Exploring the Error Structure of Taper Equations - Michael S. Williams; Robin M. Reich (Forest Science, 1997)
Much work has been done fitting taper equations to specific tree bole shapes, but few researchers have investigated what effect the correlated error structure has on the fit of a taper equation. The Max and Burkhart (1976) taper equation was used in conjunction with a number of equations which modeled the covariance structures. The equations proposed were continuously differentiable, which simplifies the fitting process, and selected to minimize the number of parameters. A maximum likelihood method was proposed to fit these equations and test the statistical significance of the correlated errors. Accounting for the correlated errors structure in the equation fitting process significantly improved fit. Tests showed a small, but significant, bias of 1.05% (± 0.143%) when the correlated errors were ignored. For. Sci. 43(3):378-386.

Communication Media and Demand for Printing and Publishing Papers in the United States - Yibing Zhang; Joseph Buongiorno (Forest Science, 1997)
To predict the demand for printing and publishing papers, a model was first developed of the demand for printed materials—newspapers, books, magazines, and their substitutes--computers, and televisions and radios. A two-stage Almost Ideal Demand System (AIDS) represented the consumer demand for communication media (stage one) and for printed materials, computers, and televisions and radios (stage two). Annual United States data from 1960 to 1991 were used to estimate the expenditure share equations and related elasticities. The results suggest that during that period: (1) printed materials and computers were luxury goods; (2) the demand for printed materials was independent of the price of computers and slightly complementary of the demand for televisions and radios; and (3) the demand for printed materials was most sensitive to its price and to income. Then, the demand for paper by the printing and publishing industry was derived from a two-stage translog cost minimization model. The first stage describes the demand for paper to make printed materials together with labor, capital, and other materials. The second stage decomposes the demand for paper into that for each printing and publishing grade. Results show that during the period of observation, (1) paper demand was inelastic; (2) labor, capital, and other materials were substitutes for paper in making printed materials; and (3) technical change led to a relative decrease in the use of newsprint, and an increase in that of other paper grades. Equating production of printed materials to consumer demand led to the derived demand for each paper grade. The elasticities suggested that paper demand was not influenced much by the price of electronic media. A decomposition analysis of the growth in demand for printing and publishing papers showed that from 1981 to 1991 the positive income effects were most important, followed by the negative effects of changes in the prices of printed materials. For. Sci. 43(3):362-377.

Growth and Water Use of Red Spruce ( Picea Rubens Sarg.) Exposed to Ozone and Simulated Acidic Precipitation for Four Growing Seasons - J. A. Laurence; R. G. Amundson; R. J. Kohut; D. A. Weinstein (Forest Science, 1997)
Red spruce (Picea rubens Sarg.) saplings from a pristine site in Maine were transplanted in native soil to 360 liter pots and relocated to Ithaca, New York. After a 1 yr establishment period, 90 saplings were chosen for use, assigned to treatments, placed in large open-top chambers, and exposed to ozone (0.5 to 2.0 x ambient concentration) and simulated acidic precipitation (at pH 3.1, 4.1, or 5.1) for 3 or 4 consecutive growing seasons (total ozone exposures of about 165 ppm · hr to almost 570 ppm · hr). Forty-five trees were grown on weighing lysimeters and were used to develop whole-tree water-use budgets. After 3 yr of exposure, the 45 trees not grown on lysimeters were harvested, and the plant tissues were weighed. After the fourth growing season, the remaining 45 trees were harvested, and the weight of the plant tissues was determined. Significant effects of ozone or simulated acidic precipitation were not detected, with the exception of a trend for increased needle dry weight with increasing ozone and, in 1990 needles only, with decreasing pH. No effects were detected in total dry weight, aboveground dry weight, coarse or fine root weight, stem dry weight, or relative growth rate. No significant interactions of ozone and pH treatment were detected. Neither ozone nor pH treatment affected the rate of water use by red spruce saplings, even when they were subjected to a dry-down period resulting in drought stress. For. Sci. 43(3):355-361.

A New Height Growth Model for Dominant and Codominant Trees - Fan-Rui Meng; Chao Ho Meng; Shouzheng Tang; Paul A. Arp (Forest Science, 1997)
A model was developed to predict height growth for dominant and codominant trees, using asymptotic tree height, and tree height at the age of maximum height growth as principal characteristics to express the influence of site on tree height. The proposed model has many desirable attributes: it (1) produces polymorphic site-index curves, (2) contains an inflection point, (3) asymptotically approaches maximum tree height as age increases, (4) is mathematically defined at the point of origin, and (5) has a theoretical base (pipe model theory) for height growth. Model performance was evaluated with stem analysis data taken from naturally regenerated forest stands of mature to overmature balsam fir (Abies balsamea [L.] Mill.) and black spruce (Picea mariana Mill.) growing in two separate regions within New Brunswick, Canada. The model was also evaluated by analyzing its ability to reproduce existing site index curves for red pine (Pinus resinosa Ait.). The results indicate that the proposed model performs slightly better than an existing 5-parameter model based on the Richards' growth function. For. Sci. 43(3):348-354.

