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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...
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...
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Dust deposition in the Rocky Mountains may be an important biogeochemical flux from upwind ecosystems. Seasonal (winter/spring) dust mass fluxes to the San Juan Mountains during the period from 2004 to 2008 ranged from 5 to 10 g m?2, with individual deposition events reaching as high as 2 g m?2. Dust deposited in the San Juan Mountains was primarily composed of silt- and clay-sized particles, indicating a regional source area. The concentrations of most major and minor elements in this dust were similar to or less than average upper continental crustal concentrations, whereas trace element concentrations were often enriched. In particular, dust collected from the San Juan Mountain snowpack was characterized by enrichments...
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 order to study the likely effects of global warming on future ecosystems, a method for applying a heating treatment to open-field plant canopies (i.e. a temperature free-air controlled enhancement (T-FACE) system) is needed which will warm vegetation as expected by the future climate. One method which shows promise is infrared heating, but a theory of operation is needed for predicting the performance of infrared heaters. Therefore, a theoretical equation was derived to predict the thermal radiation power required to warm a plant canopy per degree rise in temperature per unit of heated land area. Another equation was derived to predict the thermal radiation efficiency of an incoloy rod infrared heater as a function...
We conducted a study to evaluate the relative importance of topography, grazing, the location of individual plants (microsite), and plant species in controlling the spatial variability of soil organic matter in shortgrass steppe ecosystems. We found that the largest spatial variation occurs in concert with topography and with microsite-scale heterogeneity, with relatively little spatial variability due to grazing or to plant species. Total soil C and N, coarse and fine particulate organic matter C and N, and potentially mineralizable C were significantly affected by topography, with higher levels in toeslope positions than in midslopes or summits. Soils beneath individual plants (Bouteloua gracilis and Opuntia polyacantha)...
Decline of riparian forests has been attributed to hydrologic modifications to river flows. However, little is known about the physiological and structural adjustments of riparian forests subject to modified flow regimes, and the potential for forest restoration using historic flow regimes is poorly understood. In this paired river study, we compared hydrology, water relations, and forest structure in cottonwood-dominated floodplains of the regulated Green River to those of the unregulated Yampa River. We measured floodplain groundwater levels, soil water availability, cottonwood xylem pressure (Ψxp), and leaf-level stomatal conductance (gs) to assess current impacts of river regulation on the water status of adult...
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We asked whether 3?5 kg N y?1 atmospheric N deposition was sufficient to have influenced natural, otherwise undisturbed, terrestrial and aquatic ecosystems of the Colorado Front Range by comparing ecosystem processes and properties east and west of the Continental Divide. The eastern side receives elevated N deposition from urban, agricultural, and industrial sources, compared with 1?2 kg N y?1 on the western side. Foliage of east side old-growth Englemann spruce forests have significantly lower C:N and lignin:N ratios and greater N:Mg and N:P ratios. Soil % N is higher, and C:N ratios lower in the east side stands, and potential net N mineralization rates are greater. Lake NO3 concentrations are significantly higher...
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Global climate change is predicted to alter growing season rainfall patterns, potentially reducing total amounts of growing season precipitation and redistributing rainfall into fewer but larger individual events. Such changes may affect numerous soil, plant, and ecosystem properties in grasslands and ultimately impact their productivity and biological diversity. Rainout shelters are useful tools for experimental manipulations of rainfall patterns, and permanent fixed-location shelters were established in 1997 to conduct the Rainfall Manipulation Plot study in a mesic tallgrass prairie ecosystem in northeastern Kansas. Twelve 9 x 14–m fixed-location rainfall manipulation shelters were constructed to impose factorial...
In ecology textbooks prior to the 1970s, Aldo Leopold's classic story of predator control, over-population of deer, and habitat degradation on the Kaibab Plateau during the 1920s epitomized predator regulation of herbivore populations. However, the story disappeared from texts in the late 20th century after several papers noted uncertainties in estimations of the deer population and provided alternative explanations. We re-examined the case study by determining the age structure of aspen (Populus tremuloides Michx.) on the plateau. Aspen comprises the majority of deer browse in the summer, and the absence of a normal cohort of aspen from the 1920s would indicate deer over-population. The number of aspen (at 1.4...
Identifying distributions of submerged aquatic vegetation (SAV) across the northern Gulf of Mexico (NGOM) coastal landscape necessitates describing ecological processes in estuarine gradients. SAV assemblages are ecological indicators of aquatic ecosystem health; spatial and temporal distributions are strongly correlated to environmental conditions. Many wildlife species, including waterfowl, are dependent on SAV and seeds in NGOM coastal marshes for food and habitat. To understand SAV distributions at multiple spatial and temporal scales a multi-tiered project was designed to collect SAV presence, species assemblage, and cover data, and cores to describe seed food. The first tier sampled inter-annually in the growing...
To investigate the potential response of soils to climatic change, measurements of soil physical and chemical properties were carried out during a year in a mountain zone in Alicante (Spain), along an altitudinal and climatological gradient. Hydrological properties (infiltration runoff and sediment concentration) were measured under winter and summer conditions. Chemical and physical soil properties were analyzed for reference soil profiles along the transect. The erosional response of the soils as well as soil properties like organic matter and CEC are found to be under the direct influence of the climate, and as a result they have to be considered as important factors in the desertification processes.
