Your search for keyword(s) "ecosystem" resulted in 26 record(s).

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Title: Grazing games: Sharing common property resources with complex dynamics: Journal: Environmental Resource Economics; Authors: A. S. Crepin, and T. Lindahl; Date: 2009; Summary: The gaming theory is used to model outcomes of grassland use for grazing by cooperative farmers and non-cooperating farmers. Models account for grassland dynamics and assume each farmer maximizes profits and use open loop strategies. The two systems analyzed included one in which growth rate depends on amount of grass available (negative feedback) and other in which growth rate remains constant, with no effect dampening grazing pressure. ...; Agrovoc Control Words: Production economics, Economic resources, Grasslands; View more details about this article

Title: A bioeconomic model of cattle stocking on rangeland threatened by invasive plants and nitrogen deposition: Journal: American Journal of Agricultural Economics; Authors: D. Finnoff, A. Strong, and J. Tschirhart; Date: 2008; Summary: The competitive behavior of native grasses and two plant invaders, cheatgrass (Bromus tectorum) and leafy spurge (Euphorbia esula) along with varying levels of nitrogen deposition were examined using the General Equilibrium Ecosystem Model (GEEM), a bioeconomics model. This model was developed to simulate rangelands in the western United States and Canada to illustrate that competition between native grasses and plant invaders along with nitrogen deposition are important factors for determining optimal stocking rates and measuring rangeland health. Th ...; Agrovoc Control Words: Weeds, Rangelands, Stockrate; View more details about this article

Title: Plant traits and ecosystem grazing effects: comparison of U.S. sagebrush steppe and Patagonian steppe: Journal: Ecological Applications; Authors: P. B. Adler, D. G. Milchunas, O. E. Sala, I. C. Burke, and W. K. Lauenroth; Date: 2005; Summary: The effects of grazing on vegetation and soils were examined in two different ecosystems, the sagebrush steppe in the northwestern United States and the Patagonia steppe located in southern Argentina, both sites were located near 45Ëš latitude. In both the U.S. sagebrush steppe and the Patagonia steppe, three study sites were selected for differences in regional precipitation gradients and regional grazing management. All sagebrush steppes were grazed by cattle for beef production while all Patagonian steppes were grazed by sheep for wool. Grazing responses relative to livestock distrib ...; Agrovoc Control Words: Grazing, Rangelands, Sagebrush; View more details about this article

Title: Are boreal ecosystems susceptible to alien plant invasion? Evidence from protected areas: Journal: Oecologia; Authors: M. Rose, and L. Hermanutz; Date: 2004; Summary: A two year study was conducted in Newfoundland on the Gros Morne National Park, a boreal ecosystem, to determine the level of susceptibility to invasion and if any kind of disturbance would cause weed invasion within this large protected area. Plots were located throughout the park with vegetation measurements (% cover by species, bare ground, light availability, and litter cover) and classification of disturbance (human and animal) as high, medium, low or undisturbed taken at each site. Soil characteristics such as pH, and soil substrate were also taken. ...; Agrovoc Control Words: Weeds, Rangelands, Wildlife; View more details about this article

Title: The dynamics of nitrogen movement in an arctic salt marsh in response to goose herbivory: A parameterized model with alternate stable states: Journal: Journal of Ecology; Authors: N. A. Walker, H. A. L. Henry, D. J. Wilson, and R. L. Jefferies; Date: 2003; Summary: Walker et al. constructed a parameterized simulation model to study nitrogen flow in a patch of grazed lawn, within an intertidal marsh ecosystem. The model is based upon two alternative stable states: intertidal lawns, grazed or ungrazed, and exposed sediments, that support little or no vegetation. Values for the state variables obtained from the model were consistent with field data and led the authors to conclude that nitrogen dynamics are crucial in determining salt marsh - goose system stability. Walker et al. suggest that the determining factor is the loss of input of nitrogen from fixa ...; Agrovoc Control Words: Riparian zones, Rangelands, Wildlife; View more details about this article

Title: Effect of defoliation on grass growth. A quantitative review: Journal: Oikos; Authors: D. O. Ferraro, and M. Oesterheld; Date: 2002; Summary: The diversity of responses of individual grasses to defoliation created a controversy years ago, which still needs clarification. Ferraro and Oesterheld quantitatively assessed the evidence of defoliation effects on individual grass growth, addressing two main questions: 1) what is the average and variability of the effect of defoliation on plant growth? and 2) what are the associated conditions accounting for the diversity of effects? They analyzed responses in the literature on defoliation effects using two complementary approaches: linear regressions and meta-analysis. Results showed a ...; Agrovoc Control Words: Riparian zones, Rangelands, Wildlife; View more details about this article

Title: Evaluating the effects of ecosystem management alternatives on elk, mule deer, and white-tailed deer in the interior Columbia River basin, USA: Journal: Forest Ecology and Management; Authors: J. F. Lehmkuhl, J. G. Kie, L. C. Bender, G. Servheen, and H. Nyberg; Date: 2001; Summary: Lehmhuhl et al. developed a Bayesian Belief network to asses the habitat capability for elk, mule deer and white-tailed deer in the Columbia River basin. Their model weighed factors such as disturbance, available forage types and hiding cover to determine if an area would increase in capability or decrease. Overall, the habitat capability for all three ungulates increased in 15 of the 16 regions studied. The main reason for the increase was a drastic rise in the available forage. In contrast, hiding cover for all animals was shown to decrease, but at a lower rate than the increasing forage ...; Agrovoc Control Words: Riparian zones, Rangelands, Wildlife; View more details about this article

