Effects of warming conditions on plant Nitrogen-Phosphorus stoichiometry and resorption of three plant species in alpine meadow ecosystems on the Tibetan Plateau

Global climate change is expected to have a significant impact on ecosystems worldwide, especially for alpine meadow ecosystems which are considered as one of the most vulnerable components. However, the effects of global warming on the plant Nitrogen-Phosphorus stoichiometry and resorption in alpine meadow ecosystems remain unclear. Therefore, to investigate the plant Nitrogen-Phosphorus stoichiometry and resorption in alpine meadow ecosystems on the Qinghai-Tibet Plateau, we conducted an artificial warming study using open-top chambers (OTCs) over the 3-years of warming period. We selected three dominant species, four height types of OTCs (0.4 m, 0.6 m, 0.8 m and 1 m) and four warming methods (year-round warming, winter warming, summer-autumn-winter warming and spring-summer-autumn warming in the experiment) in this experiment. In our study, soil temperature significantly increased with increasing the height of OCTs under the different warming methods. Kobresia pygmaea presented an increase in nitrogen (N) limitation and Kobresia humilis presented an increase in phosphorus (P) limitation with increasing temperature, while Potentilla saundersiana was insensitive to temperature changes in terms of nitrogen and phosphorus limitations. Both nitrogen resorption efficiency (NRE):phosphorus resorption efficiency (PRE) and N:P trends in response to rising temperatures were the same direction. The differential responses of chemical stoichiometry of the three species to warming were observed, reflecting that the responses of nitrogen and phosphorus limitations to warming are multifaceted, and the grassland ecosystems may exhibit a certain degree of self-regulatory capability. Our results show that using chemical dosage indicators of a single dominant species to represent the nitrogen and phosphorus limitations of the entire ecosystem is inaccurate, and using N:P to reflect the nutritional limitations might have been somewhat misjudged in the context of global warming.