Comparative Plant Water Relations and Soil Water Depletion Patterns of Three Seral Shrub Species on Forest Sites in Southwestern Oregon - Susan G. Conard; Steven R. Sparks; Jon C. Regelbrugge (Forest Science, 1997)
We compared stomatal conductance, transpiration, plant water potential, and soil moisture depletion patterns for three shrub species common on early seral forest sites in southwestern Oregon following logging or fire. Our goal was to determine which of these species were more likely to be the strongest competitors with regenerating conifers. The three species, Arctostaphylos patula Greene, Ceanothus sanguineus Pursh., and Holodiscus discolor (Pursh.) Maxim., were selected to represent a range in leaf morphology and expected water use patterns. Diurnal patterns of leaf conductance, plant water potential, and environmental parameters were measured throughout the growing season, along with seasonal patterns in soil moisture. As with any data obtained under ambient field conditions, environmental parameters and exact timing of measurements varied among shrubs. To better evaluate the response of individual species to common environmental parameters, we constructed models of leaf conductance based on field data and used these models to estimate responses of conductance and transpiration to averaged environmental conditions. This allowed us to better compare species responses to seasonal and diurnal trends in environmental variables. C. sanguineus typically had the highest transpiration rates per unit leaf area, and H. discolor the lowest; however, due to much higher leaf area indices of H. discolor, the two species depleted soil moisture at about the same rate. C. sanguineus and A. patula both had high predawn water potentials throughout the season, even when soil water potential at 1 m depth was less than -1.2 Mpa, suggesting that these species, but not H. discolor, had roots in deeper soil layers. We predict that the two deciduous species, C. sanguineus and H. discolor, will be stronger competitors for soil moisture than A. patula, at least in the top meter of soil. In contrast, A. patula and C. sanguineus are capable of depleting moisture from deeper in the soil and may therefore strongly compete even with deep-rooted conifers late in the season. Our use of empirical models allowed us to compare species responses to common environmental conditions, which facilitated ecological interpretation of species differences in water use patterns. By early August, soil water potentials under all species were low enough to significantly inhibit conifer transpiration, photosynthesis, and growth. For. Sci. 43(3):336-347.

Monitoring Hemlock Forest Health in New Jersey Using Landsat TM Data and Change Detection Techniques - Denise D. Royle; Richard G. Lathrop (Forest Science, 1997)
Defoliation of eastern hemlock (Tsuga canadensis Carriere) forest caused mainly by the hemlock woolly adelgid (Adelges tsugae Annand) was detected, quantified, and mapped for a 1,267 km² study area in the New Jersey Highlands using anniversary dates of Landsat Thematic Mapper data (1984 and 1994). A model relating estimates of canopy condition to the temporal difference in near infrared/red reflectance (i.e., the vegetative index difference) was developed to predict and map four classes of hemlock condition across the study area. Data from 105 circular ground plots (90 m diameter) were used to develop the regression model, while data from 50 plots were reserved for accuracy assessment. The vegetative index difference was highly correlated to hemlock damage as measured on the ground (R² = 0.73). Lightly defoliated hemlock canopy did not differ spectrally from healthy hemlock; thus, these two classes were joined together. Accuracy assessment showed that hemlock condition can be predicted within one-half damage class with an overall accuracy of 64% for four damage classes, 70-72% for three classes, and 78-92% for two classes. Of the 7,735 ha of hemlock forest in 1984, 47% remained healthy to lightly defoliated, 44% had experienced moderate to severe defoliation, and 9% were dead by 1994. For. Sci. 43(3):327-335.

Applying Objectively Estimated and Spatially Continuous Forest Parameters in Tactical Planning to Obtain Dynamic, Treatment Units - Peter Holmgren; Thomas Thuresson (Forest Science, 1997)
Forestry planning is usually approached as the problem of combining and scheduling stand treatments. Stands are assumed to be homogeneous and spatially static and are usually delineated and described by subjective surveying methods. Because, in reality, stands vary internally, only subsets of the possible management alternatives will be considered in stand-based planning. As price expectations and other planning parameters change over time, it is likely that optimal locations, extensions, and schedules for forest operations change. This paper proposes a method whereby timber volumes and treatment priorities are estimated on objectively inventoried geo-referenced circular plots. Kriging interpolation and image analysis of scanned aerial photographs are then used to predict the variables in a spatially near-continuous raster. Treatment units are dynamically formed, based on price-expectations, and objectives defined by the forest owner. Given strategic goals, tactical plans are produced for two wood price situations, and compared with a plan based on conventional stands. The results imply that forest management planning should, perhaps, not be based on static stands if economic efficiency and planning flexibility are desirable. For. Sci. 43(3):317-326.

Back Matter Volume 43 Issue 3 1997 (Forest Science, 1997)

Front Matter Volume 43 Issue 3 1997 (Forest Science, 1997)

Environmental Values in American Culture - Linda E. Kruger (Forest Science, 1997)

Biomass Estimation for Temperate Broadleaf Forests of the United States Using Inventory Data - Paul Schroeder; Sandra Brown; Jiangming Mo; Richard Birdsey; Chris Cieszewski (Forest Science, 1997)
A potentially valuable data source for estimating forest biomass is forest volume inventory data that are widely collected and available throughout the world. In this paper we present a general methodology for using such data to reliably estimate aboveground biomass density (AGBD) and to develop expansion factors for converting volume directly to AGBD from USDA Forest Service Forest Inventory and Analysis (FIA) data. Growing stock volume inventory data and stand tables were combined with independently developed biomass regression equations to estimate AGBD and to calculate biomass expansion factors (BEF: factors that convert volume to mass, accounting for noncommercial components) for the extensive oak-hickory and maple-beech-birch forest types of the eastern United States. Estimated aboveground biomass for both forest types ranged between 28 and 200 Mg ha-1. Expansion factors decreased from more than 4.0 at low growing stock volume to nearly 1.0 when growing stock volume was as high as 190 m³ ha-1, consistent with theoretical expectations. In stands with low AGBD (< 50 Mg ha-1), small diameter trees (< 10 cm diameter) contained up to 75% of the AGBD in trees ≥ 10 cm diameter; this proportion dropped to < 10% for stands with AGBD > 175 Mg ha-1. The similarity of our results for two major forest types suggests that they may be generally applicable for estimating AGBD from inventory data for other temperate broadleaf forests. Further, the pattern between BEF and stand volume was similar to that obtained for tropical broadleaf forests, except that tropical forests generally had larger BEFs than temperate forests at a given volume. The implications of these results suggest that a recent assessment of forest biomass in developed countries is too low. For. Sci.: 43(32):424-434.

