Front Matter Volume 45 Issue 4 1999 (Forest Science, 1999)

Evidence of Resistance to the Pitch Canker Pathogen ( Fusarium circinatum ) in Native Stands of Monterey Pine ( Pinus radiata ) - Andrew J. Storer; Pierluigi Bonello; Thomas R. Gordon; David L. Wood (Forest Science, 1999)
Resistance of Monterey pine, Pinus radiata, to pitch canker, caused by Fusarium circinatum, was investigated in a naturally regenerated native stand and a planted stand on the Monterey Peninsula, California. A dose of 125 spores was selected to test resistance as it produced significant differences in mean lesion length among trees. The resistance ranking of trees remained comparable when inoculated three times over a period of seven months, but the mean lesion length decreased with each inoculation. Lesion lengths were positively correlated with symptom development. In the naturally regenerated stand, 30% of the trees formed lesions less than 5 mm long and were considered resistant to the pathogen. In contrast, only 5% of trees in the planted stand formed lesions less than 5 mm long. The use of prescribed burning of Monterey pine stands to augment natural regeneration allows a wider expression of genetic diversity in the new host populations on which natural selection in favor of resistant genotypes can be imposed by the pathogen. For. Sci. 45(4):500-505.

Assessing Tree and Stand Biomass: A Review with Examples and Critical Comparisons - Bernard R. Parresol (Forest Science, 1999)
There is considerable interest today in estimating the biomass of trees and forests for both practical forestry issues and scientific purposes. New techniques and procedures are brought together along with the more traditional approaches to estimating woody biomass. General model forms and weighted analysis are reviewed, along with statistics for evaluating and comparing biomass models. Additivity and harmonization are addressed, and weight-ratio and density-integral approaches are discussed. Subsampling methods on trees to derive unbiased weight estimates are examined, and ratio and difference sampling estimators are considered in detail. Error components for stand biomass estimates are examined. This paper reviews quantitative principles and gives specific examples for prediction of tree biomass. The examples should prove useful for understanding the principles involved and for instructional purposes. For. Sci. 45(4):573-593.

Brief Notice (Forest Science, 1999)

Meeting Announcements (Forest Science, 1999)

Heterobasidion annosum: Biology, Ecology, Impact, and Control - William J. Otrosina (Forest Science, 1999)

An Optimization Approach to Selecting Research Natural Areas in National Forests - Stephanie A. Snyder; Lucy E. Tyrrell; Robert G. Haight (Forest Science, 1999)
The USDA Forest Service has a long-established program to identify areas in national forests for designation as protected Research Natural Areas (RNAs). One of the goals is to protect high quality examples of regional ecosystems for the purposes of maintaining biological diversity, conducting nonmanipulative research and monitoring, and fostering education. When RNA designation conflicts with other land uses, difficult choices must be made about the best number and location of sites. We addressed this problem by adapting a classic optimization formulation from the location science literature. The formulation was an integer optimization model for selecting the set of RNAs that maximized the number of regional ecosystems and natural communities represented subject to an upper bound on the total area covered by the sites in the selected set. We applied the formulation using 33 potential RNAs in the Superior National Forest in northeastern Minnesota. The 33 potential RNAs were chosen for our case study because they had been mapped and field-surveyed for the presence of natural communities. The use of those sites does not imply that other areas in the Superior National Forest do not merit further study as RNA candidates. The model quickly generated information about the trade-offs between different protection goals. We found multiple sets of potential RNAs, ranging from all 33 sites to a much smaller set of 21 sites, that attained the specified goals for natural community representation. Thus, the decision-maker can choose among sets of sites with a wide range of total areas without compromising the representation goal. We also found that requirements to choose a set of sites that represents a range of locally defined ecosystems or priority natural communities can limit the total number of natural communities that can be represented within a set of sites of a given area. Average solution times for different problems were less than 5 seconds on a personal computer, suggesting that integer optimization can readily facilitate investigation of the impacts of RNA selection goals. For. Sci. 45(3):458-469.

Accounting for Bias and Uncertainty in Nonlinear Stand Density Indices - Mark J. Ducey; Bruce C. Larson (Forest Science, 1999)
Several commonly used stand density indices, such as Reineke's stand density index, Drew and Flewelling's relative density index, and Curtis's relative density index, depend in a nonlinear fashion on stand-level means of measured variables. Thus, the stand-level index value is not necessarily the mean of the plot-level index values. We show formally that this dependency introduces a bias that depends on the sample size or number of plots and on the variance-covariance structure of the measured variables. We then present formulas for estimating the bias and variance or standard error of estimated densities based on a priori knowledge of the variances and covariances or on observed sample data. We also present and compare bootstrap and jackknife methods of estimating the bias and variance associated with sample estimates. The results suggest that for some indices, the bias and variance arising from quick "grab samples" may be large enough to be of practical significance. These results have strong implications for the development and interpretation of stocking guides derived from single plots or from measurement schemes other than those employed in practical applications. For. Sci. 45(3):452-457.

A Comparison of Periodic and Annual Forest Surveys - Charles T. Scott; Michael Köhl; Hans Jörg Schnellbächer (Forest Science, 1999)
Forest surveys of large areas often are conducted on a periodic basis, every 10 yr, for example. However, periodic assessments can be problematic due to fluctuating budgets and survey results that do not reflect forest dynamics between measurements. As a result, many countries are interested in designing surveys with annual measurements, such as the U.S. Forest Health Monitoring (FHM) Program design. The existing periodic design for Switzerland was compared with four annual designs in which an equal number of plots are observed annually. Data for the comparisons were collected annually on 682 plots over 7 successive yr across Switzerland. Three estimation methods were applied to each design: Continuous Forest Inventory, Sampling with Partial Replacement, and Mixed Estimator. These used simple means, regression updating, and inverse weighting of new and old plots, and regression combined with growth-model projections, respectively. For 12 combinations of 3 attributes, the Regional Survey design was the most cost-effective, followed by the National or Regional Update Survey designs. The Periodic Survey and the National Survey (similar to the FHM design) were the least cost-effective. Sampling with Partial Replacement was the most efficient estimator, though the Mixed Estimator would have been the most efficient had less biased growth projection models been used. For. Sci. 45(3):433-451.

Sweetgum and Broomsedge Response to Competition Across a Range of Soil Organic Matter During the First Year of Plant Establishment - Bruce R. Zutter; Glenn R. Glover; Robert J. Mitchell; Dean H. Gjerstad (Forest Science, 1999)
Sweetgum (Liquidambar styraciflua L.) seedlings and broomsedge (Andropogon virginicus L.) rooted tillers were planted in a factorial combination of densities (additive series) in east central Alabama on a formerly cultivated field which varied in soil organic matter (soil OM). Mean plant aboveground biomass of sweetgum one growing season after planting declined in a hyperbolic fashion as a function of increasing density of either itself or broomsedge. Broomsedge biomass over the same time period also declined in a hyperbolic fashion as a function of increasing density of itself and sweetgum, except for sweetgum densities from 0 to 1 m-2, where biomass did not change. Sweetgum response was positively correlated with soil OM across all species-density combinations, whereas broomsedge response was correlated with soil OM only at higher densities of broomsedge. Nonlinear models including both species density and soil OM explained a nearly equal amount of variation in response of each species: 74 to 75% for sweetgum and 70% for broomsedge. Relative effects of intraspecific versus interspecific competition on the response of each species was dependent on the density of one or both species. Effect of sweetgum on broomsedge response was two to three times that of broomsedge on itself, with the effect decreasing slightly as soil OM decreased. Over a common range of densities of each species, effects of broomsedge on sweetgum were slightly greater than or nearly equal to effects of sweetgum on itself. The greater interspecific effects on the response of each species suggests no niche differentiation between broomsedge and sweetgum through one growing season. For. Sci. 45(3):423-432.

Recovering Tree Heights from Airborne Laser Scanner Data - Steen Magnussen; Paul Eggermont; Vincent N. LaRiccia (Forest Science, 1999)
Airborne laser scanner data collected over forests provide a canopy height. To obtain tree heights from airborne laser scanner data one needs a recovery model. Two such models, one (A) assuming that observations are sampled with probability proportional to displayed crown area, and the other (B) derived from the probability that a laser beam penetrates to a given canopy depth, were developed and applied to laser scanner data obtained over stands of Douglas-fir. Model estimates of recovered arithmetic mean tree heights and quantiles (75%, 85%, and 95%) were not significantly (P> 0.24) different from ground-based equivalents. An overall mean bias of-3 m in the laser canopy heights was eliminated by both methods. The median absolute difference between observed and predicted plot means and quantiles were reduced by 40 to 60%. Three alternative recovery procedures are presented for model B. For a single plot, the predictions varied significantly among the models and estimation procedures with no consistent pattern. Predictions of arithmetic mean heights were best for plots with no understory, while predictions of upper quantiles were consistent in all plots. For. Sci. 45(3):407-422.

Developing Resource-Based Social Conflict Models for Assessing the Utility of Negotiation in Conflict Resolution - René H. Germain; Donald W. Floyd (Forest Science, 1999)
Social conflicts over the management of natural resources are increasing. An informative example of these conflicts is the debate over the management of our national forests. Despite sincere efforts by the USDA Forest Service to improve modes of public involvement, as well as the institutionalization of dispute resolution procedures, the contentiousness and frequency of conflict continues to escalate. This is manifest in the high number of administrative appeals on forest plans and projects. The study used a nation-wide survey of 238 appellants (response rate of 75%) of Forest Service management decisions to test the predictive utility of social conflict models for determining the feasibility of negotiation in resolving environmental conflict. This paper addresses the question of whether the utility of negotiation can be predicted based on (1) the resources involved in the dispute, (2) how those resources are being utilized, and (3) the perceived impact on social, economic, and health issues. The social conflict models proved to have some utility in predicting the types of conflict that may be predisposed to resolution through negotiation. For. Sci. 45(3):394-406.

A Framework for Designing Forest Subsidies: Linking Landowner and Regional Impacts in the Mississippi Delta - Jay Sullivan; Gregory S. Amacher (Forest Science, 1999)
We examine the economic impacts of land use shifts from agricultural to forestry production in the Mississippi Delta at both landowner and regional economy levels. The economic impacts that we consider include net revenues to farmers who convert Delta soybean lands to forest, and the changes employment, income, value added, industry output, and taxes that we expect to occur across a three state regional economy. We develop a framework that links these landowner and regional impacts in order to compare economic impacts of land use changes at landowner and regional levels, and to investigate the self-financing potential of subsidies. Results at the landowner level indicate that conversion may provide positive returns on better soils for some tree species. Results at the regional economy level indicate that the impacts would be generally negative, although landowner subsidies are computed that could equalize the regional impacts of forestry and soybean production. Further, for limited combinations of tree species and soil type, landowner subsidies could be self-financing, providing tax revenues that could offset government outlays. Our results imply that if subsidies were adopted, they should target species and site conditions. For. Sci. 45(3):381-393.

Incomplete Block Designs for Genetic Testing: Statistical Efficiencies with Missing Observations - Yong-Bi Fu; Alvin D. Yanchuk; Gene Namkoong; G. Peter Y. Clarke (Forest Science, 1999)
Missing observations are common in forest genetic field trials and are expected to reduce statistical efficiencies of any applied field designs. Such reductions could lower the presumed efficiency and other benefits of implementing any incomplete block designs (ICBs). In this study, we addressed this by computer simulation of a full-sib progeny trial with up to 20% of the observations missing. Four scenarios of missing observations (random, row, column, and genetic mortality) and tests of both clones and seedling families were examined. Two types of ICBs (alpha and no constraint) with single-tree plots, and their corresponding randomized complete block design (RCB), were considered on test sites with gradient and patchy environmental variation. Our simulations show that: (1) the statistical efficiencies of estimating family (or clone) means with both ICB and RCB were very sensitive to the percentage, not the scenarios, of missing observations examined; (2) the statistical efficiencies for both ICB and RCB were reduced as the number of missing observations increased, except in the cases of clonal genetic mortality; (3) the relative efficiency of ICB over RCB (at equal levels of missing observations) was reduced slightly as the level of missing observations increased; (4) the relative efficiencies for the seedling family tests were a little more sensitive to the levels of missing observations than those for the clonal tests, and; (5) the two ICBs showed little variation in the relative efficiencies across the missing observation scenarios and test conditions examined. Implications of these results for forest genetic field trials are discussed. For. Sci. 45(3):374-380.

Considering Intergenerational Equity in Linear Programming-Based Forest Planning Models with MAXMIN Objective Functions - Roger Church; P. J. Daugherty (Forest Science, 1999)
This paper describes alternative approaches to formulating linear-programming-based forest planning models. These approaches consider a form of equity between current and future generations, as represented by the periods in a planning horizon. Both nominal net revenue in each period and each period's present net worth with values discounted relative to each period, are used as criteria for welfare. The minimum present net worth or net revenue outcome obtained for the set of periods is maximized. The approaches are different. Using present net worth relative to each period as a criterion allows for a concern for economic efficiency and allows variation in net revenue. Using net revenue focuses on a more even distribution of net revenue between periods. The approaches are tested in a case study, and the results are compared to those from a standard approach of maximizing present net worth relative to the first period. The results suggest that the approaches could be useful in a forest planning context, either as an alternative to standard approaches or as a means of generating relevant information. For. Sci. 45(3):366-373.

Effects of Douglas-Fir Dwarf Mistletoe on Trees in Thinned Stands in the Pacific Northwest - Robert O. Tinnin; Catherine G. Parks; Donald M. Knutson (Forest Science, 1999)
The growth of 450 Douglas-fir (Pseudotsuga menziesii) in thinned stands was assessed over 20 yr. Trees infected with Douglas-fir dwarf mistletoe (Arceuthobium douglasii) were compared with uninfected trees. A significant reduction in radial and height growth was observed when infection progressed beyond half to two-thirds of the volume of a tree crown being composed of witches' broom. Growth rates varied over time, depending on environmental conditions, but heavily infected trees showed significantly reduced growth under all observed conditions. The effect of dwarf mistletoe on diameter growth in heavily infected trees was greater when the trees grew under more rigorous conditions. Tree vigor, as estimated by the ratio of basal area increment to sapwood area, was significantly reduced among trees with more than two-thirds of the crown broomed. The level of infection was measured using broom volume rating, a seven-class system based on a ratio of the volume of broomed to unbroomed branches. Over a 10-yr period, tree infection class increased at the rate of approximately one infection class every 15 yr on average. At high levels of infection, crown decline and dieback contributed to an accelerated rate of change in infection class in this study. For. Sci. 45(3):359-365.

Vertical Overstory Canopy Architecture of Temperate Deciduous Hardwood Forests in the Eastern United States - Xiusheng Yang; Jeffrey J. Witcosky; David R. Miller (Forest Science, 1999)
The stand attributes and vertical overstory profiles of plant area (the total projected surface area of all canopy elements including leaves, twigs, and stems) for 15 temperate deciduous hardwood forest types were studied and reported. The study was conducted across the eastern United States within forest type-groups of boreal hardwood, northern hardwood, and upland oak. Vertical distributions of plant area were measured with gap-fraction-based optical sensors mounted on a mobile sampling tower. In general, the stand attributes of the surveyed forest types exhibited distinct characteristics among the three type-groups. The vertical profile of the overstory plant area demonstrated significant differences among forest types and therefore represented an important architectural feature of a forest type. The vertical profile data were well described by a modified Weibull cumulative distribution function. The two model parameters, one indicating a depth for 63% foliage inclusion and the other representing skewness, were presented for each of the 15 forest types. These two model parameters can be used to depict the vertical distribution of overstory plant area in other stands of the same types. The vertical profiles of overstory plant area were related to the successional characteristics and understory tolerance. For. Sci. 45(3):349-358.

Distributive Impacts of Forest Resource Policies in Alberta - Janaki R. R. Alavalapati; Wiktor L. Adamowicz; William A. White (Forest Science, 1999)
Economy-wide and distributive impacts of: (1) an $80 million increase in pulp and paper exports; (2) a $10 million decrease in lumber exports; (3) a 25% increase in the costs of timber production; and (4) a 25% increase in the costs of pulp and paper production in Alberta's forest sector are examined. A social accounting matrix (SAM)-based quantity model is used to examine the first two shocks, while a SAM-based price model is used to analyze the last two shocks. The results of the quantity model suggest that higher income households get a larger share of the benefits than lower income households in response to an expansion in the pulp and paper industry. A contraction in the lumber sector will hurt higher income households more than lower income households. Larger shares of medium and higher income households in total labor income and capital rents are identified as reasons for this asymmetric response. The results of the price model suggest that additional costs associated with sustainable forest management and environmental regulations will hurt lower income households more than higher income households. The higher share of consumer expenditure in total income for lower income households when compared to that of high income households may be responsible for this result. For. Sci. 45(3):342-348.

Age-Related Changes in Production and Below-Ground Carbon Allocation in Pinus Contorta Forests - Frederick W. Smith; Sigrid C. Resh (Forest Science, 1999)
A decline in wood production and above-ground net primary production (ANPP) following an early maximum is a widely observed feature of forest development. Why should relatively young, seemingly vigorous even-aged forests undergo this decrease in production? We measured above-ground net primary production and below-ground carbon allocation in an age sequence of lodgepole pine forest in south-central Wyoming spanning 260 yr of forest development. ANPP and total root carbon allocation (TRCA) are examined to determine if there is an increase in TRCA of sufficient magnitude to offset the observed decrease in ANPP in developing lodgepole forests. Also, we examined changes in canopy structure, leaf area efficiency (E), and above-ground carbon allocation patterns to determine their potential role in the age-related decrease in ANPP. ANPP declined by 50% between peak production of 192 gC m-2yr-1 at age 30 to 92 gC m-2yr-1 at age 260, largely as a decrease in stemwood production. TRCA was similar for forests from 30 to 100 yr old, but was significantly less in 260-yr-old forest at 391 gC m-2yr-1 than in younger lodgepole forests at 516 gC m-2yr-1. Declining ANPP was not due to an increase in carbon allocation to below-ground production. Net primary production (NPP), the total of above-ground and below-ground NPP, declined by 36% from 450 gC m-2yr-1 at age 30 to 288 gC m-2yr-1 at age 260. This progressive decline in NPP was associated with changes in stand structure that occur during stand development, including decreased leaf area, shifting carbon allocation, and decline in leaf area efficiency. Our results suggest that a combination of several factors, acting in concert, produce the observed decline in ANPP associated with the development of even-aged lodgepole pine forests. For. Sci. 45(3):333-341.

Occurrence of Moths among Habitats in a Mixed Mesophytic Forest: Implications for Management of Forest Bats - Laura S. Burford; Michael J. Lacki; Charles V. Covell (Forest Science, 1999)
We used blacklight traps during summer 1992 to index the frequency of occurrence and species composition of moths in five habitats on an actively managed, mixed mesophytic forest in eastern Kentucky. The habitats sampled were clearings, poletimber (< 30 yr old), moderate-aged sawtimber (30-50 yr old), and mature timber (70-80 yr old); the latter habitat was only available at the base of cliffs and on top of cliffs, where no harvest restrictions were in effect. We identified 4,107 moths representing 158 species and 17 families in the catches. Moths in the family Arctiidae were captured most frequently (n = 1,389), whereas moths in the family Noctuidae comprised the largest number of species (n = 53). We captured the most species (n = 83) and families (n = 17) of moths in stands of mature timber at the base of cliffs, and the fewest species (n = 57) of moths in clearings. Moths in the families Yponomeutidae, Limacodidae, Pyralidae, Geometridae, and Notodontidae were captured most frequently in stands of moderate-aged sawtimber, whereas moths in the family Arctiidae were most common in stands of moderate-aged sawtimber and poletimber. We captured moths in the family Noctuidae most frequently in stands of mature timber on top of cliffs. Moths in the families Limacodidae, Geometridae, Notodontidae, and Arctiidae were captured less frequently in clearings than other habitats, suggesting less use of clearings by moths than the other habitats sampled. These data indicate that the frequency of occurrence and species composition of moths varied among habitats in a mixed mesophytic forest in eastern Kentucky, suggesting that forest management practices can influence the diversity and abundance of moth species. These results have implications for sustaining forest biodiversity, particularly vertebrate predators that feed on moths including forest-dwelling insectivorous bats. For. Sci. 45(3):323-332.

