祁连山南麓高寒草甸土壤有机碳对氮添加和降水改变的响应OA

Alpine meadows,as one of the dominant vegetation types on the Qinghai-Tibet Plateau,are significantly influenced by atmospheric nitrogen(N)deposition and altered precipitation patterns under global climate change,which profoundly affect carbon balance in these ecosystems.However,the interactive effects of these two factors on soil organic carbon(SOC)dynamics remain highly uncertain.This study,conducted from 2019 to 2021 in an alpine meadow in the northeastern Qinghai-Tibet Plateau,investigated the responses of plant biomass and surface soil(0-10cm)SOC content to N addition(coated urea at 10 g N m-2a-1)and precipitation manipulation(50％increase and 50％decrease),with three replicates per treatment.Results indicated that N addition alone significantly increased peak aboveground biomass(AGB)by 19.1％(83.8g/m2)and the AGB/BGB ratio by 23.3％(0.057).Notably,both AGB and SOC content exhibited significant interannual variations.To mitigate annual variability,relative changes(ΔAGB,ΔBGB,and ΔSOC)between treatments and the control were analyzed,revealing that these relative changes were also insensitive to experimental manipulations.Both Random Forest and Structural Equation Model analyses demonstrated that SOC and ΔSOC contents were primarily regulated by temperature fluctuations rather than plant carbon inputs(AGB,BGB,or their relative changes).This study demonstrated the positive effect of climate change on SOC accumulation in alpine meadows,likely attributable to the dominant role of sustained temperature increases over recent decades,rather than atmospheric N deposition or precipitation regime shifts.The pronounced interannual effects,rather than treatment-specific responses,highlight the urgent need for long-term,multifactorial experiments to unravel the complex responses and mechanisms underlying soil carbon sequestration in alpine meadows under climate change.