冻融作用下秸秆还田后氮转化对农田黑土氮库更新机制的研究

秸秆还田作为全球有机农业的重要环节，对维持农田肥力，减少化肥施用具有重要的意义。东北黑土区地处中高纬度，是受秋末春初季节冻融作用强烈影响的敏感区，但却对冻融作用下秸秆还田后氮的转化及微生物调控机制缺乏深入认识，这严重限制了秸秆还田后黑土地氮素循环和微生物调控机制的评价。本研究以东北黑土区农田黑土为研究对象，采用同位素技术、同位素探针核酸技术（15N-DNA-SIP）及高通量测序技术，系统研究不同冻融交替频率和强度下秸秆还田后氮的转化、微生物调控作用及秸秆的氮向土壤氮库组分更新过程，并结合新转化的氮组分在团聚体中的分布特征，明确冻融作用下秸秆对土壤氮库容量的贡献，最终揭示冻融作用下秸秆还田后氮的转化对农田黑土氮库更新的过程作用机制。本研究可丰富黑土区秸秆高效利用及氮循环过程理论，并为指导黑土区秸秆还田氮肥高效利用技术体系模式提供科学依据。

As an important part of global organic agriculture, straw return is of great significance to maintain farmland fertility and reduce application of fertilizer. The Mollisols area in Northeast China is located in the middle and high latitude, which is a sensitive area strongly affected by freeze-thaw in late autumn and early spring. However, there is a lack of further understanding of nitrogen transformation and the microbial regulation mechanism after straw return under freeze-thaw, which seriously limits the evaluation of nitrogen cycle and the microbial regulation mechanism after straw return. In this study, the arable Mollisols in the northeast Mollisols area were taken as the research object. Isotope tracing, isotope probe nucleic acid technology (15N-DNA-SIP) and high-throughput sequencing were used to systematically study the transformation of nitrogen, the microbial regulation and the renewal process of nitrogen from straw to soil nitrogen pool components after straw return under different freeze-thaw circle frequencies and intensities. Combined with the newly transformed nitrogen components in aggregates, the contribution of straw to the soil nitrogen pool capacity under the action of freeze-thaw will be clarified. Finally, the mechanism of the transformation of nitrogen after straw return under the freeze-thaw cycles will be revealed. This study can enrich the theory of straw efficient utilization and nitrogen cycle process in Mollisols area, and provide scientific basis for guiding the technical system model of straw and improving nitrogen utilization efficiency in Mollisols area.