bluuebunny/crossref_metadata_2025 huggingface dataset:
Spatial Scale and Stand Structure in Northern Hardwood Forests: Implications for Quantifying Diameter Distributions
Authors: Janowiak Maria K. , Nagel Linda M. , Webster Christopher R.
Published: April 2024

Diameter distributions are frequently used to describe northern hardwood stand structure and serve as a structural guide for management. Several diameter distribution shapes have been found in managed and unmanaged uneven-aged northern hardwood stands, and it is unclear which patterns are due primarily to natural processes that could be self-perpetuating versus patterns that may be transient or aberrant. Variability in research methods has clouded consistent interpretation of resulting distributions. In this study, we evaluated northern hardwood stands in Michigan to determine how management and sample area affect interpretation of diameter distribution shape. Managed stands had a higher degree of variability in distribution shape and a tendency toward the increasing-q pattern. Unmanaged uneven-aged stands (i.e., old-growth remnants) were predominantly rotated sigmoid in shape. Patterns for each type of management became more consistent as sample area increased. Our data suggest a minimum sample area of 13% of total stand area may be needed to accurately capture diameter distribution shape; in this study that was 0.4 ha of a 3.2-ha sample plot. Additionally, greater heterogeneity in the structure of unmanaged stands resulted in the need for larger sample areas compared with that for managed stands.
Drought-Induced Changes in C and N Stoichiometry in a Quercus ilex Mediterranean Forest
Authors: Sardans Jordi , Peñuelas Josep , Ogaya Romà
Published: April 2024

A 6-year field experiment of drought manipulation was performed in a Mediterranean forest with the aim of determining the effects of the drought predicted by most climate and ecophysiological models on the C and N concentration, accumulation, and stoichiometry in plants and soil. Drought had different effects among dominant species. In Quercus ilex, it increased the C/P ratio in wood and roots, N concentrations in roots and litter, and N/P ratio in wood and roots and decreased the C concentration in roots, C/N ratio in roots and litter, and C/P ratio in litter. In Arbutus unedo, drought increased the N concentration in litter and decreased the N concentration in leaves, thus decreasing N leaf reabsorption. No significant changes in C and N concentrations were found in Phillyrea latifolia. Drought affected the P plant absorption capacity more than that of N (more mobile). There was a general decreasing trend of C and N accumulation in aboveground biomass, with this effect being significant in A. unedo, which accumulated 80% less C and lost 2 kg ha−1 of N in aboveground biomass in drought plots in the period 1999–2005, whereas in this same period it accumulated 9 kg ha−1 of N in total aboveground biomass in control plots. Total soil N and soil organic C increased in droughted soils. The effects of drought on C/N/P stoichiometry and N uptake capacity were different among the three dominant plant species. Q. ilex and A. unedo were more sensitive to drought than P. latifolia. The increase in C/P and N/P ratios in Q. ilex and the decrease in N uptake in A. unedo might decrease their competitive capacity under drought by decreasing water use efficiency. These results altogether indicated slower C and N mineralization and lower N plant capture, N leaf reabsorption, and N accumulation in some dominant plant species in response to drought, thus reducing C and N soil turnover, increasing C and N accumulation in soil, and reducing C and N at the stand level.
Effects of Microsites Created by Selective Harvesting on Growth of Microstegium vimineum in a Central Hardwood Forest
Authors: Marshall Jordan M. , Buckley David S.
Published: April 2024

Disturbances related to silvicultural activities are inevitable and may facilitate the spread of established populations of exotic species. Microstegium vimineum is an annual exotic grass that has spread throughout the eastern United States. Different categories of understory microsites resulting from cutting and the operation of logging machines within three selective harvest units were identified and characterized by measuring several environmental variables. M. vimineum was sown within the microsites categorized. Differences in growth of M. vimineum across different microsites were quantified. As percent canopy cover increased, M. vimineum percent cover, mean length, and mean number of nodes decreased. Also, as litter depth increased, M. vimineum percent cover and stem length decreased. In undisturbed microsites in which M. vimineum was not sown, the exotic grass was not a dominant species, whereas in all other microsites created by logging machine operation M. vimineum was a dominant species whether those areas were sown or colonized by wild populations. These results suggest that unique microsites created by logging may facilitate M. vimineum invasion of central hardwood forests. The apparent connection between soil and canopy disturbance and invasion by M. vimineum provides further impetus for careful planning and use of haul roads and skid trails.
An Estimator of Prediction Error Variance for Projection Equations
Authors: Ni Chengcai , Zhang Lianjun
Published: April 2024

