Modeling Dominant Height Growth of Cedar (Cedrus libani A. Rich) Stands in Turkey - Ramazan Özçelik; Quang V Cao; Esteban Gómez-García; Felipe Crecente-Campo; Ünal Eler (Forest Science, 2019)
Sustainable forest management requires accurate prediction from a growth and yield system. Such a system relies heavily on some measure of site productivity, which is often the site index. A model was developed for predicting dominant height growth and site index of even-aged cedar (Cedrus libani A. Rich.) stands in Turkey. Stem-analysis data from 148 trees were used for model development and validation. Six dynamic height–age equations were derived using the generalized algebraic difference approach (GADA). Autocorrelation was modeled by expanding the error term as an autoregressive process. Based on numerical and graphical analysis, a GADA formulation derived from the Chapman–Richards model was selected. Based on relative error in dominant height prediction, 80 years was selected as the best reference age. The resulting equation provided the best compromise between biological and statistical aspects and, therefore, is recommended for height growth prediction and site classification of cedar stands in Turkey.

Use of Modified Reineke’s Stand Density Index in Predicting Growth and Survival of Chinese Fir Plantations - Xiongqing Zhang; Quang V Cao; Lele Lu; Hanchen Wang; Aiguo Duan; Jianguo Zhang (Forest Science, 2019)
Stand density index (SDI) has played an important role in controlling stand stocking and modeling stand development in forest stands. Reineke’s SDI (SDI_R) is based on a constant slope of –1.605 for the self-thinning line. For Chinese fir plantations, however, it has been reported that the self-thinning slope varied with site and climate, rendering SDI_R questionable. Remeasured data from 48 plots distributed in Fujian, Jiangxi, Guangxi, and Sichuan provinces were used to develop models for prediction of stand survival and basal area, with SDI_R incorporated as a predictor variable. Also included in the evaluation were growth models based on self-thinning slopes estimated from two groups of sites (SDI_S) or from climate variables (SDI_C). Results indicated that models with climate-sensitive SDI (SDI_C) performed best, followed by SDI_S and SDI_R. The control models without SDI received the worst overall rank. Inclusion of climate-sensitive SDI in growth and survival models can therefore facilitate modeling of the relation between stand density and growth/survival under future climate-change conditions.

Productivity and Cost of Processors in Whole-Tree Harvesting Systems in Southern Pine Stands - Joseph L Conrad; Joseph Dahlen (Forest Science, 2019)
Logging businesses in the US South have not adopted cut-to-length harvesting systems. Adding dangle head processors on the landing of whole-tree harvesting systems may allow southern loggers to achieve some of the advantages of cut-to-length systems (i.e., precise length and diameter measurements) while maintaining high productivity and low costs per ton characteristic of current whole-tree systems. We conducted a designed study of conventional (i.e., feller-buncher, grapple skidder, loader) and processor (i.e., feller-buncher, grapple skidder, processor, loader) systems. Four harvest sites were split, with half of each site harvested by a conventional system and the other half by a processor system. Harvesting productivity was estimated using time-and-motion studies, and costs were estimated using the machine rate method. Cut-and-load costs averaged US$13.57 and US$14.67 ton–1 on the processor and conventional harvests, respectively (P > .10). Cost per ton was elevated on several conventional harvest tracts because of long skidding distances, indicating harvest planning is more important than harvesting system in determining harvesting costs. Processing and loading costs were US$1.70 ton–1 higher on processor harvests, which, combined with restrictive mill quotas being more problematic for processor crews, suggests loggers will require a logging rate premium in order to invest in processors.

White Oak (Quercus alba) Response to Thinning and Prescribed Fire in Northcentral Alabama Mixed Pine–Hardwood Forests - Callie J Schweitzer; Daniel C Dey; Yong Wang (Forest Science, 2019)
Strong white oak sawtimber markets, partially attributed to the stave and cooperage industries, are encouraging forest managers to re-examine silvicultural practices for white oak (Quercus alba). We examined recruitment and retention of white oak in mixed oak–pine stands on the William B. Bankhead National Forest in northcentral Alabama. Stands were subjected to three thinning levels (residual basal areas of 75 ft2/ac, 50 ft2/ac, and no thinning) and three fire frequencies (dormant season burns of none, one, three fires) in a factorial design. Both thinning treatments reduced overstory white oak tree densities, and fire had no effect on densities. For all reproduction height classes, regardless of thinning treatment, three prescribed burns increased white oak densities; thinned and burned stands had larger white oak seedling sprouts than those thinned with no burn. However, white oak reproduction height was primarily less than 2 ft tall, and seedlings larger than 4 ft tall were reduced. Thinning with one fire resulted in the highest densities of large white oak reproduction (4 ft tall up to 1.5 in. dbh). Red maple reproduction was the dominant competitor in all treatments and is positioned to dominate the reproduction cohort without additional tending treatments.

A Growth and Yield Model for Eucalyptus benthamii in the Southeastern United States - Kevin B Hall; Jl Stape; Bronson P Bullock; Doug Frederick; Jeff Wright; Henrique F Scolforo; Rachel Cook (Forest Science, 2019)
In recent Eucalyptus cold-tolerance trials, E. benthamii has shown good growth rates as well as cold tolerance for USDA Plant Hardiness Zones 8 and 9. This study developed growth and yield models for E. benthamii in the southeastern United States. A network of 182 temporary sample plots of E. benthamii ranging in age from 1.5 to 13.3 years was established, and inventory data were collected. Site quality was determined by fitting a polymorphic site index curve, whereas a function for stand basal area based on age, dominant height, and site occupancy was fitted. Stand-level volume and dry-weight biomass prediction equations were fitted as a function of dominant height and basal area. Based on the growth and yield model results, mean annual increments ranged from 26.4 m3 ha–1 year–1 at rotation age 6 years on the best sites to 13.7 m3 ha–1 year–1 at rotation age 10 years on the poorest sites. This is the first published set of management-oriented models for land managers considering planting E. benthamii in the southeastern United States.

Comparing the Slope–Area Threshold for Stream Initiation in Primeval and Managed Forests of Northern Michigan - Christopher J Anderson (Forest Science, 2019)
Forest management and other land uses can alter hydrological pathways and affect stream initiation along draining hillslopes. To evaluate this potential effect, primeval forests at the Huron Mountain Club in northern Michigan were compared to surrounding forest lands historically logged. A total of 59 stream channel heads (19 in primeval forests and 40 in managed forests) were mapped using GPS. Per the slope–area method, channel heads were plotted within a digital elevation model to determine drainage area and local slope, which were used to discern a threshold of channel initiation. A watershed Hydrologic Soil Index (representing the tendency for surface runoff) was also determined and evaluated for its importance for channel formation. Consistent with the slope–area method, a significant relation was detected between drainage area and local slope for both managed (R2 = .29) and primeval forest watersheds (R2 = .56). However, no significant difference in relation was detected between forest types. This was noteworthy because soils mapped in the primeval forests had a significantly higher Hydrologic Soil Index indicating thinner soils more prone to surface runoff. Results suggest that forest management has likely varied throughout the region but has sustained forest drainage densities comparable to primeval forests.

Developing Silvicultural Tools for Managing Mixed Forest Structures in Patagonia - Marina Caselli; Gabriel Ángel Loguercio; María Florencia Urretavizcaya; Guillermo Emilio Defossé (Forest Science, 2019)
Leaf area is an important ecophysiological and silvicultural variable for quantifying the potential production of trees, since it can represent growing space occupancy. At the stand level in mixed forests, productivity is conditioned on how growing space is distributed among different components structure, such as species and strata. In complex structures, traditional forest variables (i.e., basal area) do not allow a good representation of the occupied growing space, whereas leaf area appears as a better indicator. Andean cypress and coihue beech are species of the Andean-Patagonian forests that grow in either pure or mixed stands, presenting high productive potential. The aim of this study was to develop, for each species, leaf area prediction functions through allometric relations and to evaluate the relation between leaf area, volume increment and growing space occupancy. For this purpose, we carried out destructive sampling of individuals of both species in mixed Andean cypress-coihue forests. Results for these species show that leaf area can be reliably estimated by using the models developed in this study. These models, based on sapwood area, tree diameter, and/or height measurements, explain at least 90 percent of variation in leaf area. The functions fitted are a fundamental tool to study the distribution of growth and to formulate management guidelines for mixed forests through the control of growing space occupancy using leaf area index.

Differential Impacts of Emerald Ash Borer (Agrilus planipennis Fairmaire) on Forest Communities Containing Native Ash (Fraxinus spp.) Species in Eastern North America - Joshua J Granger; John M Zobel; David S Buckley (Forest Science, 2019)
Invasion by emerald ash borer (EAB; Agrilus planipennis Fairmaire), an exotic pest, is disrupting natural processes and hindering our ability to conserve genetic diversity and perpetuate ash ecosystem services and functions. The goal of this project was to identify forest communities most at risk in terms of having altered ecosystems following EAB invasion. Using recent data available from the USDA, Forest Service, Forest Inventory and Analysis program, we calculated Shannon–Wiener species diversity index values for forests containing each of the six native ash species found in the eastern United States. These forest communities differed in their species diversity index values, and diversity indices varied across ecosystem provinces and states. In addition, communities containing ashes that are restricted by a narrow range of suitable environmental conditions consistently had lower diversity index values than communities of ash species with greater geographical ranges. Finally, forest stand cohorts (i.e., seedlings, saplings, and canopy trees) had similar species diversity indices across forest communities containing a single ash species. The tree species diversity index values quantified for communities with a single ash species will provide managers with additional information for prioritizing EAB control measures and restoration efforts following EAB invasions.

Dissolved Organic Matter Characteristics and Important Site Factors in a Subtropical Mountain Forest in Central China - Min Wang; Chang Liao; Qiuxiang Tian; Dongya Wang; Yu Wu; Yanan Tang; Feng Liu (Forest Science, 2019)
Dissolved organic matter is important in the vertical and lateral translocation of nutrients in forest ecosystems. However, little is known about the changes in dissolved organic matter concentration and chemical components in ecosystem sources in humid mountain forests. Here, we measured the concentration and chemical components of dissolved organic matter at throughfall, stemflow, litter leachate, runoff, and soil pore water (at depths of 10 cm, 30 cm, and 60 cm) in a subtropical humid mountain forest during two growing seasons. The concentration of dissolved organic carbon and dissolved nitrogen showed a clear monthly trend. The dissolved organic carbon concentration and the proportion of hydrophobic organic acid in the surficial water were higher than those in the soil pore water, and this difference was accompanied by a decrease in the hydrophobic organic acid concentration from the surficial water to the soil pore water. We also found that dissolved organic matter properties in surficial water were related to canopy cover, tree species, litter carbon content, and slope, whereas dissolved organic matter in soil pore water was associated with soil C, N, and P content and pH. In addition, the rainfall pattern is important to the dissolved organic matter concentration and partitioning within the seven sources. These findings showed that the dissolved organic carbon movement from surficial water into soil pore water is a significant component of carbon cycling in forest ecosystems, and this is important in estimating the carbon budget in forest ecosystems.

Managing Understory Fagus grandifolia for Promoting Beech Bark Disease Resistance in Northern Hardwood Stands - Mary Ann Fajvan; Andrea Hille; Richard M Turcotte (Forest Science, 2019)
Many Allegheny hardwood stands contain dense understories of very shade-tolerant American beech, resulting from partial disturbances that have accelerated root sucker development. The low-shade produced by these sprouts hampers silvicultural regeneration efforts to maintain species diversity in new cohorts. An increasing proportion of sprouts result from stressed trees infested with beech bark disease. The clonal sprouts also have a genetic affinity for the disease. A mixture of Accord® and Oust® herbicides, applied to understory vegetation after shelterwood establishment cuts, can significantly reduce understory beech density. Yet, retention of some overstory beech, with demonstrated disease resistance, is ecologically desirable. The root sprouts from these parent trees should also have resistance to the disease. We used broadcast herbicide application to kill understory vegetation after shelterwood harvests in three stands, and tested the effect of herbicide on beech sprouts associated with resistant trees. Eight years after treatment, plots that had received herbicide had similar densities of beech to no-herbicide plots. However, there were significant differences in seedling densities among stands (P = .0303) and species (P = .0014). Our results indicate that there is much temporal variability in regeneration dynamics after treatment. Resistant beech sprouts are still competitive in the long term, even after herbicide application.

Improving Genetic Analysis of Corymbia citriodora subsp. variegata with Single- and Multiple-Trait Spatial-Competition Models - Mariano Agustín Hernández; Juan Adolfo López; Eduardo Pablo Cappa (Forest Science, 2019)
Environmental heterogeneity and/or genetic and environmental competition were quantified on two growth traits, diameter at breast height and total height, and wood density in a progeny trial of Corymbia citriodora subsp. variegata. Three single-trait mixed models with random spatial and/or competition effects were compared to a standard analysis by analyzing fit, dispersion parameters, accuracy of breeding values, genetic gains, and ranking of trees. In addition, a multiple-trait spatial-competition model was fitted to estimate correlations among direct and indirect additive genetic effects, and to explore relations between traits. Single-trait analyses with spatial and/or competition effects outperformed the standard model. However, the performance of these models depended on the sensitivity of each trait to detect each effect. Direct–indirect genetic correlations from the multiple-trait spatial-competition model showed inverse and strong relations among growth traits and wood density, suggesting that growth traits can be affected by competition and environmental heterogeneity, but also wood density might be influenced by these effects. The approach proposed was useful to improve the genetic analysis of the species as well as to gain an understanding of the genetic relations between traits under the influence of environmental heterogeneity and competition.

Modeling Relations between Compacted and Uncompacted Crown Ratio for the Northern United States - James A Westfall; Megan B E Westfall; KaDonna C Randolph (Forest Science, 2019)
Tree crown ratio is useful in various applications such as prediction of tree mortality probabilities, growth potential, and fire behavior. Crown ratio is commonly assessed in two ways: (1) compacted crown ratio (CCR—lower branches visually moved upwards to fill missing foliage gaps) and (2) uncompacted crown ratio (UNCR—no missing foliage adjustment). The national forest inventory of the United States measures CCR on all trees, whereas only a subset of trees also are assessed for UNCR. Models for 27 species groups are presented to predict UNCR for the northern United States. The model formulation is consistent with those developed for other US regions while also accounting for the presence of repeated measurements and heterogeneous variance in a mixed-model framework. Ignoring random-effects parameters, the fit index values ranged from 0.43 to 0.78, and root mean squared error spanned 0.08–0.15; considerable improvements in both goodness-of-fit statistics were realized via inclusion of the random effects. Comparison of UNCR predictions with models developed for the southern United States exhibited close agreement, whereas comparisons with models used in Forest Vegetation Simulator variants indicated poor association. The models provide additional analytical flexibility for using the breadth of northern region data in applications where UNCR is the appropriate crown characteristic.

Compatible Taper and Stem Volume Equations for Five Pine Species in Mixed-Species Forests in Mexico - Gerónimo Quiñonez-Barraza; Dehai Zhao; Héctor Manuel De los Santos-Posadas (Forest Science, 2019)
Ten systems of compatible taper and outside-bark volume equations derived from upper-height-based volume ratio equations were compared with a used segmented-stem system of compatible taper and volume equations. All the systems were simultaneously fitted to cumulative volume data and taper data for Arizona pine, Aztec pine, Durango pine, Mexican white pine, and Smooth-leaved pine species in naturally regenerated mixed-species forests in Mexico. The systems derived from volume ratio equations performed better than the segmented-stem system for most species. The resultant top systems might be easier to implement than the segmented-stem system for predicting upper-stem height, upper-stem diameter, merchantable volume, and total stem volume for considered species.

Exploring Wildfire-Prone Community Trust in Wildfire Management Agencies - Rebecca Rasch; Sarah McCaffrey (Forest Science, 2019)
This research examines how trustworthy wildfire management agencies are perceived to be in five wildfire-prone communities. Trust was most often expressed in the context of agency abilities or competence (calculative trust), whereas distrust was framed in the context of intentions or the belief that the agency is not acting in the best interest of the community (relational trust). Five factors identified as closely tied to an individual’s trust in wildfire agencies are: communication from the agency; perceived relations among different management agencies, as well as between agencies and the public; experiences with wildfire agencies, particularly during wildfire events; experience with prescribed burns; and values or preferences for management actions. Managers hoping to build, maintain, or restore trust with communities may need to work on building a reputation of both competence and intention to act in the best interest of the community. Results indicate that level of trust in agencies varies considerably, both across and within communities, but that applied at the right scale, the wildfire community archetype framework, a method for rapidly identifying the level of adaptive capacity in wildfire-prone communities appears to be a relatively good indicator of the level of trust community members have in an agency’s abilities.

The Influence of Dormancy Break Requirements on Germination and Viability Responses to Winter Submergence in Acorns of Three Bottomland Red Oak (Sect. Lobatae) Species - Tracy S Hawkins (Forest Science, 2019)
The objective of this study was to examine the relation of dormancy break requirements to winter submergence effects on germination and viability in cherrybark, willow, and Nuttall oak acorns. Acorns were submerged in a greentree reservoir and received 0, 21, 42, 63, or 84 days of winter submergence, followed by 8 weeks of incubation in four temperature regimes (15/6°, 20/10°, 25/15°, and 30/20° C). Winter submergence substituted for cold stratification requirements of cherrybark oak acorns, and dormancy break was achieved with 63 days of submergence. Although winter submergence exerted a positive effect on germination in Nuttall and willow oak acorns, dormancy break was not achieved in acorns of either species. Germination percentages were highest in the 30/20° C incubation temperature—cherrybark oak acorns (75–83 percent), followed by Nuttall oak (33–55 percent) and willow oak (14–52 percent). Among treatment combinations, all willow oak nongerminants were viable. Viability loss in cherrybark and Nuttall oak acorns was greatest in the 63- and 84-day treatments. The dynamics of acorn germination in response to winter hydrologic regime is influenced by submergence duration that may, or may not, satisfy dormancy break requirements in acorns of these red oak species.

