Forest Science, 2009)
A taper equation was developed for jack pine and black spruce trees growing at varying density using a dimensional analysis approach. Data used in this study came from stem analysis on 1,135 jack pine (Pinus banksiana Lamb.) and 1,189 black spruce (Picea mariana [Mill.] B.S.P.) trees sampled from 25 even-aged monospecific plantations in the Canadian boreal forest region of Northern Ontario. About half of the trees were randomly selected for model development, with the remainder used for model evaluation. A nonlinear mixed-effects approach was applied in fitting the taper equation. The predictive accuracy of the model was improved by including random-effects parameters for a new tree based on upper stem diameter measurements. Three scenarios of using upper stem diameter measurements to predict random effects were examined for predictive accuracy: one diameter at any height along the bole; two diameters, one each from below and above breast height; and three diameters, one from below and the other two from above breast height. The upper height at which the diameter was measured was limited to 65% of total tree height for practical reasons. For the first scenario, the model calibrated using a diameter measurement from between 34 and 38% of total height provided the best predictions of inside-bark diameters. For the second scenario, the model calibrated using one diameter from near the stump and the other from close to 65% of total height produced the least bias in predicting inside-bark diameters. For the third scenario, the model calibrated using the diameters from near the stump and at approximately 35 and 65% of total height provided the highest prediction accuracy.

Improved Calibration of Nonlinear Mixed-Effects Models Demonstrated on a Height Growth Function - Shawn X. Meng; Shongming Huang (Forest Science, 2009)
The calibration of a nonlinear mixed-effects model is of critical importance in making local predictions. In previous applications, simplified equations were generally used to calibrate nonlinear mixed-effects models fitted using the first-order methods implemented through the NLINMIX macro in SAS. This simplification, however, could distort local predictions. In this study, using a nonlinear height growth model of lodgepole pine (Pinus contorta var. latifolia Engelm.), we demonstrated on two data sets the procedures to obtain an improved calibration of the height growth model. The differences between the improved and conventional calibrations were found to be significant. Calibration of the nonlinear mixed models using the improved method resulted in not only reduced bias but also reduced variance of the errors. It is recommended that the improved calibration method be used. A computing program detailing the procedures for obtaining the improved calibration was developed.

Short-Term Physiological Responses of Black Walnut ( Juglans nigra L.) to Plantation Thinning - Martin-Michel Gauthier; Douglass F. Jacobs (Forest Science, 2009)
We studied physiological responses of mature black walnut (Juglans nigra L.) trees to determine the time necessary for photosynthetic adaptation to plantation thinning. Measurements were taken before treatment (July 25, 2007) and for the first 3 days after thinning (July 29, 30, and 31, 2007). Measurements did not continue in August because trees had developed leaf anthracnose and senescence was occurring, but measurements resumed on May 29, 2008 and July 29, 2008. Repeated measures of net photosynthetic rates (A) showed that thinned trees did not respond immediately to partial release, but nearly doubled in A compared with a 35% increase in control trees 1 year after thinning. Significant increases in light, leaf water status, relative humidity of the air, and nitrogen content per unit leaf area were also found in thinned trees 1 year after treatment. From these variables, light (r2 = 0.79) showed the strongest relationship with A. Results suggest that black walnut requires a full growing season before it responds to treatment when thinned late in the growing season. Thinning earlier, such as in June, may trigger a more rapid adaptation in A of thinned trees that was not detected in our study.

Facilitating Integrated Recreation Management: Assessing Conflict Reduction Benefits in a Common Metric - Kreg Lindberg; Peter Fredman; Tobias Heldt (Forest Science, 2009)
Recreation management on public land often involves trade-offs. For example, cross-country skiers may experience conflict with snowmobiles. A potential management response is trail separation, which may lead to gains to skiers but also ecological and financial costs associated with creation of a new trail. If separation involves snowmobile access restrictions, there may be experiential losses for that user group. Management responses are not always based on explicit identification and integration of the gains and losses accruing across diverse stakeholders and dimensions; economics provides a criterion, a metric, and measurement tools to facilitate such integration. A Swedish case study illustrates this approach and assesses values accruing to skiers from reduced snowmobile presence. Cross-country skiers were sampled on-site in the southern Jämtland mountain region, and follow-up mail surveys included choice experiment scenarios. Conditional logit analysis of the 1,468 completed scenarios indicates that skier welfare gains from conflict reduction are substantial and reflect both direct and indirect contact. A change from sharing trails to not seeing, hearing, or smelling snowmobiles leads to gains of 185 kronor (US$23) per skier party.

A Balanced Repeated Replication Estimator of Sampling Variance for Apparent and Predicted Species Richness - Steen Magnussen (Forest Science, 2009)
Design-based estimators of the sampling variance for apparent (S0 = observed) and predicted species richness (S̃) have been lacking. A balanced repeated replication (BRR) estimator is proposed and recommended for S0 and S̃. Good performance of the estimators is demonstrated in two contrasting examples with Monte Carlo (MC) simulations of simple random sampling with fixed area quadrats (plots) for estimating forest tree species richness. Chao and Lee's estimator of species richness was used for S̃. In BRR a set of half-samples forming an orthogonal design with respect to the inclusion/exclusion of sample records is used to produce estimates of S̃ from the observed half-sample and models for the effect of data-splitting. BRR estimates of the sampling variance of S0 were close to the MC estimates in the examples from eastern Canada (PROV) and the Barro Colorado Island (BCI) and clearly superior to naive model-based estimates. BRR estimates of S̃ were generally close to their MC counterparts, but in BCI a bias of approximately −10% was seen in small samples (n ≤ 24). BRR estimates of sampling variance of S̃ in PROV were close to the MC estimates for n ≤ 60. With larger sample sizes the BRR estimates drifted toward values obtained with Chao and Lee's model-based variance estimator. In BCI the opposite was true.

Legacy of Insect Defoliators: Increased Wind-Related Mortality Two Decades After a Spruce Budworm Outbreak - Sarah L. Taylor; David A. MacLean (Forest Science, 2009)
Effects of spruce budworm (Choristoneura fumiferana Clem.) outbreaks on growth and survival of balsam fir (Abies balsamea [L.] Mill.) and spruce (Picea spp.) are well documented, but few studies extend beyond 10 years after defoliation ceased. We used inventory data from 106 permanent sample plots in >50-year-old balsam fir stands in northern New Brunswick, Canada, to determine legacy effects of the 1969–1993 budworm outbreak on stand development up to 29 years after defoliation ceased. Defoliation data were from annual aerial surveys from 1945 to 1993 and plot ground sampling from 1985 to 1993. Plots were stratified into net stand volume development categories (decreasing, stable, and increasing 1985–2005 stemwood volume) and related to outbreak phases (outbreak, direct 1–10 years after defoliation ceased, and legacy >10 years), outbreak severity (1–4 [low], 5–8 [medium], and 9–12 [high] years of defoliation), and stand age (mature and overmature). Stand age was an important factor influencing outbreak severity (e.g., r2 = 0.383, P < 0.01). Trend and rate of volume development over time were related to past outbreak severity and increased rate of postoutbreak wind-related mortality, which peaked at 11 m3/ha/yr 11–15 years after defoliation ceased. Results indicate that aging postoutbreak stands are more vulnerable to wind disturbance events, effecting rapid stand decline.

Modeling Containment of Large Wildfires Using Generalized Linear Mixed-Model Analysis - Mark Finney; Isaac C. Grenfell; Charles W. McHugh (Forest Science, 2009)
Billions of dollars are spent annually in the United States to contain large wildland fires, but the factors contributing to suppression success remain poorly understood. We used a regression model (generalized linear mixed-model) to model containment probability of individual fires, assuming that containment was a repeated-measures problem (fixed effect) and individual fires were random effects. Changes in daily fire size from 306 fires occurring in years 2001–2005 were processed to identify intervals of high spread from those of low spread. The model was tested against independent data from 140 fires in 2006. The analysis suggested that containment was positively related to the number of consecutive days during which the fire grew little and the number of previous intervals. Containment probability was negatively related to the length of intervals during which the fire exhibited high spread and the presence of timber fuel types, but fire size was not a significant predictor. Characterization of containment probability may be a useful component of cost-benefit analysis of large fire management and planning systems.

Approaches for Modeling Vertical Distribution of Maximum Knot Size in Black Spruce: A Comparison of Fixed- and Mixed-Effects Nonlinear Models - John A. Kershaw; Jeff G. Benjamin; Aaron R. Weiskittel (Forest Science, 2009)
Both linear and nonlinear hierarchical mixed-effects models have been used in recent years to analyze nested data sets. These types of models are effective for partitioning variance between hierarchical levels and increasing model flexibility. Models of knot size and distribution have been developed for several commercially important conifer species. Modeling knots is particularly amendable to the mixed-models approach as they are inherently nested at multiple levels including the individual whorl, tree, and stand levels. Although mixed models are effective for addressing hierarchical nesting of data, in this study we contend that improvements achieved by inclusion of mixed effects can be effectively negated with the use of an appropriate model form. This contention is presented as a case study on the development of a maximum knot size model for plantation-grown black spruce in Ontario (Picea mariana [Mill.] BSP). With a naive and simple model form, the nonlinear mixed-effects approach was significantly superior to comparable generalized nonlinear models as the root mean square error was 16% lower. In contrast, when a model form that accounted for primary covariates with a robust model form was used, difference in root mean square error between nonlinear mixed-effects and generalized nonlinear models was approximately 6%. In addition, graphic techniques for exploring distributions of random effects are presented and discussed. Mixed models are effective tools, but, as illustrated by this case study, their limitations need to be recognized and use of mixed models should not precede development of sound model forms.

Early Growth Responses of Lodgepole Pine and Douglas-Fir to Soil Compaction, Organic Matter Removal, and Rehabilitation Treatments in Southeastern British Columbia - Xiao Tan; Michael Curran; Scott Chang; Douglas Maynard (Forest Science, 2009)
Effects of soil compaction, organic matter removal, and rehabilitation on lodgepole pine (Pinus contorta Dougl. ex. Loud.) and Douglas-fir (Pseudotsuga menziesii var. menziesii) were studied after three growing seasons in a long-term soil productivity study established on three calcareous soils in southeastern British Columbia. Effects of soil compaction and organic matter removal on tree growth were site and species specific. Moderate soil compaction increased the diameter and height increment of both species within the stem-only harvest treatment on all three sites, particularly at the coarser textured site (Emily Creek). Compaction tended to reduce tree mortality. Growth of both species was reduced by forest floor removal in the noncompacted soil at Mud Creek and Emily Creek and by whole-tree harvest in the moderately compacted soil at Mud Creek and Kootenay East, possibly due to treatment-induced water limitation. Whole-tree harvest and forest floor removal stimulated lodgepole pine and Douglas-fir growth in the noncompacted soil at Kootenay East. The rehabilitation treatment (established by tilling a heavily compacted soil) reduced lodgepole pine tree mortality on all sites and increased rootcollar diameter and height increment at Mud Creek and Kootenay East. Our findings may provide early growth indication and help assess long-term tree growth trends at these and other long-term soil productivity or related sites.

Self-Organizing Map Analysis of Planted Soil Infiltration Systems for Treatment of Log Yard Runoff - Åsa Hedmark; Liang Zhang; Miklas Scholz; Pär Aronsson; Torbjörn Elowson (Forest Science, 2009)
Infiltration through a soil system planted with four different species was assessed as a sustainable treatment method for logyard runoff at a field-scale experimental site in Sweden. Runoff was infiltrated through soil planted with Alnus glutinosa (L.) Gärtner (common alder), Salix schwerinii × viminalis (willow variety “Gudrun”), Lolium perenne (L.) (rye grass), and Phalaris arundinacea (L.) (reed canary grass). Analyses of variance and t tests showed no significant differences in treatment when the different plants were compared with each other, and there were also no significant differences between the tree and the grass species. The infiltration treatment was effective in reducing total organic carbon and total phosphorus in the runoff even when the loads on the infiltration system increased over time. The self-organizing map (SOM) model was applied to assess the relationships between different water quality variables and to predict total nitrogen (TN) and total phosphorus (TP) concentrations. A supplementary correlation analysis confirmed the key relationships among variables revealed by the SOM. The SOM model performed very well in predicting TN and TP concentrations with the help of other water quality variables, which can be measured more cost effectively.

Public Participation GIS: A New Method for Use in National Forest Planning - Gregory G. Brown; Pat Reed (Forest Science, 2009)
In this article we describe and evaluate a public participation geographic information systems (PPGIS) methodology for use in national forest planning in the United States. The Internet-based mapping method collects public landscape values and special places data for input into a national forest planning decision support system. The PPGIS method presupposes that, within their existing statutory framework, national forests should be managed for compatibility with the range of values the public holds for those lands and that inadequate understanding, modeling, and documentation of place-specific forest values can negatively affect public acceptance, viability, and the usefulness of national forest plans. In this article we 1) review previous applications of landscape value mapping methods across a variety of planning applications, 2) describe the participatory, Internet mapping method used in three studies of national forests in Arizona and Oregon in 2006 and 2007, 3) present and evaluate the results to show likely future implementation constraints, and 4) based on lessons learned, describe a recommended PPGIS protocol for national forest planning. The results from the three studies demonstrate that an Internet, participatory mapping method, although not without limitations, can be effective in measuring landscape value and special place data for use in a variety of forest planning processes. Because the protocol expands and in a sense democratizes the agency's public participation process, implementation of the PPGIS protocol across the national forest system can help restore public trust in the agency's forest planning processes and forest management decisions.

Evaluating Approaches for Solving the Area Restriction Model in Harvest Scheduling - Marcos Goycoolea; Alan Murray; Juan Pablo Vielma; Andres Weintraub (Forest Science, 2009)
We survey three integer-programming approaches for solving the area restriction model for harvest scheduling. We describe and analyze each of these approaches in detail, comparing them both from a modeling and computational point of view. In our analysis of these formulations as modeling tools, we show how each can be extended to incorporate additional harvest scheduling concerns. In our computational analysis we illustrate the strengths and weaknesses of each formulation as a practical optimization tool by studying harvest scheduling in four North American forests.

Multipath Mitigation under Forest Canopies: A Choke Ring Antenna Solution - Scott Danskin; Pete Bettinger; Thomas Jordan (Forest Science, 2009)
Evaluating the accuracy of global positioning system (GPS) receivers in applications under forest canopies has become an area of increasing interest. Reducing the error experienced by multipath present under forested conditions has also been a significant concern. We present results of assessing a choke ring antenna solution to the reduction of multipath effects under forest canopies. This system serves to increase the accuracy of positional fixes as well as provide a baseline for assessing multipath effects. We assessed these by comparing results to data collected by separate antenna configurations (yet same receiver) on varying slope positions and canopy conditions. Using a choke ring antenna, we found horizontal position accuracy of differentially corrected data to range from 0.32 to 0.88 m root mean square error reported at 95% confidence across a topographic gradient during leaf-on conditions. Under leaf-off conditions the horizontal position accuracy ranged from 0.35 to 0.69 m. Similar differentially corrected data collected using a standard beacon antenna showed that horizontal position accuracy ranged from 4.9 to 6.1 m during leaf-on conditions and from 3.3 to 5.8 m during leaf-off conditions. When sampled, the data from the two systems were collected within 1 minute of each other; thus, we assume a very similar plane and satellite arrangement. Coupled with topographic factors, a minimum multipath error effect could be determined for this receiver for given site conditions by taking the difference between the two levels of error.

Adaptive Decision Analysis in Forest Management Planning - Pekka Leskinen; Teppo Hujala; Jukka Tikkanen; Tuomo Kainulainen; Annika Kangas; Mikko Kurttila; Jouni Pykäläinen; Leena Leskinen (Forest Science, 2009)
Societal responsibilities of forestry have diversified, and criteria other than those related to wood production have been given more weight. Demands for forest management planning methods have changed in line with the changes in the operational environment. Thus, forest planners are facing a growing demand for more versatile and customer-oriented decision aid systems and practices in which the data are cost effectively acquired and used. So far, forest planning research has concentrated mainly on the general development of multiobjective and participatory planning methods in the numerical framework. This focus has unintentionally led to practices for which the decision analysis process is often controlled only by the technical needs of the planning methods in a unified setting, independently of the problem characteristics. However, it is important to adapt the use of planning methodologies to each planning problem and use the available information about important variables efficiently. In this article, we introduce a theoretical and methodological framework for adaptive decision analysis (ADA) for forest management planning. In ADA, different decision-support service options, comprising both qualitative and quantitative components, are maintained and carried out flexibly in each planning case with the aid of an adapting processor and feedback management, resulting in computational, social, and organizational learning.

