bluuebunny/crossref_metadata_2025 huggingface dataset:
Growth Responses of Abies amabilis Advance Regeneration to Overstory Removal, Nitrogen Fertilization and Release From Vaccinium Competition
Authors: Hawkins Barbara J. , Moran Jonathan A.
Published: April 2024

Abies amabilis advance regeneration may take several years to acclimate to overstory removal, and poor performance has been attributed to unfavorable microclimate, nutrient stress, and competition from ericaceous vegetation. Our objective was to examine potential factors limiting growth of advance regeneration of Abies amabilis on a montane site in coastal British Columbia. In 1996, 72 experimental plots were established at the Montane Alternative Silvicultural Systems site, Vancouver Island, to provide a design with 12 plots within each of 2 replicate blocks of 3 overstory removal treatments [clearcut (CC), shelterwood (SW), green tree retention (GT)]. Two plots within each replicate block were randomly allocated to each level of 3 nitrogen (N) treatments (0, 100, 250 kg ha-1, applied as urea) × 2 Vaccinium treatments (shoots present or removed).The three overstory removal treatments differed in the amount of solar radiation received beneath the canopy, in the order CC > GT > SW. Three to five growing seasons after treatment, advance regeneration in the GT and CC treatments exposed to >70% incoming solar radiation had the greatest height, stem diameter, and dry weight. N content, new N uptake (inferred from uptake of applied 15N), and allocation of uptake to new shoots were greatest in the CC followed by the GT and SW treatments. N fertilization had no effect on seedling growth. Removal of Vaccinium shoots increased stem diameter of advance regeneration, and increased new shoot dry weight in the GT treatment. Allocation of N to new shoots was greatest in advance regeneration from plots where Vaccinium was removed.
Book Reviews: Decision Methods for Forest Resource Management
Authors: Armstrong Glen W.
Published: April 2024

Decision Methods for Forest Resource Management is a book that describes several modeling approaches that natural resource managers use to help guide decisions. Nine of its 19 chapters are devoted to linear programming and its application to modeling even-aged and uneven-aged forest management. The book also covers goal programming, integer programming, CPM/PERT, dynamic programming, deterministic and stochastic simulation, Markov chains and decision processes, investment analysis, and econometric analysis and forecasting. The examples and the problems presented are relevant to forest management in today's environment. There is a strong emphasis on sustainability, environmental values (including biodiversity), and economics. The book is targeted at senior undergraduate students, graduate students, and professionals involved in natural resource management.
Tests for Long-Run Relationships in Hardwood Lumber Prices
Authors: Luppold William G. , Prestemon Jeffrey P.
Published: April 2024

Hardwood lumber prices are unique because of the large number of marketable species and variability of prices across species. Previous research showed that long-run fashion decisions regarding species selection may be influenced by price, so the interaction between fashion and species price may act to keep prices (hence, demand) of different hardwood species together in the long run. To test this hypothesis, we examined the joint lumber price behavior of six major hardwood species representing different appearance characteristics in the Appalachian hardwood region. Bivariate and multivariate price cointegration tests within lumber grades of these mainly nonstationary price series, conducted using a consistent vector error-correction rank and lag-order model selection procedure, revealed no stable long-run statistical relationships, rejecting the principal null hypothesis. Current relative price levels therefore cannot be used to infer future relative levels. Supplementary vector autoregressions of mostly differenced series, however, indicate that some interspecies price relationships exist. Such relationships, however, were mostly confined within appearance groups and only rarely across groups.
Local Analysis of Tree Competition and Growth
Authors: Shi Haijin , Zhang Lianjun
Published: April 2024

The relationships between the Local Indicator of Spatial Association (LISA) and traditional tree competition indices and individual tree growth were investigated. The results show that like most of the competition indices, LISA had moderate correlations with tree basal area growth. For predicting the tree basal area growth in a linear regression model, the local Gi performed better than many (73%) competition indices at a plot aggregation level and had higher explanatory power than most (91%) competition indices at an individual plot level. LISA also had linear and strong relationships with some traditional competition indices, such as the Lorimer index. The relationships were stronger (ρ >0.90) at an individual plot level than for all plots combined (ρ>0.75). More importantly, LISA could be statistically tested to identify local clusters of trees of similar or dissimilar sizes, even though there was no discernible pattern as summarized by a global statistic of spatial autocorrelation. These significant “hot spots” (clusters of trees of similar sizes) or “cold spots” (clusters of trees of dissimilar sizes) indicated subareas in a forest stand where the competition among trees may be more severe than the average. Therefore, LISA can replace the traditional competition indices for exploring the competitive status of neighboring trees, investigating the relationships between tree competition and growth, and estimating individual tree growth as a predictor variable in a forest growth simulator. The hot spots or cold spots identified by LISA provide useful information for the design of silvicultural and management treatments, such as selection thinning. Furthermore, LISA can be readily incorporated into visualization tools, such as a geographic information system (GIS), because it provides georeferenced information at a local level.
An Algorithm for Ensuring Compatibility Between Estimated Percentiles of Diameter Distribution and Measured Stand Variables
Authors: Mehtätalo Lauri
Published: April 2024