Modeling Impacts of Bark Beetle Infestations on Forest Visitor Experiences and Intended Displacement - Ingrid E Schneider; Arne Arnberger; Stuart P Cottrell; Eick von Ruschkowski (Forest Science, 2019)
Bark beetle outbreak impacts are occurring at reportedly unprecedented levels. Despite previous research on the aesthetic and economic impacts of terrestrial pest infestations, minimal visitor behavioral response research exists. As beetle infestation progresses, both tree appearance and landscape change can negatively impact visitation and visitor revenue. Given the multiple-use mandate of most forests, this lack of research is surprising. To meet this gap, this study simulated impacts of varied beetle outbreak levels, management approaches, and visitor characteristics on interference with forest visitors’ experience and intended displacement. Visitors at two forested US state park study sites, one with significant bark beetle impact and the other with much less, responded to onsite questionnaires with digitally calibrated photos depicting a variety of beetle-impacted forest scenarios. Up to 80 percent of visitors indicated forest scenarios with significant bark beetle impact would interfere with their experience, and 70 percent reported they would not visit or be displaced. Analyses revealed forest fore- and midground conditions with varying levels of impact significantly predicted both experience interference and displacement. The relative importance of social, biophysical, and managerial conditions differed between models. Results inform management and planning efforts as well as advance understanding of the biophysical and social factors influencing interference and intended displacement.

Asymmetric Competition Can Shape the Size Distribution of Trees in a Natural Tropical Forest - Nicolas Picard (Forest Science, 2019)
The architecture (here, the size distribution combined with the spatial pattern of individuals) of natural forest at demographic equilibrium can be used to infer the demographic processes that drive the forest dynamics. In particular, a constant growth rate and a constant mortality rate for all trees would generate an exponential distribution of their size, whereas the metabolic scaling theory predicts a power distribution. In an undisturbed tropical rainforest in French Guiana, the diameter distribution was significantly steeper than the best-fit exponential distribution and significantly flatter than the best-fit power distribution. A simple individual-based model of forest dynamics with asymmetric competition between trees, where the strength of competition was regulated by a single parameter, was able to predict the observed distribution. Competition drove the forest into a self-organized state with stronger inequalities of size among trees, a lower mean competition index, and a spatial pattern of trees that deviated from complete spatial randomness.

Determination of Moisture Content and Basic Density of Poplar Wood Chips under Various Moisture Conditions by Near-Infrared Spectroscopy - Long Liang; Guigan Fang; Yongjun Deng; Zhixin Xiong; Ting Wu (Forest Science, 2019)
The potential of near-infrared (NIR) spectroscopy coupled with partial least-squares (PLS) regression was used to determine the moisture content and basic density of poplar wood chips. NIR spectra collected from the surface of wood chips were used to develop calibration models for moisture content and basic density predication, and various spectral preprocessing techniques were applied to improve the accuracy and robustness of the prediction models. The models were tested using totally independent sample sets and exhibited acceptable predictive performance for moisture content (coefficient of determination for prediction [R2p] = 0.98 and standard error of prediction [SEP] = 2.51 percent) and basic density (R2p = 0.87 and SEP = 17.61 kg m–3). In addition, the effect of moisture variations on prediction of basic density was investigated based on NIR spectra from wood chips under various moisture levels. The results demonstrated that broad absorption bands from water molecules, especially when free water exists in the cell lumen, overlap with informative signals related to wood properties and weaken the calibration relation between spectral features and basic density. Thus, maintaining wood chips in a low and even moisture state would help achieve reliable estimates of wood density by NIR analysis models.

Associations between Swiss Needle Cast Severity and Foliar Nutrients in Young-Growth Douglas-Fir in Coastal Western Oregon and Southwest Washington, USA - Yung-Hsiang Lan; David C Shaw; Gabriela Ritóková; Jeff A Hatten (Forest Science, 2019)
Swiss needle cast (SNC) is a foliage disease of Douglas-fir (Pseudotsuga menziesii) caused by Nothophaeocryptopus gaeumannii, an ascomycete fungus (Mycosphaerellaceae) that causes tree growth reductions in the Pacific Northwest. The epidemiology of the fungus is generally well known, but the relations between disease expression and foliar nutrition are unclear. In this study, we used data from the Swiss Needle Cast Cooperative research and monitoring plot network in western Oregon and SW Washington to assess associations between SNC severity, carbon, and nine foliage nutrients (nitrogen, Na, K, P, Ca, Mg, Mn, Al, S). Foliage samples were collected from midcrown of selected Douglas-firs from each plot. SNC severity was determined on 2-year-old needles by multiplying disease incidence and fungal reproductive (pseudothecia) density. Disease severity and nutrient relations were determined using linear mixed models. SNC severity showed statistically significant positive trends with concentrations of carbon, nitrogen, Na, K, and S, no relation with concentrations of Ca, Mg, or Al, and slightly negative trends that were not significant for P and Mn. This is the first such analysis of associations between a conifer foliage disease and foliage nutrients across a landscape; subsequently, there is little published literature on how or why these nutrients may interact with disease.

Structural and Compositional Responses to Thinning over 50 Years in Moist Forest of the Northern Rocky Mountains - Chenchen Shen; Andrew S Nelson; Terrie B Jain; Meghan B Foard; Russell T Graham (Forest Science, 2019)
A thinning study was established in 1967 in moist mixed forests on the Priest River Experimental Forest in northern Idaho, USA. The study design included three thinning intensities: low, moderate, and high intensity (1,976, 988, and 494 trees ha–1). This study examined short-term (11 years) and long-term (50 years) thinning effects on residual stand characteristics, growth, and yield. Since regeneration may occur after thinning, understory change was also addressed. Thinning decreased stand density immediately but improved the growth of residual trees. Shade-tolerant species were favored in all the thinnings and dominated 50 years after thinning. Unthinned stands had higher total and merchantable volume than all thinned stands both 11 years and 50 years post treatment. Regeneration and nontree vegetation richness increased shortly after thinning, whereas nontree vegetation cover decreased sharply 50 years after treatment. The stands developed into multistrata forests with shade-tolerant species in both the overstory and understory. This is contrary to current thinning practice favoring shade-intolerant species, but demonstrates the resilience of moist Northern Rockies forests to partial overstory disturbances. In this study, thinning favoring shade-tolerant species in these mixed forests has a more significant effect on forest structure dynamics than timber production.

Black and Chestnut Oak Seedling Response to Glaciated Soil: Implications for Northward Expansion in Response to Climate Warming - Lauren S Pile; Joanne Rebbeck; Patrick H Brose; Robert P Long (Forest Science, 2019)
Species ranges are expected to move northward with climate warming. However, species will likely encounter soil conditions that differ from their historic ranges. Black (Quercus velutina) and chestnut (Q. montana) oaks are expected to do well in climates that are hotter and drier, but it is unknown as to how they respond to soils of different geological histories. At a glaciated and nonglaciated site in northwestern Pennsylvania, we compared the growth, biomass allocation, and mycorrhizal association for black and chestnut oak seedlings at two different levels of light. On nutrient-poor, nonglaciated soils at high light levels, both species had greater growth and biomass accumulation than on nutrient-rich, glaciated soils. However, at low light levels, these responses were greatest on glaciated soils, especially for chestnut oak. Although mycorrhizal association was beneficial on nonglaciated soil at high light levels, low light levels were associated with reduced growth when compared to glaciated soils. In low light and nutrient-poor soils, mycorrhizal association may result in a carbon sink with lower net photosynthesis, as carbon for plant growth is, instead, allocated to the mycorrhizae symbiont. Variable species response to soil types indicates reduced performance for black and chestnut oak seedlings on high-quality glaciated soils especially in high light environments.

Cost and Productivity of Tethered Cut-to-Length Systems in a Dry-Forest Fuel-Reduction Treatment: A Case Study - Joshua Petitmermet; John Sessions; John Bailey; Rene Zamora-Cristales (Forest Science, 2019)
Fuel-reduction treatments on steep slopes across federal forests of the western United States have been limited by the high costs associated with cable logging on steeper slopes combined with poor market prospects for small-diameter material (Bolding 2003, Rummer 2008, Han et al. 2016). The emergence of tethered cut-to-length harvesting systems and small wood markets (e.g., biochar) could decrease costs and increase revenue generated from treatments. Over the course of 3 weeks, we observed both tethered (steeper slopes) and untethered cut-to-length fuel-reduction treatment on the Fremont-Winema National Forest in south-central Oregon and interviewed operators. We used those data to derive and contrast hourly costs and productivity for the harvester and forwarder. This was the first time a tethered harvester and forwarder were used in a fuel-reduction treatment on federal forests in this region. We developed and tested a variety of work time model forms for each machine. The mean utilization rate for the harvester was 64 percent on 17 tethered consolidated corridors but 87 percent on 28 untethered consolidated corridors. Similarly, the forwarder had a mean utilization rate of 76 percent on 30 tethered trips and 89 percent on 114 untethered trips. This reduced utilization rate could be because of the direct effects of tethering, the increased complexities of operations associated with steeper slopes, and the stand characteristics (e.g., lower stand density and tree sweep) associated with steeper slopes. Costs during tethered operations were higher than during nontethered operations, but lower than previous reports using cable logging.

A Jackknife Estimator of Variance for a Random Tessellated Stratified Sampling Design - Steen Magnussen; Thomas Nord-Larsen (Forest Science, 2019)
Semisystematic sampling designs—in which a population area frame is tessellated into cells, and a randomly located sample is taken from each cell—affords random tessellated stratified (RTS) Horvitz–Thompson-type estimators. Forest inventory applications with RTS estimators are rare, possibly because of computational complexities with the estimation of variance. To reduce this challenge, we propose a jackknife estimator of variance for RTS designs. We demonstrate an application with a model-assisted ratio of totals estimator and data from the Danish National Forest Inventory. RTS estimators of standard error were, as a rule, smaller than comparable estimates obtained under the assumption of simple random sampling. The proposed jackknife estimator performed well.

Understory Vegetation Richness and Diversity of Eucalyptus benthamii and Pinus elliottii Plantations in the Midsouth US - Andrea De Stefano; Michael A Blazier; Christopher E Comer; Thomas J Dean; T Bently Wigley (Forest Science, 2019)
In the Western Gulf region of the United States cold-tolerant eucalyptus have been explored as pulpwood feedstock. However, non-native plantations may alter understory species diversity, modifying environmental conditions and soil characteristics. Few studies have compared eucalyptus plantations with native ecosystems to understand the impact on understory vegetation in the United States. In this study, we compared understory plant species richness and diversity during 2014–2016 in (1) slash pine (Pinus elliottii) established in 2008, (2) slash pine established in 2013, and (3) and Camden white gum (Eucalyptus benthamii) established in 2013. Overstory characteristics, soil pH, and soil nutrient concentrations were measured to understand factors that affected understory species richness and diversity. Results indicated a decline in understory species richness over time, with Camden white gum in an intermediate condition between same-age slash pine (highest richness) and older slash pine (lowest richness). Leaf area index, soil pH and K, and tree height were the most important factors influencing understory species richness and diversity. The adoption of fast-growing eucalyptus on these sites will probably accelerate the deterioration of natural habitats and reduce open-condition species in favor of shade-tolerant species, overturning the conservation efforts already put in place by governmental agencies and conservation groups.

A New Site Index Model for Intensively Managed Loblolly Pine (Pinus taeda) Plantations in the West Gulf Coastal Plain - Kynda R Trim; Dean W Coble; Yuhui Weng; Jeremy P Stovall; I-Kuai Hung (Forest Science, 2019)
Site index (SI) estimation for loblolly pine (Pinus taeda L.) plantations is important for the successful management of this important commercial tree species in the West Gulf Coastal Plain of the United States. This study evaluated various SI models for intensively managed loblolly plantations in the West Gulf Coastal Plain using data collected from permanent plots installed in intensively managed loblolly pine plantations across east Texas and western Louisiana. Six commonly used SI models (Cieszewski GADA model, both Chapman-Richards ADA and GADA models, both Schumacher ADA and GADA models, and McDill-Amateis GADA model) were fit to the data and compared. The Chapman-Richards GADA model and the McDill-Amateis GADA model were similar and best in their fit statistics. These two models were further compared to the existing models (Diéguez-Aranda et al. 2006 (DA2006), Coble and Lee 2010 (CL2010)) commonly used in the region. Both the Chapman-Richards GADA and the McDill-Amateis GADA models consistently predicted greater heights up to age 25 than the models of DA2006 and CL2010, with larger height differences for the higher quality sites, but predicted shorter heights thereafter. Ultimately, the McDill-Amateis GADA model was chosen as the best model for its consistency in predicting reasonable heights extrapolated beyond the range of the data. Foresters can use this model to make more informed silvicultural prescriptions for intensively managed loblolly pine plantations in the West Gulf Coastal Plain.

Forest Science: Future Directions - Scott Roberts (Forest Science, 2019)

Introduction: 2017 National Silviculture Workshop: Forest Management Policy, Forest Restoration, Disturbance Resilience, Climate Adaptation - Theresa B Jain (Forest Science, 2019)

Carbon Emission Flow and Transfer through International Trade of Forest Products - Prativa Shrestha; Changyou Sun (Forest Science, 2019)
The environmental impact of commodity trade has become a considerable concern in recent decades. In this study, carbon emissions embodied in forest products trade are examined through a multiregional input–output model. Compared with other industries, the forest products industry is clean with a small total emission and mean emission intensity. The paper sector is more substantial in total emission and dirtier in emission intensity than the wood sector. Most countries with extensive forest products trade have experienced declining consumption-based carbon emissions over 1995–2009, and all countries have become cleaner based on the emission intensity value. Carbon emissions embodied in international trade of forest products are about 25 percent of total emissions from production activities. Developing countries generally have much higher emission intensities than developed countries. Uncertainties in the carbon emission data have a larger impact than those in the intermediate and final consumption data. These findings are helpful for policymakers to understand the economic–environmental relations of forest products trade and to improve policy and agreement designs.

Potential for Sugar Maple to Provide High-Quality Sawlog Trees at the Northern Edge of Its Range - François Guillemette; Steve Bédard (Forest Science, 2019)
The management of sugar maple (Acer saccharum) at the northern edge of its range is mainly oriented toward timber production, from trees of higher grades. However, both the quality of mature trees in natural stands and how the quality may vary depending on the silvicultural treatment are unknown, especially under northern conditions. The objective of this study was to describe the variation in stem quality of mature maple trees (diameter >33 cm) according to climatic, geographic or soil variables, and to evaluate the effects of a first selection cutting cycle on this quality. Annual temperature (1.7–4.1° C) was the most important variable explaining differences in the proportion of higher-grade trees, with a 16 percent gain associated with every additional increase in degrees Celsius. The practice of a first selection cutting was associated with an 11 percent gain in this proportion. Although the actual proportion of high-quality trees was below 35 percent on the coolest sites, a proper tree selection through silviculture could likely improve this proportion in future decades, whereas the potential effects of climate change are unclear.

Lowering Stand Density Enhances Resiliency of Ponderosa Pine Forests to Disturbances and Climate Change - Jianwei Zhang; Kaelyn A Finley; Nels G Johnson; Martin W Ritchie (Forest Science, 2019)
Stand density affects not only structure and growth, but also the health of forests and, subsequently, the functions of forest ecosystems. Here, we integrated dendrochronology and repeated inventories for ponderosa pine research plots to determine whether long-term growth and mortality responded to climate trends and how varying stand density influenced the responses. The plots were established prior to 1975 on existing stands throughout northern California. Although annual temperature increased consistently for the last 65 years, ring-width indices produced by eliminating age and thinning effects failed to detect radial trend regardless of site quality. However, interannual variation for the indices was substantial, reflecting a strong influence of climate on tree growth. Plot-level basal area increments were significantly affected by tree mortality. Stand density index explained most variation of mortality. Lowering stand density enhanced remaining tree growth, reduced mortality, and increased stand resiliency to disturbances and climate change. Besides higher climate moisture indices or lower vapor pressure deficits, any treatments that improve tree vigor and reduce stress will have a similar effect to reducing stand density. Although neither biotic disturbances nor abiotic conditions can be controlled, forest managers can manage stand density appropriately to enhance resilience to climate change and disturbances.

Genetic Variation in Acoustic Time of Flight and Drill Resistance of Juvenile Wood in a Large Loblolly Pine Breeding Population - Trevor D Walker; Fikret Isik; Steven E McKeand (Forest Science, 2019)
Acoustic time of flight and drill resistance (surrogates for wood stiffness and density, respectively) were measured on 11,097 standing trees from 269 pollen-mix families of loblolly pine (Pinus taeda L.) in 6- to 9-year-old progeny tests at eight sites across the southeastern United States. Specific gravity was measured on two test sites. The phenotypic correlation between specific gravity and drill resistance was moderate (r = 0.68), whereas the genetic correlation was very strong (rg = 0.96). Narrow-sense heritabilities for acoustic time of flight and drill resistance were around 0.35 for individual trees and very strong (0.90) for family means. High genetic correlations (>0.80) between pairs of sites suggested a low genotype-by-environment interaction for both traits. Genetic correlations between wood quality traits and other economic traits (growth and stem straightness) were low except for a moderate correlation between acoustic time of flight and tree slenderness (rg = –0.64). The checklot ranked near the middle for both wood quality traits, implying no inadvertent selection occurred in this population that has been selected intensively for volume productivity. This study is the first to apply these tools in a large breeding program, and results suggest they are effective for selecting genotypes for wood quality.

