bluuebunny/crossref_metadata_2025 huggingface dataset:
Wood Relative Density Development in Red Pine (Pinus resinosa Ait.) Stands as Affected by Different Initial Spacings
Authors: Larocque Guy R. , Marshall Peter L.
Published: April 2024

The relationship between wood relative density and growth rate in red pine (Pinus resinosa Ait.) trees originating from different initial spacings was examined. Wood relative density was also related to crown development, as affected by competition. At young ages, the relative densities of entire rings and of the earlywood and latewood zones and the percentages of earlywood within the rings did not differ much among the spacings. As stands grew older, however, ring relative density and earlywood and latewood relative densities increased while the percentage of earlywood decreased. The closer the spacing, the faster relative density increased and the percentage of earlywood decreased. These changes closely followed changes in crown ratio. A good fit was obtained for an equation relating ring relative density to age and percentage of latewood for trees of various ages originating from a wide range of initial spacings. Ring width, ring relative density, and percentage of earlywood were regressed against (1) crown width and distance between the base of the crown and breast height and (2) crown volume and crown ratio. These equations did not fit well at young ages. However, the strength of the relationships improved with age, which indicated the increasing influence of crown development on wood density. For. Sci. 41(4):709-728.
Long-Term Structural Change in Uneven-Aged Northern Hardwoods
Authors: Leak William B.
Published: April 2024

The diameter distributions of 10 previously unmanaged northern hardwood stands on the Bartlett Experimental Forest in New Hampshire were analyzed to determine changes over a 35 yr period since a single cutting by the diameter-limit or single-tree selection methods. The diameter distribution of an uncut old-growth stand (the Bowl) provided a comparison. The cuttings left residual basal areas of 25 to 96 ft² of basal area per acre (5.7 to 22.0 m²/ha), as well as a wide range in diameter distribution. Basal area of the old-growth stand was 123 ft²/ac (28.2 m²/ha), and the diameter distribution was reverse J-shaped (negative exponential) as evidenced by a close fit (adjusted r² = 0.97) of log (no. of trees) over dbh class; the q (ratio between numbers of trees in successive 2 in. dbh classes) equaled 1.39. Under all cutting methods, the diameter distributions after 35 yr fit the reverse J-shaped form only moderately well with adjusted r²'s of 0.81 to 0.95. An equal or better fit in most cases (adjusted r²'s of 0.91 to 0.98) was provided by log (no. of trees) over dbh², which reflects the tendency of the quotients between numbers of trees per dbh class to increase with dbh. None of the initial diameter distributions of the cut stands had rotated sigmoid characteristics, but five of the final diameter distributions had significant rotated sigmoid characteristics, and at least two others showed graphical sigmoid tendencies. Apparently, rotated sigmoid characteristics are caused by disturbance, perhaps coupled with successional trends toward increased tolerant softwoods. For. Sci. 42(2):160-165.
An Analysis of the Impacts of Public Timber Harvest Policies on Private Forest Management in the United States
Authors: Adams Darius M. , Alig Ralph J. , McCarl Bruce A. , Callaway J. M. , Winnett Steven M.
Published: April 2024

Past studies of the impacts of changes in public timber harvest have commonly assumed that the extent and intensity of private forest management would remain unchanged in the face of shifting log prices and demand. This study reexamines the issue of public harvest impacts using a model of intertemporal log markets in which prices, private harvests, and timber management investment are endogenous. The model considers two classes of private owners in nine regions and subdivides the basic timber inventory into a large number of classes that influence yields and costs, including, site quality, species group, and past management. Six product groups are recognized with opportunities for substitution. Given the perfect market and foresight structure of the model, simulation results suggest a far more elastic market response to changes in public cut than found in past studies. Shifts in intertemporal patterns of private investment act to reduce the price and aggregate harvest impacts of public cut changes over time. Underlying these moderated market impacts, however, are larger interregional shifts in harvest and private owner welfare than suggested in earlier analyses. Through changing management investment, including conversion of lands from hardwood to softwood species types, some of the largest economic and biological/ecological impacts may be realized outside of the regions in which public forestlands are concentrated. For. Sci. 42(3):343-358.
Prediction of Gross Tree Volume Using Regression Models with Non-Normal Error Distributions
Authors: Williams Michael S. , Schreuder Hans T.
Published: April 2024

In developing new clones of forest trees, the first main goal is to propagate enough plantable plants for clonal field trials and a clonal archive. Models of clonal multiplication rates in Eucalyptus globulus indicate that this takes a similar time (about 56 wk) from the sowing of seed, whether multiplication is by axillary shoot culture in vitro or by stem cuttings propagation. Multiplication of unrooted shoots is relatively rapid in vitro but is largely offset by the greater time required for weaning, pricking out, and growth in the nursery. For. Sci. 42(4):415-418.
Predictive Posterior Distributions from a Bayesian Version of a Slash Pine Yield Model
Authors: Green Edwin J. , Strawderman William E.
Published: April 2024

