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Forest Science, Volume 46, Number 4, November 2000 Centroid Method: Comparison of Simple and Complex Proxy Tree Taper
Functions ABSTRACT. Cubic-meter volumes estimated from simple and complex proxy taper functions were compared to observed volumes of loblolly pine (Pinus taeda, L.) and ponderosa pine (Pinus ponderosa, Dougl. ex Laws.) trees to evaluate accuracy (bias and precision) in the centroid method. The results of this investigation showed no clear evidence that a more complex proxy taper function is more accurate than a simple function. The results also support previous studies that show accurate volumes of standing trees may be obtained using the centroid method, which requires only one upper-stem diameter measurement. FOR. SCI. 46(4):473-477. Determination of Stand Properties in Boreal and Temperate Forests
Using High-Resolution Imagery ABSTRACT. The existence of a relatively long (ca. 40 yr) satellite imagery archive for examination of potential worldwide forest change motivated an inspection of the relation between forest features observable from higher resolution airborne and satellite imagery and measures of forest biomass, height, and age. Using these data, we inspected the relation between stand age, mean diameter, height, and standing aboveground biomass for forest stands located in boreal forest (near Fairbanks, Alaska) and temperate forest (near Durham, North Carolina). The features of a spatial statistic, semivariance, prove to be related to the structure, age, and biomass patterns of these forests. These initial results indicate the feasibility of using appropriately calibrated high-resolution satellite imagery to estimate and monitor aboveground carbon reserves of forests. FOR. SCI. 46(4):478—486. Genotypic Stability and Genetic Parameters for Growth and Biomass
Traits in a Water ABSTRACT. The objective of this experiment was to study
genotypic stability for growth and biomass traits recorded in treatments
with optimal and limiting water availability at two different
temperatures and to study how the different growth environments affected
genetic parameter estimates. Open-pollinated families of Scots pine
(Pinus sylvestris L.) were collected in 2 seed orchards with 28 and 35
families respectively and cultivated for 1 growth period in a growth
chamber. Heritability estimates were generally moderate-high (h2 =
0.3-0.8) for growth traits in individual treatments. Joint analyses of
all treatments revealed significant family A Travel Cost Analysis of Nonconsumptive Wildlife-Associated
Recreation in the United States ABSTRACT. Increased emphasis on sustainable resource management in forestry has effectuated a demand for various nontimber values. Nonconsumptive wildlife recreation is an important nontimber service produced on forest and rangeland. Travel cost models and data from the 1991 National Survey of Fishing, Hunting and Wildlife-Associated Recreation are used to estimate the demand and value for nonconsumptive wildlife-associated recreation in the United States. Resulting welfare measures are shown to be sensitive to assumptions about the cost of travel time, pecuniary costs, and functional form. Consumer surplus estimates range from 18.7 to 327.5 dollars per trip, while aggregate estimates of consumer surplus resulting from access to nonconsumptive wildlife recreation range from 5.8 to 66.4 billion dollars annually. Availability of information about nonparticipants allows comparison of truncated and untruncated demand models. Contrary to previous findings, consumer surplus estimates from truncated models are smaller than for untruncated counterparts. Trip demand is found to be adversely affected by per capita decreases in forest and rangeland. Models include interaction variables to avoid forcing hunting or fishing as potential substitutes for the large number of people who do not hunt or fish. Hunting and nonconsumptive wildlife recreation are complementary activities, while the results for fishing are mixed. FOR. SCI. 46(4):496—506. Persistence of Growth Variation in Tree-Ring
Chronologies ABSTRACT. We infer baseline response to climate of the growth of trees in California dendroclimatological samples, adopting linear and nonlinear approaches and using the expected accumulated impact of a state change as one measure of persistence. Many samples exhibit two quite distinct growth states. Timing of high and low growth states is highly heterogeneous across locations, and regional aggregation seriously understates the size and persistence of local growth changes. If climate is a dominant factor in local tree growth, then local climate is not well represented by an aggregate regional index. FOR. SCI. 46(4):507—520. Emergy Evaluation of Reforestation Alternatives in Puerto
Rico ABSTRACT. Six alternative ways of reforesting degraded lands in Puerto Rico were evaluated using emergy (spelled with an "m"). Emergy and its economic equivalent, emdollars, put the contributions of environmental work and human services on a comparable basis. This article shows the emergy method for evaluating forest contributions to public benefit and its use to select alternatives for reforestation. Emdollar values were compared for six scenarios for reforestation of degraded land in Puerto Rico: (1) the natural succession within or adjacent to mature forest; (2) reforestation from the spread of the exotic tree siris(Albizia lebbek); (3) reforestation with plantations of siris and mahogany for harvest; (4) reforestation by leaving plantations unharvested; (5) direct planting of seedlings of many species; and (6) starting patches of forest by massive transfer of topsoil, seed bank, and roots. After energy systems diagrams were made for each reforestation alternative, data were assembled and evaluation tables prepared that estimated the emergy required for: (1) canopy closure and (2) developing species complexity if left unharvested. To explain the method, detailed calculations were included for one of the alternatives, exotic Albizia lebbek plantation on 11 yr harvest cycle. All alternatives generated net public benefit (emdollar yield ratios 4.2 to 24.3). The emdollar value of a closed canopy developed in 10 to 20 yr ranged from 20,000 to 48,000 em$ /ha, whereas the economic costs were $1200 to $9700. For complex forest development in 25 to 60 yr, values ranged from 63,000 to 118,000 em$ /ha, much higher than economic costs of $4000 to $12,000/ha. Highest public benefit per dollar cost came from succession (24.7 em$/$) and exotic colonization (19.1 em$/$). Highest potential monetary returns were from exotic spread (15.1 $/$) and plantations (17.9 and 14.5 $/$). Stand quality after 60 yr, as measured by the transformity (emergy/energy), was largest in mahogany plantation (6.4 x 104 sej/J) and succession forest (3.9 ¥ 104 sej/J). FOR. SCI. 46(4):521—530. Root Chemistry of Mature Douglas-Fir Differs by Habitat Type in
the Interior Northwestern United States ABSTRACT. Carbon compound concentrations in plant tissues depend on the environment in which plants grow. However, little is known about how these concentrations vary across a range of forest environmental conditions. Our study examined root tissue (phloem, cambium, phellum, and phelloderm) collected from naturally regenerated mature Douglas-fir (Pseudotsuga menziesii var. glauca [Bessn.] Franco) trees in eight stands on three habitat type series encompassing a range of temperature and moisture conditions. The objective was to determine root chemical composition (sugar, starch, phenol, and tannin) differences among the habitat types. Douglas-fir roots collected from dry, warm Douglas fir habitat types had sugar concentrations of 4% compared to 3% for roots from cool, moist habitat types. Root samples collected from Douglas-fir habitat types showed tannin concentrations about double those from grand fir or western redcedar habitat types. Phenol/tannin ratios for the cool, moist habitat types were about double those from warm, dry Douglas-fir habitat types. Roots sampled from western redcedar habitat types had phenol concentrations and phenol/sugar ratios more than 50% higher than those from Douglas-fir and grand fir habitat types. We speculate that root chemistry of Douglas-fir growing on Douglas-fir habitat types could make them more drought resistant but less disease resistant, while Douglas-fir growing on western redcedar types would be less drought resistant but more disease resistant. Douglas-fir growing on warm, dry sites allocated more carbon to tannin production and less to phenols. FOR. SCI. 46(4):531—536. An Econometric Analysis of Norwegian Sawmilling 1974-1991 Based on
Mill-Level Data ABSTRACT. An eight-input translog total cost function was estimated, and the estimates were used to calculate Allen and Morishima substitution elasticities, price elasticities of conditional input demands, elasticity of size, and technical change for Norwegian sawmilling at a five-digit disaggregate industry level, based on an unbalanced panel of 3,090 individual observations of sawmills over the period 1974-1991. The unusually rich source of data made it possible to analyze the production economics of sawmilling in more detail than has ever been possible before. As far as comparisons with other studies could be made, many of the Allen substitution elasticities and price elasticities of conditional input demand were in accordance with previous findings. The inputs were found to be inseparable. Therefore, frequently used overall aggregates like "materials" and "energy" are not to be recommended. Since the average sawmill had economies of size yet to be exploited, it would have been better off by increasing its size. The most effective way of doing this is to use relatively more sawlogs, electricity, capital, and the aggregate other inputs, and relatively less labor, lumber input (for planing), and the aggregate input other materials. The rate of technical change was negative for the average sawmill. FOR. SCI. 46(4):537—547. Estimating Metrics of Forest Spatial Pattern from Large Area
Forest Inventory Cluster Samples ABSTRACT. The interest in ecologically meaningful information from forest inventories is increasing. Forest area and its characteristics of spatial distribution are among this information. This paper describes a technique for deriving some metrics of forest spatial pattern from nonmapped forest inventory samples. The technique is developed for clusters of subplots, though applicable also for other plot types. It evaluates the area of the three categories: forest, nonforest, and buffer, estimated by the percentage of cluster plots where all, none, or some subplot centers fall into forest. Of particular interest is the buffer area, which is an imagined strip along the forest boundary: the larger this area, the more forest boundaries there are, and the more fragmented the forest pattern is. The estimates of forest and buffer area percentage are used to derive metrics that are related to perimeter length and mean patch size. Variance estimators for these metrics are given. Two examples are presented to illustrate the characteristics of the method, one with a schematic map, one with real inventory data. The most meaningful results are obtained when the size of the cluster plots used is smaller than the forest patches and smaller than the distance between them. The examples suggest that, in order to obtain reasonably precise estimates, sample size should be n = 500 or more. These conditions commonly hold in large area forest inventories. The technique processes information that is readily available from the field measurements of large area forest inventories. It does not require extra measurements and adds an ecologically meaningful aspect to the data analysis. It is independent of the availability of complete maps of the inventory region or of mapped plots, and therefore also allows the retrospective analysis of old forest inventory sample data. FOR. SCI. 46(4):548—557. Alternative Measurements of Productive Efficiency in the Global
