枯水期提前对洞庭湖湿地土壤微生物功能基因的影响及其生态效应分析

As a result of impounding of the Three Georges Reservoir, climate change and sand mining, the dry season of the lakes (such as, Dongting Lake) of middle and lower reaches of the Yangtze River came early. It will cause the changes of soil microbial functional genes, which are sensitive to environmental change and play a key role in ecological process (such as, matter cycling and degradation of organic pollutants). At present, many studies have been conducted on the early dry season, but have primarily been focused on its law and reason analysis. This project will take the Dongting Lake wetland as an example. It, on the basis of some related studies of our team and using field controlled experiment, will study the changes of the soil microbial functional genes (including carbon, nitrogen, phosphorus and other mater cycling genes, organic pollutants-degrading genes, etc.) with the early dry season (early 0, 20 and 40 days). It will use Geochip technology. It will reveal the responding mechanism of soil microbial functional genes to early dry season in wetland, and will discuss the effect of changes of soil microbial functional genes on the soil mater cycling and degradation of organic pollutants in wetland. This study has some value in the science. It will provide the scientific basis for the management and regulation of the lake wetlands of middle and lower reaches of the Yangtze River under new relationship of river and lake, and will also provide certain theoretical and technical support for the ecological management and protection of other lake wetlands.

受三峡水库蓄水、气候变化、河道采砂等因素的影响，洞庭湖等长江中下游湖泊湿地近些年出现了枯水期明显提前的现象，这将引起对环境变化敏感且在物质循环、有机污染物降解等生态进程中发挥着关键作用的土壤微生物功能基因的变化。目前有很多关于枯水期提前的研究，但主要集中于枯水期提前的规律及原因分析方面。本项目将在相关研究的基础上，以洞庭湖湿地为例，通过野外控制性实验，利用Geochip基因芯片技术，研究枯水期提前0、20、40天条件下湿地土壤微生物功能基因（包括碳、氮、磷等物质循环基因、有机污染物降解基因等）的变化，揭示湿地土壤微生物功能基因对枯水期提前的响应机制，探讨功能基因变化对湿地土壤物质循环及有机污染物降解的影响。该研究具有一定的科学意义，为新江湖关系下长江中下游湖泊湿地的管理和调控提供科学依据，也为其他湖泊湿地的生态管理与保护提供一定的理论与技术支撑。

水文情势是影响湿地生态过程和功能的关键因素。受三峡水库蓄水、气候变化、河道采砂等因素的影响，洞庭湖等长江中下游湖泊湿地近些年出现了枯水期明显提前的现象。本项目通过野外控制性实验，研究了枯水期提前不同时间条件下洞庭湖湿地土壤微生物功能基因的变化：与正常年份相比，枯水期提前40天的土壤微生物功能基因总信号强度（反映丰富度高低）及多样性都显著增加，而枯水期提前20天的土壤微生物功能基因总信号强度及多样性无显著变化，碳循环、氮循环、磷循环、硫循环及有机污染物降解各功能类群的基因总信号强度也都表现出与此相同的变化，检测到的127种碳循环功能基因（至少两个样品中监测到的）中的89种、25种氮循环功能基因中的21种、7种磷循环功能基因中的5种、27种硫循环功能基因中的19种、104种有机污染物降解功能基因中的68种发生了显著变化。揭示了湿地土壤微生物功能基因对枯水期提前的响应机制：各环境因子对土壤微生物功能基因变异的解释量排序为：枯水期提前时间>含水率>TOM>总磷>铵态氮>亚硝态氮>硝态氮，枯水期提前既能通过改变土壤“好氧”/“厌氧”时间直接影响土壤微生物功能基因，也能通过改变土壤有机质含量和含水率等土壤理化性质间接影响土壤微生物功能基因。探讨了功能基因变化对洞庭湖湿地土壤物质循环及有机污染物降解的影响：枯水期提前20天农药相关化合物降解将增强，对碳、氮、磷、硫循环及其他有机污染物降解无显著影响；枯水期提前40天对磷氧化及多环芳烃、萜类的降解无显著影响，其他碳、氮、磷、硫循环及其他有机污染物降解将增强。研究成果将为湿地管理与保护提供科学依据。