bluuebunny/crossref_metadata_2025 huggingface dataset:
A Method to Distribute Mortality in Diameter Distribution Models
Authors: Cao Quang V.
Published: April 2024

Bailey (1980) derived tree diameter growth models by transforming variables which preserved the functional form of the probability density function that approximated diameter distributions. The necessary assumption was either no mortality, or that mortality was proportionally distributed among diameter classes. The latter assumption might not be realistic since smaller trees should suffer more from competition than large trees and are more likely to die. This paper deals with the case when mortality is not proportionally distributed. If diameters in a stand originally follow a Weibull distribution and mortality for a growing period can be assumed to occur at the beginning of that period, then a Weibull was found to successfully approximate the diameter distribution immediately after mortality. The stand then grows without further mortality and reaches the end of the period with its diameters remaining Weibull. A similar method to derive a diameter distribution after mortality was developed for the beta distribution. The Weibull technique was applied to data from loblolly plantations. Results showed that the new approach worked reasonably well and was comparable with a diameter distribution model in approximating diameter distribution of a stand at the end of the growth period. For. Sci. 43(3):435-442.
A Distribution-Independent Approach to Predicting Stand Diameter Distribution
Authors: Tang Shouzheng , Wang Yonghe , Zhang Lianjun , Meng Cho-Ho
Published: April 2024

A new approach to projecting future stand diameter distribution was proposed without assuming a predefined probability density function. The Lebesque-Stieltjes integral was applied to derive a group of equations for the relationships between current and future stand diameter distributions and stand-level attributes. The parameters in the tree survival function and diameter growth function were recovered using these equations based on independent estimates of future stand mean diameter, quadratic mean diameter, and survival from a whole stand model. This disaggregation approach ensured that the resolutions at size-class distribution and/or individual tree levels were compatible with the stand-level aggregates. A stochastic error component was incorporated into the tree diameter growth function. This allowed us to mimic the tree diameter differentiation process over time, and it improved prediction accuracy for future stand diameter distributions. The proposed approach can also be used to allocate stand growth and yield to a list of individual trees. The fluctuation of tree growth and survival for each tree can be implemented by simulating the variance of tree diameter growth and survival probability using Monte Carlo or error propagation methods. For. Sci. 43(4):491-500.
Managerial and Institutional Factors Affect Prescribed Burning Costs
Authors: González-Cabán Armando
Published: April 2024

Prescribed burning costs are extremely variable, even if conditions are similar. This variability complicates planning and evaluation of prescribed burning programs and budgets, resulting in imprecise projections of their economic benefits. Evaluating the worth of prescribed burning efforts in objective terms is difficult, but the continual shrinkage of USDA Forest Service budgets requires an increase in program efficiency and understanding the causes of variability for prescribed burning costs. An analysis of variance model was used to describe and quantify the relative effect of managerial and institutional factors, such as smoke emission limitations or the constraint to control all types of fires, on prescribed burning costs. Data were collected by using a questionnaire to fire and fuel managers in the USDA Forest Service's Northern, Intermountain, and Pacific Northwest Regions. Estimated prescribed burning costs were significantly affected by changes in the managerial and institutional factors, such as minimizing escape potential or complying with smoke emission standards presented to these fire managers. Contrary to our expectations, burn objective (the main reason for conducting the burn) was not a significant cost factor. Unit size of the burned area affected prescribed burning costs more than either change in slope or unit shape, both of which increase the amount of burn perimeter relative to the area burned. Costs per acre demonstrated economies of scale: the larger the unit burned, the lower its per-acre cost. For. Sci. 43(4):535-543.
Forest Harvesting and Minimum Cuts: A New Approach to Handling Spatial Constraints
Authors: Hochbaum Dorit S. , Pathria Anu
Published: April 2024

