亚热带森林凋落物分解氮敏感性对干旱的响应及其机理

氮沉降敏感地作用于森林凋落物分解，改变了生态系统的碳平衡过程。但这一过程易受到大尺度上起决定性作用的气候变化的影响，特别像干旱这样的气候事件近几年不断威胁着我国南方森林生态系统，它极有可能会影响凋落物分解对氮的敏感性，进而会改变区域碳平衡过程。但到目前为止，仍然没有相关研究对这一复杂过程的机理进行探索。项目组在前期研究中发现凋落物分解氮敏感性会随干旱程度的加深而发生变化，项目申请也正是基于这一发现，尝试探索该复杂过程的机理。项目主要采用干旱+氮沉降模拟技术，从微生物群落结构、分解酶活性及其基因表达三个方面的内容对不同林型、土壤类型、海拔以及土壤基础含水量等环境条件下的凋落物分解过程进行剖析，以期发现干旱影响凋落物分解氮敏感性的过程机理。这一机理的探索将有助于预测未来干旱增强情况下氮沉降对区域碳释放过程的可能影响，对于地-气碳平衡过程的复杂性以及全球气候变化的研究也具有重要的意义。

Nitrogen deposition sensitively affects litter decomposition of forest, and thus changes carbon balance process of ecosystem. But this process is easily affected by climatic change which plays a decisive role on large scale. Especially, climate event like drought is threatening forest ecosystem of southern China in recent years. Therefore, it also very likely affects nitrogen sensitivity of litter decomposition, and further will change the carbon balance process of region. However, so far, the mechanism on this process has not been still explored by the researches. In previous studies, project group found that nitrogen sensitivity of litter decomposition changed with the strenghtening of drought. Based on this finding,project group try to explore the mechanism of this complicated ecological process. In this project, the litter decomposition processes under the different environmental conditions such as forest type, soil type, elevation and soil basic water content will be analyzed, through the field controlling experiment of simulating drought plus nitrogen deposition, in the way of microbial community structure, decomposition enzyme activity and their gene expression in order to find the mechanism on drought controlling nitrogen sensitivity of litter decomposition.The expoloration of this mechanism will contribute to predict the possible effect of nitrogen deposition on carbon release process of region in the future in the case of drought strengthening, and also be of important significance for the researches on the complexity of land-gas carbon balance process and global climatic change.