Treesearch

Due to the hotter droughts occurring with climate change, grasslands of southwestern deserts and southern plains in the United States are predicted to increasingly lose cover of native plant species, be invaded by nonnative species, and have accelerated soil erosion. We evaluated these predictions for desert grasslands in the Paint Gap Hills of Big Bend National Park, Texas. We used data from 10 monitoring transects established in 1981 and surveyed vegetation composition, canopy cover, and soil surface elevations in 1981, 1983, 1995, and 2014. Four longer and hotter droughts occurred...

Background and aims In northern regions, moss and lichen mats are the major carbon-cycling interface between soils and the atmosphere. We aimed to quantify sensitivity of ground layer nutrient stores to environmental predictors, to better understand interactions with vegetation, topography and climatic conditions. Methods With non-destructive forest inventory techniques, we estimated distributions of biomass, carbon and nitrogen among moss/lichen ground layers in a 1.1 million-ha watershed within Alaska’s boreal forest region. Using nonparametric multiplicative regression, we fit response...

Los inventarios forestales nacionales proporcionan datos básicos sobre la biodiversidad, la integridad de los ecosistemas, y la productividad de los recursos naturales en países de todo el mundo. Con mediciones repetidas, estos datos son una base de información muy poderosa para avanzar en nuestro conocimiento de los procesos ecológicos y su respuesta a la gestión forestal y las perturbaciones naturales. Aunque el análisis de datos dispares (“big data”) con nuevas técnicas (por ejemplo, aprendizaje automático) puede ser de utilidad, no hay sustituto para un diseño estadístico riguroso y...

Boreal forests play critical roles in global carbon, water and energy cycles. Recent studies suggest drought is causing a decline in boreal spruce growth, leading to predictions of widespread mortality and a shift in dominant vegetation type in interior Alaska. We took advantage of a large set of tree cores collected from random locations across a vast area of interior Alaska to examine long-term trends in carbon isotope discrimination and growth of black and white spruce. Our results confirm that growth of both species is sensitive to moisture availability, yet show limited evidence of...

Forest inventories require estimates and measures of uncertainty for subpopulations such as management units. These units often times hold a small sample size, so they should be regarded as small areas. When auxiliary information is available, different small area estimation methods have been proposed to obtain reliable estimates for small areas. Unit level empirical best linear unbiased predictors (EBLUP) based on plot or grid unit level models have been studied more thoroughly than area level EBLUPs, where the modelling occurs at the management unit scale. Area level EBLUPs do not...

Climate change over the past several decades has resulted in shifting rainfall pattern and modifying rainfall intensity, which has, in turn, exacerbated stream flow and sediment load and imposed uncertainties to these processes. This study projected impacts of potential future rainfall variations on stream flow and sediment load from the Lower Yazoo River Watershed (LYRW) in Mississippi using the BASINS (Better Assessment Science Integrating Point and Nonpoint Sources)-HSPF (Hydrological Simulation Program-FORTRAN)-CAT (Climate Assessment Tool) modeling system. Several simulation scenarios...

Biomass holds tremendous potential as a renewable feedstock for the production of fuels and chemicals. However, significant technological advancement is required before production of biofuels and bio-based chemicals will become widespread and economically self-sustaining at the industrial scale. Many of the greatest challenges surrounding biomass conversion stem from the complex nature of the feedstock. Biomass consists of the remains of once-living plant tissue, and therefore retains many of the characteristics of the original organism. These characteristics, such as microstructure,...

Since its inception in 1996, the nonprofit Consortium for Research on Renewable Industrial Materials (CORRIM; www.corrim.org) has developed comprehensive environmental performance information on wood building materials consistent with International Organization for Standardization (ISO) standards for life-cycle inventory (LCI) and lifecycle assessment (LCA) research. The majority of prior CORRIM work on structural wood products has been published in two special issues of Wood and Fiber Science (CORRIM 2005, CORRIM 2010) based on data collected and analyzed starting in 1999.

The exposure of wood to elevated temperatures during hot water extraction (HWE) has been shown to significantly influence a variety of physical and chemical properties of the wood. Aspen (Populus tremuloides) and hemlock (Tsuga canadensis)strands underwent HWE at 160° C for four different periods of time. The weight loss (WL) associated with the processes ranged from 2.9 to 17.3% for the aspen, and from 2.9 to 12.8% for the hemlock. The higher WL associated with the hardwood was attributed to higher hemicellulose content in the hardwood than in the softwood as well as differences in...

The aim of this work was to investigate the kinetics of multiple chemicals in acid bisulfite pretreatment and the relationship between total sugar yields and pretreatment factors (temperature and time). The results showed Saeman model accurately fitted the pretreatment process. According to this kinetic model, a maximum hemicellulose hydrolysis yield was achieved at a treatment time of 75 min with a temperature of 145° C. Meantime, the concentrations of acetic acid, hydroxymethylfurfural (HMF), and furfural were 1.54, 0.60, and 1.15 g L-1, respectively. Also, a Lorentzian function...