旱作覆膜土壤硝化反硝化作用微生物驱动机制研究

Due to good soil moisture conservation and warming effect, the film mulching technology has been widely applied in the rainfed cropland region of North china.The film mulching changes the soil micro environment, and thus influences the soil nitrification and denitrification driven by microorganisms. However, To date, research on structure and function of soil microorganisms related to nitrification and denitrification is still lack of clear understanding , which is the key to reveal the nitrogen transformation under film mulching systerm. In this project, choosing typical film mulching of rainfed cropland, we aimed at analysing the variation characteristics and distribution rule of soil functional microorganisms under different film mulching conditions by using core functional genes in nitrification and denitrification processes as the molecular target. The effect and the possible mechanism of soil functional microorganisms in nitrification and denitrification process and their variable regularity with environmental factors will be further explored, and the dominated environmental factors for soil functional microorganisms will be determined. Through incubation of micro environment with mulching soil DNA 13C labeled stable isotope probing, combined with functional genomics technology, the specific contribution of soil functional microorganisms in key nitrogen transformation under film mulching condition will be assesed and the "active" functional microbial taxa in nitrification and denitrification will also be recognized. This research results will help to reveal the microbial drive mechanism in key soil nitrogen cycling of film mulching in rainfed cropland and understand the characteristics of soil nitrogen transformation. Furthermore, it will also guide the rational application of film mulching and provide scientific basis for increasing nitrogen use efficiency of soil-crop system under film mulching.

地膜覆盖技术具有良好的保墒增温效果，已在我国北方旱区广泛应用。覆膜改变了膜下土壤微环境，从而影响由微生物所驱动的硝化反硝化过程，然而目前有关覆膜农田土壤硝化反硝化功能微生物研究仍缺乏清晰的认识，这是深入揭示覆膜旱作土壤氮转化过程的关键。本项目以典型覆膜旱作农田土壤为研究对象，以硝化和反硝核心功能基因为分子标靶，研究驱动土壤硝化反硝化的功能微生物组成、多样性和结构在不同作物生育期变化特征及分布规律，深入阐释其在参与土壤硝化反硝化的调控机理，明确环境因素变化对土壤硝化反硝化驱动微生物的影响并探明主控环境因子。通过土壤DNA稳定同位素13C标记的微宇宙培养，解析不同功能微生物的相对贡献，识别发挥主导作用的“活跃”硝化反硝化过程微生物驱动者。研究结果将揭示覆膜旱作土壤关键氮转化微生物驱动机制，有利于正确认识土壤氮转化特点，为指导合理应用地膜以及提高地膜覆盖下土壤-作物系统的氮素利用率提供科学依据。

地膜覆盖技术具有良好的保墒增温效果，已在我国北方旱区广泛应用。覆膜改变了膜下土壤微环境，从而影响由微生物所驱动的硝化反硝化过程，然而目前有关覆膜农田土壤硝化反硝化功能微生物研究仍缺乏清晰的认识。本项目以典型覆膜旱作农田土壤（裸地不覆膜、春覆膜和秋覆膜处理）为研究对象，以硝化和反硝核心功能基因为分子标靶，采取野外原位分析与实验室微宇宙模拟实验相结合的方式，研究了驱动土壤硝化反硝化的功能微生物组成、多样性变化特征，结果表明：1）地膜覆盖显著影响土壤水、热状况，从而影响土壤养分的有效性。但是本研究中覆膜处理与不覆膜相比，对土壤有机碳含量影响不显著；而土壤全氮、溶解性有机碳、溶解性有机氮在覆膜处理下，特别是秋覆膜处理含量显著高于不覆膜处理。2）测序结果和α多样性指数表明覆膜处理（特别是秋覆膜）下土壤样品的细菌和真菌多样性显著增加。真菌多样性在表层和亚表层土壤中表现出显著差异，而细菌差异不显著。3）在属的水平上，秋覆膜处理中最丰富的nirk反硝化核心微生物类群是厌氧粘细菌属Anaeromyxobacter、爱德华菌属Edwardsiella、细链孢菌属Catenulispora和酸杆菌属Acidobacterium，而春覆膜处理中，动球菌属Kineococcus明显较高，是核心类群。对于nirS基因，贪铜菌属Cupriavidus在不同处理中表现出显著的差异，且在秋覆膜处理中丰度更高。nirK基因的基因丰度与土壤水分（SMC）、土壤温度（ST）、土壤硝态氮（NO3-N）含量呈显著正相关（p<0.05）；nirS的丰度与土壤有机氮（DON）值呈显著正相关（p<0.05）。通过项目的开展，明确旱作农田土壤硝化反硝化功能微生物对不同覆膜处理的响应规律，明确环境因素变化对土壤硝化反硝化驱动微生物的影响并探明主控环境因子，为最终调节氮素转化过程，提高土壤氮素的可持续利用性提供新的科学依据。