Effects of Stand Regeneration Management Regimes and Age on Genetic Structure of Quercus aquifolioides (Sclerophyllous Oak) in Southwestern China - Zhongsheng Wang; Hong Liu; Na Wei; Weixiang Xu; Shuqing An; Shirong Liu (Forest Science, 2009)
As a representative relict forest type, the sclerophyllous oak (Quercus aquifolioides Rehd. et Wils.) forests in the Himalayas-Hengduanshan Mountains of China have been either nearly completely destroyed or heavily fragmented, mostly due to the long-lasting overexploitation by local human population. To evaluate the effect of current silvicultural treatments on regeneration of sclerophyllous oak, we compared inter simple sequence repeats, measures of genetic variation of this species regenerating in three types of stands: natural old-growth oak forest, clearcut spruce plantation, and clearcut naturally regenerated stands in the Miyaluo area, western Sichuan Province of China. Results showed that populations of Q. aquifolioides in the old-growth stands displayed the highest level of genetic diversity, whereas populations in the clearcut naturally regenerated stands had the lowest. In addition, we found that populations in the older spruce plantations (e.g., stands ≥50 years old) were genetically more diverse than those in the younger sites. These findings had the following immediate implications: forest clearcuts had significantly reduced genetic variability within populations of Q. aquifolioides; artificial reforestation of spruce after clearcut could promote the recovery of genetic diversity in Q. aquifolioides, especially in the older stands; and severe human and livestock disturbances hindered the recovery of genetic diversity of Q. aquifolioides in the naturally regenerated stands. We recommend active thinning in spruce plantations (at approximately age 30-40 years) via selective logging at times of rapid height growth and crown closure to promote multistoried stand structures and canopy gaps suitable for the survival and growth of Q. aquifolioides. Finally, we recommend strict management control in the naturally regenerated stands to limit the utilities of these stands by humans and their livestock to facilitate the recovery of Q. aquifolioides genetic diversity.

Canopy Cover Estimation in Semiarid Woodlands: Comparison of Field-Based and Remote Sensing Methods - Dongwook Ko; Nathan Bristow; David Greenwood; Peter Weisberg (Forest Science, 2009)
Canopy cover is a widely used measurement for characterizing forest structure. Numerous comparative studies have been conducted for a variety of canopy cover field methods. However, comparisons of canopy cover methodology are lacking for semiarid woodland, characterized by short-statured trees, simple vertical canopy structure, and relatively low canopy cover. Furthermore, there is limited knowledge on the compatibility between field and remote sensing methods, despite the increasing interest in scaling up canopy cover estimates from forest stands to large landscapes. In this study we investigated the use and functional similarity of various canopy cover field methods and a remote sensing method in semiarid pinyon-juniper woodlands in the Great Basin of the western United States. We compared line intercept, vertical densitometer, spherical densiometer, and crown radius methods with each other and with a remote sensing method using object-oriented image classification of digital orthophotography. Our results show that methods using a wider angular view generated higher canopy cover estimates. This difference may be greater in semiarid woodland that in mesic forest because of differences in canopy architecture. Canopy cover from remote sensing showed a nonlinear relationship with that from field-based methods. Such nonlinearities need to be considered when remote sensing is used to extrapolate canopy cover from stand to landscape scales or when field-based canopy cover estimates are used to calibrate or validate remote sensing classifications.

Finding Efficient Harvest Schedules under Three Conflicting Objectives - Sándor F. Tóth; Marc E. McDill (Forest Science, 2009)
Public forests have many conflicting uses. Designing forest management schemes that provide the public with an optimal bundle of benefits is therefore a major challenge. Although a capability to quantify and visualize the tradeoffs between the competing objectives can be very useful for decisionmakers, developing this capability presents unique difficulties if three or more conflicting objectives are present and the solution alternatives are discrete. This study extends four multiobjective programming methods to generate spatially explicit forest management alternatives that are efficient (nondominated) with respect to three or more competing objectives. The algorithms were applied to a hypothetical forest planning problem with three timber- and wildlife-related objectives. Whereas the ε-Constraining and the proposed Alpha-Delta methods found a larger number of efficient alternatives, the Modified Weighted Objective Function and the Tchebycheff methods provided better overall estimation of the timber and nontimber tradeoffs associated with the test problem. In addition, the former two methods allowed a greater degree of user control and are easier to generalize to n-objective problems.

Sources of Variation in the Self-Thinning Boundary Line for Three Species with Varying Levels of Shade Tolerance - Aaron Weiskittel; Peter Gould; Hailemariam Temesgen (Forest Science, 2009)
The species self-thinning boundary line has been widely analyzed with a variety of statistical techniques. Most previous studies in the forestry literature have reported that the relationship does not differ across a range of stand and site factors, but these studies have primarily used statistical techniques that make model fitting subjective or interpretation of covariate significance difficult. There is growing evidence that the use of stochastic frontier analysis is an effective statistical means for objectively fitting the species self-thinning boundary line, offering the opportunity to test the influence of additional covariates. Using extensive even-aged coastal Douglas-fir (Pseudotsuga menziesii var. menziesii [Mirb.] Franco), western hemlock (Tsuga heterophylla), and red alder (Alnus rubra Bong.) data sets in the Pacific Northwest, we examined the assumption that the intercept and slope of the species self-thinning boundary line are insensitive to stand and site factors. Likelihood ratio tests indicated that site index, stand origin (natural versus planted), and purity (proportion of basal area in the primary species) significantly influenced the species self-thinning boundary line intercept for each of the species examined in this study. In Douglas-fir and western hemlock, the slope of the self-thinning boundary was also dependent on stand origin as well as site index in the case of Douglas-fir. Fertilization did not significantly influence the intercept or slope of the species self-thinning line for Douglas-fir and western hemlock. In addition, the inclusion of site aspect and dryness index marginally improved the red alder model of self-thinning, but neither site soil nor climatic variables improved the models for western hemlock and Douglas-fir. Thus, the species self-thinning boundary line can vary significantly among stands, and its variation is driven by several distinct factors; stochastic frontier analysis is an effective tool for identifying these factors.

Statistical Power of Intervention Analyses: Simulation and Empirical Application to Treated Lumber Prices - Jeffrey P. Prestemon (Forest Science, 2009)
Timber product markets are subject to large shocks deriving from natural disturbances and policy shifts. Statistical modeling of shocks is often done to assess their economic importance. In this article, I simulate the statistical power of univariate and bivariate methods of shock detection using time series intervention models. Simulations show that bivariate methods are several times more statistically powerful than univariate methods when underlying series are nonstationary and potentially involved in cointegrating relationships. In an empirical application to detect the long-run price impacts of the voluntary phase-out of chromated copper arsenate in pressure-treating southern pine lumber for residential applications, I find the multivariate methods to be more powerful as well. I identify highly significant long-run price increases of 11% for two of three treated southern pine dimension lumber price series evaluated using multivariate approaches. The univariate method detected a long-run increase only for the third product, and the statistical significance was weak, although comparable, in magnitude to the first two products.

Identification of Scandinavian Commercial Species of Individual Trees from Airborne Laser Scanning Data Using Alpha Shape Metrics - Jari Vauhkonen; Timo Tokola; Petteri Packalén; Matti Maltamo (Forest Science, 2009)
Airborne laser scanning (ALS) data are not usually considered to be very informative with respect to tree species, and this information is often obtained by combining such data with spectral image material. The aim here was to test the ability of variables derived solely from ALS data to describe the crown shape and structure characteristics required for tree species discrimination. For that purpose, we constructed tree crown approximations from the three-dimensional return data by applying a computational geometry approach, the alpha shape concept, and developed metrics for describing them. We examined the ability of these metrics to classify Scandinavian commercial species (pine, spruce, and deciduous trees) by means of linear discriminant analysis and compared the alpha shape metrics with groups of ALS-based height, density, intensity, and two-dimensional texture variables. For evaluating the classification accuracy, we used a test data set composed of 92 dominant or codominant trees detected and delineated manually from ALS data with a density of approximately 40 returns m−2. The alpha shape metrics proved capable of discriminating between all three species classes evaluated, and several height distribution and texture variables were found to discriminate between the coniferous tree species. An overall accuracy of approximately 95% and a κ coefficient of 0.90 was achieved using a combination of the variables. Because this initial application of the alpha shape metrics was carried out using a test data set on only such trees that are clearly detectable from remotely sensed data, further research is required to apply the approach presented here within stands with a continuous canopy. Furthermore, as the tree observations considered here were highly biased toward mature coniferous trees, experiments using more representative data sets are needed to generalize the result obtained.

GIS-Based Modeling of Pinyon–Juniper Woodland Structure in the Great Basin - David L. Greenwood; Peter J. Weisberg (Forest Science, 2009)
Pinyon–juniper woodlands are a dominant vegetation type across the Intermountain West, covering an estimated 30 million ha. Increases in density, cover, and aerial extent over recent decades have been associated with altered fire regimes, tree mortality, and reduced understory productivity. In our study we sought to determine how environmental factors influence woodland structure and to exploit such abiotic influences to improve our ability to model woodland structure from digital aerial photography. We developed and applied a methodology for automated tree canopy cover mapping using an object-oriented classifier. The resulting classification was used to scale up stand inventory measurements (0.1 ha) across 11 mountain ranges to a 3,250 km2 area. Predictive models were compared with field-measured values from a validation sample for tree canopy cover, basal area, height, and stand density index. Linear mixed-effects regression models demonstrated consistent relationships between woodland structure attributes and environmental variables. More productive sites supported greater tree densities, whereas less productive sites supported fewer, larger trees. Relatively weak relationships for certain variables (e.g., tree height) suggest that woodland structure-environment relationships are partially obscured by natural disturbances and land use history.

On the Use of Statistical Tests with Non-Normally Distributed Data in Landscape Change Detection - Bogdan Strimbu; Gordon Hickey; Vladimir Strimbu; John Innes (Forest Science, 2009)
Research assessing changes of the main attributes describing forested landscapes often supply contradictory findings when viewed within an unchanging socioeconomic framework (i.e., unchanging forest management policies and no human population increase). Some studies suggest forest decline, others no change, and others expansion. We used ground-measured forest inventory data from Romania to examine the evolution of the forested landscape over a 10-year period (1993–2003), during which no substantial transformations occurred in the human population or in forest management policies. Within a repeated-measures framework, a range of parametric and nonparametric statistical tests were used to evaluate forest change. Our results revealed that significant structural changes occurred at the landscape level. The changes were detected by several multivariate and nonparametric techniques. Multivariate techniques revealed that “age class,” “phyto-climatic zone,” and “ownership type” attributes had a significant influence in delineating between the 1993 and 2003 forested landscape. The univariate nonparametric tests indicated that there are factors not considered in the planning process (such as ownership or inflation) that can lead to a significant decrease of the main quantitative forest attributes (such as canopy closure or height), a decrease undetected by the corresponding parametrical statistics. Our research revealed that even when the distribution did not exhibit significant skewness, the nonparametric techniques could be more efficient than the corresponding parametric techniques by detecting significant changes of the attributes describing the forested landscape.

An Application of a Reduced Cost Approach to Spatial Forest Planning - Timo Pukkala; Tero Heinonen; Mikko Kurttila (Forest Science, 2009)
The task of forest planning is to find the best combination of treatment schedules for forest stands. With many stands and several alternatives per stand the number of possible combinations becomes very large and standard heuristics for combinatorial optimization such as simulated annealing (SA), tabu search, and genetic algorithm become slow. One way to deal with the problem of large decision space is to decompose the forest-level problem into stand-level subproblems. We developed a spatial application of the decomposing technique proposed by Hoganson and Rose. This method maximizes the reduced cost (RC) of each stand. The dual prices of forest-level constraints appear in the RC function and they tie the stand-level problems together. In our spatial application of the RC method we used a multiobjective stand-level objective function. The function included spatial objective variables, the values of which depended on adjacent stands. The dual prices of nonspatial forest-level constraints were gradually adjusted by using a variant of the subgradient method, until the set of stand-level solutions fulfilled the forest-level constraints. The method was compared with a cellular automaton and the SA heuristic in a spatial problem in two different forests. The results suggest that the spatial application of the RC method is competitive with heuristics currently used in forest planning. It was slightly superior to SA in terms of the objective function value of SA. The method is easy to use because it has few parameters.

A Review of Forest Succession Models and Their Suitability for Forest Management Planning - Anthony R. Taylor; Han Y. H. Chen; Laird VanDamme (Forest Science, 2009)
Successful implementation of ecosystem management requires strategic forest management planning, including the ability to forecast future forest composition. With advances in ecological modeling, many forms of succession models are available. In this review, we provide a broad synthesis of the methods used to model forest succession and discuss their suitability for strategic forest management planning. Qualitative models underpin theoretical understanding of forest succession but require expression in more formal quantitative forms to be applicable to strategic planning. Quantitative modeling methods can be differentiated as empirical or mechanistic. Empirical models rely on observational data of successional change. Mechanistic models rely on knowledge of underlying ecological processes to simulate succession. Hybrid mechanistic models represent a compromise in ecological modeling between empirical robustness and theoretical understanding. With their increased flexibility for scenario planning and enhanced representation of ecosystem processes, hybrid models are well suited to addressing the multiple environmental and social factors increasingly being considered under ecosystem management. However, empirical models still remain a suitable and practical alternative because hybrid models require increased resources to initialize, operate, and interpret; emphasize understanding rather than prediction; and assume that the modeled processes they represent are adequately understood.

Estimating Current Forest Attributes from Paneled Inventory Data Using Plot-Level Imputation: A Study from the Pacific Northwest - Bianca N.I. Eskelson; Hailemariam Temesgen; Tara M. Barrett (Forest Science, 2009)
Information on current forest condition is essential to assess and characterize resources and to support resource management and policy decisions. The 1998 Farm Bill mandates the US Forest Service to conduct annual inventories to provide annual updates of each state's forest. In annual inventories, the sample size of 1 year (panel) is only a portion of the full sample and therefore the precision of the estimations for any given year is low. To achieve higher precision, the Forest Inventory and Analysis program uses a moving average (MA), which combines the data of multiple panels, as default estimator. The MA can result in biased estimates of current conditions and alternative methods are sought. Alternatives to MA have not yet been explored in the Pacific Northwest. Data from Oregon and Washington national forests were used to examine a weighted moving average (WMA) and three imputation approaches: most similar neighbor, gradient nearest neighbor, and randomForest (RF). Using the most recent measurements of the variables of interest as ancillary variables, RF provided almost unbiased estimates that were comparable to those of the MA and WMA estimators in terms of root mean square error.

Crown Recession Patterns in Three Conifer Species of the Northern Rocky Mountains - Sean M. Garber; Robert A. Monserud; Douglas A. Maguire (Forest Science, 2008)
Crown length is a fundamental tree dimension for characterizing growth potential, wildlife habitat, and wood quality. The relative rates of height growth and crown recession determine the progression of crown length over time. We investigated patterns in crown recession of three co-occurring species in the northern Rocky Mountains: western white pine (Pinus monticola Dougl. ex D. Don), ponderosa pine (Pinus ponderosa Dougl. ex P. & C. Laws.), and interior Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco var. glauca). Past height, diameter, and crown base on 169 forest-grown trees were reconstructed by detailed stem analysis. Crown base was estimated for each year of the tree's life by dating the mortality of all whorl branches. Five-year crown recession was modeled in two parts, the first predicting the probability that a crown recedes and the second estimating recession conditional on its occurrence. The probability of crown recession increased and then decreased with an increasing crown ratio for all three species and similarly peaked over initial tree size. Conditional crown recession increased monotonically with crown ratio for ponderosa pine but peaked at crown ratios between 0.7 and 0.9 in western white pine and Douglas-fir. The resulting models lend insight into factors controlling rates of crown recession and their variation among species and differing initial conditions.