An estimator of prediction error variance for projection equations was derived using the first-order Taylor expansion in this study. The estimator, a modified estimator of the prediction error variance for a population mean regression model, was adapted for situations in which projection equations are applied to unsampled individuals. The estimator accounted for the errors associated with the response variable on the right side of a projection equation, as well as the errors associated with parameter estimation and serial correlations in data. The application of the estimator was demonstrated using the example of 140 trees with diameters measured annually from age 5 to 19. The results indicated that the estimator represented prediction error variance well and was useful for constructing prediction intervals for a given projection equation and providing information on the contributions of the variance components associated with different error sources. It was evident that the error associated with the prior observation of the response variable of a projection equation had an important impact on model predictions for forward projections. Overlooking this variance component may result in significant misestimation for the prediction errors of the projection equation.
Cogongrass (Imperata cylindrica), an Alien Invasive Grass, Reduces Survival and Productivity of an Establishing Pine Forest
Authors: Daneshgar Pedram , Jose Shibu , Collins Alexandra , Ramsey Craig
Published: April 2024

A 27-month-long study was conducted to compare the impacts of Imperata cylindrica (L.) (Beauv.) and native vegetation competition on the productivity of Pinus taeda (L.) seedlings. In March 2003, 1-year-old pine seedlings were planted in the following treatments: vegetation free (VF), native competition (NC), and I. cylindrica (IC) competition. At the end of the study, only 26% of the IC seedlings survived, half of what was observed in the NC treatment. The IC seedlings had significantly smaller root collar diameter than the NC seedlings (P < 0.0001) after the first growing season and by the end of the third growing season the height and stem volume index were significantly less as well (P < 0.0001). After one full growing season, the NC and IC pine seedlings had 21 and 11.5% of the total biomass of the VF seedlings, respectively. After three growing seasons, the IC pine seedling total biomass was 2.4% of that of the VF seedlings and 18% of that of the NC seedlings (P < 0.0001). The greatest difference was in the pine needle biomass with the IC pine needle biomass being only 11% of that of the NC. During the first growing season, the IC pine seedlings maintained the lowest levels of light-saturated net photosynthesis and stomatal conductance. These results may be explained by reduced amounts of foliar nitrogen and water stress that result from I. cylindrica competition. The pines in the IC treatment had the lowest total foliar surface area and the lowest specific leaf area, which may explain the reduced productivity. Evidence from this study suggests that I. cylindrica competition significantly reduces the productivity and growth of P. taeda seedlings compared with that from native vegetation.
Estimation of Genetic-Gain Multipliers for Modeling Douglas-Fir Height and Diameter Growth
Authors: Gould Peter , Johnson Randy , Marshall David , Johnson Greg
Published: April 2024

Methods were developed to calculate genetic-gain multipliers for use in individual-tree models that predict periodic height and diameter growth of coast Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) in the Pacific Northwest. Genetic-gain multipliers are used in growth models that are typically based on extensive measurements of unimproved or “woods-run” stands, to adjust for the increased growth of stands generated from improved seedlots. First-generation progeny test data from multiple breeding zones in the Northwest Tree Improvement Cooperative were used. Data sets included initial heights and diameters and 5-year growth increments for 10- and 15-year-old trees that were identified by open-pollinated families. Nonlinear mixed-effect models were initially developed to predict the average growth of trees in all families, which, taken together, represented woods-run populations. Phenotypic differences in growth rates were then calculated at the family level. Differences among families in height and diameter growth rates were examined using methods from quantitative genetics and raw phenotypic values. Because gain in total height and diameter at age 10 years is currently the most widely available genetic information for improved Douglas-fir, equations were developed to predict genetic-gain multipliers from family breeding values for these traits. A verification procedure illustrated how incorporating multipliers in growth projections could reduce the mean-square error of predicted growth of selected families.
Regional Applicability of Forest Height and Aboveground Biomass Models for the Geoscience Laser Altimeter System
Authors: Pflugmacher Dirk , Cohen Warren , Kennedy Robert , Lefsky Michael
Published: April 2024

Accurate estimates of forest aboveground biomass are needed to reduce uncertainties in global and regional terrestrial carbon fluxes. In this study we investigated the utility of the Geoscience Laser Altimeter System (GLAS) onboard the Ice, Cloud and land Elevation Satellite for large-scale biomass inventories. GLAS is the first spaceborne lidar sensor that will provide global estimates of forest height. We compared accuracy and regional variability of GLAS height estimates with data from the US Forest Service Inventory and Analysis (FIA) program and found that current GLAS algorithms provided generally accurate estimates of height. GLAS heights were on average 2–3 m lower than FIA estimates. To translate GLAS-estimated heights into forest biomass will require general allometric equations. Analysis of the regional variability of forest height-biomass relationships using FIA field data indicates that general nonspecies specific equations are applicable without a significant loss of prediction accuracy. We developed biomass models from FIA data and applied them to the GLAS-estimated heights. Regional estimates of forest biomass from GLAS differed between 39.7 and 58.2 Mg ha−1 compared with FIA.
A Review of Forest Succession Models and Their Suitability for Forest Management Planning
Authors: Taylor Anthony R. , Chen Han Y. H. , VanDamme Laird
Published: April 2024