In this paper we discuss two forest harvesting optimization problems that arise in forest management. We consider one-stage decision problems in which the forest to be managed is partitioned into cells and the decision is to be made as to which cells to harvest. There are competing concerns to consider in assessing the value of a particular harvesting decision: the first has to do with the value of the timber harvested, and the second has to do with assessing the relative values of the resulting spatial layout from a wildlife habitat point of view. The two problems that we consider are similar, but they assess the relative merits of resulting spatial layouts somewhat differently and therefore have different objective functions to be optimized. The first problem we consider assigns benefits for harvesting cells and penalties for harvesting adjacent cells; the second problem considered assigns benefits for harvesting cells as well as benefits for creating borders that separate harvested and unharvested cells. We show that both forest harvesting problems can be interpreted as instances of the Generalized Independent Set graph optimization problem, which we introduce in this article. Generalized Independent Set is a generalization of the well-known Independent Set graph optimization problem (a set of nodes in a graph is said to be independent if no two nodes in the set are adjacent). When the underlying graph is bipartite, we derive an efficient solution method for Generalized Independent Set via network flow methods. If the cell structure is grid-like in the forest harvesting problems, then an instance of either forestry problem can be reduced to an instance of Generalized Independent Set on a bipartite graph. For such instances we developed efficient algorithms for determining an optimal harvesting strategy. The running time is O(n² log n), where n is the number of cells in the land area to be spatially managed. For. Sci. 43(4):544-554.
A Comparison of Timber Market Models: Static Simulation and Optimal Control Approaches
Authors: Sohngen Brent , Sedjo Roger
Published: April 2024

In this paper, we compare and contrast two types of timber models that have been used to analyze the market impacts of policy proposals or exogenous forces that affect timber markets. The framework and theory for static simulation and optimal control models are presented and discussed. We then compare single region, empirical versions of the models across six scenarios of exogenous economic shocks. The models are found to predict different outcomes for timber market behavior when demand changes, or when young timber is affected by a supply shock. Similar outcomes between the models are obtained when older timber stocks are affected by shocks, or when the exogenous forces impact timber markets gradually over time. For. Sci. 44(1):24-36.
Transect Relascope Sampling--A Method for the Quantification of Coarse Woody Debris
Authors: Ståhl Göran
Published: April 2024

A method for the quantification of coarse woody debris in terms of the total length of downed material is presented. The method combines relascope and line intersect sampling theory. Estimation is based on a count of downed logs using a relascope instrument along survey lines. In cost-efficiency comparisons with line intersect and circular plot sampling, the proposed method was found to be a competitive alternative. For. Sci. 44(1):58-63.
Use of Individual Tree Mixed Models to Account for Mortality and Selective Thinning When Estimating Base Population Genetic Parameters
Authors: Wei Xianming , Borralho Nuno M. G.
Published: April 2024

The ability of individual tree mixed models to estimate unbiased genetic parameters was investigated for growth, Pilodyn penetration, and bark thickness, in an Eucalyptus urophylla progeny trial where the smaller trees have been previously thinned. A multivariate Restricted Maximum Likelihood (REML) analysis including the growth measurements of all trees prior to thinning, and later measurements of only those that remained, resulted in almost unbiased estimates of heritabilities and age-age genetic correlations for growth traits at all ages. Analysis based only on trees remaining after thinning resulted in considerably lower estimates of heritabilities and age-age genetic correlations. On the other hand, genetic parameters for Pilodyn penetration or bark thickness were not affected by the thinning. This was due to the low correlations between the thinning criteria (tree size) and the wood and bark traits. For. Sci. 44(2):246-253.
Determining the Optimal Planting Density and Land Expectation Value--A Numerical Evaluation of Decision Model
Authors: Gong Peichen
Published: April 2024

Different decision models can be constructed and used to analyze a regeneration decision in even-aged stand management. However, the optimal decision and management outcomes determined in an analysis may depend on the decision model used in the analysis. This paper examines the proper choice of decision model for determining the optimal planting density and land expectation value (LEV) for a Scots pine (Pinus sylvestris L.) plantation in northern Sweden. First, a general adaptive decision model for determining the regeneration alternative that maximizes the LEV is presented. This model recognizes future stand state and timber price uncertainties by including multiple stand state and timber price scenarios, and assumes that the harvest decision in each future period will be made conditional on the observed stand state and timber prices. Alternative assumptions about future stand states, timber prices, and harvest decisions can be incorporated into this general decision model, resulting in several different decision models that can be used to analyze a specific regeneration problem. Next, the consequences of choosing different modeling assumptions are determined using the example Scots pine plantation problem. Numerical results show that the most important sources of uncertainty that affect the optimal planting density and LEV are variations of the optimal clearcut time due to short-term fluctuations of timber prices. It is appropriate to determine the optimal planting density and harvest policy using an adaptive decision model that recognizes uncertainty only in future timber prices. After the optimal decisions have been found, however, the LEV should be re-estimated by incorporating both future stand state and timber price uncertainties. For. Sci. 44(3):356-364.
Survival of Hemlock Woolly Adelgid (Homoptera: Adelgidae) at Low Temperatures
Authors: Parker Bruce L. , Skinner Margaret , Gouli Svetlana , Ashikaga Takamaru , Teillon H. Brenton
Published: April 2024

