Effects Of Nitrogen Addition And UV-B Reduction On The Decomposition Of Elymus Nutans Litter And Microbial Community Characteristics In Alpine Meadow

Decomposition of litters is the key link of material circulation and energy flow in the ecosystem,which is of great significance for maintaining the stability of the ecosystem.Global environmental changes will significantly change the physical,chemical and biological environment of litter,which may affect litter decomposition and nutrient release process.Increased nitrogen deposition and the changes of ultraviolet radiation are currently widespread environmental problems worldwide,and their impact on litter decomposition has received widespread attention,but no unified research results have been obtained,and under the background of global change,both often affect litter decomposition process in the meantime,and the combined effect of the two has not been reported yet.Therefore,in this study,the litter of Elymus nutans,a dominant species in Alpine meadow on the Qinghai-Tibet Plateau,was used as the research object,and the decomposition bag method was used to simulate nitrogen deposition increase(nitrogen deposition in the form of NH₄NO₃ wet deposition,with a sedimentation amount of 5.0 g m^-2 a^-1,which is 4 times the current sedimentation value)and UV-B reduction(radiation intensity is 21%of natural conditions)during a 1.5a(May,2018-October,2019)field in-situ decomposition experiment,to detect the effects of environmental conditions changes on litter mass loss,structural carbon component decomposition and nutrient release,litter bacterial and fungal community,the results showed that:1.Nitrogen addition significantly affected litter mass remaining,but UV-B reduction did not.2.Nitrogen addition significantly decreased remaining of cellulose and hemi-cellulose,but did not affect that of lignin;UV-B reduction did not affect mass remaining of three carbon components.3.Nitrogen addition and UV-B reduction did not significantly affect the release of N and P,but the interaction of nitrogen addition and UV-B reduction with decomposition time affected the release of nitrogen,and the interaction of nitrogen with decomposition time affected the release of P.4.UV-B reduction decreased significantly OTU number of bacteria and fungi community,but N addition did not affect them;N addition and UV-B reduction did not affect?diversity of bacteria and fungi community;UV-B reduction and its interaction with N addition affected significantly?diversity of bacteria and fungi community.The results indicated nitrogen addition promoted litter decomposition of Elymus nutans litter,and UV-B reduction changed significantly the structure of microbial community in litter.Therefore,we consider that global climate change will affect material and nutrient cycling of alpine meadow,and then functioning of alpine meadow ecosystem.