Successful implementation of ecosystem management requires strategic forest management planning, including the ability to forecast future forest composition. With advances in ecological modeling, many forms of succession models are available. In this review, we provide a broad synthesis of the methods used to model forest succession and discuss their suitability for strategic forest management planning. Qualitative models underpin theoretical understanding of forest succession but require expression in more formal quantitative forms to be applicable to strategic planning. Quantitative modeling methods can be differentiated as empirical or mechanistic. Empirical models rely on observational data of successional change. Mechanistic models rely on knowledge of underlying ecological processes to simulate succession. Hybrid mechanistic models represent a compromise in ecological modeling between empirical robustness and theoretical understanding. With their increased flexibility for scenario planning and enhanced representation of ecosystem processes, hybrid models are well suited to addressing the multiple environmental and social factors increasingly being considered under ecosystem management. However, empirical models still remain a suitable and practical alternative because hybrid models require increased resources to initialize, operate, and interpret; emphasize understanding rather than prediction; and assume that the modeled processes they represent are adequately understood.
Estimating Current Forest Attributes from Paneled Inventory Data Using Plot-Level Imputation: A Study from the Pacific Northwest
Authors: Eskelson Bianca N.I. , Temesgen Hailemariam , Barrett Tara M.
Published: April 2024

Information on current forest condition is essential to assess and characterize resources and to support resource management and policy decisions. The 1998 Farm Bill mandates the US Forest Service to conduct annual inventories to provide annual updates of each state's forest. In annual inventories, the sample size of 1 year (panel) is only a portion of the full sample and therefore the precision of the estimations for any given year is low. To achieve higher precision, the Forest Inventory and Analysis program uses a moving average (MA), which combines the data of multiple panels, as default estimator. The MA can result in biased estimates of current conditions and alternative methods are sought. Alternatives to MA have not yet been explored in the Pacific Northwest. Data from Oregon and Washington national forests were used to examine a weighted moving average (WMA) and three imputation approaches: most similar neighbor, gradient nearest neighbor, and randomForest (RF). Using the most recent measurements of the variables of interest as ancillary variables, RF provided almost unbiased estimates that were comparable to those of the MA and WMA estimators in terms of root mean square error.
Sources of Variation in the Self-Thinning Boundary Line for Three Species with Varying Levels of Shade Tolerance
Authors: Weiskittel Aaron , Gould Peter , Temesgen Hailemariam
Published: April 2024

The species self-thinning boundary line has been widely analyzed with a variety of statistical techniques. Most previous studies in the forestry literature have reported that the relationship does not differ across a range of stand and site factors, but these studies have primarily used statistical techniques that make model fitting subjective or interpretation of covariate significance difficult. There is growing evidence that the use of stochastic frontier analysis is an effective statistical means for objectively fitting the species self-thinning boundary line, offering the opportunity to test the influence of additional covariates. Using extensive even-aged coastal Douglas-fir (Pseudotsuga menziesii var. menziesii [Mirb.] Franco), western hemlock (Tsuga heterophylla), and red alder (Alnus rubra Bong.) data sets in the Pacific Northwest, we examined the assumption that the intercept and slope of the species self-thinning boundary line are insensitive to stand and site factors. Likelihood ratio tests indicated that site index, stand origin (natural versus planted), and purity (proportion of basal area in the primary species) significantly influenced the species self-thinning boundary line intercept for each of the species examined in this study. In Douglas-fir and western hemlock, the slope of the self-thinning boundary was also dependent on stand origin as well as site index in the case of Douglas-fir. Fertilization did not significantly influence the intercept or slope of the species self-thinning line for Douglas-fir and western hemlock. In addition, the inclusion of site aspect and dryness index marginally improved the red alder model of self-thinning, but neither site soil nor climatic variables improved the models for western hemlock and Douglas-fir. Thus, the species self-thinning boundary line can vary significantly among stands, and its variation is driven by several distinct factors; stochastic frontier analysis is an effective tool for identifying these factors.
Effects of Stand Regeneration Management Regimes and Age on Genetic Structure of Quercus aquifolioides (Sclerophyllous Oak) in Southwestern China
Authors: Wang Zhongsheng , Liu Hong , Wei Na , Xu Weixiang , An Shuqing , Liu Shirong
Published: April 2024

As a representative relict forest type, the sclerophyllous oak (Quercus aquifolioides Rehd. et Wils.) forests in the Himalayas-Hengduanshan Mountains of China have been either nearly completely destroyed or heavily fragmented, mostly due to the long-lasting overexploitation by local human population. To evaluate the effect of current silvicultural treatments on regeneration of sclerophyllous oak, we compared inter simple sequence repeats, measures of genetic variation of this species regenerating in three types of stands: natural old-growth oak forest, clearcut spruce plantation, and clearcut naturally regenerated stands in the Miyaluo area, western Sichuan Province of China. Results showed that populations of Q. aquifolioides in the old-growth stands displayed the highest level of genetic diversity, whereas populations in the clearcut naturally regenerated stands had the lowest. In addition, we found that populations in the older spruce plantations (e.g., stands ≥50 years old) were genetically more diverse than those in the younger sites. These findings had the following immediate implications: forest clearcuts had significantly reduced genetic variability within populations of Q. aquifolioides; artificial reforestation of spruce after clearcut could promote the recovery of genetic diversity in Q. aquifolioides, especially in the older stands; and severe human and livestock disturbances hindered the recovery of genetic diversity of Q. aquifolioides in the naturally regenerated stands. We recommend active thinning in spruce plantations (at approximately age 30-40 years) via selective logging at times of rapid height growth and crown closure to promote multistoried stand structures and canopy gaps suitable for the survival and growth of Q. aquifolioides. Finally, we recommend strict management control in the naturally regenerated stands to limit the utilities of these stands by humans and their livestock to facilitate the recovery of Q. aquifolioides genetic diversity.
Evaluating Approaches for Solving the Area Restriction Model in Harvest Scheduling
Authors: Goycoolea Marcos , Murray Alan , Vielma Juan Pablo , Weintraub Andres
Published: April 2024