The hemlock woolly adelgid (Adelges tsugae Annand [Homoptera: Adelgidae]) (HWA), a nonnative insect, is a major threat to New England forest and suburban environments, where one of its hosts, eastern hemlock, Tsuga canadensis (L.) Carrière, is a dominant native tree species. To determine the potential spread of HWA into northern New England, we studied the winter coldhardiness of a northerly population. Sistens were collected at three times during the winter and subjected to temperatures typical of those during winter in the next coldest USDA plant coldhardiness zone. Samples collected in January and February 1996 were subjected to -20, -25, and -30°C; those collected in March to -15, -20, and -25°C; all date-temperature treatments were tested at exposure times of 1, 2, 4, 8, and 24 hr. When all exposure times were combined, the percentage of live adelgids after subzero treatment (adjusted for control mortality at 0°C) declined significantly as temperature decreased. In most cases, fewer HWA were alive after treatment as exposure time increased. Significantly more HWA collected in January were alive after treatment than those collected in February and March. This suggests that HWA coldhardiness declines over this time period. When comparing the percentage of live HWA from February and March for -20 and -25°C, a noticeable decline occurred between the February and March sample dates. Although mortality was as high as 95% in one of the most severe treatments (February collection exposed to -30°C for 24 hr), the fact that complete mortality did not occur suggests that HWA may be able to continue to expand its range into areas with colder winters. For. Sci. 44(3):414-420.
Development and Evaluation of Habitat Models for Herpetofauna and Small Mammals
Authors: Block William M. , Morrison Michael L. , Scott Peter E.
Published: April 2024

We evaluated the ability of discriminant analysis (DA), logistic regression (LR), and multiple regression (MR) to describe habitat use by amphibians, reptiles, and small mammals found in California oak woodlands. We also compared models derived from pitfall and live trapping data for several species. Habitat relations modeled by DA and LR produced similar results, averaging about 70% classification success of the trapping stations to the correct group (capture or noncapture habitat). Although more variables were included in DA (4-5) than in LR (2-3), those included in LR were typically a subset of those in DA. On average, MR habitat models accounted for 56% of the variation in the index of relative species' abundance. The variables included in the MR models were seldom the same as those for DA and LR. Most differences between MR and the other two methods were related to differences in spatial scale: MR modeled habitat among grids, whereas DA and LR modeled habitat within grids. Habitat models for the same species differed between the trapping methods used. Live traps are most useful for describing general habitat relations of some small mammal species across large geographic areas, whereas pitfall traps are useful for intensive sampling of a larger portion of the vertebrate community within smaller geographic areas. Thus, the choice of trapping methods must be based on the study goals, biology of the species, and the spatial scale of study. For. Sci. 44(3):430-437.
Using Dynamic Programming and Overlapping Subproblems to Address Adjacency in Large Harvest Scheduling Problems
Authors: Hoganson Howard M. , Borges Jose G.
Published: April 2024

The adjacency problem for forest management scheduling is formulated as a dynamic programming problem. To overcome typical model-size problems, a solution strategy is proposed which links dynamic programming formulations for overlapping subproblems. Subproblems are solved sequentially in a moving-windows fashion. Solutions are near-optimal for three large but simplified test cases. Model size is sensitive to the size of the moving window. Using relatively small windows produced solutions that are closer to optimal than those found using two other modeling approaches. Solutions are also insensitive to the side of the forest used to start the moving-windows process, and microcomputer solution times are not a major consideration. The strategy offers potential to treat adjacency measures as valued management outputs. It will likely fit well into broader forestwide models which decompose the forestwide problem into parts to help address other forestwide constraints. For. Sci. 44(4):526-538.
Survival and Growth of Seedlings of Four Bottomland Oak Species in Response to Increases in Flooding and Salinity
Authors: Conner William H. , McLeod Kenneth W. , McCarron James K.
Published: April 2024