It is difficult to formulate a diameter distribution model that is compatible with many stand variables. In previous studies, compatibility of diameter distribution has been ensured with the aid of calibration (adjustment) based on making small changes to the predicted frequencies of diameter classes. In these methods, the minimum and maximum diameters cannot be changed, and the measurement error of the stand variables is not taken into account. In this study, two calibration methods based on minimizing deviations from predicted percentiles were developed. Because minimum and maximum diameters were among the predicted percentiles, there were no problems in changing them in the calibration. In the first method, the measurement error of the stand variables was not taken into account. In the second method, in addition to deviations from predicted percentiles, deviations from the measured stand variables were allowed, and the measurement error was taken into account by weighting each term of the objective function inversely by its error variance. The methods were tested in a dataset of Finnish mixed coniferous forests. Both methods were found to be better than the reference method used because the minimum and maximum diameters could be changed. Even if the measurement error was large, the second method was still advantageous, while the other methods were of no use. FOR. SCI. 50(1):20–32.
A Model for Foliage and Branch Biomass Prediction for Intensively Managed Fast Growing Loblolly Pine
Authors: Zhang Yujia , Borders Bruce E. , Will Rodney E. , Posadas Hector De Los Santos
Published: April 2024

Prediction models of foliage and branch biomass were derived based on the foliage distribution within the crown and the pipe model theory. Resulting models were fitted to data collected from intensively managed loblolly pine (Pinus taeda L.) plantations in the Lower Coastal Plain and Piedmont of Georgia. We found that diameter outside bark at the base of the live crown, crown height, and crown length are key predictors of foliage biomass. Together they produce reliable predictions of foliage and branch biomass for stands managed under a wide array of silvicultural treatments. The model indicates that an annual fertilization treatment significantly increased foliage and branch biomass in the Lower Coastal Plain. However, in the Piedmont, complete control of competing vegetation significantly increased foliage and branch biomass. A significant fertilization-age interaction for foliage and branch biomass was also detected in Piedmont stands. FOR. SCI. 50(1):65–80.
Comparison of Historical and Contemporary Forest Structure and Composition on Permanent Plots in Southwestern Ponderosa Pine Forests
Authors: Moore Margaret M. , Huffman David W. , Fulé Peter Z. , Covington W. Wallace , Crouse Joseph E.
Published: April 2024

We compared historical (1909–1913) and contemporary (1997–1999) forest structure and composition on 15 permanent plots in ponderosa pine (Pinus ponderosa Dougl. ex Laws.) forests of Arizona and New Mexico. We used the same sampling methods as in the early 1900s and compared stand density, diameter distributions, species composition, and broad age classes from the two periods. Stand density (trees ≥9.14 cm dbh) significantly (P < 0.001) increased on plots from an average of 77.4 trees per plot (s = 49.9) at plot establishment in 1909–1913 to 519.1 trees per plot (s = 252.3) at remeasurement in 1997–1999. Basal area significantly (P < 0.001) increased from 8.0 m2 per plot (s = 3.5) to 28.5 m2 per plot (s = 10.1). Contemporary tree diameter distribution shifted toward smaller size classes as demonstrated by a significant (P = 0.001) decrease in quadratic mean diameter from 38.5 cm (s = 7.5) in 1909–1913 to 28.6 cm (s = 7.1) in 1997–1999. Broad age classes yielded an average of 61.5 (s = 49.5) residual live trees classified as “blackjack” ponderosa pine (P. ponderosa <150 years) and 13.3 (s = 11.9) “yellow pine” (P. ponderosa ≥150 years) in 1909–1913. In 1997–1999, 416 live trees (s = 229.6) were “blackjack” and 57.2 (s = 28.5) trees on average were “yellow pine.” Twelve of the 15 plots were not invaded by other tree species (remained pure ponderosa pine type), while composition shifted slightly on three plots toward more shade-tolerant and fire-intolerant species. Ninety-one percent of the historically (1909–1913 or older) mapped tree structures (live trees, snags, logs, stumps, etc.) were relocated, which suggested that the forest reconstruction field techniques are reliable within 10%. Dramatic increases in tree densities may represent an increased potential for bark beetle epidemics and stand replacing wildfire over large areas in the Southwest. FOR. SCI. 50(2):162–176.
Projecting Diameter Growth in Tropical Trees: A New Modeling Approach
Authors: Ricker Martin , Río Rafael del
Published: April 2024

An important and heretofore unresolved challenge in forestry has been how to project long-term tree growth (i.e., decades to hundreds of years) from short-term measurements (here 1 year) for trees that do not present annual growth rings in their trunk wood. Such a method is crucial in the lowland tropics, where few long-term growth measurements have been taken, and where frequently trees lack reliable annual growth rings because of the lack of winters or highly seasonal dry periods. The new piecewise linear (PL) growth model, developed in this article, relates logarithmic relative growth to trunk diameter. Having obtained the coefficients from piecewise linear regression, the long-term age-diameter curve is calculated, i.e., the expected average growth curve of a statistical population of individual trees. The model is applied to the following five tree species without annual growth rings from the tropical rainforest in Los Tuxtlas (Veracruz, Mexico): Aspidosperma megalocarpon, Cordia alliodora, Dialium guianense, Guarea grandifolia, and Persea schiedeana. Using the tools of multiple linear regression, the PL model is highly flexible to derive sigmoid, exponential, and over-exponential growth separately for different diameter segments. FOR. SCI. 50(2):213–224.
Book reviews: Ecology and Control of Introduced Plants
Authors: Webster Christopher R.
Published: April 2024

