氮添加对高寒草甸表层土壤有机碳及其组分的初期影响OA

To elucidate the initial effects of nitrogen deposition on soil organic carbon(SOC)and its stability in alpine meadows,we conducted a field nitrogen addition experiment in the eastern Qilian Mountains.Aboveg-round biomass,soil physicochemical properties,enzyme activities,and SOC fractions were measured,and their key drivers were identified using variance partitioning.Nitrogen addition significantly increased aboveg-round biomass but reduced cellulase and β-glucosidase activities(P<0.05).Particulate organic carbon(POC)content and proportion decreased markedly,whereas easily oxidizable organic carbon(EOC)and mineral-associated organic carbon(MAOC)increased significantly(P<0.05).POC dynamics were mainly regulated by total phosphorus and carbon-acquiring enzymes,MAOC was closely associated with aboveground biomass,pH,and β-glucosidase,while EOC was primarily driven by available phosphorus and cellulase.Overall,microbial biomass carbon(17%)and dissolved organic carbon(14.1%)primarily explained short-term SOC variations.In summary,nitrogen addition enhanced soil carbon pool stability by promoting plant carbon inputs,modulating enzyme activities,and reshaping the distribution of SOC fractions.These findings reveal the path-ways through which nitrogen deposition stabilizes SOC in alpine meadows,providing critical insights into carbon cycling processes and the carbon sequestration potential of fragile ecosystems under nitrogen enrichment.