Evaluating Forest Biomass Recovery in South Central Alabama Pine Plantations - J Mcfero Grace; J F Klepac; Steve E Taylor (Forest Science, 2019)
Improved use of forest biomass has been presented as a viable option to satisfy a portion of the demand for sustainable alternative sources of energy. Yet, there are considerable gaps in our understanding related to the efficiencies of current state-of-the-art forest biomass recovery systems. Southern pine plantation biomass stands typically exhibit higher stand densities and smaller-diameter trees than conventional stands, which, in turn, may result in reduced recovery efficiencies. In this study, the impact of new harvest systems for biomass recovery was investigated in typical southern pine plantation biomass harvests. Specifically, spatial and temporal effects on residue distribution were examined following biomass harvest of 14- and 24-year-old loblolly pine plantations. Preharvest total standing biomass for the younger site at 90 t ac–1 (220 t hectare–1) was half that of the older site at 160 t ac–1 (390 t hectare–1). Although the analysis detected no significant temporal effects on residue distributions, the preharvest condition exhibited 100 percent ground cover, whereas postharvest conditions had nearly 20 percent of the area designated as bare. Two of the five residue classifications, light debris and litter-herbaceous, were found to have a significantly higher incidence of occurrence than the other residue classifications on the sites based on a multinomial regression. In general, we found recovery efficiencies for both sites of 80 percent or greater for both methods of determination, by destructive sampling and based on load tickets.

Annual Greenhouse-Gas Emissions from Forest Soil of a Peri-Urban Conifer Forest in Greece under Different Thinning Intensities and Their Climate-Change Mitigation Potential - F Doukalianou; K Radoglou; A E Agnelli; K Kitikidou; E Milios; M Orfanoudakis; A Lagomarsino (Forest Science, 2019)
Knowledge of the response of thinning implementation on forest soil–atmospheric greenhouse gas (GHG) (CO2, CH4, N2O) fluxes exchange system in Mediterranean region is limited because of the high heterogeneity of both soil properties and forest biomass. The novelty of this study is grounded predominantly in evaluating for the first time the response of annual GHG fluxes to thinning in a coniferous peri-urban forest soil in Greece, thus contributing significantly to the enrichment of the GHG fluxes database from the Mediterranean forest ecosystem. Results suggest that CH4 uptake increased with increasing thinning intensity. The reduction in CO2 emissions in both thinning treatments was possibly related to an indirect effect of soil heterotrophic and autotrophic respiration. Coniferous peri-urban forests in Greece can act temporally as sinks of atmospheric N2O in the coldest months and a weak source of N2O fluxes in summer. The GHG variation depended largely on soil environmental factors with soil temperature representing the dominant factor for CO2 and CH4, whereas soil moisture correlated, albeit weakly, with N2O variability. Reduction in global warming potential was observed in both thinning treatments, markedly in selective treatment, giving an initial indication that high-intensity thinning in coniferous peri-urban forests in Greece presents a high potential for global change mitigation.

Methyl Bromide Fumigation to Eliminate Thousand Cankers Disease Causal Agents from Black Walnut - Kendhl W Seabright; Scott W Myers; Stephen W Fraedrich; Albert E Mayfield; Melissa L Warden; Adam Taylor (Forest Science, 2019)
Phytosanitary treatments for logs and barked wood products are needed to mitigate the spread of thousand cankers disease through the movement of these commodities. The disease threatens eastern black walnut (Juglans nigra L.) populations in the United States. It is caused by repeated attacks by the walnut twig beetle (Pityophthorus juglandis Blackman) and subsequent canker development caused by the fungal pathogen Geosmithia morbida M. Kolařík et al. Methyl bromide (MB) fumigations were evaluated for efficacy against P. juglandis and G. morbida in J. nigra bolts. Fumigation with 82 mg/L MB for 24 h at 4.5° C eliminated P. juglandis in J. nigra, but was ineffective against G. morbida. Subsequent experiments focused on eliminating G. morbida, but results were inconclusive because of low rates of pathogen recovery from naturally infested control bolts. Final experiments used J. nigra bolts artificially inoculated with G. morbida. Fumigations with 240 and 320 mg/L MB for 72 h at 10° C were effective in eliminating G. morbida from J. nigra bolts. Results confirm that the USDA fumigation treatment schedule for logs with the oak wilt pathogen will also mitigate the risk of spreading the thousand cankers disease vector and pathogen by movement of walnut bolts and wood products.

A Pragmatic Method to Forecast Stumpage Prices - John E Wagner; Jill Rahn; Mariela Cavo (Forest Science, 2019)
Stumpage price is one of the key economic inputs in developing sustainable forest-management plans and analyzing forest-management decisions and investments. A robust method to forecast stumpage prices and prediction intervals would help timberland owners and consultants bound uncertainty and improve the chance that future management actions agree with specified objectives. We evaluated three forecasting methods: simple moving average, linear weighted moving average, and exponential weighted moving average. Real annual stumpage prices for New York’s six most common species were used to evaluate the robustness of the three forecasting methods. We concluded that, while being more complex computationally, the exponential weighted moving average was preferred to the simple and linear weighted moving average.

Annual Fire Return Interval Influences Nutritional Carrying Capacity of White-Tailed Deer in Pine–Hardwood Forests - Michael P Glow; Stephen S Ditchkoff; Mark D Smith (Forest Science, 2019)
Prescribed fire is a cost-effective habitat management tool in pine stands to enhance the quantity and quality of forage available for white-tailed deer (Odocoileus virginianus). Management recommendations typically suggest a 3- to 5-year burn rotation in mixed pine–hardwood stands to increase quality forage production, but as fire frequency increases, forb and legume biomass increases, and woody browse decreases. A more frequent burn rotation may be a viable management option for deer managers, but there is still a lack of information regarding preferred forage and nutritional carrying capacity response to prescribed fire at these intervals. We measured the production and nutritional quality of forage within mature pine–hardwood stands after a 1- or 2-year fire-return interval during three nutritionally stressful periods for deer on a 640-acre (259-hectare) enclosure located in east-central Alabama during 2014 and 2015. These stands had previously been burned annually for over 15 years, resulting in an abundance of herbaceous vegetation. We then compared forage class biomass, nutritional carrying capacity estimates, and digestible protein between burn treatments. A 1-year fire return interval improved habitat quality to a greater degree than a 2-year fire return interval by increasing the production of forage able to support greater nutritional planes. An annual burn rotation is an effective option for managers to increase protein availability in pine–hardwood stands, but other factors such as decreased cover availability and soft mast production should also be considered.

Whole Stand Volume and Green Weight Equations for Loblolly Pine in the Western Gulf Region of the United States through Age 15 - Derrick A Gallagher; Bronson P Bullock; Cristian R Montes; Michael B Kane (Forest Science, 2019)
Three whole stand equations were evaluated for best prediction performance of loblolly pine volume and green weight in three physiographic regions of the Western Gulf through age 15 using remeasured permanent research plots from a spacing study. The equations evaluated are two nonlinear forms of the Schumacher yield equation that predict yield from dominant height, stand basal area, and age with or without stand tree density, and a logistic parameterization of the Chapman–Richards equation that uses only basal area and age. The nonlinear form of the Schumacher yield equations (Equations 2 and 3) performed better than the Chapman–Richards model (Equation 4), indicating a more appropriate mathematical model to describe forest yield. The sixfold cross-validation residual standard error for volume prediction in the Lower Coastal Plain, Upper Coastal Plain, and Interior Flatwoods was 109, 179, and 71 cubic feet per acre, respectively. The residual standard error of green weight prediction for the Lower Coastal Plain, Upper Coastal Plain, and Interior Flatwoods was 4, 2, and 3 tons per acre, respectively. The presented whole stand yield models provide physiographic region-specific estimates of yield for genetically improved loblolly pine under intensive management regimes.

Comparison of Leaf Moisture Content and Ignition Characteristics among Native Species and Exotic Conifers in Northwestern Patagonia, Argentina - Lucas O Bianchi; Facundo J Oddi; Miriam Muñoz; Guillermo E Defossé (Forest Science, 2019)
The forest–steppe ecotone in Argentine Patagonia has been planted with non-native Pinus ponderosa, Pseudotsuga menziesii, Pinus radiata, and P. contorta. As in many other planted areas of the Southern Hemisphere, there is great concern about increasing landscape flammability. We determined, under lab conditions, live fuel moisture content (LFMC) and leaf ignition of these conifers, a naturalized poplar, and 13 native species. The mean LFMC was inversely related to leaf ignition of these species. The conifer LFMC was lower than that of most natives, making the conifers the most ignitable species. Pinus ponderosa and Pseudotsuga menziesii showed the spring dip phenomenon (i.e., low LFMC in early spring). Leaf ignition and LFMC may help elucidate some flammability components at species levels. At landscape scales, however, they have to be evaluated along with other landscape traits such as structure and stand composition. Understanding this landscape context will require full-scale experimental ﬁres. Nevertheless, our results provide useful information for fire danger assessment, and also for setting policies aimed at planning and applying appropriate silvicultural techniques for fire prevention and control, and hence reducing fire danger at stand or landscape levels.

Effects of Arbuscular Mycorrhiza Fungi on the Growth Characteristics, Root Morphology, and Ion Distribution of Pyrus betulaefolia Bunge under Saline-Alkaline Stress - Xiuyan Yang; Huanyong Li; Lei Jiang; Xiaoqian Tang; Xiaowei Liu; Huaxin Zhang (Forest Science, 2019)
In this study, Pyrus betulaefolia Bunge seedlings were used to investigate the effects of an arbuscular mycorrhiza fungus (AMF; Funneliformis mosseae) on plant-growth characteristics, root morphology, salt tolerance, and ion distribution under saline-alkaline stress. An indoor pot experiment was conducted in which seedlings were inoculated with Funneliformis mosseae under treatments of four different concentrations of Na2CO3 solution. The results show that AMF could establish symbiotic relations with the P. betulaefolia root system under Na2CO3 stress. Under the same Na2CO3 stress, AMF significantly increased the height growth and biomass accumulation of P. betulaefolia seedlings. AMF also promoted the root growth of P. betulaefolia seedlings. AMF inoculation significantly affected the absorption and distribution of K+ and Na+ in P. betulaefolia. The K/Na ratios in the roots and leaves of seedlings inoculated with AMF were higher than those of seedlings without inoculation. The results of this study show that inoculation with AMF had a positive effect on enhancing the saline-alkaline tolerance of P. betulaefolia, and root treatment of P. betulaefolia seedlings with Funneliformis mosseae has the potential for application in the development of saline-alkaline soil vegetation.

Predictive Ability of Mixed-Effects Height–Diameter Models Fit Using One Species but Calibrated for Another Species - Curtis L Vanderschaaf (Forest Science, 2019)
Mixed-effects individual tree height–diameter models are presented for important pines in the Western Gulf, USA. Equations are presented for plantations of loblolly (Pinus taeda L.), longleaf (Pinus palustris P. Mill.), shortleaf (Pinus echinata Mill.), and slash (Pinus elliottii Engelm.) pine. To produce localized individual tree height estimates, these models can be calibrated after obtaining height–diameter measurements from a plot/stand of interest. These equations can help answer an interesting question of whether a model fit for one species can be calibrated to produce reasonable height estimates of another species. In situations where mixed-effects models have not been developed for a particular species, perhaps an equation from another species can be used. This question was addressed by calibrating these models using independent data of loblolly, longleaf, and slash pine plantations located in South Carolina. For each calibration species, in addition to the models developed described above, previously published models, but of the same model form, fit using other species from across the USA were examined. Results show that models of a variety of species can be calibrated to provide reasonable predictions for a particular species. Predictions using this particular model form indicate that model calibration is more important than species-specific height–diameter relations.

Forest Fertilizer Applications in the Southeastern United States from 1969 to 2016 - Timothy J Albaugh; Thomas R Fox; Rachel L Cook; Jay E Raymond; Rafael A Rubilar; Otávio C Campoe (Forest Science, 2019)

Alteration to Woodland Structure through Midstory Mastication Increased Fuel Loading and Cover of Understory Species in Two Upland Hardwood Stands - Devin E Black; Mary A Arthur; Wendy Leuenberger; David D Taylor; Jeffrey F Lewis (Forest Science, 2019)
The contemporary decline of open woodlands in the eastern United States has prompted land managers to implement management prescriptions that encourage landscape and habitat diversity, often using mechanical thinning and prescribed fire as tools to alter stand structure. To increase habitat diversity and restore natural processes, a long-term oak woodland restoration project was planned for two upland hardwood stands in the Daniel Boone National Forest, Kentucky, United States. As an initial phase of restoration, we examined the effects of midstory mastication on stand structure, understory vegetation response, and fuels. The mastication treatment reduced stem density and basal area of trees ≤7.9 in. (20.1 cm) dbh by 69 percent and 47 percent, respectively, encouraged vigorous stump/root sprouting, and increased ground cover of forbs (204 percent) and native graminoids (253 percent) the first year on treated plots. Additionally, mastication created a variable cover of woody mulch on the forest floor and increased 1-h and 100-h time-lag fuels compared with controls. In year 2, Microstegium vimineum (invasive grass) cover increased by 700 percent on treated plots. This study imparts novel information on the mastication of upland hardwoods to benefit land managers in directing future treatments to shape desired stand structures and compositions, and increase landscape heterogeneity.

Changes in Physiological Functioning in Loblolly Pine Trees Undergoing Bark Beetle Simulated Mortality - Nicole J Hornslein; Courtney M Siegert; Heidi J Renninger (Forest Science, 2019)
The southeastern United States contains extensive loblolly pine (Pinus taeda L.) plantations at risk from bark beetle damage that can change ecosystem biogeochemical cycling. Functional changes in tree physiology have the potential to occur before visual evidence of mortality making them difficult to incorporate into ecosystem models. Therefore, we girdled loblolly pines to simulate bark beetle damage and measured physiological processes including sapflow rates, photosynthesis, litterfall, and needle nitrogen concentrations to determine the physiological changes occurring in trees undergoing mortality. We found that the girdling treatment took 5 months to significantly reduce sapflow rates but visual crown mortality occurred more than one year after girdling. Girdled pines had approximately 2.5 times lower water use than control pines and exhibited greater susceptibility to atmospheric water stress. Girdled and control pines had similar needle nitrogen concentrations and photosynthetic rates measured during the mortality year. However, more litterfall with higher nitrogen concentrations occurred in the mortality year than in the previous year, resulting in redistribution of carbon and nitrogen in the ecosystem. Overall, these data allow for better quantification of the effects of background disturbance levels and individual tree mortality on water, carbon, and nitrogen cycling within a loblolly pine ecosystem.

How Campers’ Beliefs about Forest Pests Affect Firewood Transport Behavior: An Application of Involvement Theory - John J Daigle; Crista L Straub; Jessica E Leahy; Sandra M De Urioste-Stone; Darren J Ranco; Nathan W Siegert (Forest Science, 2019)

Native Species Abundance Buffers Non-Native Plant Invasibility following Intermediate Forest Management Disturbances - Donald P Chance; Johannah R McCollum; Garrett M Street; Bronson K Strickland; Marcus A Lashley (Forest Science, 2019)
The biotic resistance hypothesis (BRH) was proposed to explain why intermediate disturbances lead to greater resistance to non-native invasions proposing communities that are more diverse provide greater resistance. However, several empirical data sets have rejected the BRH because native and non-native species richness often have a positive relation. We tested the BRH in a mature loblolly pine (Pinus taeda) forest with a gradient of disturbance intensities including canopy reduction, canopy reduction + fire, and canopy reduction + herbicide and fire. We analyzed data from the study using a combination of Pearson’s correlation and beta regressions. Using species richness, we too would reject BRH because of a positive correlation in species richness between native and non-native plants. However, native species abundance was greatest, and non-native species abundance was lowest following intermediate disturbances. Further, native and non-native species abundances were negatively correlated in a quadratic relation across disturbance intensities, suggesting that native species abundance, rather than richness, may be the mechanism of resistance to non-native invasions. We propose that native species abundance regulates resistance to non-native invasions and that intermediate disturbances provide the greatest resistance because they promote the greatest native species abundance.

Mill Willingness to Use Logging Residues to Produce Electricity: A Spatial Logistic Regression Approach - Raju Pokharel; Robert K Grala; Donald L Grebner; William H Cooke (Forest Science, 2019)

Timing of Nitrogen Resorption-Related Processes during Fall Senescence in Southern Oak Species - Richard Sample; Benjamin A Babst (Forest Science, 2019)
Oak (Quercus) species are prominent in southern US forests. The ability to recycle nitrogen (N) during dormancy is an important adaptation to conserve a limited resource, but N resorption in southern oaks is not well understood. Leaf protein and chlorophyll are both degraded during senescence to release N that can be stored in stems and roots. We hypothesized that leaf N would decrease soon after degradation of leaf protein and/or chlorophyll. Chlorophyll, protein, and N content were measured in leaves of Q. texana, Q. phellos, and Q. nigra during fall 2016 and 2017, in Arkansas. Degradation of protein, which holds the majority of leaf N, started early, in September, whereas chlorophyll degradation and N export from leaves occurred in late November. The delay between protein degradation and N export indicates that N resorption is drawn out over months in southern oaks, because of an unknown mechanism. Protracted leaf senescence could be due to a physiological or biochemical constraint, or it could be an adaptive trait where fall is typically warm and water-limited, but occasionally wet. Our results lay a foundation for future studies to examine how environmental stress may affect nutrient resorption during leaf senescence in southern oak species.