Cogongrass ( Imperata cylindrica ), an Alien Invasive Grass, Reduces Survival and Productivity of an Establishing Pine Forest - Pedram Daneshgar; Shibu Jose; Alexandra Collins; Craig Ramsey (Forest Science, 2008)
A 27-month-long study was conducted to compare the impacts of Imperata cylindrica (L.) (Beauv.) and native vegetation competition on the productivity of Pinus taeda (L.) seedlings. In March 2003, 1-year-old pine seedlings were planted in the following treatments: vegetation free (VF), native competition (NC), and I. cylindrica (IC) competition. At the end of the study, only 26% of the IC seedlings survived, half of what was observed in the NC treatment. The IC seedlings had significantly smaller root collar diameter than the NC seedlings (P < 0.0001) after the first growing season and by the end of the third growing season the height and stem volume index were significantly less as well (P < 0.0001). After one full growing season, the NC and IC pine seedlings had 21 and 11.5% of the total biomass of the VF seedlings, respectively. After three growing seasons, the IC pine seedling total biomass was 2.4% of that of the VF seedlings and 18% of that of the NC seedlings (P < 0.0001). The greatest difference was in the pine needle biomass with the IC pine needle biomass being only 11% of that of the NC. During the first growing season, the IC pine seedlings maintained the lowest levels of light-saturated net photosynthesis and stomatal conductance. These results may be explained by reduced amounts of foliar nitrogen and water stress that result from I. cylindrica competition. The pines in the IC treatment had the lowest total foliar surface area and the lowest specific leaf area, which may explain the reduced productivity. Evidence from this study suggests that I. cylindrica competition significantly reduces the productivity and growth of P. taeda seedlings compared with that from native vegetation.

An Estimator of Prediction Error Variance for Projection Equations - Chengcai Ni; Lianjun Zhang (Forest Science, 2008)
An estimator of prediction error variance for projection equations was derived using the first-order Taylor expansion in this study. The estimator, a modified estimator of the prediction error variance for a population mean regression model, was adapted for situations in which projection equations are applied to unsampled individuals. The estimator accounted for the errors associated with the response variable on the right side of a projection equation, as well as the errors associated with parameter estimation and serial correlations in data. The application of the estimator was demonstrated using the example of 140 trees with diameters measured annually from age 5 to 19. The results indicated that the estimator represented prediction error variance well and was useful for constructing prediction intervals for a given projection equation and providing information on the contributions of the variance components associated with different error sources. It was evident that the error associated with the prior observation of the response variable of a projection equation had an important impact on model predictions for forward projections. Overlooking this variance component may result in significant misestimation for the prediction errors of the projection equation.

Base–Age Invariant Site Index Models from a Generalized Algebraic Parameter Prediction Approach - Mingliang Wang; Keith Rennolls; Bruce E. Borders (Forest Science, 2008)
A simple idea is proposed to develop polymorphic base–age invariant models with multiple asymptotes: the asymptotic parameter is taken as the site-specific parameter (χ) and one of the other parameters is taken as dependent on χ as a simple power function. This approach is a constrained form of the generalized algebraic difference approach (GADA) and eliminates the requirement in previous GADA models to obtain an explicit solution for χ: χ just has to be estimated along with other parameters of the model. The approach may be used to adapt base–age specific models, developed in terms of the “parameter prediction” method, to be “base–age invariant.” The new approach and the models it produces are evaluated on data sets for Chinese fir, red alder, and birch, with models being fitted using the “dummy variable” method in which each observed data series has its own site-specific χ parameter. The base–age invariant models developed are superior to their comparable base–age specific models.

Regional Applicability of Forest Height and Aboveground Biomass Models for the Geoscience Laser Altimeter System - Dirk Pflugmacher; Warren Cohen; Robert Kennedy; Michael Lefsky (Forest Science, 2008)
Accurate estimates of forest aboveground biomass are needed to reduce uncertainties in global and regional terrestrial carbon fluxes. In this study we investigated the utility of the Geoscience Laser Altimeter System (GLAS) onboard the Ice, Cloud and land Elevation Satellite for large-scale biomass inventories. GLAS is the first spaceborne lidar sensor that will provide global estimates of forest height. We compared accuracy and regional variability of GLAS height estimates with data from the US Forest Service Inventory and Analysis (FIA) program and found that current GLAS algorithms provided generally accurate estimates of height. GLAS heights were on average 2–3 m lower than FIA estimates. To translate GLAS-estimated heights into forest biomass will require general allometric equations. Analysis of the regional variability of forest height-biomass relationships using FIA field data indicates that general nonspecies specific equations are applicable without a significant loss of prediction accuracy. We developed biomass models from FIA data and applied them to the GLAS-estimated heights. Regional estimates of forest biomass from GLAS differed between 39.7 and 58.2 Mg ha−1 compared with FIA.

Evaluation of Four Methods to Estimate Parameters of an Annual Tree Survival and Diameter Growth Model - Quang Cao; Mike Strub (Forest Science, 2008)
An approach to simultaneously estimate parameters of an annual tree growth model was developed, in which the sum of log-likelihood functions for tree survival and diameter growth was maximized. Four methods for acquiring interim values of stand density were evaluated: (1) Updating Attributes, in which individual tree values were summarized at the end of each year within the growth period to predict interim stand-level attributes, (2) Predicting Attributes, in which stand attributes were predicted annually using a stand-level model, (3) Linear Interpolation, in which stand attributes were predicted by linear interpolation, and finally (4) Initial Values, in which stand attributes at the beginning of the growth period were used as predictors throughout the growing period, and the rate of change for tree survival and diameter was assumed to be constant for this period. Data from the Southwide Seed Source Study of loblolly pine (Pinus taeda L.) showed that, overall, the Updating Attributes and Predicting Attributes produced better evaluation statistics in predicting tree survival and diameter growth than did the other two methods. A simulation study confirmed that these two methods produced the least biased estimates of parameters. Compared with the Updating Attributes method, the Predicting Attributes method produced similar evaluation statistics in predicting tree survival and diameter growth and similar bias in estimating model parameters. The Predicting Attributes method therefore offers a reasonable alternative to the Updating Attributes method, because of the ease of programming in available software languages.

Assessing the Relative Importance of Tangible and Intangible Resources: Empirical Results from the Forest Industry - Katja Lähtinen; Arto Haara; Pekka Leskinen; Anne Toppinen (Forest Science, 2008)
The importance of a diverse resource base to competitiveness of firms has been emphasized in resource-based view (RBV) literature and empirical studies done on various industries. Despite this emphasis, resource assessment methodologies within the RBV framework have been seldom approached, and the relative importance of different resources for business operations is not well understood. The data of the study were collected among large- and medium-sized sawmills within the Finnish forest industry. The objective of this study was to assess within the RBV framework the importance of tangible and intangible resources in business operations of sawmills. This was accomplished by introducing a multicriteria decision analysis (MCDA) method suitable for practical resource assessment. According to the results, personnel, managerial, raw material, and financial resources were the most crucial for sawmills. In the future, applying the MCDA to resource assessments could be combined, e.g., with a financial statement analysis to evaluate the effects of resource usage decisions on business performance.

Estimation of Genetic-Gain Multipliers for Modeling Douglas-Fir Height and Diameter Growth - Peter Gould; Randy Johnson; David Marshall; Greg Johnson (Forest Science, 2008)
Methods were developed to calculate genetic-gain multipliers for use in individual-tree models that predict periodic height and diameter growth of coast Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) in the Pacific Northwest. Genetic-gain multipliers are used in growth models that are typically based on extensive measurements of unimproved or “woods-run” stands, to adjust for the increased growth of stands generated from improved seedlots. First-generation progeny test data from multiple breeding zones in the Northwest Tree Improvement Cooperative were used. Data sets included initial heights and diameters and 5-year growth increments for 10- and 15-year-old trees that were identified by open-pollinated families. Nonlinear mixed-effect models were initially developed to predict the average growth of trees in all families, which, taken together, represented woods-run populations. Phenotypic differences in growth rates were then calculated at the family level. Differences among families in height and diameter growth rates were examined using methods from quantitative genetics and raw phenotypic values. Because gain in total height and diameter at age 10 years is currently the most widely available genetic information for improved Douglas-fir, equations were developed to predict genetic-gain multipliers from family breeding values for these traits. A verification procedure illustrated how incorporating multipliers in growth projections could reduce the mean-square error of predicted growth of selected families.

Regression Estimation Following the Square-Root Transformation of the Response - Timothy G. Gregoire; Qi Feng Lin; Johnathan Boudreau; Ross Nelson (Forest Science, 2008)
In a variety of regression situations, there is interest in predicting the value of Y2, yet it is useful to model it using a square root transformation, such that Y rather than Y2 is regressed on one or more covariates. The back-transformation bias of the square root transformation of the response variable of interest is presented in detail. An unbiased estimator is presented: . Its performance is compared against that of two biased estimators: and . The first two moments of these estimators are derived analytically and verified by means of a simulation study. Both biased estimators have lower mean square errors than the unbiased estimator. An example wherein aboveground biomass is the response variable is presented for illustration.

Combining Tree- and Stand-Level Models: A New Approach to Growth Prediction - Chaofang Yue; Ulrich Kohnle; Sebastian Hein (Forest Science, 2008)
Approaches to combining information generated from different models are recognized for improving forecast quality. However, such an approach has not been developed for forest growth predictions. Therefore, a study was carried out to investigate the potential of combining models to forecast forest growth. A growth prediction system was developed for Norway spruce (Picea abies [L.] Karst.) by combining growth information generated from tree- and stand-level growth models parameterized from an identical data source. The tree-level model predicts relative tree diameter growth rates of a cumulative diameter distribution. The stand-level models predict absolute stand basal area growth. The combined prediction system consists of three basic steps: preliminary prediction, combination, and feedback modification. Preliminary predictions of stand basal area growth are generated annually from both types of growth models. The preliminary predictions are then combined on the basis of a variance and covariance method, and the combined estimator is used to update the growth models in a feedback procedure. In the tree-level growth model, the updated stand basal area is subsequently disaggregated to individual trees. On the basis of a validation data set, forecasts of stand basal area with the combined prediction system were shown to gain in efficiency from 14 to 43% compared with forecasts with the tree-level model alone and from 4 to 16% compared with projections with the stand-level model, depending on the length of the projection (5–30 years).

Drought-Induced Changes in C and N Stoichiometry in a Quercus ilex Mediterranean Forest - Jordi Sardans; Josep Peñuelas; Romà Ogaya (Forest Science, 2008)
A 6-year field experiment of drought manipulation was performed in a Mediterranean forest with the aim of determining the effects of the drought predicted by most climate and ecophysiological models on the C and N concentration, accumulation, and stoichiometry in plants and soil. Drought had different effects among dominant species. In Quercus ilex, it increased the C/P ratio in wood and roots, N concentrations in roots and litter, and N/P ratio in wood and roots and decreased the C concentration in roots, C/N ratio in roots and litter, and C/P ratio in litter. In Arbutus unedo, drought increased the N concentration in litter and decreased the N concentration in leaves, thus decreasing N leaf reabsorption. No significant changes in C and N concentrations were found in Phillyrea latifolia. Drought affected the P plant absorption capacity more than that of N (more mobile). There was a general decreasing trend of C and N accumulation in aboveground biomass, with this effect being significant in A. unedo, which accumulated 80% less C and lost 2 kg ha−1 of N in aboveground biomass in drought plots in the period 1999–2005, whereas in this same period it accumulated 9 kg ha−1 of N in total aboveground biomass in control plots. Total soil N and soil organic C increased in droughted soils. The effects of drought on C/N/P stoichiometry and N uptake capacity were different among the three dominant plant species. Q. ilex and A. unedo were more sensitive to drought than P. latifolia. The increase in C/P and N/P ratios in Q. ilex and the decrease in N uptake in A. unedo might decrease their competitive capacity under drought by decreasing water use efficiency. These results altogether indicated slower C and N mineralization and lower N plant capture, N leaf reabsorption, and N accumulation in some dominant plant species in response to drought, thus reducing C and N soil turnover, increasing C and N accumulation in soil, and reducing C and N at the stand level.

Estimating Land Rent from the Market Value of Timberland - Shiv N. Mehrotra; Douglas R. Carter; Janaki Alavalapati (Forest Science, 2008)
Modeling empirical investment behavior of timber stand decision makers requires the use of market-generated information. Recent forestry literature has suggested that the available information on market valuations of timberland could be used to estimate empirical timberland rents as the opportunity cost. In this article we point out the fact that the market value of timberland comprises of the value of current market rent as well as values of speculated future market rents. We argue the importance of accounting for the values of speculated future rents, which could differ widely from the value of the current market rent.

Seed Viability and Dispersal of the Wind-Dispersed Invasive Ailanthus altissima in Aqueous Environments - Matthew A. Kaproth; James B. McGraw (Forest Science, 2008)
In mesic forest environments, seeds of wind-dispersed plant species may frequently be deposited in aqueous environments (e.g., lakes and rivers). The consequences of deposition in an aqueous medium depend on whether seed viability is maintained. If seeds survive there, secondary dispersal in water may transport seeds long distances to suitable habitats. Using the exotic species, tree-of-heaven (Ailanthus altissima [Mill.] Swingle), in this study we estimated seed dispersal into water as a function of distance and experimentally tested seed buoyancy, secondary dispersal, and germinability after dispersal in water and on land. We found that biologically significant numbers of seeds disperse directly into water, remain buoyant, and are transported long distances by water. Germination rates for seeds that were kept in aqueous environments (Cheat Lake and the Monongahela River, near Morgantown, WV) were found to be similar to or higher than those in nearby terrestrial controls (F = 10.94, P = 0.0057). Seeds kept in aqueous environments retained high germination rates (94.4 ± 1.1%) even after 5 months. Although A. altissima may not disperse primarily through water environments, this study suggests that secondary dispersal by water is possible and may allow for long-distance dispersal more than two orders of magnitude farther than recorded primary dispersal.

Simulating Light Availability under Different Hybrid Poplar Clones in a Mixed Intensive Plantation System - Alain Paquette; Christian Messier; Pierre Périnet; Alain Cogliastro (Forest Science, 2008)
Fast-growing hybrid poplars have been proposed as a means of achieving restoration objectives on former agricultural land by providing shelter for slower-growing species. Intensive two-stage scenarios of mixed plantations are also possible using valuable hardwoods interplanted among hybrid poplars. The latter would be harvested at maturity (approximately 20 years) once their protective role has been accomplished, leaving more space for the full development of the second cohort. We implemented simulations of hybrid poplar growth in the SORTIE-ND model and used it to test scenarios with clones varying in growth and crown allometry, different hardwood species, and spatial arrangements, to maximize production of both groups. Important differences in growth and allometry were manifested among clones over time, which translated into important differences in available light between rows. Sustained growth for most hardwoods appeared optimal using wider spacings of 16 m, compared with 12 m, between poplar rows. To our knowledge, this is the first attempt to integrate fast-growing hybrids and intensive silviculture scenarios into spatially explicit models. These models are necessary support tools for the efforts now being invested in intensive silviculture in the face of diminishing forest resources, increasing wood and fiber demands, and climate change.

Emulating Natural Forest Landscape Disturbances: Concepts and Applications (Forest Science, 2008)

Realizing Community Futures: A Practical Guide to Harnessing Natural Resources (Forest Science, 2008)

Silviculture and Ecology of Western U.S. Forests (Forest Science, 2008)

Sparse Bayesian Estimation of Forest Stand Characteristics from Airborne Laser Scanning - Virpi Junttila; Matti Maltamo; Tuomo Kauranne (Forest Science, 2008)
In this article, a new method is applied to modeling forest stand characteristics from airborne laser scanning measurements. The method is an alternative to the cross-validation procedure of variable selection used in the ordinary least-squares (OLS) method and seemingly unrelated regression (SUR) with automatic selection of the features used in the model. This method is called the sparse Bayesian method. It does not suffer from overfitting thanks to the Bayesian formulation of the problem. The proposed method is applied to sample plot data obtained from inventory by compartments. The results show that the sparse Bayesian method performs as well as OLS and SUR methods, in terms of accuracy of total stand characteristics. The methods are comparable also in their demand for sample plot data. None of the methods lose much of their accuracy, even when just a few dozen sample plots are available. A Bayesian approach makes it possible to automate model formulation and sample plot selection processes. It is therefore possible to automatically generate a different model for intrastand strata, thus addressing intrastand variability. The proposed method automatically maintains a balance between the number of forest parameters and the rank of the model used to estimate them.