Meeting Announcements (Forest Science, 1997)

Upcoming Book Reviews (Forest Science, 1997)

Brief Notices (Forest Science, 1997)

Small Format Aerial Photography - Stephen E. Reutebuch (Forest Science, 1997)

Environmental Accounting—EMERGY and Environmental Decision Making - Per Olov Nilsson (Forest Science, 1997)

Environmental Constraints on the Structure and Productivity of Pine Forest Ecosystems: A Comparative Analysis - William R. Harms (Forest Science, 1997)

Estimating Foliage Area of Loblolly Pine Shoots - Ramesh Murthy; Phillip M. Dougherty (Forest Science, 1997)
In this study, foliage surface area of loblolly pine (Pinus taeda L.) shoots from plants grown in a 2 x 2 factorial study of nutrients and water and three levels of CO2 was predicted by flush (growth cycle). Harms (1971) predicted foliage surface area of a flush from the weighted product of foliated flush length and average needle length. In the present study flush foliage surface area was predicted using the product of the natural log of foliated flush length and average fascicle length, and an additional independent variable fascicle density. Equations generated for each of the whole-plot treatment combinations did not differ significantly, therefore one prediction equation was developed for all whole-plot treatment combinations. Flush location significantly affected prediction of flush foliage area, therefore separate equations for predicting flush surface area were developed for the main and lateral shoots. The equations explained 96% of the variation in predicting flush foliage surface area for both main and lateral shoots with fascicle density explaining an extra 12% of the variation. The equations predicted flush foliage surface area with an average absolute percent deviation of predicted values of 16.1% and 12.6% for the main and lateral shoots. For. Sci. 43 (2):299-303.

Vector Diagnosis of Nutrient Dynamics in Mesquite Seedlings - Moses Imo; Victor R. Timmer (Forest Science, 1997)
This paper reports an application of vector analysis to interpret temporal interrelationships between plant biomass and nutrient status with time, as demonstrated using young mesquite (Prosopis chilensis) seedlings. Conventional (single dose or constant top dressing), and exponential (pure or modified exponential) fertilization schedules were used to induce contrasting plant nutrient status in the seedlings over a 12 wk growing season. Progressions in nutrient status showed that conventional fertilization resulted in nutrient dilution whereas pure exponential fertilization achieved steady-state nutrient conditions after an initial deficiency. The modified exponential schedule attained steady-state nutrition for most of the experimental period. These trends were similar for all the three elements (N, P, and K). This study demonstrated that dynamic time dependent responses such as steady-state nutrient conditions, nutrient dilution, and accumulation can be identified using traditional vector analysis provided a fourth variable, time (t), is introduced. This approach also allows simultaneous comparisons of multiple elements on the same nomogram, facilitating assessment of differential nutrient absorption during seedling development. For. Sci. 43(2):268-273.

Effects of Constitutive and Inducible Traits of Hybrid Poplars on Forest Tent Caterpillar Feeding and Population Ecology - Daniel J. Robison; Kenneth F. Raffa (Forest Science, 1997)
Hybrid Populus spp. clones, differentially affected forest tent caterpillar, Malacosoma disstria, behavior, development, and population dynamics. Increased larval cohort size and larval silk generally enhanced development. Larval behavior affected developmental success. Under choice conditions, larvae selected more suitable clones, and their growth was enhanced when they moved from less to more suitable hosts. Herbivory by the forest tent caterpillar caused significant reductions in the quality of foliage for subsequent larval development. Polar and nonpolar foliar extracts varied between constitutive and previously damaged plants, and elicited significant larval behavioral responses. The extent to which prior feeding induced foliar changes that affected larval feeding and development varied among clones. The ability of forest tent caterpillar to exploit clones includes genetic and environmental components affecting foliar quality, and includes positive and negative density dependent feedback. In whole-tree field cages, forest tent caterpillar populations increased 9.7x during a 2 yr period on a highly suitable clone, and declined 2.7x on a poor quality clone. The relationships between clonal suitability and forest tent caterpillar population growth were strongly influenced by bud phenology and exudates, in addition to foliar traits. For. Sci. 43(2):252-267.

Implications of Disaggregation in Forest Growth and Yield Modeling - Martin W. Ritchie; David W. Hann (Forest Science, 1997)
Growth and yield simulators may be characterized with regard to the aggregation structure employed. Individual-tree simulators are an example of a passive aggregation approach. Whole-stand models represent an active aggregation structure. Of particular interest is the disaggregative modeling approach, which employs elements of both individual-tree and whole-stand simulators. The apparent resolution of the disaggregative model is at the tree-level; however, the functional resolution is at the stand level. Disaggregation may be achieved with either additive or proportional allocation of growth. Additive allocation may not ensure positive individual-tree projections of growth. Either may be constrained so as to maintain symmetry between the whole-stand projection of growth and the aggregate of predicted tree growth. Traditionally, the disaggregative approach has seen the application of very simple structures for allocation of growth depending on tree dimension alone. However, the concept may be generalized to include traditional individual-tree growth equations constrained so as to act as an allocation of predicted stand growth. For. Sci. 43(2): 223-233.

Dynamic Selection of Harvests with Adjacency Restrictions: The SHARe Model - Stephanie Snyder; Charles ReVelle (Forest Science, 1997)
A dynamic forest management model is developed that incorporates spatial and temporal harvesting adjacency restrictions. The spatial harvesting requirements are modeled through the use of 0-1 integer programming models. A variety of different specifications of harvest adjacency constraints is developed and their relative impact on computational efficiency examined. Many researchers have turned to heuristic methods to approach such spatially constrained integer programming problems in the past, especially problems which include harvest flow restrictions. However, the spatially constrained integer programming model developed here, SHARe (Selecting Harvests with Adjacency Restrictions), can be solved optimally. We solve problems up to 441 units on a square grid (21 x 21) using exact optimization methods. Multiple solutions are provided for hypothetical data. In most cases, depending on the structure of the adjacency constraints, the model solved without any or only a few branch and bound nodes. This result is due, in large part, to the model being based on the classic shortest path network flow model, which is known to have special integer solution properties. In addition, we also determined that certain adjacency constraint structures are more favorable to achieving all-integer solutions than others, when used in conjunction with the network flow model developed here. For. Sci. 43(2):213-222.

