bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects on Estimation Accuracy of Forest Variables Using Different Pulse Density of Laser Data
Authors: Magnusson Mattias , Fransson Johan E.S. , Holmgren Johan 
Published: April 2024

Abstract
Collection of airborne laser scanner data for forest inventory is becoming a common practice today. To reduce cost when laser data are collected over large areas, the flight altitude or flight speed may be increased, resulting in low pulse density laser data. The effect of using a different pulse density of laser data on estimation accuracy of forest variables was investigated at stand level. Laser data were acquired by the airborne TopEye system at a 1,200-ha forest area located in southern Sweden (58°30′N, 13°40′E). The 70 selected stands were dominated by Norway spruce [Picea abies (L.) Karst.] and Scots pine (Pinus sylvestris L.) with tree height in the range of 6–28 m (mean 19 m) and stem volume in the range of 30–620 m3 ha−1 (average 286 m3 ha−1). Regression analysis was used to establish empirical functions at stand level. The pulse density of laser data was reduced from 25,000 to 40 returns ha−1. By reducing the pulse density the root mean square error (RMSE) for the tree height and stem volume estimation increased from 0.7 to 1.8 m and from 13% to 29%, respectively. A substantial decrease in estimation accuracy of tree height and stem volume could be observed at pulse densities &lt;80 returns ha−1 (corresponding to about 10 m between adjacent laser returns). The rapid increase in RMSE at these pulse densities could be explained by the less accurate classification of ground returns. With access to a high resolution digital elevation model the RMSE for the tree height and stem volume estimation increased from 0.7 to 1.1 m and from 13% to 23%, respectively, as an effect of the reduced pulse density. Even though the pulse density was reduced to several meters between adjacent laser returns, the estimation accuracies were equal to or better than those commonly obtained by using conventional forest inventory methods, e.g., aerial photo interpretation. This finding implies that low pulse density airborne laser scanner data could be cost efficient to use in inventory for estimation of forest variables at stand level.
Ectomycorrhizal Communities on Tree Roots and in Soil Propagule Banks along a Secondary Successional Vegetation Gradient
Authors: Yamashita Satsuki , Fukuda Kenji , Ugawa Shin 
Published: April 2024

Abstract
Changes in the composition of underground ectomycorrhizal communities along a secondary successional vegetation gradient were investigated in Kashiwa City, Kanto District, eastern Japan. Soil cores were sampled from the surface soils of six plots in a successional series of vegetation, and ectomycorrhizal root tips were classified into morphotypes by macroscopic observation and measurement of the internal transcribed spacer 3–4 length of rDNA. The inoculum potential of ectomycorrhizal fungi in the soils was also investigated by germinating and growing Japanese red pine seedlings in pots. The species richness of ectomycorrhizal fungi on tree roots increased along the successional gradient from the pioneer tree stage (Pinus densiflora Sieb. et Zucc. stands) to the middle stage (deciduous Quercus serrata Thunb. and Castanea crenata Sieb. stands) and then slightly decreased in the climax stage (evergreen Quercus myrsinaefolia Bl. stands). The increase in the number of ectomycorrhizal morphotypes was strongly correlated with the increase in the biomass of ectomycorrhizal trees along the succession. Ectomycorrhizal propagule banks were found in the soil of pioneer grass- and shrublands where ectomycorrhizal trees were not present. Unlike the diversity of ectomycorrhizal morphotypes on tree roots, the morphotype richness and diversity of ectomycorrhizal inocula in the soil infective to pine seedlings increased only from the grassland to the pine successional stage and not in the deciduous and evergreen-oak stages. The composition of ectomycorrhizal communities on mature trees and ectomycorrhizal propagule banks in soils showed a successional gradient along the secondary vegetation gradient, but many common morphotypes were present among the different vegetation stages.
Predicted Fire Behavior in Selected Mountain Pine Beetle–Infested Lodgepole Pine
Authors: Page Wesley , Jenkins Michael J. 
Published: April 2024

Abstract
Using custom fuel models developed for use with Rothermel's surface fire spread model, we predicted and compared fire behavior in lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.) stands with endemic, current epidemic, and postepidemic mountain pine beetle (Dendroctonus ponderosae Hopkins) populations using standardized sets of wind speeds and fuel moistures. We also compared our fire behavior results with those from standard fuel models. Results indicated that for surface fires both rates of fire spread and fireline intensities were higher in the current epidemic stands than in the endemic stands owing to increases in the amounts of fine surface fuels. In the postepidemic stands, rates of surface fire spread and fireline intensities were higher than in the endemic stands owing to decreased vegetative sheltering and its effect on mid-flame wind speed. Total heat release of surface fires, including postfrontal combustion, was also higher in the postepidemic stands owing to heavy accumulations of large diameter fuels. Crown fires were more likely to initiate in the postepidemic stands owing to greater fireline intensities and lower crown base heights. However, the critical rate of spread needed to sustain an active crown fire was higher in the postepidemic stands owing to decreased aerial fuel continuity. We suggest here that crown fire initiation in the current epidemic stands was also greater because of an abundance of dead aerial fuels; although this relationship is unclear.
Effect of Centrifugal Forces on Cluster Patterns in the Softwood Lumber Industry of the United States
Authors: Aguilar Francisco X. 
Published: April 2024