Bleached Softwood Pulp Sector ABSTRACT. In this article, we conduct a productive efficiency analysis using the two major methods: stochastic frontier analysis (SFA) and data envelopment analysis (DEA). First, we demonstrate the steps and assumptions involved in SFA and DEA, and highlight their strengths and weaknesses. Then we apply them to the case of bleached softwood kraft pulp production to derive technical and allocative efficiency measures for 102 mills in the world. We find that in general, the SFA cost-efficiency levels are higher than their DEA counterparts, and much of the cost inefficiency is caused by inappropriate input mix, or allocative inefficiency, instead of the way with which inputs are converted into outputs, or technical inefficiency. In addition, SFA and DEA results rank some of the producers in different orders. We also find that while cost-efficiency levels vary in different regions, most producers have substantial opportunities to make improvements. Finally, we discuss implications of our study. FOR. SCI. 46(4):558—569. A Review of Past Research on Dendrometers ABSTRACT. The purpose of a dendrometer is to measure tree diameter. Contact and noncontact dendrometers accomplish this task by collecting different metrics, including girth or distance between tangent points on a tree stem. Many dendrometers have been developed in the last quarter century and many have been retired. This article summarizes instrument developments and application results, contains an interpretation of the results, and provides guidance for dendrometer selection. FOR. SCI. 46(4):570—576. Measuring the Performance Improvement of Taiwan Forests after
Reorganization ABSTRACT. The data envelopment analysis (DEA) approach has been widely applied to measure the relative efficiencies of decision making units (DMUs) for a time period. This article measures the performance improvement of a DMU at two time points by using the DEA approach. Two ideas are proposed. One is to treat one DMU at two time points as two different DMUs, and the ratio of the efficiency scores of a DMU at two time points serves as a measure of the efficiency improvement. The other is to calculate the Malmquist productivity index of a DMU to represent its productivity improvement. Both the efficiency ratio and the productivity index can be decomposed into the technical part and the scale part. From the data of the eight forest districts of Taiwan compiled in 1989 and 1992, the efficiency and productivity improvement in these two periods are measured. The results of the two methods are consistent in that both indicate a slight improvement in performance. FOR. SCI. 46(4):577—584.
Forest Science, Volume 46, Number 3, August 2000 Modeling the Size-Density Relationship in Direct-Seeded Slash Pine
Stands ABSTRACT. The relationship between quadratic mean diameter and tree density appeared curvilinear on a log-log scale, based on data from direct-seeded slash pine (Pinus elliottii var. elliottii Engelm.) stands. The self-thinning trajectory followed a straight line for high tree density levels and then turned away from this line as tree density decreased. A system of equations was developed to model the reciprocal effects of stand diameter and density through time. The equations performed well for these data. Since the model is constrained according to the self-thinning rule, it should provide reasonable extrapolation. FOR. SCI. 46(3):317-321. The Economics of Prescribed Burning: A Research
Review ABSTRACT. Prescribed burning has, in the past decade, become the focus of debate among policy makers, federal and private land managers, and the public. To manage fire effectively, the USDA Forest Service has formally recognized the need for economic analysis. It is stated in the Federal Wildland Fire Policy of 1995 that fire management alternatives will be based on science and sound ecological and economic principles. This article briefly examines key issues of the Federal Wildland Fire Policy from an economic perspective, and reviews the economic literature pertaining to prescribed burning. In particular, attention is paid to research regarding costs and benefits, efficiency, risk, and the wildland-urban interface. Recommendations for future economic research include focusing on defining a production function that relates economic and ecological outcomes with respect to prescribed fire; assessment of long-term cumulative effects; and finally, a comprehensive assessment of risk including decision making at the agency level. FOR. SCI. 46(3):332-334. Water and Nutrient Movement in Small, Forested Watersheds in the
Boston Mountains of Arkansas ABSTRACT. Four small (< 13.5 ha), upland, hardwood watersheds were selected for a study of the changes in water dynamics and associated chemical changes as water moves through various components of the ecosystem. These watersheds were also used to determine what changes in water movement and chemistry are related to silvicultural treatments of conversion to pine, a shelterwood cut or a clearcut applied 6 yr earlier. A fourth watershed served as a control. It was estimated that 29% of the rainfall left the watersheds. The ratio of Na+ and Cl- indicated a marine source of these elements. Enrichment from terrestrial sources was indicated for Mg+2, Ca+2, K+, and SO42-. The major changes in water movement and in water chemistry occurred between the surface of the litter layer and the bottom of the A horizon where 55% of the water and most of the nutrients that entered the watersheds were absorbed by a root network that develops at the litter A horizon interface. The degree of absorption varied from 30% for Na+ to 86% for H+. In general, nutrients that passed the A horizon also passed the E horizon and were transported out of the watersheds. SO42- was the major nutrient deposited (21.5 kg ha-1) and accumulated (15.6 kg ha-1) in the watershed followed by NO3- (9.8 and 8.2 kg ha-1) and Ca+2 (9.6 and 5.6 kg ha-1). Cl- behaved differently than other nutrients because it was stored in the canopy and surface soil layers but lost from deeper zones in the watershed. Mg+2 also differed in that it was the only nutrient to have a net loss from the watersheds. Magnesium, K+, H+, and NO3- had differences related to silvicultural treatments. Magnesium was leached from the canopy in the control and shelterwood. K+ was enriched in the throughfall of the control and possibly shelterwood. Hydrogen was absorbed in the control canopy and leached from the clearcut canopy. FOR. SCI. 46(3):335-343. Perceived Ecological Risks to Water Environments from Selected
Forest Industry Activities ABSTRACT. This article examines underlying factors shaping lay perceptions, and differences between lay and expert perceptions, of the ecological risks to water environments associated with six forest industry activities. A survey was administered to 183 lay subjects in four communities within the Lower Fraser Basin of western Canada. Parts of the survey were also administered to 16 aquatic science professionals. The results show that both lay and expert respondents generally perceive that clearcut logging and effluent from pulp mills pose a high degree of risk, while selective logging poses a lesser degree of risk. Both groups believe that fertilizer use poses a risk to water quality. However, the experts viewed the construction of logging roads as posing significantly more risk to water environments, and requiring greater regulation, than did the lay respondents. Conversely, the lay respondents viewed pesticide use as posing significantly more risk to water environments, and requiring greater regulation, than did the expert respondents. Discussion about the implications of these perceptions in terms of policy issues and communication efforts complete the article. FOR. SCI. 46(3):344-356. A Method of Estimating Direct and Indirect Effects of Armillaria
Root Disease and Other Small-Scale Forest Disturbances on Canopy Gap
Size ABSTRACT. The ecological and economic impacts of individual forest pathogens on forest stands are often difficult to measure because of indirect impacts arising from their interactions with other agents. Root diseases especially interact with many elements of the forest. This study uses a method called path analysis to estimate direct and indirect effects of Armillaria root disease and other small-scale disturbances on a pristine Pinus ponderosa stand in the Black Hills of South Dakota. Indirect effect was defined as an outcome where one small-scale disturbance alters the effect that another has on canopy gap size. Results indicate that key factors affecting gap size include Armillaria root disease, bark beetles, weak pathogens, ice/snow damage, lightning, and wildfires, presented in order of relative importance. Interactions occur between Armillaria and lightning, beetles, wind, and fire; between bark beetles and wind, fire, and weak pathogens; and between wind and fire. Armillaria and beetles both tend to occur where damage by wind is absent. Armillaria root disease was predicted to have the largest overall effect on gap size, which is mostly due to its direct effects, and not resulting from its interactions with other disturbances. Path analysis generates a predictive model based on covariation among disturbances and offers a way of quantifying the effects of these associations. FOR. SCI. 46(3):356-362. Predicting Future Forestland Area: A Comparison of Econometric
