Effects Of Global Change On Physiological Characteristics Of Typical Alpine Meadow Plants In Tibetan Plateau

In recent decades,with the rapid development of human society,global changes characterized by climate warming,precipitation pattern change and atmospheric nitrogen deposition are having a profound impact on terrestrial plants and ecosystems.The effects feed back to global change through the global carbon cycle.Alpine meadows are important carbon sequestration systems around the world.But the special geographical location is sensitive to global change.Based on the warming precipitation platform and nitrogen and phosphorus adding platform of Haibei Station of Northwest Alpine Biology Research Institute of Chinese Academy of Sciences,this paper systematically discusses the warming.The effects of precipitation change and nitrogen and phosphorus addition on photosynthetic physiological characteristics of typical species in Tibetan Plateau,and the database of physiological growth indexes of alpine plants by simulated warming experiments in Qinghai-Tibet Plateau were collected.The effects of different functional types of plants,different ways of warming and different time of warming on the experimental results were studied by using the method of integration analysis(Meta-analysis).The main contents of this study include three parts:the first part discusses the effects of temperature and precipitation on the key photosynthetic physiological parameters of Elymus dahuricus and Gentiana straminea in Tibetan Plateau;In the second part,the effects of nitrogen and phosphorus additionon the photosynthetic physiological parameters of the dominant plant Elymus dahuricus and Gentiana straminea in Tibetan Plateau were discussed,and the third part was the Meta-analysis of simulated warming on photosynthetic physiological capacity of plants in the Tibetan Plateau.The main conclusions are as follows:(1)The net photosynthesis rate of the two plants was significantly increased by precipitation enhancement-warming treatment.The promotion of net photosynthesis achieved by promoting stomatal conductance(Gs)and apparent photosynthetic electron transport rate(ETR).Elymus dahuricus stomatal conductance was sensitive to precipitation change,while Gentiana straminea was sensitive to temperature.Elymus dahuricus possess a higher WUEi;and the value of WUEi increased with the increase of precipitation;and the maximum chemical efficiency of light system ? was decreased with the increase of precipitation;warming increased the value of qP ETR and qN of Gentiana straminea.(2)The promotion of net photosynthesis by increasing precipitation enhancement warming also related to the enzymes of photosynthesis.Warming increased the maximum carboxylation rate(Vcmax)and the maximum electron transport rate(Jmax)for Elymus dahuricus,and the interaction of temperature and precipitation had a significant effect on the Jmax and Vcmax for Gentiana straminea.Under the treatment of precipitation-enhancement warming,the value of Vcmax and Jmax was significantly increased for Gentiana straminea.Increasing temperature and reducing water significantly reduced the Vcmax and Jmax of Gentiana straminea Precipitation increased the dark respiration rate of Gentiana straminea and the effect of temperature on stomatal conductance slope of Gentiana straminea was significant.(3)Warming decreased two alpine species leaf nitrogen content(Nmass);the value of stable isotope ?13C decreased with the increase of precipitation for Elymus dahuricus;warming significantly increased the leaf ?13C values of Gentiana straminea;and the C/N value increased under with warming.The value of C/N decreased with the increase of precipitation.(4)In the nitrogen and phosphorus addition trial,under P treatment,the net photosynthesis rate increased significantly for Elymus dahuricus.The promotion of net photosynthesis by P treatment was mainly by promoting stomatal conductance,maximum photochemical efficiency and apparent photosynthetic electron transport rate(ETR).The results showed that the water use efficiency(WUEi)was significantly higher than that of the control.(5)The promotion of net photosynthesis by P treatment was also related to the enzymes of photosynthesis.under the treatment of P and NP,the maximum carboxylation rate(Vcmax)increased for Elymus dahuricus..The Vcmax of Gentiana stramineaincreased significantly under P and NP treatment,and the Jmax of Gentiana straminea increased significantly under P and NP treatment.The maximum electron transport rate(Jmax)of Gentiana straminea was significantly increased under P treatment.N?NP and NP treatments significantly increased the rate of dark respiration of Gentiana straminea.P and NP treatments significantly increased the stomatal conductance slope of Gentiana straminea.(6)The nitrogen content of leaves increased significantly under N and NP treatment and for Elymus dahuricus;the value of C/N decreased under N and NP treatment.The value of?13C is positively related with the instant water use efficiency for Elymus dahuricus,but Gentiana straminea instead;the value of ?13C and stomatal slope are negatively correlated for Elymus dahuricus,in contrast to the results of Gentiana straminea;the value of ?13C and Vcmax,Jmax positive correlation for Elymus dahuricus in contrast to the results of Gentiana straminea.(7)The main conclusions from meta-analysis are as follows:wanning can increase alpine plants' most the photosynthetic capacity in Tibetan Plateau,but the responses of different functional plants are different;warming methods has no significant impact on photosynthetic capacity of alpine plants;The length of warming time has a significant effect on plant physiological growth in Tibetan Plateau,and some physiological growth traits of different functional plant in Tibetan Plateau have significant difference.