水文变化对三峡库区消落区土壤反硝化作用的影响及其微生物学机理

The denitrification process in the water level fluctuation zone (WLFZ) has received increasing attention to be studied as a means of permanently nitrogen removal and a source of nitrous oxide. Hydrologic pulsing and vegetation are considered to be the most influential factors determining the denitrification in the WLFZ. In the present project, we will identify the responses of denitrification to the hydrologic pulsing and vegetation types and its microbiological mechanism in the WLFZ of the Three Gorges Reservoir (TGR). Based on our previous works such as the standing vegetation investigation, and the effects of vegetation types and flooding on nitrogen dynamics in the Zhongxian Revegetation area in the WLFZ of the TGR, we will simulate four different hydrologic phases including inundated, saturated, drying and reflooding in situ during the hydrologic pulses, and sample soil and surface water under different hydrological pulsing conditions from different vegetation types. Soil and surface water characteristics, denitrification rates, and dominant species, diversity, and abundance of denitrifying bacterial communities will be analyzed in the laboratory to determine the influences of hydrologic pulsing and vegetation types on the soil denitrification in the Zhongxian Revegetation area in the WLFZ of the TGR. Moreover, we will explore the relationships between denitrification and dominant species, diversity, and abundance of denitrifying bacterial communities to discuss the microbiological mechanism for the effect of hydrologic pulsing and vegetation types on the soil denitrification. This project will yield insight into the mechanism of the effect of hydrologic pulsing and vegetation types on the soil denitrification in the WLFZ and provide basic theory for revegetation and ecological environment construction in the WLFZ of the TGR.

消落区的反硝化作用因既能将氮从土壤生态系统中移除，又是产生温室气体的重要过程而倍受关注，但消落区的水文变化和植被对土壤反硝化作用产生重要影响。本项目在前期已完成的三峡库区水淹前后土壤氮动态变化的分析等工作基础上，针对三峡库区消落区夏季出露时的水文变化的四个阶段（即淹没、饱和、落干和再淹没）开展原位水文变化的模拟，通过土壤和地表水理化性质、土壤反硝化速率测定和反硝化细菌群落结构（优势种群、多样性和丰度）分析，揭示水文变化和植被类型对土壤反硝化作用的影响；通过定量土壤反硝化作用速率与土壤反硝化细菌群落结构间的相关性，探讨消落区水文变化和植被类型对土壤反硝化作用影响的微生物学机理。本研究将加深我们对消落区水文变化和植被对土壤反硝化作用的影响及其微生物学机理的理解，并为三峡库区消落区植被恢复以及库区生态环境建设提供理论基础。

消落区的反硝化作用因既能将氮从土壤生态系统中移除，又是产生温室气体的重要过程而倍受关注，但消落区的水文变化和植被对土壤反硝化作用产生重要影响。本项目在前期已完成的三峡库区水淹前后土壤氮动态变化的分析等工作基础上，针对三峡库区消落区夏季出露时的水文变化的四个阶段（即淹没、饱和、落干和再淹没）开展原位水文变化的模拟，通过对土壤理化性质、土壤反硝化速率测定和反硝化细菌群落结构（优势种群、多样性和丰度）分析，揭示水文变化和植被类型对土壤反硝化作用的影响；通过定量土壤反硝化作用速率与土壤反硝化细菌群落结构间的相关性，探讨消落区水文变化和植被类型对土壤反硝化作用影响的微生物学机理。研究结果表明草本区反硝化细菌群落结构显著不同于乔木区的，这主要是植被因素（物种数和多样性，根碳氮比）和环境因素（土壤温度和pH）共同作用的结果。草本区拥有更多的nirS和nirK基因的拷贝数，这主要和草本区拥有较高的物种数、土壤pH，土壤碳氮比和根碳氮比有关。同时，水文变化显著影响了土壤容重、铵态氮含量，以及土壤反硝化速率，并且土壤铵态氮的含量在饱和状态下最高，落干状态下最低，反硝化速率在淹没状态下最高，落干状态下最低。不同的植被类型下土壤有机碳、pH显著不同，但土壤反硝化速率没有显著性差异。本研究将加深我们对消落区水文变化和植被对土壤反硝化作用的影响及其微生物学机理的理解，并为三峡库区消落区植被恢复以及库区生态环境建设提供理论基础。