Four oak species representing a range of flood tolerance were chronically (simulating sea level rise) and acutely (simulating hurricane storm surge) exposed to increased flooding and salinity in a complete factorial experiment. Survival, growth, and final biomass were measured to assess differential species' responses. No Nuttall or overcup oak seedlings died when flooded with fresh water, but 10% of the swamp chestnut and 35% of the water oaks died. Floodwater salinities of 2 and 6 g L-1 resulted in mortality of all seedlings of all four species. Watering with 2 g L-1 saline water did not cause any mortality although leaf browning was evident in all species. Overcup oak seedlings were the most tolerant to watering with 6 g L-1 saline water (100% survival), while the other three species had high mortality. Increased salinity, both in watered and flooded conditions, generally resulted in decreased diameter growth and decreased root and shoot biomass. Short-term increases in salinity (simulated storm surge) resulted in total mortality of flooded seedlings, while drained seedlings recovered and leafed out the following spring. Results indicate that these bottomland oak species would be seriously affected by increased flooding and salinity from either hurricane storm surges or sea level rise. For. Sci. 44(4):618-624.
A Linear Programming, Tabu Search Method for Solving Forest-Level Bucking Optimization Problems
Authors: Laroze Andre
Published: April 2024

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.
Optimal Public Harvesting Under the Interdependence of Public and Private Forests
Authors: Koskela Erkki , Ollikainen Markku
Published: April 2024

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
Authors: Wang Sen , Van Kooten G. C.
Published: April 2024

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.
Vertical Overstory Canopy Architecture of Temperate Deciduous Hardwood Forests in the Eastern United States
Authors: Yang Xiusheng , Witcosky Jeffrey J. , Miller David R.
Published: April 2024

The stand attributes and vertical overstory profiles of plant area (the total projected surface area of all canopy elements including leaves, twigs, and stems) for 15 temperate deciduous hardwood forest types were studied and reported. The study was conducted across the eastern United States within forest type-groups of boreal hardwood, northern hardwood, and upland oak. Vertical distributions of plant area were measured with gap-fraction-based optical sensors mounted on a mobile sampling tower. In general, the stand attributes of the surveyed forest types exhibited distinct characteristics among the three type-groups. The vertical profile of the overstory plant area demonstrated significant differences among forest types and therefore represented an important architectural feature of a forest type. The vertical profile data were well described by a modified Weibull cumulative distribution function. The two model parameters, one indicating a depth for 63% foliage inclusion and the other representing skewness, were presented for each of the 15 forest types. These two model parameters can be used to depict the vertical distribution of overstory plant area in other stands of the same types. The vertical profiles of overstory plant area were related to the successional characteristics and understory tolerance. For. Sci. 45(3):349-358.
Developing Resource-Based Social Conflict Models for Assessing the Utility of Negotiation in Conflict Resolution
Authors: Germain René H. , Floyd Donald W.
Published: April 2024

Social conflicts over the management of natural resources are increasing. An informative example of these conflicts is the debate over the management of our national forests. Despite sincere efforts by the USDA Forest Service to improve modes of public involvement, as well as the institutionalization of dispute resolution procedures, the contentiousness and frequency of conflict continues to escalate. This is manifest in the high number of administrative appeals on forest plans and projects. The study used a nation-wide survey of 238 appellants (response rate of 75%) of Forest Service management decisions to test the predictive utility of social conflict models for determining the feasibility of negotiation in resolving environmental conflict. This paper addresses the question of whether the utility of negotiation can be predicted based on (1) the resources involved in the dispute, (2) how those resources are being utilized, and (3) the perceived impact on social, economic, and health issues. The social conflict models proved to have some utility in predicting the types of conflict that may be predisposed to resolution through negotiation. For. Sci. 45(3):394-406.
Recovering Tree Heights from Airborne Laser Scanner Data
Authors: Magnussen Steen , Eggermont Paul , LaRiccia Vincent N.
Published: April 2024

