华南地区覆膜旱种稻田甲烷排放及其与土壤水分和温度的关系

采用静态箱法和田间小区试验,研究了常规稻田和覆膜旱种稻田水稻全生育期CH4的排放规律,探讨了温度和水分与稻田CH4排放的关系。结果表明:覆膜旱种稻田的甲烷排放量明显低于常规水田的排放量,常规水田的甲烷累计排放通量为20.38g/m2,覆膜旱种稻田为2.46g/m2,水稻覆膜旱种后甲烷排放量降低了88%。常规水田CH4排放峰期持续了35d,覆膜旱种稻田CH4排放峰期为25d,两者在CH4排放高峰期的排放量分别占整个生育期累计排放量的72%和97%。覆膜旱作稻田CH4排放量降低,主要表现在最大排放峰值降低和排放峰持续时间缩短。土壤温度(5cm处)和水分与水稻生育期稻田甲烷的排放有显著正相关。CH4排放通量大于1.0mg·m-2·h-1主要集中在土壤质量含水率高于36.25%的区域,在土壤质量含水率小于36.25%时,常规稻田和覆膜旱种稻田都只有少量CH4排放。

Methane emission and its relationship with soil temperature and moisture during rice growth in film mulching upland rice field in South China

Abstract: To investigate methane fluxes in traditional paddy field and film mulching upland for late rice growth in South China, field experiment were conducted and gas sampling the closed-chamber technique were applied. The methane cumulative fluxes and global warming potential (GWP) from film mulching upland and traditional paddy field during rice growth were compared to estimate the contribution of methane fluxes from film mulching upland to greenhouse effect. Soil samples in 0-20 cm layer were collected to measure the soil water content (w/w). The thermometer was buried at 5cm soil depth in closed-chamber for gas sampling after rice transplanting. Soil temperature was obtained by the thermometer when methane was sampled. The relationships of soil moisture and soil temperature with methane fluxes were studied. Results showed that methane emitted were concentrated during the vegetative growth stage of rice both paddy field and film mulching upland. However methane emission in paddy field concentrated in former 35 days after rice transplanting with methane cumulative flux of 14 779.97 mg/m2. Methane emission in film mulching upland concentrated in former 25 days after rice transplanting with methane cumulative flux of 2 372.27 mg/m2. The percentage of CH4 cumulative flux in emission peak period and total cumulative flux in the paddy field and film mulching upland were 72% and 97%, respectively. Methane fluxes in film mulching upland were significantly lower than that in traditional paddy fields. Methane cumulative flux in film mulching upland declined by 88% compared to paddy field due to the fact maximum emission peak reduced and the emission peak period shortened. The GWP (CO2 equivalent fluxes) of methane was 468.72 g/m2 in paddy field, but 56.48 g/m2 in film mulching upland. Thus the contribution of methane fluxes to greenhouse effect in film mulching upland was lower than that in paddy field. Soil temperature and soil moisture at 5 cm soil depth had significant positive correlation with methane fluxes during the rice growth stage, respectively. The area of methane flux more than 1.0 mg·m-2·h-1 existed in the area of the soil water content (w/w) higher than 36.25%, and few methane in both paddy field and film mulching upland was emitted when soil water content was less than 36.25%.