We formulate a traditional slash pine diameter distribution yield model in a Bayesian framework. We attempt to introduce as few new assumptions as possible. We generate predictive posterior samples for a number of stand variables using the Gibbs sampler. The means of the samples agree well with the predictions from the published model. In addition, our model delivers distributions of outcomes, from which it is easy to establish measures of uncertainty, e.g., Bayesian credible regions. For. Sci. 42(4):456-464.
Long-Run Timber Supply and the Economics of Timber Production
Authors: Yin Runsheng , Newman David H.
Published: April 2024

The analysis of long-run timber supply is hampered by the lack of a well-defined profit function. Such a function provides the foundation for deriving a theoretically consistent supply equation. Some recent studies have attempted to obtain a timber supply equation by manipulating the stand-level Faustmann model. As a result of inappropriate approaches and assumptions, their conclusions may be false. In this article, we build on the Faustmann-Smith-Samuelson model first developed by Comolli (1981) to examine aggregate timber production. We show this model to have the desired properties of a profit function that allows us to test various issues. It is then found that the general beliefs of negatively sloped per-land-unit supply curves and positively sloped aggregate supply curve are robust. Finally, we present several applications and implications of our modeling approach. For. Sci 43(1):113-120.
Stochastic Models for Conifer Tree Crown Profiles
Authors: Biging Gregory S. , Gill Samantha J.
Published: April 2024

We perform a feasibility study of using stochastic models to describe the profile of tree crowns and to capture the stochastic nature of the tree crown form for five conifer species of the Sierra Nevada. In 70% of the cases investigated we found that we could model tree crown profiles as a quadratic or cubic trend in conjunction with a simple autoregressive moving average model (ARMA). In the remaining cases we used a quadratic or cubic trend in conjunction with white noise. These stochastic ARMA models are visually and statistically an improvement over using Euclidean geometric crown profile models. Competing models were judged by using Akaike's Information Criterion (AIC) to achieve a parsimonious model. It was found that first-order moving average MA(1) models or first-order autoregressive AR(1) models were adequate for modeling the majority of the cases studied and that these models were qualitatively similar. MA(1) models were preferred over the AR(1) models because less information is required to simulate them. For. Sci. 43(1):25-34.
Leaf Area-Productivity Relationships Among Mixed-Species Hardwood Forest Communities of the Central Hardwood Region
Authors: Jose Shibu , Gillespie Andrew R.
Published: April 2024

A study was conducted to quantify the influence of environmental factors on the leaf area-productivity relationships of Ecological Land Type Phases (ELTPs) representing Central Hardwood forest communities. Forest inventory data were collected from 83 plots taken along a moisture gradient, stratified within recognized ELTPs in the Hoosier National Forest in southern Indiana. Density (standing basal area, volume, and biomass), annual production, leaf area index (LAI), and water balance indices were determined for each ELTP. Ecological Land Type Phases showed marked differences in density and growth measures which were positively correlated with leaf area index. Leaf area index, in turn, exhibited strong correlations with site and environmental factors. Further, a reduction in canopy-average specific leaf area with decreasing soil moisture and LAI was observed. In general, maximum growth efficiency (measured as growth per unit of LAI) was attained at a LAI of approximately 3.5, after which it decreased. However, no significant differences in growth efficiency were found among ELTPs, suggesting that the communities were adjusting to differences in resource availability, particularly water. Thus, these mixed-species forest communities adjust both species composition and canopy morphology to compensate for changing environmental gradients. For. Sci. 43(1):56-64.
Effects of Constitutive and Inducible Traits of Hybrid Poplars on Forest Tent Caterpillar Feeding and Population Ecology
Authors: Robison Daniel J. , Raffa Kenneth F.
Published: April 2024

Hybrid Populus spp. clones, differentially affected forest tent caterpillar, Malacosoma disstria, behavior, development, and population dynamics. Increased larval cohort size and larval silk generally enhanced development. Larval behavior affected developmental success. Under choice conditions, larvae selected more suitable clones, and their growth was enhanced when they moved from less to more suitable hosts. Herbivory by the forest tent caterpillar caused significant reductions in the quality of foliage for subsequent larval development. Polar and nonpolar foliar extracts varied between constitutive and previously damaged plants, and elicited significant larval behavioral responses. The extent to which prior feeding induced foliar changes that affected larval feeding and development varied among clones. The ability of forest tent caterpillar to exploit clones includes genetic and environmental components affecting foliar quality, and includes positive and negative density dependent feedback. In whole-tree field cages, forest tent caterpillar populations increased 9.7x during a 2 yr period on a highly suitable clone, and declined 2.7x on a poor quality clone. The relationships between clonal suitability and forest tent caterpillar population growth were strongly influenced by bud phenology and exudates, in addition to foliar traits. For. Sci. 43(2):252-267.
Growth, Development, and Yield in Pure and Mixed Stands of Eucalyptus and Albizia
Authors: Debell Dean S. , Cole Thomas G. , Whitesell Craig D.
Published: April 2024

