Shao Jing-An, Huang Xue-Xi, Gao Ming, Wei Chao-Fu, Xie De-Ti, Cai Zu-Cong
College of Resource and Environment, Southwest Agricultural University, Chongqing 400716, China.
J Environ Sci (China). 2005;17(4):691-8.
The terrestrial ecosystem may be either a source or a sink of CH4 in rice paddies, depending, to a great extent, on the change of ecosystem types and land use patterns. CH4 emission fluxes from paddy fields under 4 cultivation patterns (conventional plain culture of rice (T1), no-tillage and ridge culture of rice (T2), no-tillage and ridge culture of rice and wheat (T3), and rice-wheat rotation (T4)) were measured with the closed chamber technique in 1996 and 1998 in Chongqing, China. The results showed that differences existed in CH4 emission from paddy fields under these land management practices. In 1996 and 1998, CH4 emission was 71.48% and 78.82% (T2), 65.93% and 57.18% (T3), and 61.53% and 34.22% (T4) of that in T1 during the rice growing season. During the non-rice growing season, CH4 emission from rice fields was 76.23% in T2 and 38.69% in TI. The accumulated annual CH4 emission in T2, T3 and T4 in 1996 decreased by 33.53%, 63.30% and 65.73%, respectively, as compared with that in T1. In 1998, the accumulated annual CH4 emission in T1, T2, T3 and T4 was 116.96 g/m2, 68.44 g/m2, 19.70 g/m2 and 11.80 g/m2, respectively. Changes in soil physical and chemical properties, in thermal and moisture conditions in the soil and in rice plant growth induced by different land use patterns were the dominant causes for the difference in CH4 emission observed. The relative contribution of various influencing factors to CH4 emission from paddy fields differed significantly under different land use patterns. However, the general trend was that chlorophyll content in rice leaves, air temperature and temperature at the 5 cm soil layer play a major role in CH4 emission from paddy fields and the effects of illumination, relative humidity and water layer depth in the paddy field and CH4 concentration in the crop canopy were relatively non-significant. Such conservative land use patterns as no-tillage and ridge culture of rice with or without rotation with wheat are thought to be beneficial to reducing CH4 emission from paddy fields and are, therefore, recommended as a significant solution to the problems of global (climatic) change.
陆地生态系统在稻田中可能是甲烷的源或汇，这在很大程度上取决于生态系统类型和土地利用模式的变化。1996年和1998年在中国重庆，采用密闭箱法测定了4种种植模式（水稻常规平作（T1）、水稻免耕垄作（T2）、水稻小麦免耕垄作（T3）和稻麦轮作（T4））下稻田的甲烷排放通量。结果表明，这些土地管理措施下稻田的甲烷排放存在差异。1996年和1998年，水稻生长季T2、T3和T4的甲烷排放量分别为T1的71.48%和78.82%、65.93%和57.18%、61.53%和34.22%。在非水稻生长季，T2稻田的甲烷排放量为76.23%，T1为38.69%。1996年，T2、T3和T4的年累计甲烷排放量分别比T1减少了33.53%、63.30%和65.73%。1998年，T1、T2、T3和T4的年累计甲烷排放量分别为116.96 g/m²、68.44 g/m²、19.70 g/m²和11.80 g/m²。不同土地利用模式引起的土壤理化性质、土壤热湿条件和水稻生长变化是观察到的甲烷排放差异的主要原因。在不同土地利用模式下，各影响因素对稻田甲烷排放的相对贡献差异显著。然而，总体趋势是水稻叶片叶绿素含量、气温和5 cm土层温度对稻田甲烷排放起主要作用，而光照、相对湿度、稻田水层深度和作物冠层甲烷浓度的影响相对不显著。诸如水稻免耕垄作（无论是否与小麦轮作）等保守的土地利用模式被认为有利于减少稻田甲烷排放，因此被推荐作为应对全球（气候）变化问题的重要解决方案。