Airborne laser scanner data collected over forests provide a canopy height. To obtain tree heights from airborne laser scanner data one needs a recovery model. Two such models, one (A) assuming that observations are sampled with probability proportional to displayed crown area, and the other (B) derived from the probability that a laser beam penetrates to a given canopy depth, were developed and applied to laser scanner data obtained over stands of Douglas-fir. Model estimates of recovered arithmetic mean tree heights and quantiles (75%, 85%, and 95%) were not significantly (P> 0.24) different from ground-based equivalents. An overall mean bias of-3 m in the laser canopy heights was eliminated by both methods. The median absolute difference between observed and predicted plot means and quantiles were reduced by 40 to 60%. Three alternative recovery procedures are presented for model B. For a single plot, the predictions varied significantly among the models and estimation procedures with no consistent pattern. Predictions of arithmetic mean heights were best for plots with no understory, while predictions of upper quantiles were consistent in all plots. For. Sci. 45(3):407-422.
A Comparison of Periodic and Annual Forest Surveys
Authors: Scott Charles T. , Köhl Michael , Schnellbächer Hans Jörg
Published: April 2024

Forest surveys of large areas often are conducted on a periodic basis, every 10 yr, for example. However, periodic assessments can be problematic due to fluctuating budgets and survey results that do not reflect forest dynamics between measurements. As a result, many countries are interested in designing surveys with annual measurements, such as the U.S. Forest Health Monitoring (FHM) Program design. The existing periodic design for Switzerland was compared with four annual designs in which an equal number of plots are observed annually. Data for the comparisons were collected annually on 682 plots over 7 successive yr across Switzerland. Three estimation methods were applied to each design: Continuous Forest Inventory, Sampling with Partial Replacement, and Mixed Estimator. These used simple means, regression updating, and inverse weighting of new and old plots, and regression combined with growth-model projections, respectively. For 12 combinations of 3 attributes, the Regional Survey design was the most cost-effective, followed by the National or Regional Update Survey designs. The Periodic Survey and the National Survey (similar to the FHM design) were the least cost-effective. Sampling with Partial Replacement was the most efficient estimator, though the Mixed Estimator would have been the most efficient had less biased growth projection models been used. For. Sci. 45(3):433-451.
A Timber Extraction Method Based On Pavement Serviceability and Forest Inventory Data
Authors: Martin Audrey , Owende Philip , Ward Shane , O'Mahony Micheal
Published: April 2024

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.
Neutrality of Forestry Income Taxation and Inheritable Tax Exemptions for Timber Capital
Authors: Uusivuori Jussi
Published: April 2024

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.
Using Numerical Optimization for Specifying Individual-Tree Competition Models
Authors: Miina Jari , Pukkala Timo
Published: April 2024

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 koraiensis) Management for Both Timber and Commercial Seeds
Authors: Li Chuan-Zhong , Löfgren KarI-Gustaf
Published: April 2024

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.
Fostering the Production of Nontimber Services Among Forest Owners with Heterogeneous Objectives
Authors: Kline Jeffrey D. , Alig Ralph J. , Johnson Rebecca L.
Published: April 2024

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.
Trigonometric Variable-Form Taper Equations for Australian Eucalypts
Authors: Bi Huiquan
Published: April 2024

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.
Genotypic Stability and Genetic Parameters for Growth and Biomass Traits in a Water × Temperature Factorial Experiment with Pinus sylvestris L. Seedlings
Authors: Sonesson Johan , Eriksson Gösta
Published: April 2024

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 × temperature and family × temperature × water regime interactions. Family × water regime interaction and family effects were not significant. The results indicate low adaptation to water availability and a higher adaptation to different temperatures in the two Swedish Pinus sylvestris populations. If we assume that our results hold for a large part of the rotation the G × E interactions imply that climate change can alter the ranking of clones in a breeding program and thus decrease genetic gain. Studies of family ecovalence values showed that a minority of families (4–31%) contributed significantly to the interactions. Selection for stability could be a possible way to reduce the negative effects of G × E interaction. FOR. SCI. 46(4):487–495.
Measuring the Performance Improvement of Taiwan Forests after Reorganization
Authors: Kao Chiang
Published: April 2024

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.
The Effects of Ozone on a Lower Slope Forest of the Great Smoky Mountain National Park: Simulations Linking an Individual Tree Model to a Stand Model
Authors: Weinstein D.A. , Gollands B. , Retzlaff W.A.
Published: April 2024

