bluuebunny/crossref_metadata_2025 huggingface dataset:
Growth and Water Use of Red Spruce (Picea Rubens Sarg.) Exposed to Ozone and Simulated Acidic Precipitation for Four Growing Seasons
Authors: Laurence J. A. , Amundson R. G. , Kohut R. J. , Weinstein D. A.
Published: April 2024

Red spruce (Picea rubens Sarg.) saplings from a pristine site in Maine were transplanted in native soil to 360 liter pots and relocated to Ithaca, New York. After a 1 yr establishment period, 90 saplings were chosen for use, assigned to treatments, placed in large open-top chambers, and exposed to ozone (0.5 to 2.0 x ambient concentration) and simulated acidic precipitation (at pH 3.1, 4.1, or 5.1) for 3 or 4 consecutive growing seasons (total ozone exposures of about 165 ppm · hr to almost 570 ppm · hr). Forty-five trees were grown on weighing lysimeters and were used to develop whole-tree water-use budgets. After 3 yr of exposure, the 45 trees not grown on lysimeters were harvested, and the plant tissues were weighed. After the fourth growing season, the remaining 45 trees were harvested, and the weight of the plant tissues was determined. Significant effects of ozone or simulated acidic precipitation were not detected, with the exception of a trend for increased needle dry weight with increasing ozone and, in 1990 needles only, with decreasing pH. No effects were detected in total dry weight, aboveground dry weight, coarse or fine root weight, stem dry weight, or relative growth rate. No significant interactions of ozone and pH treatment were detected. Neither ozone nor pH treatment affected the rate of water use by red spruce saplings, even when they were subjected to a dry-down period resulting in drought stress. For. Sci. 43(3):355-361.
The Effects of Neighborhood Storage Size on Dynamic Programming Solutions
Authors: Pelkki Matthew H.
Published: April 2024

Forward recursive dynamic programming (DP) was used to investigate the sensitivity of two- and three-state dynamic programming networks to neighborhood storage. Two-state DP networks were formed using all pairwise combinations of four state variables (basal area, cubic foot volume, number of trees, and diameter) and various neighborhood intervals for each state variable. As state neighborhoods decreased in size, all solutions were converged on a single rotation scheme and objective function value. Large state neighborhoods with nonuniform future growth and value potentials result in suboptimal solutions and incorrect sensitivity analyses. Comparison of various two-state networks indicate that models incorporating net cubic volume are less sensitive to increases in state neighborhood size. The addition of both a forward "look ahead" heuristic and the "harvest type" state variable to two-state networks improved the objective function value when neighborhoods were large and had nonuniform intra-neighborhood future growth and value potentials. However, these additional efforts resulted in no improvement in the objective function value when small state neighborhoods were used, further supporting the hypothesis that the DP algorithm did find the global optimum solution for the given problem formulation. For. Sci. 43(3):387-395.
A Compatible Growth-Density Stand Model Derived from a Distance-Dependent Individual Tree Model
Authors: Shao Guofan , Shugart Herman H.
Published: April 2024

A compatible growth-density stand model is developed for simulating forest stands with uniformly distributed trees (e.g., square spacing, equilateral triangle spacing, and 1:1.5 row to column ratio tree distribution patterns). The model is based on a distance-dependent individual-tree competition model. The independent variable in the individual-tree model is Hegyi's (1974) diameter-distance competition index with n = 8. The derived growth density stand model satisfies a necessary boundary condition (i.e., stand growth is zero either when stand density is zero or when stand density reaches to a very high level). The stand density which maximizes stand growth rate can be calculated with this stand model. It is found that stands with an equilateral triangle tree distribution pattern have the greatest growth rate among the three uniform stands. Stand growth in measured forests is more than 10% lower than that predicted in uniform stands. Simulation comparisons suggest that the uneven distribution of trees in such stands can reduce stand growth. For. Sci. 43(3):443-446.
Correlation of Counts of Gypsy Moths (Lepidoptera: Lymantriidae)in Pheromone Traps with Landscape Characteristics
Authors: Sharov Alexei A. , Liebhold Andrew M. , Roberts E. Anderson
Published: April 2024