Abstract
Although previous reports have identified clustering in the secondary wood products industry, there are no previous studies on the factors influencing spatial patterns in the primary wood products sector. This study explores the perceptions of members of the softwood lumber industry in the United States concerning factors driving location and promoting cluster patterns in this particular industry. The analysis builds on the core-periphery framework of New Economic Geography to identify centrifugal and centripetal forces and determines the most salient advantages and disadvantages derived from industry clustering. The most essential location factors are linked to the availability of raw materials and skilled labor. The results of the factor analysis, reinforced by bootstrapping estimation, suggest that centrifugal forces outweigh centripetal forces. Greater dispersive effects of centrifugal forces result in a peripheral primary wood products industry pattern. Clustering of softwood sawmills is perceived as detrimental to this industry segment because it results in higher costs of inputs, congestion, and undesired competition. However, geographical coincidence between primary and secondary wood product manufacturers that fosters collaboration can result in an enhanced competitive industry structure.
Variation in Mechanical Properties of Selected Young Poplar Hybrid Crosses
Authors: Yu Qibin , Zhang S.Y. , Pliura Alfas , MacKay John , Bousquet Jean , Périnet Pierre 
Published: April 2024

Abstract
To better understand the variability in mechanical properties caused by genetic differences in hybrid poplars, modulus of elasticity and modulus of rupture in static bending were examined at two 10-year-old clonal trials located at Windsor and St-Ours, southern Quebec, Canada. The materials consisted of three hybrids, Populus deltoides × Populus nigra, Populus trichocarpa × P. deltoides, Populus maximowiczii × Populus balsamifera, and native P. deltoides. Significant differences were observed in mechanical properties among hybrids and P. deltoides. The effects of growth on the mechanical properties were inconsistent and varied considerably by site and by hybrid. Results indicated no uniform trends relating growth rate to either higher or lower modulus of elasticity/modulus of rupture. It appears that selection for strength properties may not uniformly lead to decreased growth production, especially for P. trichocarpa × P. deltoides and P. maximowiczii × P. balsamifera.
Ecological and Economic Determinants of Invasive Tree Species on Alabama Forestland
Authors: Hussain Anwar , Sun Changyou , Zhou Xiaoping , Munn Ian A. 
Published: April 2024

Abstract
The spread of invasive tree species has caused increasing harm to the environment. This study was motivated by the considerations that earlier studies generally ignored the role of economic factors related to the occurrence and abundance of invasive species, and empirical analyses of invasive trees on forestland have been inadequate. We assessed the impact of ecological and economic factors on the occurrence and number of invasive tree species on Alabama forestland since 1990. Count data models were used to analyze the 2004 Alabama Forest Inventory Analysis (FIA) data. The proportion of FIA plots with invasive species was 1.06% in 1990, 1.24% in 2000, and 1.35% in 2004. Occurrence of invasive trees on a plot depended on forest type (e.g., natural pines, planted pines, or oak-pines). Plots with planted pine were 171% less likely to be infested with invasive trees than otherwise similar plots. Number of invasive trees per plot was determined by a wide variety of factors, including site productivity, growing stock, stand age, ecoregion, plot proximity to metropolitan centers, ownership type, and forest management activity. The magnitude of the impact was especially large for the ownership type, with more invasive trees on private forestlands than on public lands. These findings suggest that both ecological and economic factors need to be considered in the prevention and control of invasive species invasion.
Tests of a Dynamic Programming-Based Heuristic for Scheduling Forest Core Area Production over Large Landscapes
Authors: Wei Yu , Hoganson Howard M. 
Published: April 2024

Abstract
Potential simplifying assumptions are presented and tested for applying a heuristic model to schedule production of core area of older forest for the Chippewa National Forest in Minnesota, recognizing approximately 67,000 analysis units and 10 10-year planning periods. The model has strong ties to optimization modeling, utilizing dynamic programming to solve overlapping and linked subproblems. Emphasis of this research is on understanding tradeoffs between solution time and nearness to optimality when large landscapes are modeled. Results show that combinations of model-simplifying assumptions can help maintain an efficient balance between computation time and model optimality. Results are sensitive to values assumed for core area, suggesting that more spatial detail is recognized with higher core area values. Results are compared along an efficiency frontier, where improvements in either computation time or management schedule value cannot be achieved without a loss in the other. Understanding the tradeoff between optimality and computation efficiency is important for model use within a larger iterative system that integrates spatial values with aspatial, forestwide management constraints.
Tradeoffs in Overstory and Understory Aboveground Net Primary Productivity in Southwestern Ponderosa Pine Stands
Authors: Sabo Kyla E. , Hart Stephen C. , Sieg Carolyn Hull , Bailey John Duff 
Published: April 2024