How to Calculate Optimum Family Number When Starting a Breeding Program - Dag Lindgren; Run-Peng Wei; Steve J. Lee (Forest Science, 1997)
Methods were developed to calculate the optimum number of initial unrelated families (equivalent to founders) in a breeding program, which, following selection in a predetermined way, would result in the maximum gain. The required entries were: (1) effective population size (effective family number) after selection, (2) family type (half-sib or full-sib), (3) heritability, (4) number of selections, (5) available resources, and (6) cost per additional family in the initial population. Suggestions of optimum family numbers and other characteristics of the optimum were calculated for particular examples. It seemed important to consider cost components when planning breeding programs. The optimum initial family number was far greater than the intended effective family number when the marginal cost of adding initial families was low. If this cost was high, it was worth investing more than half of any fixed resources in obtaining many families. The value of heritability appeared rather unimportant. For. Sci. 43(2):206-212.

Radial Growth Response of Douglas-fir and Grand Fir to Larval Densities of the Douglas-fir Tussock Moth and the Western Spruce Budworm - Richard R. Mason; Boyd E. Wickman; H. Gene Paul (Forest Science, 1997)
Statistical models were developed relating corrected tree-ring chronologies of grand fir (Abies grandis [Dougl. ex D. Don] Lindl.) and Douglas-fir (Pseudotsugata menziesii var. glauca [Beissn.] Franco) to population time series of Douglas-fir tussock moth (Orgyia pseudotsugata [McDunnough]) and western spruce budworm larvae (Choristoneura occidentalis Freeman) in the same stands. The study was conducted in northeastern Oregon and spanned 22 yr including 2 periods of defoliator outbreaks as well as an interval of no outbreaks. Changes in the radial increment of host trees, corrected for tree-ring age and weather, were inversely related to larval densities in the same year of growth and in each of the 4 preceding years. The strongest growth response was a delayed function of larval density with a 3 yr time delay. Regression models giving the best fit to pooled data were second-degree polynomials in which log larval density with a 3 yr delay accounted for 28.7% of the variation in rate of change in corrected tree-ring indices, and 46.4% of the variation in the absolute size of corrected indices. The results imply that reductions in radial growth are directly related to density of feeding larvae and that the cumulative maximum effect on increment in the lower bole lags defoliation by 3 yr. The models are recommended either for directly forecasting mean reductions in radial increment from monitored densities of larvae or for inversely predicting past mean densities of defoliating larvae from dendrochronology data. For. Sci. 43(2):194-205.

New Zealand's Privatization of Forest Lands: Policy Lessons for the United States and Elsewhere? - O. F. Hall (Forest Science, 1997)
Two forest policy questions are examined: 1. What particular problems in New Zealand's privatization of public forest lands (1985 to 1995) need thorough examination prior to proposing it in the United States or elsewhere? 2. What light does the New Zealand experience throw on the question of whether privatization and subdivision of forest lands is the solution to multiple use conflicts among forest land uses and users? A brief history of the origin and implementation of New Zealand's forest privatization policy is given, including the disestablishment of its national Forest Service. Two unique features of New Zealand made privatization especially appropriate there: the history of many government-operated businesses, and the great area and productivity of a very distinctive and differentiated forest type—radiata pine plantations. Nine objectives of privatization stated in New Zealand, 5 specifically on forestry, are analyzed. Six of the 9 were concluded to be successful in New Zealand. Possibilities of success in the United States are examined. As a solution for multiple-use problems, both positive and negative results of the policy are found. Finally, 6 tentative "lessons" are concluded that should be reviewed in countries where a similar policy is proposed: 1. Privatization should involve either leasing or fee simple sale of forested land primarily suited to rapid tree growth of commercially valuable species suitable for being managed for successive crops of timber at a profit, with covenants for regeneration after harvest. 2. Lands critical for recreational, aesthetic, or habitat values should remain publicly owned. 3. Lands on which re-investment of some of the income in regeneration is of questionable profitability should not be entered into the policy. 4. The policy could be successful in avoiding many but not all multiple-use conflicts for the managers. 5. In public forests retained for exclusively noncommodity uses, questions of the availability of some useful and valuable woods may require arbitration of conflicts. 6. Privatization doesn't solve the struggle to financially support park and wilderness and special wildlife habitat. For. Sci. 43(2):181-193.

A Qualitative Comparison of Fire Spread Models Incorporating Wind and Slope Effects - David R. Weise; Gregory S. Biging (Forest Science, 1997)
Wind velocity and slope are two critical variables that affect wildland fire rate of spread. The effects of these variables on rate of spread are often combined in rate-of-spread models using vector addition. The various methods used to combine wind and slope effects have seldom been validated or compared due to differences in the models or to lack of data. In this study, rate-of-spread predictions from the Canadian Fire Behavior Prediction (FBP) system, McArthur's Mark V forest fire danger meter, the Rothermel empirical model, and the Pagni and Peterson physical model were compared with spread rates observed in a designed laboratory experiment in which wind velocity and slope were varied. Methods of combining wind and slope developed by Albini, McAlpine, and Rothermel were applied to two forms of Rothermel's model. Rothermel's model (original and modified) coupled with Albini's method and Pagni's model predictions closely reproduced the observed shape of the rate-of-spread response to wind and slope. Rothermel's method and McAlpine's method worked well in all cases except in upslope spread with opposed flow. However, Rothermel's model failed to predict a nonzero rate of spread in fuel beds with moisture contents of 35%. Possible causes of overprediction by McArthur's model and the FBP model included: (1) application of equations derived from full-scale fires to laboratory-scale fires, (2) improper selection of fuel type to represent artificial fuel beds, and (3) inaccurate estimation of wind velocity 10 m above the vegetation surface using a logarithmic profile. For. Sci. 43(2):170-180.

Using Tabu Search To Generate Stand-Level, Rule-Based Bucking Patterns - Andre J. Laroze; Brian J. Greber (Forest Science, 1997)
A Tabu Search (TS) heuristic was developed for generating easily implementable bucking rules that are applicable to entire stands (as opposed to individual stem classes), and for selecting the rule-set that provides the best feasible solution (given log prices and market constraints). The tabu restrictions used for guiding the search process are based on the frequency of the export logs' attributes, and the profit corresponding to the local optima found during the search. Parallel tabu lists of different time-spans were considered. The aspiration criterion for revoking a tabu status consisted of improving upon the best feasible solution. The model was applied to a set of radiata pine (Pinus radiata, D. Don) stands, considering different market constraints and price sets. The TS approach leads to bucking outcomes that are reasonably close, in profit terms, to the solutions obtained by an integer programming model designed for selecting the optimal set of stem-specific bucking patterns. For. Sci. 43(2):157-169.

