稻麦轮作生态系统中土壤湿度对N2O产生与排放的影响

通过对太湖地区稻麦轮作生态系统的N₂O排放及土壤湿度进行系统观测和开展一系列模拟实验,研究了降雨和土壤湿度对N₂O排放和产生过程的影响.结果表明,春季和秋季麦田N₂O排放与降雨量呈明显正相关,但水稻田和冬季麦田的N₂O排放不受降雨影响.稻麦轮作周期内的N₂O排放较强烈地受土壤湿度制约,土壤湿度为田间持水量的97～100%或84～86%WFPS(土壤体积含水量与总孔隙度的百分比)时,N₂O排放最强,低于此湿度范围时,N₂O排放通量与土壤湿度呈正相关,反之,则呈负相关.田间N₂O排放随土壤湿度的变化形式与模拟条件下培养土壤样品的N₂O产生率变化非常相似,但前者的最佳湿度范围比后者窄,而且偏小.

Impact of soil humidity on N2O production and emission from a rice-wheat rotation ecosystem

Based on the in-situ measurement of soil humidity and N₂O emission from a rice-wheat rotation ecosystem and on the simulated experiment in laboratory,the impact of precipitation and soil humidity on N₂O production and emission is studied.The results show that the N₂O emission from wheat field is positively correlated with precipitation in spring and autumn but not in winter,and that from rice field is not influenced by precipitation.Within a cycle of rice-wheat rotation, N₂O emission is intensively affected by soil humidity.97～100% of soil water holding capacity (i.e.,84～86% of WFPS) leads to a maximum N₂O emission.When the soil humidity is lower than this range,there is a positive correlation between N₂O emission flux and soil humidity, and on the contrary,there is a negative one.The variation pattern of N₂O emission with soil humidity is similar both under field and under simulated condition, although under the former one,the optimum humidity range for N₂O emission is lower.