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Desert grasslands, which are very sensitive to external drivers like climate change, are areas affected by rapid land degradation processes. In many regions of the world the common form of land degradation involves the rapid encroachment of woody plants into desert grasslands. This process, thought to be irreversible and sustained by biophysical feedbacks of global desertification, results in the heterogeneous distribution of vegetation and soil resources. Most of these shrub-grass transition systems at the desert margins are prone to disturbances such as fires, which affect the interactions between ecological, hydrological, and land surface processes. Here we investigate the effect of prescribed fires on the landscape...
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The cold deserts of the Colorado Plateau contain numerous geologically and geochemically distinct sedimentary bedrock types. In the area near Canyonlands National Park in Southeastern Utah, geochemical variation in geologic substrates is related to the depositional environment with higher concentrations of Fe, Al, P, K, and Mg in sediments deposited in alluvial or marine environments and lower concentrations in bedrock derived from eolian sand dunes. Availability of soil nutrients to vegetation is also controlled by the formation of secondary minerals, particularly for P and Ca availability, which, in some geologic settings, appears closely related to variation of CaCO3 and Ca-phosphates in soils. However, the results...
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Climate change may affect ecosystem functioning through increased temperatures or changes in precipitation patterns. Temperature and water availability are important drivers for ecosystem processes such as photosynthesis, carbon translocation, and organic matter decomposition. These climate changes may affect the supply of carbon and energy to the soil microbial population and subsequently alter decomposition and mineralization, important ecosystem processes in carbon and nutrient cycling. In this study, carried out within the cross-European research project CLIMOOR, the effect of climate change, resulting from imposed manipulations, on carbon dynamics in shrubland ecosystems was examined. We performed a 14C-labeling...
Soils play a key role in the global cycling of carbon (C), storing organic C, and releasing CO2 to the atmosphere. Although a large number of studies have focused on the CO2 flux at the soil–air interface, relatively few studies have examined the rates of CO2 production in individual layers of a soil profile. Deeper soil horizons often have high concentrations of CO2 in the soil air, but the sources of this CO2 and the spatiotemporal dynamics of CO2 production throughout the soil profile are poorly understood. We studied CO2 dynamics in six soil profiles arrayed across a grassland hillslope in coastal southern California. Gas probes were installed in each profile and gas samples were collected weekly or biweekly...
Global demand for energy has increased by more than 50 percent in the last half-century, and a similar increase is projected by 2030. This demand will increasingly be met with alternative and unconventional energy sources. Development of these resources causes disturbances that strongly impact terrestrial and freshwater ecosystems. The Marcellus Shale gas play covers more than 160,934 km(2) in an area that provides drinking water for over 22 million people in several of the largest metropolitan areas in the United States (e.g. New York City, Washington DC, Philadelphia & Pittsburgh). Here we created probability surfaces representing development potential of wind and shale gas for portions of six states in the Central...
Climate change is expected to have different effects in different parts of the world. For this reason, regionally-specific projections of climate and environmental change are important to help those who need to plan how best to adapt. The goal of this project was to use the latest global climate models and state of the science models of vegetation and hydrology, to describe what the latest science says about the Northwest’s future climate, vegetation, and hydrology. Researchers in the project began by evaluating the ability of climate models to simulate observed climate patterns in the Northwest region. The best performing models were ‘downscaled’, that is, remapped onto the finer grids used in models of hydrology...
Early succession aspen and late succession conifer forests have different architecture and physiology affecting hydrologic transfer processes. An evaluation of water pools and fluxes was used to determine differences in the hydrologic dynamics between stands of quaking aspen (Populus tremuloides) and associated stands of mixed conifer consisting of white fir (Abies concolor), Douglas-fir (Pseudotsuga menziesii), and Engelmann spruce (Picea engelmannii). In 2005 and 2006, measurements of snow water accumulation, snow ablation (melt), soil water content, snowpack sublimation, and evapotranspiration (ET) were measured in adjacent aspen and conifer stands. Peak snow water equivalent (SWE) averaged 34–44% higher in...
