亚热带典型水稻土中秸秆降解的微生物代谢网络及其驱动机制

Straw is the most important organic resource in paddy field ecosystem, but currently the straw returning ratio in China is at a very low level. An appropriate utilization of straw would be beneficial for the agricultural management. The decomposition of straws in soils is driven by various microorganisms, the mechanism of which is not yet known. At the same time, it is also greatly affected by many environmental factors, further complicating this transformation process to be spatial dependent. In this proposed project, we will use field experimental stations under hydrothermal gradients as research platforms via a series of modern molecular experiments such as isotope labeling and high through-put sequencing, to investigate the spatial variations in straw decomposition and organic composition of paddy field. This investigation will allow us to clarify the changes in microbial communities and metabolic activities during the straw decomposition processes, and to elucidate the hierarchy relationship between them. We will identify the key microbial taxa and the relative contribution of different groups to the straw decomposition. We will also draw the microbial metabolic network through analyzing the composition of metabolites and metabolic pathways. All together, the objective of this project is to clarify the microbial mechanisms of straw decomposition in paddy soils in subtropics of China, and to provide a scientific basis for re-sourcialized management of agricultural wastes.

秸秆是我国稻田最重要的有机资源，但目前直接还田率较低，秸秆的合理利用是我国农田管理亟待解决的重大现实问题。土壤中秸秆降解由微生物所驱动，受多种环境因子影响，导致不同土壤中秸秆降解的物质转化过程十分复杂，空间变异性显著，且其微生物作用机制尚不清楚。本项目依托我国亚热带代表性区域已经建立的多个野外长期试验站，通过布置田间定位试验进行联网观测，结合同位素示踪和高通量测序等现代生物分析手段，研究主要类型水稻土中秸秆降解过程和有机质组成的区域分异规律，探明秸秆降解过程中微生物群落特征和代谢活性变化，确定两者之间的对应关系；明确水稻土秸秆降解过程的主导微生物类群，阐释不同微生物类群对秸秆降解的相对贡献；通过解析水稻土中秸秆降解过程的代谢产物组成和代谢途径，描绘水稻土秸秆降解的微生物代谢网络。研究结果将阐明亚热带水稻土中秸秆降解过程的微生物学驱动机制，并为我国农业有机废弃物资源化管理利用提供科学依据。

秸秆是我国农田最重要的有机资源，秸秆还田能有效增加土壤有机质含量并提升地力，秸秆的资源化管理是我国农田可持续利用和生态环境建设中面临的紧迫任务。亚热带地区水稻土中参与有机物质转化的微生物存在时空变异。研究亚热带典型水稻土中秸秆降解过程的微生物代谢网络及其驱动机制，对于加快推进我国秸秆资源化利用具有重要的理论和实践意义。基于以上目的，本项目系统的研究了我国亚热带水稻土秸秆降解及其微生物学驱动机制。首先揭示了区域尺度下微生物群落和土壤有机质转化存在密切的相关性。虽然微生物驱动的土壤有机质过程具有很强的地域性分异规律，但是人类农业活动会降低区域尺度下的分异性。秸秆降解过程是一个受到秸秆化学性质调控的微生物群落接力过程，在此过程中不仅传统意义上的秸秆降解微生物参与，还有很多辅助型的物种通过提供氮素和传递电子等多种途径协同促进秸秆的降解。虽然参与秸秆降解的微生物物种在多个站点间的存在空间分异特性，但是在群落构建、代谢通路网络和功能基因层面，是一个高度一致和有序的微生物过程，主要受到秸秆化学性质的控制，同时土壤肥力和气候条件也有一定影响。最后，我们发现可以通过适当的农业措施，例如平衡施肥，调控微生物组，促进秸秆还田过程，加速土壤地力的提升。