The effect of landscape characteristics (elevation, slope, aspect, and vegetation) on counts of gypsy moths in pheromone traps was studied in a >5 million ha area in Virginia and West Virginia from 1988 to 1994. Habitat effects on population numbers depend on dominant ecological processes in the area: we define K-, r-, and c-effects as differences in carrying capacity, population growth rate, and colonization rate, respectively, that are associated with different landscape characteristics. To differentiate among these effects, we analyzed individually the following three zones at the expanding front of the gypsy moth population: infested (K-effects), transition (r-effects), and uninfested (c-effects). Among landscape characteristics, elevation was most highly correlated with moth counts. Moth counts increased with increasing elevation in the infested and transition zones (K- and r- effects) which may be associated with good habitats at high elevation. However, the highest average moth counts in the uninfested zone were found at low elevation. Possibly this was a c-effect which resulted from a greater colonization rate in the low-elevation areas where human population densities are greater and the probability of inadvertent transfer of egg masses on human vehicles is increased. The effect of vegetation on moth counts was much less pronounced than the effect of elevation. Moth catches were higher in deciduous and mixed forests than in coniferous forests and nonforested areas. The effect of landscape characteristics on moth captures was stronger in the transition zone than in other zones. For. Sci. 43(4):483-490.
Modeling Dominant Height Growth: Eucalyptus Plantations in Portugal
Authors: Amaro Ana , Reed David , Tomé Margarida , Themido Isabel
Published: April 2024

Difference forms of the well-known Chapman-Richards and Lundqvist-Korf biological growth models are derived for use in modeling dominant height growth using data from remeasured permanent plots. The performance of these models is compared with the performance of the McDill-Amateis difference model for describing dominant height growth of eucalyptus plantations in Portugal. The final model is a difference form of the Chapman-Richards equation with the m shape parameter constrained by initial stand conditions. The model is regional in that there are different estimated parameter values for highly productive sites in the coastal region of Portugal compared to lower productivity sites in the interior. The effect of using overlapping or nonoverlapping measurement intervals in the estimation process is examined with independent data; there appears to be little difference in the predictive ability of the resulting models. For. Sci. 44(1):37-46.
Using Simultaneous Regression Techniques with Individual-Tree Growth Models
Authors: Hasenauer Hubert , Monserud Robert A. , Gregoire Timothy G.
Published: April 2024

Individual-tree growth models basically consist of a number of equations (e.g., diameter or basal area increment model, height increment model, crown ratio model) to update tree parameters over time. These equations commonly are assumed to be independent, with parameters of each equation estimated separately rather than simultaneously with linear or nonlinear regression. However, the opposite assumption of interdependence seems more reasonable. A tree is a highly organized system, and assimilation of tissues in the form of diameter increment, height increment, and crown size does not occur independently. Procedures to simultaneously estimate systems of two or more interrelated models are well developed in the econometrics literature and are suggested as a viable alternative. Using more than 7,500 Norway spruce (Picea abies L. Karst) trees from the Austrian National Forest Inventory with remeasured breast height diameters and tree heights (5 yr interval), we compare an individual tree basal area increment model, a height increment model, and a crown ratio model separately using ordinary least squares (OLS) and simultaneously by applying two-and three-stage least squares (2SLS, 3SLS). Results indicate the presence of strong cross-equation correlations, especially between the basal area increment and height increment models. Thus, the 3SLS estimates are more efficient while the separately determined OLS estimates are biased. Two parameters that OLS indicates are significant are found to be nonsignificant when simultaneously estimating all system parameters with 3SLS. Such system simplification reduced the size of the variance-covariance matrix by 100 elements. For. Sci. 44(1):87-95.
Modeling the Basal Area-size Distribution of Forest Stands: A Compatible Approach
Authors: Gove Jeffrey H. , Patil Ganapathi P.
Published: April 2024

This paper presents a methodology that allows diameter distributions to be conformably modeled by letting the probability density represent either tree frequency as in the classic case, or basal area. The key to relating the two forms of the probability density is shown to lie in weighted distribution theory. The motivation for the relationship lies in the quadratic relationship between diameter at breast height and basal area. The weighted distribution approach is shown to be compatible with current methods of calculating quantities such as basal area by diameter class, but in addition, affords the development of new equations useful in parameter recovery or similar modeling strategies. Relationships are developed for all of the major distributions found to have been useful in forestry for fitting diameter distribution models. Several stands to which the two- and three-parameter Weibull distributions have been fitted are also presented. For. Sci. 44(2):285-297.
Leaf Area and Above- and Belowground Growth Responses of Loblolly Pine to Nutrient and Water Additions
Authors: Albaugh Timothy J. , Allen H. Lee , Dougherty Phillip M. , Kress Lance W. , King John S.
Published: April 2024

