Nutrient limitation of alpine plants: Implications from leaf N : P stoichiometry and leaf δ15N |
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Authors: | Xingliang Xu Wolfgang Wanek Caiping Zhou Andreas Richter Minghua Song Guangmin Cao Hua Ouyang Yakov Kuzyakov |
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Institution: | 1. Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, 11A Datun Road, Chaoyang District, 100101 Beijing, China;2. Department of Microbiology and Ecosystem Science, Terrestrial Ecosystem Research, University of Vienna, Althanstrasse 14, A‐1090 Wien, Austria;3. Northwest Institute of Plateau Biology, Chinese Academy of Sciences, NO. 23 Xinning Road, 810008 Xining, China;4. Department of Soil Science of Temperate Ecosystems, University of G?ttingen, 37077 G?ttingen, Germany;5. Department of Agricultural Soil Science, University of G?ttingen, 37077 G?ttingen, Germany |
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Abstract: | Nitrogen (N) deposition can affect grassland ecosystems by altering biomass production, plant species composition and abundance. Therefore, a better understanding of the response of dominant plant species to N input is a prerequisite for accurate prediction of future changes and interactions within plant communities. We evaluated the response of seven dominant plant species on the Tibetan Plateau to N input at two levels: individual species and plant functional group. This was achieved by assessing leaf N : P stoichiometry, leaf δ15N and biomass production for the plant functional groups. Seven dominant plant species—three legumes, two forbs, one grass, one sedge—were analyzed for N, P, and δ15N 2 years after fertilization with one of the three N forms: NO$ _3^- $ , NH$ _4^+ $ , or NH4NO3 at four application rates (0, 7.5, 30, and 150 kg N ha–1 y–1). On the basis of biomass production and leaf N : P ratios, we concluded that grasses were limited by available N or co‐limited by available P. Unlike for grasses, leaf N : P and biomass production were not suitable indicators of N limitation for legumes and forbs in alpine meadows. The poor performance of legumes under high N fertilization was mainly due to strong competition with grasses. The total above‐ground biomass was not increased by N fertilization. However, species composition shifted to more productive grasses. A significant negative correlation between leaf N : P and leaf δ15N indicated that the two forbs Gentiana straminea and Saussurea superba switched from N deficiency to P limitation (e.g., N excess) due to N fertilization. These findings imply that alpine meadows will be more dominated by grasses under increased atmospheric N deposition. |
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Keywords: | ammonium plant functional groups nitrate nitrogen cycling alpine meadow |
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