Effects Of Throughfall Reduction And Nitrogen Addition On Photosynthetic Physiological And Stoichiometric Characteristics Of Phyllostachys Edulis

Drought caused by global climate change and increased atmospheric nitrogen deposition caused by human activities will directly or indirectly affect the photosynthetic physiological characteristics and stoichiometric characteristics of plants.At present,a large number of researches have focused on the effects of drought and nitrogen deposition on plant photosynthetic physiological characteristics and stoichiometric characteristics,but the response mechanism of photosynthetic physiological characteristics and stoichiometric characteristics to the interaction between drought and nitrogen deposition is still unclear.With good economic benefits and ecological functions,Moso bamboo（Phyllostachys edulis）forest is a representative plantation in subtropical region of China.In addition,drought and atmospheric nitrogen deposition caused by seasonal precipitation pattern in subtropical region of China are increasing.Therefore,studying the response of Moso bamboo photosynthetic physiological characteristics and stoichiometric characteristics to drought and nitrogen deposition can provide scientific basis and theoretical basis for exploring the adaptation mechanism of Moso bamboo to drought and nitrogen deposition,and guiding the protection and management of Moso bamboo forest under the background of global change.Therefore,this study selected the Moso bamboo forest of Changning ecological station in Sichuan province as the research object,and adopted the design of the randomized area experiment with the two-factor interaction of throughfall reduction and nitrogen addition in the forest.Control group was set for CK:(natural precipitation+0 kg N hm^-2·a^-1),throughfall reduction treatment Tr:(50%throughfall reduction+0 kg N hm^-2·a^-1),nitrogen addition treatment N:(natural precipitation+100 kg N hm^-2·a^-1),throughfall reduction+nitrogen addition treatment Tr+N:(50%throughfall reduction+100 kg N hm^-2·a^-1),with 4 Processing and 4 repetitions.Researches were carried out on the stoichiometric characteristics of leaves and branches of Moso bamboo,the photosynthetic physiological characteristics of the leaves（gas exchange parameters,WUE,photosynthesis-photoresponse curve,photosynthesis-CO₂ curve,non-structural carbohydrates and their components of leaves and branches）.The response mechanism of Moso bamboo physiological characteristics and stoichiometric characteristics to throughfall reduction,nitrogen addition and their interactions were also illustrated.The results are as follows:（1）The throughfall reduction treatment only had significant effect on soil water content,which was significantly reduced.Nitrogen addition treatment only had significant effect on soil N content,which was significantly increased.（2）The thoughfall reduction treatment significantly reduced the leave N,P and branch N of Moso bamboo,and significantly increased the C:N of leaves and branches of Moso bamboo,C:P of leaves and N:P of leaves.Nitrogen addition treatment significantly increased the C and N content of leaves and branches,C:P and N:P of branches,but significantly decreased P and C:N of Moso bamboo branches.In addition,with nitrogen addition,the thoughfall reduction significantly reduced the N content of branches and increased the C:N of branches.（3）The throughfall reduction treatment significantly reduced the content of chlorophyll components,P_n,T_r,G_s,LSP,LCP,R_d,CSP,V_cmax and J_max of Moso bamboo,but increased WUE and CCP.Nitrogen addition treatment significantly increased the Chlt,P_n,G_s,T_r,AQY,LSP,R_d and V_cmax of Moso bamboo leaves and significantly reduced CCP.In addition,nitrogen addition improved Chla,AQY and WUE of Moso bamboo under the throughfall reduction treatment.（4）The throughfall reduction treatment significantly increased the content of soluble sugar and NSC of leaves,and significantly reduced the content of starch and NSC of branches.Nitrogen addition significantly increased NSC and its component content of leaves,but decreased NSC and soluble sugar content of branches.Nitrogen addition promoted the conversion of starch of branches under throughfall reduction treatment,and significantly decreased the content of starch and NSC of branches.The main conclusions are:the throughfall reduction limited the absorption of nutrients by leaves and branches of Moso bamboo,affected the synthesis of photosynthetic pigments,and weakened the ability of photosynthesis to use strong light and CO₂.Nitrogen addition enhanced photosynthetic C retention and N absorption capacity,light and CO₂ utilization capacity of Moso bamboo.In addition,nitrogen addition eased the adverse impact of throughfall reduction on photosynthetic physiological characteristics and stoichiometric characteristics,which was also beneficial to promote the bamboo to adopt the strategy of transformation and migration of branch starch to better resist water stress.