Back Matter Volume 45 Issue 3 1999 (Forest Science, 1999)

Front Matter Volume 45 Issue 3 1999 (Forest Science, 1999)

Meeting Announcement (Forest Science, 1999)

Forest Policy: Ready for Renaissance (Forest Science, 1999)

Regional Distribution and Dynamics of Coarse Woody Debris in Midwestern Old-Growth Forests - Martin A. Spetich; Stephen R. Shifley; George R. Parker (Forest Science, 1999)
Old-growth forests have been noted for containing significant quantities of deadwood. However, there has been no coordinated effort to quantify the deadwood component of old-growth remnants across large regions of temperate deciduous forest. We present results of a regional inventory that quantifies and examines regional and temporal trends for deadwood in upland old-growth forest remnants within Indiana, Illinois, Missouri, and Iowa. From 1992 to 1994, down wood ≥ 10 cm in diameter and standing trees ≥ 10 cm dbh were inventoried on 328 one-tenth ha plots at 12 sites. The mean ratio among the sites by diameter class of the number of standing dead to standing live trees (dead/live ratio) ranged from 0.08 to 0.11 and was consistent for trees ≤ 65 cm in diameter. The dead/live tree ratio was generally greater for old-growth than for mature second-growth forests (70 to 90 yr old). Mean volume of standing dead trees across all old-growth sites was 21.4 m³/ha and down wood was 60.4 m³/ha. However, both standing and down wood volume (total deadwood) increased along a regional gradient of increasing productivity from southwest Missouri to northeast Indiana and also increased with increasing age of dominant and codominant trees. Old-growth forests on high productivity sites averaged more pieces/ha of down wood in all diameter classes and higher volume/ha of down wood in nearly all diameter classes than did old-growth forests on low productivity sites. A chronosequence of forests from 10 yr to more than 200 yr since stand establishment indicated a sharply declining down wood volume from age 10 to 70 yr followed by increasing volume between 80 and 200 yr. For. Sci. 45(2):302-313.

An Analysis of Monte Carlo Integer Programming, Simulated Annealing, and Tabu Search Heuristics for Solving Spatial Harvest Scheduling Problems - Kevin Boston; Pete Bettinger (Forest Science, 1999)
Heuristics are commonly used to solve spatial harvest scheduling problems. They can generate spatially and temporally feasible solutions to large problems that traditional mathematical programming techniques are unable to solve. A common complaint about heuristics is that the quality of the solutions is unknown. We compared three heuristic techniques commonly used to solve spatial harvest scheduling problems: Monte Carlo integer programming, simulated annealing, and tabu search. Five hundred solutions to four problems, which had between 3000 to 5000 0-1 integer variables, were generated with each heuristic technique. In addition to the heuristic solutions, the optimal solution value was found to each problem using integer programming. Simulated annealing found the highest solution value for three of the four planning problems, and was less than 1% from the highest objective function value in the fourth problem. Tabu search located the best solution for the fourth planning problem. Monte Carlo integer programming had the lowest objective function for all four problems. Tabu search had the smallest range of solutions, followed by simulated annealing. Monte Carlo integer programming had the largest range of solutions. Using the Anderson-Darling statistics, the hypothesis that the solutions from each heuristic technique were distributed as a Weibull distribution was rejected for 10 of the 12 set of values. For the two solutions where the Weibull distribution was not rejected, the estimated optimal solution was found to be an unreliable estimate of the actual optimal solution. It appears that the reliability of using extreme value statistics to estimate the optimal solution is dependent on the quality of solutions generated by the heuristic procedure. For. Sci. 45(2):292-301.

Optimal Public Harvesting Under the Interdependence of Public and Private Forests - Erkki Koskela; Markku Ollikainen (Forest Science, 1999)
This article studies the design of optimal public harvesting in an economy with multiple-use forestry and private timber supply, where amenity services of public forests are public goods but, depending on access restrictions, those of private forests may or may not be. Public and private forest stands are assumed to be either substitutes, independents, or complements in the valuation of amenity services, and public and private forests are perfect substitutes as factors of production in forest industry. Under exogenous timber prices and free access, public harvesting should be used only if the marginal willingness to pay to forego public harvesting is sufficiently less than that of private harvesting. Public harvesting with no access reduces to a situation where private and public forests are independents under free access. Allowing for endogenous timber prices with free access increases the desirability of public harvesting, while having no impact under no access. Public harvesting should be set to equate the marginal costs of public harvesting corrected for the change in private timber supply and its marginal benefits due to price changes. For. Sci. 45(2):259-271.

Spatially Optimizing Wildlife Habitat Edge Effects in Forest Management Linear and Mixed-Integer Programs - Michael Bevers; John Hof (Forest Science, 1999)
We present a spatial optimization model that accounts for wildlife edge effects through multiple habitat needs in a multistand forest management problem. Wildlife population dynamics are based on discrete reaction-diffusion processes combined with multiple limiting-factor constraint sets, one for nest site capacity and another for effective forage capacity. The model is shown to reasonably represent both negative and positive effects of forest edges on wildlife by varying the amount of forage production from harvested and unharvested forest areas in a static formulation. A dynamic model is also demonstrated, and scale effects are examined using mixed-integer programming. For. Sci. 45(2):249-258.

Forecasting Adoption and Substitution of Successive Generations of Structural Wood Panel Products in the United States - Steven R. Shook (Forest Science, 1999)
A sizable body of literature concerned with technological substitution modeling exists within the domain of forest products. These models have generally been used to develop market share forecasts for various forest products and their substitutes based on relative product prices. Substitution models usually assume that the potential market size is known and that products can freely substitute for one another. A small but growing literature concerned with the diffusion of innovations also exists within the domain of forest products. This diffusion literature typically focuses on factors affecting consumer acceptance for product innovations and forecasting the level of demand growth without constraining the potential market size. In this paper, we examine the dynamic sales behavior of three and four successive generations of structural wood panel products using varying forms of a multigeneration diffusion model. The multigeneration diffusion model introduced here, which encompasses the elements of diffusion and substitution modeling, assumes that a new structural wood panel product will diffuse through a population of potential consumers over time and that market share competition will be introduced with successive generations of structural wood panels. It is important to note that our results are contingent upon the use of domestic production data, which is used as a proxy for domestic consumption. In other words, our results do not factor in net imports. Estimation results indicate that market share competition between various structural wood panel products are differentially impacted by substitution and diffusion effects. We explore the managerial implications of the model results and suggest alternative multigeneration diffusion models that could be developed for structural wood panel products. For. Sci. 45(2):232-248.

An Adjustable Predictor of Crown Profile for Stand-Grown Douglas-Fir Trees - David W. Hann (Forest Science, 1999)
This study developed a method for predicting the crown profile of stand-grown trees that can be adjusted to other populations of the same species by using either measurements or predictions of the largest crown width (LCW) for trees in the alternative population. The method should be of particular interest for tree species such as Douglas-fir that have exhibited variation in crown attributes across both their geographic range and genotypes. To model crown profile, the crown was divided into two segments: the portion of the crown above the point where LCW occurs, and the portion below that point. The equation for the upper portion predicted a crown profile that ranged in shape from nearly conic to parabolic, depending on position within the crown and the social status of the tree, as indicated by the ratio of total height divided by diameter at breast height for the tree. The equation for the lower portion predicted a crown profile with a cylindrical shape. This method explained nearly 94% of the variation in crown width when used with the felled tree measurement of LCW, 87% with a measurement of LCW taken while the tree was standing, and 83% with the use of a value for LCW that was predicted from an equation developed from an independent data set. For. Sci. 45(2):217-225.

Selecting Loblolly Pine Parents for Seed Orchards to Minimize the Cost of Producing Pulp - W. J. Lowe; T. D. Byram; F. E. Bridgwater (Forest Science, 1999)
Southern pine cooperative breeding programs currently emphasize genetic improvement of growth rates. When a deployment population, typically a seed orchard, is established, there is an opportunity to emphasize traits other than growth rate to maximize the profit of individual cooperators in the breeding program. We studied a Southeast Texas breeding population and developed selection indexes to optimize profits for Kraft and mechanical pulp mills. The relative economic weights for volume and wood density were 1:8.1 and 1:8.6 for Kraft and mechanical pulp mills, respectively. Choosing parents with these indexes increased expected profit per ton of dry pulp by 3.4% for both mill types. Expected gains in profit were 3.3% when parents were chosen based on wood density alone. If parents were chosen based solely on volume growth, expected gains in profit were only 0.3%--0.4%. For. Sci. 45(2): 213-216.

Combining a Decomposition Strategy with Dynamic Programming to Solve Spatially Constrained Forest Management Scheduling Problems - José G. Borges; Howard M. Hoganson; Dietmar W. Rose (Forest Science, 1999)
A decomposition approach to solve the forest management scheduling adjacency problem is developed for application to large forests. Overlapping subproblems amenable to exact dynamic programming solution are solved sequentially. A heuristic is used to define and link subproblems such that near-optimal solutions to the master problem are obtained. Both the contrasting size and the irregular shape of stands complicate the problem of formulating the dynamic programming network. Subproblem size and the sequencing of stands for each corresponding dynamic programming network are defined simultaneously, as model size is especially sensitive to stand sequencing. Emphasis is on efficient dynamic programming formulations to allow for large subproblems. Results from over 100 test computer runs are discussed for applications to 3 large problems. Results suggest that the strategy can consistently produce near-optimal solutions at reasonable computational cost. A procedure is developed to derive three slightly different adjacency problems so that the optimal solution can be found. Results for applications to the modified problems show that the proposed heuristic's solutions were within 0.01, 0.04, and 0.01% of the optimal solution, respectively. The proposed solution method consistently outperformed two other heuristics that were applied. For. Sci. 45(1):201-212.

Realized Gain and Prediction of Yield with Genetically Improved Pinus radiata in New Zealand - Susan D. Carson; Oscar Garcia; Judy D. Hayes (Forest Science, 1999)
Pinus radiata D. Don seedlots of varying genetic quality were compared in block-plot genetic-gain trials at 10 locations representing most of the site types in New Zealand. Permanent sample plots were measured annually for growth from age 6-8 yr from planting to ages 15-17 (midrotation). Seedlots from first-generation open-pollinated seed orchards and a mix of crosses that all involved the top-performing parent were, respectively, on average 4.5% and 5.3% taller and had 6% and 11% larger mean diameter, 12% and 30% more basal area, and 15% and 34% more stem volume than seedlots originating from mild mass selection in harvested stands ("climbing select"). The observed growth increases were quantified as changes in the rate of growth from that predicted by preexisting growth models in order to account for tree size and stocking differences. Seedlots from first-generation seed orchards and crosses of the top clone, respectively, grew 5.1% and 4.5% faster in height, and functions for basal area and stocking changed 13% and 26.4% faster, respectively, than the baseline growth models, which were based on climbing select. This implies that increased basal area growth must be taken into account in order to obtain accurate prediction of gain in stem volume. The incorporation of these observed increases in growth rates into stand growth models as "genetic-gain multipliers" in order to extrapolate predictions of growth of genetically improved seedlots beyond the sites, silvicultures, and seedlots represented in the genetic gain trials is discussed. For. Sci. 45(2):186-200.

Afforestation as a Real Option: Some Policy Implications - Bo Jellesmark Thorsen (Forest Science, 1999)
The theory of real options is applied to the decision of establishing a new forest stand. Assuming that afforestation costs are known and constant and that future net prices of roundwood follow a Geometric Brownian Motion, a simple model of the decision problem is formulated. Using this model, a real option analysis of the afforestation opportunity is performed. Next, the implications of the real option approach for afforestation subsidy schemes are analyzed. It is found that the subsidies needed to induce a desired investment behavior will in general increase, and that the actual increment will depend on the way subsidies are offered to the landowners and affect their expectations. An empirical example is used to illustrate the potential significance of the findings. For. Sci. 45(2):171-178.

Estimating Economic Gains for Landowners Due to Time-Dependent Changes in Biotechnology - John E. Wagner; Thomas P. Holmes (Forest Science, 1999)
This paper presents a model for examining the economic value of biotechnological research given time-dependent changes in biotechnology. Previous papers examined this issue assuming a time-neutral change in biotechnology. However, when analyzing the genetic improvements of increasing a tree's resistance to a pathogen, this assumption is untenable. We derive analytical expressions for the optimal rotation age given non-constant changes in biotechnology. Our model is then implemented using (1) growth and yield simulations, (2) optimal rotation calculations, and (3) survey data on genetic resistance of slash pine (Pinus elliottii) to fusiform rust. Non-parametric regression models are used to estimate the economic gain functions which, for the cases considered, averaged about 1% of forestland value per year. For. Sci. 45(2):163-170.

Back Matter Volume 45 Issue 2 1999 (Forest Science, 1999)

Front Matter Volume 45 Issue 2 1999 (Forest Science, 1999)

Effect of Western Spruce Budworm Defoliation on the Physiology and Growth of Potted Douglas-Fir Seedlings - Thomas E. Kolb; Kimberly A. Dodds; Karen M. Clancy (Forest Science, 1999)
Interactions between effects of insect defoliators on tree physiology and growth and soil nutrient and water availability are poorly understood. We addressed whether the western spruce budworm influences nutrient and water relations, ectomycorrhizae, leaf gas exchange, and growth of Douglas-fir seedlings under different environmental conditions. Four-year-old, potted seedlings were grown in two soil types (basalt-derived, limestone-derived) with two levels of soil moisture (high, low) and were subjected to three levels of budworm defoliation (none, moderate, heavy) and two levels of frass and litter produced by budworm feeding (with, without) over 2 yr in a greenhouse environment. Defoliation, soil moisture, and soil type influenced allocation of seedling biomass to leaves, stems, and roots. The addition of frass and litter had no effect on any measured soil or tree characteristic. Interactions between defoliation and other experimental factors were not important except for the defoliation x soil moisture interaction where heavy defoliation reduced the negative effects of low soil moisture on seedling predawn water potential, net photosynthetic rate, and stomatal conductance. Heavily defoliated seedlings had less biomass, higher foliar concentrations of N, Ca, and Mg, less ectomycorrhizae, and higher net photosynthetic rate and stomatal conductance compared with nondefoliated seedlings. For. Sci. 45(2):280-291.

Projecting Timber Inventory at the Product Level - Lawrence Teeter; Xiaoping Zhou (Forest Science, 1999)
Current timber inventory projections generally lack information on inventory by product classes. Most models available for inventory projection and linked to supply analyses are limited to projecting aggregate softwood and hardwood. The research presented describes a methodology for distributing the volume on each FIA (USDA Forest Service Forest Inventory and Analysis) survey plot to product classes given a type characterization, volume, and average dbh (diameter at breast height, 1.37 m above average ground level) for the plot. A multinomial logit model was developed to estimate sets of product proportion functions to distribute plot volumes by product class for each forest type and size class. A discussion of the performance of the model using Alabama and Mississippi FIA plot level data is provided. For. Sci. 45(1):226-231.

Silvicultural Contracting in British Columbia: A Transaction Cost Economics Analysis - Sen Wang; G. C. Van Kooten (Forest Science, 1999)
In the light of institutional reforms to British Columbia's forestry sector, this study investigates forest companies' decisions to contract out silvicultural activities or to perform them in-house. A model is developed to test the relationship between a firm's choice of contractual forms and (a) the attributes of the activity (e.g., specificity of technical skills and physical assets, frequency of operations, and uncertainty in controlling performance quality) and (b) characteristics of the firm (e.g., company size). Data from a survey of forest companies in the Province are used to test several hypotheses. The empirical results confirm the transaction cost logic that silvicultural activities performed in-house are likely those that are complex to manage, have a low degree of seasonality, require high levels of human skills, and involve highly specialized physical assets. For. Sci. 45(2):272-279.

Composite and Calibration Estimation Following 3P Sampling - Timothy G. Gregoire; Harry T. Valentine (Forest Science, 1999)
Two alternatives to the generalized ratio estimator, i.e., Grosenbaugh's 3PSEVENTH, are studied. Both make more complete use of auxiliary information which is available at the conclusion of 3P sampling. Both appear to be more biased but more accurate than 3PSEVENTH. For. Sci. 45(2):179-185.

Meeting Announcements (Forest Science, 1999)

Upcoming Book Reviews (Forest Science, 1999)

Brief Notices (Forest Science, 1999)

Book Reviews: Tropical Moist Forest Silviculture and Management: A History of Success and Failure - Jacob L. Whitmore (Forest Science, 1999)

Book Reviews: Ecological Scale: Theory and Applications - Janet L. Ohmann (Forest Science, 1999)

Nutritional and Sexual Responses of Jack Pine to Ammonium Nitrate and Gibberellins - W.H. Fogal; G.R. Larocque; S.M. Lopushanski; H.O. Schooley; M.L. Anderson; I.K. Edwards; S.J. Coleman; M.S. Wolynetz (Forest Science, 1999)
The nutritional and sexual responses of jack pine (Pinus banksiana Lamb.) seed orchard trees to NH4NO3 fertilization and GA4/7 foliar sprays were examined in seedling and grafted orchards at an Ontario location where soils were low N acidic sandy loams and in a Saskatchewan grafted orchard on high N calcareous sandy clay loams. High seed strobilus abortion and low pollen strobilus production and seed yields characterized the Saskatchewan trees. NH4NO3 fertilizer increased soil NH4+ and NO3- at both locations, current-year needle N and Mg in Ontario, Fe in Saskatchewan, and Ca at both locations, seed strobilus initiation and seed yields in Ontario; it decreased K in Saskatchewan. GA4/7 increased needle senescence and current-year needle N and P at both locations, K at Saskatchewan, seed and pollen strobilus initiation in Ontario, seed strobilus initiation and abortion in Saskatchewan, and seed yields per tree in Ontario; it decreased Ca at both locations, Mg at Saskatchewan, and diameter increments the year following treatments in Ontario. NH4NO3 and GA4/7 treatments did not interact for strobilus counts. Sexual expression varied with clones in Saskatchewan but not with families in Ontario. Clones interacted with GA4/7 but not NH4NO3 for seed strobilus initiation. For. Sci. 45(1):136-153.

