bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stabilized Soil Organic Carbon Pools in Subsoils under Forest Are Potential Sinks for Atmospheric CO2
Authors: Lorenz Klaus , Lal Rattan , Shipitalo Martin J. 
Published: April 2024

Abstract
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.
Initial Response of Soil Carbon and Nitrogen to Harvest Intensity and Competing Vegetation Control in Douglas-Fir (Pseudotsuga menziesii) Plantations of the Pacific Northwest
Authors: Slesak Robert A. , Schoenholtz Stephen H. , Harrington Timothy B. , Meehan Nathan A. 
Published: April 2024

Abstract
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 (&gt;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.
The Use of Ground-Penetrating Radar to Accurately Estimate Soil Depth in Rocky Forest Soils
Authors: Sucre Eric B. , Tuttle John W. , Fox Thomas R. 
Published: April 2024

Abstract
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.
Estimating a Multilevel Dominant Height–Age Model from Nested Data with Generalized Errors
Authors: Yang Yuqing , Huang Shongming 
Published: April 2024

Abstract
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.
Improving Tree Age Estimates Derived from Increment Cores: A Case Study of Red Pine
Authors: Fraver Shawn , Bradford John B. , Palik Brian J. 
Published: April 2024

Abstract
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.
Modeling Jack Pine (Pinus banksiana) Foliage Density Distribution
Authors: Schneider Robert , Fortin Mathieu , Berninger Frank , Ung Chhun-Huor , Swift D. Edwin , Zhang S.Y. 
Published: April 2024

Abstract
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.
A Parsimonious Dynamic Stand Model for Interior Spruce in British Columbia
Authors: García Oscar 
Published: April 2024

Abstract
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.
The Effects of Road Quality and Other Factors on Water-Based Recreation Demand in Northern Ontario, Canada
Authors: Hunt Len M. , Dyck Adam 
Published: April 2024

Abstract
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.
Testing for Nonlinear Spatial Integration in Roundwood Markets
Authors: Niquidet Kurt , Manley Bruce 
Published: April 2024

Abstract
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.
Effects of Stand and Inter-Specific Stocking on Maximizing Standing Tree Carbon Stocks in the Eastern United States
Authors: Woodall Christopher W. , D'Amato Anthony W. , Bradford John B. , Finley Andrew O. 
Published: April 2024

Abstract
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.
What Drives Daily Volatility in Lumber Futures Markets?
Authors: Karali Berna 
Published: April 2024

Abstract
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.
Allometric Scaling of Large Branch Volume in Hardwood Trees in Michigan, USA: Implications for Aboveground Forest Carbon Stock Inventories
Authors: MacFarlane David W. 
Published: April 2024

Abstract
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.
Carbon Credit Eligibility under Area Regulation of Harvest Levels in Northern Minnesota
Authors: Gunn John S. , Saah David S. , Fernholz Kathryn , Ganz David J. 
Published: April 2024

Abstract
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.
Late-Successional Biomass Development in Northern Hardwood-Conifer Forests of the Northeastern United States
Authors: Keeton William S. , Whitman Andrew A. , McGee Gregory C. , Goodale Christine L. 
Published: April 2024

Abstract
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 &lt; 0.001) different between mature (195 Mg/ha) and old-growth (266 Mg/ha) sites. Aboveground biomass was positively (P &lt; 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.
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
Authors: Zheng Daolan , Heath Linda S. , Ducey Mark J. , Smith James E. 
Published: April 2024

Abstract
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 &lt; 0.001).