Intentional and unintentional introductions of exotic organisms have become commonplace in our increasingly global society. While many of these introductions have been benign, others have significantly altered native ecosystems and posed insurmountable challenges to agriculture, forestry, and the conservation of biological diversity worldwide.
Forest Stand Structure and Pattern of Old-Growth Western Hemlock/Douglas-Fir and Mixed-Conifer Forests
Authors: North Malcolm , Chen Jiquan , Oakley Brian , Song Bo , Rudnicki Mark , Gray Andrew , Innes Jim
Published: April 2024

With fire suppression, many western forests are expected to have fewer gaps and higher stem density of shade-tolerant species as light competition becomes a more significant influence on stand pattern and composition. We compared species composition, structure, spatial pattern, and environmental factors such as light and soil moisture between two old-growth forests: Pacific Northwest western hemlock/Douglas-fir at the Wind River Canopy Crane Research Facility exhibiting gap-phase replacement and southern Sierra Nevada mixed conifer at the Teakettle Experimental Forest after 135 years without a fire. We hypothesized that fire suppression at Teakettle would create a current tree composition and distribution more like Wind River where light is an important influence on stand dynamics. Wind River has nearly continuous canopy cover and a high foliage volume that severely reduces understory light and stratifies the canopy composition by shade tolerance. Large trees are regularly spaced from 0 to 15 m and shade-tolerant and intolerant species are “repelled.” In contrast, Teakettle's canopy cover is discontinuous, foliage volume is one-fifth that of Wind River, and understory light is 15 times higher. Trees at Teakettle are significantly clustered in groups containing a mix of shade-tolerant and -intolerant species, separated by large gaps. Although Teakettle's gaps have higher moisture and a thinner litter layer than tree groups, regeneration in gaps is scarce. Fire suppression has increased stem density at Teakettle but it has not filled in gaps, stratified the canopy by shade tolerance, or produced a composition consistent with patterns at Wind River. Teakettle's distinctly clustered stem distribution may result from a minimum canopy cover threshold needed for tree establishment. If high temperatures produced by direct sunlight inhibit stem patterns, traditional stand management that reduces canopy cover to release regeneration should be applied with caution in the southern Sierra Nevada. FOR. SCI. 50(3):299–311.
The Distribution of Free Space and Its Relation to Canopy Composition at Six Forest Sites
Authors: Dial Roman , Bloodworth Benjamin , Lee Andrew , Boyne Patrick , Heys Jeffrey
Published: April 2024

Forest canopy free space, element density (clutter), and the distribution and relative abundance of coarse canopy elements were measured at six sites: two boreal (south-central Alaska), two temperate (Washington State and Victoria, Australia), and two tropical (Pacific Costa Rica and Malaysian Borneo). Great clutter, high relative abundance of dead elements, and shallow understory characterized boreal canopies. Presence of dead elements and deep understory characterized temperate sites, sharing clutter profiles that differed in magnitude but not shape from each other. Few dead elements, little obvious zonation, and constant, mid-canopy clutter characterized tropical sites. The neotropical site showed a clear overstory, while the paleotropical site did not. The results motivate three hypotheses: (1) forest canopies of similar latitude and climate have similar structure; (2) canopy zones form cohesive, repeatable structures as “understory” (near-ground nondominant vegetation bounding small free-spaces), “overstory” (high, dominant foliage bounding small free-spaces), “bole zone” (mid-canopy boles bounding the largest free spaces), and “dead zone” (unique to conifer sites and typified by dead elements and upwardly narrowing free-spaces above bole zone); and (3) Australian and paleotropical canopies, regions rich in vertebrate gliders, are an order of magnitude more open (less cluttered) than neotropical and North American canopies, regions poor in gliders. FOR. SCI. 50(3):312–325.
Market Dynamics and Optimal Timber Salvage After a Natural Catastrophe
Authors: Prestemon Jeffrey P. , Holmes Thomas P.
Published: April 2024

Forest-based natural catastrophes are regular features of timber production in the United States, especially from hurricanes, fires, and insect and disease outbreaks. These catastrophes affect timber prices and result in economic transfers. We develop a model of timber market dynamics after such a catastrophe that shows how timber salvage affects the welfare of different market groups and quantifies the impacts of salvage on product markets. A theoretical framework is developed that explores how government spending to mitigate economic losses through salvage is related to the costs of intervention. Using empirical price and quantity parameters derived for Hurricane Hugo as an example, we simulate how alternative levels of salvage would have affected southern pine timber prices and economic surplus. Results show that for this large-scale disturbance, the economic surplus generated by salvage averaged $6.25 million for each percentage change in the volume of salvaged timber up to the observed salvage rate (∼16%). Consumers benefited by an average of $5.4 million for each percent of the damaged timber that was salvaged, producers of salvaged timber benefited by $6.4 million for each percent salvaged, and producers of undamaged timber lost an average of $5.6 million for each percent salvaged. Sawtimber salvage yielded welfare benefits for each cubic meter averaging more than four times those generated by pulpwood. These results therefore have implications for strategic salvage planning following catastrophic damage to forests. FOR. SCI. 50(4):495–511.
Note—Foliage-Sapwood Area Equations for Balsam Fir Require Local Validation
Authors: Gilmore Daniel W. , Seymour Robert S.
Published: April 2024

