调控典型旱地土团聚体N2O释放的硝化与反硝化微生物协同作用机理

Uplands have been identified as one of the main sources of N2O emissions from agricultural soils in China, accounting for 60~80% of total emissions from farmlands. Soil aggregates are the core structural units of uplands, and possibly the main place of N2O emissions from uplands, but the process mechanisms of N2O emissions from soil aggregates are not clear. In this study, the soil aggregates of typical uplands as the research object, by incubation experiments, we will research the coupling relationships between N2O emissions from different size aggregates and key controlling factors, such as soil water content changes, addition of carbon and nitrogen. By using 15N labeled technique, we will research the response of nitrification and denitrification of different size aggregates to soil water content changes and the contribution of nitrification and denitrification to N2O emissions. By using modern molecular biology techniques, we will further study the coupling relationships between N2O emissions from different size aggregates and the abundance, composition and expression activity of amoA, narG and nosZ of key functional genes of nitrifier and denitrifier, and reveal the synergistic mechanisms of nitrifier and denitrifier in the process of N2O emissions from different size aggregates. Those studies will offer the theoretical basis of controlling greenhouse gas emissions from uplands.

旱地土壤是我国农田重要的N2O排放源，占总排放量的60~80%。土壤团聚体是旱地土壤的核心结构单元，可能是N2O产生与释放的主要场所，然而有关旱地土团聚体N2O产生与释放的过程机理不清。本项目以典型旱地土团聚体为研究对象，通过室内培养试验，研究不同粒级团聚体N2O释放动态与水分变化、外源碳添加量和外源氮添加量等关键调控因子的耦合关系；利用15N底物标记技术研究不同粒级团聚体硝化和反硝化作用对水分变化的响应及对N2O释放的贡献；进一步利用现代微生物分子生物学技术研究不同粒级团聚体N2O释放与关键硝化微生物（含amoA基因）和反硝化微生物（含narG和nosZ基因）种群的数量、组成和表达活性的耦合关系，揭示不同粒级团聚体N2O释放过程中硝化与反硝化微生物的协同作用机理，为调控旱地土壤温室气体排放提供重要科学依据。

本项目以典型旱地土团聚体为研究对象，通过室内培养试验，研究不同粒级团聚体N2O释放过程中硝化与反硝化微生物的协同作用机理。结果表明，水分条件和土地利用类型均显著影响旱地土团聚体N2O的释放。不同粒径团聚体的N2O释放速率与粒径呈显著负相关。 35%水分条件下团聚体N2O释放速率显著高于25%水分条件，但水分条件不会改变N2O释放速率与粒径呈负相关的关系。表明在 25%和 35%水分条件下小团聚体均是土壤N2O释放的活跃微域。25%水分条件下，硝化和反硝化作用是团聚体N2O产生的主要途径；35%水分条件下，反硝化作用是团聚体N2O产生的主要途径。25% 水分条件下不同粒径团聚体N2O释放速率与narG、nosZ、AOA、AOB丰度呈极显著正相关，而35%水分条件下只与narG和nosZ丰度存在显著正相关性，表明硝化微生物和反硝化微生物丰度在低水分条件下可能是造成不同粒径N2O释放速率差异的重要原因，而高水分条件下该差异则主要与反硝化微生物丰度差异相关。不同粒径团聚体中，分别含nosZ、narG和AOB 微生物群落结构存在一定差异但并不显著，而AOA群落组成在不同粒径团聚体中存在显著差异。因此，含nosZ、narG和Bact-amoA微生物的群落组成可能是导致不同粒径团聚体N2O释放差异的原因，但仍有待进一步测序分析。