Responses Of Soil Extracellular Enzyme Activities And Carbohydrate Enzyme Genes To Elevation Gradients In Qinling Taibai Mountain

Forest soil carbon pool is the largest carbon pool in terrestrial ecosystems,and its small change have a profoundly influence on atmospheric CO₂concentration and the global carbon balance.Soil extracellular enzymes play a critical role in soil energy and nutrient cycling as an important driver for the decomposition of forest soil carbon pool.However,environmental factors and soil substrates changed by the elevation gradient directly or indirectly regulate the change of soil extracellular enzyme activities.In this study,we selected the forest soil from different elevation in Taibai Mountain as the research object,and measured soil extracellular enzyme activity,soil physical and chemical properties,microbial biomass and other indicators.The research reveals the regulated factors of soil extracellular enzymes and their stoichiometry along the elevation gradient,and explores the strategy of microorganisms adapting to stoichiometric imbalance and nutrient limitation,and clarifies the decomposed mechanism of microbial source carbon by functional microorganisms along the elevation gradient combining the ecological stoichiometry theory and metagenomics technology.Achieve the following conclusions:(1)In the study area(1503-3182 m),?-1,4-glucosidase(BG),?-1,4-xylosidase(BX),cellobiohydrolase(CBH),leucine aminopeptidase(LAP),?-N-acetylglucosaminidase(NAG),acid phosphatase(ACP),polyphenol oxidase(PPO)and peroxidase(PER)increased along the altitude gradient.The enzyme activity is highest at 3182 m above sea level,and the enzyme activity is at low level at low-middle elevations.Soil moisture,soil organic carbon,total nitrogen,total phosphorus,dissolved organic phosphorus,and dissolved organic carbon can respectively explain 61.2%,60.2%,57%,51.3%,39.6%,39.6%of the variation of soil extracellular enzyme activities.(2)Soil microbial communities from 5 elevation gradient are in the homeostasis of C:N and C:P,and have the higher nitrogen use efficiency(NUE)and phosphorus use efficiency(PUE).Soil microorganisms adapt to the stoichiometry imbalance of soil available resources by shifting production and changing element utilization efficiency.(3)The abundance of glycoside hydrolase family(GHs)and auxiliary activity family(AAs)decreased with increasing elevation,and bacterial communities played a major role in the decomposition of microbial source carbon.In addition,soil available substrates(soil organic carbon,total nitrogen,ammonium nitrogen,and nitrate nitrogen)drive the changes in microorganisms decomposing microbial source carbon along the elevation gradient.