The foliage-sapwood area relationship (AL/AS) for balsam fir has been described in three separate studies with no less than four regression model forms. While there are clear differences in predicted AL values between the studies, it is not apparent if these differences are an artifact of the regression model form used or caused by regional differences in the AL/AS relationship. We extracted published AL and AS values from the literature to statistically determine the best model form to describe the AL/AS relationship. Using this model form, we then explicitly tested for regional differences in the AL/AS relationship. We found that a linear model using natural logarithmic transformations best satisfied the assumptions of least squares regression in describing the AL/AS relationship. Based on the published data, there may be regional differences in the AL/AS relationship for balsam fir. FOR. SCI. 50(4):566–570.
Surrogate Pheromone Plumes in Three Forest Trunk Spaces: Composite Statistics and Case Studies
Authors: Thistle Harold W. , Peterson Holly , Allwine Gene , Lamb Brian , Strand Tara , Holsten Edward H. , Shea Patrick J.
Published: April 2024

An atmospheric tracer gas was used as a pheromone surrogate to study near-field canopy dispersion within the trunk space. The objective is to improve guidance for forest managers deploying bark beetle antiaggregation pheromone sources to protect high-value forest stands. Data are shownfrom field studies in three forest canopies (oak-hickory, Quercus-Carya; lodgepole pine, Pinus contorta Dougl. ex Loud.; and ponderosa pine, Pinus ponderosa Dougl. ex Laws.) and include over 13,000 chemical tracer samples compiled into half-hour dispersion fields arounda point source. Maximum normalized concentrations (χ/Q) at each arc distance for each sampling period were of similar order at 5 m from the tracer source in the three canopies, although the differences in maximum χ/Q between canopies increased with distance from thesource. Plume dilution was highest in this study in the more open ponderosa pine canopy. A high-frequency tracer gas analyzer was also deployed to ascertain the structure of the gas plumes at 1 Hz. The high-frequency tracer data showed that the 30-minute average mean plumes are compositesof narrow filamentous plumes. The near-field plumes in each canopy were strongly affected by changes in atmospheric stability, as wander range and meander frequency increased after the morning transition to an unstable boundary layer. FOR. SCI. 50(5):610–625.
Climate and Productivity of Major Conifer Species in the Interior of British Columbia, Canada
Authors: Nigh Gordon D. , Ying Cheng C. , Qian Hong
Published: April 2024

Lodgepole pine (Pinus contorta var. latifolia Engelm. ex S. Wats.), interior spruce (including Picea glauca (Moench) Voss, P. engelmannii Parry ex. Engelm., P. glauca×engelmannii), and interior Douglas-fir (Pseudotsuga menziesiivar. glauca (Beissn.) Franco) are the most important commercial species in the interior of British Columbia. We develop statistical models to predict site index (a measure of site productivity) from climate for these species. Using data from 193 climate stations, we first developedmodels that predict mean annual temperature, mean temperature of the warmest and coldest months, number of frost-free days, and frost-free period from latitude, longitude, and elevation. With these models and the Parameter-elevation Regressions on Independent Slopes Model (used to predictmean annual and mean summer precipitation), we predict 10 climate attributes for site index plots of lodgepole pine, interior spruce, and interior Douglas-fir. These attributes are then used in regression models to estimate site index. The models allow us to investigate the current relationshipbetween climate (particularly temperature and precipitation) and site productivity for these species. The productivity for all the species studied increased as temperature increased, with lodgepole pine exhibiting the greatest response. The productivity of lodgepole pine and interior Douglas-firalso increased with increasing precipitation, with interior Douglas-fir having a greater response than lodgepole pine. We discuss the application of the models in relation to the impact of climate change on site productivity. FOR. SCI. 50(5):659–671.
Effects of Fertilization with Dolomite Lime+PK or Wood Ash on Root Distribution and Morphology in a Norway Spruce Stand in Southwest Sweden
Authors: Majdi Hooshang , Viebke Claes-Göran
Published: April 2024

Pelleted wood ash (A) or crushed dolomite lime with added potassium and phosphorous (CaMgPK) was applied to plots in a 60-yr-old Norway spruce stand in Southwest Sweden. Eight years later, we measured the effect of these treatments on a number of root parameters, including root biomass and distribution (in different diameter classes), root length density (cm cm-3 soil), specific root length (SRL, m g-1 DM), and number of mycorrhizal root tips. Layers sampled included the humus layer and the upper 30 cm of the mineral soil. The total fine root (0–1 mm) biomass in the mineral soil layer was lower in the A plots than the control plots, and the fine root (1–2 mm) systems were shallower in the A plots compared to both the control and CaMgPK plots. SRL was higher in the humus layer in both the CaMgPK and A plots than in the controls, and higher in the CaMgPK than in the A plots. The number of mycorrhizal root tips was also higher in the treated plots than in the controls, with the highest numbers being found in CaMgPK plots. Based on our results, we conclude that both the CaMgPK and ash treatments resulted in changes in root morphology and, therefore, presumably increased the capacity for nutrient uptake. FOR. SCI. 50(6):802–809.
Book Reviews: Analysis of Ecological Communities
Authors: Battles John J.
Published: April 2024

