土壤氮素转化的关键微生物过程及机制

Key processes and microbial mechanisms of soil nitrogen transformation

摘要:

微生物是驱动土壤元素生物地球化学循环的引擎。氮循环是土壤生态系统元素循环的核心之一, 其四个主要过程, 即生物固氮作用、氨化作用、硝化作用、反硝化作用, 均由微生物所驱动。近10年来, 随着免培养的分子生态学技术和高通量测序技术等的发展, 在硝化微生物多样性及其作用机理、厌氧氨氧化过程和机理等研究方面取得了突破性进展。本文重点阐述了我国有关土壤硝化微生物方面的研究进展, 在此基础上, 简要介绍了反硝化微生物和厌氧氨氧化及硝酸盐异化还原成铵作用的研究进展, 并对今后的研究工作提出了展望。今后土壤氮素转化微生物生态学的研究, 应瞄准国际微生生态学发展的前沿, 加强新技术新方法的应用, 结合我国农业可持续发展、资源环境保护和全球变化研究的重大需求, 重点开展以下几方面的工作: (1) 开展大尺度上土壤硝化作用及氨氧化微生物分布的时空演变特征及驱动因子的研究; (2) 加强氮素转化关键微生物过程与机理的研究, 并与相关过程的通量(如氨挥发、N2O释放)和反应速率(如矿化速率、硝化速率)关联起来; (3) 在特定生态系统中系统研究各个氮转化过程的耦合关系, 构建相关氮素转化和氮素平衡模型, 为定向调控土壤氮素转化过程, 提高氮素利用效率并减少其负面效应提供科学依据。

Abstract:

Microorganisms are the engines driving the biogeochemical cycles of soil elements. The nitrogen cycle is one of the central processes of terrestrial ecosystems, and contains four main steps, i.e. nitrogen fixation, ammonification, nitrification, denitrification, all of which are driven by microorganisms. In the last decade, with the rapid development of culture-independent molecular techniques and high-throughput sequencing technologies, breakthrough progress has been made on the diversity and mechanisms of nitrifying microorganisms, and anaerobic ammonia oxidation (anammox) process and mechanisms. Here we review the available knowledge concerning the research progress in ammonia oxidation studies in China, and briefly introduce the researches on denitrifying microorganisms, anammox, and dissimilatory nitrate reduction to ammonium (DNRA), and then present the future perspectives on this research field. Novel techniques and methods will be applied to the future microbial ecology studies of soil nitrogen transformation. It needs to hold the frontiers of microbial ecology, in combination with significant demands for China’s sustainable agriculture, resources and environment protection, and global change research, primarily focusing on the following several areas: (1) to carry on investigations on the large-scale biogeographical patterns of soil nitrification processes and nitrifying microorganisms, and to elucidate the underlying mechanisms of spatial-temporal variations and their driving factors. (2) To explore the key microbe-meditated processes and mechanisms of nitrogen transformation, and link them to the relevant observations on gas flux (e.g. ammonia volatilization, N2O emissions) and reaction rates (e.g. the rates of mineralization and nitrification). (3) To elucidate the coupling between different nitrogen transformation processes in certain ecosystems, and to estimate the nitrogen balance and build models to predict nitrogen transformation and balance. These studies are expected to provide scientific basis for adjustment of nitrogen transformation processes, improvement of nitrogen utilization efficiency and elimination of its negative effects.