We used an individual tree physiology model, TREGRO, and a stand succession model, ZELIG, to extrapolate from the direct response of leaf photosynthesis to ozone exposure in individual plants to an estimate of the possible future ozone effects on a forest located in the Twin Creeks region in Great Smoky Mountains National Park (GSMNP). This forest is dominated by yellow-poplar (Liriodendron tulipifera L.). With TREGRO, we estimated whether the reduction in the supply of carbon caused by ozone exposure would prevent an individual tree from meeting its demands for carbon for growth. With ZELIG, we analyzed the effect that changes in individual tree growth have in altering the ability of trees to successfully compete during forest succession. Current ambient levels of ozone measured at mid-elevations on the west side of GSMNP were predicted to reduce the abundance of yellow-poplar by 10% over the next 100 yr. This reduction would accelerate declines that are expected because of natural successional change. An increase of ozone of 50% above current ambient conditions was predicted to decrease yellow-poplar abundance by 30%. A reduction of ozone to halfambient levels was insufficient to prevent yellow-poplar abundance decreases. Increases in abundance in two other canopy dominants, red maple (Acer rubrum L.) and black cherry (Prunus serotina Ehrh.) were predicted from the release from competition as yellow-poplar was suppressed by ozone exposure. These increases, however, were predicted to be short-lived, with large decreases of up to 30% eventually occurring for both species. Overall basal area of the forest was predicted to be relatively unchanged by ozone exposure. FOR. Sci. 47(1)29–42.
Estimation of Mean Annual Temperature from Leaf and Wood Physiognomy
Authors: Wiemann Michael C. , Dilcher David L. , Manchester Steven R.
Published: April 2024

There are distinct relationships among the anatomy of wood, the morphology of leaves, and the climate in which woody plants are growing. The relationships between leaf morphological characters and climate have been known for many years, but wood characters as climate indicators are less well studied. In this article, we use measurements of wood anatomy and leaf morphology from woody dicotyledonous plants, growing in Florida and Connecticut, to determine the accuracy to which statistical models can predict climate. The strength of the relationship between climate and physiognomy is important because it allows us to evaluate the phenotypic plasticity that woody plants express under various climates. In this study we use canonical correspondence and regression models to examine how precisely wood anatomical and leaf morphological characters are related to climate. For leaves, canonical correspondence analysis (CCA) using 31 characters gave the closest estimate of mean annual temperature (MAT) in Connecticut, whereas a regression equation using only a single leaf character (leaf margins with no teeth) as predictor gave the closest estimate in Florida. For wood, CCA using 13 wood characters gave the closest estimate in Florida, whereas a regression equation using only a single wood character (the occurrence of vessels smaller than 100 μm) gave the closest estimate in Connecticut. CCA showed that, although MAT has a smooth and continuous relationship with leaf physiognomy, this is not the case for wood. Temperate woods form a different physiognomic population than subtropical and tropical woods, in which the physiognomy of temperate woods is more strongly influenced by MAT than is the physiognomy of subtropical and tropical woods. FOR. SCI. 47(2):141–149.
Designing an Evolution Program for Solving Integer Forest Management Scheduling Models: An Application in Portugal
Authors: Falcão André O. , Borges José G.
Published: April 2024

In this article, basic concepts of both genetic algorithms and evolution program design are presented. An evolution program is presented to solve a Model I harvest scheduling problem with 0-1 decision variables for the management alternatives for each stand, with annual constraints on harvested volume. An appropriate data structure (i.e., chromosome representation) is presented, as well as modified selection, crossover, and mutation strategies specially designed for application to large forest scheduling problems. Emphasis is on designing an efficient evolution program to address the complexity of large integer problem model solving and to provide both strategic and operational guidance to forest managers. A new stopping criterion for this iterative heuristic based on the asymptotic behavior of the evolution process is further presented. The new evolution program is applied to a two-product timber harvest scheduling problem in Portugal with a temporal horizon extending to seventy 1 yr periods. Results from 50 test computer runs are discussed for application to this large problem encompassing approximately 122,000 binary integer variables and 1,000 constraints. Statistic analysis of the convergence process suggests that the evolution program may seek optimal solutions at reasonable computational cost. Results thus suggest that evolutionary techniques may be used to confront the complexity of integer forest management scheduling model solving. FOR. SCI. 47(2):158–168.
Using the Branch and Bound Algorithm to Solve Forest Planning Problems with Adjacency Constraints
Authors: McDill Marc E. , Braze Janis
Published: April 2024