Mexican Spotted Owl Home Range and Habitat Use in Pine-Oak Forest: Implications for Forest Management - Joseph L. Ganey; William M. Block; Jeffrey S. Jenness; Randolph A. Wilson (Forest Science, 1999)
To better understand the habitat relationships of the Mexican spotted owl (Strix occidentalis lucida), and how such relationships might influence forest management, we studied home-range and habitat use of radio-marked owls in ponderosa pine (Pinus ponderosa)-Gambel oak (Quercus gambelii) forest. Annual home-range size (95% adaptive-kernel estimate) averaged 895 ha ± + 70 (SE) for 12 individuals and 997 ha ± 186 (SE) for 7 pairs of owls. On average, the 75% adaptive-kernel contour (a probability contour containing 75% of the owl locations) included 32 and 30% of the annual home range for individuals and pairs, respectively, suggesting high concentration of activity in a relatively small portion of the home range. Relative area of three cover types (ponderosa pine forest, pine-oak forest, and meadow) did not differ between seasonal ranges, and owls used these cover types in proportion to their relative area during both breeding and nonbreeding seasons. In contrast, relative area of four canopy-cover classes varied between seasons. Breeding-season ranges contained greater proportions of areas with canopy cover ≥ 60% and lower proportions of areas with 20-39% canopy cover than nonbreeding-season ranges. Owls roosted and foraged in stands with ≥ 60% canopy cover more than expected during both breeding and nonbreeding seasons, and used stands with 20-39% canopy cover less than expected except for foraging during the breeding season. Stands used for foraging did not differ in structure between seasons and had greater canopy cover and less rock cover than stands with no documented use. Stands used for roosting differed between seasons in a multivariate comparison, but no individual habitat variables differed between seasons in subsequent univariate comparisons. In both seasons, stands used for roosting had greater canopy cover than stands with no roosting use. Closed-canopy forests, which were used heavily by owls, were relatively rare on the study area, suggesting that such forests warrant special protection in areas managed for spotted owls. This may conflict with efforts to restore more open conditions in ponderosa pine forests. For. Sci. 45(1):127-135.

Three-Year Survival and Growth of Douglas-Fir Seedlings Under Various Vegetation-Free Regimes - R. Rose; J.S. Ketchum; D. E. Hanson (Forest Science, 1999)
Responses of Douglas-fir seedlings were studied for 3 yr following eight vegetation-control treatments in three western Oregon clearcuts. The objectives were to determine seedling growth response to different areas of spot vegetation control and to determine the relative influence of early woody and herbaceous competition on seedling growth. Herbicide treatment areas varied in size from those receiving no control to full control (9.3 m2). Controlled areas were maintained free of herbaceous vegetation for 2 yr and all woody vegetation was controlled for 3 yr. Two additional treatments, complete control of woody vegetation only and complete control of herbaceous vegetation only, were also examined. On two sites (Summit and Marcola), seedling growth parameters were maximized at or near full vegetation control with a tree spacing of 3 m x 3 m. On the third site (Pedee), maximum growth response occurred between 5 and 6 m2; of control. Herbaceous vegetation control resulted in increased seedling growth at all sites while woody vegetation control yielded increased seedling growth only at the Pedee site. Cumulative 3 yr herbaceous cover accounted for 68% and 41% of the variability in stem volume at Summit and Marcola, respectively. Adding cumulative 3 yr woody cover to the model accounted for an additional 18% and 49% of the variability in stem volume at Summit and Marcola, respectively. At Pedee, neither herbaceous nor woody cover significantly influenced 3 yr stem volume, suggesting that factors other than vegetation cover were responsible for differences measured. For. Sci. 45(1):117-126.

A Linear Programming, Tabu Search Method for Solving Forest-Level Bucking Optimization Problems - Andre Laroze (Forest Science, 1999)
The forest-level bucking optimization problem consists of determining the bucking program that maximizes the global profit subject to demand constraints, merchandising restrictions, and forest-estate. A Linear Programming-Tabu Search (LP/TS) method was developed for obtaining near-optimal, rule-based solutions to this problem. TS is used for generating an efficient bucking rule for every stand and merchandising restrictions considered. The LP model is used for determining the area of each stand that should be allocated to each merchandising alternative (and by doing so selecting the bucking rule defined for the corresponding specifications). The goal is to capture the synergy that can be obtained by combining logs from different sources that are produced applying different production guidelines. The results obtained for several estate, price, and demand conditions indicate that the LP/TS method consistently achieves an efficiency level of approximately 97% compared to the optimal solution for the same scenarios. Considering that the simplicity of the bucking rules offers an important operational advantage (Laroze and Greber 1997), the method developed for this study represents an interesting approach for solving forest-level bucking problems. For. Sci. 45(1):108-116.

Within-Stem Variation in Tropolone Content and Decay Resistance of Second-Growth Western Redcedar - Jeffrey D. DeBell; Jeffrey J. Morrell; Barbara L. Gartner (Forest Science, 1999)
Western redcedar (Thuja plicata Donn) is a commercial species valued for its high decay resistance, which is due to the presence of toxic extractives (tropolones) in the heartwood. We measured tropolone content and weight loss in soil block tests using samples taken from 11 second-growth western redcedar trees. Tropolone content increased with rings from the pith, and in the outer heartwood, increased from the top to the base of the tree. We did not find any consistent increase or decrease in tropolone content with height in the tree for samples the same number of rings from the pith. Our data suggest that the lower tropolone content near the pith is largely a juvenile effect, associated with wood formed near the active crown. This has implications for choosing a rotation length if wood of uniformly high decay resistance is desired, because younger trees contain a greater proportion of wood close to the pith. However, we also found large tree-to-tree differences in the rate of tropolone increase with age from the pith. This may have promise for maintaining uniformly high decay resistance if the factors underlying the tree-to-tree differences can be discovered and managed. Our results from soil block tests for decay resistance were more variable, but in general, wood near the pith, which was low in tropolones throughout the tree, was extremely variable in decay resistance; outer heartwood with high tropolone content showed higher, less variable decay resistance, while outer heartwood with low tropolone content remained variable in decay resistance. For. Sci. 45(1):101-107.

Back Matter Volume 45 Issue 1 1999 (Forest Science, 1999)

Front Matter Volume 45 Issue 1 1999 (Forest Science, 1999)

Compatible Volume and Taper Models with Coefficients for Tropical Species on Hainan Island in Southern China - Zixing Fang; Robert L. Bailey (Forest Science, 1999)
Compatibility of a volume-taper equation system is generally defined to mean that volumes determined by integrating the taper curve from groundline to total tree height are algebraically identical to those obtained from the total volume or appropriate volume ratio equations. This constraint was applied to a previously published model as a boundary condition using the constant of integration resulting from the solution of the differential equation. Four cases are discussed that apply to different solutions of the differential equation. This set of models, all based on the same geometric assumption, makes a very flexible system for modeling stem taper. We fitted the resulting taper models and corresponding tip volume equations simultaneously to stem-measurement data for 23 tropical species growing on Hainan Island in southern China. The simplest case among the four (case I-a) was acceptable for some species, but for some others, a more general case (case II-b) was needed. We compared the results for the simplest and the most general cases of this system with a published geometric model having only a point constraint at dbh and with a published variable exponent taper equation. We examined how well each one predicted upper-stem diameters, merchantable height for a given upper-stem diameter, and total stem volume. Our taper models always had the smallest bias and standard error of estimates for total volume estimation. The variable exponent taper equation was the best for predicting upper-stem diameter and merchantable height. The advantages of a taper system with a geometric rationale are discussed, and two examples of easy extensions of our taper model are shown in the appendix. For. Sci. 45(1):85-100.

Spatial Restrictions in Harvest Scheduling - Alan T. Murray (Forest Science, 1999)
Forest resource use has traditionally been multifaceted. In order to ensure that these resources continue to be available for use by current and future generations, sustainable management practices are essential for striking a balance between the varied and often competing demands associated with forest use. This has meant that analysis incorporate specific objectives and considerations aimed at minimizing the impacts of forest activities. One such management planning approach has been the inclusion of spatial restrictions in harvest scheduling analysis. This article reviews two basic harvest scheduling models which may be used for imposing spatial restrictions. Distinctions between the alternative methods are highlighted and operational considerations are discussed. This article establishes and outlines priority areas for future harvest scheduling research. For. Sci. 45(1): 45-52.

Basal Area Growth and Crown Closure in a Loblolly Pine Spacing Trial - Philip J. Radtke; Harold E. Burkhart (Forest Science, 1999)
Data collected after each of the first 13 yr since planting of a loblolly pine spacing trial were used to study relationships between basal area growth and crown closure. Crown closure and crown competition factor at the inflection age of cumulative basal area growth were examined on 192 plots of varying initial density and rectangularity at four sites in the Piedmont and the Atlantic Coastal Plain. Inflection age increased with initial growing space, but at a decreasing rate, presumably approaching some maximum value that would be realized in the absence of all competition. The inflection generally occurred earlier on study sites with the highest site index values, but exceptions to this trend were observed. The degree of crown closure at the inflection age increased with planting density, but did not depend in a meaningful way on the site index of the study sites. Crown competition factor at the inflection age increased with planting density, but also increased with site index. Rectangularity did not significantly affect the inflection age, but it did reduce the level of crown closure at that age. A test for the effect of rectangularity on crown competition factor was inconclusive. For. Sci. 45(1):35-44.

Simulation of Thinning with a Single-Grip Harvester - Lars Eliasson (Forest Science, 1999)
A simulation model of a single-grip harvester was constructed to evaluate different silvicultural treatments and to compare different machine concepts with a minimum of confounding factors. The model simulates machine movement, boom movement, felling, delimbing, and cross-cutting in stands where both size and position of each tree are known. To validate the model, model output was compared with data from recent time studies. Effects on harvester productivity of three harvesting intensities (extraction of 30, 40, and 50% of the basal area when thinning from below) and four distances between machine positions were studied. Productivity increased with harvesting intensity and with distance between machine positions. For. Sci. 45(1):26-34.

Long-Term Dynamics of Lodgepole Needle Miner Populations in Central Oregon - Richard R. Mason; H.Gene Paul (Forest Science, 1999)
A 30 yr time series of larval densities of lodgepole needle miner (Coleotechnites sp. nr. milleri[Busck][Lepidoptera:Gelechiidae]) populations in central Oregon was analyzed. The series included parts of two needle miner outbreaks and an extended interval between outbreaks when populations were at low densities. Complete data sets and subsets were examined by conventional methods of population and time-series analysis to detect patterns of needle miner abundance and to determine the feedback structure of the series. A 141 yr tree-ring chronology also was constructed for the same area from which the regional history of needle miner outbreaks was determined. Analyses revealed two kinds of concurrent cycles: 8 to 10 yr oscillations of needle miner densities apparently caused by time delays in the regulatory (density-dependent) feedback effect of natural enemies, and recurrent outbreaks at 20 to 25 yr dependent on overall recovery rate of the population between outbreaks and the degree of tree susceptibility to infestation. In general, populations fluctuated around an equilibrium determined by favorability of the local environment for population increase. The equilibrium density was many times higher for a needle miner population on a site with high-risk trees than for populations elsewhere. It is hypothesized that accelerated thinning and harvesting of lodgepole pine and stand-replacing outbreaks of mountain pine beetle (Dendroctonus ponderosae Hopkins) between 1970 and 1990 increased the overall resistance of lodgepole stands to infestation and prevented an isolated outbreak in the 1990s from being more widespread. For. Sci. 45(1):15-25.

A Methodology to Analyze Divergent Case Studies of Non-Timber Forest Products and Their Development Potential - Manuel Ruiz Pérez; Neil Byron (Forest Science, 1999)
Debate currently rages over the development potential of Non-Timber Forest Products (NTFP) in tropical forests. Proponents of particular "solutions" can refer to evidence (case studies, data) which tend to support their interpretation of events and relationships. Recommendations thus frequently depend on how data are classified and interpreted. Inaccurate or incomplete classification leads to defective subsequent theories, models, and recommendations. We present a method for classifying very divergent case-study data, and some initial results as a basis for general understanding of key factors that influence a given result. Crucial issues determining outcomes of NTFP development include the nature of government involvement, distribution of property rights, the ability of local people to claim and enforce such rights, market transparency, and pressure on the resource. This paper concludes with suggestions for further testing and development of the methodology. For. Sci. 45(1):1-14.

Evaluation of the Barr & Stroud FP15 and Criterion 400 Laser Dendrometers for Measuring Upper Stem Diameters and Heights - Michael S. Williams; Kenneth L. Cormier; Ronald G. Briggs; Donald L. Martinez (Forest Science, 1999)
Calibrated Barr & Stroud FP15 and Criterion 400 laser dendrometers were tested for reliability in measuring upper stem diameters and heights under typical field conditions. Data were collected in the Black Hills National Forest, which covers parts of South Dakota and Wyoming in the United States. Mixed effects models were employed to account for differences between users of the dendrometers and to test for significant differences between the heights and diameters measured indirectly (by dendrometer) and directly (by caliper and linear tape). The location at which measurements were taken on each tree was determined by paint marks along the bole. No significant differences between users were found. The Barr & Stroud consistently overestimated diameters by approximately 0.3 cm (0.1 in). Unbiased estimates of diameter were obtained with the Criterion 400. For height measurements, neither the Barr & Stroud nor the Criterion 400 produced unbiased measurements. The effect of distance to the base of the tree and height of the diameter measurement on the variability of the measurements was also studied. As distance increased, the variability of diameter measurements increased for both dendrometers. For the measurement of height, only the Barr & Stroud exhibited an increase in the variability of measurements with increasing distance. After correcting the data for their biases, taper equations were fitted to them and analyzed. The equations generated from the Barr & Stroud were not significantly different from those generated from direct measurement, unlike the Criterion 400 where taper equations generated were statistically different. A brief study of the effects of familiarity with each dendrometer indicated that the measurement error and variability decreased as the user became more familiar with the Criterion. This was not the case for the Barr & Stroud. For. Sci. 45(1):53-61.

Tree Mortality Following Defoliation by the European Gypsy Moth (Lymantria dispar L.) in the United States: A Review - Christopher B. Davidson; Kurt W. Gottschalk; James E. Johnson (Forest Science, 1999)
This review presents information related to defoliation by the European gypsy moth (Lymantria dispar L.) and subsequent tree mortality in the eastern United States. The literature describing defoliation-induced tree mortality is extensive, yet questions still remain concerning (1) the association between initial stand composition and subsequent tree mortality, (2) the influence of site quality on tree mortality, and (3) observed differences between mortality rates in initial and subsequent outbreaks. Our review and analysis of the available literature indicates that initial species composition affects subsequent defoliation. Stands with predominantly susceptible host species have higher levels of species-specific and total mortality than mixed stands of susceptible, resistant, and immune host species. Differences in mortality on sites of varying productivity do not appear to be a direct result of site quality; rather, site quality indirectly influences mortality rates through its effect on species composition and therefore defoliation. Differences between initial and subsequent outbreaks appear to be due primarily to losses of vulnerable oaks and lower canopy species during the initial outbreak; oak mortality in initial outbreaks was found to be significantly greater (P = 0.0727) than oak mortality in subsequent outbreaks. For. Sci. 45(1):74-84.

Stakeholder Perspectives on Appropriate Forest Management in the Pacific Northwest - Anne R. Kearney; Gordon Bradley; Rachel Kaplan; Stephen Kaplan (Forest Science, 1999)
One potential source of the controversy over forest management in the Pacific Northwest is differences in stakeholders' conceptualizations, or perspectives, on appropriate forest management. This study explores the nature of stakeholders' perspectives and identifies some of the differences and commonalities among them. Study participants included 23 individuals from 3 forest stakeholder groups: the USDA Forest Service, timber industry, and environmentalists. Participants' perspectives on appropriate forest management were assessed using a conceptual content cognitive map (3CM) task. Results indicate the existence of a wide range of concerns including issues related to the focus, setting, and process of management. The pattern of differences and similarities among stakeholder groups with respect to these concerns was found to be complex and to deviate substantially from common stereotypes. In addition, participants' perceptions of the other stakeholder groups were found to be highly stereotypical and were not supported by the data. For. Sci. 45(1):62-73.

1998 Contents (Forest Science, 1998)

1998 Author Index (Forest Science, 1998)

1998 Subject Index (Forest Science, 1998)

Meeting Announcements (Forest Science, 1998)

Brief Notice (Forest Science, 1998)

Upcoming Book Reviews (Forest Science, 1998)

The Science of Conservation Planning: Habitat Conservation Under the Endangered Species Act - Katherine Ralls (Forest Science, 1998)

Book Reviews: Placing Nature: Culture and Landscape Ecology - Taylor V. Stein (Forest Science, 1998)

Survival and Growth of Seedlings of Four Bottomland Oak Species in Response to Increases in Flooding and Salinity - William H. Conner; Kenneth W. McLeod; James K. McCarron (Forest Science, 1998)
Four oak species representing a range of flood tolerance were chronically (simulating sea level rise) and acutely (simulating hurricane storm surge) exposed to increased flooding and salinity in a complete factorial experiment. Survival, growth, and final biomass were measured to assess differential species' responses. No Nuttall or overcup oak seedlings died when flooded with fresh water, but 10% of the swamp chestnut and 35% of the water oaks died. Floodwater salinities of 2 and 6 g L-1 resulted in mortality of all seedlings of all four species. Watering with 2 g L-1 saline water did not cause any mortality although leaf browning was evident in all species. Overcup oak seedlings were the most tolerant to watering with 6 g L-1 saline water (100% survival), while the other three species had high mortality. Increased salinity, both in watered and flooded conditions, generally resulted in decreased diameter growth and decreased root and shoot biomass. Short-term increases in salinity (simulated storm surge) resulted in total mortality of flooded seedlings, while drained seedlings recovered and leafed out the following spring. Results indicate that these bottomland oak species would be seriously affected by increased flooding and salinity from either hurricane storm surges or sea level rise. For. Sci. 44(4):618-624.

Analyzing Consistency of Experts' Judgments—Case of Assessing Forest Biodiversity - Jyrki Kangas; Juha M. Alho; Osmo Kolehmainen; Ari Mononen (Forest Science, 1998)
Incorporation of biodiversity considerations into forest planning requires methods for the operationalization of biodiversity and for the quantification of expert judgments concerning the future implications of alternative forest management plans. Applying expert knowledge in numerical decision support most probably involves much uncertainty. To reduce biases, the use of several independent experts seems advisable. However, the experts may disagree, and it is not always clear whether this is due to genuine disagreements, or because of misunderstandings or other errors that may occur in the elicitation process. In this study, an approach is presented for analyzing the uncertainties in expert judgments elicited by pairwise comparisons, and for improving the consistency of judgments. Ecological expertise is applied in the estimation of an evaluation model which can be used in assessing alternative forest plans with respect to biodiversity in optimization calculations. The approach is based on the combined use of HERO optimization method developed for tactical forest planning, Delphi technique, and variance components modeling. The Delphi technique may be helpful in understanding better the causes of the possible disagreements. Variance components modeling is used to estimate the changes in the views of 11 experts concerning the different components of biodiversity, in three Delphi rounds. It turned out that the views converged to some extent, but in one case an increase in shared inconsistency among judges was also detected. For. Sci. 44(4):610-617.

Measuring Environmental Quality in the Southern Appalachian Mountains - Linwood Pendleton; Brent Sohngen; Robert Mendelsohn; Thomas Holmes (Forest Science, 1998)
This study presents a method for valuing recreational environmental quality in the forests of the southeastern United States. The paper offers a method for choosing, measuring, and valuing forest attributes. Surveys and popular recreation literature are used to identify forest attributes that contribute to recreational quality. Standard ecological techniques are employed to measure levels of these attributes along trails in Tennessee, North Carolina, and Georgia. Finally, the paper demonstrates how hedonic methods can be used to assign values to forest attributes. We show that values for recreational quality vary across users and sites. Furthermore, we demonstrate the existence of negative marginal values for certain forest attributes and provide evidence that suggests these negative values are not the result of mis-specification, but are consistent with oversatiation. For. Sci. 44(4):603-609.

