Rogers P.C.,Western Aspen Alliance |
Rogers P.C.,Ecology Center |
Jones A.,Wild Utah Project |
Catlin J.,Wild Utah Project |
And 3 more authors.
Natural Areas Journal | Year: 2015
Quaking aspen (Populus tremuloides) forests are experiencing numerous impediments across North America. In the West, recent drought, fire suppression, insects, diseases, climate trends, inappropriate management, and ungulate herbivory are impacting these high biodiversity forests. Additionally, ecological tension zones are sometimes created at residential-wildland interfaces with divergent management directives. For example, private conservation reserves bordering public land may be degraded from browsing where game species find refuge from hunting and plentiful forage. We examined putative herbivore impacts to nearly pure aspen forests at Wolf Creek Ranch (WCR), a sparsely developed residential landscape in northern Utah. Forty-three one-hectare monitoring plots were established to measure forest attributes including site characteristics, tree and vegetation condition, and herbivore use. Additionally, we tested the ability of a plot-level visual rating system to characterize objective field measures. Results suggest elk (Cervus elaphus) herbivory is currently having a strong effect on aspen in the study area, reducing many locations to nearly single-layer aspen forests dominated by aging canopy trees. Regeneration (<2 m tall stems) is experiencing moderate to high browse impacts, and recruitment (2-6 m stems) is below replacement levels on approximately half of WCR's aspen forests. The visual rating system accurately reflected significant trends in forest cover, canopy height, plot aspect, regeneration, recruitment, and tree mortality. Ordination of plot and forest data indicated a strong negative relationship between elk presence and recruitment success. We make recommendations for addressing difficult herbivore-aspen interactions where publicly managed wildlife present barriers to conservation within residential forest reserves.
Astani E.,University of Zanjan |
Vahedpour M.,University of Zanjan |
Babaei H.,Ecology center |
Karimipour M.,University of Zanjan
Research Journal of Chemistry and Environment | Year: 2011
Mercury compound concentrations are determined in Anzali wetland. Water sampling from the wetland is collected from four basins stations which are located at inflow and outflow channels in each basin of the wetland in summer, autumn and winter 2009. The highest and the lowest contents of total mercury were observed in the eastern and western basins, respectively. There were statistically significant differences between the contents of total mercury in the wetland water and sampling stations and seasons using a two-way ANOVA-2 technique. The highest total mercury in the wetland water was observed in the autumn.
Mukherjee J.R.,Graduate Program |
Mukherjee J.R.,Ecology Center |
Jones T.A.,U.S. Department of Agriculture |
Adler P.B.,Ecology Center |
Monaco T.A.,U.S. Department of Agriculture
Rangeland Ecology and Management | Year: 2015
Grazing tolerance of dominant native species may determine the fate of rangeland ecosystems, and using native plant populations with good grazing tolerance in restoration seedings may improve ecosystem resilience, especially when domestic herbivores are present. We examined interspecific and intraspecific differences in shoot biomass and defoliation tolerance for two semiarid, perennial cool-season bunchgrasses native to the Intermountain West, USA, Pseudoroegneria spicata and Elymus wawawaiensis, on the basis of four functional traits (specific leaf area [SLA], plant basal area, tiller number, and tiller mass). We applied two treatments, control and boot-defoliation, where the latter included defoliation at the early-reproductive ("boot") stage, the phenological stage most vulnerable to herbivory, while the control treatment did not. We tested two contrasting hypotheses (i.e., that boot-defoliation tolerance is increased through either increases in SLA or through more favorable tiller demography). For shoot biomass, both grasses were less productive under the boot-defoliation treatment than for the control, but E. wawawaiensis displayed higher boot-defoliation tolerance than P. spicata. Interpopulation variation occurred in all four functional traits for P. spicata, but there were no such variation for E. wawawaiensis. The tiller demography hypothesis better explained boot-defoliation tolerance in both species, and neither SLA nor plant basal area was correlated with shoot biomass for either treatment. Of the traits measured, high tiller number served as the primary mechanism for shoot biomass and boot-defoliation tolerance in P. spicata, while tiller number and tiller mass were both important predictors of both shoot biomass and boot-defoliation tolerance. © 2015 Society for Range Management. Published by Elsevier Inc. All rights reserved.
Hooker T.D.,Ecology Center |
Stark J.M.,Ecology Center
Soil Science Society of America Journal | Year: 2012
We used in situ 13C-labeling of an annual grass to examine the decomposition rate and fate of detrital C over 17 mo in a sagebrush ecosystem. We coupled these measurements with 15N pool dilution and tracer measurements to examine seasonal changes in gross N cycling rates in bulk soil and organic matter density fractions. Annual grass fi ne roots decomposed rapidly (0.23 mo-1) over the 17 mo, substantially faster than rates typically reported for other semiarid ecosystems using litterbags. Despite a long summer dry period, recent detrital C was rapidly respired and incorporated into microbial biomass and nonmicrobial fractions between summer and autumn. Decomposition of recent detritus accounted for 13% of mineralized C and 9% of microbial C produced during the summer following plant labeling. These proportions declined by 50% in autumn, indicating that microbes relied more heavily on recent detritus for C and energy during the dry summer than during the following moist autumn months. In spite of this, decomposition rates of recent plant detritus were faster during autumn than summer due to higher rates of microbial activity. Nitrogen immobilization into soil organic matter (SOM) fractions increased from summer to autumn and was fastest in spring. Rates of N immobilization into the supposedly recalcitrant heavy-fraction (HF) SOM were faster than into the light fraction; however, rates in light and heavy fractions were similar when expressed per unit organic C. Rates of N immobilization were positively correlated with the 13C content of density fractions, suggesting that inputs of new plant C were an important driver of N immobilization. While addition of NH4 + stimulated nitrifi cation rates in both summer and autumn, NH 4 + addition only stimulated rates of N immobilization during spring, indicating that heterotrophic microbial growth was N limited during spring but C limited during summer and autumn when plants were not actively growing. Our results indicate that root decomposition in semiarid soils is more rapid than previously thought, and is not likely to be N limited. Moreover, HF SOM is not as recalcitrant as is frequently assumed, but instead, it is a strong sink for recent plant C inputs and a driver of N immobilization in soil. © Soil Science Society of America.
Lindner S.,University of Cambridge |
Peterson S.,Kiel Institute for The World Economy |
Peterson S.,University of Kiel |
Windhorst W.,Ecology Center
Journal of Environmental Planning and Management | Year: 2010
In the not too distant future several power plants throughout Europe will have to be replaced and the decision has to be made whether to build coal-fired power plants with carbon capture and storage (CCS). In a study for the city of Kiel in northern Germany only an 800 MW coal power plant reaches a required minimum for rentability. This study looks at an additional economic and environmental evaluation of a coal plant with CCS. We find that in two out of three carbon and energy price scenarios integrated gasification combined cycle (IGCC) plants with CCS have the greatest rentability. Pulverised coal (PC) plants with CCS can only compete with other options under very favourable assumptions. Life-cycle emissions from CCS are less than 70% of a coal plant - compared with at least more than 80% when only considering direct emissions from plants. However, life-cycle emissions are lower than in any other assessed option. © 2010 University of Newcastle upon Tyne.