A 2 x 2 nutrient and water factorial experiment with four replications was installed in an 8-yr-old stand of loblolly pine (Pinus taeda L.) growing on an infertile, excessively drained sandy site in Scotland County, North Carolina. After the fourth year of treatment, estimated stem volume increment, total biomass production, and peak leaf area index (LAI) increased 152%, 99%, and 101%, respectively, with fertilization and 25%, 23%, 16%, respectively, with irrigation. Stem volume growth efficiency (growth per unit LAI) increased 21% with fertilization, 9% with irrigation, and 30% with both fertilization and irrigation. Total biomass production efficiency increased 91% with fertilization, 29% with irrigation, and 120% with both fertilization and irrigation. The observed increase in stem volume growth efficiency may have been due, in part, to changes in biomass partitioning. However, altered partitioning patterns alone did not explain the observed increase in total biomass production efficiency. We hypothesized that the change in total biomass production efficiency may have been a result of greater allocation to foliage (photosynthesizing tissue) and less allocation to fine roots (a high maintenance respiration tissue) under fertilization and irrigation treatments. For. Sci. 44(2):317-328.
Long-Term Dynamics of Lodgepole Needle Miner Populations in Central Oregon
Authors: Mason Richard R. , Paul H.Gene
Published: April 2024

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.
Evaluation of the Barr & Stroud FP15 and Criterion 400 Laser Dendrometers for Measuring Upper Stem Diameters and Heights
Authors: Williams Michael S. , Cormier Kenneth L. , Briggs Ronald G. , Martinez Donald L.
Published: April 2024

Calibrated Barr & Stroud FP15 and Criterion 400 laser dendrometers were tested for reliability in measuring upper stem diameters and heights under typical field conditions. Data were collected in the Black Hills National Forest, which covers parts of South Dakota and Wyoming in the United States. Mixed effects models were employed to account for differences between users of the dendrometers and to test for significant differences between the heights and diameters measured indirectly (by dendrometer) and directly (by caliper and linear tape). The location at which measurements were taken on each tree was determined by paint marks along the bole. No significant differences between users were found. The Barr & Stroud consistently overestimated diameters by approximately 0.3 cm (0.1 in). Unbiased estimates of diameter were obtained with the Criterion 400. For height measurements, neither the Barr & Stroud nor the Criterion 400 produced unbiased measurements. The effect of distance to the base of the tree and height of the diameter measurement on the variability of the measurements was also studied. As distance increased, the variability of diameter measurements increased for both dendrometers. For the measurement of height, only the Barr & Stroud exhibited an increase in the variability of measurements with increasing distance. After correcting the data for their biases, taper equations were fitted to them and analyzed. The equations generated from the Barr & Stroud were not significantly different from those generated from direct measurement, unlike the Criterion 400 where taper equations generated were statistically different. A brief study of the effects of familiarity with each dendrometer indicated that the measurement error and variability decreased as the user became more familiar with the Criterion. This was not the case for the Barr & Stroud. For. Sci. 45(1):53-61.
Tree Mortality Following Defoliation by the European Gypsy Moth (Lymantria dispar L.) in the United States: A Review
Authors: Davidson Christopher B. , Gottschalk Kurt W. , Johnson James E.
Published: April 2024

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.
Estimating Economic Gains for Landowners Due to Time-Dependent Changes in Biotechnology
Authors: Wagner John E. , Holmes Thomas P.
Published: April 2024

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.
Effect of Western Spruce Budworm Defoliation on the Physiology and Growth of Potted Douglas-Fir Seedlings
Authors: Kolb Thomas E. , Dodds Kimberly A. , Clancy Karen M.
Published: April 2024