Effects of Thinning and Nitrogen Fertilization on Sugars and Terpenes in Douglas-Fir Vascular Tissues: Implications for Black Bear Foraging - Bruce A. Kimball; Eric C. Turnblom; Dale L. Nolte; Doreen L. Griffin; Richard M. Engeman (Forest Science, 1998)
The chemical constituents of coniferous vascular tissues play a role in bear forage selection. In particular, bear foraging preferences are related to the concentrations of simple sugars (nonstructural carbohydrates) and terpenes in the forage. Analyses of vascular tissue samples from trees collected in test plots indicated that both thinning and fertilization caused the sugar concentration of vascular tissues in the lower bole to increase. However, these treatments had no effect on the concentrations of hydrocarbon monoterpenes, oxygenated monoterpenes, or sesquiterpenes. These results may explain the observations that black bears prefer to forage in thinned and fertilized stands. For. Sci. 44(4):599-602.

Genetic Parameters and Breeding Value Predictions for Eucalyptus Nitens Wood Fiber Production Traits - Wayne Tibbits; Gary Hodge (Forest Science, 1998)
A base breeding population of 13,000 trees from about 300 Eucalyptus nitens families of open-pollinated origin in 6 provenances of native forest stands, was established in 8 tests, analyzed for genetic parameters and used for breeding value and gain prediction. Traits considered were basal area (BA), basic density (BD), and kraft pulp yield (PY) in 4- to 8-yr-old trees. Measurement of PY, whether taken as individual trees (PYI) or composites (PYC), were considered as the same trait, since the average Type B genetic correlation (rBg) between PYI and PYC was 0.94. Trees with the "early-adult form" typically from the Errinundra provenance appeared to have the poorest PY, averaging 1 to 3% points lower than all the other provenances. This provenance was excluded from detailed genetic analyses. Significant differences among the other five provenances were found for all traits. Four provenances were reasonably similar, but northern New South Wales was estimated to be lowest for BA and PY, and highest for BD. Single-site biased heritabilities (h2b) varied substantially from site to site, and averaged 0.32 ± 0.05 for BA, 0.43 ± 0.09 for BD, 0.37 ± 0.08 for PY. Heritability estimates from combined-site analyses were 0.19 for BA, 0.42 for BD, and 0.37 for PY. Genotype x environment (g x e) interaction was estimated using rBg. For BD and PY, rBg was 0.94, indicating no major g x e. Moderate g x e interactions were detected for SA, with rBg at 0.60. Genetic correlation between BA and PY, and between BD and PY were favorable, but between BA and BD was unfavorable (genetic correlation = 0.24, 0.41 and -0.24 respectively). For. Sci. 44(4):587-598.

The Economic Impact of a Subsidy on Mexican Grains and Forestry: A CGE Analysis - Roy Boyd; Khosrow Doroodian (Forest Science, 1998)
This study first examines the economy-wide impacts of the "Pro-Campo" grains subsidy program. It then analyzes the effects of extending this program to forestry as a means of curbing further deforestation. To accomplish these objectives, we employ a computable general equilibrium (CGE) model of the Mexican economy. Our findings show that (1) the subsidies lead to a transfer of resources from the refining, natural gas, services, and financial services sectors into the various agricultural, manufacturing, and mining sectors; (2) All consumption sectors except the food and the alcohol and tobacco sectors decrease as a result of subsidies; (3) The lower income groups experience an increase in their income at the expense of the upper income groups when government revenue and expenditure are held constant. Such results suggest that extension of "Pro-Campo" benefits to the forestry sector should have the desired impact of keeping land and capital resources in forestry. Our results, however, only pertain to commercial species and do not include the off-side damages which may occur to useful noncommercial species. For. Sci. 44(4):578-586.

Economic and Fragmentation Effects of Clearcut Restrictions - T.M. Barrett; J.K. Gilless; L.S. Davis (Forest Science, 1998)
Clearcut restrictions limiting individual clearcut size affect economic outputs and alter the spatial distribution of wildlife habitat over the landscape. Simulations of different clearcutting restrictions were applied to a 47,500 ha mixed-ownership landscape in the Sierra Nevada of California. The private owner was assumed to pursue a goal of maximizing net present value (NPV), while the public owner was assumed to use a combination of low-intensity selection harvesting and long rotations to develop late-seral habitat. With a 10 yr exclusion period, maximum clearcut size limits of 4 and 32 ha reduced the private owner's NPV to 79% and 91% of the unconstrained maximum, respectively; with a 20 yr exclusion period, to 65% and 88% of the unconstrained maximum. Initially, smaller clearcut size limits resulted in more mature forest [average stand diameter (ASD) greater than 30 cm], but with greater fragmentation. Ultimately, late-seral habitat (ASD > 61 cm) was insensitive to clearcut size limits because rotation lengths of 60 or 90 yr did not produce that habitat class for most forest types. For. Sci. 44(4):569-577.

Comparative Susceptibility of Conifers to Larch Dwarf Mistletoe in the Pacific Northwest - Robert L. Mathiasen (Forest Science, 1998)
A total of 62 mixed conifer sites in Idaho, Montana, Oregon, and Washington infested with larch dwarf mistletoe (Arceuthobium laricis) were sampled to compare host susceptibility to this parasitic flowering plant. Temporary circular plots (6 m radius) were established around dominant, severely infected, principal, and secondary hosts. Within plots, species, diameter at 1.37 m above the ground, and dwarf mistletoe rating (6 class system) were determined for each live tree over 1.37 m in height. A total of 11,270 trees were sampled in 620 plots. Based on the percentage of infection, species were assigned to host susceptibility classes: western larch is the only principal host of larch dwarf mistletoe; mountain hemlock and lodgepole pine are secondary hosts; subalpine fir and ponderosa pine are occasional hosts; and Engelmann spruce, grand fir, and western white pine are rare hosts. No infection was observed on Douglas-fir, western hemlock or western redcedar. However, based on a report of larch dwarf mistletoe parasitizing western hemlock in Washington, western hemlock must be designated as a rare host. Pacific silver fir and whitebark pine are tentatively classified as occasional hosts. For. Sci. 44(4):559-568.

Tree-Ring Responses to Drought Across Species and Contrasting Sites in the Ridge and Valley of Central Pennsylvania - Marc D. Abrams; Charles M. Ruffner; Todd A. Morgan (Forest Science, 1998)
Annual tree-ring variation between 1984 and 1995 was measured in ten hardwood species in central Pennsylvania (USA) to assess differential drought impacts on xeric ridge, dry-mesic barrens, mesic valley, and wet-mesic riparian sites. Each tree species occurred on two or more sites. Four droughts of moderate to severe intensity occurred during the study period. In general, trees on the xeric ridge and wet-mesic riparian sites were more frequently impacted with reductions in the ring width index, whereas trees on the mesic valley and dry-mesic barrens sites had fewer growth reductions. Annual variation in growth was negatively correlated with summer temperature, particularly for species on the riparian site. Six of twenty-three species-by-site combinations had above average growth during one or more of the droughts, while 8 of 23 species-by-site combinations had below average growth the year following drought. The species with the largest decrease in the ring width index during drought varied among the sites, and included Acer rubrum in the valley, Prunus serotina in the barrens and riparian sites, and Quercus rubra and Acer rubrum on the ridge. Comparing tree-ring data from this study with leaf gas exchange data from other studies resulted in several inconsistencies in drought responses; therefore, information from both approaches may be needed in accurately assessing species drought tolerance rating. For. Sci. 44(4):550-558.

Using Expert Judgment to Model Initial Attack Fire Crew Effectiveness - Kelvin G. Hirsch; Paul N. Corey; David L. Martell (Forest Science, 1998)
An expert judgment elicitation methodology was developed and used to encode subjective assessments of fire crew effectiveness from experienced initial attack crew leaders. During structured individual interviews, experts from four Canadian forest fire management agencies provided assessments of the probability of fire containment (POC) by a "medium" (5- to 7-person) initial attack crew for 35 initial attack scenarios that varied in terms of fire size and head fire intensity. This repeated-measures data was used to develop individual, logistic response curves for 34 of the experts. Analysis of the coefficients of these response curves showed that fire size, fire intensity, and the interaction between size and intensity significantly influenced the POC assessments. Using data for seven ancillary variables concerning the background and experience of the experts, it was found that agency had the greatest influence on the POC estimates. Random coefficient regression modeling was used to develop composite probability of containment models for the entire data set, each agency, and suppression with and without bucketing. For. Sci. 44(4):539-549.

Using Dynamic Programming and Overlapping Subproblems to Address Adjacency in Large Harvest Scheduling Problems - Howard M. Hoganson; Jose G. Borges (Forest Science, 1998)
The adjacency problem for forest management scheduling is formulated as a dynamic programming problem. To overcome typical model-size problems, a solution strategy is proposed which links dynamic programming formulations for overlapping subproblems. Subproblems are solved sequentially in a moving-windows fashion. Solutions are near-optimal for three large but simplified test cases. Model size is sensitive to the size of the moving window. Using relatively small windows produced solutions that are closer to optimal than those found using two other modeling approaches. Solutions are also insensitive to the side of the forest used to start the moving-windows process, and microcomputer solution times are not a major consideration. The strategy offers potential to treat adjacency measures as valued management outputs. It will likely fit well into broader forestwide models which decompose the forestwide problem into parts to help address other forestwide constraints. For. Sci. 44(4):526-538.

Regional Cost Function Analysis of the Logging Industry in the Pacific Northwest and Southeast - Phillip Smith; Ian A. Munn (Forest Science, 1998)
Nonhomothetic translog cost functions with two variable inputs, labor and capital, were estimated to compare the underlying production structure of the logging industry in the Pacific Northwest and Southeast regions of the United States from 1963 to 1992. The parent cost function and capital share equation for each region were estimated using Maximum Likelihood Estimation techniques. Both equations were significantly different between regions. The industry in both regions was capital-using over the study period. Labor and capital were substitutes in each region, but substitution possibilities were limited. Input substitution was more elastic in the Southeast, and therefore the industry in the Southeast would be better able to adjust to changes in input prices or output demand. Additional tests determined that homothetic, homogeneous, and time invariant functions would be inappropriate for the logging industry in either region. For. Sci. 44(4):517-525.

Using the Non-Parametric Classifier CART to Model Forest Tree Mortality - Matthias Dobbertin; Gregory S. Biging (Forest Science, 1998)
A binary classification tree (CART) was used to predict forest tree mortality for two conifer species. CART models were fitted using binary recursive splitting of the data set into increasingly homogeneous subsets. Models were compared in terms of improvement of prediction accuracy, representativeness in average size of the predicted mortality trees, and interpretability of the results. For shade intolerant ponderosa pine, crown ratio, diameter increment prediction, or variables indicating the relative position of a tree in a stand were used for splitting. For shade tolerant white fir, height increment prediction and stand density were selected for splitting. The prediction accuracies for mortality trees of the best CART models were between 28-36% for ponderosa pine and between 11-17% for white fir. CART was also compared with logistic regression using a stochastic and a deterministic assignment of mortality. Efficiencies similar to those achieved with CART were reached with deterministic logistic models using thresholds probabilities. However, CART and the logistic model tended to utilize different predictor variables, especially for white fir. CART uncovered additional factors for white fir important for predicting mortality not identified by the logistic regression. For. Sci. 44(4):507-516.

Risk Preferences and Adaptive Harvest Policies for Even-Aged Stand Management - Peichen Gong (Forest Science, 1998)
Uncertainty in future states of nature affects the set of feasible management alternatives as well as a forest owner's preferences among different alternatives. To incorporate uncertainty into forestry decisions, both effects should be recognized simultaneously. This study concerns the final harvest decision in even-aged stand management with stochastic stumpage prices. An expected utility maximization model is developed for determining the optimal adaptive harvest policy. Instead of assuming risk-neutrality on the side of forest owners, the model explicitly incorporates risk preferences into the determination of reservation prices. A method for estimating the set of efficient adaptive harvest policies for risk-averse forest owners is developed based on the mean-variance rule and stochastic dominance analysis. The set of efficient adaptive harvest policies is estimated and compared with the set of efficient rotation ages for two example stands. Numerical results show that any risk-averse forest owner prefers the optimal adaptive harvest policy to the optimal rotation age. By using the rule of "harvest only when the observed stumpage price is equal to or higher than the reservation price," the expected net present value can be increased, and, meanwhile, the standard deviation of the net present value can be reduced significantly. Incorporation of risk-aversion leads to reservation prices that may be lower than those that maximize the expected net present value. It indicates that risk-averse forest owners typically should harvest earlier than risk-neutral forest owners. For. Sci. 44(4):496-506.

The Impact of Reserve Prices in Sealed Bid Federal Timber Sale Auctions - Douglas R. Carter; David H. Newman (Forest Science, 1998)
In this article we examine the impact of reserve prices on timber revenues from federal timber sale auctions in North Carolina from a game-theoretic perspective by recognizing the effect of competition on optimal bid strategies. The empirical model endogenizes the number of bidders in a simultaneous-equations Tobit framework, and estimates the impacts of the reserve price on the probability that an offering will sell, as well as on the sale price given that the offering is sold, in the presence of strategic bidding behavior. Model results support the underlying game-theoretic structure. The number of bidders and the reserve price are both important in determining market value or high bid. Using a Wu-Hausman test, we reject exogeneity in the number of bidders. Importantly, a calculation of the change in market value given a change in the reserve price shows that increasing reserve prices will likely increase timber revenues on sales in North Carolina, thus providing evidence that reserve prices are not optimal. However, increasing the reserve price will decrease the proportion of sold sales which may not support nontimber objectives of the Forest Service. For. Sci. 44(4):485-495.

Back Matter Volume 44 Issue 4 1998 (Forest Science, 1998)

Front Matter Volume 44 Issue 4 1998 (Forest Science, 1998)

Errata (Forest Science, 1998)

Meeting Announcements (Forest Science, 1998)

Upcoming Book Reviews (Forest Science, 1998)

Brief Notices (Forest Science, 1998)

Book Reviews: Temperate Agroforestry Systems, edited by A. M. Gordon and S.M. Newman - David E. Hibbs (Forest Science, 1998)

Book Reviews: Geographic Variation in Forest Trees, by H. K. Morgenstern - Bruce C. Bongarten (Forest Science, 1998)

Estimation of Temporal Variations in Historical Fire Frequency from Time-Since-Fire Map Data - W. J. Reed; C. P. S. Larsen; E. A. Johnson; G. M. MacDonald (Forest Science, 1998)
This paper describes an improved statistical methodology for estimating historical forest fire frequencies from time-since-fire map data. Of particular interest is the question of estimating fire frequency in temporally distinct epochs. Unlike previous graphical and ad hoc methods, the new methodology is firmly grounded within the established statistical paradigm of likelihood inference. In addition, in contrast to earlier methods, it takes into account the fact that surviving stands which originated in earlier epochs, have been subject to different hazards of burning as they have lived through more recent epochs. Neglecting this fact leads to overestimates of the fire frequency in the more recent epochs. Procedures for obtaining maximum likelihood estimates and likelihood ratio confidence intervals for the fire frequency in each epoch are developed, along with a likelihood ratio test to assess whether the fire frequencies in distinct epochs were significantly different. This test is not strictly valid when the change points separating epochs are suggested from exploratory data analysis; rather it is developed assuming that change points are determined independently of the data. This distinction, which is necessary to avoid selection bias, has not been noted before. The fact that forest fire is a contagious process, with consequent spatial autocorrelation in time-since-fire observations, is taken into account through the use of an overdispersed model, with associated quasi-likelihood function. This aspect has been ignored, by and large, in previous analyses which have implicitly assumed independence of observations. An example is given in which the method is applied to published fire history data from the Kananaskis Valley. The results indicate that the previous analysis overestimated the fire frequency for the most recent epoch. The conclusions of other studies concerning temporal changes in fire frequency may need to be reconsidered. For. Sci. 44(3):465-475.

Allometry and Growth - L. R. Broad (Forest Science, 1998)
A theory of multivariate allometry is developed. Bivariate and multivariate allometry are then shown to be compatible, the defining differential equations being analogs of each other and invariant under analogous allometric transforms. The relevance of allometric equations to growth modeling is examined. Commonly used growth models that are invariant under allometric transforms are capable of being formulated in terms of allometric (growth) differential equations. Methods for formulating and solving multivariate growth models are demonstrated. For. Sci. 44(3):458-464.

Technical Note: Nitrogen Supply, Nitrogen Use, and Production in an Age Sequence of Lodgepole Pine - Ute Olsson; Dan Binkley; F. W. Smith (Forest Science, 1998)
Forest productivity typically declines after reaching a peak early in stand development. Historically this pattern was attributed to constant or declining stand photosynthesis and increasing stand respiration, but this explanation has been largely invalidated by field measurements and modeling. Production in older stands might decline as a result of declining soil nutrient supply. To test this idea, we examined patterns of productivity and nitrogen (N) supply and use in four age classes of lodgepole pine (Pinus contorta Dougl. ex. Loud.) ecosystems in southeastern Wyoming. Aboveground net primary production (ANPP) increased from 2200 kg ha-1 yr-1 at age 30 to 4600 kg ha-1 yr-1 at age 50, then declined to 2000 kg ha-1 yr-1 at age 200. Soil N supply (indexed with ion exchange resin bags) was highest in the 30-yr-old sites, but showed no further pattern with age in older sites. The ratio of ANPP to the supply of N rose sharply from age 30 to age 50, and then declined slowly. The ratio of ANPP to the N actually taken up was high for the three youngest age classes, but declined substantially in the old-growth (200 yr) site. We conclude that the low ANPP of the old-growth stands was probably not driven by changes in stand nutrition; the decline in efficiency of N use indicates some other factor probably constrains productivity of old-growth stands. For. Sci. 44(3):454-457.

Crown Profile Modeling of Loblolly Pine by Nonparametric Regression Analysis - Paul F. Doruska; James E. Mays (Forest Science, 1998)
Crown profile of loblolly pine (Pinus taeda L.) was modeled by nonparametric regression analysis. Nonparametric regression may be applicable when an underlying parametric model cannot be identified and uses only the data to fit a curve. A class of local-polynomial estimators which contains the popular kernel estimator as a special case was investigated. Kernel regression appears to fit closely to the interior data points but often possesses bias problems at the boundaries of the data, a feature less exhibited by local linear or local quadratic regression. A selection of trees was used to show that nonparametric regression captures more variation in crown shape than multiple linear regression. When using nonparametric regression, decisions must be made regarding polynomial order and bandwidth. Such decisions depend on the presence of local curvature, desired degree of smoothing, and for bandwidth in particular, the minimization of some global error criterion. In the present study, a penalized PRESS criterion (PRESS*) was selected as the global error criterion. For. Sci. 44(3):445-453.

