生物炭影响红壤菜地N2O排放的土壤微结构和反硝化微生物耦合机制

N2O is an important agricultural greenhouse gas, intensive vegetable field in red soil region becomes the main source of N2O emission in croplands. Biochar can improve soil permeability, effect microbial habitat, change the relative strength of nitrification and denitrification, decreases soil N2O emissions. This Project take the intensive vegetable-planting red soil as the research object, Using biochar as soil conditioner, Designing the research route of "Biochar→Soil microstructure →Denitrifying microorganism→N2O emissions", to investigate the dynamic changes between soil pore structure and N2O emissions before and after applying biochar. Using 15N isotope tracer technique to explicit biochar influences on denitrification process. Taking modern molecular biotechnology to reveal the problem of how biochar effects on denitrifying microorganism and its influence on N2O emissions. Statistical method will be using to construct the relationship between the characteristics of soil microstructure and denitrification microbial community. Finally the coupling mechanism of soil microstructure and denitrifying microorganism for biochar effects on N2O emissions in red soil vegetable field will be explicited. This project will providing the theoretical basis on establishing the scientific reduction measures of N2O emissions and nitrogen efficient utilization in red soil vegetable field, and also pointing out a new method to mitigate the global climate change.

N2O是重要的农业源温室气体，而集约化红壤菜地则是农田N2O排放的主要来源。生物炭可以改善土壤通透性，影响微生物生境，改变硝化和反硝化作用的相对强弱，减少N2O排放。项目以红壤区集约化菜地土壤为研究对象，采用生物炭作为土壤改良剂，设计“生物炭→土壤微结构→反硝化微生物→N2O排放”研究路线，研究施加生物炭前后土壤孔隙结构特征和N2O排放间的变化关系，明确生物炭通过改善土壤微结构影响N2O排放机理。采用15N同位素示踪技术明确生物炭对红壤菜地反硝化进程的影响，结合现代分子生物学方法研究生物炭影响红壤菜地N2O排放的反硝化微生物机制。通过统计学方法构建土壤微结构特征与反硝化微生物群落特征间的相关关系，阐明生物炭影响红壤菜地N2O排放的土壤微结构和反硝化微生物耦合机制，为科学制定红壤菜地N2O减排措施和实现氮素高效利用提供理论依据，为减缓全球气候变化提供新思路。

N2O是重要的农业源温室气体，红壤菜地土壤施氮量和施肥频次较高，是N2O的主要来源。生物炭可以改善土壤通透性，影响微生物生境，改变硝化和反硝化作用的相对强弱，减少N2O排放。项目以南方红壤区集约化菜地土壤为研究对象，围绕“生物炭→土壤微结构→硝化和反硝化微生物→N2O排放”主线研究生物炭影响红壤菜地N2O排放的土壤微结构和反硝化微生物耦合机制。研究结果表明：生物炭可以显著降低不同质地红壤菜地土壤N2O排放。铵态氮的添加是红壤菜地土壤N2O排放的主要来源，控制南方红壤菜地土壤系统N2O排放的主要策略是降低铵态氮肥的施用。生物炭对土壤微结构的改良机制为生物炭增加<0.25 mm水稳性团聚体含量，增加了不同质地土壤微结构中2-5 mm的孔隙含量和大小。生物炭的添加促进了红壤菜地土壤中硝化作用进程，同时抑制了反硝化作用进程，进而降低红壤菜地土壤N2O的排放。以铵态氮为氮肥来源时氨氧化细菌AOB和亚硝酸还原酶基因（nirs）是控制沙壤土N2O排放的关键基因。以硝态氮为氮肥来源时N2O还原酶基因nosZ是控制沙壤土N2O排放的关键基因，以硝态氮为氮肥来源时生物炭对N2O的减排作用在于生物炭刺激了土壤中的nosZ基因。