Effects of Microsites Created by Selective Harvesting on Growth of Microstegium vimineum in a Central Hardwood Forest - Jordan M. Marshall; David S. Buckley (Forest Science, 2008)
Disturbances related to silvicultural activities are inevitable and may facilitate the spread of established populations of exotic species. Microstegium vimineum is an annual exotic grass that has spread throughout the eastern United States. Different categories of understory microsites resulting from cutting and the operation of logging machines within three selective harvest units were identified and characterized by measuring several environmental variables. M. vimineum was sown within the microsites categorized. Differences in growth of M. vimineum across different microsites were quantified. As percent canopy cover increased, M. vimineum percent cover, mean length, and mean number of nodes decreased. Also, as litter depth increased, M. vimineum percent cover and stem length decreased. In undisturbed microsites in which M. vimineum was not sown, the exotic grass was not a dominant species, whereas in all other microsites created by logging machine operation M. vimineum was a dominant species whether those areas were sown or colonized by wild populations. These results suggest that unique microsites created by logging may facilitate M. vimineum invasion of central hardwood forests. The apparent connection between soil and canopy disturbance and invasion by M. vimineum provides further impetus for careful planning and use of haul roads and skid trails.

Forest Hydrology: An Introduction to Water and Forests (2nd Edition) (Forest Science, 2008)

Using the Space-Time Permutation Scan Statistic to Map Anomalous Diameter Distributions Drawn from Landscape-Scale Forest Inventories - Benjamin Rubin; David MacFarlane (Forest Science, 2008)
Landscape-scale tree stem diameter distributions contain information that is potentially useful for evaluating the structural sustainability of forests, describing the impacts of past disturbances, and predicting future forest structure. One obstacle to interpreting diameter distributions at large scales is that typical boundaries used to define populations, such as ecoregions or counties, may not correspond to areas with different diameter distributions. We modified the space-time permutation scan statistic (STPSS), a disease outbreak detection technique, to identify and map areas in Pennsylvania, USA, where diameter distributions based on Forest Inventory and Analysis plots appeared different from the diameter distributions of the state as a whole. We used linear, exponential, and polynomial regressions to model the diameter distributions of the entire state and of areas indicated by the STPSS. The best fit regression models were linear and polynomial as determined by Akaike's information criterion and log likelihood statistics. Regression models confirmed that the STPSS identified areas where the diameter distributions of all species, oaks, and red maple differed from their corresponding statewide populations. Through a nested application of the STPSS at successively smaller spatial scales, we mapped core zones within each area where the difference was greatest.

Spatial Scale and Stand Structure in Northern Hardwood Forests: Implications for Quantifying Diameter Distributions - Maria K. Janowiak; Linda M. Nagel; Christopher R. Webster (Forest Science, 2008)
Diameter distributions are frequently used to describe northern hardwood stand structure and serve as a structural guide for management. Several diameter distribution shapes have been found in managed and unmanaged uneven-aged northern hardwood stands, and it is unclear which patterns are due primarily to natural processes that could be self-perpetuating versus patterns that may be transient or aberrant. Variability in research methods has clouded consistent interpretation of resulting distributions. In this study, we evaluated northern hardwood stands in Michigan to determine how management and sample area affect interpretation of diameter distribution shape. Managed stands had a higher degree of variability in distribution shape and a tendency toward the increasing-q pattern. Unmanaged uneven-aged stands (i.e., old-growth remnants) were predominantly rotated sigmoid in shape. Patterns for each type of management became more consistent as sample area increased. Our data suggest a minimum sample area of 13% of total stand area may be needed to accurately capture diameter distribution shape; in this study that was 0.4 ha of a 3.2-ha sample plot. Additionally, greater heterogeneity in the structure of unmanaged stands resulted in the need for larger sample areas compared with that for managed stands.

Estimating Area of Forest Change by Random Sampling of Change Strata Mapped Using Satellite Imagery - John R. Dymond; James D. Shepherd; Greg C. Arnold; Craig M. Trotter (Forest Science, 2008)
There is worldwide interest in monitoring changes in forest area for carbon budgeting and assessing biodiversity changes. For cost-effective monitoring over large areas, automated mapping is necessary. However, the accuracy of automated mapping is rarely high enough to permit accurate estimation of changes in forest area when there is small change. In this article, we show how accurate area statistics of small change can be achieved by combining automated change mapping with stratified random sampling. The stratified random sampling can be made efficient by exhaustive sampling of a stratum with contiguous areas of apparent change greater than or equal to some lower limit (5 ha in the case presented here) and splitting the forest-to-forest stratum into large and small spectral change. Efficiency of the method is high when the exhaustively sampled stratum contains a high proportion of all real change. A regional example from New Zealand of mapping change in forest area is given. Acceptable accuracy (afforestation is estimated to ±7% of reported afforestation) from acceptable effort (10,702 sample points) is obtained, representing an efficiency gain of 78% (in terms of sample size) over simple random sampling. The method can be applied to national estimation of forest change to the same accuracy with an efficiency gain of approximately 70%. It provides a more rapid alternative to multipurpose forest inventories, which depend on intensive and expensive field data, and has significant implications for carbon accounting at regional and national scales, where rapid production of usable estimates are required for carbon exchange markets.

A Gamma-Poisson Distribution of Point to k Nearest Event Distance - Steen Magnussen; Nicholas Picard; Christoph Kleinn (Forest Science, 2008)
Distance sampling of events in natural or seminatural populations often indicates a larger variance in the distance to the kth nearest event than expected for events distributed completely at random. Overdispersion contributes to the well-known bias problem of distance sampling density estimators. Distance distribution models that accommodate overdispersion in the data should lead to more robust estimators of density. To this end we propose a gamma-Poisson distribution model for distances from a point to k nearest events. The model assumes a gamma distribution of local densities of randomly distributed events. Properties of the distribution and estimation of the parameters and event density are detailed for both constrained and unconstrained sampling. Four examples, one with simulated data from a known negative binomial distribution and three with simulated distance sampling in natural and seminatural stem-mapped tree stands, illustrate the promising performance of this new distribution, both as a model for distances and for density estimation. The modeling approach extends to other mixing distributions.

Economic and Ecological Effects of Diameter Caps: A Markov Decision Model for Douglas-Fir/Western Hemlock Forests - Mo Zhou; Joseph Buongiorno; Jingjing Liang (Forest Science, 2008)
We evaluated some of the effects of not harvesting trees of 41 cm (16 in.) dbh or larger with uneven-aged management of Douglas-fir/western hemlock forests. The opportunity cost of diameter caps was measured by the difference in maximum expected net present value (NPV) or equivalent annual timber income, with or without diameter caps. For the two policies, Markov decision models were used to determine the best decision rules and their effects on the NPV, the forest area with late-seral structure, and the forest area with northern spotted owl nesting habitat structure. The opportunity cost of diameter caps was computed for 64 initial stand states defined by basal area of small, medium, or large trees of shade-intolerant species (mostly Douglas-fir) or shade-tolerant species (mostly western hemlock). The opportunity cost fell in four distinct quartiles. The 16 stand states with high basal area in large shade-intolerant and large shade-tolerant trees had the highest opportunity cost ($798–$816 ha−1year−1 or 58–76%, expected over an infinite horizon), whereas the 16 stand states with low basal area in large shade-intolerant and large shade-tolerant trees had the lowest ($59–$89 ha−1year−1 or 11–13%). The diameter caps policy increased considerably the expected area of forest with late-seral structure, over an infinite time horizon, and the expected area with spotted owl nesting habitat structure, compared with their current levels in the study region.

Suppression Cost Forecasts in Advance of Wildfire Seasons - Jeffrey P. Prestemon; Karen Abt; Krista Gebert (Forest Science, 2008)
Approaches for forecasting wildfire suppression costs in advance of a wildfire season are demonstrated for two lead times: fall and spring of the current fiscal year (Oct. 1–Sept. 30). Model functional forms are derived from aggregate expressions of a least cost plus net value change model. Empirical estimates of these models are used to generate advance-of-season forecasts. Cost forecasts involve estimation of suppression cost equations by geographical region based on a time series of historical data (1977–2006) of costs, a time trend, and climate variables, forecasts of the next season's suppression costs, by region and in total across all regions, and generation of suppression cost forecast probability distributions by region and in aggregate. The forecasts are also evaluated historically for their goodness of fit using cross-validation techniques. The two lead time forecast models are compared with the 10-year moving average of suppression costs, currently used as a budget request formula by the US Forest Service. Results show that the spring forecast of suppression costs is statistically no better than the fall forecast for predicting the coming season's costs. However, both the spring and fall forecasts significantly outperform the 10-year moving average, reducing forecast errors by approximately 60%.

Thinning Effects on Microbial Biomass, N Mineralization, and Tree Growth in a Mid-Rotation Fire-Origin Lodgepole Pine Stand in the Lower Foothills of Alberta, Canada - Xiao Tan; Scott X. Chang; Philip G. Comeau; Yonghe Wang (Forest Science, 2008)
We examined the effects of precommercial thinning on microbial biomass C and N, rates of microbial respiration and net N mineralization, and tree growth 24 years after thinning of a 22-year-old fire-origin lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.) stand near Edson, Alberta. Treatments were control (unthinned) and manual-thinned (even spacing) to 1,600 trees ha−1 with thinning residue removed. Forest floor and mineral soil (0–10 and 10–20 cm) were sampled on June 15, July 26, and September 25 of the 2002 growing season for the analyses of soil chemical and biological properties, with the last set of incubated samples for determining net N mineralization rates retrieved on May 23, 2003. Forest floor mass was 16 Mg ha−1 lower in the thinned (59 Mg ha−1) than in the unthinned (75 Mg ha−1) plots. Soil moisture content in the forest floor and net N mineralization rates and available N in the mineral soil on most of the sampling dates were higher in the thinned than in the control plots. In the thinned plots, basal area and relative density were 27.7 m2 ha−1 and 54, respectively, and these were still significantly lower than values in the unthinned plots 24 years after treatment. Current annual diameter increment of the largest 1,000 trees ha−1 was greater in the thinned than in the unthinned plots in 2002–2003. Diameter growth was positively correlated with net N mineralization and soil available N. In this stand, thinning still influenced N availability and soil processes with the trees continuing to respond 24 years after thinning.

An Alternative View of Continuous Forest Inventories - Francis A. Roesch (Forest Science, 2008)
A generalized three-dimensional concept of continuous forest inventories applicable to all common forest sample designs is presented and discussed. The concept recognizes the forest through time as a three-dimensional population, two dimensions in land area and the third in time. The sample is selected from a finite three-dimensional partitioning of the population. The partitioning is analogous to carving the volume into pieces like a three-dimensional jigsaw puzzle. Each puzzle piece is defined by the selection volumes of observation sets on the individual trees existing in the forest during the period of interest. The concept is a temporal extension of an alternative view of forest sampling offered in Roesch et al. (1993, Sur. Methods 19(2):199–204) and results in a finite number of independently selected three-dimensional sample units.

Adjacency Branches Used To Optimize Forest Harvesting Subject to Area Restrictions on Clearfell - Alastair J. McNaughton; David Ryan (Forest Science, 2008)
Consider a forest containing units of various sizes for which a maximum clearfell area has been specified along with an associated green-up time period. For such an application it is customary to use adjacency constraints to produce a harvesting plan. These constraints control the availability for harvest of specific units relative to the harvesting of certain adjacent units. However, such constraints are difficult to formulate and often precipitate major difficulties in the implementation of the solution algorithm. A new concept, a nuclear set, is introduced. This concept allows the unit-specific aspects of the problem to be analyzed in an insightful manner. Any adjacency violation can be detected in relation to these nuclear sets. Suitable adjacency branches can be implemented to remove these violations. The form of these branches derives from the same nuclear sets. A remarkably small number of these branches are required to obtain a feasible solution. These ideas are incorporated into a column generation and constraint generation model. This new forest harvesting model solves the clearfell area restriction problem in an exact sense. Results are included for numerical trials involving simulated data representing moderately sized applications with a planning horizon of up to one rotation. The output from these trials suggests that this algorithm is suitable for large commercial applications. Several applications of 1,600 units are solved over 25 time periods with multiple green-up.

Protect Thy Neighbor: Investigating the Spatial Externalities of Community Wildfire Hazard Mitigation - David Butry; Geoffrey Donovan (Forest Science, 2008)
Climate change, increased wildland fuels, and residential development patterns in fire-prone areas all combine to make wildfire risk mitigation an important public policy issue. One approach to wildfire risk mitigation is to encourage homeowners to use fire-resistant building materials and to create defensible spaces around their homes. We develop a theoretical model of interdependent household wildfire risk and mathematically introduce two new concepts of the benefits accruing from hazard mitigation: direct and spillover (indirect) damage averted. We explore how firewise communities can best spend and position mitigation resources to maximize the sum of direct and spillover damage averted. Simulating wildfire behavior within a fire-prone community, our results indicate that homeowners' wildfire risk reduction actions can have significant, positive spillover effects on the wildfire risk of neighboring houses. In such cases, individual homeowners may engage in inefficient levels of wildfire risk mitigation when viewed from the community perspective. We use a simulation approach to demonstrate that wildfire risk reduction is most effective when concentrated in houses at the interface of communities and wildlands.

Tradeoffs in Overstory and Understory Aboveground Net Primary Productivity in Southwestern Ponderosa Pine Stands - Kyla E. Sabo; Stephen C. Hart; Carolyn Hull Sieg; John Duff Bailey (Forest Science, 2008)
Previous studies in ponderosa pine forests have quantified the relationship between overstory stand characteristics and understory production using tree measurements such as basal area. We built on these past studies by evaluating the tradeoff between overstory and understory aboveground net primary productivity (ANPP) in southwestern ponderosa pine forests at the landscape level and over a gradient of stand structural types and burn histories. We measured overstory and understory attributes in 2004 and 2005 in four stand structural types (unmanaged, thinned, thinned and burned, and low basal area thinned and burned) relative to a stand-replacing wildfire site. Thinning alone and with prescribed burning reduced stand-level wood and total tree production relative to unmanaged stands. Understory (herbaceous) ANPP was highest in wildfire stands and low basal area thinned and burned plots but did not differ among the other stand structural types, apparently because of high residual basal area and relatively uniform tree spacing. Contemporary ponderosa pine forests are low productivity ecosystems that exhibit a threshold response between reductions in tree density and increases in understory production at 5.9 m2 ha. We calculated the slope of the relationship between tree and herbaceous ANPP to be −0.14, which was lower than the values we estimated from other, more productive savanna ecosystems. Our results suggest that to maintain more fire-resistant and hence sustainable southwestern ponderosa pine ecosystems, tree densities need to be substantially reduced from contemporary levels. Large, landscape-level reductions in tree density will decrease total ecosystem production of this forest type, but this reduction will probably be small relative to ecosystem production losses after widespread, stand-replacing wildfires.

Tests of a Dynamic Programming-Based Heuristic for Scheduling Forest Core Area Production over Large Landscapes - Yu Wei; Howard M. Hoganson (Forest Science, 2008)
Potential simplifying assumptions are presented and tested for applying a heuristic model to schedule production of core area of older forest for the Chippewa National Forest in Minnesota, recognizing approximately 67,000 analysis units and 10 10-year planning periods. The model has strong ties to optimization modeling, utilizing dynamic programming to solve overlapping and linked subproblems. Emphasis of this research is on understanding tradeoffs between solution time and nearness to optimality when large landscapes are modeled. Results show that combinations of model-simplifying assumptions can help maintain an efficient balance between computation time and model optimality. Results are sensitive to values assumed for core area, suggesting that more spatial detail is recognized with higher core area values. Results are compared along an efficiency frontier, where improvements in either computation time or management schedule value cannot be achieved without a loss in the other. Understanding the tradeoff between optimality and computation efficiency is important for model use within a larger iterative system that integrates spatial values with aspatial, forestwide management constraints.

A Geographically Weighted Regression Analysis of Douglas-Fir Site Index in North Central Idaho - Mark J. Kimsey; James Moore; Paul McDaniel (Forest Science, 2008)
An analysis of Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco var. glauca) site index (SI) was performed in north central Idaho using two forms of linear regression: standard multiple linear regression (MLR) and geographically weighted regression (GWR). The hypothesis was that the GWR model would provide better estimates of SI using edaphic, topographic, and climatic predictor variables than ordinary MLR. Elevation, volcanic ash depth, slope, and aspect were significantly correlated with Douglas-fir SI (R A 2 = 0.5). GWR accounted for an additional 29% of the variation in SI and reduced the error sum of squares by approximately 53%. The geographically weighted parameter estimates of the model intercept and elevation were nonstationary, which indicates that geographic location determines the influence of a variable on SI. Residual analysis from a MLR model showed large SI prediction error throughout the study area. This prediction error was significantly reduced using the GWR model. GWR shows promise for biological modeling.