Interactions between effects of insect defoliators on tree physiology and growth and soil nutrient and water availability are poorly understood. We addressed whether the western spruce budworm influences nutrient and water relations, ectomycorrhizae, leaf gas exchange, and growth of Douglas-fir seedlings under different environmental conditions. Four-year-old, potted seedlings were grown in two soil types (basalt-derived, limestone-derived) with two levels of soil moisture (high, low) and were subjected to three levels of budworm defoliation (none, moderate, heavy) and two levels of frass and litter produced by budworm feeding (with, without) over 2 yr in a greenhouse environment. Defoliation, soil moisture, and soil type influenced allocation of seedling biomass to leaves, stems, and roots. The addition of frass and litter had no effect on any measured soil or tree characteristic. Interactions between defoliation and other experimental factors were not important except for the defoliation x soil moisture interaction where heavy defoliation reduced the negative effects of low soil moisture on seedling predawn water potential, net photosynthetic rate, and stomatal conductance. Heavily defoliated seedlings had less biomass, higher foliar concentrations of N, Ca, and Mg, less ectomycorrhizae, and higher net photosynthetic rate and stomatal conductance compared with nondefoliated seedlings. For. Sci. 45(2):280-291.
Incomplete Block Designs for Genetic Testing: Statistical Efficiencies with Missing Observations
Authors: Fu Yong-Bi , Yanchuk Alvin D. , Namkoong Gene , Clarke G. Peter Y.
Published: April 2024

Missing observations are common in forest genetic field trials and are expected to reduce statistical efficiencies of any applied field designs. Such reductions could lower the presumed efficiency and other benefits of implementing any incomplete block designs (ICBs). In this study, we addressed this by computer simulation of a full-sib progeny trial with up to 20% of the observations missing. Four scenarios of missing observations (random, row, column, and genetic mortality) and tests of both clones and seedling families were examined. Two types of ICBs (alpha and no constraint) with single-tree plots, and their corresponding randomized complete block design (RCB), were considered on test sites with gradient and patchy environmental variation. Our simulations show that: (1) the statistical efficiencies of estimating family (or clone) means with both ICB and RCB were very sensitive to the percentage, not the scenarios, of missing observations examined; (2) the statistical efficiencies for both ICB and RCB were reduced as the number of missing observations increased, except in the cases of clonal genetic mortality; (3) the relative efficiency of ICB over RCB (at equal levels of missing observations) was reduced slightly as the level of missing observations increased; (4) the relative efficiencies for the seedling family tests were a little more sensitive to the levels of missing observations than those for the clonal tests, and; (5) the two ICBs showed little variation in the relative efficiencies across the missing observation scenarios and test conditions examined. Implications of these results for forest genetic field trials are discussed. For. Sci. 45(3):374-380.
Sweetgum and Broomsedge Response to Competition Across a Range of Soil Organic Matter During the First Year of Plant Establishment
Authors: Zutter Bruce R. , Glover Glenn R. , Mitchell Robert J. , Gjerstad Dean H.
Published: April 2024

Sweetgum (Liquidambar styraciflua L.) seedlings and broomsedge (Andropogon virginicus L.) rooted tillers were planted in a factorial combination of densities (additive series) in east central Alabama on a formerly cultivated field which varied in soil organic matter (soil OM). Mean plant aboveground biomass of sweetgum one growing season after planting declined in a hyperbolic fashion as a function of increasing density of either itself or broomsedge. Broomsedge biomass over the same time period also declined in a hyperbolic fashion as a function of increasing density of itself and sweetgum, except for sweetgum densities from 0 to 1 m-2, where biomass did not change. Sweetgum response was positively correlated with soil OM across all species-density combinations, whereas broomsedge response was correlated with soil OM only at higher densities of broomsedge. Nonlinear models including both species density and soil OM explained a nearly equal amount of variation in response of each species: 74 to 75% for sweetgum and 70% for broomsedge. Relative effects of intraspecific versus interspecific competition on the response of each species was dependent on the density of one or both species. Effect of sweetgum on broomsedge response was two to three times that of broomsedge on itself, with the effect decreasing slightly as soil OM decreased. Over a common range of densities of each species, effects of broomsedge on sweetgum were slightly greater than or nearly equal to effects of sweetgum on itself. The greater interspecific effects on the response of each species suggests no niche differentiation between broomsedge and sweetgum through one growing season. For. Sci. 45(3):423-432.
Forest Stand Structure of the Northern Spotted Owl's Foraging Habitat
Authors: North Malcolm P. , Franklin Jerry F. , Carey Andrew B. , Forsman Eric D. , Hamer Tom
Published: April 2024