Abstract
Previous studies in ponderosa pine forests have quantified the relationship between overstory stand characteristics and understory production using tree measurements such as basal area. We built on these past studies by evaluating the tradeoff between overstory and understory aboveground net primary productivity (ANPP) in southwestern ponderosa pine forests at the landscape level and over a gradient of stand structural types and burn histories. We measured overstory and understory attributes in 2004 and 2005 in four stand structural types (unmanaged, thinned, thinned and burned, and low basal area thinned and burned) relative to a stand-replacing wildfire site. Thinning alone and with prescribed burning reduced stand-level wood and total tree production relative to unmanaged stands. Understory (herbaceous) ANPP was highest in wildfire stands and low basal area thinned and burned plots but did not differ among the other stand structural types, apparently because of high residual basal area and relatively uniform tree spacing. Contemporary ponderosa pine forests are low productivity ecosystems that exhibit a threshold response between reductions in tree density and increases in understory production at 5.9 m2 ha. We calculated the slope of the relationship between tree and herbaceous ANPP to be −0.14, which was lower than the values we estimated from other, more productive savanna ecosystems. Our results suggest that to maintain more fire-resistant and hence sustainable southwestern ponderosa pine ecosystems, tree densities need to be substantially reduced from contemporary levels. Large, landscape-level reductions in tree density will decrease total ecosystem production of this forest type, but this reduction will probably be small relative to ecosystem production losses after widespread, stand-replacing wildfires.
Protect Thy Neighbor: Investigating the Spatial Externalities of Community Wildfire Hazard Mitigation
Authors: Butry David , Donovan Geoffrey 
Published: April 2024

Abstract
Climate change, increased wildland fuels, and residential development patterns in fire-prone areas all combine to make wildfire risk mitigation an important public policy issue. One approach to wildfire risk mitigation is to encourage homeowners to use fire-resistant building materials and to create defensible spaces around their homes. We develop a theoretical model of interdependent household wildfire risk and mathematically introduce two new concepts of the benefits accruing from hazard mitigation: direct and spillover (indirect) damage averted. We explore how firewise communities can best spend and position mitigation resources to maximize the sum of direct and spillover damage averted. Simulating wildfire behavior within a fire-prone community, our results indicate that homeowners' wildfire risk reduction actions can have significant, positive spillover effects on the wildfire risk of neighboring houses. In such cases, individual homeowners may engage in inefficient levels of wildfire risk mitigation when viewed from the community perspective. We use a simulation approach to demonstrate that wildfire risk reduction is most effective when concentrated in houses at the interface of communities and wildlands.
Thinning Effects on Microbial Biomass, N Mineralization, and Tree Growth in a Mid-Rotation Fire-Origin Lodgepole Pine Stand in the Lower Foothills of Alberta, Canada
Authors: Tan Xiao , Chang Scott X. , Comeau Philip G. , Wang Yonghe 
Published: April 2024

Abstract
We examined the effects of precommercial thinning on microbial biomass C and N, rates of microbial respiration and net N mineralization, and tree growth 24 years after thinning of a 22-year-old fire-origin lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.) stand near Edson, Alberta. Treatments were control (unthinned) and manual-thinned (even spacing) to 1,600 trees ha−1 with thinning residue removed. Forest floor and mineral soil (0–10 and 10–20 cm) were sampled on June 15, July 26, and September 25 of the 2002 growing season for the analyses of soil chemical and biological properties, with the last set of incubated samples for determining net N mineralization rates retrieved on May 23, 2003. Forest floor mass was 16 Mg ha−1 lower in the thinned (59 Mg ha−1) than in the unthinned (75 Mg ha−1) plots. Soil moisture content in the forest floor and net N mineralization rates and available N in the mineral soil on most of the sampling dates were higher in the thinned than in the control plots. In the thinned plots, basal area and relative density were 27.7 m2 ha−1 and 54, respectively, and these were still significantly lower than values in the unthinned plots 24 years after treatment. Current annual diameter increment of the largest 1,000 trees ha−1 was greater in the thinned than in the unthinned plots in 2002–2003. Diameter growth was positively correlated with net N mineralization and soil available N. In this stand, thinning still influenced N availability and soil processes with the trees continuing to respond 24 years after thinning.
Estimating Area of Forest Change by Random Sampling of Change Strata Mapped Using Satellite Imagery
Authors: Dymond John R. , Shepherd James D. , Arnold Greg C. , Trotter Craig M. 
Published: April 2024