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We used field studies and imaging spectroscopy to investigate the effect of grazing on vegetation cover in historically grazed and ungrazed high-mesa rangelands of the Grand Staircase?Escalante National Monument, Utah, USA. Airborne hyperspectral remote sensing data coupled with spectral mixture analysis uncovered subtle variations in the key biogeophysical properties of these rangelands: the fractional surface cover of photosynthetic vegetation (PV), nonphotosynthetic vegetation (NPV), and bare soil. The results show that a high-mesa area with long-term grazing management had significantly higher PV (26.3%), lower NPV (54.5%), and lower bare soil (17.2%) cover fractions in comparison to historically ungrazed high-mesa...
We integrated soil models with an established ecosystem process model (SIPNET, simplified photosynthesis and evapotranspiration model) to investigate the influence of soil processes on modelled values of soil CO2 fluxes (RSoil). Model parameters were determined from literature values and a data assimilation routine that used a 7-year record of the net ecosystem exchange of CO2 and environmental variables collected at a high-elevation subalpine forest (the Niwot Ridge AmeriFlux site). These soil models were subsequently evaluated in how they estimated the seasonal contribution of RSoil to total ecosystem respiration (TER) and the seasonal contribution of root respiration (RRoot) to RSoil. Additionally, these soil...
Although field studies have demonstrated an ecosystem-specific effect of experimental atmospheric nitrogen (N) deposition on litter decomposition, a mechanistic understanding of how ligninolytic microbial communities respond to atmospheric deposition is lacking. Because high levels of inorganic N suppress lignin decomposition by some basidiomycetes, it is plausible that the abundance and activity of these key microorganisms underlies differential ecosystem responses of decomposition to atmospheric N deposition. We hypothesize that: (a) atmospheric N deposition will cause an ecosystem-specific reduction in basidiomycete activity and abundance with greatest decreases in ecosystems with lignin-rich forest litter and...
In the projects fostered by the NRP the effects of changed climate (atmospheric CO2 concentration, temperature) on different terrestrial ecosystems were studied. For forests it was concluded that the initial stimulation of tree growth in general did not persist after two years, and therefore care must be taken not to overestimate the potential contribution of increased carbon sequestration by forests. On the other hand, shifted patterns of carbon distribution in the tree-soil system may lead to a higher soil organic matter content, which will contribute to an improved soil structure and availability of soil moisture. A sensitivity analysis revealed that, for the poor sandy forest soils, improved rooting depth is...
The cold deserts of the Colorado Plateau contain numerous geologically and geochemically distinct sedimentary bedrock types. In the area near Canyonlands National Park in Southeastern Utah, geochemical variation in geologic substrates is related to the depositional environment with higher concentrations of Fe, Al, P, K, and Mg in sediments deposited in alluvial or marine environments and lower concentrations in bedrock derived from eolian sand dunes. Availability of soil nutrients to vegetation is also controlled by the formation of secondary minerals, particularly for P and Ca availability, which, in some geologic settings, appears closely related to variation of CaCO3 and Ca-phosphates in soils. However, the results...
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Predicted changes in climate may affect key soil processes such as respiration and net nitrogen (N) mineralization and thus key ecosystem functions such as carbon (C) storage and nutrient availability. To identify the sensitivity of shrubland soils to predicted climate changes, we have carried out experimental manipulations involving ecosystem warming and prolonged summer drought in ericaceous shrublands across a European climate gradient. We used retractable covers to create artificial nighttime warming and prolonged summer drought to 20-m 2 experimental plots. Combining the data from across the environmental gradient with the results from the manipulation experiments provides evidence for strong climate controls...
Abstract (from http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0099604): Across the globe, species distributions are changing in response to climate change and land use change. In parts of the southeastern United States, climate change is expected to result in the poleward range expansion of black mangroves ( Avicennia germinans) at the expense of some salt marsh vegetation. The morphology of A. germinans at its northern range limit is more shrub-like than in tropical climes in part due to the aboveground structural damage and vigorous multi-stem regrowth triggered by extreme winter temperatures. In this study, we developed aboveground allometric equations for freeze-affected black mangroves which...