Although the spotted owl's close association with old growth has been extensively studied, it has been more difficult to identify and quantify the abundance of particular stand structures associated with preferred owl foraging sites. Old-growth forests have a suite of characteristics that distinguish them from younger forests but which also make it difficult to isolate individual structural features important to the spotted owl. This study used an analysis of use-only sites in areas where natural disturbance had created a gradient of old-growth structural characteristics. We used radio telemetry data collected from reproducing owl pairs to locate sample stands and compute a relative measure of owl-use intensity in each stand. Snag volume and tree height class diversity (a measure of canopy layering) were the stand structures significantly associated with owl foraging intensity. Stands with 142 m³/ha of intact snags and a high diversity of tree heights had medium or high foraging use by spotted owls. In these old-growth stands, biological legacies (e.g., large trees and snags) produced by past disturbance provide important forest structures associated with spotted owl foraging use. For. Sci. 45(4):520-527.
Assessing Uncertainty in a Stand Growth Model by Bayesian Synthesis
Authors: Green Edwin J. , MacFarlane David W. , Valentine Harry T. , Strawderman William E.
Published: April 2024

The Bayesian synthesis method (BSYN) was used to bound the uncertainty in projections calculated with PIPESTEM, a mechanistic model of forest growth. The application furnished posterior distributions of (a) the values of the model's parameters, and (b) the values of three of the model's output variables--basal area per unit land area, average tree height, and tree density--at different points in time. Confidence or credible intervals for the output variables were obtained directly from the posterior distributions. The application also provided estimates of correlation among the parameters and output variables. BSYN, which originally was applied to a population dynamics model for bowhead whales (Raftery et al. 1996, JASA 90:402-442), is generally applicable to deterministic models. Extension to two or more linked models is discussed. A simple worked example is included in an appendix. For. Sci. 45(4):528-538.
Dynamics of Coarse Woody Debris Placed in Three Oregon Streams
Authors: Keim Richard F. , Skaugset Arne E. , Bateman Douglas S.
Published: April 2024

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.
Logistic Regression for Southern Pine Beetle Outbreaks with Spatial and Temporal Autocorrelation
Authors: Gumpertz Marcia L. , Wu Chi-tsung , Pye John M.
Published: April 2024

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.
Modeling the Size–Density Relationship in Direct-Seeded Slash Pine Stands
Authors: Cao Quang V. , Dean Thomas J. , Baldwin V. Clark
Published: April 2024

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
Authors: Hesseln Hayley
Published: April 2024

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):322–334.
A Solution Method for Uneven-Aged Management Applied to Norway Spruce
Authors: Wikström Peder
Published: April 2024

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.
Persistence of Growth Variation in Tree-Ring Chronologies
Authors: Yoo Seung Jick , Wright Brian D.
Published: April 2024

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
Authors: Odum Howard T. , Doherty Steven J. , Scatena Frederick N. , Kharecha Pushker A.
Published: April 2024

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 × 10 4 sej/J) and succession forest (3.9 × 104 sej/J). FOR. SCI. 46(4):521–530.
Alternative Measurements of Productive Efficiency in the Global Bleached Softwood Pulp Sector
Authors: Yin Runsheng
Published: April 2024

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.
Process Models as Tools in Forestry Research and Management
Authors: Johnsen Kurt , Samuelson Lisa , Teskey Robert , McNulty Steve , Fox Tom
Published: April 2024

Forest process models are mathematical representations of biological systems that incorporate our understanding of physiological and ecological mechanisms into predictive algorithms. These models were originally designed and used for research purposes, but are being developed for use in practical forest management. Process models designed for research typically require complicated and intensive data, whereas models designed for management strive to use simpler and more readily available data and provide predictions useful for forest managers. In this article, we review some different types of process models, examine their requirements and utility in research and forest management, and discuss research priority areas that will increase their accuracy and application. We conclude that soil and nutritional limitations are the most difficult model components in predicting growth responses using process models. FOR. Sci. 47(1):2–8.
Evaluation of Modeled Carbon Fluxes for a Slash Pine Ecosystem: SPM2 Simulations Compared to Eddy Flux Measurements
Authors: Clark Kenneth L. , Cropper Wendell P. , Gholz Henry L.
Published: April 2024