Approaches ABSTRACT. Predictions of future forestland area are an important component of forest policy analyses. In this article, we test the ability of econometric land use models to accurately forecast forest area. We construct a panel data set for Alabama consisting of county and time-series observation for the period 1964 to 1992. We estimate models using restricted data sets-namely, data from early periods-and use out-of-sample values of dependent and independent variables to construct precise tests of the model's forecasting accuracy. Three model specifications are examined: ordinary least squares, dummy variables (fixed effects), and error components (random effects). We find that the dummy variables model produces more accurate forecasts at the county and state level than the other model specifications. This result is related to the ability of the dummy variables model to more completely control for cross-sectional variation in the dependent variables. This suggests that the estimated model parameters better capture the temporal relationship between forest area and economic variables. FOR. SCI. 46(3):363-376. Linking Harvest Choices to Timber Supply ABSTRACT. Aggregate timber supply by ownership was investigated for a small region by applying stand-level harvest choice models to a representative sample of stands and then aggregating to regional totals using the area-frame of the forest survey. Timber harvest choices were estimated as probit models for three ownership categories in coastal plain southern pine stands of North Carolina using individual permanent and remeasured stand-level data from last two available USDA Forest Service Forest Inventory and Analysis (FIA) surveys. The timber harvest decision was modeled as a function of timber values, a cost factor, and stand volume as a proxy for nontimber values. Probit models were statistically significant at 1% for all ownerships. Area expansion factors (the portion of forest area in the region represented by the sampled stand) were then combined with harvest probabilities to model the aggregate effects of price changes on timber supply, given a fixed forest area. Implied price elasticities were estimated using this modeling of aggregate effects, and a bootstrapping procedure was applied to estimate confidence limits for supply elasticities with respect to price. Our results showed that NIPF and industry were elastically responsive in the aggregate when price increases are perceived as temporary but much less elastically and usually negatively responsive when increases are perceived as permanent. Results are consistent with theory of optimal rotations and highlight the critical influence of both existing inventory structure and expectations on aggregate timber supply. FOR. SCI. 46(3):377-389. Calibrating Predicted Diameter Distribution with Additional
Information ABSTRACT. The diameter distribution of the growing stock is an essential starting point in many forest management planning problems. There are several methods for predicting the diameter distribution of a stand, varying from methods which utilize theoretical distribution functions to nonparametric methods. Usually the predicted diameter distribution is scaled so that the stem number corresponds to the measured value. However, if stem number and basal area are both known, it may be difficult to predict a distribution that gives correct estimates for both these characteristics. Such diameter distributions can be obtained using an approach adopted from sampling theory-calibration estimation. In this study, the diameter distributions of Scots pine were predicted with two different methods, the Weibull and percentile based methods, and then calibrated with additional information. The calibration reduced the RMSE of stand variables computed from the predicted distribution. FOR. SCI. 46(3):390-396. Trigonometric Variable-Form Taper Equations for Australian
Eucalypts ABSTRACT. This article introduces a new variable-form taper model that is stable in specification yet flexible in its ability to fit data for species and trees with different stem forms. The base function is constructed from trigonometric volume-ratio equations following the geometry of a tree stem. The specification for the exponent includes variables for depicting changes in stem form along a stem and variables for taking into account differences in stem form among trees of different sizes. This model is fitted to data from 25 species of Australian eucalypts and is compared with Kozak's taper model to demonstrate its characteristics: stability in specification, flexibility in fitting data for species and trees with varying stem forms and accurate predictions of taper and merchantable height. FOR. SCI. 46(3):397-409. The Engines of Change in Resource-Dependent
Communities ABSTRACT. Social scientists have long attempted to understand change in natural resource-dependent communities. This article examines the relationship of three alternative "engines of change": local resource production, local historical events, and broad societal trends. Regression models were used to examine the relationships between four dimensions of community social change (size, structure, cohesion, and anomie) and the alternative "engines of change" in seven resource-dependent communities in the Pacific Northwest for over 50 year time periods. Included in the group were four timber towns, as well as communities dependent upon fishing, tourism, and mining. The data suggest that broad societal trends followed by local historical events explain the largest proportion of the variation in community social change dimensions of size and structure. Local resource production has modest explanatory power when combined with the other "engines of change." For. Sci. 46:410-422. Comparing Adjacency Constraint Formulations for Randomly Generated
Forest Planning Problems with Four Age-Class
Distributions ABSTRACT. Three types of adjacency constraint formulations-pairwise, Type I ND (nondominated), and NOAM (new ordinary adjacency matrix)-were compared on 900 hypothetical, randomly generated, spatially explicit forest management problems with between 50 and 350 stands. Forests were generated using four age-class distributions, nominally called immature, regulated, overmature, and old-growth. Management planning problems with adjacency constraints were formulated for these forests in Model 1 format based on a planning horizon consisting of three 20 yr periods. The problems also included flow constraints and minimum average age requirements for the ending forest. For all age-class distributions, the Type I ND constraint type resulted in significantly lower solution times than either the Pairwise or the NOAM constraint types. NOAM constraints performed better than Pairwise constraints for immature forest problems, but Pairwise constraints performed better than NOAM constraints for overmature and old-growth forest problems. There was no difference between these two constraint types for regulated forest problems. Results also show that the age-class distribution of the forest is one of the most important factors determining the time needed to solve forest management problems with adjacency constraints. In general, the more mature the forest, the harder the problem is to solve. In particular, problems based on the old-growth age-class distribution typically took much longer to solve than comparable problems based on the other age-class distributions. FOR. SCI. 46(3):423-436. Differential Effects of Rhizobacterial Strain and Dose on the
Ectomycorrhizal Colonization of Loblolly Pine Seedlings ABSTRACT. Loblolly pine seed were inoculated at sowing with one of four plant growth-promoting rhizobacteria (PGPR) strains at four different rates both in the nursery and in the greenhouse. Seedlings were harvested at 4, 8, and 12 wk after sowing in the greenhouse and at 5, 10, and 15 wk after sowing in the nursery. Ectomycorrhizae colonization, estimated as the total number ectomycorrhizal roots per seedling and averaging by gram root biomass, were not evident on any treatment at either 5 wk in the nursery or 4 wk in the greenhouse. However, by 8 wk after sowing, many treatments significantly (P < 0.0001) inhibited ectomycorrhizal root formation. Generally, increasing the rate of all bacteria applied in the greenhouse decreased ectomycorrhizal root formation. Conversely, strain LS212 at 1011 cfu resulted in an increase in ectomycorrhizal roots in the nursery. Increases in seedling root growth were also dependent on bacterial strain and rate, whereas shoot biomass was not effected. Decreases in ectomycorrhizae colonization accounted for 61% of the variation in increases in root biomass, suggesting high metabolic costs of mycorrhizal maintenance in the presence of some rhizobacteria. However, differences in shoot height and survival after outplanting could not be attributed to the mycorrhizae colonization effect. These studies demonstrate that mycorrhizae may serve as a carbon sink early in seedling development and indicate a complex interaction between soil microflora and bacterium in nursery and greenhouse settings. FOR. SCI. 46(3):437-441. A Timing-Oriented Approach to Spatial Allocation of Fire
Management Effort ABSTRACT. This article explores spatial optimization approaches to fire (and possibly fuel) management problems, with a timing-oriented model formulation. The relevant land area is divided into cells, and the ignition time of "protection areas" (such as towns, homes, and campgrounds) is delayed as much as possible through spatial application of treatments that have the effect of slowing the fire front movement through each cell. Model variables track the entry and exit times of the fire front and account for the earliest ignition source for each cell. A stylized case example is used to demonstrate the model's application and spatial sensitivity with easily interpretable results. The results show that a spatial concentration of fire management effort may not be optimal, at least for the simple example analyzed. Extension of the model formulation to long-term fuels management is also discussed. FOR. SCI.46(3):442-451. A Solution Method for Uneven-Aged Management Applied to Norway
Spruce ABSTRACT. The uneven-aged management problem is to determine the management regime for an existing stand over an infinite time horizon, without ever clearcutting it. A new solution method to solve this problem is presented and demonstrated on simulated Norway spruce stands with different initial stand structures. Diameter distributions were used as a convenient way to describe these structures. The method, which puts much effort into determining the timing of harvest activities, is based on Tabu search and greedy heuristics. The growth dynamics were described with a single tree simulator. Different problem approaches for this problem were adopted to maximize the net present value (NPV) of harvested trees, with or without steady-state constraints. With no such constraints, a finite time horizon approximates the general management problem, while the steady-state constraints involved fixed and equilibrium endpoints. The fixed endpoint was a reverse J-shaped diameter distribution, and its purpose was to mimic the structure of a virgin stand. Analysis of economic efficiency, productivity. and managerial implications were made. With the method used and for the endpoint problems, the conversion strategy, conversion length. and steady-state diameter distribution were determined simultaneously. The Kolmogorov-Smirnov measure was used to describe the similarity between diameter distributions and was put directly into the constraints. The infinite approximation is suggested as the best problem formulation as it, in contrast to a steady-state approach, does not assume that a resource system reaches a climax, eliminates the need to define a diameter class width, and involves no fixed cutting cycles. The even-aged management problem, which is to determine the best period for clearcutting and the best thinning regime that precedes the clearcut, while recognizing the soil expectation value, was analyzed for comparison. The method is flexible, independent of the kind of growth simulator used, and can, for example, be directly applied to a diameter class model. FOR. SCI. 46(3):452-463.