Problems of Scaling Plantation Plot Diameter Distributions to Stand Level - Bruce E. Borders; Mingliang Wang; Dehai Zhao (Forest Science, 2008)
Diameter distribution models are used extensively in forest growth and yield modeling. They are usually fitted with fixed area sample plot data but applied at the stand level, the unit of forest production planning. In this process, the distribution obtained at the plot level is assumed to be representative of that at the stand level. In other words, the distribution from each plot of the same stand is assumed (roughly) to be the same, and therefore we can reasonably scale the plot distribution to the stand level. However, because of site-induced within-stand (between-plot) variability and spatial correlation introduced by tree competition and/or microsite effects or other factors, plot distributions may differ markedly from the stand distribution. We use data from 11 slash pine (Pinus elliottii) plantations, each consisting of 10 plots, to address differences in diameter distributions between plot level and stand level. The data indicate that (single) plot distributions are generally significantly different from their stand counterparts, because of spatial heterogeneity among plots within a given stand. For relatively homogeneous stands, diameter distributions obtained by averaging two to three plots may well represent the stand distribution within a certain precision, whereas for stands with more obvious spatial heterogeneity, a relatively large number of plots seem to be necessary for characterizing the stand distribution.

Changes in Forest Structure After a Large, Mixed-Severity Wildfire in Ponderosa Pine Forests of the Black Hills, South Dakota, USA - Tara L. Keyser; Leigh B. Lentile; Frederick W. Smith; Wayne D. Shepperd (Forest Science, 2008)
We evaluated changes in forest structure related to fire severity after a wildfire in ponderosa pine forests of the Black Hills, South Dakota, where 25% burned at low, 48% at moderate, and 27% at high severity. We compared tree mortality, fine (FWD) and coarse woody debris (CWD) and tree regeneration in areas burned under different severity. With low severity, mortality was limited to small trees (<15 cm dbh) with no reduction in basal area (BA) compared with unburned areas. FWD and CWD were 60% less than the unburned forest. With moderate severity, 100% mortality of small trees and significant large tree mortality resulted in an 50% reduction in BA and an open stand structure dominated by a few large trees. After 5 years, FWD and CWD recovered to unburned levels. With high severity, a lack of seed source makes regeneration unlikely. After 5 years, FWD equaled levels in unburned stands and CWD loads exceeded the unburned forest by 74%. The future landscape will be a mosaic of patches with forest structures determined by developmental trajectories set in motion by different fire severities. There will be patches of fully stocked, single canopy forest, multistory forest, and persistent grass- and shrub-dominated communities. High fuel loads in moderate and high severity areas remain a concern for management as does the lack of regeneration in high severity areas.

How (Un)Certain Is the Future in Forestry? A Comparative Assessment of Uncertainty in the Forest and Agricultural Sector - Marjanke A. Hoogstra; Heiner Schanz (Forest Science, 2008)
Several authors have stated that, because of the long time horizons underlying forestry processes, the forest sector encounters far more uncertainty than is experienced by any other industrial or agricultural production processes, especially regarding the long future. To gain more insight into the extent to which foresters experience uncertainty in their work field, a content analysis has been carried out to reveal how foresters from the United States and (Germanic) Central Europe (Germany, Austria, and Switzerland) experience uncertainty. The outcomes were compared with the experiences of uncertainty in a more short-term oriented sector, namely the agricultural sector (also in the United States and in Central Europe). Although the findings must be interpreted carefully, the research reveals that, in contrast to what was expected, foresters experience the future as the most certain time period. Decisionmakers in forestry, as in other business sectors, seem to ignore the uncertainty and pretend that the future is certain. This strategy implies considerable risk and, therefore, for forest management to be effective, there is no other way than actively confronting the futurity dilemma.

Generalized Algebraic Difference Approach Derivation of Dynamic Site Equations with Polymorphism and Variable Asymptotes from Exponential and Logarithmic Functions - Chris J. Cieszewski; Mike Strub (Forest Science, 2008)
The generalized algebraic difference approach (GADA) uses both: two-dimensional functions of explicit time and two-dimensional functions of explicit site to derive a single dynamic equation that is a three-dimensional function of explicit time and implicit site. In 2004 Cieszewski advanced dynamic site equations with polymorphism, and variable asymptotes (Cieszewski, C.J. 2004. GADA derivation of dynamic site equations with polymorphism and variable asymptotes from Richards, Weibull, and other exponential functions. PMRC Tech. Rep. 2004-5, p. 16.) were built with GADA using one general function of time T and two general functions of site X. The function of time is the exponential function Y = MTb , and the functions of site are the quadratic function Z = b1 + b2X + b3X 2 and the inverse half-saturation function Z = b1 + b2/(X + b3). We discuss the new dynamic equations based on five exponential substitutions (Richards, Gompertz, Korf, logistic, and log-logistic) and one new logarithmic model substitution in the exponential function of time and 10 special cases of the two functions of site corresponding to their different parameter values. The new dynamic equations presented offer breakthrough flexibility in modeling of the self-referencing dynamics with the exponential and logarithmic functions considered in this article.

Spatial Pattern of Coast Redwood in Three Alluvial Flat Old-Growth Forests in Northern California - Christa M. Dagley (Forest Science, 2008)
The spatial patterns of trees were investigated in old-growth redwood (Sequoia sempervirens [D. Don] Endl.) forests located in northern California to guide the design of restoration prescriptions. All stems ≥15 cm dbh were mapped and measured on three 1.5-ha plots. Patterns for trees in different size classes were analyzed separately with Ripley's K(d) function. Results revealed two patterns. At two sites, trees were randomly distributed throughout the stand and size classes were spatially independent of each other at scales of 0–50 m. At one site, a clumped spatial pattern was revealed for small- and medium-sized tree groups at small scales, whereas a random spatial pattern was detected for large trees at scales of 0–50 m. In addition, significant positive deviation from spatial independence at small scales suggested an attraction between tree groups. The spatial pattern of regeneration (trees <15 cm dbh) was described using quadrat-based analyses. Regeneration was clumped at all three sites. Results indicate that old-growth redwood forests occurring on alluvial flats have different spatial patterns for similar size classes of trees despite the similarities in topography and stand structural characteristics. For land managers interested in restoration, these results suggest that past thinning guides that emphasized uniform spacing may not be appropriate in restoration efforts. Instead, trees should be retained in clumps or in random spatial patterns.

Spatial Dynamics of Natural Regeneration in Two Differently Managed Pinus sylvestris Stands before and after Silvicultural Intervention Using Replicated Spatial Point Patterns - Marta Pardos; Fernando Montes; Isabel Cañellas (Forest Science, 2008)
Individual seedlings were mapped on eight 5 m × 5 m plots between 2003 and 2006, in two differently managed Pinus sylvestris forests in Spain (group shelterwood system in Valsaín forest versus uniform system followed by soil preparation in Navafría forest). The spatial pattern of the seedlings was analyzed through the L(d) function. The spatial relationship between seedlings before and after the regeneration felling was analyzed using the intertype Lrs (d) function. To study the spatial relationship between seedling distribution and either light availability or organic matter depth, the Krx (d) function was used. A practical method is proposed for obtaining the group-specific mean for several replicates: L std(d), based on the standardization of the L(d) function by the quantile bounds of the null model, which, once attained, is compared with the sum, weighted by the number of points in each replicate. Both the Lstd(d) group means and the point number weighted mean showed a cluster pattern for seedlings from germination to 6 years old, peaking at short scales (15–100 cm), before and after the cutting. After the cutting, the co-occurrence between germinants and older seedlings was not significant, although the Lrs (d) function was positive and presented a peak (50–100 cm). Seedling emergence was positively associated with organic matter depth after the cutting. The association between seedling distribution and light was modified when the cutting was severe (>60% of tree basal area).

Bivariate Distribution Modeling of Tree Diameters and Heights: Dependency Modeling Using Copulas - Mingliang Wang; Keith Rennolls; Shouzheng Tang (Forest Science, 2008)
Models of diameter and height distributions play an important role in forest mensuration and inventory, and many models and fitting methods are available for fitting these distributions separately. Very few models and methods appropriate for fitting the joint distribution of diameters and heights are available. The S BB and distributions obtained using Plackett's method are the only appropriate models published in the forestry literature to date. A bivariate joint distribution can be represented in terms of its underlying marginals and a copula function that models the dependency structure. A copula is a function that joins or “couples” a multivariate distribution function to its one-dimensional marginal distributions. The copula approach provides a general way of constructing bivariate distributions, including previously used bivariate models. The basics of the copula representation, the most useful copula functions, and maximum likelihood estimation (MLE) of the copula function are introduced. The emphasis of this article is on the choice of copula function(s) appropriate for modeling the joint distribution of tree diameters and heights. Using an empirical dataset of 102 Chinese fir (Cunninghamia lanceolata Lamb.) plantation plots, we fit each of the copula functions that we considered to each sample-plot joint distribution of tree diameters and heights. A two-stage MLE approach with a nonparametric (empirical) approach to the marginal distributions is adopted. In this case study the normal copula proves to be the best for modeling the joint distribution (dependence) of tree diameters and heights.

Ecological and Economic Determinants of Invasive Tree Species on Alabama Forestland - Anwar Hussain; Changyou Sun; Xiaoping Zhou; Ian A. Munn (Forest Science, 2008)
The spread of invasive tree species has caused increasing harm to the environment. This study was motivated by the considerations that earlier studies generally ignored the role of economic factors related to the occurrence and abundance of invasive species, and empirical analyses of invasive trees on forestland have been inadequate. We assessed the impact of ecological and economic factors on the occurrence and number of invasive tree species on Alabama forestland since 1990. Count data models were used to analyze the 2004 Alabama Forest Inventory Analysis (FIA) data. The proportion of FIA plots with invasive species was 1.06% in 1990, 1.24% in 2000, and 1.35% in 2004. Occurrence of invasive trees on a plot depended on forest type (e.g., natural pines, planted pines, or oak-pines). Plots with planted pine were 171% less likely to be infested with invasive trees than otherwise similar plots. Number of invasive trees per plot was determined by a wide variety of factors, including site productivity, growing stock, stand age, ecoregion, plot proximity to metropolitan centers, ownership type, and forest management activity. The magnitude of the impact was especially large for the ownership type, with more invasive trees on private forestlands than on public lands. These findings suggest that both ecological and economic factors need to be considered in the prevention and control of invasive species invasion.

An Integrated Approach to Evaluating the Economic Costs of Wildfire Hazard Reduction through Wood Utilization Opportunities in the Southwestern United States - Eini C. Lowell; Dennis R. Becker; Robert Rummer; Debra Larson; Linda Wadleigh (Forest Science, 2008)
This research provides an important step in the conceptualization and development of an integrated wildfire fuels reduction system from silvicultural prescription, through stem selection, harvesting, in-woods processing, transport, and market selection. Decisions made at each functional step are informed by knowledge about subsequent functions. Data on the resource characteristics of small-diameter ponderosa pine (Pinus ponderosa Dougl. ex Laws.), harvest equipment productivity, lumber recovery, and net profit (loss) by level of fuels reduction achieved were collected from four 8.1-ha (20 ac) sites in northern Arizona. These data were used to develop a Windows-based, financial and engineering software program, the harvest cost-revenue (HCR) estimator, to identify the economic costs of wildfire fuel reduction treatments that may be used to evaluate cost per acre thresholds for logging contractors, appraise contract bid rates, or assess stumpage values for ponderosa pine stands in the southwestern United States. Application of the model illustrates variability in fuels reduction costs owing to the level of fuels reduction achieved, the volume of merchantable wood removed from different forest stands, and the availability of markets for removed material. Machine productivity helps predict differences in harvest costs but is secondary to market constraints and the volume of wood harvested.

Variation in Mechanical Properties of Selected Young Poplar Hybrid Crosses - Qibin Yu; S.Y. Zhang; Alfas Pliura; John MacKay; Jean Bousquet; Pierre Périnet (Forest Science, 2008)
To better understand the variability in mechanical properties caused by genetic differences in hybrid poplars, modulus of elasticity and modulus of rupture in static bending were examined at two 10-year-old clonal trials located at Windsor and St-Ours, southern Quebec, Canada. The materials consisted of three hybrids, Populus deltoides × Populus nigra, Populus trichocarpa × P. deltoides, Populus maximowiczii × Populus balsamifera, and native P. deltoides. Significant differences were observed in mechanical properties among hybrids and P. deltoides. The effects of growth on the mechanical properties were inconsistent and varied considerably by site and by hybrid. Results indicated no uniform trends relating growth rate to either higher or lower modulus of elasticity/modulus of rupture. It appears that selection for strength properties may not uniformly lead to decreased growth production, especially for P. trichocarpa × P. deltoides and P. maximowiczii × P. balsamifera.

Precision of Total Volume Estimates Resulting from Pseudo-Bayes Estimator for Stock Tables - Edwin J. Green; Michael Clutter (Forest Science, 2008)
In an earlier article we presented a novel estimator for stand tables. The estimator performed much better than the usual estimator in simulation studies. In this article we extend the method to volume estimation, and demonstrate via simulation studies that total volume estimates from the pseudo-Bayes stand table estimator are superior to estimates derived from the usual stand table estimator. We also derive estimates for the variance and mean squared error of the pseudo-Bayes total volume estimator and approximate confidence intervals. The intervals based on the mean squared error have approximately correct coverage and are narrower than the usual confidence intervals.

Seed Germination: Mathematical Representation and Parameters Extraction - Yousry A. El-Kassaby; Ian Moss; Dave Kolotelo; Michael Stoehr (Forest Science, 2008)
A method for mathematically describing cumulative seed germination using the four-parameter Hill function is described. The function's four parameters allowed both direct or indirect biological interpretation of germination behavior and the impact of seed pretreatments on germination improvement. Three parameters, a, b, and c, allowed direct assessment of germination capacity (%), the shape and steepness of the germination course, and germination speed (time to reach 50% germination). The fourth parameter y0 permitted estimation of the lag time (germination onset). The mathematical expression of cumulative seed germination of unstratified and stratified seed made it possible to quantitatively estimate seedlot dormancy and the amount of germination improvement caused by a specific seed pretreatment. This was accomplished by estimating the area between the two cumulative germination curves through integration. The utility of the proposed approach was demonstrated using germination data from wind-pollinated, individual genotypes (half-sib families) of lodgepole pine (Pinus contorta var. latifolia) and bulk seedlots of lodgepole pine and white spruce (Picea glauca).

Stochastic Simulation of Forest Regeneration Establishment Using a Multilevel Multivariate Model - Jari Miina; Jaakko Heinonen (Forest Science, 2008)
Here we present a method for simulating high unexplained variation in establishment of tree seedlings in planted Norway spruce (Picea abies [L.] Karst.) stands. The simulation method is based on an existing hierarchical multilevel multivariate model for establishment of regeneration (Miina, J., and T. Saksa. 2006. New For. 32:265–283). The model includes seven simultaneously estimated models for numbers and heights of tree seedlings on 20-m2 plots within a regeneration area. The variation in plot-level expectations is described by fixed effects and two nested multivariate normal random effects. Conditionally, given the expected values, one of the count variables is underdispersed and four are overdispersed relative to Poisson law. The conditional distributions of the square roots of the height variables are normal. For the conditional joint distribution, the model defines the product-moment cross-correlation matrix, which includes both positive and negative cross-correlations. The first two moments do not, however, uniquely define the marginal distributions of the count variables or the joint distribution of all seven variables. We applied binomial distribution for the underdispersed Poisson variation and negative binomial distribution for the overdispersed Poisson variation. The conditional joint distribution was defined by a multivariate normal copula and the marginal distributions. Despite relatively low cross-correlations among responses, if the cross-correlations among random components of the responses were ignored in stochastic simulations, the amount and costs of precommercial thinning (i.e., cleaning out competing broadleaves) were greatly underestimated. If all random effect components in model parameters were dropped, the error increased markedly.