A process-based model (SPM2) was developed to simulate net hourly exchanges of carbon for slash pine (Pinus elliottii var. elliottii) ecosystems in north-central Florida, and simulated values were compared to those obtained using eddy covariance measurements above the canopy. The SPM2 simulated relatively low hourly rates of net carbon exchange at high irradiance during the day, especially during the month of May. This discrepancy contributed the most to differences between the two approaches, and suggests that the model underestimates the maximum rate of leaf-level net photosynthesis during the period of rapid growth in the spring. The SPM2 also simulated lower net carbon release during the nighttime across the range of air temperatures, relative to eddy covariance measurements. As a result of these discrepancies, accumulated daytime and nighttime sums were quite different between the two approaches. However, once results were aggregated over 24 hr, differences between simulations and measurements were insignificant at all but the highest and lowest daily net carbon gain values. Annual estimates for 1996 were similar: 693, 719, and 745 g C m-2 yr-1 for the SPM2 model, eddy covariance measurements and mass balance measurements, respectively. This model evaluation has lead to specific research questions for guiding further model development. FOR. Sci. 47(1):52–59.
Biophysical Site Indices for Shade Tolerant and Intolerant Boreal Species
Authors: Ung Chhun-Huor , Bernier Pierre Y. , Raulier Frédéric , Fournier Richard A. , Lambert Marie-Claude , Régnière Jacques
Published: April 2024

Two variants of a biophysical site index model were derived for two shade-tolerant boreal species (Abies balsamea [L.] Mill., and Picea mariana [Mill.] BSP), and two shade-intolerant boreal species (Populus tremuloides Michx., and Betula papyrifera Marsh.). The reduced model is based on the widely used assumption that the relationship between height and age of dominant trees depends solely on site properties: i.e., four climatic variables (degree-days, vapor pressure deficit, aridity index, and precipitation), and one edaphic variable (soil water-holding capacity). The full model is based on the further assumption that site index also depends on the stand successional stage represented by the dbh distribution index. The reduced model is accurate and unbiased for both intolerant species, but it becomes inaccurate and underestimates the mature stand dominant height for both tolerant species. The full model is equivalent to the reduced model for both intolerant species, but becomes two or three times more accurate and unbiased for both tolerant species. When incorporated into a growth and yield model as the site quality index, the reduced model performs as well as the traditional phytometric model (derived solely from an empirical fit of dominant height and age without any biophysical data) for both intolerant species, but it becomes biased for both tolerant species. By contrast, the full model, when used as a site quality index in the growth and yield model, is unbiased and equivalent to the phytometric model for the four species. These results show that the site index of intolerant species can be solely associated with climatic and edaphic variables, but these variables have to be completed by the successional stage for correctly estimating the site index of the tolerant species. FOR. Sci. 47(1):83–95.
Severe Drought Effects on Mediterranean Woody Flora in Spain
Authors: Peñuelas Josep , Lloret Francisco , Montoya Ramón
Published: April 2024

The severe drought in 1994 damaged the woody flora of central and southern Spain (80% of the 190 studied sites presented drought-damaged species). In 1996, after a wet year, 67% of the sites were still affected. Different degrees of damage and recovery were found among different functional types (trees or shrubs), and genera of different evolutionary history (Mediterranean or pre-Mediterranean). The Mediterranean genera, mostly shrubs evolved under Mediterranean climate conditions, i.e., later than 3.2 M years ago in the Pliocene, were more damaged by the drought than the earlier evolved pre-Mediterranean genera, mostly trees. However, the Mediterranean genera were more resilient and recovered much better after the following wet year. FOR. SCI. 47(2):214–218.
A Longitudinal Study of Environmental Attitudes of Women and Gender Diversification in the U.S. Forest Service 1990–1996
Authors: Brown Greg , Harris Charles C.
Published: April 2024