Productivity of Eucalyptus saligna Sm. plantations is commonly limited by low levels of available nitrogen (N), and synthetic N fertilizer applications are costly and sometimes impractical; thus, we evaluated mixed species plantings in which N is added by Albizia falcataria (L.) Fosberg [=Paraserianthes falcataria (L.) Nielson]. Five ratios of Eucalyptus and Albizia were compared with each other, with pure Albizia, and with pure Eucalyptus fertilized periodically with N in a randomized block design on the wet Hamakua coast of the Island of Hawaii. Eucalyptus growth increased as the amount of Albizia in the stand increased from 11 to 66%, and heights and diameters of Eucalyptus in stands containing 34% or more Albizia were equal to or larger than those in fertilized, pure stands. Total aboveground biomass, stem biomass, and stem volume per ha of mixed stands at age 10 were at least equal to yields produced in fertilized, pure Eucalyptus stands; total biomass of mixed stands with 50 or 66% Albizia was 30 and 46% greater than that in fertilized, pure Eucalyptus and 10 and 24% greater than that of pure Albizia. Yield of the Eucalyptus component alone in these two mixtures was at least equal to that of fertilized, pure Eucalyptus stands. Moreover, mean annual increment declined more slowly after culmination in all-mixed stands than in the fertilized, pure Eucalyptus stand. Over time, the apparent benefits of mixed versus pure plantings of Eucalyptus and Albizia have increased, and at age 10 include diversity in stand structure (and habitat) as well as the improvements in Eucalyptus tree growth and stand productivity recognized at younger ages. For. Sci. 43(2):286-298.
Constraining Individual Tree Diameter Increment and Survival Models for Loblolly Pine Plantations
Authors: Zhang Shaoang , Amateis Ralph L. , Burkhart Harold E.
Published: April 2024

Among extant forest growth and yield models, individual tree growth models provide the most detailed information, which is useful for intensive forest management. However, individual tree growth models may be inaccurate for stand-level predictions because of the cumulative error resulting from individual tree predictions. This paper is aimed at developing a method to ensure that individual tree growth models not only provide precise individual tree predictions but also give precise stand-level estimation. Based on the conceptual relationships between basal area of each diameter class and the diameter increment of trees in the same diameter class, a constrained regression equation system is proposed. The same approach is also applied to modeling individual tree survival probability. An algorithm for estimating multiresponse regressions was developed. Results using data from unthinned loblolly pine (Pinus taeda L.) plantations show that the simultaneous equation system provides nearly the same individual tree diameter increment estimates as the unconstrained model but better estimates for basal area of each diameter class and for total stand basal area. The potential for improving stand mortality estimation with a constrained individual tree survival model where there is little mortality in the data is limited. For. Sci. 43(3):414-423.
Relationship Between Volatile Foliar Terpenes and Resistance of Sitka Spruce to the White Pine Weevil
Authors: Tomlin Elizabeth S. , Borden John H. , Pierce Harold D.
Published: April 2024

Volatile foliar terpenes were compared both quantitatively and qualitatively among 20 provenances and 11 cloned genotypes of Sitka spruce (Picea sitchensis Bong [Carr.]) that had been classified as resistant or susceptible to the white pine weevil (Pissodes strobi [Peck]). On average, trees in resistant provenances had significantly lower content of ten terpenes than in susceptible provenances. One resistant clone had significantly higher foliar terpene content, and four resistant clones had significantly lower content than susceptible trees. Thus clonal resistance could be expressed respectively by repellency or lack of apparency. Canonical discriminant analysis revealed that several resistant clones, particularly from the Haney provenance, could be distinguished from others on the basis of their terpene profiles. While there was no clear relationship between terpene profile and resistance, these results suggest that there are probably multiple resistant "chemotypes," and that volatile foliar terpenes may be useful in identifying potentially resistant trees. For. Sci. 43(4):501-508.
Analyzing Uncertainties in Experts' Opinions of Forest Plan Performance
Authors: Alho Juha M. , Kangas Jyrki
Published: April 2024

Multi-objective forestry requires new decision support systems to aid the forest owner and foresters in the planning of future treatment schedules. The analytic hierarchy process (AHP), based on pairwise comparison data and Saaty's eigenvector method, is one technique that has been proposed to make such qualitatively different objectives as income from timber sales and scenic beauty of forest landscape commensurable. A weak point of the methodology has been the lack of a statistical theory behind it. We have earlier shown how classical regression techniques can be used to provide a statistical assessment of the uncertainty of the estimated ratio-scales. In this paper we extend the results to a multi-level decision hierarchy commonly used in forest planning. We also provide a Bayesian extension of the regression technique. The advantage of the Bayesian approach is that it provides summaries of expert views that are easily understood by decision makers who may not have extensive understanding of statistical concepts. On the basis of the Bayesian analysis, one can calculate, for example, how likely it is that (in the view of the expert) a given forest plan is better than any other plan being compared. For. Sci. 43(4):521-528.
Reconstructing the Spatial Pattern of Trees from Routine Stand Examination Measurements
Authors: Hanus Mark L. , Hann David W. , Marshall David D.
Published: April 2024