Forest Science, Volume 46, Number 2, May 2000 Special Section Introduction to Spatial Modeling in Forest Management and Resources Planning A. Murray Understanding the Tradeoffs Between Site Quality and Species Presence in Reserve Site Selection R. Church, R. Gerrard, A. Hollander, and D. Stoms ABSTRACT. A number of optimization models have been developed for natural reserve design and reserve site selection. The most common approach seeks to maximize the number of individual species that occur among chosen sites. A number of heuristics and mathematical programming algorithms have been applied to solve this problem. Although attaining maximum overall species representation is important, the relative quality of representation [which could be affected by site attributes such as habitat value, adequate population size, presence of critical resources, existence (or lack thereof) of exotic competitors, etc.] has been absent from most representation models. Yet issues of site quality should be considered in order to have any assurance of long-term species persistence in a reserve system. Here we present a multiobjective optimization model that addresses the issue of balancing species presence with habitat quality. One type of interesting alternative yields more high quality representation at the price of some reduction in overall representation. We present an application using a large dataset from California Gap Analysis to demonstrate this and other tradeoffs. Optimal solutions are attained using commercial integer programming software with very reasonable computational effort. For. Sci. 46(2):157-167. Optimizing Forest Stand Management with Natural Regeneration and Single-Tree Choice Variables J. Hof and M. Bevers ABSTRACT. This article addresses the any-aged forest management problem with individual trees as the choice variables in integer programming models. In order to sustain the forest using natural regeneration, spatial proximity of seed trees is required for harvesting to take place in these models. This problem requires integer variables to avoid harvesting part of a tree, but it is remarkably integer-friendly. Solvability of large models is thus explored, along with the patterns of solution that can be recognized in smaller models. Results from these exploratory models are sensitive to initial forest conditions and do not display the steady state conditions typically assumed for uneven-aged management in the literature. For. Sci. 46(2):168—175. Impacts of the Time Horizon for Adjacency Constraints in Harvest Scheduling H.M. Hoganson and J.G. Borges ABSTRACT. Adjacency constraints, constraints which limit the harvest timings of adjacent management units, are a challenge to address within forest management scheduling models. Four large test cases were examined to consider the need to recognize site-specific adjacency constraints over a long time horizon within a forest management scheduling model. Results suggest that the costs of adjacency constraints tend to be short-term in nature. Immediate periods tend to be influenced most because there is less lead time to prepare for the constraints. Little may be gained in planning by addressing adjacency constraints for more than a full rotation length. Adjacency constraints can likely be satisfied efficiently without having large shifts in harvest timings for most all management units. Results are consistent with an interpretation of the dual formulation of a relaxed linear programming formulation of the problem. For. Sci. 46(2):176—187. A Model and Tabu Search Method to Optimize Stand Harvest and Road Construction Schedules E.W. Richards and E.A. Gunn ABSTRACT. An important function of tactical planning in forest management is to choose spatially and temporally explicit schedules for both harvesting and road construction activities. In addition to maintaining consistency with goals of the strategic planning process, harvesting decisions are subjected to spatial, environmental constraints. At the same time, planning and cost of road access over the medium-term planning horizon must be considered. This article presents a model and heuristic solution methodology to address stand level harvest scheduling and the associated road construction scheduling problem. The model is formulated to determine minimal cost schedules, for stand harvests and road construction, that achieve recommended timber harvest volume targets and that comply with environmental regulations. The harvest decisions are made at the stand level of resolution. Graph structures are used to formulate the spatial restrictions on clearcut opening size and location. Road construction projects are scheduled to create a feasible road network at minimum net present capital cost. The optimization problem is solved using a Tabu search heuristic, which includes special constructs to cope with the complexity of this problem. An efficient frontier of solutions is produced, which may be utilized to analyze tradeoffs between lost forest productivity, due to timing of harvests, and the capital cost of road construction. Forest Science 46(2):188—203. A Three-Stage Heuristic for Harvest Scheduling with Access Road Network Development M.M. Clark, R.D. Meller, and T.P. McDonald ABSTRACT. In this article we present a new model for the scheduling of forest harvesting with spatial and temporal constraints. Our approach is unique in that we incorporate access road network development into the harvest scheduling selection process. Due to the difficulty of solving the problem optimally, we develop a heuristic that consists of a solution construction stage and two solution improvement stages. We call our approach INROADS and compare it to three other approaches by employing hypothetical example problems with 225 stands (or cut blocks) over a three-period planning horizon. Thirteen example forests that vary in terms of stand value and spatial dispersion are used to evaluate our heuristic, which outperforms the other approaches tested. For. Sci: 46(2):204—218. Articles Neutrality of Forestry Income Taxation and Inheritable Tax Exemptions for Timber Capital J. Uusivuori ABSTRACT. This article examines the neutrality of income taxation in the so-called Austrian sector of the economy. By focusing on the forestry sector, it is shown that certain exemption practices of yield taxation can be modified to restore the efficiency of the taxation. Earlier research on the production efficiency relating to different capital income tax systems in the Austrian sector shows that yield taxes based on realized income lead to inefficient allocation of resources between the Austrian and the ordinary sector of the economy when pretax distortions are present. The models used in the earlier tax literature do not, however, differentiate between taxing capital income and taxing the initial capital under an individual occupancy of an asset. In this article, by explicitly separating timber capital taxation from timber capital income taxation, a modified yield taxation scheme is presented, which gradually corrects an initially distorted allocation of resources between forests and other assets in the economy. FOR. SCI. 46(2):219—228. Modeling Tree-Ring Growth Responses to Climatic Variables Using Artificial Neural Networks Q-B Zhang, R.J. Hebda, Q-J Zhang, and R.I. Alfaro ABSTRACT. Modeling the nonlinear and complex relationships between climate and tree-ring growth is of significance in dendroclimatic studies, but difficult to implement using traditional linear regression approaches. To overcome this difficulty, the technique of Artificial Neural Network (ANN) was employed in this study to develop the growth response models using the climate/growth database for Douglas-fir (Pseudotsuga menziesii var. menziesii [Mirb.] Franco) on southern Vancouver Island, Canada. The results show that the ANN models are able to extract nonlinear growth response patterns from the observed climate/tree-ring datasets, and to generate more accurate predictions than multiple linear regression approaches. The ANN-extracted climate-growth relationships can be displayed by scenario analysis; for example, when all other input variables are held fixed at their means, the limiting effect of April-July precipitation on tree growth decreases with increased precipitation. The main difficulty of applying ANN technique in dendroclimatology is the problem of overlearning (i.e., the ANN learns too many specific climate-growth patterns and loses the ability to generalize between similar climate-growth patterns). This problem can be alleviated by carefully designing the ANN, such as reducing the number of input variables, choosing a variety of training/testing sets, designing partially connected architectures with a small number of neurons in the hidden layer, and using early stopping during training process. The reliability of the derived ANN models is assessed by validation on independent testing datasets. The main advantages of the ANN technique over traditional dendroclimatic approaches are its ability to capture nonlinear climate-growth response, and its nonreliance on preassumed functional relationships for describing the observed datasets. The ANN method introduced in this article is sufficiently general to be applicable to many forest ecological modeling applications. FOR. SCI. 46(2):229—239. Validation of a Forest Values Typology for Use in National Forest Planning G. Brown and P. Reed ABSTRACT. Public values for national forestlands are assumed to underlie preferences for actual forest use and define the context for forest planning and decision making, but the relationship between preferences and attitudes toward forest management activities and public forest values (both use and nonuse values) is not well understood. Using data from a survey of Alaskan residents in the Chugach National Forest plan revision process, the relationship between attitudes toward forest management actions and forest values is examined using a variety of statistical procedures. Key findings indicate that: (1) survey respondents were able to identify with 13 distinct forest values based on a modified forest value typology developed by Rolston and Coufal (1991), (2) no obvious latent structure of variables or constructs emerged from factor analysis of the 13 forest values indicating that the forest value typology may not be easily simplified without compromising the exclusiveness of measured forest values, (3) small, but statistically significant correlations were found between attitudes toward specific forest management practices such as logging and mining and held forest values, and (4) forest values are modestly predictive of respondent preferences for specific forest planning decisions. For. Sci. 46(2):240—247. Asymmetric Day/Night Temperature Elevation: Growth Implications