The Effects of Fixed-Area Plot Width on Forest Canopy Height Simulation - Ross F. Nelson; Timothy G. Gregoire; Richard G. Oderwald (Forest Science, 1998)
Mapped-stand data which includes tree location and mensuration data may be used to simulate the height characteristics of a forest canopy in a computer. The dimensions of the rectangular, fixed-area ground plot which is used to collect the tree location and mensuration data can profoundly affect the accuracy of the resultant computer reconstruction of forest canopy heights. Thin fixed-area plots result in forest canopy height constructs (i.e., canopy height models, or CHMs) which are shorter and less dense than the actual forest stand. Ninety-nine 0.405 ha forest stands in the southeastern and south central United States were analyzed. For each stand, a top-of-canopy height model was generated for the entire stand on a 0.25 m x 0.25 m grid. The mean canopy height and the canopy density of the simulated stand was calculated. A Monte Carlo simulator established randomly located sample plots of varying plot width (1 m to 20 m) at three different sampling intensities (1%, 5%, and 10% of stand area) in the mapped stand. The trees selected on any particular plot were used to generate a CHM, and the sample mean canopy height and canopy density were compared with the corresponding stand values. Samples collected using 1 m wide plots resulted in height models which underestimated average canopy height and canopy closure with deviations greater than 5% of the stand value, 95-100% of the time. The underestimation results from the construction of top-of-canopy architecture based on measurements of crowns belonging only to trees whose boles are within the plot. This construction technique omits crowns extending over the plot belonging to tree boles located off the plot. Thinner plots tend to miss more of the trees which support the canopy over the plot. For the 99 stands considered in this study, ground plot widths on the order of 6 to 8 m were required in order to acquire ground data which could be used to accurately model forest canopy height characteristics. The minimum ground plot width required to produce an accurate height model decreased with increasing stem density; a plot width of 4 m, for instance, may be used at stem densities of ~2000 stems ha-1. For. Sci. 44(3):438-444.

Development and Evaluation of Habitat Models for Herpetofauna and Small Mammals - William M. Block; Michael L. Morrison; Peter E. Scott (Forest Science, 1998)
We evaluated the ability of discriminant analysis (DA), logistic regression (LR), and multiple regression (MR) to describe habitat use by amphibians, reptiles, and small mammals found in California oak woodlands. We also compared models derived from pitfall and live trapping data for several species. Habitat relations modeled by DA and LR produced similar results, averaging about 70% classification success of the trapping stations to the correct group (capture or noncapture habitat). Although more variables were included in DA (4-5) than in LR (2-3), those included in LR were typically a subset of those in DA. On average, MR habitat models accounted for 56% of the variation in the index of relative species' abundance. The variables included in the MR models were seldom the same as those for DA and LR. Most differences between MR and the other two methods were related to differences in spatial scale: MR modeled habitat among grids, whereas DA and LR modeled habitat within grids. Habitat models for the same species differed between the trapping methods used. Live traps are most useful for describing general habitat relations of some small mammal species across large geographic areas, whereas pitfall traps are useful for intensive sampling of a larger portion of the vertebrate community within smaller geographic areas. Thus, the choice of trapping methods must be based on the study goals, biology of the species, and the spatial scale of study. For. Sci. 44(3):430-437.

Analyzing Public Inputs to Multiple Objective Decisions on National Forests Using Conjoint Analysis - Donald F. Dennis (Forest Science, 1998)
Faced with multiple objectives, national forest managers and planners need a means to solicit and analyze public preferences and values. A conjoint ranking survey was designed to solicit public preferences for various levels of timber harvesting, wildlife habitats, hiking trails, snowmobile use, and off-road-vehicle (ORV) access on the Green Mountain National Forest. The survey was completed by 76 respondents during public involvement meetings. An ordered probit model was used to estimate linear and quadratic main effects. Respondents preferred moderate levels of timber harvesting and snowmobile access and lower levels of ORV access. They favored a mixture of mature closed canopy and younger more open forests over either extreme and were somewhat indifferent toward extending the network of hiking trails. For. Sci. 44(3):421-428.

Survival of Hemlock Woolly Adelgid (Homoptera: Adelgidae) at Low Temperatures - Bruce L. Parker; Margaret Skinner; Svetlana Gouli; Takamaru Ashikaga; H. Brenton Teillon (Forest Science, 1998)
The hemlock woolly adelgid (Adelges tsugae Annand [Homoptera: Adelgidae]) (HWA), a nonnative insect, is a major threat to New England forest and suburban environments, where one of its hosts, eastern hemlock, Tsuga canadensis (L.) Carrière, is a dominant native tree species. To determine the potential spread of HWA into northern New England, we studied the winter coldhardiness of a northerly population. Sistens were collected at three times during the winter and subjected to temperatures typical of those during winter in the next coldest USDA plant coldhardiness zone. Samples collected in January and February 1996 were subjected to -20, -25, and -30°C; those collected in March to -15, -20, and -25°C; all date-temperature treatments were tested at exposure times of 1, 2, 4, 8, and 24 hr. When all exposure times were combined, the percentage of live adelgids after subzero treatment (adjusted for control mortality at 0°C) declined significantly as temperature decreased. In most cases, fewer HWA were alive after treatment as exposure time increased. Significantly more HWA collected in January were alive after treatment than those collected in February and March. This suggests that HWA coldhardiness declines over this time period. When comparing the percentage of live HWA from February and March for -20 and -25°C, a noticeable decline occurred between the February and March sample dates. Although mortality was as high as 95% in one of the most severe treatments (February collection exposed to -30°C for 24 hr), the fact that complete mortality did not occur suggests that HWA may be able to continue to expand its range into areas with colder winters. For. Sci. 44(3):414-420.

Standard Errors of Area Estimates Obtained by Traversing and GPS - Lennart Bondesson; Göran Ståhl; Sören Holm (Forest Science, 1998)
In this article, the problem of determining standard errors of area estimates obtained by traversing is addressed. In traversing, a surveyor moves along the boundary of a compartment and makes measurements at certain base points to determine their coordinates. Two cases of traversing are described: the case when coordinates are determined directly using GPS equipment and the case when distances and directions are measured from every base point to the next. It is shown that the problem of determining standard errors of the area estimates is different for the two cases. Formulas are derived from basic assumptions about the measurement errors. The efficiency of the two approaches is compared. It is found that the standard errors for the two methods often are of a similar magnitude but that the size and the shape of a compartment affect what method should be preferred. For. Sci. 44(3):405-413.

Influence of Plant Density and Soil Organic Matter on the First-Year Growth of Loblolly Pine and Sweetgum - Bruce R. Zutter; Glenn R. Glover; Robert J. Mitchell (Forest Science, 1998)
Loblolly pine (Pinus taeda L.) and sweetgum (Liquidambar styraciflua L.) seedlings were planted at a range of densities on a formerly cultivated field which varied in soil organic matter (soil OM) in the upper 15 cm of the soil. Mean aboveground biomass per plant at the end of one growing season was examined to see how it varied as a function of plant density and soil OM. Biomass per plant as a function of density, holding soil OM constant, was described well by a reparameterized form of a standard yield density equation. A simple linear equation suitably described per plant biomass as a function of soil OM, holding density constant. Effects of soil OM on biomass were positive for both species, with sweetgum exhibiting a stronger response than loblolly pine. Based on the results of fitting equations to single factors, an equation considering both density and soil OM was developed and fitted using all data for each species. The equations explained 85% of the variation in response for both species. The inclusion of soil OM was more important in describing response of sweetgum than for loblolly pine. Inclusion of both density and soil OM in a single equation to describe mean response of plants in a monoculture might be extended to a mixture of species and used to examine intraspecific and interspecific competitive effects of competition and their relationship with productivity. For. Sci. 44(3):397-404.

Impact of Alternative Regeneration Methods on Genetic Diversity in Coastal Douglas-Fir - W. Thomas Adams; Jinghua Zuo; Jarbas Y. Shimizu; John C. Tappeiner (Forest Science, 1998)
Genetic implications of natural and artificial regeneration following three regeneration methods (group selection, shelterwood, and clearcut) were investigated in coastal Douglas-fir (Pseudotsuga menziesii var. menziesii [Mirb.] Franco) using genetic markers (17 allozyme loci). In general, harvesting followed by either natural or artificial regeneration resulted in offspring populations little altered from those in the previous generation. Cutting the smallest trees to form shelterwoods, however, resulted in the removal of rare, presumably deleterious, alleles, such that slightly fewer alleles per locus were observed among residual trees (2.76) and natural regeneration (2.75) than found in uncut (control) stands (2.86). Thus, although the shelterwood regime appears quite compatible with gene conservation, it would be best to leave parent trees of a range of sizes in shelterwoods designated as gene conservation reserves, in order to maximize the number of alleles (regardless of current adaptive value) in naturally regenerated offspring. Seedling stocks used for artificial regeneration in clearcut, shelterwood, and group selection stands (7 total) had significantly greater levels of genetic diversity, on average, than found in natural regeneration. This is probably because the seeds used in artificial seedling stocks came from many wild stands and thus, sampled more diversity than found in single populations. For. Sci. 44(3): 390-396.

Segmenting the Market for Environmentally Certified Wood Products - Lucie K. Ozanne; Paul M. Smith (Forest Science, 1998)
A study was conducted to segment consumers in terms of their attitudes toward environmentally certified wood products. Factor analysis reduced seven variables of environmental certification to two distinct factors. Cluster analysis, performed on the seven variables of forest and wood products certification, suggested the existence of six relatively homogeneous groupings or segments of consumers. Multiple discriminant analysis provided a method for profiling these six consumer segments in terms of demographic, attitudinal, and trust (respondent's trust in potential certifying organizations) variables. This paper identifies one consumer segment of approximately 25 million Americans who would most likely seek out environmentally certified wood products. Relative to our other study respondents, they can be described as politically liberal, Democrats, female, members of an environmental organization, fairly well educated, concerned about the quality of the environment and forest resources, and having high self-rated environmental knowledge. In addition, these respondents would place the most trust in the certification claims made by an environmental organization. Conversely, a consumer segment of nearly 10 million Americans appears highly skeptical of certification programs, in general. Consistent with previous literature, our demographic variables were less effective in discriminating among groupings of consumers than attitudinal and trust variables. Implications of segmentation strategies are discussed for both industrial managers and forest policymakers. For. Sci. 44(3):379-389.

Efficiency Implications of Silvicultural Expenditures from Separating Ownership and Management on Forest Lands - Martin K. Luckert (Forest Science, 1998)
In pursuing silvicultural goals on licensed public lands, governments worldwide have adopted various policy instruments including contractual requirements, the reimbursement of silvicultural costs, and investment incentives in the form of shares in the value of timber crops resulting from voluntary silvicultural activities. Monte Carlo simulations are used to investigate the efficiency implications of alternative silvicultural policy options. Results indicate that current policies, dominated by requirements and reimbursements with uncertain costs, may create significantly less wealth than policies that include some share of future timber crops. Means of granting shares include reimbursing tenure holders according to the present value of the future benefits created by their expenditures or by sharecropping arrangements. Such policies could potentially provide tenure holders with incentives to efficiently invest in silvicultural activities, by alleviating tenure insecurity while correcting for market failures. For. Sci. 44(3):365-378.

Determining the Optimal Planting Density and Land Expectation Value--A Numerical Evaluation of Decision Model - Peichen Gong (Forest Science, 1998)
Different decision models can be constructed and used to analyze a regeneration decision in even-aged stand management. However, the optimal decision and management outcomes determined in an analysis may depend on the decision model used in the analysis. This paper examines the proper choice of decision model for determining the optimal planting density and land expectation value (LEV) for a Scots pine (Pinus sylvestris L.) plantation in northern Sweden. First, a general adaptive decision model for determining the regeneration alternative that maximizes the LEV is presented. This model recognizes future stand state and timber price uncertainties by including multiple stand state and timber price scenarios, and assumes that the harvest decision in each future period will be made conditional on the observed stand state and timber prices. Alternative assumptions about future stand states, timber prices, and harvest decisions can be incorporated into this general decision model, resulting in several different decision models that can be used to analyze a specific regeneration problem. Next, the consequences of choosing different modeling assumptions are determined using the example Scots pine plantation problem. Numerical results show that the most important sources of uncertainty that affect the optimal planting density and LEV are variations of the optimal clearcut time due to short-term fluctuations of timber prices. It is appropriate to determine the optimal planting density and harvest policy using an adaptive decision model that recognizes uncertainty only in future timber prices. After the optimal decisions have been found, however, the LEV should be re-estimated by incorporating both future stand state and timber price uncertainties. For. Sci. 44(3):356-364.

Mixed Conifer Forest Mortality and Establishment Before and After Prescribed Fire in Sequoia National Park, California - Linda S. Mutch; David J. Parsons (Forest Science, 1998)
Pre- and post-burn tree mortality rates, size structure, basal area, and ingrowth were determined for four 1.0 ha mixed conifer forest stands in the Log Creek and Tharp's Creek watersheds of Sequoia National Park. Mean annual mortality between 1986 and 1990 was 0.8% for both watersheds. In the fall of 1990, the Tharp's Creek watershed was treated with a prescribed burn. Between 1991 and 1995, mean annual mortality was 1.4% in the unburned Log Creek watershed and 17.2% in the burned Tharp's Creek watershed. A drought from 1987 to 1992 likely contributed to the mortality increase in the Log Creek watershed. The high mortality in the Tharp's Creek watershed was primarily related to crown scorch from the 1990 fire and was modeled with logistic regression for white fir (Abies concolor [Gord. and Glend.]) and sugar pine (Pinus lambertiana [Dougl.]). From 1989 to 1994, basal area declined an average of 5% per year in the burned Tharp's Creek watershed, compared to average annual increases of less than 1% per year in the unburned Log Creek watershed and in the Tharp's watershed prior to burning. Post-burn size structure was dramatically changed in the Tharp's Creek stands: 75% of trees ≤50 cm and 25% of trees >50 cm were killed by the fire. For. Sci. 44(2):341-355.

Back Matter Volume 44 Issue 3 1998 (Forest Science, 1998)

Front Matter Volume 44 Issue 3 1998 (Forest Science, 1998)

Errata (Forest Science, 1998)

Upcoming Book Reviews (Forest Science, 1998)

Brief Notices (Forest Science, 1998)

Meeting Announcements (Forest Science, 1998)

Book Reviews: The Idea of Biodiversity: Philosophies of Paradise, by D. Takacs - Peter A. Jordan (Forest Science, 1998)

Book Reviews: Fundamentals of the Physical Environment, by D. Briggs, P. Smithson, K. Addison, and K. Atkinson - Douglas W. Waldren (Forest Science, 1998)

Book Reviews: Northern Forested Wetlands: Ecology and Management, Edited by C.C Trettin, M.F. Jurgensen, D.F. Grigal, M.R. Gale, and J. K. Jeglum - Aram J. K. Calhoun (Forest Science, 1998)

Leaf Area and Above- and Belowground Growth Responses of Loblolly Pine to Nutrient and Water Additions - Timothy J. Albaugh; H. Lee Allen; Phillip M. Dougherty; Lance W. Kress; John S. King (Forest Science, 1998)
A 2 x 2 nutrient and water factorial experiment with four replications was installed in an 8-yr-old stand of loblolly pine (Pinus taeda L.) growing on an infertile, excessively drained sandy site in Scotland County, North Carolina. After the fourth year of treatment, estimated stem volume increment, total biomass production, and peak leaf area index (LAI) increased 152%, 99%, and 101%, respectively, with fertilization and 25%, 23%, 16%, respectively, with irrigation. Stem volume growth efficiency (growth per unit LAI) increased 21% with fertilization, 9% with irrigation, and 30% with both fertilization and irrigation. Total biomass production efficiency increased 91% with fertilization, 29% with irrigation, and 120% with both fertilization and irrigation. The observed increase in stem volume growth efficiency may have been due, in part, to changes in biomass partitioning. However, altered partitioning patterns alone did not explain the observed increase in total biomass production efficiency. We hypothesized that the change in total biomass production efficiency may have been a result of greater allocation to foliage (photosynthesizing tissue) and less allocation to fine roots (a high maintenance respiration tissue) under fertilization and irrigation treatments. For. Sci. 44(2):317-328.

Influence of Intensive Culture on Leaf Net Photosynthesis and Growth of Sweetgum and Loblolly Pine Seedlings - L. J. Samuelson (Forest Science, 1998)
The influence of (1) complete weed control only, (2) weed control and irrigation, (3) weed control and irrigation with a fertilizer solution (fertigation), and (4) weed control and fertigation plus pest suppression (pine only) on midday light-saturated leaf net photosynthesis (Pn) of sweetgum (Liquidambar styraciflua L.) and loblolly pine (Pinus taeda L.) was examined monthly, two growing seasons after plantation establishment. Irrigation but not fertigation increased Pn on all dates and more than doubled height and diameter of sweetgum after the first growing season. Greater Pn in sweetgum in response to irrigation was, in part, a result of reductions in stomatal limitation to Pn and decreased stomatal sensitivity to vapor pressure deficit. In loblolly pine, Pn was increased only by irrigation and only on one date during the first growing season. No effect of treatment on Pn of either species was observed for the second season. After two growing seasons, an eight-fold increase in aboveground biomass and six-fold increase in leaf area were observed in sweetgum in response to fertigation relative to the control treatment. Fertigation plus pest control treatment eliminated tip moth damage to shoots of loblolly pine during the first growing season and resulted in a doubling of total biomass and tripling of leaf area. Maximum biomass accumulation in sweetgum and loblolly pine after two seasons of intensive culture was mainly a function of leaf area rather than Pn For. Sci. 44(2):308-316.

Measuring the Efficiency of Public Forestry Organizations - Esa-Jussi Viitala; Harri Hänninen (Forest Science, 1998)
The decreasing budgets of public forestry organizations have given rise to the present need to evaluate their efficiency and to find means to improve it. In this paper the efficiency of 19 state-funded, regional Forestry Boards is investigated using Data Envelopment Analysis (DEA). In addition, the prime determinants of efficiency are examined using Tobit models. The results indicate a substantial variation in efficiency across Forestry Boards with a potential for input saving in the range of 20%. It seems that, of the controllable factors, management style and support are associated with efficiency. It appears also that applying DEA with Tobit models provides a useful two-stage approach to assess and explain efficiency differences among public forestry organizations. For. Sci. 44(2):298-307.

Modeling the Basal Area-size Distribution of Forest Stands: A Compatible Approach - Jeffrey H. Gove; Ganapathi P. Patil (Forest Science, 1998)
This paper presents a methodology that allows diameter distributions to be conformably modeled by letting the probability density represent either tree frequency as in the classic case, or basal area. The key to relating the two forms of the probability density is shown to lie in weighted distribution theory. The motivation for the relationship lies in the quadratic relationship between diameter at breast height and basal area. The weighted distribution approach is shown to be compatible with current methods of calculating quantities such as basal area by diameter class, but in addition, affords the development of new equations useful in parameter recovery or similar modeling strategies. Relationships are developed for all of the major distributions found to have been useful in forestry for fitting diameter distribution models. Several stands to which the two- and three-parameter Weibull distributions have been fitted are also presented. For. Sci. 44(2):285-297.

Reconciling Multivariate Calibrations of Volume Estimates in Two-Phase Forest Inventories - Steen Magnussen; Paul Boudewyn (Forest Science, 1998)
Univariate approaches to ratio of means calibration of phase I variables in two-phased forest inventories may lead to suboptimal properties when calibrated results are used in a multivariate context, as exemplified by a growth model. Application of bootstrap resampling techniques makes it possible to find a multivariate set of ratios of means with optimum properties in terms of global performance criteria. For. Sci. 44(2):266-271.