Elaeagnus angustifolia L., a nonnative N2-fixer, has established within riparian corridors of the interior western United States and is now the fourth most frequently occurring woody riparian plant in this region. We examined whether E. angustifolia alters pools and fluxes of soil inorganic N at eight sites dominated by Populus deltoides ssp. wislizeni along the Rio Grande in New Mexico over 2 years. E. angustifolia contributed a small fraction of total leaf fall (<5% across sites) but accounted for a disproportionately high amount of N (19%) that entered the system from P. deltoides and E. angustifolia leaf fall, due to the high N content (>2%) of E. angustifolia senesced leaves. Soil inorganic N concentrations...
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Fluxes of dissolved organic matter (DOM) are an important vector for the movement of carbon (C) and nutrients both within and between ecosystems. However, although DOM fluxes from throughfall and through litterfall can be large, little is known about the fate of DOM leached from plant canopies, or from the litter layer into the soil horizon. In this study, our objectives were to determine the importance of plant-litter leachate as a vehicle for DOM movement, and to track DOM decomposition [including dissolve organic carbon (DOC) and dissolved organic nitrogen (DON) fractions], as well as DOM chemical and isotopic dynamics, during a long-term laboratory incubation experiment using fresh leaves and litter from several...
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This assessment was conducted to fulfill the requirements of section 712 of the Energy Independence and Security Act (EISA) of 2007 and to improve understanding of carbon and greenhouse gas (GHG) fluxes in ecosystems of the Western United States. The assessment examined carbon storage, carbon fluxes, and other GHG fluxes (methane and nitrous oxide) in all major terrestrial ecosystems (forests, grasslands/shrublands, agricultural lands, and wetlands) and aquatic ecosystems (rivers, streams, lakes, reservoirs, and coastal waters) in two time periods: baseline (generally in the first half of the 2010s) and future (projections from baseline to 2050). The assessment was based on measured and observed data collected by...
Abstract (from http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0143619): Key to understanding the implications of climate and land use change on biodiversity and natural resources is to incorporate the physiographic platform on which changes in ecological systems unfold. Here, we advance a detailed classification and high-resolution map of physiography, built by combining landforms and lithology (soil parent material) at multiple spatial scales. We used only relatively static abiotic variables (i.e., excluded climatic and biotic factors) to prevent confounding current ecological patterns and processes with enduring landscape features, and to make the physiographic classification more interpretable...
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This assessment was conducted to fulfill the requirements of section 712 of the Energy Independence and Security Act of 2007 and to conduct a comprehensive national assessment of storage and flux (flow) of carbon and the fluxes of other greenhouse gases in ecosystems of the Eastern United States. These carbon and greenhouse gas variables were examined for major terrestrial ecosystems (forests, grasslands/shrublands, agricultural lands, and wetlands) and aquatic ecosystems (rivers, streams, lakes, estuaries, and coastal waters) in the Eastern United States in two time periods: baseline (from 2001 through 2005) and future (projections from the end of the baseline through 2050). The Great Lakes were not included in...
A field experiment was established to quantify the effects of different amounts of rainfall on root growth and dry mass of belowground plant parts in three types of grassland ecosystems. Mountain (Nardus grassland), highland (wet Cirsium grassland), and lowland grassland (dry Festuca grassland) ecosystems were studied in 2006 and 2007. Roofs constructed above the canopy of grass stands and gravity irrigation systems simulated three climate scenarios: (1) rainfall reduced by 50%, (2) rainfall enhanced by 50%, and (3) the full natural rainfall of the current growing season. Experimentally reduced amounts of precipitation significantly affected both yearly root increments and total root dry mass in the highland grassland....
Water availability defines and is the most frequent control on processes in arid and semiarid ecosystems. Despite widespread recognition of the importance of water in dry areas, knowledge about key processes in the water balance is surprisingly limited. How water is partitioned between evaporation and transpiration is an area about which ecosystem ecologists have almost no information. We used a daily time step soil water model and 39 years of data to describe the ecohydrology of a shortgrass steppe and investigate how manipulation of soil and vegetation variables influenced the partitioning of water loss between evaporation and transpiration. Our results emphasize the overwhelming importance of two environmental...
Abstract (from http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0102261): The future health of ecosystems is arguably as dependent on urban sprawl as it is on human-caused climatic warming. Urban sprawl strongly impacts the urban ecosystems it creates and the natural and agro-ecosystems that it displaces and fragments. Here, we project urban sprawl changes for the next 50 years for the fast-growing Southeast U.S. Previous studies have focused on modeling population density, but the urban extent is arguably as important as population density per se in terms of its ecological and conservation impacts. We develop simulations using the SLEUTH urban growth model that complement population-driven models...
map background search result map search result map Altering Rainfall Timing and Quantity in a Mesic Grassland Ecosystem: Design and Performance of Rainfall Manipulation Shelters Contemporary geochemical composition and flux of aeolian dust to the San Juan Mountains, Colorado, United States Composition, Dynamics, and Fate of Leached Dissolved Organic Matter in Terrestrial Ecosystems: Results from a Decomposition Experiment Ecosystem Responses to Nitrogen Deposition in the Colorado Front Range Altering Rainfall Timing and Quantity in a Mesic Grassland Ecosystem: Design and Performance of Rainfall Manipulation Shelters Contemporary geochemical composition and flux of aeolian dust to the San Juan Mountains, Colorado, United States Composition, Dynamics, and Fate of Leached Dissolved Organic Matter in Terrestrial Ecosystems: Results from a Decomposition Experiment Ecosystem Responses to Nitrogen Deposition in the Colorado Front Range