Dataset-GCB.xlsx

Abstract: Microbial necromass carbon (MNC) is an important contributor to stable soil organic carbon pools and is regulated by plant root traits and microbial community characteristics. Mean air temperature in the Tibetan Plateau (TP) is predicted to increase between 1.5 and 2.9°C by the end of 21st century, and how the accumulation and persistence of soil MNC will vary under different warming scenarios still poorly understood. We conducted an eight-year field warming experiment, simulating warming at 0 ℃, 0.4 ℃, 1.5 ℃, 2.0 ℃, and 2.5 ℃ above ambient temperatures in a high-altitude alpine meadow ecosystem. We found that low-level warming generally enhanced bacterial necromass carbon (BNC), fungal necromass carbon (FNC), and total MNC compare with high level warming in soil layers between 0-30 cm. Different warming treatments did not significantly affect the ratios of MNC or BNC to soil organic carbon (SOC) across depths. Structural equation modeling analysis demonstrated that the effect of plant root traits on MNC persistence strengthened with warming intensity, while the influence of microbial community characteristics waned as warming increased. Overall, our study provides novel evidence that the major determinants of MNC production and stabilization may vary with warming magnitude in alpine meadows. Differences in potential responses of microbial residue C to warming should be considered in global C-cycling models to more accurately predict future feedbacks between climate and soil C stocks.

摘要：微生物残体碳（microbial necromass carbon, MNC）是稳定土壤有机碳库的重要组成部分，其积累与持久性受植物根系性状及微生物群落特征共同调控。据预测，到21世纪末，青藏高原（Tibetan Plateau, TP）的平均气温将升高1.5至2.9℃，而不同增温情景下土壤微生物残体碳的积累与持久性将如何变化，目前仍不甚明晰。本研究在高海拔高寒草甸生态系统中开展了为期8年的野外增温实验，设置了较环境温度分别升高0℃、0.4℃、1.5℃、2.0℃及2.5℃的5个增温梯度。研究发现，在0-30cm土层中，低强度增温总体上提升了细菌残体碳（bacterial necromass carbon, BNC）、真菌残体碳（fungal necromass carbon, FNC）及总微生物残体碳的含量，而高强度增温则未产生类似促进效果。不同增温处理对各土层中微生物残体碳、细菌残体碳与土壤有机碳（soil organic carbon, SOC）的比值均无显著影响。结构方程模型分析显示，植物根系性状对微生物残体碳持久性的调控作用随增温强度升高而增强，而微生物群落特征的影响则随增温程度加剧而减弱。总体而言，本研究提供了新的实证证据，表明高寒草甸生态系统中微生物残体碳生成与稳定的核心调控因子可能随增温幅度发生变化。全球碳循环模型应纳入微生物残体碳对增温的潜在响应差异，以更精准地预测气候与土壤碳库之间的未来反馈关系。