We survey three integer-programming approaches for solving the area restriction model for harvest scheduling. We describe and analyze each of these approaches in detail, comparing them both from a modeling and computational point of view. In our analysis of these formulations as modeling tools, we show how each can be extended to incorporate additional harvest scheduling concerns. In our computational analysis we illustrate the strengths and weaknesses of each formulation as a practical optimization tool by studying harvest scheduling in four North American forests.
Adaptive Decision Analysis in Forest Management Planning
Authors: Leskinen Pekka , Hujala Teppo , Tikkanen Jukka , Kainulainen Tuomo , Kangas Annika , Kurttila Mikko , Pykäläinen Jouni , Leskinen Leena
Published: April 2024

Societal responsibilities of forestry have diversified, and criteria other than those related to wood production have been given more weight. Demands for forest management planning methods have changed in line with the changes in the operational environment. Thus, forest planners are facing a growing demand for more versatile and customer-oriented decision aid systems and practices in which the data are cost effectively acquired and used. So far, forest planning research has concentrated mainly on the general development of multiobjective and participatory planning methods in the numerical framework. This focus has unintentionally led to practices for which the decision analysis process is often controlled only by the technical needs of the planning methods in a unified setting, independently of the problem characteristics. However, it is important to adapt the use of planning methodologies to each planning problem and use the available information about important variables efficiently. In this article, we introduce a theoretical and methodological framework for adaptive decision analysis (ADA) for forest management planning. In ADA, different decision-support service options, comprising both qualitative and quantitative components, are maintained and carried out flexibly in each planning case with the aid of an adapting processor and feedback management, resulting in computational, social, and organizational learning.
Early Growth Responses of Lodgepole Pine and Douglas-Fir to Soil Compaction, Organic Matter Removal, and Rehabilitation Treatments in Southeastern British Columbia
Authors: Tan Xiao , Curran Michael , Chang Scott , Maynard Douglas
Published: April 2024

Effects of soil compaction, organic matter removal, and rehabilitation on lodgepole pine (Pinus contorta Dougl. ex. Loud.) and Douglas-fir (Pseudotsuga menziesii var. menziesii) were studied after three growing seasons in a long-term soil productivity study established on three calcareous soils in southeastern British Columbia. Effects of soil compaction and organic matter removal on tree growth were site and species specific. Moderate soil compaction increased the diameter and height increment of both species within the stem-only harvest treatment on all three sites, particularly at the coarser textured site (Emily Creek). Compaction tended to reduce tree mortality. Growth of both species was reduced by forest floor removal in the noncompacted soil at Mud Creek and Emily Creek and by whole-tree harvest in the moderately compacted soil at Mud Creek and Kootenay East, possibly due to treatment-induced water limitation. Whole-tree harvest and forest floor removal stimulated lodgepole pine and Douglas-fir growth in the noncompacted soil at Kootenay East. The rehabilitation treatment (established by tilling a heavily compacted soil) reduced lodgepole pine tree mortality on all sites and increased rootcollar diameter and height increment at Mud Creek and Kootenay East. Our findings may provide early growth indication and help assess long-term tree growth trends at these and other long-term soil productivity or related sites.
Approaches for Modeling Vertical Distribution of Maximum Knot Size in Black Spruce: A Comparison of Fixed- and Mixed-Effects Nonlinear Models
Authors: Kershaw John A. , Benjamin Jeff G. , Weiskittel Aaron R.
Published: April 2024