Reconstruction of the spatial pattern of trees is important for the accurate visual display of unmapped stands. The proposed process for generating the spatial pattern is a nonsimple sequential inhibition process, with the inhibition zone proportionate to the scaled maximum crown width of an open-grown tree of the same species and same diameter at breast height as the subject tree. The results of this coordinate generation procedure are compared with mapped stem data from nine natural stands of Douglas-fir at two ages by the use of a transformed Ripley's K(d) function. The results of this comparison indicate that the proposed method, based on complete tree lists, successfully replicated the spatial patterns of the trees in all nine stands at both ages and over the range of distances examined. On the basis of these findings and the procedure's ability to model effects through time, the nonsimple sequential inhibition process has been chosen to generate tree coordinates in the VIZ4ST computer program for displaying forest stand structure in naturally regenerated young Douglas-fir stands. For. Sci. 44(1):125-133.
Bayesian Analysis of the Linear Model with Heterogeneous Variance
Authors: Green Edwin J. , Valentine Harry T.
Published: April 2024

Linear models are among the most common statistical tools in forestry, and indeed in all science. It is widely known that when linear models are applied to attributes of size (e.g., individual tree volumes), the conditional variance may be heterogeneous. Under these circumstances, the usual least squares estimator remains consistent, but is no longer efficient. This has been appreciated in forestry for some time, and various solutions have been recommended over the years. In this paper, we propose a Bayesian solution. Bayesians would prefer this method to previous solutions for many reasons. However, even non-Bayesians may wish to consider the method as it yields (as will be shown) solutions quite close to the maximum likelihood solution, along with the marginal posterior distribution of each parameter. For. Sci. 44(1):134-138.
Long-Term Trends in Height Growth of Jack Pine in North Central Ontario
Authors: Goelz J.C. G. , Burk T. E.
Published: April 2024

Although most investigations of long-term growth trends of trees involve description of radial growth of trees, investigation of height growth of dominant and codominant trees also warrants attention for two significant reasons--the dependent variable is largely independent of stand density and it represents an index of stand productivity. Residuals from a height growth equation for jack pine (Pinus banksiana Lamb.) were used to examine long-term trends in height growth. No consistent long-term trend was apparent; however, a period of superior growth was identified during the 1960s. Short-term changes in climatic variables could account for a short duration of increased growth. As anthropogenic factors, such as air pollution, did not exhibit a trend coincident with the growth trend, they do not represent a reasonable explanation. An additional benefit of detailed examination of trends in residuals is the ability to uncover misidentification of models. The examination may suggest an inappropriate form for the equation was used, or may suggest that important variables are missing from the model. For. Sci. 44(1):158-164.
The Law of One Price in United Kingdom Soft Sawnwood Imports--A Cointegration Approach
Authors: Hänninen Riitta H.
Published: April 2024

The law of one price states that prices of homogenous commodities, defined in a common currency, are equal throughout the world. It implies cointegration of prices. In the present study, the law was tested for imports of soft sawnwood to the United Kingdom from Finland, Sweden, Canada, and Russia using the concept of cointegration. The data are quarterly and cover the period 1978-1992. The study used the multivariate cointegration method of Johansen instead of the bivariate method commonly used in earlier studies. The existence of the law was tested simultaneously for all four import prices and separately for pairs of prices. The results do not support the "law" but instead indicate the existence of differences over the long run between different suppliers' sawnwood prices. This suggests that imperfect competition models should be used in explaining and forecasting UK sawnwood imports. The results also raise an important issue concerning testing for competition in forest products markets, which is not usually done in connection with the modeling of markets. For. Sci. 44(1):17-23.
Modeling Timber Harvest Scheduling Problems with Multiple Criteria: An Application in Spain
Authors: Díaz-Balteiro Luis , Romero Carlos
Published: April 2024

This paper presents a multicriteria procedure for forest planning problems. The basic ingredients of this procedure are multigoal programming, compromise programming, and results connecting the best-compromise solutions with the concept of utility optima. The main feature of the procedure lies in the easy and transparent utility interpretation of some single best-compromise solutions even when the utility function, as is usual in a forestry context, is virtually unknown. The theoretical developments are applied to a timber harvest scheduling problem in Spain. The criteria considered are: (a) the net present value of the forest over the planning horizon, (b) the equality of harvest volume in each cutting period, (c) the area control criterion which looks for an ending regulated or even-aged forest, and (d) the ending inventory restraint. The preferential weights incorporated into the models are derived from the application of the Analytical Hierarchy Process (AHP) method to a group of experts in forestry matters. Several utility formulations are tested: (1) a separable and additive utility function linear in each criterion (i.e., a compromise solution for metric 1); (2) a Rawlsian utility function where the maximum deviation is minimized (i.e., a compromise solution for metric ∞) and (3) a family of quasi-Rawlsian utility functions. For. Sci. 44(1):47-57.
Influence of Plant Density and Soil Organic Matter on the First-Year Growth of Loblolly Pine and Sweetgum
Authors: Zutter Bruce R. , Glover Glenn R. , Mitchell Robert J.
Published: April 2024