for J.V.H. Constable and W.A. Retzlaff ABSTRACT. Using the TREGRO simulation model we examined the relative impact of asymmetric and symmetric elevations of day/night temperatures on 3 yr biomass gain of yellow-poplar (Liriodendron tulipifera L.) and loblolly pine (Pinus taeda L.). Temperature elevation scenarios used were: (1) an asymmetric 0.3°C/0.9°C increase in day/night temperature (T + 0.3/0.9) as observed since the turn of the century; (2) a symmetric 4°C elevation during both day and night periods (T + 4) as predicted by general circulation models; and (3) an asymmetric 2°C/6°C elevation of day/night temperature (T + 2/6). TREGRO incorporates temperature effects on photosynthesis, respiration, growth rate, and phenology. In both species for all temperature elevation scenarios, respiratory increases exceeded photosynthetic increases and reduced belowground growth. In yellow-poplar, belowground growth was reduced by 7.6% in the T + 0.3/0.9 scenario, whereas the T + 4 and T + 2/6 scenarios reduced belowground growth by 145% and 155%, respectively. The elevated temperature scenarios increased total tree biomass of loblolly pine, but belowground growth was reduced by 24%, 111%, and 113% by the T + 0.3/0.9, T + 4, and T + 2/6 scenarios, respectively. Reductions in root biomass at elevated temperatures may influence competitive interactions between forest tree species and susceptibility to environmental fluctuations. FOR. SCI. 46(2):248—257. Tree-Growth and Understory Responses to Low-Severity Prescribed
Burning in M.D. Busse, S.A. Simon, and G.M. Riegel ABSTRACT. The growth of ponderosa pine and associated understory vegetation was evaluated for a 6 yr period following spring underburning of surface fuels. Underburn and control (unburned) plots were paired at 15 replicate sites in pole-sized ponderosa pine forests of central Oregon. The burns were generally low in severity, as noted by low O horizon mass reduction (24%) and tree mortality (6%). A small but significant decline in basal area and volume growth rates of surviving trees was found in the 6 yr following underburning. The reduction in tree growth was related to a combination of crown length reduction, O horizon reduction, and site productivity. More productive stands had the highest proportional reduction in growth due to burning. By comparison, site conditions including stand density, initial basal area, elevation, parent material, and soil fertility were not related to the observed growth reduction. Understory vegetation showed a mixed response to burning. Shrub cover, dominated by Purshia tridentata, declined significantly following burning and remained well below preburn levels for the length of the study, even though one-fourth of all burned Purshia plants successfully resprouted. Total herbaceous vegetation cover and production were unaffected by burning, while species diversity increased slightly. With the exception of the decline in Purshia cover, the results indicate that low-severity prescribed burning has a relatively minor impact on tree-growth and understory response in thinned ponderosa pine stands. FOR. SCI. 46(2):258—268. Effects of Correlation among Parameters on Prediction Quality of a Process-Based Forest Growth Model B.T. Guan ABSTRACT. A nonparametric method was introduced as a technique for evaluating the effects of parameter correlation on prediction quality of process-based forest growth models. The method was based on a rank correlation and Cholesky decomposition. For a given data matrix, by reordering the observations, the method would produce a rearranged matrix with the desired correlation structure. The method was computationally simple and efficient. Using a process-based model calibrated for red pine (Pinus resinosa Ait.) as an example, small-scale Monte Carlo simulations revealed that parameter correlation had different effects on the model's prediction means and variances, depending on the importance of the parameters involved. In general, given the same level of correlation, correlation between two important parameters would have greater influences on prediction quality than correlation between two less important parameters. Parameter correlation slightly affected the prediction means but could significantly change prediction variances. The relationship between prediction quality and the degrees of correlation, however, was not necessarily a linear one. The same parameter correlation might also have different effects on different state variables. For. Sci. 46(2):269—276. Using Numerical Optimization for Specifying Individual-Tree Competition Models J. Miina and T. Pukkala ABSTRACT. In this article we present a method that combines maximum likelihood estimation and nonlinear programming in growth modeling. The method of Hooke and Jeeves is used to discover the optimal specification of a particular competition index type, while statistical software is used to fit the regression model with the given competition index type. The log-likelihood computed by the statistical software is fed back to the optimization algorithm, which alters the specification of the competition index type based on the changes in the log-likelihood. This approach was tested for a mixture of Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies [L.] Karst.). The characteristics of five different competition index types were optimized. The best model included an index computed from vertical angles formed by a horizontal plane and the tops of competitors. The elevation of the horizontal plane was computed with a species-specific linear regression model using height of the subject tree as the predictor. Pine competitors nearer than 6 m and spruce competitors nearer than 9-10 m were included in the optimal competition index. This study showed that the approach used here is highly efficient. FOR. SCI. 46(2):277—283. A Theory of Red Pine (Pinus koreanis) Management for Both Timber and Commercial Seeds C-Z Li and K-G Löfgren ABSTRACT. Red pine (Pinus koraiensis), is a commonly distributed species of tree in northeastern China. The wood is used for manufacturing purposes as usual, and the seeds are used as a source of delicious food and for medical applications. If the top of the tree is removed at a mature age, seed production is much enhanced. In this article, we derive optimal harvesting rules for such multiple use management of red pine trees. We give optimality conditions for cutting off the top of the tree, the intensity of removal, and the optimal date for the final felling. The two harvesting dates will indirectly determine the optimal length of commercial seed production. We also derive comparative static results on how the rotation periods and the intensity of removal changes, as a function of prices and the interest rate. The theory is also applicable to the economic management of seed orchards, where the practice of cutting off the top of the tree is used, all over the world, to induce seed production. FOR. SCI. 46(2):284—290. Analytical Site Index Solution for the Generalized Log-Logistic Height Equation C.J. Cieszewski ABSTRACT. The generalized log-logistic height equation computes height as a function of age and a fixed base-age site index. This equation and its modifications have been used for many applications in various regions. It is seemingly apparent that this equation is analytically insolvable for the site index; no general analytical solution to this equation is readily available. This article presents such a solution that has proven to be valid and useful with all tested parameters. This solution is based on an adaptation of the Ramanujan's (1887-1920) solution for a trinomial with real-number exponents. Ramanujan's solution is a series that in many cases can be expressed as a closed-form equation. In the present context, this series may be used for derivations of various special cases of closed-form solutions, initial-condition difference and differential equations, and for various analytical sensitivity and trend analysis, as well as for efficient site index computations. FOR. SCI. 46(2):291—296 Predicting Daily Mean Soil Temperature from Daily Mean Air Temperature in Four Northern Hardwood Forest Stands S.E. Brown, K.S. Pregitzer, D.D. Reed, and A.J. Burton ABSTRACT. Soil temperature is very important in regulating ecosystem processes, yet it is often difficult and costly to measure. Most models that have endeavored to predict soil temperature have either a long time step or several complicated independent variables. Daily mean air and soil temperatures were measured from 1989-1997 in four northern hardwood sites along a 500 km latitudinal gradient in Michigan. These data were used to derive a simple method to predict daily mean soil temperature (depth of 15 cm) using the daily mean air temperature from the previous day and a cosine function of Julian date (R2 = 0.93-0.96; SEM = 0.98-1.40°C). Predicted