稻草还田影响典型水稻土N2O释放的微生物机理

Denitrification in soil is one of the most important processes in earth nitrogen cycle, also is the important mechanism of the soil N2O release. And straw incorporation can directly affect the mineralization-hold balance of nitrogen in soil, so as to increase or reduce soil N2O release. Relied on a long-term experiment, this study would focus on N2O emission, denitrification process and physical/chemical properties in paddy soil, to explore the influence of long-term incorporation of rice straw on denitrification law and N2O release. By incubation experiment, the alternating wet process in rice paddies was simulated; it would go into the response relationship between adding amount of straw and the characteristics of denitrification progress, and then the emission of N2O. Take advantage of molecular biology technology, functional genes would be used for the research on the microbial evolution in denitrificating progress after long-term incorporating of rice straw, and the alteration of microbial community under the condition of different amount of straw incorporation in culture experiment. By this study, it supposed to reveal the inner link of rice straw incorporation and denitrification in paddy soil, clear and definite the drive mechanism of denitrification and N2O release after straw incorporation. The results would be an important theory basis for further research on mutual relationship of carbon and nitrogen and its scientific management.

微生物的反硝化作用是地球氮循环的重要过程，也是土壤N2O释放的重要机制。秸秆还田措施可直接影响土壤氮素的固持-矿化平衡，从而增加或减少土壤N2O的释放。本项目以长期定位试验为依托，研究稻草还田对生长季稻田N2O排放动态和反硝化作用过程土壤理化性质以及关键酶活性的变化，探讨长期稻草还田对稻田反硝化作用规律及其N2O释放的影响；采用室内培养实验，通过模拟稻田干湿交替过程，探讨水稻土反硝化作用特征和N2O释放与不同稻草添加量的响应关系；采用分子生物学技术，利用功能基因研究长期稻草还田条件下反硝化功能微生物演变规律，以及反硝化过程N2O的生成和转化关键功能基因群落组成和丰度与稻草添加量的响应关系，揭示稻草还田与水稻土反硝化作用的内在联系，明确稻草还田影响土壤反硝化作用的微生物驱动机理及其与N2O释放之间的耦合关系，为深入研究水稻土碳氮相互作用关系和农田碳氮管理提供重要的理论依据。

本项目以长期定位试验为依托，研究稻草还田对生长季稻田N2O排放动态和反硝化作用过程土壤理化性质和关键酶的变化，探讨长期稻草还田对稻田反硝化作用规律及其N2O释放的影响；采用室内培养实验，通过模拟稻田干湿交替过程，探讨水稻土反硝化作用特征以及N2O释放与不同稻草添加量的响应关系；采用分子生物学技术，利用功能基因研究长期和短期稻草还田条件下反硝化功能微生物演变规律，以及反硝化过程N2O的生成和转化关键功能基因群落组成和丰度与稻草添加量的响应关系，揭示稻草还田与水稻土反硝化作用的内在联系，明确稻草还田影响土壤反硝化作用的微生物驱动机理及其与N2O释放之间的耦合关系，为深入研究水稻土碳氮相互作用关系和农田碳氮管理提供重要的理论依据。. 研究结果表明，稻草添加促进了红壤水稻土N2O的释放，在土壤理化方面，主要原因有稻草添加后能够增加土壤中可溶性有机碳的供给，为反硝化细菌提供了更多的碳源，同时也增加了土壤中用于反硝化过程的底物-NO3-，从而提高了反硝化强度；从微生物分子生态层面，稻草的添加增加了反硝化过程中产生N2O步骤功能基因的数量，减少了N2O转化为N2功能基因的数量，但这些功能基因的群落组成分布还有待于进一步研究。