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Atmospheric deposition of sulfur and nitrogen species have the potential to acidify terrestrial and aquatic ecosystems, but nitrate and ammonium are also critical nutrients for plant and microbial productivity. Both the ecological response and the hydrochemical response to atmospheric deposition are of interest to regulatory and land management agencies. We developed a non-spatial biogeochemical model to simulate soil and surface water chemistry by linking the daily version of the CENTURY ecosystem model (DayCent) with a low temperature aqueous geochemical model, PHREEQC. The coupled model, DayCent-Chem, simulates the daily dynamics of plant production, soil organic matter, cation exchange, mineral weathering, elution,...
Diatom assemblages in sediments from two subalpine lakes in the Uinta Mountains, Utah, show asynchronous changes that are related to both anthropogenic and natural inputs of dust. These lakes are downwind of sources of atmospheric inputs originating from mining, industrial, urban, agricultural and natural sources that are distributed within tens to hundreds of kilometers west and south of the Uinta Mountains. Sediment cores were retrieved from Marshall and Hidden lakes to determine the impacts of atmospheric pollution, especially metals. Paleolimnological techniques, including elemental analyses and 210Pb and 239+240Pu dating, indicate that both lakes began receiving eolian inputs from anthropogenic sources in the...
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In order to determine the effect of increased nitrogen inputs on fluxed of N2O and CH4 from alpine soils, we measured fluxes of these gases from fertilized and unfertilized soils in wet and dry alpine meadows. In the dry meadow, the addition of nitrogen resulted in a 22-fold increase in N2O emissions, while in the wet meadow, we observed a 45-fold increase in N2O emission rates. CH4 uptake in the dry meadow was reduced 52% by fertilization; however, net CH4 production occurred in all the wet meadow plots and emission rates were not significantly affected by fertilization. Net nitrification rates in the dry meadow were higher in fertilized plots than in non-fertilized plots throughout the growing season; net mineralization...
The sensitivity of high-elevation lakes to acidic deposition was evaluated in five national parks of the Rocky Mountains based on statistical relations between lake acid-neutralizing capacity concentrations and basin characteristics. Acid-neutralizing capacity (ANC) of 151 lakes sampled during synoptic surveys and basin-characteristic information derived from geographic information system (GIS) data sets were used to calibrate the statistical models. The explanatory basin variables that were considered included topographic parameters, bedrock type, and vegetation type. A logistic regression model was developed, and modeling results were cross-validated through lake sampling during fall 2004 at 58 lakes. The model...


    map background search result map search result map Fluxes of nitrous oxide and methane from nitrogen-amended soils in a Colorado alpine ecosystem Fluxes of nitrous oxide and methane from nitrogen-amended soils in a Colorado alpine ecosystem