Back Matter Volume 43 Issue 2 1997 (Forest Science, 1997)

Front Matter Volume 43 Issue 2 1997 (Forest Science, 1997)

Nature and the Human Spirit: Toward an Expanded Land Management Ethic - Theresa L. Wang (Forest Science, 1997)

Aggregation Procedures in Forest Management Planning Using Cluster Analysis - Andrés Weintraub; Guillermo Sáez; Marisa Yadlin (Forest Science, 1997)
Typical linear programming models used in forest planning can be very large. It is often of interest to analyze more compact, less detailed versions. One form of reducing the size of the problem is through an aggregation process. One way in which this has been done is through a column aggregation process, where sets of similar columns are replaced by one representative. A second alternative is to aggregate the original data, in which case the stands and management alternatives are grouped before building a model. Typical approaches for the aggregation processes have been analytical. We present an alternative approach for aggregation based on cluster analysis. Computational results for both types of aggregation show that using cluster analysis can be advantageous. For. Sci. 43(2):274-285.

Growth, Development, and Yield in Pure and Mixed Stands of Eucalyptus and Albizia - Dean S. Debell; Thomas G. Cole; Craig D. Whitesell (Forest Science, 1997)
Productivity of Eucalyptus saligna Sm. plantations is commonly limited by low levels of available nitrogen (N), and synthetic N fertilizer applications are costly and sometimes impractical; thus, we evaluated mixed species plantings in which N is added by Albizia falcataria (L.) Fosberg [=Paraserianthes falcataria (L.) Nielson]. Five ratios of Eucalyptus and Albizia were compared with each other, with pure Albizia, and with pure Eucalyptus fertilized periodically with N in a randomized block design on the wet Hamakua coast of the Island of Hawaii. Eucalyptus growth increased as the amount of Albizia in the stand increased from 11 to 66%, and heights and diameters of Eucalyptus in stands containing 34% or more Albizia were equal to or larger than those in fertilized, pure stands. Total aboveground biomass, stem biomass, and stem volume per ha of mixed stands at age 10 were at least equal to yields produced in fertilized, pure Eucalyptus stands; total biomass of mixed stands with 50 or 66% Albizia was 30 and 46% greater than that in fertilized, pure Eucalyptus and 10 and 24% greater than that of pure Albizia. Yield of the Eucalyptus component alone in these two mixtures was at least equal to that of fertilized, pure Eucalyptus stands. Moreover, mean annual increment declined more slowly after culmination in all-mixed stands than in the fertilized, pure Eucalyptus stand. Over time, the apparent benefits of mixed versus pure plantings of Eucalyptus and Albizia have increased, and at age 10 include diversity in stand structure (and habitat) as well as the improvements in Eucalyptus tree growth and stand productivity recognized at younger ages. For. Sci. 43(2):286-298.

Impacts of Timber Harvesting on Soil Organic Matter, Nitrogen, Productivity, and Health of Inland Northwest Forests - M. F. Jurgensen; A. E. Harvey; R. T. Graham; D. S. Page-Dumroese; J. R. Tonn; M. J. Larsen; T. B. Jain (Forest Science, 1997)
Soil organic components are important factors in the health and productivity of Inland Northwest forests. Timber harvesting and extensive site preparation (piling, windrowing, or scalping) reduces the amount of surface organic material (woody residues and forest floor layers) over large areas. Some wildfires and severe prescribed burns can have similar consequences. Such organic matter reductions can have important implications for soil chemical, biological and physical properties. A number of studies have linked substantial reduction in mycorrhizae development and tree growth to high levels of soil disturbance, or removal of organic horizons. Timber harvesting also removes a large percentage of coarse woody debris, which has unknown ramifications on soil productivity. Current woody residue guidelines in this region recommend leaving <10 to 125 Mg ha-1 on site to replace woody materials lost during harvesting operations. Large amounts of soil nitrogen (>500 kg ha-1) can also be lost from timber harvesting and site preparation, especially when using prescribed fire. The time required to replace this lost nitrogen may range from <10 to >275 yr, and depends on the severity of site treatments, presence or absence of nitrogen-fixing plants, and amounts of atmospheric deposition. Maintaining adequate amounts of organic matter on some forest sites in the Inland Northwest may temporarily increase the risk of wildfire or favor the activity of certain insects or disease fungi. However, carefully planned prescribed burns and mechanical site preparation can be practiced on most sites with relatively low impacts on soil organic levels, while accomplishing the important forest management objectives of fuel reduction, seedbed preparation, and reducing competing vegetation. Organic matter management will be the most difficult on very dry sites, with their historically low soil organic and nitrogen content, and high fire potential. The maintenance of adequate soil organic matter levels is critical for sustaining forest health and productivity under the variable moisture and temperature conditions of this region. Thus, soil organic components will become more important in the future as ecosystem management systems are developed for western forests. For. Sci. 43(2):234-251.