Both linear and nonlinear hierarchical mixed-effects models have been used in recent years to analyze nested data sets. These types of models are effective for partitioning variance between hierarchical levels and increasing model flexibility. Models of knot size and distribution have been developed for several commercially important conifer species. Modeling knots is particularly amendable to the mixed-models approach as they are inherently nested at multiple levels including the individual whorl, tree, and stand levels. Although mixed models are effective for addressing hierarchical nesting of data, in this study we contend that improvements achieved by inclusion of mixed effects can be effectively negated with the use of an appropriate model form. This contention is presented as a case study on the development of a maximum knot size model for plantation-grown black spruce in Ontario (Picea mariana [Mill.] BSP). With a naive and simple model form, the nonlinear mixed-effects approach was significantly superior to comparable generalized nonlinear models as the root mean square error was 16% lower. In contrast, when a model form that accounted for primary covariates with a robust model form was used, difference in root mean square error between nonlinear mixed-effects and generalized nonlinear models was approximately 6%. In addition, graphic techniques for exploring distributions of random effects are presented and discussed. Mixed models are effective tools, but, as illustrated by this case study, their limitations need to be recognized and use of mixed models should not precede development of sound model forms.
Cavity Size and Copper Root Pruning Affect Production and Establishment of Container-Grown Longleaf Pine Seedlings
Authors: Sword Sayer Mary Anne , Haywood James D. , Sung Shi-Jean Susana
Published: April 2024

With six container types, we tested the effects of cavity size (i.e., 60, 93, and 170 ml) and copper root pruning on the root system development of longleaf pine (Pinus palustris Mill.) seedlings grown in a greenhouse. We then evaluated root egress during a root growth potential test and assessed seedling morphology and root system development 1 year after planting in central Louisiana, USA. Seedling size was increased by copper root pruning in small cavities but was unaffected by this treatment in larger cavities. Before planting, copper root pruning increased taproot and secondary lateral root dry weights at the expense of primary lateral root dry weight and increased root growth potential in the top 5 cm of the root plug. Across treatments, survival was 97%, and all seedlings were in the grass stage. Of the lateral root dry weight that elongated during the first year after planting, 33% more occurred in the upper 5 cm of soil when seedlings were treated with copper. Within each cavity size, copper root pruning did not affect the general morphology of 1-year-old seedlings. However, relationships between root collar diameter and root egress by depth indicated that this treatment has the potential to increase the range of cavity sizes used for seedling production.
Fifty Years of Fertilization Experiments on Pinus pinaster in Southwest France: The Importance of Phosphorus as a Fertilizer
Authors: Trichet Pierre , Bakker Mark R. , Augusto Laurent , Alazard Pierre , Merzeau Dominique , Saur Etienne
Published: April 2024

Data from 50 years of fertilization trials on Maritime pine (Pinus pinaster) were compiled to investigate how growth was affected by fertilization or improved nutrient availability. The results demonstrated that only trees fertilized with phosphorus (P) fertilizers showed an overall improvement in productivity. The effects were significant mainly at wetter sites and were less effective at drier sites. The form of P fertilizer does not seem to be important, and a rate of about 17–35 kg of P ha−1 applied as a single dose at stand establishment was found to be sufficient to obtain a significant improvement in growth. Foresters can expect an increase of 20–40% cumulative volume at rotation age or a reduction of 4–5 years in rotation length due to fertilization with P. The duration of the effect of P fertilization on the annual increment varied (up to 20 years after application in the best cases). The high P-fixing capacity of these soils appears to be the most important factor in explaining differential responsiveness to P fertilizers, but stand developmental stage or the appearance of other limitations such as nitrogen may also explain the decline in the effectiveness of P fertilization with age.
Long-Term Effects of Site Preparation Treatments, Complete Competition Control, and Repeated Fertilization on Growth of Slash Pine Plantations in the Flatwoods of the Southeastern United States
Authors: Zhao Dehai , Kane Michael , Borders Bruce , Harrison Mike
Published: April 2024

Data through age 26 from a well-designed study established in 1979 were analyzed with a repeated-measures analysis of variance approach to evaluate effects of site preparation treatments, complete competition control, and repeated fertilization on growth of slash pine (Pinus elliottii Engelm.) plantations on Spodosols and non-Spodosols in the flatwoods region of southern Georgia and northern Florida. Complete and sustained vegetation control and repeated fertilization consistently and significantly increased slash pine productivity, with greater responses occurring on Spodosols than on non-Spodosols; their combination had less than additive effects on Spodosols and additive effects on non-Spodosols. Complete and sustained vegetation control resulted in greater cumulative responses than repeated fertilization over more than 20 years, and then the gains from repeated fertilization had caught or surpassed the gains from complete vegetation control. Bedding resulted in significant responses in the early ages. Burning improved stand basal area and volume growth rather than average tree height and dbh on non-Spodosols and had little effect on Spodosols. Chopping had no significant effect on either soil group. Results of this study emphasize the need for site-specific silvicultural prescriptions.
Estimating Forest Attributes Using Observations of Canopy Height: A Model-Based Approach
Authors: Mehtätalo Lauri , Nyblom Jukka
Published: April 2024

