菜地N2O排放溯源及微生物功能群生态响应机制

Nitrous oxide (N2O) produced from agricultural system is one of the important factors that inducing deterioration of the global greenhouse effect. Vegetable cultivation needs much fertilizer and water while utilization rate is low, which increased N2O emissions, specifically its origin and occurring rule are important basis of developing agricultural emission reduction measures. At present, N2O source partitioning from vegetable soil is not clear, and few studies on the effect of microorganisms driving mechanism in the transformation process. Therefore, the project takes open field Chinese cabbage soil in North China as research object. Firstly, method of stable isotope 15N natural abundance and theory of site preference are used to partition nitrification and denitrification processes and N2O emission behavior, to discuss N2O source affected by inputs of water and fertilizer. Secondly, laboratory incubation will be conducted to simulate N2O main occurring processes, such as autotrophic nitrification, heterotrophic nitrification, etc, to further distinguish between different sources and emissions which affect by fertilizer. Finally, high-throughput sequencing, Illumina Miseq will be used to clarify microbial communities in different N2O sources as well as its response to the changing of environmental conditions. The result will be clear that N2O source partitions affected by different fertilizer-water interactions, and the key role of microbes in nitrogen transformation process, which provides a theoretical basis for making rational agronomic measures and reducing N2O emission.

农业系统产生的氧化亚氮（N2O）是造成全球温室效应持续恶化的重要原因之一。蔬菜种植水肥投入大而肥料利用率低，加剧了其排放，明确其来源和发生规律是制定农业减排措施的重要依据。目前对蔬菜地N2O溯源研究不够深入，且对起驱动作用的微生物在其转化过程中的影响机制研究较少。因此，本项目以华北地区露地白菜土壤为研究对象，首先利用15N稳定同位素自然丰度法和位嗜值理论进行田间N2O硝化、反硝化作用过程及规律研究，探讨不同水肥对其来源的影响；其次，室内实验模拟自养硝化、异养硝化等更多种N2O生成过程，进一步细化区分不同肥力输入对其来源和排放的影响；最后，利用Illumina Miseq高通量测序手段研究功能微生物在N2O各来源中发挥的群体效应和应对环境条件变化的响应机制。研究结果将明确不同水肥互作对N2O生成途径的影响及微生物在氮转化过程中的关键作用，为制定合理农艺措施，减少N2O排放提供理论依据。

农业系统产生的氧化亚氮（N2O）是造成全球温室效应持续恶化的重要原因之一。蔬菜种植水肥投入大而肥料利用率低，更加剧了其排放，明确其来源和发生规律是制定农业减排措施的重要依据。目前对蔬菜地N2O溯源研究不够深入，且对起驱动作用的微生物在其转化过程中的影响机制研究较少。因此，本项目以华北地区露地白菜土壤为研究对象，首先室内实验模拟自养硝化、异养硝化等多种N2O生成过程，以区分不同肥力输入对其来源和排放的影响。发现在一定水分条件下，不同施氮量会引起土壤N2O排放总量及产生途径的差异，其所关联的同位素特征值亦发生相应变化, 从而确立了以稳定同位素自然丰度法和异位体位嗜值(site preference, SP)技术探明土壤N2O发生来源及其在排放总量中的贡献的方法，并确定了田间最合理的施肥水平和灌溉量，为大田研究提供基础；其次利用15N稳定同位素自然丰度法和位嗜值理论进行田间N2O硝化、反硝化作用过程及规律研究，发现在以硫酸铵为氮肥、高土壤含水量 (70% WFPS)条件下，微生物驱动的氨氧化过程是土壤N2O产生的主要来源，施肥量增加会影响N2O来源途径。单独使用δ 15N、δ 18O来区分N2O各种产生途径并不合适，尤其是在施用氨态肥料的农田里；最后，利用Illumina Miseq高通量测序手段研究功能微生物在N2O各来源中发挥的群体效应和应对环境条件变化的响应机制，目前测序结果正在分析中。本研究所进行的测量和分析表明，利用天然同位素丰度法测定蔬菜地土壤中N2O的来源是可行的，有助于设计合理的农业减排措施，可为缓解全球温室效应提供理论依据。