Responses Of Litter Of Main Tree Species In Broad-leaved Korean Pine Forest To Warming And Nitrogen

In recent years,atmospheric nitrogen deposition and global temperature rise have seriously threatened the balance of ecosystem.Forest ecosystem is recognized as the largest ecosystem on land and plays a great role in nitrogen and carbon fixation of forest soil.In particular,litter and its decomposition can provide nutrient and material support,maintain the balance and stability of terrestrial ecosystem,and ensure the normal energy flow and material flow cycle of ecosystem.Although there are a lot of studies on forest litter decomposition at “domestic and abroad” or “local and overseas”,there are few studies on warming,nitrogen deposition and their interaction,and the mechanism of carbon and nitrogen nutrient loss in the decomposition process is not very clear.Therefore,in this experiment,the cross latitude temperature increase was used to simulate the temperature rise in the Xiaoxing'an sample plot in Northeast China and the artificial application of exogenous nitrogen was used to simulate the nitrogen addition treatment.There were four treatments: control,nitrogen application,temperature increase and temperature increase nitrogen application.The effects of Korean pine and Acer truncatum litter on temperature rise,nitrogen increase and temperature and nitrogen increase were studied,so as to provide basis for litter decomposition and reference for nutrient energy cycle in coniferous and broad-leaved mixed forest.The main results in our study were as follows:(1)After two years of decomposition,the mass loss of broad-leaved litter is the most,followed by coniferous leaves and mixed leaves.Nitrogen application treatment increased the mass loss of needle leaf litter,and decreased slowly for broad-leaved and mixed leaves.The mass loss of each litter decreased after heating treatment.It also decreased after increasing temperature and nitrogen treatment.(2)Nitrogen application,temperature and nitrogen treatment changed the release mode of carbon element in mixed leaf litter,and carbon element became enriched first and then released.Increasing temperature and nitrogen changed the release mode of nitrogen and phosphorus in broad-leaved litter,nitrogen changed into leaching enrichment release mode,and phosphorus changed into direct release mode.(3)Under the control treatment,the decomposition differences among different litter types were significantly correlated with the initial nitrogen content of litter,but not after nitrogen application,temperature increase and temperature and nitrogen increase treatment.The decomposition difference between different litter types was significantly correlated with the initial carbon nitrogen ratio of litter,which was significantly correlated under nitrogen application and heating treatment,but not under nitrogen and heating treatment.In conclusion,there are decomposition differences among litter with different leaf types,and the response mechanisms to global change are also different.The response of litter with different leaf types to climate change is positive and negative,and its change law is inconsistent.This study provides data support and scientific reference for how litter decomposition responds to global climate change and affects ecosystem balance and stability.