Characterizing Family Forest Owners: A Cluster Analysis Approach - Indrajit Majumdar; Lawrence Teeter; Brett Butler (Forest Science, 2008)
For policy implementation to promote better stewardship on family forestlands, it is necessary to understand what motivates landowners. This study characterizes family forest owners in Alabama, Georgia, and South Carolina, based on their feelings about forest stewardship and their stated reasons for owning forestland. Multivariate cluster analysis suggests that family forest owners are, in fact, a diverse set of owners who can be grouped into three attitudinal types, namely, multiple-objective, nontimber, and timber. The multiple-objective ownership type was found to be the largest group (49.1% of respondents) with almost half the family forest owners in the sample population belonging to this category. Owners belonging to the timber cluster (29.4%) indicated only timber management and land investment as strong motivating factors behind their forestland ownership, whereas owners belonging to the nontimber cluster (21.5%) value the nonconsumptive uses of their forestland such as aesthetic values, biodiversity, recreation, and privacy.

Parameter Estimation of Base-Age Invariant Site Index Models: Which Data Structure to Use?—Reply - Mingliang Wang; Bruce E. Borders; Dehai Zhao (Forest Science, 2008)

Effect of Centrifugal Forces on Cluster Patterns in the Softwood Lumber Industry of the United States - Francisco X. Aguilar (Forest Science, 2008)
Although previous reports have identified clustering in the secondary wood products industry, there are no previous studies on the factors influencing spatial patterns in the primary wood products sector. This study explores the perceptions of members of the softwood lumber industry in the United States concerning factors driving location and promoting cluster patterns in this particular industry. The analysis builds on the core-periphery framework of New Economic Geography to identify centrifugal and centripetal forces and determines the most salient advantages and disadvantages derived from industry clustering. The most essential location factors are linked to the availability of raw materials and skilled labor. The results of the factor analysis, reinforced by bootstrapping estimation, suggest that centrifugal forces outweigh centripetal forces. Greater dispersive effects of centrifugal forces result in a peripheral primary wood products industry pattern. Clustering of softwood sawmills is perceived as detrimental to this industry segment because it results in higher costs of inputs, congestion, and undesired competition. However, geographical coincidence between primary and secondary wood product manufacturers that fosters collaboration can result in an enhanced competitive industry structure.

Emergy Synthesis of Intensive Eucalyptus Cultivation in São Paolo, Brazil - T.L. Romanelli; M.J. Cohen; M. Milan; M.T. Brown (Forest Science, 2008)
We used environmental accounting to evaluate high-intensity clonal eucalyptus production in São Paolo, Brazil, converting inputs (environmental, material, and labor) to emergy units so ecological efficiency could be compared on a common basis. Input data were compiled under three pH management scenarios (lime, ash, and sludge). The dominant emergy input is environmental work (transpired water, 58% of total emergy), followed by diesel (15%); most purchased emergy is invested during harvest (41.8% of 7-year production totals). Where recycled materials are used for pH amendment (ash or sludge instead of lime), we observe marked improvements in ecological efficiency; lime (raw) yielded the highest unit emergy value (UEV = emergy per unit energy in the product = 9.6E + 03 sej J−1), whereas using sludge and ash (recycled) reduced the UEV to 8.9E + 03 and 8.8E + 03 sej J−1, respectively. The emergy yield ratio was similarly affected, suggesting better ecological return on energy invested. Sensitivity of resource use to other operational modifications (e.g., decreased diesel, labor, or agrochemicals) was small (<3% change). Emergy synthesis permits comparison of sustainability among forest production systems globally. This eucalyptus scheme shows the highest ecological efficiency of analyzed pulp production operations (UEV range = 1.1 to 3.6E + 04 sej J−1) despite high operational intensity.

The Severity of Budworm-Caused Growth Reductions in Balsam Fir/Spruce Stands Varies with the Hardwood Content of Surrounding Forest Landscapes - Elizabeth M. Campbell; David A. MacLean; Yves Bergeron (Forest Science, 2008)
Tree-ring data collected from balsam fir (Abies balsamea [L.] Mill.) in 31 spruce (Picea spp.)/fir-dominated stands in northern New Brunswick were used to evaluate how radial growth reductions during the last spruce budworm (Choristoneura fumiferana Clem.) outbreak (1972–1992) varied according to the hardwood content of surrounding forest landscapes, insecticide spray history and elevation. Stepwise regression analysis was used to build 12 models describing relationships between mean percent growth reduction (i.e., deviation from mean tree growth averaged over the lifespan of all trees in a stand) and the explanatory variables for years when >80% of stands had growth reductions (1976–1978, 1982–1984, 1990, 1991, and 1994) and for three growth reduction periods (1972–1980, 1981–1985, and 1986–1993). The hardwood content of surrounding forest landscapes entered into all significant regression models (P < 0.05), explaining 12–41% of the variance in budworm-caused growth reductions. Differences in growth reductions among stands were greatest during the initial years of the budworm outbreak (1972–1980), particularly in 1976 when mean reductions were 40% in stands with <50% hardwood and content and 20% in stands in which surrounding hardwood content was >50%. Relationships between variation in growth reductions among stands and elevation or insecticide spray history were weak and less consistent than with landscape hardwood content. Our findings suggest that increasing the hardwood content of forest landscapes could help to reduce the impact of outbreaks on timber supplies.

Using Inventory Projections to Evaluate Management Options for the Nontimber Forest Product of Epiphytic Moss - JeriLynn Peck; Howard Hoganson; Patricia Muir; Alan Ek; Lee Frelich (Forest Science, 2008)
Several US national forests have implemented moratoria on harvesting moss in the absence of management plans that can demonstrate long-term sustainability. To fill this gap, harvest schedules are presented for epiphytic moss in northwestern Oregon based on a variation of the classic volume control model. Commercial moss inventory over a 150-year simulation period was estimated as initial inventory plus biomass increment minus mortality and legal harvest. A 50-year exclusion period between harvests was chosen based on the minimum time estimated to replenish moss and to maintain acceptable species richness for the moss and the invertebrate taxa that inhabit it. Mean estimates for the input parameters were used for a “baseline” scenario and the upper and lower 95th percentile confidence intervals for the estimates were used for “optimistic” and “conservative” scenarios describing moss growth and yield estimates. Recent moss harvest permit levels exceed those that would sustain resource yield and biodiversity even under the optimistic scenario. Avoiding resource depletion would require reducing permit levels by 3.5- and 1.4-fold under baseline and optimistic scenarios, respectively. Sustained yield would require reductions of 6.8- and 1.7-fold, respectively.

Using Segmented Regression to Estimate Stages and Phases of Stand Development - Curtis L. VanderSchaaf; Harold E. Burkhart (Forest Science, 2008)
Size-density trajectories on the logarithmic scale are generally thought to consist of two major stages. The first major stage is often referred to as the density-independent mortality stage in which the probability of mortality is independent of stand density; in the second stage, often referred to as the density-dependent mortality or self-thinning stage, the probability of mortality is related to stand density. Within the self-thinning stage, segments of a size-density trajectory consisting of a nonlinear approach to a linear portion, a linear portion, and a divergence from the linear portion are generally assumed. Here, we define the maximum size-density relationship (MSDR) dynamic thinning line as the linear portion. A loblolly pine (Pinus taeda L.) planting density study was used to demonstrate the process of using segmented regression models for estimating stages and phases of stand development. After results from the segmented regression model analyses were obtained, full versus reduced model tests indicated that a portion of self-thinning can be represented as linear. Estimates of the logarithm of quadratic mean diameter (lnD q) and logarithm of trees per hectare (lnN) where the linear component begins and ends were obtained from the segmented regression analyses and used as response variables predicted as a function of planting density. Predicted values of the lnD q and lnN allow for the MSDR dynamic thinning line boundary level and slope to be estimated for any planting density. Estimates showed that MSDR dynamic thinning line boundaries did not all attain the same level but varied by planting density.

Differences in Spruce Budworm Defoliation among Balsam Fir and White, Red, and Black Spruce - Chris R. Hennigar; David A. MacLean; Dan T. Quiring; John A. Kershaw (Forest Science, 2008)
Spruce budworm (Choristoneura fumiferana Clem.) outbreaks severely reduce growth and survival of balsam fir (Abies balsamea [L.] Mill.) and spruce (Picea spp. A. Dietr.) over much of eastern North America, resulting in major reductions in yield and disruption of harvest schedules. This is the first study to rigorously quantify defoliation differences among all four spruce budworm host tree species at a stand level. An extensive permanent sample plot data set, with more than 27,000 tree and 1,117 stand measurements from 1984 to 1992 in New Brunswick, Canada, revealed a clear and consistent hierarchy of host species defoliation susceptibility. Regardless of defoliation severity and other stand variables tested, white (Picea glauca [Moench] Voss), red (Picea rubens Sarg.), and black spruce (Picea mariana [Mill.] B.S.P.) had approximately 72, 41, and 28% as much defoliation as balsam fir, respectively. Balsam fir defoliation was a highly significant predictor of white, red, and black spruce defoliation. Of the variation in defoliation of red-black spruce hybrids, 34% was explained by balsam fir defoliation and an interaction with spruce hybrid index. This is the first model to quantify hybrid red-black spruce defoliation across a full range of severities. Quantitative models of stand-level defoliation differences among host species will improve spruce budworm stand impact forecasts and decision support prioritization of bioinsecticide or salvage operations and provide information to calibrate population-defoliation models for host species in mixed species stand types.

Variance Reduction for Radial Line Sampling Coverage Estimators - Thomas B. Lynch (Forest Science, 2008)
It may be convenient to use radial line sampling for coverage estimates in small irregularly shaped areas. Radial line samples emanate from a fixed point located in the interior of the area and would be run according to a randomly selected azimuth. Thus, radial line sampling is analogous to techniques of local stereology, which considers quantitative aspects of spatial structures in the neighborhood of a central point. Coverage estimates from radial line sampling can be based on coverage observed on several sample lines. Several variance reduction techniques commonly used in Monte Carlo integration are proposed to reduce the variance of coverage estimates based on radial line sampling: importance sampling, control variates, and antithetic variates. The success of these techniques in irregularly shaped areas depends on the assumption that total line length is correlated with length of coverage. Radial line sampling as proposed here differs somewhat from ordinary line sampling because coverage estimates are based on squared line lengths.

δ15N Patterns of Douglas-Fir and Red Alder Riparian Forests in the Oregon Coast Range - Emily E. Scott; Steven S. Perakis; David E. Hibbs (Forest Science, 2008)
We used naturally occurring stable isotopes of N to compare N dynamics in near-stream and upslope environments along riparian catenas in N-fixing red alder (Alnus rubra) and Douglas-fir (Pseudotsuga menziesii) forests in the Coast Range of western Oregon. Based on the existing literature, we expected soil δ15N to be enriched closer to streams owing to inputs of isotopically heavy, marine-derived N by spawning salmon, higher rates of denitrification near the stream, or both. However, it has been unclear what effect red alder might have on soil δ15N patterns near streams. We found a consistent −1‰ δ15N signature in red alder foliage, and δ15N of total N in soils under red alder averaged 2.2‰ along sampling transects extending 20 m upslope from the stream. Surprisingly, δ15N of total N in soil under Douglas-fir was progressively depleted nearer to streams, opposite from the pattern expected from N losses by denitrification or N inputs from anadromous salmon. Instead, δ15N of total N in soil under Douglas-fir converged toward soil δ15N values typical of red alder sites. We consider that the historic presence of red alder may have contributed a legacy of lower soil δ15N nearer to streams on sites that are currently dominated by young Douglas-fir forest.

Tree-Soil Interactions Affect Production of Loblolly and Slash Pine - Christopher A. Dicus; Thomas J. Dean (Forest Science, 2008)
Species-related differences in needle litter nutrient concentrations and subsequent N mineralization were examined in 17-year-old stands of loblolly pine (Pinus taeda L.) and slash pine (Pinus elliottii Engelm.) at a common site. Results of this common-garden study indicate that a feedback may exist between foliar litter nutrient concentration and soil N mineralization. Net N mineralization (to 30 cm) was significantly greater in loblolly pine than in slash pine stands, which was attributed to greater litter nutrient concentrations in loblolly pine. Stand volume production was also greater in loblolly pine than in slash pine and was positively correlated with N mineralization. Although lower litter nutrient concentrations may have reduced productivity of slash pine relative to loblolly pine in this study, they may serve as a mechanism to increase the relative fitness of the species by lowering the soil nutrient availability below the optimum of loblolly pine.

Artificial Regeneration of Major Oak ( Quercus ) Species in the Eastern United States—A Review of the Literature - Daniel C. Dey; Douglass Jacobs; Ken McNabb; Gary Miller; V. Baldwin; G. Foster (Forest Science, 2008)
Although natural regeneration is often the best method for establishing new oak (Quercus spp.) stands, there are increasingly more situations in which high potential for oak regeneration failure dictates the use of artificial regeneration including direct seeding and planting seedlings. Additionally, afforestation planting programs frequently incorporate oak species. Artificial regeneration of oak stands is challenging for numerous reasons. In this article we synthesize the current state of knowledge regarding growing and planting the major oak species in the eastern United States, point out critical research gaps, and provide some general growing, planting, and stand tending guidelines and recommendations. Adequate site preparation, careful planting of healthy, genetically adapted seed or seedlings of high morphological and physiological quality, and subsequent control of competing vegetation and browse damage are necessary actions to assure regeneration success. Oak seedling survival in the early years after planting or seeding is a poor indicator of regeneration success. Successful regeneration may be defined as having a desired proportion of the oak planting stock reach dominant/codominant status in the stand. The costs of all activities required to produce a successful oak tree in the future stand should be considered in economic comparison of alternative prescriptions for oak regeneration.

Soil Carbon and CO2 Efflux as Influenced by the Thinning of Loblolly Pine ( Pinus taeda L.) Plantations on the Piedmont of Virginia - Marcus F. Selig; John R. Seiler; Michael C. Tyree (Forest Science, 2008)
The thinning of loblolly pine plantations has a great potential to influence the fluxes and storage of carbon within managed stands. In this study we investigated the effects of thinning on mineral soil carbon distribution and storage 14 years after the thinning of an 8-year-old loblolly pine plantation on the Piedmont of Virginia. Additionally, we examined patterns of soil CO2 efflux (Es) for 1 year after the second thinning of the same stands at age 22. The study was conducted using three replicate 0.22-ha stands planted using 3.05 × 3.05 m spacing in 1980. Soil carbon in the fine soil fraction (<2 mm) was evenly dispersed throughout thinned plots, and random sampling techniques were adequate for capturing spatial variability. Soil carbon decreased with depth, was higher at all depths in thinned stands, and was significantly higher (P = 0.06) at the 10- to 20-cm depth in the thinned stands (1.04%) compared with unthinned stands (0.76%). Soil temperature was approximately 1–2°C warmer in the growing season and 1°C cooler in the dormant season in thinned stands. Soil moisture was consistently higher in thinned stands by approximately 5%. Temperature was positively and significantly correlated with Es in thinned and unthinned stands. When modeled using regression, thinning was a significant variable for predicting Es (P < 0.0009) but explained less than 1% of the variation. Whereas thinning decreased Es when standardized to a constant temperature, actual Es was elevated in thinned stands because of higher soil temperature.

Investigation of Some Sector Sampling Statistical Properties - Nick J. Smith; Kim Iles; Kurt Raynor (Forest Science, 2008)
Sector sampling is designed to sample objects in clusters or small, irregularly shaped polygons, such as variable retention patches and associated harvested areas. A number of statistical aspects of sector sampling were examined by using real data and a resampling framework. When the sector angle is selected at random, the probability of sampling each tree is the same; thus, a simple expansion factor method is all that is required to calculate tract totals and mean tree values. Standard variance formulas can then be used. For unit area estimates (such as basal area per hectare) a ratio-of-means estimator balances the areas in different-sized sectors. However, both the ratio-of-means mean and variance may be underestimated. An empirical correction to the biased variance estimator was derived. Alternatively, an unbiased and also more efficient unit area estimate can be made using a random point sector angle selection with a mean-of-ratios method. In this case standard variance formulas can again be used. A systematic sector arrangement reduced variance under an expansion factor but did not reduce variance using a ratio-of-means approach where sector area was already considered.

Modeling Effects of Overstory Density and Competing Vegetation on Tree Height Growth - Christian Salas; Albert R. Stage; Andrew P. Robinson (Forest Science, 2008)
We developed and evaluated an individual-tree height growth model for Douglas-fir [Pseudotsuga menziesii (Mirbel) Franco] in the Inland Northwest United States. The model predicts growth for all tree sizes continuously, rather than requiring a transition between independent models for juvenile and mature growth phases. The model predicts the effects of overstory and understory vegetative competition on height growth. Our model requires attained height rather than tree age as a predictor variable, thereby avoiding the problems of site index. Site effects are introduced as a function of ecological habitat type, elevation, aspect, and slope. We used six data sets totaling 3,785 trees in 314 plots. The structure of the data and the model indicated the need for a mixed-effects, nonlinear modeling approach using maximum likelihood in a linear differential equation with a power transformation. Behavior of the model was analyzed using a state-space approach. Our results show that both overstory and understory density affect height growth, allowing a manager to make informed decisions about vegetation control.