As an aspiring student in forest ecology, I was never more distressed about my career choice than when a senior graduate student predicted that I would spend more time learning statistics than any other subject. Twenty years later, the contents of my bookshelf and hard drive provide compelling evidence of the truth of this prediction. Community ecology has collected an eclectic mix of multivariate techniques to quantify the relationships among species and their environment. The challenge has always been to sort through the lot to find the most appropriate approach given the question and the data. While I still sometimes pine for the simplicity of a two-way analysis of variance (ANOVA), Bruce McCune and James Grace's book, Analysis of Ecological Communities satisfies my craving for statistical clarity. They provide an exemplary guide to the convoluted terrain of multivariate data analysis.
An Evaluation of Spatial Dependency in Juvenile Loblolly Pine Stands Using Stem Diameter
Authors: Bullock Bronson P. , Burkhart Harold E.
Published: April 2024

A simultaneous autoregressive model (SAR) was used to evaluate the amount of spatial influence juvenile loblolly pine (Pinus taeda L.) stems in a plantation have on one another. The presence of spatial autocorrelation between stems in a stand indicates that the characteristics of one stem are related to the characteristics of neighboring stems. The stands evaluated in this study had planting densities that varied from 747 to 6,727 trees per hectare. The SAR model contains a spatial dependency parameter that captures the inter-tree influences. Analysis on detrended diameter data showed that across ages 2 to 5 for groundline diameter measurements and ages 5 to 11 for breast height diameter measurements, the simultaneous autoregressive model indicated significant spatial dependency parameters in 23.2% of the plots (alpha-level = 0.10). A generally increasing trend in the occurrence of significant spatial influence from 18.2% to 28.4% was noted with an increase in planting density from 747 to 3,364 trees per hectare, beyond which the trend decreased. Estimation of the spatial dependency parameter will aid in describing juvenile competition processes and developing a more precise representation of juvenile forest stands. FOR. SCI. 51(2):102–108.
Influence of Fire and El Niño on Tree Recruitment Varies by Species in Sierran Mixed Conifer
Authors: North Malcolm , Hurteau Matthew , Fiegener Robert , Barbour Michael
Published: April 2024

The influence of fire and climate events on age structure of different species was examined in old-growth mixed conifer in the southern Sierra Nevada. Within a 48-ha stem-mapped sample area, after a mechanical thinning, all stumps were examined for fire scars and 526 stumps were cut to ground level and aged. Before 1865, which was the last widespread fire event, the mean interval between scars for an individual tree was 17.3 years and the mean fire return interval for the period with the greatest number of recording trees was 11.4 years. A significantly greater than expected number of fires occurred in dry La Niña years, but these fires were not significantly larger in size than fires in other years. The response of mixed-conifer recruitment to climate and fire events varied by species. Before 1865, Jeffrey pine and sugar pine recruitment were correlated with wet El Niño years, but only sugar pine establishment was associated with fire. Red fir recruitment did not follow fire events but was associated with El Niño years before and after 1865. Most white fir and incense cedar (84%), including many large-diameter trees (>76 cm dbh), recruited after the last widespread fire in 1865. Although tree distribution is clustered in the southern Sierra Nevada, mixed-conifer groups are not age cohorts because species have different recruitment patterns relative to climate and fire events. In mixed conifer, top-down effects of fire and weather on recruitment are mediated by different species responses to these effects and within-stand differences in where species are located. FOR. SCI. 51(3):187–197.
Stand Conditions Associated with Tree Regeneration in Sierran Mixed-Conifer Forests
Authors: Gray Andrew N. , Zald Harold S. J. , Kern Ruth A. , North Malcolm
Published: April 2024

Fire suppression has significantly increased canopy cover, litter depth, and stem density in many western forests, altering microsite conditions that affect tree seedling establishment. We conducted studies in a mixed-conifer forest in the Sierra Nevada, California, to determine relationships between established understory trees and microsite quality, and to examine the effect of fire intensity and shrub cover on seedling establishment. Most of the conifer species were found on microsites with relatively high soil moisture and relatively low direct solar radiation. All species had greater frequency under shadier conditions except for Jeffrey pine, which was found on drier, more open microsites. Although seedlings were more abundant on mineral soil than expected, intact litter and forest floor was not a barrier to establishment. Mortality of planted seedlings was high, particularly in exposed areas. Although shrub cover may initially aid survival, few conifer saplings were present in shrub-dominated patches, possibly because shrubs can be aggressive competitors for soil moisture. The lack of regeneration, logs, or snags in many openings suggest that large gaps are hostile environments for tree seedlings. Results suggest that reductions in shrub cover may benefit tree establishment, but increasing understory light and decreasing surface soil moisture through canopy cover reductions may not. FOR. SCI. 51(3):198–210.
A Re-Evaluation of Reineke's Rule and Stand Density Index
Authors: Pretzsch Hans , Biber Peter
Published: April 2024