Qualitative Comparative Analysis: A Useful Tool for Research into Forest Policy and Forestry Conflicts - Eeva Hellström (Forest Science, 1998)
The internationalization of the forestry debate and forest policy brings about a growing need to develop, apply, and discuss comparative methodologies in forestry research. This paper illustrates and discusses the use of Qualitative Comparative Analysis (QCA), a new comparative tool in forest policy research. The advantages and disadvantages of the method are demonstrated by reanalyzing previous research on public environmental criticism of forestry in Finland, Sweden, Norway, West Germany, France, and the United States between 1950 and 1983. In particular, the reanalysis illustrates the potential benefits of systematic techniques of comparison as supplementary tools to traditional "common sense" interpretations of qualitative data. In addition to arguing on behalf of the technical applicability of the method to comparative forest policy research, a need is expressed to expand the use of the method from causal to noncausal applications. For. Sci. 44(2):254-265.

Use of Individual Tree Mixed Models to Account for Mortality and Selective Thinning When Estimating Base Population Genetic Parameters - Xianming Wei; Nuno M. G. Borralho (Forest Science, 1998)
The ability of individual tree mixed models to estimate unbiased genetic parameters was investigated for growth, Pilodyn penetration, and bark thickness, in an Eucalyptus urophylla progeny trial where the smaller trees have been previously thinned. A multivariate Restricted Maximum Likelihood (REML) analysis including the growth measurements of all trees prior to thinning, and later measurements of only those that remained, resulted in almost unbiased estimates of heritabilities and age-age genetic correlations for growth traits at all ages. Analysis based only on trees remaining after thinning resulted in considerably lower estimates of heritabilities and age-age genetic correlations. On the other hand, genetic parameters for Pilodyn penetration or bark thickness were not affected by the thinning. This was due to the low correlations between the thinning criteria (tree size) and the wood and bark traits. For. Sci. 44(2):246-253.

Does Thinning Affect Gypsy Moth Dynamics? - Andrew M. Liebhold; Rose-Marie Muzika; Kurt W. Gottschalk (Forest Science, 1998)
In northeastern U.S. forests there is considerable variation in susceptibility (defoliation potential) and vulnerability (tree mortality) to gypsy moth (Lymantria dispar [L.]). Thinning has been suggested as a way to reduce susceptibility and/or vulnerability. We evaluated how thinning affected the dynamics of gypsy moth populations by experimentally thinning half of each of eight oak-mixed hardwood stands in the Central Appalachians. Population dynamics of gypsy moth were monitored using yearly counts of egg masses, numbers of larvae hatching per mass, estimates of larval density, and weekly collections of larvae and pupae which were reared to quantify mortality due to parasitoids and disease. During the 8 yr study, three stands were heavily defoliated by outbreak populations of gypsy moth, three were sprayed with pesticides accidentally, and two were not disturbed. Egg-mass densities were slightly lower in the thinned portions of the undisturbed stands, but thinning had little or no effect on gypsy moth densities in defoliated and sprayed stands. Variation in mortality of gypsy moth caused by parasitoids and disease was related to variation in egg-mass densities in the current and/or preceding years. After adjusting for the effect of gypsy moth density, thinning had no significant effect on mortality from parasitoids or pathogens. We conclude that any reduction in egg mass densities as a result of thinning is likely related to the reduction in foliar biomass, not increased natural enemy activity. For. Sci. 44(2):239-245.

Adapting Distance-Independent Forest Growth Models to Represent Spatial Variability: Effects of Sampling Design on Model Coefficients - Albert R. Stage; William R. Wykoff (Forest Science, 1998)
If sampling variability of competition variables can be accommodated, a distance independent growth model can (1) simulate patchy stands inventoried by a grid of sampling locations; (2) prescribe treatments for each location; and (3) update inventories using plot sizes differing from those used in model calibration. Ignoring sampling properties of competition biases estimates of stand development and management responses. Our solution to reduce this bias has three steps: First, we model the sampling properties of the competition estimates depending on plot sizes and on spatial patterns. Then we use the modeled error variances when estimating parameters of the structural relation of growth to competition. Finally, we join these two products in a Structural Based Prediction (SBP) procedure that dynamically modifies coefficients during simulation. SBP increases sensitivity to spatial variation and permits valid analyses of location-specific prescriptions for varying inventory designs. In a model of diameter change for individual Pseudostuga menziesii var. glauca (Beissn.) Franco, coefficients of the competition variables estimated under the structural model were three times as large as when estimated under an ordinary least-squares criterion. This increase reduced sensitivity to crown ratio. Two variants of the Prognosis Model for Stand Development were constructed to compare behavioral changes: (1) using SBP, and (2) using the OLS-based coefficient estimates of the same diameter-growth submodel. Projections with the two variants differed in the internal structures of both uniform and irregular stands and using several sampling methods. Stand averages of volume growth were similar for uniform stands-either from uniform regeneration or from uniformity created by thinning patchy stands. However, the thinning response in patchy stands differed between the two variants. Analysis of the variance model showed little sensitivity within the range of half to twice the Poisson-based estimates of competition variance. For. Sci. 44(2):224-238.

Modeling Thinning Effects on Ring Specific Gravity of Loblolly Pine (Pinus taeda L.) - Gudaye Tasissa; Harold E. Burkhart (Forest Science, 1998)
Effects of thinning on ring specific gravity in loblolly pine trees were examined in a regional trial in the southeastern United States. The thinning study consisted of two treatment levels (30% and 50% of the basal area removed) and a control. Thinning did not alter the proportion of the annual ring in earlywood or latewood and thus did not affect ring specific gravity. There was regional variation in average ring specific gravity, with trees from the Coastal Plain having higher ring specific gravity than trees from the Piedmont or the Highlands. Within the Coastal Plain, trees in the Gulf Coastal Plain tended to have higher average ring specific gravity than trees in the Atlantic Coastal Plain. A ring specific gravity prediction model was developed based on ring position, tree, stand, and site attributes. Much of the variation in ring specific gravity was due to within-tree variation; consequently, stand and site factors accounted for a limited proportion of variation in ring specific gravity. As the within-tree observations used in the study tended to be correlated, a direct covariance modeling approach was used to account for the correlation among observations. For. Sci. 44(2):212-223.

The Role of Mycorrhizae, Site Preparation, and Organic Amendment in the Afforestation of a Semi-Arid Mediterranean Site with Pinus halepensis - José I. Querejeta; Antonio Roldán; Juan Albaladejo; Victor Castillo (Forest Science, 1998)
A factorial field experiment was conducted in a degraded semi-arid site of southeastern Spain to test the effectiveness of mycorrhization and several soil preparation techniques on afforestation with Pinus halepensis. The mycorrhizal treatments were nursery inoculation with Pisolithus arhizus and forest soil addition to the planting holes. The soil preparation treatments were terracing(mechanical and manual) and the addition of an organic amendment (urban solid refuse). One year after planting, the study revealed significant differences in mycorrhization levels, frequency of mycorrhizal species, fine root production and growth between the inoculated seedlings and the noninoculated controls. Inoculation with P. arhizus gave better pine growth and mycorrhization rates than the addition of forest soil. Both mycorrhization treatments were particularly effective in combination with mechanical terracing. The organic amendment had no apparent negative influence on the mycorrhization level of the seedlings and significantly improved pine growth. The beneficial effects of mycorrhization treatments on P. halepensis growth persisted 2 yr after planting. The increase in growth of the seedlings due to the treatments could be attributed to the change in soil conditions (increased fertility and soil aeration) and probably to a mycorrhization effect on water relations, although it has not been clearly demonstrated. FOR. Sci. 43(2):203-211.

The Optimal Timber Rotation: An Option Value Approach - Andrew J. Plantinga (Forest Science, 1998)
Previous analyses of the timber rotation problem under price uncertainty find that timber owners can increase the expected values of their stands by using a reservation price policy that exploits stochastic variations in prices. This result is found when the process governing prices is stationary and with nonstationary prices when there are fixed costs. This paper highlights the role of option values in influencing the optimal timing of harvests. In this context, the option value is a premium over the expected net present value of a timber stand reflecting the opportunity cost of harvesting now and foregoing the option to delay harvest until information on future stand values is revealed. With stationary prices, option values arise from two sources of forthcoming information: the level of the stumpage price relative to the long-term mean and the stand value relative to fixed costs. With nonstationary prices, option values are associated only with the latter information. This paper demonstrates analytically that reservation price policies act as a mechanism for incorporating the option value into the calculus of the optimal rotation length. Numerical simulations provide further insights into the effects of option values on rotation lengths, expected stand values, and reservation prices. For. Sci. 44(2):192-202.

Variation in Selected Wood Properties of Vochysia Guatemalensis from Four Sites in Costa Rica - Eugenio Gonzalez J.; Richard F. Fisher (Forest Science, 1998)
Vochysia guatemalensis D. Smith is distributed naturally from Mexico to Panama. It is a promising species for commercial reforestation on degraded lands, but little is known about the variation in important wood traits. Trees of this species were sampled in four natural stands to estimate the variation and radial gradients in wood specific gravity, fiber length, vessel density and vessel radial diameter. Increment cores were extracted from each tree at breast height and divided into 1 cm segments from pith to bark. Specific gravity was determined for each segment. The same wood cores were macerated for measuring fiber length. Vessel density and vessel radial diameter were measured for each segment from cross sections. Significant differences were found among sites (P < 0.05) for specific gravity and fiber length. Both of these variables also increased from pith to bark at all sites, and these radial gradients were significantly different among sites (P < 0.05). Vessel density was also significantly different among sites, but there was no significant change from pith to bark. No significant differences were detected among sites for mean vessel radial diameter; however, radial change in vessel diameter was significantly different among sites. For. Sci. 44(2):185-191.

Back Matter Volume 44 Issue 2 1998 (Forest Science, 1998)

Front Matter Volume 44 Issue 2 1998 (Forest Science, 1998)

Book Reviews: Harvesting Wild Species: Implications for Biodiversity Conservation, Edited by C.H. Freese - Stephen DeStefano (Forest Science, 1998)

Forest Harvests and Wood Products: Sources and Sinks of Atmospheric Carbon Dioxide - Jack K. Winjum; Sandra Brown; Bernhard Schlamadinger (Forest Science, 1998)
Changes in the net carbon (C) sink-source balance related to a country's forest harvesting and use of wood products is an important component in making country-level inventories of greenhouse gas emissions, a current activity within many signatory nations to the UN Framework Convention on Climate Change. We propose two approaches for estimating national C inventories from forest harvesting and wood product utilization (excluding forest regrowth): the atmospheric-flow method and the stock-change method. The former has the atmosphere as its system of interest and counts all flows to and from the atmosphere for a particular country. The latter looks at a country's forest and wood product C stocks and how they change over time. Here we develop these two methods, and estimate national C source-sink balance from the readily available FAO global forest products database for countries, regions, and the world. Both methods gave a worldwide estimated source of 980 Tg of C in 1990 as a result of forest harvests and wood product utilization; about 60% came from developing countries and 40% from developed countries. Estimates (Tg C) for selected developing countries for the atmospheric-flow/stock-change method were: Brazil, 72/73; India, 81/80; Indonesia, 53/56; and Ivory Coast, 3.9/4.3; and for selected developed countries (again atmospheric-flow/stock-change method): Canada, 36/50; Finland, 8.8/13; New Zealand, 2.7/3.4; and United States 141/138. Net wood exporters show lower numbers in the atmospheric-flow method, net wood importers in the stock-change method. Among the variables that most consistently and strongly affected C emissions for a given country in 1990 were: roundwood production, slash left to oxidize, and commodity wood put into uses ≥ 5 yr. We conclude with a discussion that shows how choosing either one of the two methods for wood harvest accounting has potential policy implications or impacts on the incentives or disincentives to use wood. For. Sci. 44(2):272-284.

Book Reviews: Achieving Sustainable Development (Sustainability and the Environment Series), by A. Dale and J.B. Robinson - William White (Forest Science, 1998)

Book Reviews: Plant Collectors in Madagascar and the Comoro Islands - Blair Orr (Forest Science, 1998)

Book Reviews: Applications of Physiological Ecology to Forest Management - R. E. Dickson; J. G. Isebrands (Forest Science, 1998)

Book Reviews: Beech Forests - Christopher A. Nowak (Forest Science, 1998)

The Design of Second Best Forest Incentives in Small Open Economies - Gregory S. Amacher; Monica Rios; Luis Constanino; Richard J. Brazee (Forest Science, 1998)
In this article, we examine the design and choice of forest incentives under second best conditions. The government faces constraints on uses of funds, the government has decided to use a subsidy system despite the welfare costs that exist with these programs, and the government has different preferences for landowner income, nontimber benefits production, and revenue generation. In particular, we examine how government preferences affect the decision to use harvest tax exemptions and the decision to subsidize expansion of the forest tax base through forest conversion. A new approach to studying forest incentive design is proposed where the government is treated as the decision maker and chooses policies to maximize welfare of the forest sector subject to its revenue constraint. This approach allows investigation of efficient reform in an existing forest subsidy system. For an empirical application of the model, we use data from Chile's forest sector to determine short-run dead weight losses of existing subsidies as a basis for reform recommendations. The basic approach in the article should be useful in predicting the behavior of revenue constrained governments. For. Sci 44(1):165-175.

Long-Term Trends in Height Growth of Jack Pine in North Central Ontario - J.C. G. Goelz; T. E. Burk (Forest Science, 1998)
Although most investigations of long-term growth trends of trees involve description of radial growth of trees, investigation of height growth of dominant and codominant trees also warrants attention for two significant reasons--the dependent variable is largely independent of stand density and it represents an index of stand productivity. Residuals from a height growth equation for jack pine (Pinus banksiana Lamb.) were used to examine long-term trends in height growth. No consistent long-term trend was apparent; however, a period of superior growth was identified during the 1960s. Short-term changes in climatic variables could account for a short duration of increased growth. As anthropogenic factors, such as air pollution, did not exhibit a trend coincident with the growth trend, they do not represent a reasonable explanation. An additional benefit of detailed examination of trends in residuals is the ability to uncover misidentification of models. The examination may suggest an inappropriate form for the equation was used, or may suggest that important variables are missing from the model. For. Sci. 44(1):158-164.

Measuring Softwood Lumber Value: A Conjoint Analysis Approach - Vijay S. Reddy; Robert J. Bush (Forest Science, 1998)
Conjoint analysis was used to determine softwood lumber value perceptions among buyers of wood for preservative treatment and to determine trade-offs between lumber attributes and price. Utility functions for each lumber attribute and a model to estimate overall lumber value were developed. Wane was found to be the most important attribute in the evaluation of lumber value, followed by price, accuracy of grading, damage to the lumber package, lumber straightness, and lumber moisture content (in that order). Utility scores of individual respondents and simulation techniques were used to quantify trade-offs between quality and price. Buyers of softwood lumber for preservative treatment were found to be willing to pay a higher price to obtain wane-free lumber. The results of the study provide guidelines for softwood lumber suppliers seeking to differentiate their product while maximizing customer-perceived product value. For. Sci. 44(1):145-157.

Effects of Plant Growth-Promoting Rhizobacteria on Loblolly and Slash Pine Seedlings - S. A. Enebak; G. Wei; J. W. Kloepper (Forest Science, 1998)
Loblolly and slash pine seed were inoculated at sowing with 1 of 12 different strains of plant growth-promoting rhizobacteria (PGPR) in the greenhouse. Time to germination and seedling densities were determined at 21 days, and seedling biomass was measured at 12 wk after sowing. All bacterial strains significantly increased the speed of seedling emergence over nontreated pine seed. By 12 wk, however, no differences in stand densities were observed between bacteria-treated and nontreated seed for either pine species. Postemergence damping-off was reduced in loblolly pine when seed was treated with 3 of the 12 bacterial strains; however, postemergence damping-off on slash pine seedlings was not affected by rhizobacteria. Treatment with rhizobacteria had a significant positive and negative effect on seedling growth and biomass, which depended on tree species. Loblolly pine shoot and root lengths, as well as the above- and belowground biomass, were significantly reduced when seeds were treated with strains BS1 and BS2. In contrast, loblolly pine seeds treated with strains BS3, PM2, and INR7 significantly increased the below ground biomass of the seedling root systems. Slash pine seedlings had similar interactions with the bacterial strains. Strain BS1 significantly reduced shoot lengths compared with nontreated seeds, while strains 90-166, INR7, and SE49 increased shoot biomass. Slash pine root lengths and biomass were also reduced when treated with strains BS1 and BS2. Unlike loblolly pine, no bacterial strain increased slash pine root length or biomass. This study suggests that the effects of rhizobacteria inoculation on seedling emergence and plant growth are independent and that the effects are species specific. For. Sci. 44(1):139-144.

Bayesian Analysis of the Linear Model with Heterogeneous Variance - Edwin J. Green; Harry T. Valentine (Forest Science, 1998)
Linear models are among the most common statistical tools in forestry, and indeed in all science. It is widely known that when linear models are applied to attributes of size (e.g., individual tree volumes), the conditional variance may be heterogeneous. Under these circumstances, the usual least squares estimator remains consistent, but is no longer efficient. This has been appreciated in forestry for some time, and various solutions have been recommended over the years. In this paper, we propose a Bayesian solution. Bayesians would prefer this method to previous solutions for many reasons. However, even non-Bayesians may wish to consider the method as it yields (as will be shown) solutions quite close to the maximum likelihood solution, along with the marginal posterior distribution of each parameter. For. Sci. 44(1):134-138.

Reconstructing the Spatial Pattern of Trees from Routine Stand Examination Measurements - Mark L. Hanus; David W. Hann; David D. Marshall (Forest Science, 1998)
Reconstruction of the spatial pattern of trees is important for the accurate visual display of unmapped stands. The proposed process for generating the spatial pattern is a nonsimple sequential inhibition process, with the inhibition zone proportionate to the scaled maximum crown width of an open-grown tree of the same species and same diameter at breast height as the subject tree. The results of this coordinate generation procedure are compared with mapped stem data from nine natural stands of Douglas-fir at two ages by the use of a transformed Ripley's K(d) function. The results of this comparison indicate that the proposed method, based on complete tree lists, successfully replicated the spatial patterns of the trees in all nine stands at both ages and over the range of distances examined. On the basis of these findings and the procedure's ability to model effects through time, the nonsimple sequential inhibition process has been chosen to generate tree coordinates in the VIZ4ST computer program for displaying forest stand structure in naturally regenerated young Douglas-fir stands. For. Sci. 44(1):125-133.

Modeling the Dynamics and Species Composition of a Tropical Mixed-Species Uneven-Aged Natural Forest: Effects of Alternative Cutting Regimes - Vincent Favrichon (Forest Science, 1998)
Sustainable tropical rain forest management is currently the subject of strong interest. There are only a few experimental stations available to research the impact of forest management (especially logging practices) on stand growth. This study develops a quantitative model to describe and simulate the dynamics of an undisturbed stand, as well as a logged uneven-aged, multispecies stand in French Guiana. This is a management-oriented matrix model. It takes into account three main characteristics of the forest dynamics in this type of ecosystem. First, we estimated density-dependence by nonlinear regression of the dynamics parameters (growth, mortality, and ingrowth). Second, a site effect is introduced on the assumption that the stand density in a natural stand is an approximate site characteristic and may help define the steady state corresponding to undisturbed conditions. Third, the very high species diversity is reduced by combining species into five groups based on growth behavior with reference to shade tolerance and maximum potential size. The model has been validated with short-term as well as medium-term projections. It was used to assess the stability of such a stand. We also evaluated the biological sustainability of logging practices, that is, the ability to return to the steady state in terms of total density as well as species composition. For. Sci. 44(1):113-124.

