| Wetland is a unique ecosystem formed by the interaction of land and water,and alpine wetland is more sensitive to climate change（such as nitrogen deposition）due to its vulnerability and sensitivity.Bayinbuluk alpine wetland is a typical alpine wetland in the arid region of Central Asia,which plays an important role in regulating atmospheric composition and element cycle in the region.The rapid increase of global nitrogen deposition rate has a profound impact on the carbon,nitrogen and phosphorus cycles and microbial communities in terrestrial ecosystems.However,the response of soil carbon,nitrogen and phosphorus fractions and microbial communities to nitrogen addition in alpine wetlands in arid regions of Central Asia is not clear,and the mechanism is not clear.Therefore,in the alpine wetland of Bayinbuluk Swan Lake,we selected Swamp（S）,Swamp meadow（SM）and Meadow（M）to set up experiment with nitrogen addition(concentration was CK:0,N1:8,N2:16kg·N·hm-2·a-1).Soil chemical and microbial characteristics were determined by routine laboratory tests and16S/ITS rRNA gene sequencing.The purpose of this study was to explore the effects of short-term（one-year）nitrogen addition on soil carbon,nitrogen and phosphorus fractions and its microbial driving mechanism,in order to provide basic data reference for the formulation of future climate change measures in alpine wetlands around the world.The main conclusions are as follows:（1）There were significant differences in soil carbon,nitrogen and phosphorus fractions and microbial characteristics among different wetland types.Total carbon and total nitrogen were higher in swamp soil,while total phosphorus was higher in swamp meadow soil.The microbial community diversity in swamp soil was abundant,and the structure and function of soil community were significantly different among different wetlands.（2）Nitrogen addition had no significant effect on soil total carbon,nitrogen and phosphorus,total inorganic carbon and total organic phosphorus contents in alpine wetland.However,it significantly increased the contents of inorganic nitrogen（ammonium nitrogen and nitrate nitrogen）,and changed the content of soil carbon fractions in alpine wetland,and increased the stability of soil organic carbon by 18.24%and 25.45%by decreasing the unstable organic carbon fractions and increasing the inert organic carbon fractions of soil,respectively.Nitrogen addition significantly changed the contents of organic nitrogen and inorganic phosphorus,but did not change the nitrogen supply potential,while N2 treatment decreased the phosphorus supply potential of swamp soil by 9.55%,mainly through increasing the contents of occluded phosphate.（3）Nitrogen addition significantly increased soil microbial biomass and soil urease,protease and catalase activities,in which microbial biomass carbon and microbial biomass nitrogen increased by 7.00%-119%and 8.03%-38.26%,respectively.The activities of urease,protease and H2O2 increased by 7.25%-59.63%,4.71%-58.55%and 34.70%-157.27%,respectively.Alkaline phosphatase was not significantly affected.In terms of sucrase activity,N1 treatment increased sucrase activity（increased by 58.58%）,while N2 treatment significantly decreased sucrase activity（decreased by 22.72%）.（4）Nitrogen addition had no significant effect on the OTUs numbers and diversity index of soil microbial community in swamp and swamp meadow,but N1 treatment reduced the OTUs numbers of soil microbial community（decreased by 7.31%）and increased Simpson index（increased by 66.27%）.Nitrogen addition significantly changed the bacterial community structure,metabolic pathways and element cycling related functions of the alpine wetland.（5）The changes of soil carbon,nitrogen and phosphorus were mainly related to the closely related microbial community（microbial community module）,and the highly related Ascomycota and rare microbial community dominated the changes of soil carbon and phosphorus.The microbial network hubs were significantly correlated with soil organic carbon stability index in swamp meadow soil.In conclusion,nitrogen addition did not change the contents of soil total state elements,but significantly changed the contents of soil carbon,nitrogen and phosphorus fractions,and nitrogen addition indirectly regulated the changes of soil carbon,nitrogen and phosphorus fractions through highly related microbial communities in the soil. |