Loblolly pine (Pinus taeda L.) and sweetgum (Liquidambar styraciflua L.) seedlings were planted at a range of densities on a formerly cultivated field which varied in soil organic matter (soil OM) in the upper 15 cm of the soil. Mean aboveground biomass per plant at the end of one growing season was examined to see how it varied as a function of plant density and soil OM. Biomass per plant as a function of density, holding soil OM constant, was described well by a reparameterized form of a standard yield density equation. A simple linear equation suitably described per plant biomass as a function of soil OM, holding density constant. Effects of soil OM on biomass were positive for both species, with sweetgum exhibiting a stronger response than loblolly pine. Based on the results of fitting equations to single factors, an equation considering both density and soil OM was developed and fitted using all data for each species. The equations explained 85% of the variation in response for both species. The inclusion of soil OM was more important in describing response of sweetgum than for loblolly pine. Inclusion of both density and soil OM in a single equation to describe mean response of plants in a monoculture might be extended to a mixture of species and used to examine intraspecific and interspecific competitive effects of competition and their relationship with productivity. For. Sci. 44(3):397-404.
Standard Errors of Area Estimates Obtained by Traversing and GPS
Authors: Bondesson Lennart , Ståhl Göran , Holm Sören
Published: April 2024

In this article, the problem of determining standard errors of area estimates obtained by traversing is addressed. In traversing, a surveyor moves along the boundary of a compartment and makes measurements at certain base points to determine their coordinates. Two cases of traversing are described: the case when coordinates are determined directly using GPS equipment and the case when distances and directions are measured from every base point to the next. It is shown that the problem of determining standard errors of the area estimates is different for the two cases. Formulas are derived from basic assumptions about the measurement errors. The efficiency of the two approaches is compared. It is found that the standard errors for the two methods often are of a similar magnitude but that the size and the shape of a compartment affect what method should be preferred. For. Sci. 44(3):405-413.
Crown Profile Modeling of Loblolly Pine by Nonparametric Regression Analysis
Authors: Doruska Paul F. , Mays James E.
Published: April 2024

Crown profile of loblolly pine (Pinus taeda L.) was modeled by nonparametric regression analysis. Nonparametric regression may be applicable when an underlying parametric model cannot be identified and uses only the data to fit a curve. A class of local-polynomial estimators which contains the popular kernel estimator as a special case was investigated. Kernel regression appears to fit closely to the interior data points but often possesses bias problems at the boundaries of the data, a feature less exhibited by local linear or local quadratic regression. A selection of trees was used to show that nonparametric regression captures more variation in crown shape than multiple linear regression. When using nonparametric regression, decisions must be made regarding polynomial order and bandwidth. Such decisions depend on the presence of local curvature, desired degree of smoothing, and for bandwidth in particular, the minimization of some global error criterion. In the present study, a penalized PRESS criterion (PRESS*) was selected as the global error criterion. For. Sci. 44(3):445-453.
Estimation of Temporal Variations in Historical Fire Frequency from Time-Since-Fire Map Data
Authors: Reed W. J. , Larsen C. P. S. , Johnson E. A. , MacDonald G. M.
Published: April 2024

This paper describes an improved statistical methodology for estimating historical forest fire frequencies from time-since-fire map data. Of particular interest is the question of estimating fire frequency in temporally distinct epochs. Unlike previous graphical and ad hoc methods, the new methodology is firmly grounded within the established statistical paradigm of likelihood inference. In addition, in contrast to earlier methods, it takes into account the fact that surviving stands which originated in earlier epochs, have been subject to different hazards of burning as they have lived through more recent epochs. Neglecting this fact leads to overestimates of the fire frequency in the more recent epochs. Procedures for obtaining maximum likelihood estimates and likelihood ratio confidence intervals for the fire frequency in each epoch are developed, along with a likelihood ratio test to assess whether the fire frequencies in distinct epochs were significantly different. This test is not strictly valid when the change points separating epochs are suggested from exploratory data analysis; rather it is developed assuming that change points are determined independently of the data. This distinction, which is necessary to avoid selection bias, has not been noted before. The fact that forest fire is a contagious process, with consequent spatial autocorrelation in time-since-fire observations, is taken into account through the use of an overdispersed model, with associated quasi-likelihood function. This aspect has been ignored, by and large, in previous analyses which have implicitly assumed independence of observations. An example is given in which the method is applied to published fire history data from the Kananaskis Valley. The results indicate that the previous analysis overestimated the fire frequency for the most recent epoch. The conclusions of other studies concerning temporal changes in fire frequency may need to be reconsidered. For. Sci. 44(3):465-475.
Comparative Susceptibility of Conifers to Larch Dwarf Mistletoe in the Pacific Northwest
Authors: Mathiasen Robert L.
Published: April 2024

