Short-term effect of increasing nitrogen deposition on CO2, CH4 and N2O fluxes in an alpine meadow on the Qinghai-Tibetan Plateau,China |
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| Authors: | Chunming Jiang Guirui Yu Huajun Fang Guangmin Cao Yingnian Li |
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| Institution: | 1. College of Global Change and Earth System Science, Beijing Normal University, Beijing 100875, China;2. Joint Center for Global Change and China Green Development, Beijing Normal University, Beijing 100875, China;3. School of Atmospheric Sciences, Sun Yat-Sen University, Guangzhou 519082, Guangdong, China;4. State Key Laboratory of Cryospheric Sciences, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou, Gansu 730000, China;5. State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China;6. University of the Chinese Academy of Sciences, Beijing 100049, China;7. Department of Grassland Science, China Agricultural University, Beijing 100193, China;8. College of Social Science, Department of Geography, Michigan State University, East Lansing, MI 48824, United States;1. Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China;2. Department of Biological Sciences, Center for Ecosystem Sciences and Society, Northern Arizona University, Flagstaff, AZ 86001, USA;3. College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China;4. Research Center of Forest Management Engineering of State Forestry and Grassland Administration, Beijing Forestry University, Beijing 100083, China |
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| Abstract: | An increasing nitrogen deposition experiment (2 g N m?2 year?1) was initiated in an alpine meadow on the Qinghai-Tibetan Plateau in May 2007. The greenhouse gases (GHGs), including CO2, CH4 and N2O, was observed in the growing season (from May to September) of 2008 using static chamber and gas chromatography techniques. The CO2 emission and CH4 uptake rate showed a seasonal fluctuation, reaching the maximum in the middle of July. We found soil temperature and water-filled pore space (WFPS) were the dominant factors that controlled seasonal variation of CO2 and CH4 respectively and lacks of correlation between N2O fluxes and environmental variables. The temperature sensitivity (Q10) of CO2 emission and CH4 uptake were relatively higher (3.79 for CO2, 3.29 for CH4) than that of warmer region ecosystems, indicating the increase of temperature in the future will exert great impacts on CO2 emission and CH4 uptake in the alpine meadow. In the entire growing season, nitrogen deposition tended to increase N2O emission, to reduce CH4 uptake and to decrease CO2 emission, and the differences caused by nitrogen deposition were all not significant (p < 0.05). However, we still found significant difference (p < 0.05) between the control and nitrogen deposition treatment at some observation dates for CH4 rather than for CO2 and N2O, implying CH4 is most susceptible in response to increased nitrogen availability among the three greenhouse gases. In addition, we found short-term nitrogen deposition treatment had very limited impacts on net global warming potential (GWP) of the three GHGs together in term of CO2-equivalents. Overall, the research suggests that longer study periods are needed to verify the cumulative effects of increasing nitrogen deposition on GHG fluxes in the alpine meadow. |
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