values were compared with actual recorded soil temperatures from 1997 at each of the sites, and the average difference between the observed and predicted values ranged from 0.11 to 0.39°C. Different coefficients were estimated for each of the sites; however, this general method of predicting soil temperature appears applicable to any site. Once calibrated for a given site, soil temperature may be simply estimated, thus reducing the need for extended monitoring efforts. This method also allows the reconstruction of soil temperature records beyond the monitoring period. Projecting long-term trends in soil temperature may help to further elucidate several ecosystem processes and also may provide more information on how a changing global climate will impact forest ecosystems. FOR. SCI. 46(2):297—301. Fostering the Production of Nontimber Services Among Forest Owners with Heterogeneous Objectives J.D. Kline, R.J. Alig, and R.L. Johnson ABSTRACT. Programs to enhance nontimber services increasingly focus on nonindustrial private forest (NIPF) owners. These owners are believed to possess multiple objectives, causing them to respond to economic forces and policies in complex and unpredictable ways. We examine NIPF owners in western Oregon and western Washington, using a survey to document their forest ownership objectives and willingness to accept incentive payments to forego harvesting to improve wildlife habitat. An empirical model is developed describing owners' willingness to accept incentive payments to delay harvest, as a function of their forest ownership objectives and socioeconomic characteristics. Mean incentive payments necessary to induce owners to forego harvest are higher for owners possessing primarily timber objectives ($301-314/ha/yr), than for owners possessing both timber and nontimber objectives ($254-257/ ha/yr) or primarily recreation objectives ($185-210/ ha/yr). An estimated supply curve describing the area of NIPF land on which owners would forego harvesting for 10 yr varies from relatively flat to fairly steep. Although many owners would require little or no incentive to forego harvest, others would require a significant incentive. Nontimber services likely could be enhanced by targeting incentive programs or technical assistance toward NIPF owners possessing nontimber objectives. FOR. SCI. 46(2):302—311. Book Reviews Forest Plants of the Southeast and Their Wildlife Uses edited by J.H. Miller and K.V. Miller Forest Health and Protection edited by R.L. Edmonds, J.K. Agee, and R.I. Gara
Forest Science, Volume 46, Number 1, February 2000 Compatible Volume-Taper Models for Loblolly and Slash Pine Based on a System with Segmented-Stem Form Factors Z. Fang , B.E. Borders , and R.L. Bailey ABSTRACT. By integrating a variable-form differential equation for taper, a segmented-stem system of models involving a taper equation, merchantable volume equation, and total stem volume equation results. Through the constraints imposed on the coefficients of integration, the taper model is continuous at the inflection points, and all components in the system are compatible with each other. Models are derived for a bole with two inflection points, but the constant form factor model (no inflection point) and one inflection point segmented model can be obtained as special cases by substituting appropriate parameters directly into this more general model. All parameters are shared by the components in this compatible system. Simultaneous parameter estimation techniques are used so that all appropriate information is obtained from the data. Based on stem analysis data for 1,280 loblolly pine (Pinus taeda L.) trees and 871 slash pine (Pinus elliottii Engelm.) trees, improved predictions result with respect to predicting a stem profile when compared to a constant form factor model. For. Sci. 46(1):1-12. Dynamics of Coarse Woody Debris Placed in Three Oregon Streams R.F. Keim, A.E. Skaugset, and D.S. Bateman ABSTRACT. Many streams of the North American west coast are deficient in coarse woody debris (CWD) and have been subjected to aquatic habitat restoration by adding CWD. The ready availability of alder (Alnus rubra Bong.) CWD makes it attractive for such uses, but the dynamics of this relatively small debris are poorly understood. We placed CWD in three third-order streams in western Oregon either as large, key pieces (pulled-over streamside alders or bucked conifer logs) or as smaller logging debris (mostly alder). This treatment immediately increased CWD in the streams by 86% to 155%. We used chronosequences of surveys to evaluate whether the increased loadings of CWD persisted for more than a year, and whether the key pieces trapped smaller debris to create accumulations. Although there was more CWD in all three streams during the 3 yr after treatment than there had been before treatment, rates of movement were high. Aggregation of CWD increased in all three streams for at least 1 yr, and accumulations of CWD associated with key pieces were larger after 3 yr than immediately after treatment. Pulled-over alders were more stable and more effective in forming accumulations than bucked conifers but were subject to rapid decay. For. Sci. 46(1): 13-22. Optimal Harvesting and Thinning with Stochastic Prices R.J. Brazee and E. Bulte ABSTRACT. This article rigorously incorporates optimal thinning decisions for an even-age stand into an optimal harvesting model with fluctuating stumpage prices. The theoretical model optimally determines how often and at what ages to thin when stumpage prices are independently drawn from a stationary distribution. New theoretical results include increases in the net present value of both land and stumpage, and an increase in some harvest reservation prices from introducing thinning. A simplified model is numerically simulated using parameters estimated from Dutch data for Pinus sylvestris to determine when to thin. The simulation results suggest that the gains from incorporating thinning are significant when compared to the Faustmann approach and at least modestly important when compared to optimal harvesting models without thinning. The simulation results also indicate that expected thinning age may decrease significantly while the expected harvest age increases, when compared to the Faustmann approach. For. Sci. 46(1): 23-31. Valuing a Forest as a Call Option: The Sale of Forestry Corporation of New Zealand W.R. Hughes ABSTRACT. In September 1996, the New Zealand (NZ) Government sold its 100% shareholding in the Forestry Corporation of NZ (FC) to a consortium led by Fletcher Challenge Forests (FF), a publicly listed company, for NZ $2.06 billion. Option pricing methodology is used to value the forest assets that were listed in FC's 1996 Annual Report at $1.853 billion. Total net assets had a book value of $2.03 billion, about $30 million less than the selling price. Assuming a 7.5% real cost of capital and a maximum tax rate of 33%, the actual value of the forest assets realized in the sale (taken to be $1.853 billion) are at a 12.9% discount to the "fair" value of $2.128 billion derived by the option pricing approach. The advantage of this approach to forest valuation over the traditional approach (based on discounted cash flow using projected future prices over long horizons) is that only the volatility of future log prices need be estimated. The relative insensitivity of forest value to this parameter suggests less spread between bid and ask prices by forest buyers and sellers with similar costs of capital, tax rates, and so on. FOR. SCI. 46(1):32-39. The Impacts of Deregulation and Privatization on Cost Efficiency in New Zealand's Forest Industry D.L. Grebner and G.S. Amacher
ABSTRACT. In this paper, we investigate whether deregulation and privatization induced changes in cost efficiency within the New Zealand wood industry. Unlike previous work, the effects of privatization, deregulation, and removal of log export bans are compared to determine which shock had the most influence on efficiency changes. Cost efficiency is measured by estimating stochastic frontier models using the recent cost function approach, which does not suffer from the endogeneity problems associated with stochastic frontier production function estimation. The results show that cost efficiency decreased after each policy reform, but deregulation was more important in this regard than privatization. This suggests that countries with comparative advantages in wood processing, who also implement deregulation or privatization, may suffer through a short-run period of lower efficiency as the economy adjusts to higher input costs in those sectors. In New Zealand's case, the adjustments most likely affecting efficiency have been investments in new technologies, where time is required to attain maximum efficiency. The results are contrary to other studies that have predicted increased efficiency as a result of privatization. FOR. SCI. 46(1):40-51. Effects of an Intense Wildfire in a Mexican Oak-Pine Forest P.Z. Fulé, A.G-A., and W.W. Covington ABSTRACT. An oak-pine forest burned by intense wildfire in April, 1996, and a companion unburned area were sampled 1 month and 1 yr postfire in La Michilía Biosphere Reserve, Durango, Mexico. Up to 90% of the trees were killed or top-killed in the burned area, but larger trees tended to survive, so basal area was only reduced by 66%. Top-killing was relatively higher among fire-susceptible oaks and lower among fire-resistant pines. However, oaks were strong resprouters both in the canopy and at the base of top-killed trees. Damage codes based on crown scorch and bole char were highly accurate when predicting that a tree would die but substantially overestimated survivors. Most tree regeneration was top-killed in the fire, but oak sprout density was 700% that of the unburned area by 1 yr postfire. Manzanita shrubs