Brief Notices: The Ecology of a Tropical Forest: Seasonal Rhythms and Long-Term Changes (Second Edition) - Egbert G. Leigh; A. Stanley Rand; Donald M. Windsor (Forest Science, 1997)

Upcoming Reviews (Forest Science, 1997)

Brief Notices: A Wood of Our Own - Julian Evans (Forest Science, 1997)

Brief Notices: Ecosystem Management in the United States: An Assessment of Current Experience - Steven L. Yaffee; Ali F. Phillips; Irene C. Frentz; Paul W. Hardy; Sussanne M. Maleki; Barbara E. Thorpe (Forest Science, 1997)

Book Reviews: Boreal Forests and Global Change - John C. Zasada (Forest Science, 1997)

Book Reviews: Water Relations of Plants and Soils - William C. Carlson (Forest Science, 1997)

Book Reviews: The Literature of Forestry and Agroforestry - Carol C. Green (Forest Science, 1997)

Book Reviews: Agroforestry: Science, Policy and Practice - Angus W. Brodie (Forest Science, 1997)

Book Reviews: Land Mosaics: The Ecology of Landscapes and Regions - Louis Iverson (Forest Science, 1997)

Book Reviews: Science and Ecosystem Management in the National Parks - J. K. Agee (Forest Science, 1997)

Notes: Pollen Tube Growth in Quercus - Robert A. Cecich (Forest Science, 1997)
Fluorescence and brightfield microscopy were used to evaluate pollen tube growth in the Erythrobalanus and Lepidobalanus subgenera of the genus Quercus. All three species had the same pattern of pollen tube growth behavior, from the time pollen landed on the stigmas to the cessation of pollen tube elongation in mid-May. Pollen tubes grew from the apertures, penetrated the stigmatic epidermis, and produced a series of callose plugs as they advanced basipetally through the transmitting tissue of the styles. Pollen tubes grew through the solid transmitting tissue until they reached the level of the visible portion of the perianth, where the three styles join. In white oak, the arrested pollen tubes resumed growth in early June, and fertilization occurred during the week of June 11. In northern red oak and black oak, resumption of pollen tube growth occurred in the following growing season. Pollen tubes of northern red oak resumed growth in the May 22 collections and fertilization occurred during the week of June 12. In black oak, however, pollen tubes resumed growth in the June 5 collections and fertilization occurred in late June. The control over pollen tube elongation may be environmental or sporophytic. For. Sci. 43(1):140-146.

Wildlife Conservation Planning Using Stochastic Optimization and Importance Sampling - Robert G. Haight; Laurel E. Travis (Forest Science, 1997)
Formulations for determining conservation plans for sensitive wildlife species must account for economic costs of habitat protection and uncertainties about how wildlife populations will respond. This paper describes such a formulation and addresses the computational challenge of solving it. The problem is to determine the cost-efficient level of habitat protection that satisfies a viability constraint for a sensitive wildlife population. The viability constraint requires a high probability of attaining a population size target. Because of the complexity of wildlife prediction models, population survival probabilities under alternative protection plans must be estimated using Monte Carlo simulation. The computational challenge arises from the conflicting effects of sample size: fewer replications used to estimate survival probability increases the speed of the search algorithm but reduces the precision of the estimator of the optimal protection plan. Importance sampling is demonstrated as a simulation technique for reducing estimator variance for a given sample size, particularly when the tail of the population distribution is of critical importance. The method is demonstrated on a hypothetical problem involving gray wolf management in the Great Lakes region of the United States. In comparison to random sampling, importance sampling produces a 21-fold reduction in the variance of the estimator of the minimum-cost protection plan. Results from the optimization model demonstrate the extreme sensitivity of the minimum-cost protection plan to the structure of the growth model and the magnitude of environmental variation. This sensitivity is not widely recognized in the literature on wildlife habitat planning and is a strong reason for using optimization methods that can handle stochastic population models with a wide range of structures. For. Sci. 43(1):129-139.

Back Matter Volume 43 Issue 1 1997 (Forest Science, 1997)

Front Matter Volume 43 Issue 1 1997 (Forest Science, 1997)

Inoculation of Tree Roots with Plant Growth Promoting Soil Bacteria: An Emerging Technology for Reforestation - C. P. Chanway (Forest Science, 1997)
Seedling root systems are colonized heavily by asymbiotic soil bacteria, many of which have the potential to influence plant growth significantly. A heterogeneous group of these microorganisms is well known for their ability to colonize roots and stimulate growth of agricultural plant species, sometimes doubling seedling biomass accumulation only a few weeks after inoculation, but more usually resulting in less spectacular biomass gains (e.g., 15%-30% greater than uninoculated controls within a growing season). Plant growth promoting soil bacteria may exert such effects through a variety of mechanisms, and include microorganisms that stimulate seedling emergence or infection by symbiotic fungi and bacteria. Other plant beneficial soil bacteria possess biological control activity or are capable of transforming plants genetically. Inoculation of tree seedlings with such bacteria before outplanting would be an inexpensive, environmentally benign, and easily applied nursery treatment, but comparatively little work has been performed with these microorganisms in forestry. Recent results with various tree species, however, indicate that seedling performance can be significantly enhanced through bacterial inoculation of root systems: pine and spruce biomass increased 32%-49% 1 yr after inoculation and outplanting at a reforestation site. In addition, infection by desired species of ectomycorrhizal fungi can also be enhanced by inoculation with certain strains of root colonizing bacteria. Results from studies performed with beneficial asymbiotic tree root associated bacteria are reviewed in this article in relation to the possible uses of such microorganisms for artificial forest regeneration. For. Sci 43(1):99-112.

Trends in Genetic and Environmental Parameters for Height, Diameter, and Volume in a Multilocation Clonal Study with Loblolly Pine - A. D. Paul; G. S. Foster; T. Caldwell; J. McRae (Forest Science, 1997)
Seedlings from 30 full-sib families (contained in 2, 4 x 4 factorials) of loblolly pine (Pinus taeda L.) were cloned and planted in three test sites in Georgia. Analyses were conducted on total height at ages 1 to 5 yr in the field, dbh at age 5, and individual tree volume at age 5. Four sources of genetic control were tested: male parent, female parent, male x female parent interaction, and clone within family. Differential growth responses due to test sites were present. Significant differences were detected among male parents for only one (age 5 height) of the seven traits in only one factorial. However, variation for height among female parents was found at ages 1 to 5 in only one of the two factorials accounting for 1% to 9% of the total variation. Significant effects of clone within family were found at all ages in one factorial and at ages 1, 3, and 4 in the other factorial for height but not for dbh or individual tree volume. None of the parental sources (male, female, or male x female) were interactive with test sites except one isolated case at age 2 in one factorial. However, the clone within family source of variation interacted significantly with site for height at ages 3 to 5 in factorial 1. Differences due to male or female parent effects were somewhat lower than has been found in other similar studies, possibly due to the relatively low number of parents in both factorials and hence, sampling effects. Future genetic studies should include more parents in the mating design but with approximately the same number of cloned individuals per cross in order to provide a better test of sources of variation. Trends in genetic and environmental variances and heritabilities were examined. Additive genetic variance (VA')for tree height displayed a steady increase from age 1 to 5. Dominance genetic variance (VD') for height also increased steadily over the same age range. The relationship between VA' and VD' differed between the two factorials. In factorial 1, VA' was larger than VD' for ages 1 to 4, then VD' became larger for age 5. The reverse pattern occurred in factorial 2. Epistatic genetic variance was detected only at age 1 for height in factorial 1 and at ages 1 and 3 in factorial 2. Dominance variance equaled or exceeded additive genetic variance for dbh and individual tree volume at age 5. Narrow-sense and broad-sense heritabilities for height were low to intermediate (0.05 to 0.37) from ages 1 to 5 and were more or less stable over ages. The importance of dominance genetic variance, at least to age 5, underscores the likelihood of additional genetic gains through a clonal tree improvement and deployment program beyond the gains achieved in a seed orchard/seedling based program. For. Sci. 42(1):87-98.