Stand Assessment through Lidar-Based Forest Visualization Using Immersive Virtual Environment Technology - Ikuko Fujisaki; David L. Evans; Robert J. Moorhead; Derek W. Irby; Mahnas Jean Mohammadi-Aragh; Scott D. Roberts; Patrick D. Gerard (Forest Science, 2008)
This study examined the utility of light detection and ranging (lidar) remote sensing combined with immersive virtual environment technology for timber stand assessment. Lidar data were used to identify locations and extract dimensional information of trees in immature and mature loblolly pine (Pinas taeda, L) stands in northeast Mississippi. Computer visualized stands were built on the basis of lidar measurements and were projected with an interactive room-size stereoscopic display. Representational quality of lidar-based virtual forests was assessed through stand descriptions made by human subjects recruited from the Department of Forestry at Mississippi State University. Subjects examined either field-recorded videos or computer visualizations of immature and mature stands and estimated stocking, tree size class, height class, rotation stage, stand structure, and hardwood competition of each stand. Estimated stand characteristics by the two groups were compared. Significant viewer group differences were found in height class and rotation stage but not in other characteristics. Discussion includes how the immersive virtual environment technologies are potentially useful in natural resources management. Further study of economic aspects and interface development would be required to promote these technologies to an operational system.

Modeling Airtanker Flight Distance between Concurrent Fires: The Development and Use of Statistical Distribution Parameters - Francis E. Greulich (Forest Science, 2008)
Airtankers, while actively engaging in initial attack, are sometimes reassigned and flown directly to another randomly occurring initial attack fire. Airtanker system planning that means to incorporate this fire-to-fire transfer activity needs information about the flight distance between these randomly located fires. Moments of the distance distribution, derived in this article, can be used to characterize and evaluate fire-to-fire airtanker dispatch within and between protection areas. A hypothetical example illustrates how a proposed change in an airtanker protection zone can affect not only airbase-to-fire flight distance but also fire-to-fire flight distance. In this example, the expected airbase-to-fire distance and the expected total transfer-flight distance are both significantly reduced, but at the same time, somewhat unexpectedly, the average fire-to-fire flight distance actually increases. The discovery and quantification of such unanticipated results can potentially influence airtanker system design. These key system design parameters can now be obtained through the exceedingly fast and accurate analytical methods presented here.

The Effects of Fertilization on Soil Respiration in 2-Year-Old Pinus taeda L. Clones - Michael C. Tyree; John R. Seiler; Thomas R. Fox (Forest Science, 2008)
Fertilization is a common, cost-effective method to increase productivity of managed forests in the southeastern United States; however, little is known about how fertilization will affect the processes that drive total soil CO2 efflux (F S) and ultimately net ecosystem productivity (NEP). The objective of this research was to intensively monitor the response of F S, and its respiratory components during the first year after N and P fertilization in Pinus taeda clones. We monitored F S, heterotrophic respiration (R H), and specific root respiration (R R) and found that F S in fertilized plots differed significantly (P < 0.0001) from that in unfertilized plots, but the direction of this effect was dependent on date. Additionally, R H was consistently lower (P = 0.0001) in fertilized plots relative to control plots, but the magnitude was dependent on the sampling date, and R R significantly (P = 0.04) increased in fertilized plots (+20%) when averaged over the study. Increased R R and decreased R H were probably offsetting each other, resulting in no overall difference in F S 1 year after fertilization. If these short-term trends persisted over the rotation of the stand, increased gross primary productivity accompanied by no change or even a decrease in soil C evolution could result in increased NEP.

Stand-Level Forest Structure and Avian Habitat: Scale Dependencies in Predicting Occurrence in a Heterogeneous Forest - Katherine Manaras Smith; William S. Keeton; Therese M. Donovan; Brian Mitchell (Forest Science, 2008)
We explored the role of stand-level forest structure and spatial extent of forest sampling in models of avian occurrence in northern hardwood-conifer forests for two species: black-throated blue warbler (Dendroica caerulescens) and ovenbird (Seiurus aurocapillus). We estimated site occupancy from point counts at 20 sites and characterized the forest structure at these sites at three spatial extents (0.2, 3.0, and 12.0 ha). Weight of evidence was greatest for habitat models using forest stand structure at the 12.0-ha extent and diminished only slightly at the 3.0-ha extent, a scale that was slightly larger than the average territory size of both species. Habitat models characterized at the 0.2-ha extent had low support, yet are the closest in design to those used in many of the habitat studies we reviewed. These results suggest that the role of stand-level vegetation may have been underestimated in the past, which will be of interest to land managers who use habitat models to assess the suitability of habitat for species of concern.

Worldwide Forest Mensuration History - Harold E Burkhart (Forest Science, 2008)

Deriving Tree Diameter Growth and Probability of Survival Equations from Successive Diameter Distributions - Thomas G. Matney; Emily B. Schultz (Forest Science, 2008)
Many growth and yield models have used statistical probability distributions to estimate the diameter distribution of a stand at any age. Equations for approximating individual tree diameter growth and survival probabilities from dbh can be derived from these models. A general procedure for determining the functions is discussed and illustrated using a loblolly pine spacing study. The results from the spacing study show that it is possible to define tree diameter growth and survival probability functions from diameter distributions with an accuracy sufficient to obtain a link between the individual tree and diameter growth and yield models.

Individual Tree and Stand Level Influences on the Growth, Vigor, and Decline of Red Oaks in the Ozarks - Steven L. Voelker; Rose-Marie Muzika; Richard P. Guyette (Forest Science, 2008)
Repeated oak decline and mortality events have occurred in the Ozark region for decades and probably longer. We sampled an age sequence of 1,259 black and scarlet oaks (Quercus velutina Lam. and Quercus coccinea Muench.) to better describe the process of oak decline and mortality in the red oak group (subgenera Erythrobalanus). Trend in basal area increment (BAI) over the most recent 40 years was used to establish three vigor classes for trees with decreasing, stable, or increasing growth (Declining, Stable, or Healthy). We compared crown condition measures with absolute BAI and boundary line BAI, a measure of radial growth adjusted for tree size. A pulse of mortality was found to occur just subsequent to the most recent drought, although decline often started decades previously. Time series of individual tree BAI suggests that half of all oak decline events were incited by one or two drought-related step-changes in growth and variance. Predisposing factors to decline generally showed significant but weak relationships with crown conditions. Surviving oaks growing in high-mortality stands had poorer crown conditions and grew more slowly than trees in low-mortality stands. When recently dead trees were accounted for, the same high-mortality stands had significantly greater predecline basal area and stocking than low-mortality stands. Thus, a less competitive growth environment may afford some buffer to drought stress before oak decline but does not appear to help afflicted stands improve their growth and vigor.

Tropical Homegardens: a Time-Tested Example of Sustainable Agroforestry - Travis W. Idol (Forest Science, 2007)

Recruitment Patterns in a Mediterranean Oak Forest: A Case Study Showing the Importance of the Spatial Component - Sara Maltez-Mouro; Luis V. García; Teodoro Marañón; Helena Freitas (Forest Science, 2007)
The spatial patterns of recruits in a Mediterranean forest in Southwest Portugal were examined. We aimed to investigate how several environmental and canopy variables contribute to the observed patterns, and how relevant the spatial component is in explaining the variance in the density of recruits. We took a census of every recruit of four dominant woody species (Arbutus unedo, Quercus faginea, Q. suber, and Viburnum tinus), mapping their position inside two forest plots. For a total of 309 recruits, we measured the following variables: soil moisture, slope, canopy density, herbaceous and litter ground cover, overlying species and height, and distance to the nearest adult of the same and different species. Spatial pattern analysis, principal coordinate analysis of neighbor matrices, canonical correspondence analysis, and variance partitioning were performed to detect significant deviations from complete spatial randomness and identify conspecific and interspecific patterns, characterize regeneration niches, and evaluate the importance of the spatial component. Results showed the existence of significant community structure at the recruitment stage. The distance between recruits and the nearest conspecific adult was the main explanatory variable. Light availability, soil moisture, litter accumulation, and the overlying species were also significant factors in explaining the variance in the density of recruits. The best model accounted for 37% of the overall variance in the density of recruits, and most (80%) of the explained variance corresponded to spatially structured variance. This case study shows the importance of the spatial component in understanding the forest regeneration patterns under Mediterranean conditions and will contribute to the implementation of ecologically based management actions to preserve the remaining forest fragments.

Ectomycorrhizal Communities on Tree Roots and in Soil Propagule Banks along a Secondary Successional Vegetation Gradient - Satsuki Yamashita; Kenji Fukuda; Shin Ugawa (Forest Science, 2007)
Changes in the composition of underground ectomycorrhizal communities along a secondary successional vegetation gradient were investigated in Kashiwa City, Kanto District, eastern Japan. Soil cores were sampled from the surface soils of six plots in a successional series of vegetation, and ectomycorrhizal root tips were classified into morphotypes by macroscopic observation and measurement of the internal transcribed spacer 3–4 length of rDNA. The inoculum potential of ectomycorrhizal fungi in the soils was also investigated by germinating and growing Japanese red pine seedlings in pots. The species richness of ectomycorrhizal fungi on tree roots increased along the successional gradient from the pioneer tree stage (Pinus densiflora Sieb. et Zucc. stands) to the middle stage (deciduous Quercus serrata Thunb. and Castanea crenata Sieb. stands) and then slightly decreased in the climax stage (evergreen Quercus myrsinaefolia Bl. stands). The increase in the number of ectomycorrhizal morphotypes was strongly correlated with the increase in the biomass of ectomycorrhizal trees along the succession. Ectomycorrhizal propagule banks were found in the soil of pioneer grass- and shrublands where ectomycorrhizal trees were not present. Unlike the diversity of ectomycorrhizal morphotypes on tree roots, the morphotype richness and diversity of ectomycorrhizal inocula in the soil infective to pine seedlings increased only from the grassland to the pine successional stage and not in the deciduous and evergreen-oak stages. The composition of ectomycorrhizal communities on mature trees and ectomycorrhizal propagule banks in soils showed a successional gradient along the secondary vegetation gradient, but many common morphotypes were present among the different vegetation stages.

The Interaction between Soil Nutrients and Leaf Loss during Early Establishment in Plant Invasion - Elizabeth A. Leger; Katherine M. Howe; Jessica Gurevitch; Eliza Woo; Jonathan Hickman; Isabel W. Ashton; Manuel Lerdau (Forest Science, 2007)
Nitrogen availability affects both plant growth and the preferences of herbivores. We hypothesized that an interaction between these two factors could affect the early establishment of native and exotic species differently, promoting invasion in natural systems. Taxonomically paired native and invasive species (Acer platanoides, Acer rubrum, Lonicera maackii, Diervilla lonicera, Celastrus orbiculata, Celastrus scandens, Elaeagnus umbellata, Ceanothus americanus, Ampelopsis brevipedunculata, and Vitis riparia) were grown in relatively high-resource (hardwood forests) and low-resource (pine barrens) communities on Long Island, New York, for a period of 3 months. Plants were grown in ambient and nitrogen-enhanced conditions in both communities. Nitrogen additions produced an average 12% initial increase in leaf number of all plants. By the end of the experiment, invasive species outperformed native species in nitrogen-enhanced plots in hardwood forests, where all plants experienced increased damage relative to control plots. Native species experienced higher overall amounts of damage in hardwood forests, losing, on average, 45% more leaves than exotic species, and only native species experienced a decline in growth rates (32% compared with controls). In contrast, in pine barrens, there were no differences in damage and no differences in performance between native and invasive plants. Our results suggest that unequal damage by natural enemies may play a role in determining community composition by shifting the competitive advantage to exotic species in nitrogen-enhanced environments.

Calcium Uptake, Partitioning, and Sinuous Growth in Douglas-Fir Seedlings - Kim Littke; Darlene Zabowski (Forest Science, 2007)
Sinuosity is a growth deformation affecting Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] and other conifers. Ca, an essential nutrient in tree growth and cell development, may be deficient in these stands and could be causing sinuous growth. An experiment was conducted to test whether low Ca availability causes sinuous growth in Douglas-fir seedlings. Douglas-fir 1 + 1 seedlings were grown in a greenhouse with high to low Ca availability. After 6 months of growth, the seedlings were measured for sinuosity and separated into new-needles, new-stem, old-needles, old-stem, and roots. High Ca fertilized seedlings had greater new-needle biomass and growth than low Ca fertilized seedlings. High Ca availability also led to higher Ca concentration and content, including higher foliar membrane-associated Ca, Ca-pectate, and Ca-oxalate than low Ca seedlings. Low Ca availability had no significant effect on sinuosity. Although high Ca availability did not alleviate sinuous growth in Douglas-fir seedlings, it did lead to higher growth, foliar biomass, and membrane-associated Ca.

Tree Mortality in Mixed Pine–Hardwood Stands Defoliated by the European Gypsy Moth ( Lymantria dispar L.) - Mark H. Eisenbies; Christopher Davidson; James Johnson; Ralph Amateis; Kurt Gottschalk (Forest Science, 2007)
Defoliation by the European gypsy moth (Lymantria dispar L.) and subsequent tree mortality have been well documented in the northeastern United States. In this study we evaluate tree mortality after initial defoliation in mixed pine–hardwood stands in the southeastern United States as the range of European gypsy moth expands. In 1993, 46 mature pine–oak and pine–sweetgum stands were selected on the coastal plain in Maryland and Virginia along the advancing gypsy moth front. Initial stand conditions, defoliation, and tree mortality after a single defoliation outbreak were monitored for 4 years. Susceptible oaks and sweetgum were defoliated at the greatest intensities. After defoliation, mortality in attacked stands was 4.4 m2/ha higher in pine–oak stands and 1.7 m2/ha higher in pine–sweetgum stands, representing 13 and 3% of the total basal area, respectively. Mortality of pines was observed mainly among suppressed and intermediate trees. Logistic regressions were derived to correlate individual tree mortality to stand and tree factors associated with gypsy moth attack. On the basis of these models, susceptible understory species with degraded crowns in pine–oak stands were at the greatest risk of mortality. Dominant overstory pines in pine–hardwood stands appear to be at low risk.

Predicted Fire Behavior in Selected Mountain Pine Beetle–Infested Lodgepole Pine - Wesley Page; Michael J. Jenkins (Forest Science, 2007)
Using custom fuel models developed for use with Rothermel's surface fire spread model, we predicted and compared fire behavior in lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.) stands with endemic, current epidemic, and postepidemic mountain pine beetle (Dendroctonus ponderosae Hopkins) populations using standardized sets of wind speeds and fuel moistures. We also compared our fire behavior results with those from standard fuel models. Results indicated that for surface fires both rates of fire spread and fireline intensities were higher in the current epidemic stands than in the endemic stands owing to increases in the amounts of fine surface fuels. In the postepidemic stands, rates of surface fire spread and fireline intensities were higher than in the endemic stands owing to decreased vegetative sheltering and its effect on mid-flame wind speed. Total heat release of surface fires, including postfrontal combustion, was also higher in the postepidemic stands owing to heavy accumulations of large diameter fuels. Crown fires were more likely to initiate in the postepidemic stands owing to greater fireline intensities and lower crown base heights. However, the critical rate of spread needed to sustain an active crown fire was higher in the postepidemic stands owing to decreased aerial fuel continuity. We suggest here that crown fire initiation in the current epidemic stands was also greater because of an abundance of dead aerial fuels; although this relationship is unclear.

Preharvest Measurement of Marked Stands Using Airborne Laser Scanning - Jussi Peuhkurinen; Matti Maltamo; Jukka Malinen; Juho Pitkänen; Petteri Packalén (Forest Science, 2007)
The customer-oriented wood procurement chain from forest to raw material user starts with a knowledge of stands available for harvesting and information on these marked stands. Despite several studies, no adequate method has been developed for obtaining preharvest measurement information to meet existing requirements. The aim here was to develop a method for the preharvest measurement of a marked stand based on single tree detection and airborne laser scanning. The trees were detected from high-density laser scanning data using automatic detection procedures, and their dbh was estimated using either local or regional models. The method was compared with actual harvester measurement of the stand and alternative methods for obtaining preharvest measurement information (systematic plot sampling, subjective inventory by compartments, and the laser canopy height distribution method). The comparisons of the methods were based on goodness-of-fit tests of diameter distributions and bucking simulations. The results indicated that the laser scanning-based single tree detection procedure has considerable advantages over other methods. The crucial point in applying the method seemed to be the choice of diameter prediction model.

