目前，有关气候变化下森林根系分泌物输入（尤其是化学组分变化）与土壤生态过程耦合效应的原位研究十分缺乏，严重制约了对根系-土壤-微生物互作机制及其对环境变化响应的深入认识。本项目以亚高山人工云杉林为对象，以根际过程为切入点，以根系分泌物为核心，采用红外辐射增温，结合树皮环割和林下分泌物添加试验，重点研究增温对亚高山森林根系分泌物速率、化学组成及其介导的土壤C-N循环过程的影响，并同步监测土壤微生物特性与矿物-有机物复合体物理化学界面特征变化，旨在：1）刻画气候变暖下森林在生态系统尺度上根系分泌物输入通量、化学成分及其伴随的C:N化学计量特征；2）揭示森林根系分泌物C:N化学计量特征与土壤C-养分循环过程的偶联效应及其对增温的响应；3）厘定微生物与非生物作用过程对根系分泌物诱导的土壤C/N循环激发效应的影响及其相对贡献。本项目实施可提升森林根际生态过程的调控机理及其对环境变化响应的认知水平。

The importance of root-derived labile C inputs on soil processes and functions and their feedbacks to climate change has increasingly been recognized. However, only limited effort has been made to examine the potential mehanisms by which root exudation, especially for root exudation stoichiometry, influence soil ecological processes under global warming through their effects on C-nutrient cycling, which greatly limits our understanding of root-soil-microbe interactions and their potential ecological consequences on forest ecosystem functions. In this study, we employ a suite of novel experimental methods to detremine, quantitatively and qualitatively, slouble root exudates, exudate stoichiometry (C: N), and their biogeochemical consequeces on forest soil C-nutrient cycling under experimental warming in subalpine spruce plantation in the eastern Tibetan Plateau. Meanwhile, we also investigated the physicochemical changes of mineral-organic associations interface, soil microbes and extracellular enzyme activities closely related to these processes in the field. Our goals are to 1) quantify the effects of experimental warming on root exudation fluxes (g C m-2 year-1) at ecosystem scale, chemical composition and C: N stoichiometry in field-grown trees, 2) explore the coupling relationships between exudate stoichiometry and rhizosphere soil C-N cycle under experimental warming, 3) validate and quantify the relative contribution of direct microbial metabolic and indirect abiotic mechanism on rhizosphere priming effects induced by root exudate. Our proposal will greatly advance and deepen the development of rhizosphere ecological processes and associated regulation mechanism in response to changing environmental conditions.