A Stochastic Model for Tree Survival in Stands Affected by Annosum Root Disease - Haiganoush K. Preisler; Garey W. Slaughter (Forest Science, 1997)
Mortality of trees surrounding pine stumps colonized by Heterobasidion annosum for about 35 years was monitored over a period of 20 yr in 53 eastside pine stands in northern California. The data were used to develop a stochastic model that quantifies effects of tree characteristics and spatial proximities on survival of trees within 12 m of a colonized stump. The model accommodates mortality data collected at irregular intervals. Variables with significant effects on tree survival included trees species, size, and distance of roots from the root of a previously dead tree. Results from stochastic models based on actual data are useful for detecting factors affecting tree survival and for evaluating assumptions of numerical (simulation) models, such as root disease computer models. For. Sci. 43(1):78-86.

Regression Methods for Spatially Correlated Data: An Example Using Beetle Attacks in a Seed Orchard - Haiganoush K. Preisler; Nancy G. Rappaport; David L. Wood (Forest Science, 1997)
We present a statistical procedure for studying the simultaneous effects of observed covariates and unmeasured spatial variables on responses of interest. The procedure uses regression type analyses that can be used with existing statistical software packages. An example using the rate of twig beetle attacks on Douglas-fir trees in a seed orchard illustrates the problem and the recommended statistical procedures. Use of this procedure revealed spatial patterns in beetle attacks that were not otherwise evident. We also found that the covariates, tree vigor, cone crop, and host genotype (i.e., clone) apparently had significant effects on number of beetle attacks within a model that also included location effects. This procedure should prove useful in other situations where spatial trends are of interest in themselves and are not simply viewed as nuisance parameters to be dealt with by the proper experimental design. For. Sci. 43(1):71-77.

Using Pheromone-Baited Traps To Control the Amount and Distribution of Tree Mortality During Outbreaks of the Douglas-Fir Beetle - Darrell W. Ross; Gary E. Daterman (Forest Science, 1997)
Multiple-funnel traps baited with strong aggregation pheromone lures were placed throughout three 259 ha plots in northeastern Oregon during an outbreak of the Douglas-fir beetle, Dendroctonus pseudotsugae Hopkins. Mean numbers (± SEM) of Douglas-fir beetles collected per plot for the entire flight periods of 1992 and 1993 were 277,921 ± 40,447 and 268,834 ± 37,088, respectively. Mean numbers (± SEM) of the most abundant predator, Thanasimus undatulus (Say), collected per plot in 1992 and 1993 were 43,527 ± 3,553 and 35,652 ± 3,514, respectively. Douglas-fir beetle-caused tree mortality was concentrated around the trap sites in the treated plots, even though traps were located an average of 40 m from the nearest host tree. Managers can influence the spatial distribution of tree mortality during an outbreak by selective placement of traps across the landscape. Selective trap placement, plus the removal of trapped beetles from the population, may reduce tree mortality within the general area. For. Sci. 43(1):65-70.

Public Acceptability Thresholds of Clearcutting to Maintain Visual Quality of Boreal Balsam Fir Landscapes - Joséet Pâquet; Louis Bélanger (Forest Science, 1997)
Clearcutting transforms forest landscapes by creating important visual contrasts between cut areas and adjacent stands. The object of this study was to determine if it is possible to harvest a certain proportion of the visible landscape while maintaining a visually acceptable setting in the social and ecological context of the boreal balsam fir (Abies balsamea L. Mill.) forest of central Québec. Using an adaptation of the Scenic Beauty Estimation (SBE) method, a survey was conducted through slide presentations to 309 persons from 11 groups of forest users. Levels of acceptability for single-patch and dispersed-patch cutting strategies were established for this ecosystem. The results confirmed that an increase in the percentage of clearcut areas in the visible landscape induced a lower level of acceptability and that even a small clearcut created a visual impact. However, despite a generally unfavorable reaction to clearcuts, a certain level of landscape alteration was acceptable to the tested groups. When clearcuts were in the form of a single patch, the acceptability threshold of the user groups was reached at an average percentage of 25% of the visible landscape harvested by clearcutting. The dispersed-patch strategy reduced the negative visual impact; for 6 of the 11 groups, the acceptability threshold increased to a harvesting level of 50%. To remain visually acceptable, clearcuts must be in a subdominant position in the visible landscape. The visual impact of a clearcut is effectively mitigated when the vegetation has reached a minimum height of 4 m. For. Sci. 43(1):46-55.

