Plant nitrogen uptake strategies tend to plasticity in alpine meadow of Qinghai Tibet Plateau

• 1、State Key Laboratory of Grassland Agro-Ecosystems, School of Life sciences, Lanzhou University, 730000 China

Abstract：Plant nitrogen uptake strategies have preference and plasticity, but it is not clear how soil environmental changes affect preference and plasticity and which strategy plants choose in the process of adapting to soil environmental changes. In this study, we used 15N labeling experiment to explore the plant nitrogen uptake strategies and theirresponse to soil environmental changes under different treatments (CK(control treatment), N(N fertilization), G(grazing)) in the alpine meadow of Qinghai Tibet Plateau. The results showed that compared with CK, N significantly reduced soil total nitrogen (TN) and pH(p< 0.05), and significantly increased soil nitrate nitrogen (NO3-). G significantly reduced TN, pH, NO3- and soil water content (SWC). In CK, the recovery of 15NH4+ by Festuca ovina and plant communities was significantly higher than that of 15N-glycine and 15NO3-, and the recovery of 15NH4+ and 15NO3- by Elymus nutans was similar, and both were significantly higher than that of 15N-glycine. In N, there was no significant difference in the recovery of three forms of nitrogen by Festuca ovina and plant communities, and the recovery of 15NO3- by Elymus nutans was significantly higher than that of 15NH4+ and 15N-glycine. In G, the recovery of 15NH4+ and 15NO3-by Elymus nutans and Festuca ovina were significantly higher than15N-glycine, and the recovery of 15NH4+ by plant communities was significantly higher than 15N-glycine and 15NO3-.Linear correlation analysis showed that the recovery of15NH4+ by plant communities was significantly positively correlated with pH and TN, the recovery of 15NO3- by plant communities was significantly positively correlated with SWC, TN and pH.Recovery ratios of 15NO3-/15NH4+ by plant communities was significantly positively correlated with the soil NO3-/NH4+. VPA showed that the soil NO3-/NH4+and pH were the main factors affecting plant communities to uptake different forms of nitrogen under N fertilization, and pH was the main factor affecting plant communities to uptake different forms of nitrogen under grazing.The above experimental results show that the difference of plant nitrogen uptake strategy is one of the important mechanisms of species coexistence. Plant nitrogen uptake strategy is related to adaptation to soil environment, and plants tend to choose plasticity in the process of adapting to soil environmental changes.

Keywords： 15N Plant nitrogen uptake strategies Soil environment Alpine meadow