Title: Changes induced by elk browsing in the aboveground biomass production and distribution of willow (Salix monticola Bebb): Their relationships with plant water, carbon, and nitrogen dynamics: Journal: Oecologia; Authors: H. R. Peinetti, S. C. Menezes, and M. B. Coughenour; Date: 2001; Summary: Eight long-term exclosures were used to determine the effects of elk (Cervus elaphus) herbivory in winter on Salix monticola in Rocky Mountain National Park, Colorado. Plants in the grazed treatment were in areas open to grazing, but were protected from grazing by small temporary exclosures during the experimental period to prevent additional browsing. Phenological phases, plant biomass (dry weight), gas exchange, soil moisture, and plant nitrogen were measured from May â€“ October for one year. ...; Agrovoc Control Words: Willows , Browsing, Ungulates; View more details about this article

Title: Drought and grazing: I. Effects on quantity of forage produced: Journal: Journal of Range Management; Authors: R. K. Heitschmidt, M. R. Haferkamp, M. G. Karl, and A. L. Hild; Date: 1999; Summary: The effects of grazing during, or during and after, the season of a drought were determined for eastern Montana grasslands in this study. The results suggested that drought greatly reduced standing crop and grazing further reduced standing crop when combined with drought, however, these results did not take initial pasture characteristics into account. Analysis including the initial conditions, determined one year prior to the imposed drought and grazing treatments, revealed that the effects of drought and grazing on forage production were not as extreme as the previous analysis predicted. ...; Agrovoc Control Words: Riparian zones, Rangelands, Wildlife; View more details about this article

Title: Linking above-ground and below-ground interactions: How plant responses to foliar herbivory influence soil organisms: Journal: Soil Biology and Biochemistry; Authors: R. D. Bardgett, D. A. Wardle, and G. W. Yeates; Date: 1998; Summary: In this review, Bardgett et al. identify the mechanisms by which foliar herbivory may indirectly affect the soil biota and associated below-ground processes through affecting plants. The authors demonstrate that the effects of herbivory on soil organisms, through alterations of the quality and quantity of organic matter input, can be extremely important. These effects may be either short-term, simply through the consequence of shifts in non-detrital inputs from root exudates, or longer term, through: (a) alteration of the below-ground biomass and net primary production, (b) of the quality of ...; Agrovoc Control Words: Riparian zones, Rangelands, Wildlife; View more details about this article

Title: Landscape variables affecting livestock impacts on water quality in the humid temperate zone: Journal: Canadian Journal of Plant Science; Authors: E. A. Clark; Date: 1998; Summary: This is a literature review of 46 published scientific articles covering how landscape variables influence the impacts of livestock grazing on water quality in humid temperate zones. ...; Agrovoc Control Words: Riparian zones, Grazing, Watersheds; View more details about this article

Title: Moose herbivory in taiga: Effects on biogeochemistry and vegetation dynamics in primary succession: Journal: Oikos; Authors: K. Kielland, and J. P. Bryant; Date: 1998; Summary: Vegetation and soil chemistry variables were measured inside and outside of a 7 year old exclosure to determine the effects of moose (Alces alces) herbivory on Alaskan taiga forest succession. Vegetation measurements indicated that moose herbivory increased alder (Alnus tenuifolia) and decreased willow (Salix spp.) composition, most likely due to selective browsing pressure on willow species. This shift in species composition effected the understory growth environment and soil chemical properties. Browsed areas had lower soil ca ...; Agrovoc Control Words: Riparian zones, Rangelands, Wildlife; View more details about this article

Title: Livestock grazing: Animal and plant biodiversity of shortgrass steppe and the relationship to ecosystem function: Journal: Oikos; Authors: D. G. Milchunas, W. K. Lauenroth, and I. C. Burke; Date: 1998; Summary: Milchunas et al. synthesized new and previously-published data from long-term grazing treatments in North America shortgrass steppe on diversity and abundance of plants, lagomorphs, rodents, birds, macroarthropods, microathropods and nematodes. Birds appear to be particularly responsive to grazing. Differences among treatments in richness within groups other than plants and birds were relatively minor, especially when compared to large declines in abundance of some groups with increasing grazing intensity. Aboveground macroarthropod and lagomorphs were the most heavily influence by grazing. ...; Agrovoc Control Words: Riparian zones, Rangelands, Wildlife; View more details about this article

Title: Spatial patterns in the moose-forest-soil ecosystem on Isle Royale, Michigan, USA: Journal: Ecological Applications; Authors: J. B. Pastor, B. Dewey, R. Moen, J. Mladenoff, M. White, and J. Cohen; Date: 1998; Summary: Some of the highest moose (Alces alces) densities in the world are on the Isle Royale in Michigan and it is believed that moose browsing has caused a shift from hardwood to conifer dominated forest in this area. The authors tested three geostatistical models of the spatial distribution of available browse, annual browse consumption, conifer basal area, and soil nitrogen across the landscape: (1) random spatial distribution; (2) spherical model; and (3) harmonic oscillator model. The results of this study suggest that as moose use increases, the number of small aspen (< ...; Agrovoc Control Words: Riparian zones, Rangelands, Wildlife; View more details about this article

Title: Herbivores, the functional diversity of plants species, and the cycling of nutrients in ecosystems: Journal: Theoretical Population Biology; Authors: J. Pastor, and Y. Cohen; Date: 1997; Summary: This article explores the effect of herbivores on ecosystem nutrient and energy flow in a boreal regions, given the assumption that plant species differ in herbivore preference, nutrient uptake rates, and decomposition rates. This article also shows that if the consumer selects a plant species based on the chemical factors that simultaneously control both digestion and decomposition, then over a very wide range of consumer return of fecal material, the rates of energy and nutrient flow through the system are less than that of a system where the consumer is absent. Moreover, one of the plants ...; Agrovoc Control Words: Riparian zones, Rangelands, Wildlife; View more details about this article

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