Jia Zhongjun, Cai Zucong
Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China.
Ying Yong Sheng Tai Xue Bao. 2003 Nov;14(11):2049-53.
Methane emission from rice paddy fields is the net result of the combination of many processes, i.e., CH4 production, CH4 oxidation and CH4 transportation in paddy soil. Rice plants play a key role in the CH4 emission from paddy fields, particularly in all the processes involved. The positive and negative effects of rice plants on CH4 emission from paddy fields are well recognized as the main factors influencing the temporal variation of CH4 emission flux in paddy field. Process-based studies about the effects of rice plants on methane emission from paddy fields were summarized, and different roles of rice plants on this emission were discussed. Root exudates and litters of rice plants could serve as the substrate for methanogenesis and enhance the CH4 production of paddy soils, resulting in a high CH4 emission peak, particularly in rice late growing season. Rhizospheric CH4 oxidation induced by rice root-excreted oxygen constitutes a main biogenic sink of CH4, which could account for 36-90% of CH4 produced in paddy soil over the entire growing season of rice. Up to 80% and more of CH4 released from rice field during a growing season could be emitted by rice plant-mediated transport. The fully developed aerenchyma of rice plants could be of importance in CH4 emission during rice growing seasons, and responsible for the CH4 emission peak observed at rice early growing season.
稻田甲烷排放是多种过程综合作用的净结果，即稻田土壤中的甲烷产生、甲烷氧化和甲烷传输。水稻植株在稻田甲烷排放中起着关键作用，尤其是在所有相关过程中。水稻植株对稻田甲烷排放的正负效应是影响稻田甲烷排放通量时间变化的主要因素，这一点已得到广泛认可。本文总结了基于过程的水稻植株对稻田甲烷排放影响的研究，并讨论了水稻植株在这一排放过程中的不同作用。水稻植株的根系分泌物和凋落物可作为产甲烷的底物，增强稻田土壤的甲烷产生，导致甲烷排放出现高峰，尤其是在水稻生长后期。水稻根系分泌的氧气诱导根际甲烷氧化，构成甲烷的主要生物汇，在水稻整个生长季中，其可占稻田土壤中产生的甲烷的36% - 90%。在一个生长季中，稻田释放的甲烷中高达80%及以上可通过水稻植株介导的传输排放。水稻植株发育完全的通气组织在水稻生长季的甲烷排放中可能起重要作用，并导致在水稻生长早期观察到甲烷排放高峰。
