西南亚高山季节性冻土区针叶林土壤N转化及其微生物机制对模拟增温的响应

Seasonally frozen soil is the key driver of N cycle in ecosystem of high latitude region. It is reported that climate warming is significant for Qinghai-Tibetan Plateau with typical seasonally frozen soil, and the seasonally frozen will be significantly changed by climate warming. However, it is remained unclear that how are warming and its resulted changes of frozen soil on N transformation. In this project, the soil of the subalpine coniferous forest in eastern Qinghai-Tibetan Plateau is chosen as objects and infrared heaters are used for artificial warming in the situ experiment. We determine the changes of the rate of soil N transformation, soil N pools, the structure and function of microorganisms in different period under different warming treatments (3, 5℃ and ambient). The aims of this project is to: 1) determine the responses of soil N transformation to warming in different period of frozen soil; 2) reveal the effects and potential mechanism of warming on soil N transformation in regions with seasonal frozen soil. These results would provide theoretical basis for comprehensively understanding the mechanism of below-ground ecological process responding to global warming in typical terrestrial ecosystem.

季节性冻土是高海拔地区生态系统N循环的关键驱动因子。青藏高原是典型的季节性冻土区，也是IPCC预测的增温明显区域，气候变暖必将导致该区季节性冻土时空格局产生变化，这将对该区亚高山针叶林土壤N 转化过程产生怎样的影响？基于此，本项目以青藏高原东缘西南亚高山针叶林土壤为研究对象，采用红外辐射加热器模拟气候变暖的原位控制实验，重点研究不同增温幅度（3、5℃）对不同冻土时期土壤N转化速率、N库组成、关键功能微生物群结构及功能的影响。旨在：1）阐明不同冻土时期土壤N转化对模拟增温的响应；2）揭示气候变暖背景下冻土格局变化对土壤N转化过程的影响及微生物机制。以期为全面理解该区森林生态系统地下生态过程对气候变化的响应机制，及森林可持续经营和管理提供重要理论依据。

青藏高原是典型的季节性冻土区，也是IPCC预测的增温明显区域，气候变暖必将导致该区季节性冻土时空格局产生变化，这将对该区亚高山针叶林土壤N 转化过程产生怎样的影响？基于此，本项目以青藏高原东缘西南亚高山针叶林土壤为研究对象，采用红外辐射加热器模拟气候变暖的原位控制实验，重点研究增温对不同冻土时期土壤N转化速率、N库组成、关键功能微生物群结构及功能的影响。结果表明: 增温3.7℃减少了季节性冻土冻融循环次数，增温导致季节性冻土消融增加了土壤N库，尤其是可溶性N库，也改变了土壤N转化关键酶活性；另一方面，培养实验表明冻融循环次数增加了可溶性N库含量也影响了N转化关键酶的活性，结果与野外实验可以相互认证。因此，未来气候变暖背景下川西亚高山针叶林季节性冻土变化会改变土壤N转化过程。