An airborne laser scanner can be used to make observations of canopy height at given locations within a forest stand. In recent years, foresters have developed methods to extract information on forest attributes, such as stand density and size distribution of the trees, from laser data for forest inventory purposes. These methods are based on empirical relationships rather than on theory about how observations are generated by tree canopies. We recover the relationship between canopy height and forest attributes, based on assumptions about the shape of a single tree crown, the distribution of tree height, and the spatial distribution of tree locations. This work improves our understanding of how stand characteristics are related to observations collected by airborne laser scanners and links the problem to the theory of germ-grain models and random closet sets in spatial statistics. Furthermore, we use the derived relationship to develop a model-based approach for estimating stand density and distribution of tree heights using observations of canopy height. A simulation study showed that the method is capable of producing fairly accurate estimates for the number of stems and mean tree height, yielding only slight biases in mean tree height and stand density.
Motivations and Land-Use Intentions of Nonindustrial Private Forest Landowners: Comparing Inheritors to Noninheritors
Authors: Majumdar Indrajit , Laband David , Teeter Lawrence , Butler Brett
Published: April 2024

The documented importance of intergenerational human capital transfers in agriculture generally gives us reason to suspect that such transfers may be important in a forestry context and that there may be important implied differences between first-generation woodland owners and multigeneration woodland owners with respect to their motivations and future intentions. In turn, knowledge of the motivations and intentions of nonindustrial private landowners may be extremely important because such knowledge may be vital in terms of our ability to predict future timber supply and the availability of nontimber amenities. Also, the effectiveness of public policies targeting nonindustrial private forest landowners may depend critically on their motivations and intentions. In this article, we analyzed 8,373 responses to the National Woodland Owner Survey to compare characteristics, motivations, and intentions of multigeneration forest landowners against those of single-generation forest landowners. In brief, we found there were significant differences in their motivations and management behavior; inheritors are more active forest managers and manage for both timber and nontimber forest products more aggressively than noninheritors who typically value esthetics, privacy, protection of biodiversity, and nonhunting recreation.
Terrain Trafficability Prediction with GIS Analysis
Authors: Suvinen Antti , Tokola Timo , Saarilahti Martti
Published: April 2024

The aim of this article is to test a GIS-based model for predicting terrain trafficability. The resistance forces restricting the movement of a forest tractor are estimated using a digital soil map, a 25 × 25-m digital elevation model (DEM) and an improved elevation model. Virtual total resistances along the 1,150-m test track were measured using the controller area network (CAN) bus-based technique. Rolling resistance prediction based on the soil type map was quite successful on frictional soils, but the predictions were clear underestimations on cohesive soils because the characteristics of Finnish soil types as substrates for vehicle motion are not well known. The 25 × 25-m DEM seems to be too inaccurate to predict the slope resistance and total resistance, whereas the results obtained with the improved DEM support the null hypothesis that the prediction is adequate enough from a terramechanical point of view and that the method could be used as a tool for predicting terrain trafficability.
Fertilization and Seeding Effects on Vegetative Cover After Wildfire in North-Central Washington State
Authors: Peterson David W. , Dodson Erich K. , Harrod Richy J.
Published: April 2024

Land surface treatments are often applied after severe wildfires to mitigate runoff and erosion threats. However, questions remain about treatment effectiveness, even as treatment costs continue to rise. We experimentally evaluated the effects of seeding and fertilization treatments on vegetative and total soil cover for two growing seasons after the Pot Peak wildfire in the eastern Cascade Mountains. Without treatments, vegetative cover averaged 15% the first year and 27% the second year after wildfire. Fertilization significantly increased vascular plant cover and reduced bare soil area in both years, but differences between low and high fertilization levels were not significant. Fertilization also increased cryptogam cover. Seeding alone was generally ineffective; however, the combination of fertilization with a seed mixture containing the native forb, yarrow (Achillea millefolium L.), produced the highest vascular plant cover and lowest bare soil area. Our results suggest that fertilization may be more effective than seeding, probably providing a degree of protection from erosion, especially the second year after fire. However, treatment effectiveness must be evaluated in context against costs and potential ecosystem impacts.
An Evaluation of Spatial Autocorrelation and Heterogeneity in the Residuals of Six Regression Models
Authors: Zhang Lianjun , Ma Zhihai , Guo Luo
Published: April 2024

Spatial effects include spatial autocorrelation and heterogeneity. Ignoring spatial effects in a modeling process causes misleading significance tests and suboptimal model prediction. In this study, we used three forest plots with different spatial patterns of tree locations (i.e., clustered, random, and regular patterns) to investigate the spatial distributions and heterogeneity in the model residuals from six regression models with the ordinary least squares (OLS) as the benchmark. Our results revealed that when significant spatial autocorrelations and variations existed in the relationship between tree height and diameter, as in the softwood plot (clustered) and hardwood plot (random), OLS was not appropriate for modeling the relationship between tree variables. Spatial regression models (i.e., spatial lag and spatial error models) were effective for accounting for spatial autocorrelation in the model residuals, but they were insufficient to deal with the problem of spatial heterogeneity. It was evident that the model residuals in both spatial lag and spatial error models had a similar pattern and magnitudes of spatial heterogeneity at spatial scales different from those of the OLS model. In contrast, the linear mixed model and geographically weighted regression incorporated the spatial dependence and variation into modeling processes, and consequently, fitted the data better and predicted the response variable more accurately. The model residuals from both the linear mixed model and geographically weighted regression had desirable spatial distributions, meaning fewer clusters of similar or dissimilar model residuals over space.
Microhabitat Selection of Bark-Foraging Birds in Response to Fire and Fire Surrogate Treatments
Authors: Farris Kerry L. , Zack Steve , Amacher Andrew J. , Pierson Jennifer C.
Published: April 2024