The Frequency and Anatomical Characteristics of Anomalous Dark Rings in Black Cherry, and Their Relation to Cherry Scallop Shell Moth Defoliations - Robert P Long; Michael C Wiemann; Thomas A Kuster (Forest Science, 2019)

Sliding Stability of Cable-Assisted Tracked Equipment on Steep Slopes - Francisca Belart; Ben Leshchinsky; John Sessions; Woodam Chung; Preston Green; Jeff Wimer; Brett Morrissette (Forest Science, 2019)

Two-Step Regression Process for Whole Stand Loblolly Pine Survival Projection and Quantifying Uncertainty - Derrick A Gallagher; Cristian R Montes; Bronson P Bullock; Michael B Kane (Forest Science, 2019)

Reversing Mesophication Effects on Understory Woody Vegetation in Mid-Southern Oak Forests - Andrew L Vander Yacht; Patrick D Keyser; Seth A Barrioz; Charles Kwit; Mike C Stambaugh; Wayne K Clatterbuck; Dean M Simon (Forest Science, 2019)

Growth-Density Relationships in Loblolly Pine Plantations - Micky G Allen; Harold E Burkhart (Forest Science, 2019)

Initiating Climate Adaptation in a Western Larch Forest - Justin S Crotteau; Elaine Kennedy Sutherland; Theresa B Jain; David K Wright; Melissa M Jenkins; Christopher R Keyes; Linda M Nagel (Forest Science, 2019)

Restoration of Native Fire-Adapted Southern Pine-Dominated Forest Ecosystems: Diversifying the Tools in the Silvicultural Toolbox - James M Guldin (Forest Science, 2019)

Risk Attitudes and Conservation Decisions: A Case Study of Family Forest Owners in Georgia - Moon Jeong Kang; Jacek P Siry; Gregory Colson; Susana Ferreira (Forest Science, 2019)

Integrating Strategic and Tactical Forest-Management Models within a Multicriteria Context - Pedro Belavenutti; Carlos Romero; Luis Diaz-Balteiro (Forest Science, 2019)

Modeling Wound-Closure Response Over Time in Douglas-Fir Trees - Dryw A Jones; Constance A Harrington; David Marshall (Forest Science, 2019)

A Technique for Implementing Group Selection Treatments with Multiple Objectives Using an Airborne Lidar-Derived Stem Map in a Heuristic Environment - Brian M Wing; Kevin Boston; Martin W Ritchie (Forest Science, 2019)

Cost Plus Net Value Change (C+NVC) Revisited: A Sequential Formulation of the Wildfire Economics Model - David Rossi; Olli-Pekka Kuusela (Forest Science, 2019)

Reconciling the Tradeoff between Economic and Ecological Objectives in Habitat-Tree Selection: A Comparison between Students, Foresters, and Forestry Trainers - Hannes Cosyns; Daniel Kraus; Frank Krumm; Tobias Schulz; Patrick Pyttel (Forest Science, 2019)

Comparing the Net Benefit of Forestland Access for Big-Game Hunting across Landownership Types in Georgia, USA - James C Mingie; Neelam C Poudyal; J M Bowker; Michael T Mengak; Jacek P Siry (Forest Science, 2019)

Survival, and Growth Response of Douglas-Fir Trees to Increasing Levels of Bole, Root, and Crown Damage - Dryw A Jones; Constance A Harrington; David Marshall (Forest Science, 2019)

Woody Debris and Nutrient Retention following Alternative Biomass Harvesting Guidelines - John M Kabrick; Keith W Goyne; Henry E Stelzer (Forest Science, 2019)

Focal-Point Aggregation Under Area Restrictions through Spatially Constrained Optimal Harvest Scheduling - Atsushi Yoshimoto; Patrick Asante (Forest Science, 2019)

Branch Elongation and Formation of New Stem Units as Influenced by Reductions in Leaf Photosynthetic Capacity - Shannon D Kidombo; Thomas J Dean (Forest Science, 2019)

A New Method for Estimating Coarse Root Production in Forest Ecosystem - Tran Van Do; Tamotsu Sato; Mamoru Yamamoto; Osamu Kozan; Nguyen Toan Thang; Vo Dai Hai; Tran Hoang Quy; Phung Dinh Trung; Dang Van Thuyet (Forest Science, 2019)

Decoupling the Diameter–Age Debate: The Boise National Forest’s Legacy Tree Guide - John Riling; Kathleen Geier-Hayes; Theresa Jain (Forest Science, 2019)

A Landscape-Level Assessment of Whitebark Pine Regeneration in the Rocky Mountains, USA - Sara A Goeking; Deborah K Izlar; Thomas C Edwards (Forest Science, 2019)

Seasonal Changes in Live Tree Branch Moisture in Oregon, USA: Four Case Studies - Francisca Belart; John Sessions; Glen Murphy (Forest Science, 2019)

Stumpage Opportunity Cost of Riparian Management Zones on Headwater Streams in Northern Hardwood Timberlands - Maneesha T Jayasuriya; René H Germain; Eddie Bevilacqua (Forest Science, 2019)

Tariff and US Paper Products Trade - Daowei Zhang; Ly Nguyen (Forest Science, 2019)

Projected Market Competition for Wood Biomass between Traditional Products and Energy: A Simulated Interaction of US Regional, National, and Global Forest Product Markets - Prakash Nepal; Karen L Abt; Kenneth E Skog; Jeffrey P Prestemon; Robert C Abt (Forest Science, 2019)

Diurnal and Seasonal CO2 Assimilation by Four Plantation Species in Taiwan - Chung-I Chen; Ya-Nan Wang; Jui-Chu Yu (Forest Science, 2019)

Compatibility, Development, and Estimation of Taper and Volume Equation Systems - Dehai Zhao; Thomas B Lynch; James Westfall; John Coulston; Michael Kane; David E Adams (Forest Science, 2019)

Ecological Restoration of an Oak Woodland within the Forest-Prairie Ecotone of Kansas - G A Pabodha Galgamuwa; Charles J Barden; Jason Hartman; Thad Rhodes; Nicholas Bloedow; Raúl J Osorio (Forest Science, 2019)

Tree Diversity Determines the Diversity of the Taxonomic and Functional Structure of the Fungal Community in Forest Litter in Southern China - Wenya Xiao; Jiahao Zhao; Xinli Yan; Qingwei Guan (Forest Science, 2019)

Growth, Photosynthesis, and Cold Tolerance of Eucalyptus benthamii Planted in the Piedmont of North Carolina - John R Butnor; Kurt H Johnsen; Peter H Anderson; Kevin B Hall; Joshua M Halman; Gary J Hawley; Christopher A Maier; Paul G Schaberg (Forest Science, 2019)

Light and Moisture Conditions Suitable for Establishing Andean Cypress and Coihue Beech Seedlings in Patagonia: A Nursery Approach - Marina Caselli; María Florencia Urretavizcaya; Gabriel Ángel Loguercio; Guillermo Emilio Defossé (Forest Science, 2019)

Shade and Hemlock Woolly Adelgid Infestation Increase Eastern Hemlock Foliar Nutrient Concentration - Marika Lapham; Chelcy Ford Miniat; Albert E Mayfield; Robert M Jetton; Steven T Brantley; David R Zietlow; Cindi Brown; James R Rhea (Forest Science, 2018)

Influence of Selection Method on Skidder-Trail Soil Compaction in Longleaf Pine Forest - Seth W Bigelow; Noah A Jansen; Steven B Jack; Christina L Staudhammer (Forest Science, 2018)

The Evolution of Logging Businesses in Georgia 1987–2017 and South Carolina 2012–2017 - Joseph L Conrad IV; W Dale Greene; Patrick Hiesl (Forest Science, 2018)

Best Management Practices Influence Sediment Delivery from Road Stream Crossings to Mountain and Piedmont Streams - A J Lang; W Michael Aust; M Chad Bolding; Kevin J McGuire; Erik B Schilling (Forest Science, 2018)

The Role of Forest Setting on Partnership Demand and Engagement Approaches - Erin Seekamp; Lee Cerveny; Lori Barrow (Forest Science, 2018)

Direct and Indirect Assessment of Carbon Stock in Deadwood: Comparison in Calabrian Pine ( Pinus brutia Ten. subsp. brutia ) Forests in Italy - Isabella De Meo; Alessandra Lagomarsino; Alessandro Elio Agnelli; Alessandro Paletto (Forest Science, 2018)

Local Capacity to Engage in Federal Wildfire Suppression Efforts: An Explanation of Variability in Local Capture of Suppression Contracts - Max Nielsen-Pincus; Cody Evers; Cassandra Moseley; Heidi Huber-Stearns; R Patrick Bixler (Forest Science, 2018)

The Financial Performance of Public Furniture Firms with Different Positions in Antidumping Actions - Xufang Zhang; Changyou Sun (Forest Science, 2018)

Annual Monitoring of US Timber Production: Rationale and Design - John W Coulston; James A Westfall; David N Wear; Christopher B Edgar; Steven P Prisley; Thomas B Treiman; Robert C Abt; W Brad Smith (Forest Science, 2018)

Spatial Analyses of Invasion Patterns of Chinese Tallow (Triadica sebifera) in a Wet Slash Pine (Pinus elliottii) Flatwood in the Coastal Plain of Mississippi, USA - Zhaofei Fan (Forest Science, 2018)

Simultaneous Prediction of Plot-Level and Tree-Level Harvest Occurrences with Correlated Random Effects - Rubén Manso; François Ningre; Mathieu Fortin (Forest Science, 2018)

Climatic Effects on Site Productivity of Red Pine Plantations - Mahadev Sharma; John Parton (Forest Science, 2018)

Assignment Problems in Wildfire Suppression: Models for Optimization of Aerial Resource Logistics - Jorge Rodríguez-Veiga; Iván Gómez-Costa; María José Ginzo-Villamayor; Balbina Casas-Méndez; José Luis Sáiz-Díaz (Forest Science, 2018)

Mississippi Private Landowner Willingness for Diverting Land to Growing Short Rotation Woody Crops for Bioenergy Enterprises - Ian A Munn; Anwar Hussain; Donald L Grebner; Stephen C Grado; Marcus K Measells (Forest Science, 2018)

Operational Green Tree Retention and Land Cover Patterns in Intensively Managed Pine Forest Landscapes of the Southeastern United States - Michael C Parrish; Steve Demarais; T Bently Wigley; Sam K Riffell; Andrew W Ezell; Phillip D Jones (Forest Science, 2018)

Incorporating Social Diversity into Wildfire Management: Proposing “Pathways” for Fire Adaptation - Travis B Paveglio; Matthew S Carroll; Amanda M Stasiewicz; Daniel R Williams; Dennis R Becker (Forest Science, 2018)

Biomass Accumulation in the Endangered Shrub Lindera melissifolia as Affected by Gradients of Light Availability and Soil Flooding - Brian Roy Lockhart; Emile S Gardiner; Theodor D Leininger; Paul B Hamel; A Dan Wilson; Margaret S Devall; Nathan M Schiff; Kristina F Connor (Forest Science, 2018)

Evaluation of Betula platyphylla Families Based on Growth and Wood Property Traits - Deyang Liang; Xinxin Zhang; Chao Wang; Xiuwei Wang; Kailong Li; Guifeng Liu; Xiyang Zhao; Guan-Zheng Qu (Forest Science, 2018)

Landscape Genetics and Genetic Conservation of Two Keystone Species from Ombrophilous Dense Forest: Euterpe edulis and Ocotea catharinensis - Tiago Montagna; Juliano Zago da Silva; Alison Paulo Bernardi; Felipe Steiner; Victor Hugo Buzzi; Miguel Busarello Lauterjung; Adelar Mantovani; Maurício Sedrez dos Reis (Forest Science, 2018)

New Insights in Biocontrol Strategy against Cephalcia tannourinensis, the Principal Insect Defoliator of Lebanese Cedars - Martine Rehayem; Elise Noujeim; Nabil Nemer; Sylvie Pagès; Jean-Claude Ogier; Olivier Thaler; Bernard Duvic (Forest Science, 2018)

Assessments of Biodiversity, Carbon, and Their Relationships in Nepalese Forest Commons: Implications for Global Climate Initiatives - Harisharan Luintel; Robert M Scheller; Randall A Bluffstone (Forest Science, 2018)

A New Optimization Model for Spatially Constrained Harvest Scheduling under Area Restrictions through Maximum Flow Problem - Atsushi Yoshimoto; Patrick Asante (Forest Science, 2018)

Patterns and Drivers of Recent Tree Mortality in Diverse Conifer Forests of the Klamath Mountains, California - Melissa H DeSiervo; Erik S Jules; Drew S Bost; Emily L De Stigter; Ramona J Butz (Forest Science, 2018)

Empirical Modeling of Fire Spread Rate in No-Wind and No-Slope Conditions - Carlos G Rossa; Paulo M Fernandes (Forest Science, 2018)

Effect of Tree Diameter, Canopy Position, Age, and Browsing on Stump Sprouting in Southern New England - Jeffrey S Ward; Scott C Williams (Forest Science, 2018)

Regional Simulations of Loblolly Pine Productivity with CO2 Enrichment and Changing Climate Scenarios - Harold E Burkhart; Evan B Brooks; Heather Dinon-Aldridge; Charles O Sabatia; Nabin Gyawali; Randolph H Wynne; Valerie A Thomas (Forest Science, 2018)

Incidental Effects of Cut-to-Length Harvest Systems and Residue Management on Populus tremuloides (Michx.) Regeneration and Yield - Michael I Premer; Robert E Froese (Forest Science, 2018)

Improving Large Trailer Access for Biomass Recovery in Steep Terrain - Bryent Daugherty; John Sessions; Rene Zamora-Cristales; Michael G Wing (Forest Science, 2018)

Arthropod Abundance, Diversity, and Biomass during Bird Breeding Season in Camden White Gum and Slash Pine Plantations in the Southeastern United States - Elizabeth J Messick; Christopher E Comer; Michael A Blazier; T Bently Wigley (Forest Science, 2018)

Genetic Parameters for Growth, Stem Straightness, and Branch Quality for Pinus elliottii var. elliottii × Pinus caribaea var. hondurensis F1 Hybrid in Argentina - Ector C Belaber; María E Gauchat; Hugo D Reis; Nuno M Borralho; Eduardo P Cappa (Forest Science, 2018)

Abies pinsapo Boiss. Transcriptome Sequencing and Molecular Marker Detection: A Novel Genetic Resources for a Relict Mediterranean Fir - A Pérez-González; M Marconi; I Cobo-Simón; B Méndez-Cea; P Perdiguero; R Linacero; J C Linares; F J Gallego (Forest Science, 2018)

Brood Production by Xyleborus glabratus in Bolts from Trees Infected and Uninfect ed with the Laurel Wilt Pathogen, Raffaelea lauricola - Stephen W Fraedrich; Thomas C Harrington; Qiong Huang; Stanley J Zarnoch; James L Hanula; Glenda Susan Best (Forest Science, 2018)

Identifying Key Factors for the Success of a Regional Logistic Center - François Sarrazin; Luc LeBel; Nadia Lehoux (Forest Science, 2018)

The Effects of Repeated Prescribed Fire and Thinning on Bees, Wasps, and Other Flower Visitors in the Understory and Midstory of a Temperate Forest in North Carolina - Joshua W Campbell; Patrick A Vigueira; Cynthia C Viguiera; Cathryn H Greenberg (Forest Science, 2018)

Immediate Post–Forest Fire Salvage Logging, Soil Erosion, and Sediment Delivery - Cajun E James; Bruce Krumland (Forest Science, 2018)

Controlling Dense Layers of Pawpaw (Asimina triloba) in Mesic Upland Forest Understories - Matthew G Olson; Michael T Keeley (Forest Science, 2018)

Different Structure of Sessile Oak Stands Affects Soil Moisture and Soil CO2 Efflux - Eva Darenova; Matjaž Čater (Forest Science, 2018)

An Improved Water Budget for the El Yunque National Forest, Puerto Rico, as Determined by the Water Supply Stress Index Model - Liangxia Zhang; Ge Sun; Erika Cohen; Steven G McNulty; Peter V Caldwell; Suzanne Krieger; Jason Christian; Decheng Zhou; Kai Duan; Keren J Cepero-Pérez (Forest Science, 2018)

Phytophthora cinnamomi Involved in the Decline of Holm Oak (Quercus ilex) Stands in Southern Italy - Salvatore Frisullo; Giuseppe Lima; Gaetano Magnano di San Lio; Ippolito Camele; Luigi Melissano; Ivana Puglisi; Antonella Pane; Giovanni Enrico Agosteo; Leonardo Prudente; Santa Olga Cacciola (Forest Science, 2018)

Genotypic Variation and Genotype-by-Environment Interactions in Growth and Wood Properties in a Cloned Eucalyptus urophylla × E. tereticornis Family in Southern China - Heyu Yang; Qijie Weng; Fagen Li; Changpin Zhou; Mei Li; Shengkan Chen; Hongxia Ji; Siming Gan (Forest Science, 2018)

Time-Since-Death and Its Effect on Wood from Beetle-Killed Engelmann Spruce in Southwest Colorado - Damon Vaughan; Kurt Mackes; James B Webb (Forest Science, 2018)

Time Spent in Federal Court: U.S. Forest Service Land Management Litigation 1989–2008 - Denise M Keele; Robert W Malmsheimer (Forest Science, 2018)

Spatial Genetic Structure in Seed Stands of Pinus arizonica Engelm. and Pinus cooperi Blanco in the State of Durango, Mexico - Saskia C Friedrich; José C Hernández-Díaz; Ludger Leinemann; José A Prieto-Ruíz; Christian Wehenkel (Forest Science, 2018)

First Report of Neozygites sp. (Entomophthoromycota: Neozygitales) Affecting the Woolly Poplar Aphid - Cristian Montalva; Alex González; Eduardo Valenzuela; Eladio Rojas; Richard A Humber (Forest Science, 2018)