The USDA Forest Service has been dominated by white, male foresters. Beginning in the mid-1970s, the agency was compelled legally and morally to begin diversifying its workforce by race, gender, and profession. Concurrent with workforce diversification efforts, the agency confronted demands from the courts, Congress, and interest groups to change national forest management by emphasizing national forest preservation over the production of commodities such as timber and livestock forage. This study examines the role of women as potential organizational change agents by analyzing survey data collected from two national studies of the Forest Service in 1990 and 1996. Results from the 1996 study indicate that women continue to exhibit higher levels of general environmental concern than men, suggesting their role as potential “saviors” in helping the agency to make the transition to increased emphasis on ecosystem management. Conversely, diversification of the Forest Service workforce continues to be highly contentious, with some employees feeling that the recruitment and promotion of women without adequate training and/or experience have left the agency unprepared to meet complex demands. The inability of the Forest Service to satisfy multiple, conflicting constituencies in the face of agency downsizing suggests the role of women as “scapegoats,” whose perceived lack of experience is responsible for agency shortcomings. The authors suggest that the historical convergence of workforce diversification with changes in national forest policy inevitably place women in the conflicting roles of both “saviors” and “scapegoats.” FOR. SCI. 47(2):246–257.
Burning Characteristics of Needles from Eight Pine Species
Authors: Fonda Richard W.
Published: April 2024

Ponderosa pine (Pinus ponderosa), Jeffrey pine (P. jeffreyi), longleaf pine (P. palustris), and south Florida slash pine (P. elliottii var. densa) are fire resisters. Trees of these species are able to survive the direct effects of wildfires. Monterey pine (P. radiata), knobcone pine (P. attenuata), sand pine (P. clausa), and jack pine (P. banksiana) are fire evaders. Trees of these species are killed by wildfire, but species survive on the postfire site via seed germination. Needles were burned in a 2×2 factorial experiment to compare these eight species, all of which are prominent in fire-related communities. The experiment tested two factors—fire adaptive strategy (resisters vs. evaders), geographic region (western vs. eastern United States)—and interactions between those two factors. Flame height, flame time, ember time, burn time, percent fuel combusted, and mean rate of weight loss were measured. Longleaf pine, ponderosa pine, and south Florida slash pine had the highest values for flame height, percent fuel combusted, and mean rate of weight loss. Knobcone pine and Monterey pine had the longest ember time and burn time. Sand pine and jack pine had the longest flame time. Resisters tested highest in flame height, percent fuel combusted, and mean rate of weight loss. Evaders had greater flame and burn times. Western pines were significantly greater than eastern pines in all burning characteristics except flame time and mean rate of weight loss. Significant interactions between fire adaptive strategy and geographic region existed for all burning characteristics except mean rate of weight loss. The interaction was accounted for primarily by differences between western evaders, which had some of the highest values for each characteristic, and eastern evaders, which had some of the lowest values. FOR. SCI. 47(2):390–396.
BOOK REVIEWS: Writing and Presenting Scientific Papers
Authors: Covert Sarah F.
Published: April 2024

Effective writing and oral presentation skills are essential tools for any scientist. Nothing less than one's employment, grant support, publication record, and scientific impact all depend on these abilities. It is surprisingly rare, however, for graduate training programs to address these issues through formal study. As a consequence, I suspect that many young scientists enter the world of independent research with less than stellar writing skills, and I know from unfortunate experience that many seasoned scholars have yet to fully master the art of the scientific seminar. There is a clear need for instruction in these areas, but how can graduate trainers effectively teach their students these skills when they most likely acquired them only through the horrors of trial and error, or the luck of natural talent? Furthermore, how can an established scientist or a motivated student polish his or her communication skills through independent study? Malmfors, Garnsworthy, and Grossman provide lucid and concise answers to these questions in their very useful, no-nonsense handbook.
BOOK REVIEWS: Invasive Plants of California's Wildlands
Authors: Pimentel David
Published: April 2024

Invasive Plants of California's Wildlands provides detailed information on the biology and control of 78 nonnative plant species that were listed as Exotic Invasive Plants of Greatest Ecological Concern by the California Exotic Pest Plant Council. These invasive, nonnative species were discussed because they are already growing wild in California and are causing or have the potential to be a serious threat to state parks, preserves, and other wildlands.