A total of 62 mixed conifer sites in Idaho, Montana, Oregon, and Washington infested with larch dwarf mistletoe (Arceuthobium laricis) were sampled to compare host susceptibility to this parasitic flowering plant. Temporary circular plots (6 m radius) were established around dominant, severely infected, principal, and secondary hosts. Within plots, species, diameter at 1.37 m above the ground, and dwarf mistletoe rating (6 class system) were determined for each live tree over 1.37 m in height. A total of 11,270 trees were sampled in 620 plots. Based on the percentage of infection, species were assigned to host susceptibility classes: western larch is the only principal host of larch dwarf mistletoe; mountain hemlock and lodgepole pine are secondary hosts; subalpine fir and ponderosa pine are occasional hosts; and Engelmann spruce, grand fir, and western white pine are rare hosts. No infection was observed on Douglas-fir, western hemlock or western redcedar. However, based on a report of larch dwarf mistletoe parasitizing western hemlock in Washington, western hemlock must be designated as a rare host. Pacific silver fir and whitebark pine are tentatively classified as occasional hosts. For. Sci. 44(4):559-568.
Economic and Fragmentation Effects of Clearcut Restrictions
Authors: Barrett T.M. , Gilless J.K. , Davis L.S.
Published: April 2024

Clearcut restrictions limiting individual clearcut size affect economic outputs and alter the spatial distribution of wildlife habitat over the landscape. Simulations of different clearcutting restrictions were applied to a 47,500 ha mixed-ownership landscape in the Sierra Nevada of California. The private owner was assumed to pursue a goal of maximizing net present value (NPV), while the public owner was assumed to use a combination of low-intensity selection harvesting and long rotations to develop late-seral habitat. With a 10 yr exclusion period, maximum clearcut size limits of 4 and 32 ha reduced the private owner's NPV to 79% and 91% of the unconstrained maximum, respectively; with a 20 yr exclusion period, to 65% and 88% of the unconstrained maximum. Initially, smaller clearcut size limits resulted in more mature forest [average stand diameter (ASD) greater than 30 cm], but with greater fragmentation. Ultimately, late-seral habitat (ASD > 61 cm) was insensitive to clearcut size limits because rotation lengths of 60 or 90 yr did not produce that habitat class for most forest types. For. Sci. 44(4):569-577.
Effects of Thinning and Nitrogen Fertilization on Sugars and Terpenes in Douglas-Fir Vascular Tissues: Implications for Black Bear Foraging
Authors: Kimball Bruce A. , Turnblom Eric C. , Nolte Dale L. , Griffin Doreen L. , Engeman Richard M.
Published: April 2024

The chemical constituents of coniferous vascular tissues play a role in bear forage selection. In particular, bear foraging preferences are related to the concentrations of simple sugars (nonstructural carbohydrates) and terpenes in the forage. Analyses of vascular tissue samples from trees collected in test plots indicated that both thinning and fertilization caused the sugar concentration of vascular tissues in the lower bole to increase. However, these treatments had no effect on the concentrations of hydrocarbon monoterpenes, oxygenated monoterpenes, or sesquiterpenes. These results may explain the observations that black bears prefer to forage in thinned and fertilized stands. For. Sci. 44(4):599-602.
Measuring Environmental Quality in the Southern Appalachian Mountains
Authors: Pendleton Linwood , Sohngen Brent , Mendelsohn Robert , Holmes Thomas
Published: April 2024

This study presents a method for valuing recreational environmental quality in the forests of the southeastern United States. The paper offers a method for choosing, measuring, and valuing forest attributes. Surveys and popular recreation literature are used to identify forest attributes that contribute to recreational quality. Standard ecological techniques are employed to measure levels of these attributes along trails in Tennessee, North Carolina, and Georgia. Finally, the paper demonstrates how hedonic methods can be used to assign values to forest attributes. We show that values for recreational quality vary across users and sites. Furthermore, we demonstrate the existence of negative marginal values for certain forest attributes and provide evidence that suggests these negative values are not the result of mis-specification, but are consistent with oversatiation. For. Sci. 44(4):603-609.
A Methodology to Analyze Divergent Case Studies of Non-Timber Forest Products and Their Development Potential
Authors: Pérez Manuel Ruiz , Byron Neil
Published: April 2024

