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Abstract
Current understanding of plant nutrient stoichiometry mainly focus on C, N, and P and in humid and tropic regions. This study was conducted to investigate nutrient stoichiometry in a semaird small watershed. Three dominant plants, Medicago sativa, Stipa bungeana, and Artemisia sacrorum, sampled along a natural nutrient gradient, were analyzed with respect to plant nutrient stoichiometry (N:P, N:K, and K:P). The results showed that nutrient stoichiometry varied greatly between plants and within the same plant at the small watershed scale. At the natural nutrient gradient, N:P of the N limited plant is mainly determined by plant N, while that of P or P+N limited plants were dominated by plant P. The N:K and K:P of both N limited and P or N+P limited plants were mainly controlled by plant K with weak relations to nutrient limitations. Aboveground biomass directly influences nutrient stoichiometry, while extractable soil nutrients exert their impacts on stoichiometry through aboveground biomass.
Acknowledgements
The authors thank Professor Göran Ågren from the Department of Ecology, Swedish University of Agricultural Sciences, and reviewers for their comments and suggestions that improved the quality of this paper. This study was supported by the National Natural Science Foundation of China (40901145, 41271315, 40801111), Science and Technology Development Research Program in Shaanxi Province (2011kjxx25), the Program from Northwest A&F University and from the Institute of Soil and Water Conservation, CAS & MWR.