The self-thinning rule established by Reineke in 1933, N α d−1.605 (N, d = number of stems and quadratic mean diameter, respectively) assumes the same allometric relationship between size and density for a wide spectrum of species under self-thinning conditions. We re-evaluate this rule based on 28 fully stocked pure stands of common beech (Fagus sylvatica L.), Norway spruce (Picea abies [L.] Karst.), Scots pine (Pinus sylvestris L.), and common oak (Quercus petraea [Mattuschka] Liebl.) in Germany that date back to the year 1870. OLS regression of the model ln(N) = a + b · ln(d) results in b values of −1.789 for common beech, −1.664 for Norway spruce, −1.593 for Scots pine, and −1.424 for common oak. The allometric coefficient for common beech differs significantly from the other species. There is also a significant difference between the b values of Norway spruce and common oak. Except for Scots pine, the above allometric coefficients deviate significantly (common beech) and close-to-significantly (Norway spruce, common oak) from the coefficient −1.605 postulated by Reineke in 1933. To cover the species–specific oscillation of mortality rates, we additionally calculate the self-thinning coefficient for each survey period. Ecological implications of the species-specific scaling exponents are stressed and consequences regarding tools for regulating stand density are discussed. FOR. SCI. 51(4):304–320.
BOOK REVIEW: Modern Biogeochemistry
Authors: Chang Scott
Published: April 2024

Professor Bashkin's recent book “Modern Biogeochemistry” provides an in-depth analysis of the many aspects of biogeochemistry of some key chemical elements in a wide variety of ecosystems. The book essentially evolved from the lectures professor Bashkin gave at the Universities of Cornell, Moscow, Pushchino, Seoul, and Bangkok.
Provenance Trials of Ponderosa Pine in Northern California
Authors: Kitzmiller Jay H.
Published: April 2024

Growth of 17 ponderosa pine populations transferred within the southern Cascades–Sierra Nevada ranges were tested for 19 years on two contrasting sites, Cherry Hill (CH) and Peanut Springs (PS). Seven additional southern Sierra populations were tested at PS. Results provide guidance to forest managers seeking to reforest ponderosa pine after large wildfires or to improve productivity of plantations. PS represented warm, moist, lower mixed-conifer sites in the central Sierra. CH represented colder, drier climates at the southern limit of the Cascades in upper elevation mixed-conifer. High inherent site productivity at PS was reduced by topsoil displacement and brush competition for moisture and/or nutrients. Contrasting magnitudes and patterns of growth among provenances were expressed between sites. The local provenance at PS outgrew more distant sources by 12 to 74%. However, high elevation, nonlocal Sierra sources grew best at CH, where volume decreased with source latitude and increased with source elevation. All sources had stockier form at CH. In both tests, Sierra sources outgrew and were stockier than Cascade sources; stockiness increased with source elevation. Current results at CH support matching provenance elevation with site, using southern sources. Results at PS strongly support the use of local seed, with allowance for transferring seed to adjacent zones. FOR. SCI. 51(6):595–607.
Litterfall Dynamics of an Evergreen Broadleaf Forest and a Pine Forest in the Subtropical Region of China
Authors: Li Zhi An , Zou Bi , Xia Han-ping , Ren Hai , Mo Jiang-ming , Weng Hong
Published: April 2024

Monthly litterfall was monitored over a 10-year period from an evergreen broadleaf forest (EBF) and a pine forest (PF) in subtropical South China. During this period, litter was also collected bimonthly from the forest floor for 2 years. Total annual litterfall in EBF fluctuated around 9 Mg ha−1 with leaves, branches, and miscellanea accounting for 52.5%, 22.2%, and 25.3%, respectively. Total annual litterfall alternated between high and low values in consecutive years. Storms and pest outbreaks were responsible for most of the peaks in both monthly and annual litterfall. Litter from each of 43 species was recorded, but 9 species contributed about 85% of total litterfall. Dominant species shed their leaves in a more regular pattern with peaks mainly from Jan. to Mar. Pine forest (Pinus massoniana) produced much less litterfall than EBF, with a mean of 2.7 Mg ha−1. Here, leaves accounted for 73.2% of total litterfall, branches only 11.4%, and miscellanea 15.4%. Litter on the ground amounted to 5.2 Mg ha−1 in EBF and 2.9 Mg ha−1 in PF. The results show that this climax forest has much higher litterfall and forest floor mass than the pine forest, and litterfall is rather stable with regard to annual variation. FOR. SCI. 51(6):608–615.
BOOK REVIEWS: Valuing Agroforestry Systems: Methods and Applications
Authors: Luckert Martin K.
Published: April 2024

