Key processes and microbial mechanisms of soil nitrogen transformation

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.