Debate currently rages over the development potential of Non-Timber Forest Products (NTFP) in tropical forests. Proponents of particular "solutions" can refer to evidence (case studies, data) which tend to support their interpretation of events and relationships. Recommendations thus frequently depend on how data are classified and interpreted. Inaccurate or incomplete classification leads to defective subsequent theories, models, and recommendations. We present a method for classifying very divergent case-study data, and some initial results as a basis for general understanding of key factors that influence a given result. Crucial issues determining outcomes of NTFP development include the nature of government involvement, distribution of property rights, the ability of local people to claim and enforce such rights, market transparency, and pressure on the resource. This paper concludes with suggestions for further testing and development of the methodology. For. Sci. 45(1):1-14.
Spatial Restrictions in Harvest Scheduling
Authors: Murray Alan T.
Published: April 2024

Forest resource use has traditionally been multifaceted. In order to ensure that these resources continue to be available for use by current and future generations, sustainable management practices are essential for striking a balance between the varied and often competing demands associated with forest use. This has meant that analysis incorporate specific objectives and considerations aimed at minimizing the impacts of forest activities. One such management planning approach has been the inclusion of spatial restrictions in harvest scheduling analysis. This article reviews two basic harvest scheduling models which may be used for imposing spatial restrictions. Distinctions between the alternative methods are highlighted and operational considerations are discussed. This article establishes and outlines priority areas for future harvest scheduling research. For. Sci. 45(1): 45-52.
Compatible Volume and Taper Models with Coefficients for Tropical Species on Hainan Island in Southern China
Authors: Fang Zixing , Bailey Robert L.
Published: April 2024

Compatibility of a volume-taper equation system is generally defined to mean that volumes determined by integrating the taper curve from groundline to total tree height are algebraically identical to those obtained from the total volume or appropriate volume ratio equations. This constraint was applied to a previously published model as a boundary condition using the constant of integration resulting from the solution of the differential equation. Four cases are discussed that apply to different solutions of the differential equation. This set of models, all based on the same geometric assumption, makes a very flexible system for modeling stem taper. We fitted the resulting taper models and corresponding tip volume equations simultaneously to stem-measurement data for 23 tropical species growing on Hainan Island in southern China. The simplest case among the four (case I-a) was acceptable for some species, but for some others, a more general case (case II-b) was needed. We compared the results for the simplest and the most general cases of this system with a published geometric model having only a point constraint at dbh and with a published variable exponent taper equation. We examined how well each one predicted upper-stem diameters, merchantable height for a given upper-stem diameter, and total stem volume. Our taper models always had the smallest bias and standard error of estimates for total volume estimation. The variable exponent taper equation was the best for predicting upper-stem diameter and merchantable height. The advantages of a taper system with a geometric rationale are discussed, and two examples of easy extensions of our taper model are shown in the appendix. For. Sci. 45(1):85-100.
Afforestation as a Real Option: Some Policy Implications
Authors: Thorsen Bo Jellesmark
Published: April 2024

The theory of real options is applied to the decision of establishing a new forest stand. Assuming that afforestation costs are known and constant and that future net prices of roundwood follow a Geometric Brownian Motion, a simple model of the decision problem is formulated. Using this model, a real option analysis of the afforestation opportunity is performed. Next, the implications of the real option approach for afforestation subsidy schemes are analyzed. It is found that the subsidies needed to induce a desired investment behavior will in general increase, and that the actual increment will depend on the way subsidies are offered to the landowners and affect their expectations. An empirical example is used to illustrate the potential significance of the findings. For. Sci. 45(2):171-178.
Combining a Decomposition Strategy with Dynamic Programming to Solve Spatially Constrained Forest Management Scheduling Problems
Authors: Borges José G. , Hoganson Howard M. , Rose Dietmar W.
Published: April 2024

A decomposition approach to solve the forest management scheduling adjacency problem is developed for application to large forests. Overlapping subproblems amenable to exact dynamic programming solution are solved sequentially. A heuristic is used to define and link subproblems such that near-optimal solutions to the master problem are obtained. Both the contrasting size and the irregular shape of stands complicate the problem of formulating the dynamic programming network. Subproblem size and the sequencing of stands for each corresponding dynamic programming network are defined simultaneously, as model size is especially sensitive to stand sequencing. Emphasis is on efficient dynamic programming formulations to allow for large subproblems. Results from over 100 test computer runs are discussed for applications to 3 large problems. Results suggest that the strategy can consistently produce near-optimal solutions at reasonable computational cost. A procedure is developed to derive three slightly different adjacency problems so that the optimal solution can be found. Results for applications to the modified problems show that the proposed heuristic's solutions were within 0.01, 0.04, and 0.01% of the optimal solution, respectively. The proposed solution method consistently outperformed two other heuristics that were applied. For. Sci. 45(1):201-212.
An Adjustable Predictor of Crown Profile for Stand-Grown Douglas-Fir Trees
Authors: Hann David W.
Published: April 2024