Agroforestry has long been touted as a management approach with potential for gaining synergies between agricultural and forest production. A staple approach in developing-country situations, agroforestry systems are increasingly being considered in developed-country settings. However, socioeconomic analyses of agroforestry systems have long lagged behind natural science contributions. This volume, the second in the series “Advances in Agroforestry,” makes a significant step in promoting the social science importance of agroforestry. The editors have assembled a nice collection of studies regarding the valuation of agroforestry systems around the world, encompassing developing and developed country settings. The approaches used arise largely from an economics disciplinary background, but there is much in here of interest to a broader, multidisciplinary audience.
Cost-Sharing and Private Timber Stand Improvements: A Two-Step Estimation Approach
Authors: Ovaskainen Ville , Hänninen Harri , Mikkola Jarmo , Lehtonen Emmi
Published: April 2024

The effects of cost-sharing and information assistance on nonindustrial private forest owners’ investment in timber stand improvements are analyzed using a two-step estimation method. We use survey data on Finnish nonindustrial private forestland owners’ stand improvements in 1994–1998, including precommercial thinnings, cleaning of seedling stands, and restoration thinnings of juvenile stands. The investment decision is theoretically considered in a two-period model with amenity values. To allow for the joint determination of participation in the cost-sharing program and the decision to invest, a two-step estimation method is used. The predicted probability of using public subsidy from the first-step model is included in the second-step model for the probability or relative extent of stand improvements. For robust inference, quasi-maximum likelihood estimation is applied. Public subsidy, personal assistance, and forest planning expectedly increased the probability of investing. Public subsidy especially had substantial effects on the probability and extent of stand improvements. Besides overcoming the endogeneity of cost-sharing, the two-step approach showed that personal assistance also encourages stand improvements indirectly through its effect on the use of public subsidy.
Detailed Stem Measurements of Standing Trees from Ground-Based Scanning Lidar
Authors: Henning Jason G. , Radtke Philip J.
Published: April 2024

A commercially available pan-and-tilt mount laser scanner was used to acquire data for subsequent three-dimensional modeling and measurement of standing forest trees. Methods were developed for identifying trees in range images and co-registering range images acquired from different vantage points. Upper-stem diameters and branch heights derived from the range images were compared to measurements made after the felling of a small number of loblolly pine (Pinus taeda L.) trees. Tree identification assumed bole cross-sections were circular, estimating their geometric centers at successive heights up the stem. Tree center estimates at multiple heights were then used to co-register images made from different vantage points. Co-registration (x, y) errors did not exceed 2.1 cm in any of the 18 pairwise registrations carried out. Results showed excellent agreement (average error < 1 cm) between the lidar-derived diameter estimates and caliper measurements for bole sections below the base of live crown. Less accurate estimates (<2 cm) were obtained for stem heights up to 13 m. Results indicated the potential for accurate assessment of branch or whorl heights using ground-based scanning lidar, with the greatest accuracy likely to be realized for branches near the base of the live crown and below it.
Horizontal Line Sampling for Riparian Forests without Land Area Estimation
Authors: Lynch Thomas B.
Published: April 2024

Sampling forests in riparian areas presents unique difficulties that can be addressed by judicious application of line sampling. Land areas associated with riparian forests often have highly irregular boundaries, making accurate area determination difficult. Therefore, estimators for total amounts of forest attributes that do not depend on land area are desirable. Such estimators can be obtained by using horizontal line sampling from sample lines that are located at random intervals along a straight baseline and which extend entirely through the riparian area of interest. Horizontal line sampling selects sample trees that subtend an angle whose vertex is located on a length of line. This is conceptually similar to Ståhl's transect relascope sampling (Ståhl, G. 1998. Transect relascope sampling—A method for the quantification of course woody debris. For. Sci. 44:58–63), which estimates total amounts of coarse woody debris from lines established at fixed intervals. Use of a control variate or importance sampling based on predicted line length (where available) is suggested as a variance reduction technique. An unbiased estimator for sampling at intervals along the line is suggested. Monte Carlo integration estimates of riparian land area are proposed for estimation of per-unit area quantities. These estimators could be applied to any forested area but appear to be most well suited to long, relatively narrow riparian areas.
Applying an Efficient k-Nearest Neighbor Search to Forest Attribute Imputation
Authors: Finley Andrew O. , McRoberts Ronald E. , Ek Alan R.
Published: April 2024

This article explores the utility of an efficient nearest neighbor (NN) search algorithm for applications in multisource kNN forest attribute imputation. The search algorithm reduces the number of distance calculations between a given target vector and each reference vector, thereby decreasing the time needed to discover the NN subset. Results of five trials show gains in NN search efficiency ranging from 75 to 98% for k = 1. The search algorithm can be easily incorporated into routines that optimize feature subsets or weights, values of k, distance decomposition coefficients, and mapping.
Base–Age Invariance Properties of Two Techniques for Estimating the Parameters of Site Index Models
Authors: Strub Mike , Cieszewski Chris J.
Published: April 2024

Using eight hypothetical data points (four growth series with two observations each) the difference between two site index curve parameter estimation methods, the base–age invariant stochastic regression approach (BAI) and the method of all base ages (BAA), is illustrated. The anamorphic form of the Schumacher log-transform height–age equation is used for the comparison. The two estimation techniques are equivalent for the linear case of the model but produce different parameter estimates for its nonlinear form. For both linear and nonlinear cases the BAI approach produced a lower root-mean-squared error than the BAA method. Only the BAI approach produced unique estimates for the site-specific parameters of both model forms and both growth series.
Variance Reduction for Sector Sampling
Authors: Lynch Thomas B.
Published: April 2024

