华南丘陵区冬闲稻田二氧化碳、甲烷和氧化亚氮的排放特征

采用静态箱 气相色谱法对收获后冬闲稻田CO₂、CH₄和N₂O排放进行了田间原位测定，探讨了越冬稻田3种温室气体的排放规律.结果表明，残茬稻田和裸田的CO₂的排放峰值分别出现在18:00和16:00左右.日间CH₄排放为净值，夜间表现为弱吸收.残茬稻田和裸田N₂O夜间排放分别为日间平均的1.79和1.58倍.残茬稻田的昼夜CO₂平均排放通量显著高于裸田(P＜0.05).在测定期间，残茬稻田CO₂排放随温度升高而增高.相关分析表明，CO₂排放与土温、地表温度和气温均呈显著相关，表明温度是影响收获后稻田CO₂排放的主要因素.在11月10日至翌年1月18日测定期间，残茬稻田的CO₂和CH₄平均排放通量分别为(180.69±21.21) mg·m^-2·h^-1和(-0.04±0.01) mg·m^-2·h^-1，CO₂排放通量较裸田高13.06％，CH₄吸收增高50%.残茬稻田的N₂O排放通量为(21.26±19.31) μg·m^-2·h^-1，较裸田低60.75％.由此说明华南丘陵区冬闲稻田是大气CO₂和N₂O的源，CH₄的汇.

Characteristics of CO2, CH4 and N2O emissions from winter-fallowed paddy fields in hilly area of South China

With closed static chamber and modified gas chromatograph (HP5890 II), the in situ measurements were made on the CO2, CH4 and N2O emissions from winter-fallowed paddy fields in the hilly area of South China. Gas samples were taken simultaneously from the fields with and without rice stubble. The results showed that both of the fields had the peak value of CO2 flux in the late afternoon. In the fields with and without rice stubble, the CH4 flux was positive in the day time while negative in the night, and the N2O flux in the day time was 1.79 and 1.58 times as much as that in the night, respectively. The diurnal average CO2 flux in the field with rice stubble was significantly higher than that in bare field (P < 0.05). Correlation analysis demonstrated that the CO2 flux in winter-fallowed paddy fields had significant correlations with soil temperature, aboveground temperature, and air temperature, suggesting that temperature was the main factor affecting the CO2 emission from rice field after harvesting. During the observation time (from 2003-11-10 to 2004-01-18), the average CO2, CH4 and N2O fluxes in the field with rice stubble were (180.69 +/- 21.21) mg x m(-2) x h(-1), (-0.04 +/- 0.01) mg x m(-2) x h(-1) and (21.26 +/- 19.31) microg x m(-2) x h(-1), respectively. Compared with bare field, the CO2 flux in the field with rice stubble was 13.06% higher, CH4 absorption increased by 50%, while N2O flux was 60.75% lower. It was concluded that the winter fallowed paddy field in hilly area of South China was the source of atmospheric CO2 and N2O, and the sink of atmospheric CH4.