Forest Cover, Agricultural, and Socio-Economic Development: A Weighted Beta-Logistic Approach with Ratio Response - Francisco X Aguilar; Nianfu Song (Forest Science, 2018)

Effects of Thinning on Ring Mass Growth along Stem of Douglas Fir in Four Coastal Pacific Northwest Sites - David G Briggs; Rapeepan Kantavichai (Forest Science, 2018)

Implementing the 2012 Forest Planning Rule: Best Available Scientific Information in Forest Planning Assessments - C M Ryan; L K Cerveny; T L Robinson; D J Blahna (Forest Science, 2018)

Estimating the Basic Density and Mechanical Properties of Elite Loblolly Pine Families with Near Infrared Spectroscopy - Gifty E Acquah; Charles Essien; Brian K Via; Nedret Billor; Lori G Eckhardt (Forest Science, 2018)

Estimated Sediment Reduction with Forestry Best Management Practices Implementation on a Legacy Forest Road Network in the Northern Rocky Mountains - Brian D Sugden (Forest Science, 2018)

Potential Effects of US Protectionism and Trade Wars on the Global Forest Sector - Joseph Buongiorno; Craig Johnston (Forest Science, 2018)

An improved water budget for the El Yunque National Forest, Puerto Rico, as determined by the Water Supply Stress Index model - Liangxia Zhang; Ge Sun; Erika Cohen; Steven G McNulty; Peter V Caldwell; Suzanne Krieger; Jason Christian; Decheng Zhou; Kai Duan; Keren J Cepero-Pérez (Forest Science, 2018)

First Report of Neozygites sp. (Entomophthoromycota: Neozygitales) Affecting the Woolly Poplar Aphid - Cristian Montalva; Alex González; Eduardo Valenzuela; Eladio Rojas; Richard A Humber (Forest Science, 2018)

Different structure of sessile oak stands affects soil moisture and soil CO2 efflux - Eva Darenova; Matjaž Čater (Forest Science, 2018)

Arthropod abundance, diversity, and biomass during bird breeding season in Camden white gum and slash pine plantations in the southeastern United States - Elizabeth J Messick; Christopher E Comer; Michael A Blazier; T Bently Wigley (Forest Science, 2018)

Controlling dense layers of pawpaw (Asimina triloba) in mesic upland forest understories - Matthew G Olson; Michael T Keeley (Forest Science, 2018)

Corrigendum (Forest Science, 2018)

Forest Science 2017 Reviewers (Forest Science, 2018)

Multienvironment Evaluation of Pinus pinaster Provenances: Evidence of Genetic Trade-Offs between Adaptation to Optimal Conditions and Resistance to the Maritime Pine Bast Scale ( Matsucoccus feytaudi ) - Giovanni Di Matteo; Jordi Voltas (Forest Science, 2016)

Local Seed Source Availability Limits Young Seedling Populations for Some Species More Than Other Factors in Northern Hardwood Forests - John L. Willis; Michael B. Walters; Evan Farinosi (Forest Science, 2016)

The Effects of Rehydration Time on Pressure-Volume Curves of Larix gmelinii and Fraxinus mandshurica in Northeast China - Liu Yang; Robert O. Teskey; Huizhen Sun (Forest Science, 2016)

Unexpected Events When Manually Falling Trees in Coastal British Columbia - Gregory John DeMille; Kevin Lyons (Forest Science, 2016)

An Agent-Based Model of Heterogeneous Forest Landowner Decisionmaking - Jesse D Henderson; Robert C Abt (Forest Science, 2016)

Conifer Root Proliferation after 20 Years of Soil Compaction - Matt D. Busse; Gary O. Fiddler; Carol J. Shestak (Forest Science, 2016)
Soil compaction is known to limit plant growth by reducing soil macroporosity and restricting gas, water, and root movement. Recent evidence from study sites across the United States and Canada, however, suggests that tree growth is not universally affected by soil compaction from forest harvesting practices. Our observational study examined rooting patterns in mixed conifer plantations in the central Sierra Nevada of California to determine whether tree roots use continuous pathways or channels to overcome the physical restrictions of compacted soil. Replicate plots were established 20–25 years earlier to compare compacted and uncompacted treatments after clearcut harvesting. Fine and lateral root counts were taken at multiple depths in soil trenches. Rooting was extensive in compacted plots despite consistently high soil strength values (~3 MPa). No differences in rooting patterns or in fine or lateral root numbers were detected between compaction treatments. The results indicated long-term tolerance by conifer roots to soil compaction without clear use of preferential channels or uncompacted zones.

Biodiversity in Dead Wood - Christopher W. Woodall (Forest Science, 2013)

R undio , D.E., and D.H. O lson . 2007. Influence of Headwater Site Conditions and Riparian Buffers on Terrestrial Salamander Response to Forest Thinning. For. Sci . 53(2): 320–330. (Forest Science, 2013)

Niquidet, K., and B. Manley. 2011. Testing for Nonlinear Spatial Integration in Roundwood Markets. For. Sci. 57(4):301–308 (Forest Science, 2012)

Effects of Land Use/Cover Change and Harvests on Forest Carbon Dynamics in Northern States of the United States from Remote Sensing and Inventory Data: 1992–2001 - Daolan Zheng; Linda S. Heath; Mark J. Ducey; James E. Smith (Forest Science, 2011)
We examined spatial patterns of changes in forest area and nonsoil carbon (C) dynamics affected by land use/cover change (LUC) and harvests in 24 northern states of the United States using an integrated methodology combining remote sensing and ground inventory data between 1992 and 2001. We used the Retrofit Change Product from the Multi-Resolution Land Characteristics Consortium to quantify LUC. We then calculated C dynamics using C densities for major forest types based on US Forest Service Forest Inventory and Analysis data by forest area for different statuses (i.e., afforestation, deforestation, and forest remaining forest) and incorporated county-level harvest data. Across the region, 16,740 km2 of forestland changed to nonforest, whereas 9,120 km2 of nonforest became forestland, a net loss of 7,620 km2 of forestland during the period or −0.13%/year. The region as a whole functioned as a C sink of 627 Tg (1 teragram = 1012 g) or 70 Tg of C/year. Regional C sequestration calculated using forest type identification at the state level was 5% higher than that from the county-level identification. Integrated annual effects of LUC and harvest on reducing C stocks at the state level varied substantially, ranging from 0.4% in North Dakota to 5.1% in Delaware with an average of 3.2% across the region (3.4% in the 13 northeastern states and 2.6% in the 11 northcentral states), compared with what it would be without these effects. We also found that within the region the annual LUC rate was significantly correlated with population density at the state level (P < 0.001).

Late-Successional Biomass Development in Northern Hardwood-Conifer Forests of the Northeastern United States - William S. Keeton; Andrew A. Whitman; Gregory C. McGee; Christine L. Goodale (Forest Science, 2011)
Managing the contribution of forest ecosystems to global carbon cycles requires accurate predictions of biomass dynamics in relation to stand development. Our study evaluated competing hypotheses regarding late-successional biomass dynamics in northern hardwood-conifer forests using a data set spanning the northeastern United States, including 48 mature and 46 old-growth stands. Continuous data on dominant tree ages were available for 29 of these and were used as an indicator of stand development. Aboveground live biomass was significantly (P < 0.001) different between mature (195 Mg/ha) and old-growth (266 Mg/ha) sites. Aboveground biomass was positively (P < 0.001) and logarithmically correlated with dominant tree age; this held for live trees (r2 = 0.52), standing dead trees (r2 = 0.36), total trees (r2 = 0.63), and downed woody debris (r2 = 0.24). In a Classification and Regression Tree analysis, stand age class was the strongest predictor of biomass, but ecoregion and percent conifer accounted for ∼25–33% of intraregional variability. Biomass approached maximum values in stands with dominant tree ages of ∼350–400 years. Our results support the hypothesis that aboveground biomass can accumulate very late into succession in northern hardwood-conifer forests, recognizing that early declines are also possible in secondary forests as reported previously. Empirical studies suggest a high degree of variability in biomass development pathways and these may differ from theoretical predictions. Primary forest systems, especially those prone to partial disturbances, may have different biomass dynamics compared with those of secondary forests. These differences have important implications for both the quantity and temporal dynamics of carbon storage in old-growth and recovering secondary forests.

Near-Surface Soil Carbon, Carbon/Nitrogen Ratio, and Tree Species Are Tightly Linked across Northeastern United States Watersheds - Donald S. Ross; Scott W. Bailey; Gregory B. Lawrence; James B. Shanley; Guinevere Fredriksen; Austin E. Jamison; Patricia A. Brousseau (Forest Science, 2011)
Forest soils hold large stores of carbon, with the highest concentrations in the surface horizons. In these horizons, both the total C mass and the C/N ratio may respond more rapidly to changes in tree species than lower horizons. We measured C and C/N ratios in the Oa or A horizon from 12 watersheds at 8 established forested research sites in the northeastern United States. The dominant tree species included Acer saccharum, Betula alleghaniensis, Fagus grandifolia, Picea rubens, and Tsuga canadensis. In 710 plots, both soil C (50–530 g kg−1) and the C/N ratio (11.6–45.3) had a wide range. In all but the Cone Pond watershed, both N concentration and the C/N ratio were strongly related to C content. For these 11 watersheds, the average C/N ratio = 9.5 + 0.030 × C g kg−1 (R2 = 0.97, P < 0.001). Ratios at Cone Pond were much higher than would be predicted from this equation and charcoal was found in numerous samples, suggesting a source of recalcitrant C. Averaged by watershed, C concentration was also significantly related to C pools. The carbon concentration of the horizons sampled was negatively related to A. saccharum + B. alleghaniensis dominance and positively related to conifer + F. grandifolia dominance. The strong relationships between C, C/N ratio, and species suggest predictable patterns in C accumulation in near-surface soils.

Carbon in Northern Forests - Chris Swanston; Andrew Burton (Forest Science, 2011)

Plantations for Bioenergy: Principles for Maintaining Biodiversity in Intensively Managed Forests - David J. Flaspohler; Christopher R. Webster (Forest Science, 2011)
As the value of forests for providing a feedstock for bioenergy increases, more land will probably be converted to fast-growing tree plantations to increase short-term production of cellulose. In general, plantations support fewer plant and animal species than native forests because plantations are greatly simplified in terms of tree and other plant species richness and in terms of many structural and process-related forest functions. However, native biodiversity can be retained in some plantation forests if careful management is used in all stages of plantation establishment, tending, and harvest. Key considerations for conserving biodiversity as plantation forests grow as a proportion of total world forest cover include choice of plantation tree species, harvest frequency, rotation age, and care and management of biological legacies and forest understory plant and wildlife communities. We provide background and guidance that can be used to guide future plantation management in a new era of using forests to capture and store carbon and to generate bioenergy.

Potential Influence of Forest Management on Regional Carbon Stocks: An Assessment of Alternative Scenarios in the Northern Lake States, USA - John B. Bradford (Forest Science, 2011)
Forest management affects stand age. In consideration of the strong link between stand age and carbon cycling, altering harvesting regimes can influence regional carbon stocks and sequestration. Recent research has quantified ecosystem carbon stocks across stand age in upland conifer and aspen–birch forests of the northern Lake States. This study applied those relationships to assess how forest management could influence carbon stocks in these two forest types. US Forest Service Forest Inventory and Analysis data were used to estimate current regional age structure and management intensity and state Gap Analysis Program data were used to assess forest type abundance. Across the region, current carbon stocks in aspen–birch and upland conifer forests are estimated to be 590 and 367 Tg C, respectively. Ceasing timber harvesting over the next century would increase the prevalence of older stands and increase ecosystem carbon stocks by 54% (31% in 50 years) and 30% (19% in 50 years) in aspen–birch and upland conifer forests, respectively. Harvesting aspen–birch stands would change ecosystem carbon stocks by +4% or −13% under annual harvesting of 1 or 2%, respectively. Harvesting upland conifer stands at a rate of 1 or 2% every year would decrease ecosystem carbon by 3 and 18%, respectively. Carbon from harvested material partly compensates for differences in total carbon stocks between no-harvest and harvest scenarios, suggesting a net positive carbon sequestration in all scenarios within 100 years. These results provide insight into the potential maximum impact of forest management on carbon stocks and sequestration in these two forest types.

Carbon Credit Eligibility under Area Regulation of Harvest Levels in Northern Minnesota - John S. Gunn; David S. Saah; Kathryn Fernholz; David J. Ganz (Forest Science, 2011)
We evaluated the implications of area regulation of harvest on eligible carbon under both the Voluntary Carbon Standard (VCS) and the Chicago Climate Exchange (CCX) for public forest lands in north central Minnesota (89,840 ha total). We used data from the carbon submodel of the US Forest Service Forest Vegetation Simulator (Lake States variant) to evaluate changes in forest carbon stocks under different management scenarios. Baseline harvest intensity was defined by considering the manager's short-range tactical plans and the distribution of harvests by cover type and intensity class then became the “business as usual” (BAU) for use in the calculation of eligible carbon under the VCS and CCX. Under VCS, the most effective way to increase carbon stocks while meeting other management objectives was to shift harvest practices to lower intensity entries and retain higher residual basal areas. The carbon stock change rates for each manager varied significantly under the BAU scenario and resulted in a mean annual net decrease. Because CCX carbon credit eligibility requires a net increase of carbon stocking from the base year, area regulation may create periods of time where there is no eligible carbon volume. An alternate management strategy that uses the area regulation method, reduces harvest intensity, and decreases overall acreage harvested was able to provide higher postharvest carbon stocks versus the BAU scenario under VCS.

Allometric Scaling of Large Branch Volume in Hardwood Trees in Michigan, USA: Implications for Aboveground Forest Carbon Stock Inventories - David W. MacFarlane (Forest Science, 2011)
Allometric scaling of large branch volume (branches to a ≥9-cm top diameter outside of bark) was examined using data from hundreds of hardwood trees of 11 hardwood tree species across a range of sites in Michigan. The amount of large branch volume in hardwoods generally increased with tree size with most of it in first-order branches (off of the main stem), but there were trees as small as 35 cm that had third-order large branches in their crowns. To explore how branch volumes scaled with bole volume, large branch volume expansion factors (VEFs) were calculated and correlated with several stem, branch, and crown metrics. Tree dbh and height, respectively, were weakly correlated (r2 = 0.15) and uncorrelated with VEFs, but crown ratio and the diameter of the largest branch in the tree explained almost 50% of variation in VEFs across a range of tree species, sizes, and site conditions. Combining stem, crown, and branch measurements allowed for as much as 64% of variation in branch to bole volume scaling to be explained. For 9 of 11 species studied, species-specific models improved model fits compared with those for a species-composite model. Understanding branch to bole volume relationships could improve forest carbon inventories by reducing error in whole-tree volume estimation and by clarifying the amount of merchantable volumes in branches, and correlates of large branch VEFs might even serve as indicators of whole-tree wood density.

Positive Relationship between Aboveground Carbon Stocks and Structural Diversity in Spruce-Dominated Forest Stands in New Brunswick, Canada - Weifeng Wang; Xiangdong Lei; Zhihai Ma; Daniel D. Kneeshaw; Changhui Peng (Forest Science, 2011)
Maintaining both the structure and functionality of forest ecosystems is a primary goal of forest management. In this study, relationships between structural diversity and aboveground stand carbon (C) stocks were examined in spruce-dominated forests in New Brunswick, Canada. Tree species, size, and height diversity indices as well as a combination of these diversity indices were used to correlate aboveground C stocks. Multiple linear regressions were subsequently used to quantify the relationships between these indices and aboveground C stocks, and partial correlation analysis was also adopted to remove the effects of other explanatory variables. Results show that stand structural diversity has a significant positive effect on aboveground C stocks even though the relationship is weak overall. Positive relationships observed between the diversity indices and aboveground C stocks support the hypothesis that increased structural diversity enhances aboveground C storage capacity. This occurs because complex forest structures allow for greater light infiltration and promote a more efficient resource use by trees, leading to an increase in biomass and C production. Mixed tolerant species composition and uneven-aged stand management in conjunction with selection or partial cutting to maintain high structural diversity is therefore recommended to preserve biodiversity and C stocks in spruce-dominated forests.

Toward Efficient Management of Large Fires: A Mixed Integer Programming Model and Two Iterative Approaches - Yu Wei; Douglas B. Rideout; Thomas B. Hall (Forest Science, 2011)
In this study, we developed an optimization model and two iterative approaches to improve the efficiency of large fire management. This model allocates suppression effort across time and space to minimize fire loss within a defined duration. It departs from previous research by replacing simplified fire containment rules with progress-based fire loss control. This is accomplished by extending the minimum travel time algorithm to build a large fire suppression model. Mixed integer programming is used to integrate spatial information such as fire behavior, firefighter safety, and values at risk to guide large fire suppression. The concern of time-specific suppression allocation is modeled through two iterative approaches using different logical procedures. Test cases demonstrate how this model assembles spatial data to support suppression decisions for one fire or multiple simultaneous fires. Suppression is also scheduled across 30 randomly simulated fires in Sequoia and Kings Canyon National Parks. Results demonstrate that suppression delay can significantly increase fire loss. Simulation results show that iterative approach A is more efficient in distributing suppression effort into short time periods.