We examined the short-term response of the bark-foraging bird community to mechanical thinning, prescribed fire, and thinning/prescribed fire combination treatments designed to reduce fuel loads at study sites throughout the continental United States as part of the national Fire and Fire Surrogate (FFS) project. We modeled the effects of study site, treatment, treatment category, and time since treatment on the foraging encounter rate of four individual species (red-breasted nuthatch [Sitta canadensis], mountain chickadee [Poecile gambeli], hairy woodpecker [Picoides villosus], and brown creeper [Certhia americana]) and assessed the relative importance of several tree and snag characteristics in the selection of foraging trees by these same species. The foraging encounter rate of all four species responded inconsistently across both treatment categories and study sites. Substrate diameter was the strongest and most consistent characteristic positively influencing the selection of foraging habitat structures for all species across all treatment categories. Other influential variables included the presence of bark beetles for red-breasted nuthatches, hairy woodpeckers, and brown creepers in control and burn-only treatment areas and tree species for brown creepers in burn-only and thin-only treatment areas. Although this study did not detect any major negative treatment response by any species, our results suggest that there is substantial variability in the reaction of this particular bird community to fuel reduction treatments and that managers may need to evaluate the effects of these treatments on a site-by-site and species-by-species basis.
Short-Term Response of Ground-Dwelling Arthropods to Prescribed Fire and Mechanical Fuel Reduction in a Southern Appalachian Upland Hardwood Forest
Authors: Greenberg Cathryn H. , Forrest T. G. , Waldrop Thomas
Published: April 2024

As part of the multidisciplinary National Fire and Fire Surrogate Study, we used drift fences with pitfall traps to determine how three fuel reduction treatments affected ground-dwelling macroarthropods in the southern Appalachian Mountains of North Carolina. Four experimental units, each >14 ha, were contained within each of three replicate blocks. Treatments were (1) prescribed burning, (2) mechanical felling of shrubs and small trees, (3) mechanical felling + burning, and (4) untreated controls. Mechanical understory felling was conducted in winter 2001–2002, and prescribed burning was conducted in March 2003. Mechanical felling + burning resulted in greater canopy openness compared with the other treatments as a result of hotter fires and elevated levels of subsequent tree mortality. Burning reduced leaf litter depth in both burned treatments by >80%. We captured 6,776 individual macroarthropods (460 g of dry biomass) within 22 identified orders and 59 identified families. Coleoptera and Hymenoptera were numerically dominant (27.3 and 25.9%, respectively); Lepidoptera larvae also were a dominant component of dry biomass (37%). We found no differences among treatments in the relative abundance or dry biomass of total ground-dwelling macroarthropods or within most orders; Hymenoptera (predominantly Formicidae) dry biomass was greater with mechanical felling + burning than with mechanical felling. Total relative abundance and dry biomass were low in spring and higher in late summer. Our results indicate that prescribed burning and mechanical fuel reduction treatments conducted in winter or early spring have little impact on the community composition, relative abundance, or biomass of total arthropods or most arthropod orders and families, at least in the short term. However, because we did not use a killing agent, our trapping method probably undersampled macroarthropods that could climb or fly from traps, and results for those groups should be interpreted cautiously. Our study suggests that the fuel reduction methods studied may be used as a land management tool in upland hardwood forest with little effect on macroarthropod communities or the ground-dwelling arthropod prey base for vertebrates.
On Conducting a Multisite, Multidisciplinary Forestry Research Project: Lessons from the National Fire and Fire Surrogate Study
Authors: McIver James Duncan , Weatherspoon Charles Phillip
Published: April 2024

The National Fire and Fire Surrogate (FFS) study is described, from its conceptual stage in early 1996 to the completion of its short-term phase in May 2006. Comprising 12 sites, the FFS study is a comprehensive multidisciplinary experiment designed to evaluate the economics and ecological consequences of alternative fuel reduction treatments in seasonally dry forests of the United States. The FFS study uses a common experimental design across the 12-site network, with each site consisting of a fully replicated experiment that compares four treatments: an unmanipulated control, prescribed fire, mechanical treatments, and mechanical + fire. We measured operational costs and variables within several components of the ecosystem, including vegetation, the fuel bed, soils, bark beetles, tree diseases, and wildlife in the same 10-ha experimental units. This design allowed us to assemble a fairly complete picture of ecosystem response to treatment at the site scale, and to compare treatment response across sites representing a wide variety of conditions. We offer the FFS study as a model for conducting a complex multidisciplinary management experiment focused on natural resource issues. We then discuss why we believe it was successful and how it could be improved. We discuss seven key features that we believe must be considered to conduct a successful multidisciplinary experiment: funding, design, partnerships, organization, standardization, data management, and outreach. Although experiments such as the FFS study are difficult to execute, they may be our best hope for answering some of our more pressing questions in the field of natural resource management.
Thinning and Burning in Dry Coniferous Forests of the Western United States: Effectiveness in Altering Diameter Distributions
Authors: Youngblood Andrew
Published: April 2024