Back Matter Volume 44 Issue 1 1998 (Forest Science, 1998)

Front Matter Volume 44 Issue 1 1998 (Forest Science, 1998)

Ensuring the Compatibility of Aquatic Habitat and Commodity Production Goals in Eastern Oregon with a Tabu Search Procedure - Pete Bettinger; John Sessions; K. Norman Johnson (Forest Science, 1998)
We present a land management scheduling model for ensuring the compatibility of aquatic habitat quality and commodity production goals in forest management. This model uses Tabu search procedures to select feasible land management activities (timber harvesting and road system management) subject to an even-flow constraint and aquatic habitat quality goals, as represented by stream sediment and temperature indices. The methodology for evaluating the effects of land management activities on the realization of aquatic habitat goals utilizes established procedures, yet makes evaluations with each incremental decision choice. We apply the procedures to a 5,926 ha case study watershed in eastern Oregon to evaluate the performance. For comparison, a global optimum solution is estimated using extreme value theory techniques. Results show that all solutions are spatially and temporally feasible with respect to stream sediment and temperature index goals. Eighty percent of solutions had net present values within 10% of an estimated optimal solution. Further, out of 20 independent runs, one was within 2% of an estimated global optimum, and all 20 were within 15% of the estimated global optimum. While improvements to the model can be made, we have demonstrated that moderately complex aquatic habitat quality evaluation techniques, with spatial elements, can be nested inside a land management scheduling model. For. Sci. 44(1):96-112.

Estimating Tree Grades for Southern Appalachian Natural Forest Stands - Jeffrey P. Prestemon (Forest Science, 1998)
Log prices can vary significantly by grade: grade 1 logs are often several times the price per unit of grade 3 logs. Because tree grading rules derive from log grading rules, a model that predicts tree grades based on tree and stand-level variables might be useful for predicting stand values. The model could then assist in the modeling of timber supply and in economic optimization. Grade models are estimated for ten species groups found in the southern Appalachians, using data from several thousand trees and permanent plots in the USDA Forest Service's Forest Inventory and Analysis (FIA) database. The models correctly predicted grades of a majority of trees in both a test and a validation data set, and predictions of grade proportions across a sample of the population were usually within three percentage points of actual grade proportions. But success of models varied across species and diameter groups. Considering several measures of modeling success, the most accurate models were those predicting tree grades for softwoods and larger hardwoods. For. Sci. 44(1):73-86.

Canopy Dynamics, Light Interception, and Radiation Use Efficiency of Selected Loblolly Pine Families - R. L. McCrady; E. J. Jokela (Forest Science, 1998)
Needlefall, aboveground net primary production (ANPP), canopy light interception and attenuation, and "radiation use efficiency" of five open-pollinated loblolly pine (Pinus taeda L.) families were investigated using 100-tree family block plots near Summerville, SC. Family variation in annual needlefall amounts was significant during the fourth (from 4796 to 6191 kg ha-1) and fifth growing seasons (from 4717 to 5721 kg ha-1); needlefall patterns for the poorest performing family were asynchronous from those of the others, with notably higher needlefall rates from April to July. Estimates of ANPP at age 4 yr varied by 16% (from 32.9 to 38.2 Mg ha-1) among families, and were generally commensurate with progeny test rankings based on height growth. The relationship between ANPP and leaf area index (LAI) was both significant and curvilinear, with an apparent optimum level of production (42.6 Mg ha-1) achieved at a LAI of about 13 (all-sided; February). The least productive families had the lowest mean LAI (e.g., 7.9), while the most productive families generally had higher levels of LAI (e.g., 13.6). Significant family differences in canopy light interception were present in every month sampled except June, when photosynthetically active radiation (PAR) interception exceeded 90% for all families. Light extinction coefficients (k) for February differed significantly among the five families, and ranged from 0.28 to 0.38; families with the largest LAIs generally had the lowest values of k and the highest levels of PAR interception. A strong linear relationship (r² = 0.74) was found between ANPP and intercepted PAR. Estimates of the dry matter:radiation quotient (ε "radiation use efficiency") differed significantly among families, and ranged from 1.33 g MJ-1 to 1.48 g MJ-1. Results of this study suggest that fundamental differences exist in production ecology among loblolly pine families, and that canopy-level characteristics such as LAI, PAR interception, and "radiation use efficiency" are important in conferring differential family performance. For. Sci. 44(1):64-72.

Transect Relascope Sampling--A Method for the Quantification of Coarse Woody Debris - Göran Ståhl (Forest Science, 1998)
A method for the quantification of coarse woody debris in terms of the total length of downed material is presented. The method combines relascope and line intersect sampling theory. Estimation is based on a count of downed logs using a relascope instrument along survey lines. In cost-efficiency comparisons with line intersect and circular plot sampling, the proposed method was found to be a competitive alternative. For. Sci. 44(1):58-63.

Modeling Timber Harvest Scheduling Problems with Multiple Criteria: An Application in Spain - Luis Díaz-Balteiro; Carlos Romero (Forest Science, 1998)
This paper presents a multicriteria procedure for forest planning problems. The basic ingredients of this procedure are multigoal programming, compromise programming, and results connecting the best-compromise solutions with the concept of utility optima. The main feature of the procedure lies in the easy and transparent utility interpretation of some single best-compromise solutions even when the utility function, as is usual in a forestry context, is virtually unknown. The theoretical developments are applied to a timber harvest scheduling problem in Spain. The criteria considered are: (a) the net present value of the forest over the planning horizon, (b) the equality of harvest volume in each cutting period, (c) the area control criterion which looks for an ending regulated or even-aged forest, and (d) the ending inventory restraint. The preferential weights incorporated into the models are derived from the application of the Analytical Hierarchy Process (AHP) method to a group of experts in forestry matters. Several utility formulations are tested: (1) a separable and additive utility function linear in each criterion (i.e., a compromise solution for metric 1); (2) a Rawlsian utility function where the maximum deviation is minimized (i.e., a compromise solution for metric ∞) and (3) a family of quasi-Rawlsian utility functions. For. Sci. 44(1):47-57.

Modeling Dominant Height Growth: Eucalyptus Plantations in Portugal - Ana Amaro; David Reed; Margarida Tomé; Isabel Themido (Forest Science, 1998)
Difference forms of the well-known Chapman-Richards and Lundqvist-Korf biological growth models are derived for use in modeling dominant height growth using data from remeasured permanent plots. The performance of these models is compared with the performance of the McDill-Amateis difference model for describing dominant height growth of eucalyptus plantations in Portugal. The final model is a difference form of the Chapman-Richards equation with the m shape parameter constrained by initial stand conditions. The model is regional in that there are different estimated parameter values for highly productive sites in the coastal region of Portugal compared to lower productivity sites in the interior. The effect of using overlapping or nonoverlapping measurement intervals in the estimation process is examined with independent data; there appears to be little difference in the predictive ability of the resulting models. For. Sci. 44(1):37-46.

A Comparison of Timber Market Models: Static Simulation and Optimal Control Approaches - Brent Sohngen; Roger Sedjo (Forest Science, 1998)
In this paper, we compare and contrast two types of timber models that have been used to analyze the market impacts of policy proposals or exogenous forces that affect timber markets. The framework and theory for static simulation and optimal control models are presented and discussed. We then compare single region, empirical versions of the models across six scenarios of exogenous economic shocks. The models are found to predict different outcomes for timber market behavior when demand changes, or when young timber is affected by a supply shock. Similar outcomes between the models are obtained when older timber stocks are affected by shocks, or when the exogenous forces impact timber markets gradually over time. For. Sci. 44(1):24-36.

The Law of One Price in United Kingdom Soft Sawnwood Imports--A Cointegration Approach - Riitta H. Hänninen (Forest Science, 1998)
The law of one price states that prices of homogenous commodities, defined in a common currency, are equal throughout the world. It implies cointegration of prices. In the present study, the law was tested for imports of soft sawnwood to the United Kingdom from Finland, Sweden, Canada, and Russia using the concept of cointegration. The data are quarterly and cover the period 1978-1992. The study used the multivariate cointegration method of Johansen instead of the bivariate method commonly used in earlier studies. The existence of the law was tested simultaneously for all four import prices and separately for pairs of prices. The results do not support the "law" but instead indicate the existence of differences over the long run between different suppliers' sawnwood prices. This suggests that imperfect competition models should be used in explaining and forecasting UK sawnwood imports. The results also raise an important issue concerning testing for competition in forest products markets, which is not usually done in connection with the modeling of markets. For. Sci. 44(1):17-23.

Tax Incidence and Optimal Forest Taxation under Stochastic Demand - Erkki Koskela; Markku Ollikainen (Forest Science, 1998)
This article examines the incidence and welfare effects of forest taxation in the competitive roundwood markets when future demand for timber is uncertain, thus making the future timber price stochastic. It turns out that the nature of timber price risk is crucial for the behavioral, incidence and welfare effects of forest taxes. Under private risk, when some do well and others poorly, the land site tax is like a pure profit tax and is fully borne by forest owners, while the burden of the yield tax is generally shared by both sides of the market. The incidence of the yield tax does not, however, matter qualitatively for the optimal structure of taxation. It is desirable to supplement the land site tax by a distortionary yield tax, because it provides social insurance by decreasing the after-tax timber price risk, which overweighs its distortionary effect. The level of the optimal yield tax is determined by the trade-off between its social insurance and distortionary effects. Under aggregate risk, when all either gain or lose, government budget constraint is stochastic. Given the optimal land site tax, optimal yield tax is nondistortionary and thus fully borne by forest owners. The neutrality of the optimal yield tax is due to the fact that it has no social insurance role in the presence of aggregate risk. The level of the yield tax depends on the risk attitudes toward variability of after-tax timber revenue and government consumption. For. Sci. 44(1):4-16.

Editor's Annual Report (Forest Science, 1998)

Meeting Announcements (Forest Science, 1998)

Upcoming Book Reviews (Forest Science, 1998)

Using Simultaneous Regression Techniques with Individual-Tree Growth Models - Hubert Hasenauer; Robert A. Monserud; Timothy G. Gregoire (Forest Science, 1998)
Individual-tree growth models basically consist of a number of equations (e.g., diameter or basal area increment model, height increment model, crown ratio model) to update tree parameters over time. These equations commonly are assumed to be independent, with parameters of each equation estimated separately rather than simultaneously with linear or nonlinear regression. However, the opposite assumption of interdependence seems more reasonable. A tree is a highly organized system, and assimilation of tissues in the form of diameter increment, height increment, and crown size does not occur independently. Procedures to simultaneously estimate systems of two or more interrelated models are well developed in the econometrics literature and are suggested as a viable alternative. Using more than 7,500 Norway spruce (Picea abies L. Karst) trees from the Austrian National Forest Inventory with remeasured breast height diameters and tree heights (5 yr interval), we compare an individual tree basal area increment model, a height increment model, and a crown ratio model separately using ordinary least squares (OLS) and simultaneously by applying two-and three-stage least squares (2SLS, 3SLS). Results indicate the presence of strong cross-equation correlations, especially between the basal area increment and height increment models. Thus, the 3SLS estimates are more efficient while the separately determined OLS estimates are biased. Two parameters that OLS indicates are significant are found to be nonsignificant when simultaneously estimating all system parameters with 3SLS. Such system simplification reduced the size of the variance-covariance matrix by 100 elements. For. Sci. 44(1):87-95.

1997 Contents (Forest Science, 1997)

1997 Author Index (Forest Science, 1997)

1997 Subject Index (Forest Science, 1997)

Meeting Announcements (Forest Science, 1997)

Brief Notice (Forest Science, 1997)

Upcoming Book Reviews (Forest Science, 1997)

Book Reviews: Tropical Deforestation: The Human Dimension - Hans M. Gregersen (Forest Science, 1997)

Notes: Effect of Desiccation, Temperature, and Moisture Content on Seed Storage of Three Tropical Tree Species - Eugenio Gonzalez J.; Richard F. Fisher (Forest Science, 1997)
We studied the viability of seeds of Hyeronima alchorneoides Fr. Allemao, Virola koschnyi Warb. and Vochysia guatemalensis D. Smith in relation to desiccation, seed moisture content, and storage temperature. Seed was either desiccated in chambers with activated silica gel or using air passed through columns of activated silica gel. Two seed moisture contents were achieved: 25-30% and 6-8%. Desiccated seeds were stored at either room temperature (25±1°C ) or in a cold room (4±1°C). Seeds of V. koschnyi and V. guatemalensis did not tolerate the loss of moisture and lost their viability completely. The seeds of H. alchorneoides tolerated desiccation treatments without significant loss of viability. A combination of low temperatures (4±1°C) and low seed moisture content (6-8%) allowed seeds to be stored for 6 mo. However, mean germination was reduced by storage. We also attempted to inhibit the germination of V. guatemalensis by treatment with five concentrations of abscisic acid: 10-4, 10-6, 10-10, 10-15, and 10-20 M. Abscisic acid failed to stop the germination of fresh seeds at any concentration tested. For. Sci. 43(4):595-601.

Notes: Optimal Economic Selection of Road Design Standards for Timber Harvesting Operations―A Corrected Analytical Model - Francis E. Greulich (Forest Science, 1997)
A theoretical development is given that corrects a long-accepted analytical model used in road system design. The model assumes that a forested area with uniform conditions of road construction is to be accessed by truck road for timber harvest. A discrete number of specified road design standards are available. Each design standard has known costs per unit length associated with road construction and use. The resulting total cost for any segment of the road when constructed to a given standard and used for timber haul depends fundamentally on the volume of timber transported over that segment. Transported volumes may vary along the length of the road, however, thus changing the associated costs. The emended economic decision rules for specifying road standards along the entire length of the road even as haul volumes change are developed. Examples are given. For. Sci. 43(4):589-594.

Genetic Control of Rooting Ability of Lodgepole Pine Cuttings - Anders Fries; Zeki Kaya (Forest Science, 1997)
This study evaluates the genetic control of rooting ability ex vitro for cuttings of lodgepole pine (Pinus contorta var. latifolia Engelm.). More than 200 clones from 21 full-sib families were studied during 4 yr in the greenhouse. Clonal averages in rooting frequency, root size score, shoot extension during rooting, and vitality score were calculated, together with variance components and phenotypic and genetic correlations among variables. Years, families within latitude of origin, clones within families within latitudes, and cutting type (type of shoot used as cutting) had statistically significant effects on rooting traits of cuttings. Years and clones within families had significant effects on height increment. Broad-sense heritabilities of clonal means were 0.55 for rooting frequency, 0.66 for root size, 0.56 for height increment, and 0.34 for vitality. To reduce the nongenetic variation when estimating genetic parameters, cuttings should not be taken from different shoot types. Genetic correlations among the variables were generally negligible. Cutting propagation of lodgepole pine seems possible for producing plants for genetic tests. After refinement of the methods it may also be used operationally, but clones that produce few shoots and have low rooting ability might be lost. For. Sci. 43(4):582-588.

Genetic Parameters and Selection Efficiencies in Resistance to Western Gall Rust, Stalactiform Blister Rust, Needle Cast, and Sequoia Pitch Moth in Lodgepole Pine - Harry X. Wu; Cheng C. Ying (Forest Science, 1997)
Genetic variances, heritabilities, and between-trait genetic correlations in resistance to western gall rust (Endocronartium harknessii), stalactiform blister rust (Cronartium coleosporioides), needle cast (Lophodermella concolor), and sequoia pitch moth (Synanthedon sequoiae) (Lepidoptera: Sesiidae) were investigated in a 21-yr-old lodgepole pine (Pinus contorta spp. latifolia) provenance-family trial with 778 wind-pollinated families in interior British Columbia. Selection efficiencies in expected improvement in resistance were compared among mass, family, sequential family-and-within-family, and combined family/individual index selection. Efficiencies in multitrait selection for overall resistance to the four pests based on different selection indices were also compared. Individual heritability for incidence of western gall rust was 0.50, stalactiform blister rust 0.32, needle cast 0.30, and sequoia pitch moth 0.21. Family mean heritabilities ranged from 0.39 to 0.65. The genetic correlation between incidence of sequoia pitch moth and stalactiform blister rust was 0.89, and between pitch moth and western gall rust 0.25. The genetic gain estimates from mass selection for resistance to the four pests varied from 14 to 31% at a 13% selection rate. On average, combined family/individual index selection was 5% more efficient than mass selection, and family and sequential family-and-within-family selection was about 38% and 16% less efficient than mass selection, respectively. Substantial improvement can also be expected from provenance selection. Multitrait index selection for overall resistance excluding sequoia pitch moth data was nearly as efficient as the full index. Indirect selection for resistance to sequoia pitch moth based on resistance for stalactiform blister rust was more efficient than direct selection. Selection for resistance showed little adverse effect on growth. For. Sci. 43(4):571-581.

A Longitudinal Analysis of Height/Diameter Curves - Juha Lappi (Forest Science, 1997)
The paper describes a simultaneous statistical analysis of height/diameter curves in data consisting of several temporal and permanent plots. Two jack pine data sets, one from planted stands and the other from naturally regenerated stands, were analyzed using the same model structure. Parameters of a logarithmic height/diameter curve at a given age in a given stand were decomposed into a trend (an age-dependent population mean), a random stand effect, and a random time effect. The deviation of an observed height from the stand and age specific height/diameter curve was decomposed into a random tree effect and a random residual error which have nonhomogeneous variances. Trend functions for the parameters of the height/diameter curve were estimated using least squares estimates of parameters as dependent variables (generalized least squares would lead to inconsistent estimates). The trend equations describe most of the variation in the height curve parameters. Other stand variables (in addition to age) can explain the variation further, but development over time cannot then be predicted. A less stable description of the height/diameter curves is obtained in terms of dominant height. In applications, height/diameter curves can be calibrated by predicting the random stand and time effects using any combination of height measurements. A simultaneously estimated set of curves will be logical also when there are so few measurements that ordinary least squares curves show erratic fluctuations. For. Sci. 43(4):555-570.

Managerial and Institutional Factors Affect Prescribed Burning Costs - Armando González-Cabán (Forest Science, 1997)
Prescribed burning costs are extremely variable, even if conditions are similar. This variability complicates planning and evaluation of prescribed burning programs and budgets, resulting in imprecise projections of their economic benefits. Evaluating the worth of prescribed burning efforts in objective terms is difficult, but the continual shrinkage of USDA Forest Service budgets requires an increase in program efficiency and understanding the causes of variability for prescribed burning costs. An analysis of variance model was used to describe and quantify the relative effect of managerial and institutional factors, such as smoke emission limitations or the constraint to control all types of fires, on prescribed burning costs. Data were collected by using a questionnaire to fire and fuel managers in the USDA Forest Service's Northern, Intermountain, and Pacific Northwest Regions. Estimated prescribed burning costs were significantly affected by changes in the managerial and institutional factors, such as minimizing escape potential or complying with smoke emission standards presented to these fire managers. Contrary to our expectations, burn objective (the main reason for conducting the burn) was not a significant cost factor. Unit size of the burned area affected prescribed burning costs more than either change in slope or unit shape, both of which increase the amount of burn perimeter relative to the area burned. Costs per acre demonstrated economies of scale: the larger the unit burned, the lower its per-acre cost. For. Sci. 43(4):535-543.