Dynamic Treatment Units in Eucalyptus Plantation - Petteri Packalén; Tero Heinonen; Timo Pukkala; Jari Vauhkonen; Matti Maltamo (Forest Science, 2011)
The purpose of this study was to test airborne laser scanning-based forest inventory and the use of dynamic treatment units in eucalyptus plantations. Dynamic treatment units are formed by spatial optimization, which aggregates small inventory units. The hypothesis is that the use of dynamic treatment units increases yield and improves the efficiency of forest use. Forest inventory based on airborne laser scanning provides data for small units, which must be aggregated into feasible treatment units. The study area was a Eucalyptus pulpwood plantation in Brazil. Mixed-effects models were constructed for the basal area and dominant height using an area-based method. The plot-level estimates of growing stock characteristics were more accurate than those obtained for the stand level in many previous studies. The study area was divided into hexagons of 300 m2 for which the growing stock characteristics were estimated. A growth simulator was used to produce treatment schedules for the hexagons by varying the rotation length. The production potential of the planning area was examined by maximizing the growing stock volume at the end of the planning period with varying degrees of cutting area aggregation, with an even-flow cutting target for every 1-year period. The use of dynamic treatment units always increased the total volume production, i.e., the sum of harvested and ending volume. Cutting areas formed by spatial optimization often deviated from compartment boundaries.

Comparing Traditional Longitudinal Modeling Strategies of Forestry with Mixed-Effects Models: Restrictions in Model Formulation - Brock Stewart; Lewis Jordan; Rongxia Li (Forest Science, 2011)
Generalized algebraic difference approach and site index models, which are commonly fitted to repeated-measures data in forestry, are formulated by specifying that one or more regression parameters depend on a single, common subject-specific quantity. Their formulation leads to shortcomings not present with “effects” types of formulations, which involve specifying each subject-specific regression parameter as depending on at least one local quantity that no other parameters depend on. We give conceptual illustrations as well as empirical examples using published models.

What Drives Daily Volatility in Lumber Futures Markets? - Berna Karali (Forest Science, 2011)
Most financial asset returns exhibit volatility persistence. This article investigates this phenomenon in the context of daily returns in lumber futures markets. The volatility of lumber futures is found to vary with different phases of the United States-Canada softwood lumber trade dispute. Daily price volatility was the highest in the post-Softwood Lumber Agreement period (2001–2005), followed by the Softwood Lumber Agreement period (1996–2000) and the period with trade disputes and temporary tariffs (1992–1995). An inverse relationship between inventory levels and volatility is found. Further, the inventory effect on volatility varies across the different periods of the trade dispute. An inverse relation between time to delivery and volatility is also found. Moreover, it is shown that although volatility persistence exists in the lumber futures market, the time gap between the arrival of news to the markets and the delivery time of futures contracts is the fundamental variable in explaining volatility persistence.

Modeling Crown Structure from LiDAR Data with Statistical Distributions - Quang V. Cao; Thomas J. Dean (Forest Science, 2011)
The objective of this study was to evaluate the ability of three statistical distributions to characterize the vertical distribution of foliage mass in canopies of even-aged loblolly pine stands, based on airborne-scanning light detection and ranging (LiDAR) data. The functions were the Weibull and SB distributions and a mixture of the lognormal and Weibull distributions. Results indicated that the mixture distribution fit the LiDAR data better than the Weibull and SB distributions, according to three goodness-of-fit statistics. By switching from the lognormal for data near the tree top to the Weibull for data near the base of the crown, the mixture distribution seemed to better resemble the shape of the distribution of LiDAR returns than the Weibull alone. The mixture distribution was particularly effective for plots in which distributions of the returns were too peaked for either the Weibull or SB.

Correction: Munn, I., A. Hussain, D. Hudson, and B.C. West. 2011. Hunter Preferences and Willingness to Pay for Hunting Leases. For. Sci. 57(3):189–200. (Forest Science, 2011)

An Exploratory Study of Biomass Harvesting among Logging Firms in Virginia and North Carolina - John F. Munsell; Scott M. Barrett; M. Chad Bolding (Forest Science, 2011)
Logging firms in the United States will need to harvest and transport woody biomass if national wood-based renewable energy production goals are to be achieved. Expansion of associated biomass markets could provide important revenue opportunities for logging firms and potentially alter the sector. To study biomass harvesting behavior among logging firms, a logistic regression model was developed using a backward likelihood ratio procedure and 114 Virginia and North Carolina logging firms that operate in proximity to established woody biomass markets. The sample was identified from a larger pool of firm owners who participated in a Virginia Sustainable Harvesting and Resource Professional (SHARP) Logger Program survey. Hypothesized predictors included logging operation and owner variables. Confirmatory factor analysis was used to verify the underlying structure of summated latent constructs. The model correctly classified biomass harvesting 78% of the time, exhibited acceptable fit, and contained normally distributed residual error. Significant predictors included firm mechanization, haul distance, and owner perspectives regarding job security satisfaction and attitudes about biomass harvesting. Analysis of variance and χ2 were used to test for differences between significant predictors when factored across a three-point biomass market-action variable—no market, market/no harvest, and market/harvest. The follow-on market-action evaluations included firms from the SHARP Logger Program survey that share county-level centers of operation for which at least one of the firms noted proximity to a woody biomass market. Implications for logging sector research are discussed, along with practical considerations for regions where wood-based renewable energy initiatives are on the rise.

The Effect of Timber Harvesting Guidelines on Felling and Skidding Productivity in Northern Minnesota - Denys Goychuk; Michael A. Kilgore; Charles R. Blinn; Jay Coggins; Randall K. Kolka (Forest Science, 2011)
Substantial investment has been made in the development and application of scientifically based best management practices (i.e., guidelines) intended to protect and enhance the ecological, environmental, and aesthetic attributes of forest resources. When correctly applied, guidelines can increase environmental benefits on site and to adjacent resources, as well as improve forest health and productivity. We empirically evaluated how varying degrees of application of Minnesota's Timber Harvesting and Forest Management guidelines, along with operator and tract-specific variables, affect felling and skidding productivity of mixed aspen/hardwood/conifer stands in northern Minnesota. To do so, felling and skidding productivity data from five mechanized logging businesses were collected on 52 clearcut harvest blocks in northern Minnesota from August 2006 to May 2007 using time-motion and geospatial sensors. Additional postharvest data were collected for each block using high-resolution aerial photography and detailed on-site inventories. With use of these data, separate regression models were developed to estimate the impact that timber harvesting guidelines and tract and operator variables have on felling and skidding productivity. Results of regression analyses and diagnostic tests showed that felling productivity is influenced not only by guideline variables but also by tract and operator variables. Skidding productivity is influenced by both guideline and tract variables. The error terms of the separate felling and skidding models are statistically correlated, calling for their simultaneous estimation using a method known as seemingly unrelated regression. Specific explanatory variables that are statistically significant in explaining felling productivity include the logger's use of a preharvest site map and/or preharvest meeting with the forester, harvesting in winter, merchantable timber volume per unit area, and the operator. Variables that are statistically significant in explaining skidding productivity are the area of landings and skid trails as a percentage of the harvest area, ratio of the harvest block perimeter to the block area, slope, and merchantable timber volume per unit area. The findings suggest that implementing the guidelines we studied has minimal effect on felling productivity, although several adversely affect skidding productivity. By considering how to lay out the harvest block to facilitate skidding efficiency, a feller operator may be able to reduce the impact of some guidelines on skidding productivity.

Effects of Stand and Inter-Specific Stocking on Maximizing Standing Tree Carbon Stocks in the Eastern United States - Christopher W. Woodall; Anthony W. D'Amato; John B. Bradford; Andrew O. Finley (Forest Science, 2011)
There is expanding interest in management strategies that maximize forest carbon (C) storage to mitigate increased atmospheric carbon dioxide. The tremendous tree species diversity and range of stand stocking found across the eastern United States presents a challenge for determining optimal combinations for the maximization of standing tree C storage. Using a nationwide annual forest inventory, we quantified trends in standing tree C across a variety of species mixtures and stocking attributes for 24 of the most common tree species in the eastern United States. We found that as interspecific stocking decreased, such that the majority of stand stocking was in a single species, maximum live tree aboveground carbon (AGC) decreased by 33% in highly stocked stands across all study species. Maximum standing dead tree AGC was not correlated with stand stocking but instead was related to interspecific stocking with AGC storage being reduced by more than 50% as stands became progressively occupied by one tree species. Although the competitive interactions between individual species and/or functional groups (i.e., shade tolerance) can greatly complicate efforts to assess forest C storage opportunities, some basic tenets identified in this study may refine future research hypotheses and broadly identify species mixtures and associated stocking levels that may maximize AGC storage.

On Relative Maxima of Diameter Growth, Basal Area Growth, Volume Growth, and Mean Annual Increment for Individual Trees - Thomas B. Lynch; Difei Zhang (Forest Science, 2011)
A mathematical demonstration for the fact that maximum individual tree diameter growth occurs at an earlier age than maximum individual tree basal area growth is reviewed. This demonstration assumes that the growth functions are continuous, are twice differentiable with respect to age, and increase monotonically to one maximum, thereafter to decline monotonically. The relationship of the age of maximum individual tree volume growth to the age of basal area growth is also discussed. Mathematical demonstrations are given for the fact that the culmination of mean annual increment occurs earlier for diameter than for basal area, and results on age of maximum growth and mean annual increment are also given for arbitrary power functions in diameter.

Kernel Regression of Directional Data with Application to Wind and Wildfire Data in Los Angeles County, California - Haiyong Xu; Kevin Nichols; Frederic P. Schoenberg (Forest Science, 2011)
This article describes a method of kernel regression that can be used to investigate the relationship between a directional explanatory variable and a real-valued response variable. Cross-validation and bootstrap methods for obtaining sensible bandwidths and standard error estimates are also described. The proposed method is applied to wildfire and meteorological data from Los Angeles County, California, with the goal of summarizing and quantifying the impact of wind direction on the total area burned in wildfires ignited on a particular day. The results confirm that winds blowing from the northeast and east are associated with the ignition of wildfires of significantly larger burn areas than winds from other directions; the mean burn area of wildfires ignited on days with winds from the northeast is approximately 4.7 times that associated with the winds from the southwest. A major reason for this increase in burn area is confounding of wind direction with meteorological variables such as temperature, wind speed, and humidity, but even when generalized additive modeling is used to control for these meteorological variables, winds from the northeast are still associated with the ignition of fires of substantially larger burn areas.

Spatial Optimization of Wildlife Populations with Probabilistic Habitat Connections - Alain Billionnet (Forest Science, 2011)
I consider a land area divided into cells and the problem that consists of determining the cells that must be harvested and the cells that must be left in old-growth to maximize the size of wildlife populations that depend on amounts of young- and old-growth forest. In each old-growth cell, the size of the old-growth-dependent population depends on the spatial arrangement of the old-growth cells, specifically of the probability that the cell is connected to at least one other old-growth cell. This problem suggested by Hof and Bevers can be easily formulated by a difficult nonlinear 0-1 program. These authors proposed a linear approximation of a special case of the pairwise connection probabilities. The aim of this article was to show that the problem can be solved simply and efficiently with any set of connection probabilities by using standard 0-1 linear programming software. The key feature to transform the nonlinear program into a linear program is an approximation of the logarithmic function curve by some of its tangents. Computational results on hypothetical grid forests with up to 900 cells are presented to illustrate potentialities of the approach. Near-optimal solutions guaranteed to be within 0.5% of the optimal solution are obtained in less than 10 minutes of computing time.

Testing for Nonlinear Spatial Integration in Roundwood Markets - Kurt Niquidet; Bruce Manley (Forest Science, 2011)
Prior studies have frequently not supported spatial market integration and the law of one price in roundwood markets. However, these studies have relied on cointegration tests that have low power in the presence of nonlinearities. Roundwood markets may display these effects due to high transactions costs between regions. In this article, we revisited the question of spatial integration in roundwood markets by using tests that have no cointegration as a null hypothesis and threshold cointegration as an alternative. For testing, a dataset of monthly New Zealand roundwood prices from four regional markets over the period from January 1995 to April 2010 were used. Similar to standard linear cointegration tests, the null hypothesis of no cointegration could not be rejected for most of the regional price pairs. One interpretation is that regional markets are segregated. Another interpretation is that the power of these nonlinear tests, although an improvement over that of their linear counterparts, is still relatively low.

Spatiotemporal Relationships between Climate and Whitebark Pine Mortality in the Greater Yellowstone Ecosystem - Jeffrey T. Jewett; Rick L. Lawrence; Lucy A. Marshall; Paul E. Gessler; Scott L. Powell; Shannon L. Savage (Forest Science, 2011)
Whitebark pine (Pinus albicaulis) serves as a subalpine keystone species by regulating snowmelt runoff, reducing soil erosion, facilitating the growth of other plants, and providing food for wildlife. Mountain pine beetle (Dendroctonus ponderosae) is an ideal bioindicator of climate change, because its life cycle is temperature-dependent. Western North America is currently experiencing the largest outbreak of mountain pine beetle on record, and evidence suggests that a changing climate has accelerated the life cycle of this bark beetle. This study explored the relationships between climate, mountain pine beetles, and whitebark pine mortality in the Greater Yellowstone Ecosystem. A time series of Landsat satellite imagery (nine images) was used to monitor whitebark pine mortality in the Greater Yellowstone Ecosystem from 1999 to 2008. The patterns of mortality were analyzed with respect to monthly climate variations over the 9-year period. The impacts of topography and autocorrelation (both spatial and temporal) were also analyzed. The most important predictor variables were autocorrelation terms, indicating a strong host-tree depletion effect. Both drier and warmer climatic conditions favored increased whitebark pine mortality. These results show for the first time a statistical link between climate variability and whitebark pine mortality, probably mediated by mountain pine beetles.

The Effects of Road Quality and Other Factors on Water-Based Recreation Demand in Northern Ontario, Canada - Len M. Hunt; Adam Dyck (Forest Science, 2011)
Resource managers are often faced with difficult decisions regarding the management of unpaved roads in forested environments. These decisions are complicated by the lack of information about ways that people use roads for leisure activities such as outdoor recreation. In this study, we assessed how the quality of roads and trails affected the demand for water-based recreation in northern Ontario, Canada. To make this assessment, we tested and controlled for several other factors that might influence this demand. The results from a random-effects, negative binomial regression of traffic counts to water-based settings suggested that demand was higher when road quality to sites was better, sites were in close proximity to human settlements, and large-sized water bodies that held desirable fish species were available. Furthermore, demand was higher when weather was warmer and drier, when people had more leisure time (i.e., weekends, statutory holidays, and summer), when wind speeds were low on large-sized water bodies, and when fuel costs were lower. The relative effect of road quality on counts was strongest of all of these factors. In fact, moving from a trail to a medium- or high-quality road was predicted to increase demand for water-based recreation by more than 200%. By understanding this direct effect of road quality along with the importance of other factors for water-based recreation demand, resource managers can carefully plan all stages of road management (i.e., creation, maintenance, and closure/removal of roads) to either encourage or discourage use.

Canopy Structure in a 650-Year Douglas-Fir Chronosequence in Western Washington: Distribution of Canopy Elements and Open Space - Roman J. Dial; Nalini M. Nadkarni; Charles D. Jewell (Forest Science, 2011)
Using within-canopy, side-viewing light detection and ranging (LiDAR), we measured canopy structure in a Douglas-fir (Pseudotsuga menziesii) chronosequence. We present foliage profiles, canopy composition, and a new metric quantifying the vertical distribution of open space, supporting and extending results from other structural studies. Foliage distribution shifted from vertically uniform in the youngest stand (50 years), to a canopy surface peak in mature forests (100–160 years old), to a near-ground maximum in old-growth (650 years). Leaf area index in old-growth and mature forests was similar but was smaller in young forest. Canopy composition changed with age: relatively more dead elements in young, boles in mature, and diversity in old-growth canopies. Older forest had greater mean and variance in open space than younger forests. Open space was vertically uniform in young, unimodal in mature, and greatest in the upper canopy in old-growth forests. Our results provide an integrated description of canopy structure over more than half a millennium, highlighting solid structure and its complement, open space. The unique element we present—open space—provides novel insights into the assessment of forest structure. This study provides a means to compare forests across ages, from immature to old-growth, with an additional canopy variable available for developing relationships between canopy structure and function.

Evaluating Tree Species Spatial Diversity Based on Neighborhood Relationships - Gangying Hui; Xiuhai Zhao; Zhonghua Zhao; Klaus von Gadow (Forest Science, 2011)
This contribution presents a method for describing forest tree species diversity based on the analysis of tree neighborhoods. The proposed measure of tree species spatial diversity (TSS) is compared with four commonly used diversity indices using empirical and simulated data. The empirical dataset includes field observations with known tree coordinates from different forest types in China, Mongolia, Mexico, Germany, Myanmar, and South Africa. The simulated set uses 12 specifically designed patterns of spatial species mingling. The results show that the value of the TSS criterion increases with increasing tree species richness. In addition, TSS is sensitive to rare species and to variations in community structure, including species spatial isolation and spatial mingling. For these reasons, the TSS criterion is much more effective for measuring tree species diversity than the commonly used indices. It allows detailed interpretation of forest spatial diversity and of forest structural modifications after selective thinnings in multispecies forests. A particular advantage of the TSS index is the fact that its assessment, which is based on neighborhood relations, can be easily integrated in routine forest management surveys at practically no additional cost.

A Parsimonious Dynamic Stand Model for Interior Spruce in British Columbia - Oscar García (Forest Science, 2011)
A whole-stand growth model, Scube, was developed for spruce-dominated, even-aged, natural and planted stands, using permanent sample plot data from the sub-boreal spruce biogeoclimatic zone of British Columbia, Canada. Available data were limited, with no information on mature planted stands or thinning treatments. A parsimonious model design, incorporating knowledge of stand dynamics and experience from other forests, made possible a logical reproduction of observed behavior and plausible extrapolations to other conditions. Scube consists of a system of four differential equations, describing the evolution of four state variables: top height, trees per hectare, basal area, and a stand closure indicator. Concepts of closure and site occupancy drive the behavior of young stands and the response to thinning. Parameters were estimated through numerical optimization of several residual functions, reflecting different projection interval types and weighting strategies. Differences in estimates among the various criteria were small. Calculations are facilitated through expressions that remain invariant in the absence of disturbances. The methods generalize the algebraic difference approach and related forest modeling techniques, linking them to standard dynamical systems theory.