This article describes an assessment of the branch and bound algorithm (BBA) for solving forest management planning problems with adjacency constraints. Four questions are addressed: (1) What are the current limits of off-the-shelf optimization software implementing the BBA in terms of types and sizes of problems that can be solved within a reasonable time? (2) To what degree can larger problems be solved if the solution tolerance gap is increased from the default 0.01%? (3) How much can solution times be reduced by increasing the tolerance gap? and (4) If the algorithm is stopped at a larger tolerance gap, how large is the true gap likely to be? To address these questions, 2,676 hypothetical, spatially explicit forest management problems with three planning periods and between 50 and 2,500 management units were created and then solved with CPLEX® Version 6.5 to tolerance gaps of 0.01%, 0.1%, 1%, or 2%. For forests with immature or regulated age–class distributions, the predicted average solution time to a tolerance gap of 0.01% was 7.6 and 17.4 min, respectively, for problems with 2,500 management units—the largest problems solved in this study. For overmature and old-growth forest problems, predicted average solution times to a 0.01% tolerance gap reached 4 hr at about 640 and 213 management units, respectively. Increasing the tolerance gap to 1% increased these limits to 1,420 and 235 units, respectively. Increasing the tolerance gap to 1% reduced solution times by at least 90% in 49% of the overmature forest cases and in 53% of the old-growth forest cases. In overmature and old-growth forest problems, the true gap averaged 0.28% and 0.41%, respectively, when the reported gap was 1%. For. Sci. 47(3):403–418.
The Effects of Legal Limits and Recommendations on Timber Production: The Case of Finland
Authors: Hyytiäinen Kari , Tahvonen Olli
Published: April 2024

One form of legislative regulation on private forestry does not allow a stand to be clearcut until it exceeds a certain average diameter or age. This study examines whether this type of regulation used in Finland, for example, constrains the optimal timber harvesting of various site types of Norway spruce and Scots pine cultures. Applying a Faustmann type of rotation model, well-established growth and yield data and economic time series, we find that the regulations constrain the optimal solution if the rate of interest exceeds 3% or 5% for Scots pine and Norway spruce stands, respectively. They turn out to be more binding, the lower the growth capacity of the stand. Especially for mature stands, the regulations may cause major economic losses. The regulations increase long-term sawlog production but decrease pulpwood production in comparison to the unconstrained optimum. Moreover, the regulations change the structure and reduce the level of costs, and may then reduce working opportunities in forestry. FOR. SCI. 47(4):443–454.
Combining Forest-Level Analysis with Options Valuation Approach—A New Framework for Assessing Forestry Investment
Authors: Yin Runsheng
Published: April 2024

The conventional forest investment assessment at the stand level has difficulty dealing with multiple decisions and capturing the operational flexibility involved in timber production. By combining forest-level analysis with the options valuation approach, this article suggests a new framework for forestry investment assessment. We first articulate the new framework and discuss a few technical issues encountered in adopting it. Then, we present three empirical examples (entry decision, land acquisition, and harvest timing) to illustrate how forest-level analysis and/or real options valuation can be done and what we may learn from this type of exercise. We believe that while adopting this new framework entails challenges, it represents a great opportunity to expand the field of forest investment assessment. FOR. SCI. 47(4):475–483.
Impacts on Economically Optimal Timber Rotations When Future Land Use Changes
Authors: Klemperer W. David , Farkas Daniel R.
Published: April 2024

Based on a perpetual rotation assumption, changes in selected variables will have effects on the even-aged timber clearcut age (rotation) that maximizes net present value using the Faustmann formula. Alternatively, one can assume that landowners project a postharvest change in land use with a land value equal to or exceeding today's Faustmann value and that this future land value is independent of their assumed values for variables like annual costs, annual revenues, stumpage prices, and income taxes. In that case, the impact of changes in the foregoing variables on optimal rotations may be substantially greater, and sometimes in the opposite direction, compared to the standard Faustmann approach. Moreover, a higher estimated postharvest land value can shorten the optimal rotation. With a loblolly pine yield function, these rotation differences are demonstrated, using the standard, perpetual Faustmann formula and a rotation-end land use change adaptation with a fixed projected land value. Appendixes include mathematical verifications. The different interpretations depend on whether one considers the Faustmann land value as the land market value in a general equilibrium sense, or whether one takes the future market value of land as given and performs sensitivity analyses of alternative scenarios. Policy implications are difficult to assess without more research on landowner behavior. FOR. SCI. 47(4):520–525.