Growth and Physiological Responses of Young Loblolly Pine Stands to Thinning - J. A. Peterson; J. R. Seiler; J. Nowak; S. E. Ginn; R. E. Kreh (Forest Science, 1997)
Although yield responses to thinning in loblolly pine have been well documented, short- and long-term morphological and physiological changes are largely unknown. To investigate these responses, three 8-yr-old, 0.2024 ha replicate stands of loblolly pine were thinned by 50% in May 1988, and bole growth and morphological changes in the crown were measured annually for the next 6 yr. In situ gas exchange measurements were monitored in the upper and lower third of the crowns monthly during the third through sixth growing seasons following thinning. First- and second-year physiological responses to thinning have been reported earlier (Ginn et al. 1991). Thinning slowed live crown recession and increased crown diameters resulting in increased photosynthetic surface area per tree. Over the 6 yr study period, the crown diameters of thinned trees increased 82% while the crown diameters of control trees increased only 20%. Larger bole diameters were observed for thinned trees four growing seasons after thinning. Photosynthetic rate and needle conductance did not increase overall, but were increased in the lower crown foliage of thinned trees. Needle dark respiration was higher in thinned stands in both the upper and lower crowns. Increased bole diameter growth is likely the result of the large increases in foliar biomass as well as initially higher physiological activity in the lower crowns of thinned stands. For. Sci. 43(4):529-534.

Analyzing Uncertainties in Experts' Opinions of Forest Plan Performance - Juha M. Alho; Jyrki Kangas (Forest Science, 1997)
Multi-objective forestry requires new decision support systems to aid the forest owner and foresters in the planning of future treatment schedules. The analytic hierarchy process (AHP), based on pairwise comparison data and Saaty's eigenvector method, is one technique that has been proposed to make such qualitatively different objectives as income from timber sales and scenic beauty of forest landscape commensurable. A weak point of the methodology has been the lack of a statistical theory behind it. We have earlier shown how classical regression techniques can be used to provide a statistical assessment of the uncertainty of the estimated ratio-scales. In this paper we extend the results to a multi-level decision hierarchy commonly used in forest planning. We also provide a Bayesian extension of the regression technique. The advantage of the Bayesian approach is that it provides summaries of expert views that are easily understood by decision makers who may not have extensive understanding of statistical concepts. On the basis of the Bayesian analysis, one can calculate, for example, how likely it is that (in the view of the expert) a given forest plan is better than any other plan being compared. For. Sci. 43(4):521-528.

Uncertainty and Forest Land Use Allocation in British Columbia: Vague Priorities and Imprecise Coefficients - Arlene Ells; Erwin Bulte; G. Cornelis van Kooten (Forest Science, 1997)
Recently, increasing weight has been placed on nontimber values in forest management. Both the multiple objectives and the parameters that support decision making in forestry are often imprecise and vague. In this paper, the concepts of fuzzy set theory are explained and then applied to the problem of allocating public forestland on Vancouver Island among competing land uses. Two principal sources of fuzziness are identified--those related to uncertainty in classification (specification of management objectives) and those related to uncertainty concerning how actions affect objectives (imprecise technical coefficients). By comparing the results of classical and fuzzy decision models, we conclude that the latter approach can be judged an improvement over the former. The fuzzy land-use allocation appears to be more consistent with the political decision making process, which relies on consultation and consensus-seeking among various interest groups, that has evolved in British Columbia. The analysis also yields insights into the robustness of outcomes and suggests priority areas for further research. For. Sci. 43(4):509-520.

Relationship Between Volatile Foliar Terpenes and Resistance of Sitka Spruce to the White Pine Weevil - Elizabeth S. Tomlin; John H. Borden; Harold D. Pierce (Forest Science, 1997)
Volatile foliar terpenes were compared both quantitatively and qualitatively among 20 provenances and 11 cloned genotypes of Sitka spruce (Picea sitchensis Bong [Carr.]) that had been classified as resistant or susceptible to the white pine weevil (Pissodes strobi [Peck]). On average, trees in resistant provenances had significantly lower content of ten terpenes than in susceptible provenances. One resistant clone had significantly higher foliar terpene content, and four resistant clones had significantly lower content than susceptible trees. Thus clonal resistance could be expressed respectively by repellency or lack of apparency. Canonical discriminant analysis revealed that several resistant clones, particularly from the Haney provenance, could be distinguished from others on the basis of their terpene profiles. While there was no clear relationship between terpene profile and resistance, these results suggest that there are probably multiple resistant "chemotypes," and that volatile foliar terpenes may be useful in identifying potentially resistant trees. For. Sci. 43(4):501-508.

A Distribution-Independent Approach to Predicting Stand Diameter Distribution - Shouzheng Tang; Yonghe Wang; Lianjun Zhang; Cho-Ho Meng (Forest Science, 1997)
A new approach to projecting future stand diameter distribution was proposed without assuming a predefined probability density function. The Lebesque-Stieltjes integral was applied to derive a group of equations for the relationships between current and future stand diameter distributions and stand-level attributes. The parameters in the tree survival function and diameter growth function were recovered using these equations based on independent estimates of future stand mean diameter, quadratic mean diameter, and survival from a whole stand model. This disaggregation approach ensured that the resolutions at size-class distribution and/or individual tree levels were compatible with the stand-level aggregates. A stochastic error component was incorporated into the tree diameter growth function. This allowed us to mimic the tree diameter differentiation process over time, and it improved prediction accuracy for future stand diameter distributions. The proposed approach can also be used to allocate stand growth and yield to a list of individual trees. The fluctuation of tree growth and survival for each tree can be implemented by simulating the variance of tree diameter growth and survival probability using Monte Carlo or error propagation methods. For. Sci. 43(4):491-500.

Correlation of Counts of Gypsy Moths (Lepidoptera: Lymantriidae)in Pheromone Traps with Landscape Characteristics - Alexei A. Sharov; Andrew M. Liebhold; E. Anderson Roberts (Forest Science, 1997)
The effect of landscape characteristics (elevation, slope, aspect, and vegetation) on counts of gypsy moths in pheromone traps was studied in a >5 million ha area in Virginia and West Virginia from 1988 to 1994. Habitat effects on population numbers depend on dominant ecological processes in the area: we define K-, r-, and c-effects as differences in carrying capacity, population growth rate, and colonization rate, respectively, that are associated with different landscape characteristics. To differentiate among these effects, we analyzed individually the following three zones at the expanding front of the gypsy moth population: infested (K-effects), transition (r-effects), and uninfested (c-effects). Among landscape characteristics, elevation was most highly correlated with moth counts. Moth counts increased with increasing elevation in the infested and transition zones (K- and r- effects) which may be associated with good habitats at high elevation. However, the highest average moth counts in the uninfested zone were found at low elevation. Possibly this was a c-effect which resulted from a greater colonization rate in the low-elevation areas where human population densities are greater and the probability of inadvertent transfer of egg masses on human vehicles is increased. The effect of vegetation on moth counts was much less pronounced than the effect of elevation. Moth catches were higher in deciduous and mixed forests than in coniferous forests and nonforested areas. The effect of landscape characteristics on moth captures was stronger in the transition zone than in other zones. For. Sci. 43(4):483-490.

Comparing the Economic Value of Reducing Fire Risk to Spotted Owl Habitat in California and Oregon - John B. Loomis; Armando González-Cabán (Forest Science, 1997)
To increase the range of natural resource values considered in the USDA Forest Service fire management analysis system, a combined telephone contact-mail booklet-telephone interview of California and New England households regarding their willingness to pay for reducing fire intensity and acres burned in California and Oregon's spotted owl habitat located in old growth forests was performed. Using a multiple bounded dichotomous choice format, annual willingness to pay of $79 per California household and $46 per New England household was estimated for a 20% reduction in acreage burned in California. For the same percentage reduction in fire in Oregon's old growth forest the value is $59 per California household and $45 per New England household. For a combined California and Oregon Program, California households would pay $95 annually, while New England households would pay $61. This illustrates the importance of national programmatic valuation of the USDA Forest Service's fire control program in old growth forests, rather than state by state surveys which miss substitution effects. This analysis also demonstrates that households benefit from and support fire protection of old growth forests in states other than their own. For. Sci. 43(4):473-482.

Breeding Objective for Plantation Eucalypts Grown for Production of Kraft Pulp - Bruce L. Greaves; Nuno M. G. Borralho; Carolyn A. Raymond (Forest Science, 1997)
A long-term production function for unbleached eucalypt kraft pulp, incorporating all growing, harvesting, transport, and pulping costs, and variable capital and operating costs, was used to determine the economic importance of standing volume, basic density, pulp yield, and stem form. The value of each trait to breeding was defined as the relative improvement toward the objective (of minimizing total pulp cost) for a given selection intensity when selecting for each trait individually. For genetic parameters typical of eucalypts, and with the aid of simulated first-geneneration eucalypt populations, density and standing volume were the most important traits, providing the greatest savings in total pulp cost. Combined selection using density and volume provided 95% of the gains possible from an index involving all traits (density, volume, pulp yield, and form). Selection for pulp yield alone provided only 53% of the savings possible from selection for density, and improvement in stem form had negligible effect on total pulp cost. For. Sci. 43(4):465-472.

Back Matter Volume 43 Issue 4 1997 (Forest Science, 1997)

Front Matter Volume 43 Issue 4 1997 (Forest Science, 1997)

Forest Harvesting and Minimum Cuts: A New Approach to Handling Spatial Constraints - Dorit S. Hochbaum; Anu Pathria (Forest Science, 1997)
In this paper we discuss two forest harvesting optimization problems that arise in forest management. We consider one-stage decision problems in which the forest to be managed is partitioned into cells and the decision is to be made as to which cells to harvest. There are competing concerns to consider in assessing the value of a particular harvesting decision: the first has to do with the value of the timber harvested, and the second has to do with assessing the relative values of the resulting spatial layout from a wildlife habitat point of view. The two problems that we consider are similar, but they assess the relative merits of resulting spatial layouts somewhat differently and therefore have different objective functions to be optimized. The first problem we consider assigns benefits for harvesting cells and penalties for harvesting adjacent cells; the second problem considered assigns benefits for harvesting cells as well as benefits for creating borders that separate harvested and unharvested cells. We show that both forest harvesting problems can be interpreted as instances of the Generalized Independent Set graph optimization problem, which we introduce in this article. Generalized Independent Set is a generalization of the well-known Independent Set graph optimization problem (a set of nodes in a graph is said to be independent if no two nodes in the set are adjacent). When the underlying graph is bipartite, we derive an efficient solution method for Generalized Independent Set via network flow methods. If the cell structure is grid-like in the forest harvesting problems, then an instance of either forestry problem can be reduced to an instance of Generalized Independent Set on a bipartite graph. For such instances we developed efficient algorithms for determining an optimal harvesting strategy. The running time is O(n² log n), where n is the number of cells in the land area to be spatially managed. For. Sci. 43(4):544-554.

Book Reviews: Seeds of Forest Broadleaves from Harvesting to Sowing - Kristina F. Connor (Forest Science, 1997)

Meeting Announcements (Forest Science, 1997)

Upcoming Book Reviews (Forest Science, 1997)

Brief Notice (Forest Science, 1997)

Endophytic Fungi in Grasses and Woody Plants. Systematics, Ecology and Evolution - Jeffrey Stone (Forest Science, 1997)

Biology of Populus and its Implications for Management and Conservation - Richard B. Hall; Hans Heybroek (Forest Science, 1997)

Tropical Rainforest Research—Current Issues - John J. Ewel (Forest Science, 1997)

The Practice of Silviculture—Applied Forest Ecology, Ninth Edition - Todd W. Bowersox (Forest Science, 1997)

Resource Management Information Systems: Process and Practice - Russell G. Congalton (Forest Science, 1997)

Relating Site-Specific Weather Data to Regional Monitoring Networks in the Lake States - E. Kuuseoks; H. O. Liechty; D. D. Reed; J. Dong (Forest Science, 1997)
Meteorological variables most frequently used in ecological studies include, or are derived from, daily precipitation and air temperature. In many studies, weather data from the nearest permanent weather station are used as surrogates for on-site measurements. This study discusses the problems with this approach and illustrates methods for developing regression equations for calculating site-specific daily minimum, average, and maximum temperatures, and precipitation amount from regional monitoring information. Meteorological data were collected at four sites along a 650 km climatic gradient from Houghton County (47°N, 89°W) to Oceana County (43°N, 86°W), Michigan. Data from several National Oceanic and Atmospheric Administration (NOAA) stations within 40 km of each study site were related to measurements made at each site. Predictive ability was improved by using information from more than one NOAA station to predict on-site temperature. No increase in predictive ability resulted from including information from more than a single station when predicting precipitation. For the majority of the sites and climate variables, the best relationships were not obtained by using the nearest NOAA station; variables such as the relative distance from large bodies of water or elevation appeared to be influential. Since distance between two locations is rarely the most important factor governing the relationship between their climates, the use of the nearest weather station is not the best method to describe weather conditions on specific sites of interest. For. Sci. 43(3):447-452.

A Compatible Growth-Density Stand Model Derived from a Distance-Dependent Individual Tree Model - Guofan Shao; Herman H. Shugart (Forest Science, 1997)
A compatible growth-density stand model is developed for simulating forest stands with uniformly distributed trees (e.g., square spacing, equilateral triangle spacing, and 1:1.5 row to column ratio tree distribution patterns). The model is based on a distance-dependent individual-tree competition model. The independent variable in the individual-tree model is Hegyi's (1974) diameter-distance competition index with n = 8. The derived growth density stand model satisfies a necessary boundary condition (i.e., stand growth is zero either when stand density is zero or when stand density reaches to a very high level). The stand density which maximizes stand growth rate can be calculated with this stand model. It is found that stands with an equilateral triangle tree distribution pattern have the greatest growth rate among the three uniform stands. Stand growth in measured forests is more than 10% lower than that predicted in uniform stands. Simulation comparisons suggest that the uneven distribution of trees in such stands can reduce stand growth. For. Sci. 43(3):443-446.

A Method to Distribute Mortality in Diameter Distribution Models - Quang V. Cao (Forest Science, 1997)
Bailey (1980) derived tree diameter growth models by transforming variables which preserved the functional form of the probability density function that approximated diameter distributions. The necessary assumption was either no mortality, or that mortality was proportionally distributed among diameter classes. The latter assumption might not be realistic since smaller trees should suffer more from competition than large trees and are more likely to die. This paper deals with the case when mortality is not proportionally distributed. If diameters in a stand originally follow a Weibull distribution and mortality for a growing period can be assumed to occur at the beginning of that period, then a Weibull was found to successfully approximate the diameter distribution immediately after mortality. The stand then grows without further mortality and reaches the end of the period with its diameters remaining Weibull. A similar method to derive a diameter distribution after mortality was developed for the beta distribution. The Weibull technique was applied to data from loblolly plantations. Results showed that the new approach worked reasonably well and was comparable with a diameter distribution model in approximating diameter distribution of a stand at the end of the growth period. For. Sci. 43(3):435-442.

Constraining Individual Tree Diameter Increment and Survival Models for Loblolly Pine Plantations - Shaoang Zhang; Ralph L. Amateis; Harold E. Burkhart (Forest Science, 1997)
Among extant forest growth and yield models, individual tree growth models provide the most detailed information, which is useful for intensive forest management. However, individual tree growth models may be inaccurate for stand-level predictions because of the cumulative error resulting from individual tree predictions. This paper is aimed at developing a method to ensure that individual tree growth models not only provide precise individual tree predictions but also give precise stand-level estimation. Based on the conceptual relationships between basal area of each diameter class and the diameter increment of trees in the same diameter class, a constrained regression equation system is proposed. The same approach is also applied to modeling individual tree survival probability. An algorithm for estimating multiresponse regressions was developed. Results using data from unthinned loblolly pine (Pinus taeda L.) plantations show that the simultaneous equation system provides nearly the same individual tree diameter increment estimates as the unconstrained model but better estimates for basal area of each diameter class and for total stand basal area. The potential for improving stand mortality estimation with a constrained individual tree survival model where there is little mortality in the data is limited. For. Sci. 43(3):414-423.

Choosing Prices to Optimally Buck Hardwood Logs with Multiple Log-Length Demand Restrictions - James B. Pickens; Scott A. Throop; James O. Frendewey (Forest Science, 1997)
The purpose of this article is to present a hierarchical optimization approach that selects prices which, when used in a single stem bucking optimization model, produce a specified mix of logs by grade and length. The model is developed to address the demand constrained optimal bucking situation for northern hardwoods. The demand constraints are minimum percentages needed in four log lengths [3.0 m (10 ft), 3.7 m (12 ft), 4.3 m (14 ft), and 4.9 m (16 ft)] to meet order requirements from veneer buyers. There are two levels in the hierarchical optimization system: at the lower level, a dynamic programming model is used to optimize the value of each individual tree, while the upper level is a linear programming model which finds one or more sets of prices, each used some portion of the time, that produce the required product mix in the lower level model. The hierarchical model is solved iteratively until a single set of prices satisfies all demand constraints. This approach is distinctly different than traditional approaches, which pass different information between the upper and lower level models to solve two-level optimization problems. The parameters passed in traditional approaches are shadow prices in one direction and production levels in the reverse direction. The model developed could be adapted to other species and log grading rules whenever several competing demand constraints exist. Furthermore, the approach could be adapted to a wide range of hierarchical planning applications where inputs, and therefore the production possibilities curve, are fixed and constraints apply. For. Sci. 43(3):403-413.

Clonal Variation in Susceptibility of White Birches ( Betula Spp.) to Mammalian and Insect Herbivores - Matti Rousi; Jorma Tahvanainen; Heikki Henttonen; Daniel A. Herms; Ilari Uotila (Forest Science, 1997)
Resistance of small micropropagated plantlets and seedlings of white birch (Betula pendula Roth and B. pubescens Ehrh.) to hares (Lepus timidus L.), voles (Microtus agrestis L.) and weevils (Phyllobius and Polydrosus spp.) was determined. Field and cafeteria experiments were conducted over 2 yr period at several locations near Punkaharju Forest Research Station, Eastern Finland. There were significant differences among clones and seedlots (forest seed origins) in susceptibility to hares, voles, and weevils. One of the eight clones studied in detail was resistant to most tested agents (clone 39), whereas two clones were susceptible to each agent (clones 36 and JR/1). However, there was only one significant correlation (hare vs. Polydrosusweevil) among rankings of clones in susceptibility to different pests. Generally the differences among clones were similar in different experimental situations, indicating a genetic basis to variation in resistance. No difference in the susceptibility was observed between seedlots from natural forest and micropropagated plantlets from rapidly growing plus trees, suggesting that selecting for rapid growth did not compromise resistance as predicted by some theories. For. Sci. 43(3):396-402.

The Effects of Neighborhood Storage Size on Dynamic Programming Solutions - Matthew H. Pelkki (Forest Science, 1997)
Forward recursive dynamic programming (DP) was used to investigate the sensitivity of two- and three-state dynamic programming networks to neighborhood storage. Two-state DP networks were formed using all pairwise combinations of four state variables (basal area, cubic foot volume, number of trees, and diameter) and various neighborhood intervals for each state variable. As state neighborhoods decreased in size, all solutions were converged on a single rotation scheme and objective function value. Large state neighborhoods with nonuniform future growth and value potentials result in suboptimal solutions and incorrect sensitivity analyses. Comparison of various two-state networks indicate that models incorporating net cubic volume are less sensitive to increases in state neighborhood size. The addition of both a forward "look ahead" heuristic and the "harvest type" state variable to two-state networks improved the objective function value when neighborhoods were large and had nonuniform intra-neighborhood future growth and value potentials. However, these additional efforts resulted in no improvement in the objective function value when small state neighborhoods were used, further supporting the hypothesis that the DP algorithm did find the global optimum solution for the given problem formulation. For. Sci. 43(3):387-395.