稻田土壤可溶性有机物影响甲烷产生的微生物机制

Methane is one of the most important greenhouse gases and plays an important role in global warming. Rice paddy field is a main methane emission source, thus clarifying the mechanisms of methane emission in paddy field and exploring appropriated fertilization managements to reduce it has become a research hotspot. Soil dissolved organic carbon (DOC) and methanogen play critical roles in methane emission; however, there is still knowledge gap on the relationship between the methanogen community and DOC characteristics as well as their responses to organic fertilization practices. Based on the long-term organic fertilization field experiment under double rice cropping system established since 1981, our research will investigate the temporal dynamics of methane emission flux from rice paddy field influenced by different organic amendments during rice growing period. In particular, the content and composition of DOC and the community structure and abundance of Methanogens were concomitantly analyzed with soil sampled from the corresponding field plots. Based on the comprehensive analyses of relations among DOC compositions, Methanogens community and methane emission flux, an incubation experiment manipulating the compositions of DOC amendments will be conducted under controlled conditions to varify the effects of DOC on the community structure and abundance of Methanogens. Taken together, our results will elucidate the mechanistic relationships among the DOC characteristics, Methanogens community structure and methane emission influenced by long-term different organic amendments. Besides contributing to understand the mechanism of methane emission from rice paddy field, it will also guide the opimization of organic amendment managements and furthermore facilitate the reductions of methane emission.

稻田作为大气甲烷最主要的生物源之一，对全球变暖影响重大，揭示稻田甲烷排放的影响机制及探索稻田甲烷减排措施已成为当前研究热点。土壤可溶性有机碳（DOC）和产甲烷菌在稻田甲烷产生过程中起着重要作用，而关于产甲烷菌与土壤可溶性有机碳的关系及对有机肥的响应研究非常薄弱。本研究拟借助始于1981年的红壤稻田有机肥长期定位试验，通过监测稻田甲烷排放通量、土壤DOC含量和组成及产甲烷菌群落的动态变化特征，基于微生物对DOC的依存关系，结合直接调控DOC组成的室内实验，探索有机肥作用下土壤可溶性有机物组成影响稻田甲烷产生的微生物机制。本项目的研究结果在理论上可以揭示有机肥作用下DOC性质－产甲烷菌－甲烷产生之间的关系，拓展有机肥影响稻田甲烷排放的内在机制研究；而在实践上可以指导南方稻田有机肥的合理施用及稻田甲烷减排措施的制定，具有较明显的理论探索性和应用针对性。

稻田作为大气甲烷最主要的生物源之一，对全球变暖影响重大，揭示稻田甲烷排放的影响机制、探索稻田甲烷减排措施已成为当前研究热点。本项目依托始于1981年的红壤双季稻田有机肥长期定位试验，选取早稻配施紫云英（GM）、早稻配施紫云英+晚稻配施猪粪（GM+PM）、早稻配施紫云英+晚稻配施猪粪+冬盖水稻秸秆（GM+PM+RS）、早稻配施紫云英+晚稻水稻秸秆还田（GM+RS）和氮磷钾肥配施（NPK）等5种模式，系统研究了长期有机肥作用下红壤双季稻田甲烷排放和土壤可溶性有机碳组成的动态变化规律以及稻田土壤产甲烷菌和氧化菌的群落结构动态变化特征，并分析了可溶性有机物组成对水稻土产甲烷菌群落结构及甲烷排放量的影响。研究发现，有机肥管理方式显著影响稻田有机碳的累积、可溶性有机碳的组成和甲烷排放量。稻田甲烷排放量与稻田有机肥的投入量呈显著正相关关系，以早稻配施紫云英+晚稻配施猪粪+冬盖水稻秸秆（GM+PM+RS）模式排放量最高，为29.98 g m-2，施用有机肥稻田甲烷排放总量最低为19.92 g m-2（GM），显著高于单施化肥模式的14.85 g m-2。土壤可溶性有机碳含量的季节变化受水稻生长期根系代谢活性和有机肥投入量的双重影响，其也与甲烷排放规律一致，均表现出先增加后减少的趋势。本项目采用454 FLX+平台对稻田土壤甲烷产生菌、甲烷氧化菌和细菌的群落结构进行了测序，发现不同有机肥管理方式下稻田土壤甲烷产生菌、甲烷氧化菌和细菌的群落结构差异，发现土壤甲烷产生菌的多样性和数量与有机肥投入的种类和数量呈正相关关系，证明了有机肥作用下土壤可溶性有机碳的组成、土壤甲烷产生菌的群落结构和甲烷排放量存在密切的协变关系，初步发现了土壤可溶性有机碳组成影响甲烷排放的微生物机制。这对深入了解有机肥作用下土壤有机碳累积转化过程及土壤微生物与土壤碳循环过程的交互作用有重要意义，也为制定低碳、高效的红壤稻田有机肥管理模式提供了重要依据，具有较重要的理论和实践价值。