Leaf Nutrient Concentrations and Timber Productivity in the Dry Sclerophyll Forests of South-East Queensland, Australia: Implications for Arboreal Marsupials - Kevin Ray Wormington; David Lamb; Hamish Ian McCallum; Damien John Moloney (Forest Science, 2007)
The species richness and abundance of arboreal marsupials are positively related to the proportion of total stand basal area occupied by Corymbia citriodora ssp. variegata and tree height in South-East Queensland and have been related to nutrient availability and productivity in other parts of Australia. The objectives of this study were to assess the relationships of stand basal area occupied by C. citriodora and tree height, and the available nutrients and productivity in the dry sclerophyll forests of South-East Queensland. Leaf nutrient analysis of seven species of trees in South-East Queensland showed that the percentage by weight of phosphorus in leaves increased with the proportion of the total stand basal area of C. citriodora. This rate of increase was greater for C. citriodora than other species, indicating that C. citriodora may be more competitive on soils with greater available phosphorus. C. citriodora leaves also contained higher concentrations of nitrogen and potassium than the other tree species on multispecies sites. Timber productivity was greater at the sites where trees were taller, and tree height was positively correlated to the proportion of total stand basal area of C. citriodora and rainfall but was negatively correlated to the slope. These findings indicate that the most used habitat by arboreal marsupials in the dry sclerophyll forests of South-East Queensland (i.e., taller forests with a high proportion of the stand basal area occupied by C. citriodora) had higher concentrations of foliar nutrients and were more productive than less used habitats.

Effects on Estimation Accuracy of Forest Variables Using Different Pulse Density of Laser Data - Mattias Magnusson; Johan E.S. Fransson; Johan Holmgren (Forest Science, 2007)
Collection of airborne laser scanner data for forest inventory is becoming a common practice today. To reduce cost when laser data are collected over large areas, the flight altitude or flight speed may be increased, resulting in low pulse density laser data. The effect of using a different pulse density of laser data on estimation accuracy of forest variables was investigated at stand level. Laser data were acquired by the airborne TopEye system at a 1,200-ha forest area located in southern Sweden (58°30′N, 13°40′E). The 70 selected stands were dominated by Norway spruce [Picea abies (L.) Karst.] and Scots pine (Pinus sylvestris L.) with tree height in the range of 6–28 m (mean 19 m) and stem volume in the range of 30–620 m3 ha−1 (average 286 m3 ha−1). Regression analysis was used to establish empirical functions at stand level. The pulse density of laser data was reduced from 25,000 to 40 returns ha−1. By reducing the pulse density the root mean square error (RMSE) for the tree height and stem volume estimation increased from 0.7 to 1.8 m and from 13% to 29%, respectively. A substantial decrease in estimation accuracy of tree height and stem volume could be observed at pulse densities <80 returns ha−1 (corresponding to about 10 m between adjacent laser returns). The rapid increase in RMSE at these pulse densities could be explained by the less accurate classification of ground returns. With access to a high resolution digital elevation model the RMSE for the tree height and stem volume estimation increased from 0.7 to 1.1 m and from 13% to 23%, respectively, as an effect of the reduced pulse density. Even though the pulse density was reduced to several meters between adjacent laser returns, the estimation accuracies were equal to or better than those commonly obtained by using conventional forest inventory methods, e.g., aerial photo interpretation. This finding implies that low pulse density airborne laser scanner data could be cost efficient to use in inventory for estimation of forest variables at stand level.

Density Frontiers for Even-Aged Douglas-fir and Western Hemlock Stands in Coastal British Columbia - Louise de Montigny; Gordon Nigh (Forest Science, 2007)
Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco var. menziesii) and western hemlock (Tsuga heterophylla [Raf.] Sarg.) are the two most common and commercially important species on the coast of British Columbia, Canada. Our research focused on determining the relationship between maximum density and top height for pure stands of these species. These relationships can be used to provide a constraint on mortality functions in individual-tree growth and yield models for even-aged stands. Our data consist of density and top height from experimental plots established along the coast of British Columbia, Washington, and Oregon. These experiments yielded 2,930 observations from 628 plots. We fit stochastic frontier functions to the density/top height data. Stochastic frontier functions have a stochastic component that allows data points to lie on either side of the frontier. The fitting of the frontier functions using maximum likelihood estimation resulted in maximum density lines as an exponential function of top height for both species. The fitted model is based loosely on the −3/2 power thinning law. Our analysis shows that these relationships hold across sites with differing quality. The maximum density line is greater for western hemlock than for Douglas-fir up to a height of about 35 m, at which point they are almost the same. The higher maximum density of western hemlock is likely related to its greater shade tolerance. We used the growth-and-yield model Table Interpolation Program for Stand Yields (TIPSY) to simulate the growth of high-density stands of Douglas-fir and western hemlock. These simulations gave similar results to our fitted density frontier line.

Biomass Removal, Soil Compaction, and Vegetation Control Effects on Five-Year Growth of Douglas-fir in Coastal Washington - Adrian Ares; Thomas Terry; Constance Harrington; Warren Devine; David Peter; John Bailey (Forest Science, 2007)
Sustainable forest production requires an understanding of the effects of site disturbance on tree growth and the consequences of soil amelioration and vegetation control practices. We assessed the impacts of biomass removals at harvest, soil compaction and tillage, and vegetation control on early growth of Douglas-fir in coastal Washington. Harvest treatments included removal of commercial bole only (BO), bole only up to 5-cm top diameter (BO5), total tree (TT), and total tree plus all legacy coarse woody debris (TTP). Vegetation control (VC) effects were tested in BO, while soil compaction (BO/SC) and compaction plus tillage (BO/SCT) were imposed in BO/VC. Five years after planting, biomass removal and soil compaction/tillage effects on tree growth were relatively small. At year 5, mean stem basal diameter in BO was greater than in TT, whereas mean height was similar in BO and BO/SC, but increased in BO/SCT. Control of competing vegetation markedly increased tree growth. At year 5, mean tree stem diameter at 1.3-m height (dbh) and height in BO/no vegetation control (NVC) were 34 mm and 308 cm, respectively, compared to 45 mm and 357 cm in BO/VC (P <0.01). Mean relative growth rate in stem diameter for trees in BO/VC was greater than in BO/NVC in years 2–4, but this trend reversed in year 5, suggesting that tree intraspecific competition may be greater in BO/VC than in BO/NVC. Vegetation control also increased second-flushing (i.e., the flushing of set buds in late summer) in years 4 and 5. Vegetation competition effects on tree growth appeared to be related to changes in available soil water rather than to competition for nutrients.

The Longleaf Pine Ecosystem: Ecology, Silviculture, and Restoration - Lindsay R. Boring (Forest Science, 2007)

Scaling Taper Relationships from Miniature-Scale to Operational-Scale Stands of Loblolly Pine - Mahadev Sharma; Harold E. Burkhart; Ralph L. Amateis (Forest Science, 2007)
Taper relationships for trees grown in miniature- and operational-scale stands of loblolly pine were established using stem analysis data from 106 and 173 trees, respectively. Tree taper was modeled using segmented polynomial and dimensionally compatible taper equations. The relationship was then scaled from miniature to operational scale using the profiles obtained from these taper equations. Stump diameter was used in the taper equations instead of dbh in scaling the relationship. A simple linear regression equation described well the taper relationship between trees grown at miniature and operational scales. The fit statistics for both the segmented polynomial and dimensionally compatible taper equations were comparable at both scales. In terms of predictive accuracy, however, the segmented polynomial taper equation was superior to the dimensionally compatible taper equation in scaling the taper relationship for trees from miniature- to operational-scale plots.

An Alternative to Traditional Goodness-of-Fit Tests for Discretely Measured Continuous Data - KaDonna C. Randolph; Bill Seaver (Forest Science, 2007)
Traditional goodness-of-fit tests such as the Kolmogorov-Smirnov and χ2 tests are easily applied to data of the continuous or discrete type, respectively. Occasionally, however, the case arises when continuous data are recorded into discrete categories due to an imprecise measurement system. In this instance, the traditional goodness-of-fit tests may not be wholly applicable because of an unmanageable number of ties in the data, sparse contingency tables, or both; therefore, a flexible alternative to goodness-of-fit tests for discretely measured continuous data is presented. The proposed methodology bootstraps confidence intervals for the difference between selected percentiles of the empirical distribution functions of two samples. Application of the approach is illustrated with a comparison of loblolly pine (Pinus taeda L.) tree crown density distributions at the 10th, 25th, 50th, 75th, and 90th percentiles simultaneously.

Ice Damage in Loblolly Pine: Understanding the Factors That Influence Susceptibility - Doug P. Aubrey; Mark D. Coleman; David R. Coyle (Forest Science, 2007)
Winter ice storms frequently occur in the southeastern United States and can severely damage softwood plantations. In January 2004, a severe storm deposited approximately 2 cm of ice on an intensively managed 4-year-old loblolly pine (Pinus taeda L.) plantation in South Carolina. Existing irrigation and fertilization treatments presented an opportunity to examine the effects of resource amendments on initial ice damage and subsequent recovery. Fertilized treatments showed more individual stem breakage, whereas nonfertilized treatments showed more stem bending; however, the proportion of undamaged trees did not differ between treatments. Irrigation did not influence the type of damage. Trees that experienced breakage during the storm were taller with larger diameter and taper and leaf, branch, and crown biomass compared with unbroken trees. One growing season after ice damage, relative height increases were significantly greater for trees experiencing stem breakage compared with unbroken trees; however, relative diameter increases were significantly lower for these trees. Relative diameter increases for broken trees were smaller for fertilized treatments compared with nonfertilized treatments. A reduction in wood strength was ruled out as the cause of greater breakage in fertilized trees; rather, fertilized trees had reached an intermediate diameter range known to be susceptible to breakage under ice loading.

Rooting of Leafy Stem Cuttings of Baillonella toxisperma - Marie Ngo Mpeck; Alain Atangana (Forest Science, 2007)
Rooting ability in Moabi was examined using 972 single-node leafy stem cuttings set in each of three blocks of a split-split plot experimental design in nonmist propagators. Each main plot contained three rooting media (sand, sawdust, and a 50:50 mixture of sand and sawdust), whereas three auxin types (indole-3-acetic acid [IAA], indole-3-butyric acid [IBA], and 1-naphthalene acetic acid [NAA]) and a control (alcohol) were tested at the subplot level. At the sub-subplot level, three leaf areas (25, 50, and 75 cm2) were investigated. Significant (P = 0.05) and nonsignificant substrate × hormone × leaf area interactions on rooting percentage were found at week 8 and during the rest of experiment, respectively. Significant sand versus sawdust × IBA versus IAA and NAA × quadratic components of leaf area interaction on rooting percentage was identified from week 10 to week 14 (P = 0.0462–0.038), and the highest rooting percentage (85.2 ± 7.24%) was found in 75 cm2 × IBA × sand-treated cuttings at week 14. Significant substrate × leaf area interaction on rooting percentage was observed throughout the experiment. Interacting substrate × leaf area significantly influenced the number of roots per rooted cutting at week 22. This study indicated that Moabi is amenable to vegetative propagation within 14 weeks.

Common Law Liability for Landowners When Using Prescribed Fires on Private Forest Land in the Southern United States - Changyou Sun (Forest Science, 2007)
The potential liability associated with escaped fires has been a widespread concern to forest landowners when using prescribed fires on private forestland. In this study, common law for prescribed fires on forestland in the 13 southern states was analyzed by examining published legal cases. A thorough search on the legal database of Westlaw generated a list of 27 cases at the state appellate courts. Major characteristics of these cases were summarized by features such as state, year, ownership type, and liability of landowner. Furthermore, these cases were analyzed under three focus areas: negligence rules, strict liability, and vicarious liability. Overall, the standard of care associated with the reasonable prudent person has been required for the intentional use of fire on forestland with a lawful purpose. In the past, gross negligence rule and strict liability have not been applied in the South. Vicarious liability may become a chief concern for forest landowners in the future.

Relative Influence of the Components of Timber Harvest Strategies on Landscape Pattern - Eric J. Gustafson (Forest Science, 2007)
Forest managers seek to produce healthy landscape patterns by implementing harvest strategies that are composed of multiple management components such as cutblock size, rotation length, even-aged or uneven-aged residual stand structure, conversion to plantations, and the spatial dispersion of harvest units. With use of the HARVEST model and neutral landscapes, a factorial simulation experiment was conducted to determine how each management component influenced measures of spatial pattern. There was a significant overall effect of all components on response variables defined by age class and on all but the rotation length component for response variables defined by forest type. Increasing cutblock size, rotation length, and clustering of cutblocks generally reduces measures of age class fragmentation, and increasing the use of even-aged management increases fragmentation. The response of forest type variables was consistently dominated by the component (percent plantation) that changed the abundance of a forest type. Dispersion also had a significant effect because conversions were allocated in space through the dispersion treatment. The results can be used to develop strategies to mitigate negative effects of certain silvicultural activities by showing which other components have opposite effects. Managers can better predict how specific strategy components will contribute to the cumulative landscape pattern.

Parameter Estimation of Base–Age Invariant Site Index Models: Which Data Structure to Use?—A Discussion - Chris J. Cieszewski; Mike Strub (Forest Science, 2007)
We discuss here methods of comparing various approaches to site-dependent height–age model-parameter estimation. The discussion emphasis is on proper analysis of the varying parameter (VP) method versus several variants of the algebraic difference methods including one with the error in variable (EIV) theory adaptation. The study has demonstrated that, when properly considered, the VP method consistently outperforms all the other methods including the EIV method. The EIV method was tested on data with known “true model” and drastically simplified errors, and had a root mean square error (RMSE) more than 10 times worse than the VP method. All the other methods produced drastically and uniquely differing results with RMSEs varying from 26 times greater than the VP method to 300 times greater. The patterns of relatively close similarity between the EIV and the VP methods and the large differing among the other methods was similar for fittings to real data of second-rotation loblolly pine (Pinus taeda L.) from a designed experiment. The VP method is recommended for use over all the other methods as the most unbiased and as much simpler than the EIV method, which was second best.

Parameter Estimation of Base-Age Invariant Site Index Models: Which Data Structure to Use? - Mingliang Wang; Bruce Borders; Dehai Zhao (Forest Science, 2007)
Two main approaches to estimating parameters of dominant height curves (derived by algebraic difference approach (ADA) and generalized ADA (GADA)), the dummy variable method and the difference approach (the error-in-variable (EIV) method along with ordinary least-squares (OLS) fits)are compared using second-rotation loblolly pine (Pinus taeda L.) data from a designed experiment. It was found that the EIV method consistently performed better than the dummy variable method, and the two unbiased estimation methods were not necessarily better than the biased OLS differencemethods. In general, the performance of these two approaches was similar in height prediction given site index, but in combination with site index prediction given heights, the difference methods generally performed better. The nonoverlapping forward difference data structure (III), is recommendedto fit difference models.

Modeling Tree Recruitment with Zero-Inflated Models: The Example of Hardwood Stands in Southern Québec, Canada - Mathieu Fortin; Josianne DeBlois (Forest Science, 2007)
In recruitment modeling, the response variable is a count and its distribution is often characterized by an excess number of zeros. As a result, standard distributions of probabilities, such as Poisson, are inappropriate. A common approach in forestry consists of using two-part conditional models. These models have two distinct components aimed to predicting the occurrence and abundance of recruitment, respectively. For such data, zero-inflated models might provide a more adequate framework by combining the two components into a joint distribution of probabilities. In this article, a conditional model is compared with two different zero-inflated models, namely, a zero-inflated Poisson (ZIP) and a zero-inflated discrete Weibull (ZIdiW) model. The three models were calibrated using a data set provided by permanent sample plots located in hardwood stands. Parsimony criteria (the Akaike information criterion and the Bayesian information criterion) and diagnostic plots were used to perform the comparison. The results show that the ZIdiW model has the best fit. The flexibility of the Weibull function and the possibility of obtaining a more parsimonious model are two advantages related to the use of a ZIdiW model in recruitment modeling.