also resprouted vigorously. Herbaceous production and cover were lower after the first postfire growing season in the burned area than the unburned area. Woody fuels and forest floor depth were also reduced. Although short-term fire effects indicate that the forest ecosystem has moved closer toward a savanna condition, remnant seed trees and sprouting trees are expected to maintain forest cover. Future herbaceous production is likely to increase in response to overstory mortality. Quantification of fire effects is helpful for supporting short-term management decisions since oak-pine forests cover millions of hectares in northern Mexico. As a long-term management strategy, however, we suggest that restoring the frequent, low-intensity fire regime may be desirable for ecological and economic reasons. FOR. SCI. 46(1):52-61. Analytical Group Decision Making in Natural Resources: Methodology and Application D.L. Schmoldt and D.L. Peterson ABSTRACT. Group decision making is becoming increasingly important in natural resource management and associated scientific applications, because multiple values are treated coincidentally in time and space, multiple resource specialists are needed, and multiple stakeholders must be included in the decision process. Decades of social science research on decision making in groups have provided insights into the impediments to effective group processes and on techniques that can be applied in a group context. Nevertheless, little integration and few applications of these results have occurred in resource management decision processes, where formal groups are integral, either directly or indirectly. A group decision-making methodology is introduced as an effective approach for temporary, formal groups (e.g., workshops). It combines the following three components: (1) brainstorming to generate ideas; (2) the analytic hierarchy process to produce judgments, manage conflict, enable consensus, and plan for implementation; and (3) a discussion template (straw document). Resulting numerical assessments of alternative decision priorities can be analyzed statistically to indicate where group member agreement occurs and where priority values are significantly different. An application of this group process to fire research program development in a workshop setting indicates that the process helps focus group deliberations; mitigates groupthink, nondecision, and social loafing pitfalls; encourages individual interaction; identifies irrational judgments; and provides a large amount of useful quantitative information about group preferences. This approach can help facilitate scientific assessments and other decision-making processes in resource management. For. Sci. 46(1):62-75. A Timber Extraction Method Based On Pavement Serviceability and Forest Inventory Data A. Martin, P. Owende, S. Ward, and M. O'Mahony ABSTRACT. A methodology for integrating pavement classification and forest inventory data to determine the capability of forest access roads with weak subgrades to support timber extraction is described. GPS location data recorded in stand-alone mode was superimposed on forest and Ordnance Survey maps. Within a GIS, the acquired spatial data was manipulated and integrated with pavement attribute information and the current and projected forest inventory data. Potential pavement damage by a typical timber haulage truck with payloads of 22, 27, 30, and 35 tonnes (t) was then assessed. It was found that by overloading the truck by 3 and 8 t (GVW of 43 t and 48 t, respectively), the total volume of timber that could be conveyed without damaging the serviceable pavements reduced by an average of 16 and 44%, respectively. Rerouting of timber to avoid critical and failed sections could significantly increase the transportation costs. Rerouting was found to be impractical where forest compartments were accessible by single routes; hence, necessary repairs to facilitate the extraction are recommended in such cases. The final database could be extended to include specific costing of repair and maintenance requirements, and so determine the economic implications of respective routing strategies. FOR. SCI. 46(1):76-85. Influence of Vertical Foliage Structure on the Distribution of Stem Cross-Sectional Area Increment in Western Hemlock and Balsam Fir J.A. Kershaw, Jr., and D.A. Maguire ABSTRACT. A set of western hemlock (Tsuga heterophylla Raf. [Sarg.]) and balsam fir (Abies balsamea [L.] Mill.) from western Washington, USA and western Newfoundland, Canada, respectively, were destructively sampled to examine relationships between vertical foliage structure and distribution of stem cross-sectional area increment. A series of stem growth distribution models describing the relationship between amount of foliage area above a given height and stem cross-sectional area increment at that height was derived from the pipe model theory. These models were derived with increasing generality so that two commonly held assumptions could be explicitly tested: (1) linear increase in cross-sectional area increment with increasing foliage area; and (2) constant cross-sectional area increment below base of the live crown. Overall, the models performed very well, accounting for over 80% of the observed variation in cross-sectional area increment for both species. The results show that, while cross-sectional area increment increases with increasing current foliage, the increase is not proportional (i.e., linear). Furthermore, the rate of cross-sectional area increment below base of the live crown was found to increase in the smaller balsam fir trees and decrease in the larger western hemlock trees. These results suggest that cross-sectional area increment per unit foliage below the live crown may change as trees grow. FOR. SCI. 46(1):86-94. Logistic Regression for Southern Pine Beetle Outbreaks with Spatial and Temporal Autocorrelation M.L. Gumpertz, C. Wu, and J.M. Pye ABSTRACT. Regional outbreaks of southern pine beetle (Dendroctonus frontalis Zimm.) show marked spatial and temporal patterns. While these patterns are of interest in themselves, we focus on statistical methods for estimating the effects of underlying environmental factors in the presence of spatial and temporal autocorrelation. The most comprehensive available information on outbreaks consists of binary data, specifically, annual presence or absence of outbreak for individual counties within the southern United States. We demonstrate a method for modeling spatially correlated proportions, such as the proportion of years that a county experiences outbreak, based on annual outbreak presence or absence data for counties in three states (NC, SC, and GA) over 31 yr. In this method, the proportion of years in outbreak is predicted using a marginal logistic regression model with spatial autocorrelation among counties, with adjustment of variance terms to account for temporal autocorrelation. This type of model describes the probability of outbreak as a function of explanatory variables such as host availability, physiography, climate, hurricane incidence, and management type. Explicitly including spatial autocorrelation in the model improves estimates of the probability of outbreak for a particular county and of the importance of the various explanatory variables. FOR. SCI. 46(1):95-107. Guided Transect Sampling for Assessing Sparse Populations G. Ståhl, A. Ringvall, and T. LämåsABSTRACT. Guided Transect Sampling is suggested for transect based surveys when sampling sparse and geographically scattered populations. It is a two-stage design in which wide strips are selected in the first stage followed by a subsampling procedure guided by prior information in the second stage. As a basis for the second stage, the target area is divided into grid-cells containing covariate data obtained, for example, by remote sensing. The general principle can be coupled with different transect based survey methods such as strip sampling or line transect sampling. Also, different strategies for the second stage guidance can be used, resulting in estimators with different properties. In this study, Guided Transect Sampling was compared with a traditional strip survey under different simulated forest conditions. The comparisons indicated that the proposed method can improve the efficiency of transect based inventories of sparse populations. For. Sci. 46(1):108-115. Generalized Algebraic Difference Approach: Theory Based Derivation of Dynamic Site Equations with Polymorphism and Variable Asymptotes C.J. Cieszewski and R.L. Bailey ABSTRACT. Biologically realistic site models require the ability to concurrently express variable asymptotes and polymorphism in curve shapes. Moreover, it is only logical and rational to require that these models be invariant to changes in the index or base age. This manuscript explains the Generalized Algebraic Difference Approach that can be used effectively to derive truly base-age invariant difference equations capable of describing concurrent polymorphism and variable asymptotes. This new generic methodology for derivation of even the most complex dynamic equations is mathematically sound. The equations derived with it can be extremely flexible and may generate intricate patterns of concurrent polymorphism and variable asymptotes. This methodology is relevant to all situations in which the dependent variable is a function of an unobservable variable, and the models can be implicitly defined by their initial conditions. It is equally useful for derivation of new equations and for improvement of existing base-age specific equations. FOR. SCI. 46(1):116-126. Prediction of Annual Diameter Growth and Survival for Individual Trees from Periodic Measurements Q.V. Cao ABSTRACT. It is difficult to fit annual tree survival and diameter growth models to data that were measured, not every