The article argues that the currently dominant idea of material welfare is at odds with a lifestyle that does justice to basic human values. Measurement of welfare needs to attach importance to a good environment. With regard to the subjective counterpart: social research on the experience of welfare - the quality of life - in various Western countries shows clearly that intangible values are very important in the lives of most people. In a process of globalization of economy and cultural supplies, it will be important to strengthen democratic concern with the environmental question. The legitimation of political authority in (inter)national negotiations will depend on the attention paid to welfare and quality of...
In this study, we investigate changes in ecosystem structure that occur over a gradient of land-degradation in the southwestern USA, where shrubs are encroaching into native grassland. We evaluate a conceptual model which posits that the development of biotic and abiotic structural connectivity is due to ecogeomorphic feedbacks. Three hypotheses are evaluated: 1. Over the shrub-encroachment gradient, the difference in soil properties under each surface-cover type will change non-linearly, becoming increasingly different; 2. There will be a reduction in vegetation cover and an increase in vegetation-patch size that is concurrent with an increase in the spatial heterogeneity of soil properties over the shrub-encroachment...
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Conclusions: Summarizes findings from a review of literature intended to identify critical thresholds for conservation based in empirical studies of landscape fragmentation. Presents a conceptual overview of landscape fragmentation and habitat loss, as well as guidelines and thresholds relating to landscape indicators such as patch size, habitat amount, edge effects, riparian buffers, and habitat connectivity. Thresholds/Learnings: Many. See Kennedy et al. 2003. Synopsis: This report summarizes findings from a review of literature intended to identify critical thresholds for conservation based in empirical studies of landscape fragmentation. In presenting a conceptual overview of landscape fragmentation and habitat...
AbstractContext Conservation planning is increasingly using ‘‘coarse filters’’ based on the idea of conserving ‘‘nature’s stage’’. One such approach is based on ecosystems and the concept of ecological integrity, although myriad ways exist to measure ecological integrity.Objectives To describe our ecosystem-based index of ecological integrity (IEI) and its derivative index of ecological impact (ecoImpact), and illustrate their applications for conservation assessment and planning in the northeastern United States.Methods We characterized the biophysical setting of the landscape at the 30 m cell resolution using a parsimonious suite of settings variables. Based on these settings variables and mapped ecosystems, we...
Many biological, hydrological, and geological processes are interactively linked in ecosystems. These ecological phenomena normally vary within bounded ranges, but rapid, nonlinear changes to markedly different conditions can be triggered by even small differences if threshold values are exceeded. Intrinsic and extrinsic ecological thresholds can lead to effects that cascade among systems, precluding accurate modeling and prediction of system response to climate change. Ten case studies from North America illustrate how changes in climate can lead to rapid, threshold-type responses within ecological communities; the case studies also highlight the role of human activities that alter the rate or direction of system...
The fate of carbon (C) in organisms, food webs, and ecosystems is to a major extent regulated by mass-balance principles and the availability of other key nutrient elements. In relative terms, nutrient limitation implies excess C, yet the fate of this C may be quite different in autotrophs and heterotrophs. For autotrophs nutrient limitation means less fixation of inorganic C or excretion of organic C, while for heterotrophs nutrient limitation means that more of ingested C will ??go to waste?? in the form of egestion or respiration. There is in general a mismatch between autotrophs and decomposers that have flexible but generally high C:element ratios, and consumers that have lower C:element ratios and tighter...


map background search result map search result map Climate Change Affects Carbon Allocation to the Soil in Shrublands Controls of Bedrock Geochemistry on Soil and Plant Nutrients in Southeastern Utah The Response of Soil Processes to Climate Change: Results from Manipulation Studies of Shrublands Across an Environmental Gradient Changes in Vegetation Structure after Long-term Grazing in Pinyon-Juniper Ecosystems: Integrating Imaging Spectroscopy and Field Studies Conservation Thresholds for Land Use Planners Controls of Bedrock Geochemistry on Soil and Plant Nutrients in Southeastern Utah Changes in Vegetation Structure after Long-term Grazing in Pinyon-Juniper Ecosystems: Integrating Imaging Spectroscopy and Field Studies Climate Change Affects Carbon Allocation to the Soil in Shrublands The Response of Soil Processes to Climate Change: Results from Manipulation Studies of Shrublands Across an Environmental Gradient Conservation Thresholds for Land Use Planners