森林土壤有机碳库对于维持和提高林地地力起决定性作用。微生物碳的同化与分解代谢调控土壤有机碳形成与分解。准确表征该生理过程的参数是碳利用效率和周转速率。然而，受方法学限制，我们对微生物周转速率的时空变异规律及其温度敏感性对土壤有机碳矿化的影响程度仍缺乏认识。本项目拟以长白山海拔梯度上的典型温带森林土壤为研究对象，借助13C和18O示踪、13C核磁共振波谱分析、高通量测序、氨基糖及物理分组等技术，原位监测微生物碳利用效率和周转速率的时空格局，解析生物因素与非生物因素交互作用的影响程度及途径；探寻微生物周转与土壤有机碳库转化过程及化学特征的联系；揭示微生物周转温度敏感性对激发效应的调控规律，最终阐明微生物周转对土壤有机碳矿化长期影响的作用机理。结果能够为深入理解森林土壤碳循环的微生物调控机理提供新思路，为森林土壤有机质和林地地力的培育与管理提供理论支持。

Soil organic carbon (SOC) plays a critical role in maintaining and improving soil fertility in forests. The formation and decomposition of SOC are primarily controlled by microbial anabolic and catabolic activities, which could be parameterized as carbon use efficiency (CUE) and biomass turnover rate (Tr). However, owing to the limitation of methodology, the spatiotemporal pattern of CUE and Tr, and the magnitude to which their temperature sensitivity influences SOC mineralization are poorly understood until now. In this study, mineral soils will be sampled in temperate forests along an elevation gradient at Changbai Mountain. We will use a combination of novel isotopic (13C and 18O), spectroscopic (13C-NMR) and molecular techniques with the aims to (1) determine variations in microbial CUE and Tr in situ and the underlying mechanisms; (2) explore the relationships between Tr and the dynamic transfer and chemical characters of SOC pools; and (3) investigate the degrees and sources of priming effects caused by temperature sensitivity of Tr. The overarching goal of our study is to elucidate the underlying mechanisms of how microbial Tr influences the long-term SOC mineralization. Our findings will facilitate to better understand the microbial importance in controlling C cycling of forest soil through a new framework and provide theoretical supports for the cultivation and management of soil organic matter and soil fertility in temperate forests.