year, but at some interval. This study aimed to determine suitable methods to obtain parameter estimates for such a system from periodic measurements. Given a system consisting of a tree survival model and a tree diameter growth model, this article presents an iterative method for estimating system parameters. The method involves sequentially updating of the parameters of both models within the growth period. Data from 111 plots from the Southwide Seed Source Study of loblolly pine (Pinus taeda L.) were then used to evaluate this iterative approach against the averaging method that assumes a constant tree survival probability and diameter growth rate during the remeasurement interval. Results indicated that the iterative method out-performed the averaging method in predicting future individual tree survival, diameter growth, and stand basal area. The iterative method was superior because it accounted for the variable rate of diameter growth and tree survival probability as functions of ever-changing stand and tree attributes. FOR. SCI. 46(1):127-131. Duality and Faustmann: Implications for the Evaluation of Landowner Behavior R.J. Brazee and G.S. Amacher ABSTRACT. This paper examines the behavioral consequences when landowners seek to minimize costs rather than maximize profits. We derive a cost function that is dual to the net present value function in the Faustmann Model. This cost function provides a theoretical foundation for studies that estimate forest production costs. We use comparative statics methodology to derive qualitative results for changes in selected policies and exogenous parameters. We find that the qualitative impacts under cost minimization are usually unambiguous. Qualitative impacts under profit maximization are usually ambiguous. This implies that behavioral impacts are usually easier to assess a priori, when landowners minimize costs rather than maximize profits. FOR. SCI. 46(1):132-138. Relative Abundance and Species Richness of Herpetofauna in Forest Stands in Pennsylvania B. Ross, T. Fredericksen, E. Ross, W. Hoffman, M.L. Morrison, J. Beyea, M.B. Lester, B.N. Johnson, and N.J. Fredericksen ABSTRACT. The relative abundance and species richness of herpetofauna was investigated to assess the impact of recent logging operations in 47 forest stands in northeastern Pennsylvania during 1996 and 1997. Stands including nonindustrial private forestlands and public lands that have received some type of harvesting within the last 8 yr ranged from near complete overstory tree cover to complete removal of overstory cover. Stands included the two dominant forest types in the region: northern hardwood (Betula, Fagus, Prunus, Acer, and Tsuga spp.) and oak-hickory (Quercus and Carya spp.). A total of 8,181 individuals of 26 species (12 salamander, 7 snake, 6 frog, and 1 toad species) were observed in the study stands. The relative abundance and species richness of salamanders increased significantly with increasing retention of tree basal area. Forest stands containing > 15 m2/ha live tree basal area appeared to be a threshold level for high salamander abundance. Snake species abundance and richness increased significantly with increasing removal of tree basal area. The abundance of anuran species showed no significant relationship with amount of tree basal area removal, but the relative abundance and species richness of anurans depended on the presence of water within or bordering the stands. Forest type did not change the overall response of herpetofauna community composition to forest harvesting, although salamanders were more abundant in northern hardwood stands, and snakes were more abundant in oak-hickory stands. Patterns and threshold levels of abundance and species richness of herpetofauna determined in this study may be used to maintain the abundance and richness of selected species when harvesting forest stands. FOR. SCI. 46(1):139-146.
Forest Science, Volume 45, Number 2, May 1999
Estimating Economic Gains for Landowners Due to Time-Dependent Changes in Biotechnology J.E. Wagner and T.P. Holmes ABSTRACT. 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. Afforestation as a Real Option: Some Policy Implications B.J. Thorsen ABSTRACT. 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. Composite and Calibration Estimation Following 3P Sampling T.G. Gregoire and H.T. Valentine ABSTRACT. 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. Realized Gain and Prediction of Yield with Genetically Improved Pinus radiata in New Zealand S.D. Carson, O. Garcia, and J.D. Hayes ABSTRACT. 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 pre-existing 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. Combining a Decomposition Strategy with Dynamic Programming to Solve Spatially Constrained Forest Management Scheduling Problems J.G. Borges, H.M. Hoganson, and D.W. Rose ABSTRACT. 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. Selecting Loblolly Pine Parents for Seed Orchards to Minimize the Cost of Producing Pulp W.J. Lowe, T.D. Byram, and F.E. Bridgwater ABSTRACT. 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. An Adjustable Predictor of Crown Profile for Stand-Grown Douglas-Fir Trees D.W. Hann ABSTRACT. 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. Projecting Timber Inventory at the Product Level L. Teeter and X. Zhou ABSTRACT. 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. Forecasting Adoption and Substitution of Successive Generations of Structural Wood Panel Products in the United States S.R. Shook ABSTRACT. 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. Spatially Optimizing Wildlife Habitat Edge Effects in Forest Management Linear and Mixed-Integer Programs M. Bevers and J. Hof ABSTRACT. 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. Optimal Public Harvesting Under the Interdependence of Public and Private Forests E. Koskela and M. Ollikainen ABSTRACT. 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. Silvicultural Contracting in British Columbia: A Transaction Cost Economics Analysis S. Wang and G.C. van Kooten ABSTRACT. 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. Effect of Western Spruce Budworm Defoliation on the Physiology and Growth of Potted Douglas-Fir Seedlings T.E. Kolb, K.A. Dodds, and K.M. Clancy ABSTRACT. 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 • 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. An Analysis of Monte Carlo Integer Programming, Simulated Annealing, and Tabu Search Heuristics for Solving Spatial Harvest Scheduling Problems K. Boston and P. Bettinger ABSTRACT. 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. Regional Distribution and Dynamics of Coarse Woody Debris in Midwestern Old-Growth Forests M.A. Spetich, S.R. Shifley, and G.R. Parker ABSTRACT. 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 greater than or equal to 10 cm in diameter and standing trees greater than or equal to 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 less than or equal to 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.
Forest Science, Volume 45, Number 1, February 1999
A Methodology to Analyze
Divergent Case Studies of Non-Timber Forest Products and Their
Dvelopment Potential
Manuel Ruiz Pérez and Neil Byron
ABSTRACT. 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.
Long-Term Dynamics of Lodgepole Needle Miner Populations in
Central Oregon
Richard R. Mason and H. Gene Paul
ABSTRACT. 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.
Simulation of Thinning with a Single-Grip Harvester
Lars Eliasson
Abstract. 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.
Basal Area Growth and Crown Closure in a Loblolly Pine Spacing
Trial
Philip J. Radtke and Harold E. Burkhart
ABSTRACT. 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.
Spatial Restrictions in Harvest Scheduling
Alan T. Murray
Abstract. 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.
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, and Donald
L. Martinez
Abstract. 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.
Stakeholder Perspectives on Appropriate Forest Management in the
Pacific Northwest Anne R. Kearney, Gordon Bradley, Rachel Kaplan, and Stephen
Kaplan Abstract. 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.
Tree Mortality Following Defoliation by the European Gypsy Moth
(Lymantria dispar L.) in the United States: A Review
Christopher B. Davidson, Kurt W. Gottschalk, and James E. Johnson
ABSTRACT. 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.
Compatible Volume and Taper Models with Coefficients for Tropical
Species on Hainan Island in Southern China
Zixing Fang and Robert L. Bailey
Abstract. 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.
Within-Stem Variation in Tropolone Content and Decay Resistance of
Second-Growth Western Redcedar
Jeffrey D. DeBell, Jeffrey J. Morrell, and Barbara L. Gartner
ABSTRACT. 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.
A Linear Programming, Tabu Search Method for Solving Forest-Level
Bucking Optimization Problems
Andre Laroze
Abstract. 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.
Three-Year Survival and Growth of Douglas-Fir Seedlings Under
Various Vegetation-Free Regimes
R. Rose, J.S. Ketchum, and D.E. Hanson
ABSTRACT. 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 m 2). 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 ï 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.
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, and Randolph
A. Wilson
Abstract. 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 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
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Temperature
Factorial Experiment with Pinus sylvestris L. Seedlings
60% and lower proportions of areas with 20-39%
canopy cover than nonbreeding-season ranges. Owls roosted and foraged in
stands with