Western United States land managers are conducting fuel reduction and forest restoration treatments in forests with altered structural conditions. As part of the National Fire and Fire Surrogate (FFS) study, thinning and burning treatments were evaluated for changing forest structure. Shifts between pretreatment and posttreatment diameter distributions at seven western FFS study sites were determined by assessing live tree diameter frequency distributions and the 10th and 90th percentile and mean diameter. Diameter distributions were based on 31,517 live trees within 76 pretreatment units and 25,061 live trees within 85 posttreatment units. Cross-site comparisons were made using meta-analysis. Values for 10th percentile diameter increased at two sites, values for 90th percentile diameter increased at six sites, and values for mean diameter increased at five sites (P < 0.05) after active treatments (thin, burn, or thin + burn) compared with control sites. Across the seven western FFS study sites, the overall effect size of the thin treatment increased for 90th percentile and mean diameter, the overall effect size of the burn treatment increased for 10th percentile, 90th percentile, and mean diameter, and the overall effect size of the thin + burn treatment increased for 10th percentile, 90th percentile, and mean diameter. This work indicates that although each of the active treatments was effective in shifting diameter distributions toward larger trees, no single treatment or entry will probably mitigate nearly a century of fire exclusion and fuel accumulation in dry coniferous forests of the western United States.
Effects of Fire and Fire Surrogate Treatments on Bark Beetle-Caused Tree Mortality in the Southern Cascades, California
Authors: Fettig Christopher , Borys Robert , Dabney Christopher
Published: April 2024

We examined bark beetle responses to fire and fire surrogate treatments 2 and 4 years after the application of prescribed fire in a mixed-conifer forest in northern California. Treatments included an untreated control (C), thinning from below (T), and applications of prescribed fire (B) and T + B replicated three times in 10-ha experimental units. A total of 1,822 pine and fir trees (5.1% of all trees) were killed by bark beetles. Mountain pine beetle (Dendroctonus ponderosae Hopkins) was found infesting ponderosa pine (Pinus ponderosa Dougl. ex Laws.), sugar pine (Pinus lambertiana Dougl.), and lodgepole pine (Pinus contorta Dougl. ex Loud.); western pine beetle (Dendroctonus brevicomis LeConte) was found infesting ponderosa pine; and fir engraver (Scolytus ventralis LeConte) was found infesting white fir (Abies concolor [Gord. & Glend.] Lindl. ex Hildebr.). Significantly higher rates of bark beetle-caused tree mortality occurred on B (9.2%) than on C (3.2%), T (<1%), or T + B (3.3%) cumulatively during the 4-year period. A total of 723 pines (4.4% of all pines) were killed by bark beetles, primarily mountain pine beetle. Attacks resulted in significantly more pine mortality on B (5%) than on C, T, or T + B (all <1%) 2 years after the application of prescribed fire. No significant treatment effects were found during the second sample period or cumulatively during the 4-year period. A total of 1,098 white fir trees (5.8% of all white fir) were killed by the fir engraver. Attacks resulted in significantly higher rates of fir mortality on T + B than on T during both sample periods but not cumulatively during the 4-year period. Overall, bark beetle-caused tree mortality was concentrated in the smaller diameter classes. The implications of these and other results to forest management are discussed.
Effectiveness of Litter Removal to Prevent Cambial Kill-Caused Mortality in Northern Arizona Ponderosa Pine
Authors: Fowler James F. , Sieg Carolyn Hull , Wadleigh Linda L.
Published: April 2024

Removal of deep litter and duff from the base of mature southwestern ponderosa pine (Pinus ponderosa Laws.) is commonly recommended to reduce mortality after prescribed burns, but experimental studies that quantify the effectiveness of such practices in reducing mortality are lacking. After a pilot study on each of four sites in northern Arizona, we monitored 15–16 sets of 8 matched trees on areas designated to be burned and adjacent not-burned sites and randomly assigned one of four litter and duff removal (to mineral soil) treatments: (1) rake to a distance of 23 cm from the bole, (2) leaf blow to a distance of 23 cm, (3) rake to a distance of 1 m, and (4) no litter or duff disturbance or removal. By 3 years postburn, no trees had died because of any of the treatments, but litter and duff removal prevented most cambial kill. However, 17% of the burned, no removal trees had some cambial kill. Litter and duff removal to 23 cm was as effective in preventing cambial kill and bole char as removal to 1 m, and there was no difference between removal by raking versus leaf blower removal. These results suggest that litter and duff removal is not needed to prevent ponderosa pine mortality after fall prescribed burns, but removal to 23 cm is adequate to prevent spots of cambial kill or moderate bark char.