Examining the Gain in Model Prediction Accuracy Using Serial Autocorrelation for Dominant Height Prediction - Mingliang Wang; Jagtar Bhatti; Yonghe Wang; Thierry Varem-Sanders (Forest Science, 2011)
Within-subject serial correlation (autocorrelation) has long been a concern in forest growth and yield modeling but has been ignored for predictive purposes in most studies. In this study, we used linear prediction theory combined with linearized (with respect to random effects) nonlinear mixed models to investigate the improvement in model prediction achieved with autocorrelation. In this setting, predictions rely on estimates of common parameters obtained from a set of previous growth series and prior observations of new growth series, allowing the response variable for the new series to be projected either backward or forward in time. The prediction gains associated with using autocorrelation were evaluated using stem analysis data sets for black spruce (Picea mariana [Mill.] BSP) and red alder (Alnus rubra Bong.). The evaluations involved splitting the data and comparing models with one or more random parameters, with and without use of autocorrelation. Autocorrelation improved the projection of dominant height (site index) over short ranges (10–20 years), but the gain was trivial for the long range (>20 years). Consequently, in cases of dominant height projection based on one single observation, for practical purposes, autocorrelation can be ignored in both model-fitting and prediction stages. Cross-comparison between models with different random effects indicated that simple models with one random effect had the best predictive performance. Rather than excluding such models solely on the basis of certain fit statistics, it is recommended that the predictive abilities of models with a single random effect be evaluated, with and without correlated errors, relative to their counterparts with more random effects.

Fuel Complex Alterations Associated with Spruce Beetle-Induced Tree Mortality in Intermountain Spruce/Fir Forests - Carl Arik Jorgensen; Michael James Jenkins (Forest Science, 2011)
Tree mortality caused during extensive outbreaks of spruce beetle (Dendroctonus rufipennis Kirby [Coleoptera: Curculionidae]) has been assumed to increase hazardous fuel loads and consequently influence fire behavior, occurrence, and effects. However, little research has been done to quantify or qualify how spruce beetle-induced tree mortality may alter fuel complexes during the course of an outbreak. The objective of our research was to determine how fuel complexes differ between stands with endemic populations of spruce beetle, stands experiencing current outbreaks, and stands with postoutbreak spruce beetle-induced tree mortality. We measured ground, surface, and aerial fuels in spruce–fir stands assigned into one of three spruce beetle condition classes: endemic, epidemic, or postepidemic. These stands were located on the Manti-LaSal and Fishlake National Forests in southcentral and southern Utah. We used analysis of variance (ANOVA) to compare mean differences in stand attributes and fuel variables between the three spruce beetle condition classes. The mean amount of down woody surface fuel (tonnes/ha) in the 100-hour size class in epidemic stands was significantly greater than that in endemic stands. Mean litter depth and amount was significantly greater in epidemic stands than in endemic and postepidemic stands. A significant increase for most estimates of live and dead herbaceous material was detected in epidemic stands and postepidemic stands compared with that in stands not affected by the spruce beetle. Likewise, significant increases in live shrub material were detected in postepidemic stands. Spruce–fir stands also had significantly less live aerial fuels after outbreaks than endemic stands.

Investigating the Utilization of Potassium Fertilizer in a Pinus patula Schiede Ex Schltdl. & Cham. Plantation - Jacob W. Crous; Andrew R. Morris; Mary C. Scholes (Forest Science, 2011)
Previous research indicated that the application of phosphorus (P) and potassium (K) fertilizer to Mexican weeping pine (Pinus patula Schiede ex Schltdl. & Cham.) on gabbro-derived soils was necessary to correct a second rotation yield decline. To plan efficient fertilization of subsequent rotations, the fate and utilization of the applied K fertilizer was investigated using the rubidium (Rb)/K reverse tracer technique whereby the naturally occurring Rb in the soil was used as an indicator of native soil K. At the age of 15 years, samples from the soil, forest floor, bark, wood and live foliage were collected from a trial in which various amounts of P and K fertilizer were applied at different stages of stand development. No significant quantity of the applied K remained in the soil at the end of the 15-year rotation, but sufficient plant-available P remained on plots where 80 kg ha−1 P and K was applied. Significantly greater quantities of P per ha were found in the forest floor, wood, and foliage on the plots that received 40 or 80 kg ha−1 P and K compared with the control. The application of 80 kg ha−1 P and K increased the P content of the wood and foliage over that recorded in the 40 kg ha−1 P and K treatment. The application of 80 kg ha−1 P and K increased the K content of the forest floor and foliage compared with that of the control. Across all PK quantities, fertilizer K contributed 28, 17, and 8% to the quantity of K in the wood, bark, and foliage, respectively. The export of up to 52 kg K ha−1 from the site in wood and bark will necessitate the reapplication of at least 104 kg K ha−1 to the subsequent rotation to produce timber sustainably on the gabbro-derived soils at Usutu.

Estimating Riparian Understory Vegetation Cover with Beta Regression and Copula Models - Bianca N. I. Eskelson; Lisa Madsen; Joan C. Hagar; Hailemariam Temesgen (Forest Science, 2011)
Understory vegetation communities are critical components of forest ecosystems. As a result, the importance of modeling understory vegetation characteristics in forested landscapes has become more apparent. Abundance measures such as shrub cover are bounded between 0 and 1, exhibit heteroscedastic error variance, and are often subject to spatial dependence. These distributional features tend to be ignored when shrub cover data are analyzed. The beta distribution has been used successfully to describe the frequency distribution of vegetation cover. Beta regression models ignoring spatial dependence (BR) and accounting for spatial dependence (BRdep) were used to estimate percent shrub cover as a function of topographic conditions and overstory vegetation structure in riparian zones in western Oregon. The BR models showed poor explanatory power (pseudo-R2 ≤ 0.34) but outperformed ordinary least-squares (OLS) and generalized least-squares (GLS) regression models with logit-transformed response in terms of mean square prediction error and absolute bias. We introduce a copula (COP) model that is based on the beta distribution and accounts for spatial dependence. A simulation study was designed to illustrate the effects of incorrectly assuming normality, equal variance, and spatial independence. It showed that BR, BRdep, and COP models provide unbiased parameter estimates, whereas OLS and GLS models result in slightly biased estimates for two of the three parameters. On the basis of the simulation study, 93–97% of the GLS, BRdep, and COP confidence intervals covered the true parameters, whereas OLS and BR only resulted in 84–88% coverage, which demonstrated the superiority of GLS, BRdep, and COP over OLS and BR models in providing standard errors for the parameter estimates in the presence of spatial dependence.

Effects of Initial Spacing on Height Development of Loblolly Pine - Clara Antón-Fernández; Harold E. Burkhart; Mike Strub; Ralph L. Amateis (Forest Science, 2011)
The relationship between dominant height and age is the base of site index, the most widely used measure of site quality. In applying the site index concept, one typically assumes that height development is not affected by stand density or thinning treatment. This assumption has been challenged by recent studies on loblolly pine. A detailed data set with initial densities ranging from 6,730 to 750 trees/ha and covering ages 1 through 25 after plantation establishment was used to study and model the effect of initial spacing on height development of loblolly pine. Dominant height was found to be dependent on initial spacing. Height-age models are proposed that take into account the effect of spacing on average and dominant height. The differences among plantation densities are evident from age 6 and are consistent to the end of the 25-year period of study. Previous studies in other conifers have reported an early advantage in terms of height growth in denser stands that tend to disappear with age, producing a crossover of the growth trajectories. No evidence of this crossover effect in height was found.

Hunter Preferences and Willingness to Pay for Hunting Leases - Ian Munn; Anwar Hussain; Darren Hudson; Ben C. West (Forest Science, 2011)
Previous analyses of hunting leases need to be refined by addressing the decision to lease, incremental willingness to pay (WTP) for those already leasing, and number of leases purchased. Requisite data for this study were generated on the basis of a survey of Mississippi resident and nonresident hunters. Results suggested that a hunter decision to purchase a lease was influenced by hunting avidity, availability of alternative hunting access options, perceived hunter crowding on public lands relative to private lands, and household income, whereas the number of leases purchased was influenced by alternative access options and hunter perception of congestion on public lands compared with that on private land. Thus, factors influencing the decision whether or not to purchase a lease and number of leases purchased were not the same. Incremental median WTP ranged from $0.56 to $6.40 per acre, depending on alternative hunting access options, hunter perception of crowding on public lands, availability of game species on leased lands, and duration of the lease agreement. This result suggested that Mississippi landowners who currently allow hunting access may be able to enhance lease-related total gross annual financial returns by $800 to $9,200 if they improved management of their lands or modified their lease agreements consistent with hunters' genuine concerns.

Modeling Jack Pine ( Pinus banksiana ) Foliage Density Distribution - Robert Schneider; Mathieu Fortin; Frank Berninger; Chhun-Huor Ung; D. Edwin Swift; S.Y. Zhang (Forest Science, 2011)
The vertical distribution of foliage biomass is important because it is associated with photosynthesis and is closely related to some wood quality attributes such as branch diameter and sapwood content. In this article we propose a model to predict foliage biomass distribution within the crown for jack pine trees in Eastern Canada. This model has two parts. The first one distinguishes the proportion of nodal (formed at the end of each yearly shoot) and internodal (formed during the growing season) foliage biomass. The second part of the model predicts the distribution of the biomass depending on the type of foliage (nodal or internodal). This second part is based on a two-parameter beta cumulative distribution function (cdf). The parameterization of this cdf was performed using a mixed-effects nonlinear regression. The proportion of foliage biomass found in the nodal whorls is proportional to dbh and age and inversely proportional to total height. The distribution of the foliage biomass in the nodal whorls is dependent only on tree-level variables whereas the internodal foliage biomass is influenced by both tree- and stand-level variables. The internodal foliage biomass maximum is closer to the crown base than that of nodal foliage biomass. Decomposing the distribution into whorl types leads to a better description of crown characteristics.

Study of Shrub Cover and Height Using LIDAR Data in a Mediterranean Area - Javier Estornell; Luis Angel Ruiz; Borja Velázquez-Marti (Forest Science, 2011)
In this work we studied the height and coverage of shrub vegetation using light detection and ranging (LIDAR) data. The maximum dominant heights of vegetation were measured in the field in 83 stands of a 0.5-m radius, and the data were compared with figures for heights obtained from LIDAR data in concentric areas with different radii. The minimum root mean square error (RMSE) between the field measurements and LIDAR data was found for radii between 1.5 and 2.25 m, RMSE being 0.26 m. When the slopes are low and an accurate digital terrain model is obtained, it was shown that the radius can be reduced. Shrub heights were also studied in plots of 100 m2. In this case, the 95th percentile of the LIDAR data included in each plot was the best predictor of height with R2 of 0.71 and a RMSE of 0.13 m. For detecting the presence of shrub vegetation, the highest accuracy was obtained when the canopy height model and a spectral image were combined (overall accuracy of 90%).

Modeling and Prediction of Tree Height–Diameter Relationships Using Spatial Autoregressive Models - Junfeng Lu; Lianjun Zhang (Forest Science, 2011)

Diversity of Shrub-Dwelling Arthropods to Thinning of Young Douglas-Fir Forests in the Pacific Northwest, USA - Hoonbok Yi; Andrew Ralph Moldenke (Forest Science, 2011)
We examined an unthinned control stand and three different thinning intensities in 40- to 60-year-old Douglas-fir forests in western Oregon to assess the effects of thinning on the abundance, species richness, and diversity of shrub-dwelling arthropods. Shrub-dwelling arthropods, collected with a bagging technique, decreased significantly as thinning intensity increased in deciduous foliage (vine maple, Acer circinatum Pursh), but arthropods showed no response to thinning on the two types of conifer foliage (Douglas-fir, Pseudotsuga menziesii [Mirb.] Franco and western hemlock, Tsuga heterophylla [Raf.] Sarg.). The species richness and diversity of shrub-dwelling arthropods showed significantly higher values on the coniferous branches than on the deciduous foliage. Functional group composition for the two foliage types revealed consistently different proportions. Deciduous branch supported a higher proportion of sapsuckers and leaf chewers, and conifer branch hosted a higher proportion of predators and detritivores. Nonmetric multidimensional scaling ordination showed a distinct difference between the species assemblages inhabiting the deciduous and conifer branches. The effects of thinning on the arthropods were complex. Seasonal effects on arthropods exceed treatment effects because the species composition in the dry season was very different from that in the wet season. The shrub-dwelling arthropod community reveals little seasonal difference on coniferous branch, but significant differences occur on deciduous branch. In this study, treatment effects were very limited, but our results indicate that as thinning increased, the response of arthropod community on deciduous branch increased more. This large-scale experiment provided an opportunity to assess responses of shrub-dwelling arthropods to levels and patterns of forest management.

Estimating Wood Volume of the Stem and Branches of Sugar Maple ( Acer saccharum Marsh.) Using a Stem Profile Model with Implicit Height - Wojciech T. Zakrzewski (Forest Science, 2011)
A taper model-based solution for estimating volume of wood in sugar maple (Acer saccharum Marsh.) in Ontario, Canada, is presented. This practical procedure, using a reformulated version of the 1999 taper model of Zakrzewski, requires measuring only dbh and produces estimates of commercial wood volume allocated in stems and (or) branches, along tree length. The suggested methodology allows tree height to be treated as an implicit variable: either unobserved or unobservable (latent). Using the dbh-based taper model, a standard height/dbh curve may be generated without height measurements. The methodology presented here may be also treated as a modeling framework for developing dbh-based biomass equations as well as for investigating spatial allocation of wood within trees, e.g., for studying the influence of the competitive environment (forest stand density) of a tree on height growth. Sample data used were measurements from 1,113 sugar maple trees from Ontario's Algonquin region.

Improving Tree Age Estimates Derived from Increment Cores: A Case Study of Red Pine - Shawn Fraver; John B. Bradford; Brian J. Palik (Forest Science, 2011)
Accurate tree ages are critical to a range of forestry and ecological studies. However, ring counts from increment cores, if not corrected for the years between the root collar and coring height, can produce sizeable age errors. The magnitude of errors is influenced by both the height at which the core is extracted and the growth rate. We destructively sampled saplings and small trees of red pine (Pinus resinosa Ait.) and combined within- and between-tree cross-dating to determine accurate rings counts and radial growth rates for 11 stem sections of each sample. We developed regression models to estimate age adjustment as a function of coring height and radial growth rate. We compared candidate models using corrected Akaike's information criterion scores, and we evaluated model performance by jackknife permutations. Application of our best-fit equations clearly improved age estimates: compared with unadjusted ring counts, our adjusted age estimates had normally distributed errors centered near 0, lower standard deviations, and a narrower range of values. Thus, these equations can be used to adjust ages of cored, mature trees occurring in these same settings. The methods used here may be applied to other shade-intolerant or mid-tolerant species where improved tree establishment dates are needed.

Sampling Strategies for Efficient Estimation of Tree Foliage Biomass - Hailemariam Temesgen; Vicente Monleon; Aaron Weiskittel; Duncan Wilson (Forest Science, 2011)
Conifer crowns can be highly variable both within and between trees, particularly with respect to foliage biomass and leaf area. A variety of sampling schemes have been used to estimate biomass and leaf area at the individual tree and stand scales. Rarely has the effectiveness of these sampling schemes been compared across stands or even across species. In addition, sample size estimates for achieving a certain level of precision have rarely been given. This simulation study used extensive branch and tree foliage biomass data sets for Douglas-fir (Pseudotsuga menziesii var. menziesii [Mirb.] Franco) and ponderosa pine (Pinus ponderosa Dougl ex. Laws.) to compare alternative sampling schemes and sample sizes. The use of auxiliary information at the estimation phase resulted in a more cost-efficient sampling scheme than when auxiliary information was used at the design phase. However, using auxiliary information at the design phase resulted in more precise estimates than using the same at the estimation phase for the same sample size. For both species, systematic sampling with ratio estimation provided the most efficient estimate of individual tree foliage biomass. In Douglas-fir, stratifying by branch type (i.e., whorl versus interwhorl) resulted in a marginal gain in precision. For Douglas-fir, on average, root mean square error decreased by 43.1% when sample size increased from 6 to 12 branches per tree, with a further decrease of 24.3% when sample size increased from 12 to 18 branches per tree. For ponderosa pine, on average, the root mean square error decreased by 44.4 and 23.9% when the sample size was increased from 6 to 12 and from 12 to 18 branches per tree, respectively. Additional work is needed to understand the appropriate sampling techniques for older conifer tree crowns and sampling multileader deciduous crowns.

Modeling the Effect of Midrotation Fertilization on Specific Gravity of Loblolly Pine ( Pinus taeda L.) - Finto Antony; Laurence R. Schimleck; Daniel B. Hall; Alexander Clark; Richard F. Daniels (Forest Science, 2011)
Ring specific gravity, earlywood and latewood specific gravity, and percent latewood were measured on cores collected at breast height from a thinned and fertilized midrotation loblolly pine (Pinus taeda L.) plantation in the lower Coastal Plain of North Carolina. The study was laid out in a randomized complete block design receiving four levels of nitrogen (N) fertilizer in 1984: 000 (control), 112, 224, and 336 kg/ha plus 28 kg/ha of phosphorus with each treatment. A consistent pattern of response was observed in latewood specific gravity (LWSG) after the application of different levels of fertilizer and used as a variable for modeling. The LWSG profiles of unfertilized trees followed a nonlinear relation with ring number from pith. A three-parameter asymptotic function was used to explain the LWSG profile of unfertilized trees with ring number as a covariate. Application of N reduced LWSG and was modeled using a two-parameter response function with year since fertilization as a covariate and separate parameter estimates for each fertilization level. On the basis of the model, the magnitude of maximum cumulative response was −0.025, −0.049, and −0.074 attained at 3.7, 1.9, and 0.8 years after fertilization for the 112, 224, and 336 kg/ha treatments, respectively.

