Nitrogen mineralization across an atmospheric nitrogen deposition gradient in Southern California deserts |
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| Authors: | LE Rao DR Parker A Bytnerowicz EB Allen |
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| Institution: | 1. Laboratory of Ecology and Evolutionary Biology, and Yunnan Key Laboratory of Plant Reproductive Adaption and Evolutionary Ecology, Yunnan University, Kunming 650500, China;2. Jiangxi Key Laboratory for Restoration of Degraded Ecosystems & Watershed Ecohydrology, Nanchang Institute of Technology, Nanchang, Jiangxi 330099, China;3. Key Laboratory of Geospatial Technology for the Middle and Lower Yellow River Regions, College of Environment and Planning, Henan University, Kaifeng 475004, China;4. State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, China;5. Department of Earth, Environmental and Geographic Sciences, University of British Columbia, 3333 University Way, Kelowna, B.C. V1V 1V7, Canada;1. Center for Ecological Research, Northeast Forestry University, Harbin 150040, China;2. School of Geography Sciences, Nanjing Normal University, Nanjing 210023, China;3. Jiangsu Center for Collaborative Innovation in Geographical Information Resource Development and Application, Nanjing 210023, China;4. Department of Plant Ecology (IFZ), Justus–Liebig University Giessen, Heinrich–Buff–Ring 26, 35392 Giessen, Germany;5. School of Biology and Environmental Science, University College Dublin, Ireland |
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| Abstract: | Dry nitrogen deposition is common in arid ecosystems near urban and agricultural centers, yet its impacts on natural environments are relatively understudied. We examined the effects of N deposition on soil N mineralization across a depositional gradient at Joshua Tree National Park. We hypothesized that N deposition affects N mineralization by promoting exotic grass invasion and increasing soil carbon and nitrogen. These relationships were tested through a laboratory incubation on soils collected from sixteen sites where atmospheric N, soil characteristics, and annual vegetation were measured. Mineralization parameters modeled using the Gompertz model were compared to soil C, soil N, estimated soil N from deposition, and percent cover of exotic and native annuals. Calculated soil N from deposition was directly correlated with measured soil C and N and decreasing C:N ratios, which were associated with increased total amounts of mineralized N. However, no effects of soil C or N, and thus N deposition, were observed on mineralization rates. Exotic grasses, but not native forbs or total annual cover, increased with soil C, soil N, and total mineralized N, suggesting that exotic grasses and N deposition are correlated and associated with increasing total C and N in the interspace soils at polluted locations. |
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