Variance reduction techniques used in Monte Carlo integration including control variates and importance sampling can use estimated or actual shapes of vegetated land areas to reduce the variance of estimators from sector sampling. The estimated shapes of forested areas could come from maps, aerial photos, or similar sources. Antithetic variates for variance reduction in Monte Carlo integration can be applied to sector sampling without using any estimated shape or map. Sector sampling selects as samples all trees or other vegetation of interest located in randomly chosen sectors that have a vertex at a common point located in the interior of a forested area. Each sector is associated with an angle of fixed magnitude emanating from the interior point. Sector orientation is based on a randomly selected azimuth originating at the interior point that is the vertex for each sector. This technique is well adapted to application on relatively small areas that have irregularly shaped boundaries. Sector sampling can be demonstrated to be unbiased. Unbiasedness holds with angle reduction for adjustment of sample size and with the variance reduction techniques that are proposed. The method is not restricted to application with trees because sector sampling methods could be applied just as well to other vegetation types or any other objects located in the land area of interest.
Competitiveness in the Sawmills and Wood Preservation Industry in the United States and Canada
Authors: Nagubadi Rao V. , Zhang Daowei
Published: April 2024

We examine relative prices, relative productivity levels, and competitiveness in the sawmills and wood preservation industry in the United States and Canada between 1958 and 2003 by using purchasing power parities and bilateral translog production function. Our results show that the competitiveness of the Canadian industry is facilitated by higher relative productivity levels and depreciation of the Canadian dollar relative to the US dollar on both inputs and outputs in earlier periods, and only due to depreciation of the Canadian dollar in later periods. The average annual rate of productivity growth was higher for the US industry. Although Canadian relative productivity levels were higher before 1994, the US industry's relative productivity level eventually surpassed the Canadian industry.
Canada–U.S. Softwood Lumber Trade Revisited: Substitution Bias in the Context of a Spatial Price Equilibrium Framework
Authors: Mogus Anthony , Stennes Brad , van Kooten G. Cornelis
Published: April 2024

Softwood lumber trade between Canada and the United States has been characterized by various trade restrictions. Many studies have attempted to quantify the effects of such sanctions, modeling softwood lumber as a single, homogenous commodity, although recent research suggests that this may be a misleading assumption because softwood lumber products vary. In this article, we address the problem of “substitution bias” in estimates of the effects of trade restricting policies. A spatial price equilibrium model is used to examine the effects of import duties on Canadian lumber, comparing these with the effects of an export tax and quota. By controlling for substitution bias, our estimates indicate that a larger share of the tariff burden is placed on U.S. consumers, with Canadian producers suffering less injury compared to estimates based on the traditional assumption of a homogenous product. In addition, by comparing the net impact associated with the alternative policy regimes, a policy equivalence is found. Results suggest that the short-run impact of a trade restriction is largely independent of the policy regime incorporated, with the collection of quota rents or tax revenues determining overall winners and losers.
Modeling Postfire Mortality of Ponderosa Pine following a Mixed-Severity Wildfire in the Black Hills: The Role of Tree Morphology and Direct Fire Effects
Authors: Keyser Tara L. , Smith Frederick W. , Lentile Leigh B. , Shepperd Wayne D.
Published: April 2024

We examined the relationship among tree size, crown and stem damage, and 5 years of postfire mortality of ponderosa pine (Pinus ponderosa Dougl. ex. P. & C. Laws.) in the Black Hills following a large, mixed-severity wildfire. We measured tree morphology and direct fire effects on 963 trees and assessed individual tree mortality annually from 2001 to 2005. We used logistic regression to model tree mortality as a function of tree morphology (dbh) and bark thickness (BARK) and direct fire effects [percentage of the live crown scorched (PSCOR) and basal char measured as the percentage of the bole charred below 30 cm (CHAR)]. Models using dbh and BARK were modeled separately due to correlation between the variables. In all models, mortality decreased with increasing dbh and BARK and increased with increasing PSCOR and CHAR. Basal char contributed to the mortality of trees less than 40 cm but became less influential as dbh and BARK increased. Overall, probability of mortality modeled as a function of dbh, PSCOR, and CHAR correctly predicted the status of 78% of trees, whereas the model predicting mortality as a function of BARK, PSCOR, and CHAR had an increase in prediction accuracy of only 1%.
Capital Structure in the United States Forest Products Industry: The Influence of Debt and Taxes
Authors: Mendell Brooks C. , Sydor Tymur , Mishra Neena
Published: April 2024

This article investigates financing practices across firms in the forest products industry by studying the relationship between debt and taxes hypothesized in finance theory. In testing the theoretical relationship between taxes and capital structure for 20 publicly traded forest industry firms for the years 1994–2003, we find a negative relationship between profitability and debt, a positive relationship between nondebt tax shields and debt, and a negative relationship between firm size and debt. All three results run counter to theoretical expectations. Results indicate that, controlling for size, firms in the forest products industry with higher market valuations and pretax earnings used more conservative financing strategies. Also, the article develops a dynamic panel model with fixed effects for each firm and residualization to address issues of multicollinearity.