稻田常用农药对三江平原湿地土壤微生物群落结构、功能的影响及其降解研究

The Sanjiang Plain is the important rice production base in China. Wetland reclamation and the construction of the irrigation and water conservancy project resulted in the dramatical decrease of wetland area and the deterioration of ecological environment in the Sanjiang Plain. Pesticides were widely used during the rice cultivation. They can protect rice production, but in the mean while, they also become important pollutants of soil ecosystem. The effect of pesticides on wetland ecosysterm and their degradation is a realistic problem in front of us demanding studying and solving urgently. In this study, tricyclazole and quinclorac will be applied to natural wetland and artificial wetland (paddy field) in the Sanjiang Plain. Based on in-situ and laboratory experiment results, the changes in the structure and function (especially C conversion) of soil microbial community will be monitored. The objectives of this study are to understand how nature and artificial wetland soil microbial communities response to tricyclazole and quinclorac and to identify the taxonomic and functional imformation of the microorganisms which are able to degrade tricyclazole and quinclorac and the degradation pathway under unflooded aerobic and flooded anaerobic conditions, as well as the main factors that influence the degradation. This study will help us to understand the influence of typical pesticides on wetland soil microbial structure and function in the Sanjiang Plain and their underlying degradation mechanism, evaluate the effects of pesticides on wetland soil environment ecological security, and provide guidance on safe and rational use of pesticides.

三江平原是我国重要的稻米生产基地，湿地垦殖以及农田水利工程的兴建，导致了三江平原沼泽湿地面积急剧减少和生态环境恶化。农药作为水稻种植过程中重要的生产资料，在保障水稻产量的同时，是否会对三江平原湿地生态系统产生影响及其降解特性成为了亟待研究的课题。本项目以三江平原天然湿地和人工湿地（稻田）为供试对象，采用原位培养及室内试验相结合的研究手段，配合高通量测序等分析方法，研究添加三环唑和二氯喹啉酸后自然湿地和人工湿地（稻田）土壤微生物群落结构和功能，特别是碳转化功能的变化特征，并利用同位素标记技术，探讨三环唑和二氯喹啉酸在非淹水好氧及淹水厌氧情况下的微生物降解及影响因素，揭示参与降解的微生物种群和功能信息。本研究在理论上有助于深入理解典型农药对三江平原湿地土壤微生物结构和功能的影响及其降解途径，为安全、合理使用农药，评估农药对湿地土壤环境生态安全的影响提供科学依据。

三环唑和二氯喹啉酸在水稻种植过程中被广泛施用，在保障水稻产量的同时，也成为了湿地土壤生态系统的重要污染物。本项目采用原位培养及室内试验相结合的研究手段，配合高通量测序等分析方法，研究添加三环唑和二氯喹啉酸后自然湿地和人工湿地（稻田）土壤微生物群落结构和功能，特别是碳转化功能的变化特征，并研究三环唑和二氯喹啉酸的微生物降解机理。得到如下研究结果：（1）三环唑和二氯喹啉酸混合施用会影响湿地土壤微生物的群落结构，但并不影响多样性。（2）对于稻田土壤微生物，三环唑施用对主导菌门、群落结构以及标志差异物种造成的影响较大，二氯喹啉酸施用对微生物功能影响较大，混合施用主要影响Alpha多样性。在碳循环相关的功能方面，施用三环唑在短期内增加厌氧碳固定相关基因丰度，混合施用显著提高有氧碳固定和一氧化碳氧化相关基因丰度。（3）从常年施用三环唑和二氯喹啉酸的水稻土中筛选出降解功能菌，明确温度、pH和污染物浓度会显著影响降解效率，并检测到二氯喹啉酸和三环唑的降解产物，通过全基因组测序推测出参与降解反应的相关酶信息及降解途径。本研究在有助于深入理解典型农药对湿地土壤微生物结构和功能的影响及其降解途径，为三环唑和二氯喹啉酸的生物修复技术发展提供理论支撑。