秸秆与生物炭影响东北黑土N2O排放的微生物驱动机制

Protecting and improving the quality of black soil is an active demand to ensure national food security and promote green agricultural development. Straw and biochar have great potential in carbon sequestration, fertilization and improvement of soil structure. N2O is an important greenhouse gases, and its main emission source is farmland soil. The exogenous carbon imput changes the process of soil nitrogen transformation by affecting soil physicochemical and biological properties, consequently, affecting soil N2O emission. Aggregate is the basic unit of soil structure, and the microhabitats created by soil aggregates affect the distribution and activity of soil microbial communities, and thus lead to different carbon and nitrogen transformation processes. Intensive investigation on the coupling effect of straw and biochar retention and soil aggregate distribution on the nitrogen conversion process and functional microbial community structure will improve the understanding of the microbial mechanism of how straw and biochar affecting soil N2O emission. This project focuses on the black soil farmland in northeast China, combines the research of N2O emission characteristics with the N2O generation process and the microbial mechanism. The aim of this project are to clarify the response of nitrification and denitrification process and related functional microbe quantity and community structure characteristics to straw and biochar retention on the aggregate scales, and finally to reveal the microbiological driving mechanisms of N2O emission from black soil affecting by straw and biochar retention. Our study, with important scientific and practical significance, will provide theoretical basis for the managements of regional carbon and nitrogen pool.

保护和提高黑土耕地质量是确保国家粮食安全和促进农业绿色发展的迫切需求。秸秆与生物炭在固碳、培肥、改善土壤结构等方面应用潜力巨大。N2O是重要温室气体之一，农田土壤是其主要排放源。外源有机碳的输入通过影响土壤理化及生物性状改变土壤氮转化过程，进而影响土壤N2O排放。土壤团聚体是土壤结构的基本单元，其创造的微环境深刻影响微生物群落分布与活性，进而导致碳氮转化过程的差异。深入探究秸秆及生物炭还田与土壤团聚体分布对氮转化过程及功能微生物群落结构的耦合作用，有助于完善秸秆与生物炭对土壤N2O排放的影响机制。本项目以东北黑土农田为研究对象，将N2O排放特征、主要产生过程与微生物机理研究相结合，在团聚体尺度阐明土壤硝化反硝化过程及相关功能微生物数量和群落结构特征对秸秆与生物炭的响应机理，最终揭示秸秆与生物炭对黑土N2O排放的影响及其微生物驱动机制，为区域碳氮库管理提供科学依据。

秸秆与生物炭在固碳、培肥、改善土壤结构等方面应用潜力巨大。N2O是重要温室气体之一，农田土壤是其主要排放源。外源有机碳的输入通过影响土壤理化及生物性状改变土壤氮转化过程，进而影响土壤N2O排放。土壤团聚体是土壤结构的基本单元，其创造的微环境深刻影响微生物群落分布与活性，进而导致碳氮转化过程的差异。本研究以东北黑土农田为研究对象，探究了秸秆与生物炭对土壤理化性状、团聚体分布及N2O排放特征的影响，明确了秸秆与生物炭施用下土壤团聚体内氮转化相关酶活性变化规律，并结合对土壤氮转化功能基因绝对丰度以及微生物群落结构与多样性的研究，揭示了秸秆与生物炭影响黑土N2O排放的微生物驱动机制。研究结果表明，秸秆还田（SR）和秸秆生物炭共同还田（BS）能够显著增加土壤中>0.25 mm团聚体比例（R0.25），生物炭（BR）会降低土壤溶解有机质（DOM）腐殖化程度和复杂性，但能够提高土壤活性有机碳含量，而SR则增加DOM腐殖化程度和复杂性。SR、BS处理显著增加农田N2O排放总量，增幅分别为41.7%和63.7%，且N2O排放速率与土壤温度、含水量、矿质氮均呈显著正相关关系。秸秆和生物炭均显著提高了小团聚体中亚硝酸盐还原酶、硝酸盐还原酶和一氧化氮还原酶的活性，但显著降低了氧化亚氮还原酶活性。BS显著增加微团聚体中AOA amoA基因丰度，BR则显著增加了微团聚体中AOB amoA基因丰度。大团聚体和微团聚体中反硝化功能基因nirK的丰度在秸秆还田下显著提高。编码氧化亚氮还原酶的nosZ基因在微团聚体中具有较高的丰度，并且与对照相比，SR显著增加其丰度。微生物群落结构分析表明，BR、SR和BS处理显著降低细菌Shannon指数，BR和BS处理显著降低真菌Shannon指数。施用10和30 t hm-2生物炭可以更好地增强微生物群落间的相互作用，特别是在超大团聚体内。总之，秸秆与生物炭通过提高氮转化关键酶活性，增加硝化反硝化功能基因丰度以及微生物间相互作用，进而促进N2O的排放。本研究可为黑土地保护下的秸秆综合利用提供理论参考。