Abstract
There is worldwide interest in monitoring changes in forest area for carbon budgeting and assessing biodiversity changes. For cost-effective monitoring over large areas, automated mapping is necessary. However, the accuracy of automated mapping is rarely high enough to permit accurate estimation of changes in forest area when there is small change. In this article, we show how accurate area statistics of small change can be achieved by combining automated change mapping with stratified random sampling. The stratified random sampling can be made efficient by exhaustive sampling of a stratum with contiguous areas of apparent change greater than or equal to some lower limit (5 ha in the case presented here) and splitting the forest-to-forest stratum into large and small spectral change. Efficiency of the method is high when the exhaustively sampled stratum contains a high proportion of all real change. A regional example from New Zealand of mapping change in forest area is given. Acceptable accuracy (afforestation is estimated to ±7% of reported afforestation) from acceptable effort (10,702 sample points) is obtained, representing an efficiency gain of 78% (in terms of sample size) over simple random sampling. The method can be applied to national estimation of forest change to the same accuracy with an efficiency gain of approximately 70%. It provides a more rapid alternative to multipurpose forest inventories, which depend on intensive and expensive field data, and has significant implications for carbon accounting at regional and national scales, where rapid production of usable estimates are required for carbon exchange markets.
Seed Viability and Dispersal of the Wind-Dispersed Invasive Ailanthus altissima in Aqueous Environments
Authors: Kaproth Matthew A. , McGraw James B. 
Published: April 2024

Abstract
In mesic forest environments, seeds of wind-dispersed plant species may frequently be deposited in aqueous environments (e.g., lakes and rivers). The consequences of deposition in an aqueous medium depend on whether seed viability is maintained. If seeds survive there, secondary dispersal in water may transport seeds long distances to suitable habitats. Using the exotic species, tree-of-heaven (Ailanthus altissima [Mill.] Swingle), in this study we estimated seed dispersal into water as a function of distance and experimentally tested seed buoyancy, secondary dispersal, and germinability after dispersal in water and on land. We found that biologically significant numbers of seeds disperse directly into water, remain buoyant, and are transported long distances by water. Germination rates for seeds that were kept in aqueous environments (Cheat Lake and the Monongahela River, near Morgantown, WV) were found to be similar to or higher than those in nearby terrestrial controls (F = 10.94, P = 0.0057). Seeds kept in aqueous environments retained high germination rates (94.4 ± 1.1%) even after 5 months. Although A. altissima may not disperse primarily through water environments, this study suggests that secondary dispersal by water is possible and may allow for long-distance dispersal more than two orders of magnitude farther than recorded primary dispersal.
Base–Age Invariant Site Index Models from a Generalized Algebraic Parameter Prediction Approach
Authors: Wang Mingliang , Rennolls Keith , Borders Bruce E. 
Published: April 2024

Abstract
A simple idea is proposed to develop polymorphic base–age invariant models with multiple asymptotes: the asymptotic parameter is taken as the site-specific parameter (χ) and one of the other parameters is taken as dependent on χ as a simple power function. This approach is a constrained form of the generalized algebraic difference approach (GADA) and eliminates the requirement in previous GADA models to obtain an explicit solution for χ: χ just has to be estimated along with other parameters of the model. The approach may be used to adapt base–age specific models, developed in terms of the “parameter prediction” method, to be “base–age invariant.” The new approach and the models it produces are evaluated on data sets for Chinese fir, red alder, and birch, with models being fitted using the “dummy variable” method in which each observed data series has its own site-specific χ parameter. The base–age invariant models developed are superior to their comparable base–age specific models.
GIS-Based Modeling of Pinyon–Juniper Woodland Structure in the Great Basin
Authors: Greenwood David L. , Weisberg Peter J. 
Published: April 2024

Abstract
Pinyon–juniper woodlands are a dominant vegetation type across the Intermountain West, covering an estimated 30 million ha. Increases in density, cover, and aerial extent over recent decades have been associated with altered fire regimes, tree mortality, and reduced understory productivity. In our study we sought to determine how environmental factors influence woodland structure and to exploit such abiotic influences to improve our ability to model woodland structure from digital aerial photography. We developed and applied a methodology for automated tree canopy cover mapping using an object-oriented classifier. The resulting classification was used to scale up stand inventory measurements (0.1 ha) across 11 mountain ranges to a 3,250 km2 area. Predictive models were compared with field-measured values from a validation sample for tree canopy cover, basal area, height, and stand density index. Linear mixed-effects regression models demonstrated consistent relationships between woodland structure attributes and environmental variables. More productive sites supported greater tree densities, whereas less productive sites supported fewer, larger trees. Relatively weak relationships for certain variables (e.g., tree height) suggest that woodland structure-environment relationships are partially obscured by natural disturbances and land use history.