This study developed a method for predicting the crown profile of stand-grown trees that can be adjusted to other populations of the same species by using either measurements or predictions of the largest crown width (LCW) for trees in the alternative population. The method should be of particular interest for tree species such as Douglas-fir that have exhibited variation in crown attributes across both their geographic range and genotypes. To model crown profile, the crown was divided into two segments: the portion of the crown above the point where LCW occurs, and the portion below that point. The equation for the upper portion predicted a crown profile that ranged in shape from nearly conic to parabolic, depending on position within the crown and the social status of the tree, as indicated by the ratio of total height divided by diameter at breast height for the tree. The equation for the lower portion predicted a crown profile with a cylindrical shape. This method explained nearly 94% of the variation in crown width when used with the felled tree measurement of LCW, 87% with a measurement of LCW taken while the tree was standing, and 83% with the use of a value for LCW that was predicted from an equation developed from an independent data set. For. Sci. 45(2):217-225.
Considering Intergenerational Equity in Linear Programming-Based Forest Planning Models with MAXMIN Objective Functions
Authors: Church Roger , Daugherty P. J.
Published: April 2024

This paper describes alternative approaches to formulating linear-programming-based forest planning models. These approaches consider a form of equity between current and future generations, as represented by the periods in a planning horizon. Both nominal net revenue in each period and each period's present net worth with values discounted relative to each period, are used as criteria for welfare. The minimum present net worth or net revenue outcome obtained for the set of periods is maximized. The approaches are different. Using present net worth relative to each period as a criterion allows for a concern for economic efficiency and allows variation in net revenue. Using net revenue focuses on a more even distribution of net revenue between periods. The approaches are tested in a case study, and the results are compared to those from a standard approach of maximizing present net worth relative to the first period. The results suggest that the approaches could be useful in a forest planning context, either as an alternative to standard approaches or as a means of generating relevant information. For. Sci. 45(3):366-373.
Effects of an Intense Wildfire in a Mexican Oak-Pine Forest
Authors: Fulé Peter Z. , García-Arévalo Abel , Covington W. Wallace
Published: April 2024

An oak-pine forest burned by intense wildfire in April, 1996, and a companion unburned area were sampled 1 month and 1 yr postfire in La Michilía Biosphere Reserve, Durango, Mexico. Up to 90% of the trees were killed or top-killed in the burned area, but larger trees tended to survive, so basal area was only reduced by 66%. Top-killing was relatively higher among fire-susceptible oaks and lower among fire-resistant pines. However, oaks were strong resprouters both in the canopy and at the base of top-killed trees. Damage codes based on crown scorch and bole char were highly accurate when predicting that a tree would die but substantially overestimated survivors. Most tree regeneration was top-killed in the fire, but oak sprout density was 700% that of the unburned area by 1 yr postfire. Manzanita shrubs also resprouted vigorously. Herbaceous production and cover were lower after the first postfire growing season in the burned area than the unburned area. Woody fuels and forest floor depth were also reduced. Although short-term fire effects indicate that the forest ecosystem has moved closer toward a savanna condition, remnant seed trees and sprouting trees are expected to maintain forest cover. Future herbaceous production is likely to increase in response to overstory mortality. Quantification of fire effects is helpful for supporting short-term management decisions since oak-pine forests cover millions of hectares in northern Mexico. As a long-term management strategy, however, we suggest that restoring the frequent, low-intensity fire regime may be desirable for ecological and economic reasons. For. Sci. 46(1):52-61.
Optimizing Forest Stand Management with Natural Regeneration and Single-Tree Choice Variables
Authors: Hof John , Bevers Michael
Published: April 2024

This article addresses the any-aged forest management problem with individual trees as the choice variables in integer programming models. In order to sustain the forest using natural regeneration, spatial proximity of seed trees is required for harvesting to take place in these models. This problem requires integer variables to avoid harvesting part of a tree, but it is remarkably integer-friendly. Solvability of large models is thus explored, along with the patterns of solution that can be recognized in smaller models. Results from these exploratory models are sensitive to initial forest conditions and do not display the steady state conditions typically assumed for uneven-aged management in the literature. For. Sci. 46(2):168-175.
Effects of Correlation among Parameters on Prediction Quality of a Process-Based Forest Growth Model
Authors: Guan Biing T.
Published: April 2024

A nonparametric method was introduced as a technique for evaluating the effects of parameter correlation on prediction quality of process-based forest growth models. The method was based on a rank correlation and Cholesky decomposition. For a given data matrix, by reordering the observations, the method would produce a rearranged matrix with the desired correlation structure. The method was computationally simple and efficient. Using a process-based model calibrated for red pine (Pinus resinosa Ait.) as an example, small-scale Monte Carlo simulations revealed that parameter correlation had different effects on the model's prediction means and variances, depending on the importance of the parameters involved. In general, given the same level of correlation, correlation between two important parameters would have greater influences on prediction quality than correlation between two less important parameters. Parameter correlation slightly affected the prediction means but could significantly change prediction variances. The relationship between prediction quality and the degrees of correlation, however, was not necessarily a linear one. The same parameter correlation might also have different effects on different state variables. For. Sci. 46(2):269-276.