Do Taste and Quality Perception Influence Consumer Preferences for Wood? An Econometric Model with Latent Variables - Sandrine Costa; Serge Garcia; Lisette Ibanez (Forest Science, 2011)
The aim of our article was to understand consumer preferences for wood and competitive materials. Assuming that a wood product is composed of various attributes, we consider that consumers' choices are not guided by observed characteristics but, instead, by the quality perception consumers have of these attributes. An econometric model integrating this factor by means of latent variables allows us to analyze the influence of individual characteristics and information (external sources and/or experience) on product quality perception. We also include consumers' attitudes in the model by supposing that the importance consumers place on attributes accurately describes their tastes. Data on material choices (wood versus vinyl) for window frames validate our assumptions.

Estimating a Multilevel Dominant Height–Age Model from Nested Data with Generalized Errors - Yuqing Yang; Shongming Huang (Forest Science, 2011)
A dominant height-age model was developed following a multilevel nonlinear mixed-model approach. Random effects were modeled at the plot and the tree levels, with two random parameters at each level. In addition to the random effects, a variance function was used to model heteroscedasticity, and various covariance structures were evaluated to account for residual autocorrelation. A new covariance structure, the modified spatial power structure, is proposed. This new structure was found to provide the best fit to the model. Although residual autocorrelations were still not completely removed by this structure, they were substantially reduced. Model validation results using an independent data set confirmed that the final model with the modified spatial power structure produced more accurate and precise dominant height predictions. This was true for both expansion methods, and the empirical best linear unbiased predictor (EBLUP) expansion showed better results than the ZERO expansion. The model with the modified spatial power structure fitted by the EBLUP expansion method, therefore, was chosen as the preferred model for making tree-specific, dominant height predictions. The advantages and relevance of the multilevel nonlinear mixed-model approach for forest growth and yield modeling are discussed.

Simulating Fire and Forest Dynamics for a Landscape Fuel Treatment Project in the Sierra Nevada - Brandon M. Collins; Scott L. Stephens; Gary B. Roller; John J. Battles (Forest Science, 2011)
We evaluated an actual landscape fuel treatment project that was designed by local US Forest Service managers in the northern Sierra Nevada. We modeled the effects of this project on reducing landscape-level fire behavior at multiple time steps, up to nearly 30 years beyond treatment implementation. In addition, we modeled planned treatments under multiple diameter-limited thinning scenarios to assess potential impacts on fuel treatment effectiveness. The planned fuel treatments reduced modeled conditional burn probabilities substantially across the landscape relative to those for a scenario with no simulated treatments. This reduction relative to that for the no treatment landscape was evident approximately 20 years after simulated treatment implementation. Although diameter-limited thinning scenarios resulted in different residual forest stand structures, we detected no real differences in modeled landscape-level burn probabilities. The modeling adaptations we made with respect to fuel model selection and simulated ingrowth/regeneration over simulated time, as well as incorporation of variable winds in fire simulations, collectively contribute to a robust analysis of the study area.

The Use of Ground-Penetrating Radar to Accurately Estimate Soil Depth in Rocky Forest Soils - Eric B. Sucre; John W. Tuttle; Thomas R. Fox (Forest Science, 2011)
Ground-penetrating radar (GPR) is a geophysical tool that has the capability, given favorable soil properties, to improve the accuracy of soil depth estimation, compared with other commonly used methods. This study was conducted on three different physiographic regions across the southern Appalachian Mountains: the Ridge and Valley (n = 9), Cumberland Plateau (n = 6), and Allegheny Plateau (n = 6). At each site (n = 21), a 20- × 20-m measurement plot was scanned using both 200- and 400-MHz antennas to estimate average soil depth. Soil depth estimates obtained from both GPR antennas were compared with each other as well as with soil depth estimations obtained with a soil auger using a paired t test (α = 0.05). No significant differences in soil depth were observed for the 200- versus 400-MHz antennas (P = 0.913). Consequently, data recorded from the 400-MHz antenna were used when depth measurements between the GPR and soil auger were compared. This was done because of the smaller and lighter antenna size and better practicality (i.e., can be used by a single operator) compared with the heavier and bulky 200-MHz antenna. Across all plots (n = 21), depth estimations were shallower using a soil auger compared with estimates obtained using GPR across all plots (P = 0.0002). Results from this study demonstrate how current methods can underestimate soil depth in rocky forest soils. Depth estimations from GPR could be used to more accurately quantify site quality in the southern Appalachians by providing the precise data needed to calculate nutrient availability and water-holding capacity. Last, the reduction in size and weight of GPR antennas and computers now provides forest scientists a practical and powerful technology that should be revisited because it has been confined to very specific applications over the last 25 years.

Stabilized Soil Organic Carbon Pools in Subsoils under Forest Are Potential Sinks for Atmospheric CO2 - Klaus Lorenz; Rattan Lal; Martin J. Shipitalo (Forest Science, 2011)
The soil organic carbon (SOC) pool stored in subsoil horizons in forests plays an important role in the global carbon cycle. Strategies are needed to increase the subsoil SOC pool in forests because the turnover time of SOC increases with increase in soil depth as subsoil SOC is chemically and physically stabilized. We compared the total SOC and total nitrogen (TN) pools, chemically and physically separated SOC fractions, and C and N pools in fine roots in a soil pedon in an oak-hickory forest type consisting of white oak (Quercus alba L.) and red oak (Quercus rubra L.) with yellow-poplar (Liriodendron tulipifera L.) at the North Appalachian Experimental Watershed near Coshocton, Ohio, USA. The SOC pool was the highest in the A horizon (47.4 Mg ha−1) and smaller in the Bt1 (6.9 Mg ha−1) and Bt2 (6.7 Mg ha−1) horizons. The SOC and TN concentrations sharply decreased with depth. Fine root C and N pools were much larger in the A horizon (0.71 and 0.025 Mg ha−1) than in underlying horizons. Although only 22% of the SOC pool was stored below the A horizon, 58% of the chemically stabilized and 31% of the physically stabilized SOC fractions pool occurred in the subsoil horizons. Thus, studies are needed to test whether forest management can increase the stabilized SOC pool in subsoil horizons to mitigate the human-induced climate change.

Soil Carbon Change through 2 m during Forest Succession Alongside a 30-Year Agroecosystem Experiment - Scott Devine; Daniel Markewitz; Paul Hendrix; David Coleman (Forest Science, 2011)
Forest succession (FS) and no-till (NT) agriculture are generally assumed to have a beneficial effect on surficial soil organic C (SOC) stocks compared with conventional tillage (CT) management; however, land use effects to depths >30 cm remain uncertain. In this research we compared SOC contents and composition to 2 m under CT, NT, and FS at the 30-year Horseshoe Bend agroecosystem experiment in Athens, Georgia, USA. Soils from 0 to 2 m were fractionated into particulate organic C (POC) (53-2000 μm) and fine C (<53 μm) fractions, and bulk soil δ13C signatures were determined. Soils from 0 to 28 cm were dry- and wet-sieved to estimate aggregate stability. Soil solutions were also collected at 0, 15, and 100 cm for dissolved organic C (DOC) analysis. Full-profile (0-2 m) SOC storage is 52 Mg ha−1 in CT, 60 Mg ha−1 in NT, and 62 Mg ha−1 in FS. Significant differences are limited to 0-5 cm and are linked to enhanced aggregate stability under NT and FS. Increases in subsoil POC under FS and changes in soil δ13C and C/N ratio indicate that substantial subsoil C cycling has occurred. DOC fluxes at 0 cm were significantly greater under NT (200 kg ha−1 year−1) and FS (210 kg ha−1 year−1) than under CT (80 kg ha−1 year−1). DOC fluxes at 15 cm are estimated to be 20 kg ha−1 year−1 under CT and NT and 40 kg ha−1 year−1 under FS. At 100 cm, DOC fluxes are 2 kg ha−1 year−1, regardless of land use. An increase in FS POC of 2 Mg ha−1 from 15 to 100 cm outweighs cumulative differences in DOC input to this layer, implicating deep forest rooting and bioturbation as active mechanisms in subsoil C change. Whereas differences in SOC content were concentrated near the surface, dynamic changes in C cycling extend well below the plow layer.

Subsurface Carbon Contents: Some Case Studies in Forest Soils - Dale W. Johnson; James D. Murphy; Benjamin M. Rau; Watkins W. Miller (Forest Science, 2011)
This article evaluates the importance of deeper soil horizons for soil C inventories in forest ecosystems. For non-Spodosols, we categorized soils as to the degree of convexity of the cumulative soil C content profile. Soils with a highly convex or asymptotic soil C content profile contained a significantly lower fraction of their total C (36 ± 8%) below 20 cm than those with less convex (nonasymptotic) profiles (51 ± 2%), even though the more convex soils were 12 cm (23%) deeper. Spodosols contained the most C below 20 cm (66 ± 3%) as a result of the presence of spodic horizons. Spodosols also contained substantially more total soil profile C than non-Spodosols even though the average depths of sampling were similar. Langmuir and logarithmic equations predicted C contents of deeper horizons fairly well for most non-Spodosol soils, whereas C content declines systematically with depth. These equations were very poor for Spodosols, however, because of the increases in soil C with depth that often occur with spodic horizons. Two case studies from the Sierra Nevada mountains suggested that C concentration varies to a greater degree than does bulk density or fine earth (% <2 mm) content, thus illustrating the importance of obtaining good estimates of the large stone content, which can offset differences in C concentration when C content is calculated in the normal fashion (i.e., ignoring the >2-mm fraction). These case studies do not support the idea of estimating bulk density from soil C concentration.

Deep Soils - Rob Harrison; Dan Richter; Tom Fox (Forest Science, 2011)

Editor's Note - Edwin J. Green (Forest Science, 2011)

Initial Response of Soil Carbon and Nitrogen to Harvest Intensity and Competing Vegetation Control in Douglas-Fir ( Pseudotsuga menziesii ) Plantations of the Pacific Northwest - Robert A. Slesak; Stephen H. Schoenholtz; Timothy B. Harrington; Nathan A. Meehan (Forest Science, 2011)
We assessed the effect of harvest type (bole-only or whole-tree) and vegetation control treatments (initial or annual application of herbicide) on soil C and N at two contrasting sites in the Pacific Northwest. Pretreatment (2003) and posttreatment (2005) soil samples were collected by depth to 60 cm, and a stratified sampling approach based on four surface conditions was used for posttreatment sampling in surface soils. Surface condition had a significant effect on soil C and N concentrations, generally decreasing with decreasing amounts of logging debris and increasing soil disturbance. There was no difference between harvest treatments in the change in soil C and N content despite differences in surface condition coverage between harvest types, indicating estimates of C and N change determined from the stratification approach were imprecise. Soil C and N content tended to increase regardless of treatment, but increases were significant only in the bole-only harvest at one site and in the whole-tree harvest at the other site. Initial vegetation control caused significantly greater positive change in soil C and N than the annual vegetation control treatment, with effects limited to surface soil at one site and all sample depths at the other site. Much of these increases occurred in deeper (>20 cm) parts of the soil profile, indicating that deep soil sampling is necessary for assessment of harvest-related change in soil C and N.

Carbon Inputs and Water Uptake in Deep Soils of an Eastern Amazon Forest - Eric Davidson; Paul A. Lefebvre; Paulo M. Brando; David M. Ray; Susan E. Trumbore; Luis A. Solorzano; Joice N. Ferreira; Mercedes M. da C. Bustamante; Daniel C. Nepstad (Forest Science, 2011)
Rooting depth affects soil profiles of water uptake and carbon inputs. Here we explore the importance of deep roots in a mature tropical forest of eastern Amazonia, where a throughfall exclusion experiment was conducted to test the resilience of the forest to experimentally induced drought. We hypothesized that soil water depletion occurred below the depth previously measured by sensors in 11-m-deep soil pits and that only a small root biomass is necessary to affect water uptake and the isotopic signature of soil CO2. A noninvasive electrical profiling method demonstrated greater depletion of soil water in the 11-18 m depth increment in the exclusion plot compared with the control plot by the end of the 3rd year of the experiment. A fine root biomass of only 0.1 g/cm3 measured at 3-6 m was sufficient for soil water drawdown and for imparting an isotopic signature of modern soil 14CO2 in both plots. A soil 13CO2 profile indicated drought stress in the exclusion plot. Fine root inputs of organic C to deep soils are small with respect to the carbon dynamics of the forest, but the deep rooting habit clearly affects the ecosystem water balance and profiles of soil CO2.

Total Soil Carbon in the Coarse Fraction and at Depth - Darlene Zabowski; Nicol Whitney; Janita Gurung; Jeffrey Hatten (Forest Science, 2011)
Historically, most studies estimating soil carbon have been based almost exclusively on ≤2-mm soil particles (fine soil fraction) and generally excluded soil >2-mm (coarse soil fraction) or soil at >1-m depth. In fact, many studies have not examined soil carbon below 20 cm. This study was conducted to determine how much total soil C is underestimated by following traditional, or standard, soil sampling and analysis for both particle size fractions and depth. Seventeen soil series and one soil classified to the level of Great Group, were sampled in Alaska, Oregon, Puerto Rico, and Washington. Total soil C was quantified for the soil fine and coarse fractions, as well as for soil >1-m deep. Results of this study showed substantial soil C contained in the coarse soil fraction (<1-25%) and in soil greater than 1-m depth (3-48%). The combined exclusion of the coarse fraction and soil below 1 m could miss as much as one-half of the soil total C of a profile. These results indicate that to obtain a true value of soil total carbon, the entire soil must be sampled, including the coarse soil fraction and soil below 1 m.

Deep Soil Horizons: Contribution and Importance to Soil Carbon Pools and in Assessing Whole-Ecosystem Response to Management and Global Change - Robert B. Harrison; Paul W. Footen; Brian D. Strahm (Forest Science, 2011)
Most of the C in terrestrial ecosystems is found in the soil. Although C calculations indicate that soils are more important than plants as reservoirs of C, soil rarely receives the attention given aboveground ecosystem components when C budgets are calculated. When soil pools are quantified they are typically sampled to relatively shallow depths. Shallow soil sampling in research includes studies that estimate C and nutrient pools and studies assessing the response of terrestrial ecosystems (i.e., forests, grasslands, and agricultural fields) to management treatments. Although many soils have sola that are substantially deeper than 20 cm and C accumulates well below these depths in many soils, the majority of studies of soil C sample to depths of 20 cm or less, generally because of the difficulty and cost of sampling the soil profile deeper. Shallow soil sampling is often justified by assuming that deeper soil horizons are stable and will not change over time, although some medium- and long-term studies do not support this assumption. Shallow soil sampling can result in both a major underestimate of soil C present in the soil profile and an inability to adequately measure the impacts of both treatments for specific goals (i.e., tillage, fertilization, and vegetation management) or other changes (i.e., global change and atmospheric inputs) over time in whole-ecosystem studies. We assessed the potential of shallow soil sampling to underestimate C in the soil profile as well as to change the conclusions of studies of management treatments on soil C. Results showed that where soils were sampled to at least 80 cm or more depth 27-77% of mineral soil C was found >20 cm in depth. In addition, analysis of results for 105 different studies of N fertilization in forests and N fertilization or conversion to switchgrass in agricultural studies shows that deeper sampling can actually change the conclusions of results of some research studies of net C accumulation or loss. Researchers wishing to either quantify soil C pools or measure changes of soil C over time are cautioned to sample soil profiles as deeply as possible and not assume that deeper soil horizons are not a critical part of adequate ecosystem analysis.

Property Value Impacts of Hemlock Woolly Adelgid in Residential Forests - Thomas P. Holmes; Elizabeth A. Murphy; Kathleen P. Bell; Denise D. Royle (Forest Science, 2010)
This study estimates the economic losses attributable to a nonindigenous forest insect, the hemlock woolly adelgid (Adelges tsuga), using cross-sectional and difference-in-difference hedonic price models. The data span a decade of residential property value transactions in West Milford, New Jersey. Hemlock health in naturally regenerated hemlock stands was measured biannually over this period using remote sensing data and the image differencing technique. These data were linked with spatially referenced land use and land cover data, measured twice during the decade, and the locations and housing characteristics associated with parcels sold. Spatial dependence in the regression models was addressed using spatial error and fixed-effects panel data models. The empirical results demonstrated that hemlock decline consistently caused statistically significant reductions in property values both for parcels containing hemlock resources as well as for neighboring nonhemlock parcels. We conclude that failure to account for spatial spillover effects would downwardly bias estimates of economic losses and total economic losses on properties sold during the study period ranged from $0.64 million in the parcel level cross-section model to $2.2 million in the 0.5-km neighborhood difference-in-difference model.

Minimum-Inbreeding Seed Orchard Design - Milan Lstibůrek; Yousry A. El-Kassaby (Forest Science, 2010)
The industrial concept of “quadratic assignment problem” (QAP) was used to develop a new seed orchard design that minimizes the level of inbreeding (minimum inbreeding [MI]) in an orchard's seed crop through the optimum allocation of clones within the orchard's grid. Spatial distribution of individual trees was done in proportion to their degree of genetic relatedness. The MI orchard design accommodates a variable number of unrelated or related clones with equal or variable sizes, and it is not restricted by the orchard's spatial configuration (shape or size). The proposed design is suitable for advanced generation populations that commonly harbor complicated pedigree relationships. The MI design was compared with the commonly used permutated neighborhood design and the completely randomized scheme, resulting in aggregate inbreeding distances of 6.82, 12.53, and 22.56, respectively, highlighting the effectiveness of the proposed design.