Output Supply and Input Demand in the Pulp and Paper Industry: A Nonparametric Model for the United States and Canada - Jiing-Shyang Hseu; Joseph Buongiorno (Forest Science, 1997)
Demand and supply relationships are needed to understand the economics of the pulp and paper industry and to make forecasts of inputs, outputs, and prices. Here, long-run supply and demand elasticities were derived with a nonparametric method exploiting the consequences of the weak axiom of profit maximization (WAPM). No assumption was required regarding the form of the profit function, and all own-price elasticities necessarily had the expected theoretical signs. But, an infinite number of quantity responses being consistent with the theory and data, finding a unique response required a new assumption: that quantities adjusted just enough to satisfy the WAPM. The data pertained to the pulp and paper industries of the United States and Canada from 1959 to 1987. They recognized four outputs and nine inputs. A price shock of 20% led to elasticities that closely satisfied local homogeneity of the supply/demand functions, and symmetry of their price derivatives. Output supplies were all elastic, or nearly so, with respect to their own prices. The own-price elasticities of input demand ranged from -0.4 to -2.2, demand for capital being one of the most elastic. Cross-price elasticities tended to be small. The method was also applied to make out-of-sample forecast of inputs and outputs conditional on observed prices, under nonregressive technical change. Forecasts for 1983 to 1987 were generally unbiased. A synthesis of parametric and nonparametric methods is still needed to improve forecasts. For. Sci. 43(1):35-45.

Stochastic Models for Conifer Tree Crown Profiles - Gregory S. Biging; Samantha J. Gill (Forest Science, 1997)
We perform a feasibility study of using stochastic models to describe the profile of tree crowns and to capture the stochastic nature of the tree crown form for five conifer species of the Sierra Nevada. In 70% of the cases investigated we found that we could model tree crown profiles as a quadratic or cubic trend in conjunction with a simple autoregressive moving average model (ARMA). In the remaining cases we used a quadratic or cubic trend in conjunction with white noise. These stochastic ARMA models are visually and statistically an improvement over using Euclidean geometric crown profile models. Competing models were judged by using Akaike's Information Criterion (AIC) to achieve a parsimonious model. It was found that first-order moving average MA(1) models or first-order autoregressive AR(1) models were adequate for modeling the majority of the cases studied and that these models were qualitatively similar. MA(1) models were preferred over the AR(1) models because less information is required to simulate them. For. Sci. 43(1):25-34.

A Carbon Balance Model of Growth and Self-Pruning in Trees Based on Structural Relationships - Annikki Mäkelä (Forest Science, 1997)
A tree growth model is formulated based on structural relationships in a carbon balance framework. Three relationships are applied: (1) an allometric relationship between crown surface area and foliage area, (2) the principle of functional balance, and (3) the pipe-model theory. These assumptions lead to a model where the sizes of the functional parts of the tree are derivable from foliage weight, except for the pruning height of the crown. This is determined by defining a "self-pruning coefficient," which controls the allocation of growth between height growth and foliage growth. The tree model is applied to an average-tree based stand growth model where both the self-pruning coefficient and tree mortality are made functions of crown coverage. The model is quantified for Scots pine growing in southern Fenno-Scandia. The overall behavior of the model is realistic. The model responds to stocking density through the rate of self-pruning, lower stocking densities leading to larger crown ratios. It also responds to changes in parameters describing site quality in a realistic way, although the differences in stand density are not as large as expected. The predicted development of the biomass compartments in individual trees agrees well with data on dominant Scots pine trees in Finland. For. Sci. 43(1):7-24.

Editor's Annual Report (Forest Science, 1997)

An Optimization Approach to Area-Based Forest Pest Management Over Time and Space - John Hof; Michael Bevers; Brian Kent (Forest Science, 1997)
This paper discusses spatial optimization approaches to managing aggressively reproducing and dispersing pests. The relevant land planning area is divided into cells, and pest growth and dispersal across those cells are accounted for in integer programs that include choice variables for applying control treatments to those cells. Two model formulations are developed and demonstrated in a simple case example: one that assumes no limit to host capacity and one that assumes a limit to host capacity accumulated over time. The formulation with no host capacity limit is shown to be potentially unrealistic if control treatments are not limited. Different objective functions and amounts of control treatment result in optimal strategies that vary from immediate containment near the pest's origin to delayed containment at an area away from the pest's origin. Both formulations are difficult to solve, reflecting the exploratory nature of this paper. For. Sci. 43(1):121-128.

Long-Run Timber Supply and the Economics of Timber Production - Runsheng Yin; David H. Newman (Forest Science, 1997)
The analysis of long-run timber supply is hampered by the lack of a well-defined profit function. Such a function provides the foundation for deriving a theoretically consistent supply equation. Some recent studies have attempted to obtain a timber supply equation by manipulating the stand-level Faustmann model. As a result of inappropriate approaches and assumptions, their conclusions may be false. In this article, we build on the Faustmann-Smith-Samuelson model first developed by Comolli (1981) to examine aggregate timber production. We show this model to have the desired properties of a profit function that allows us to test various issues. It is then found that the general beliefs of negatively sloped per-land-unit supply curves and positively sloped aggregate supply curve are robust. Finally, we present several applications and implications of our modeling approach. For. Sci 43(1):113-120.

Leaf Area-Productivity Relationships Among Mixed-Species Hardwood Forest Communities of the Central Hardwood Region - Shibu Jose; Andrew R. Gillespie (Forest Science, 1997)
A study was conducted to quantify the influence of environmental factors on the leaf area-productivity relationships of Ecological Land Type Phases (ELTPs) representing Central Hardwood forest communities. Forest inventory data were collected from 83 plots taken along a moisture gradient, stratified within recognized ELTPs in the Hoosier National Forest in southern Indiana. Density (standing basal area, volume, and biomass), annual production, leaf area index (LAI), and water balance indices were determined for each ELTP. Ecological Land Type Phases showed marked differences in density and growth measures which were positively correlated with leaf area index. Leaf area index, in turn, exhibited strong correlations with site and environmental factors. Further, a reduction in canopy-average specific leaf area with decreasing soil moisture and LAI was observed. In general, maximum growth efficiency (measured as growth per unit of LAI) was attained at a LAI of approximately 3.5, after which it decreased. However, no significant differences in growth efficiency were found among ELTPs, suggesting that the communities were adjusting to differences in resource availability, particularly water. Thus, these mixed-species forest communities adjust both species composition and canopy morphology to compensate for changing environmental gradients. For. Sci. 43(1):56-64.