川中丘陵地区冬水田甲烷排放特征研究

以川中丘陵地区典型冬水田为对象,设置了有水稻常规施肥(RF)、无水稻常规施肥(NP)、有水稻无氮肥(NN)3种处理,以静态暗箱-气相色谱法对甲烷(CH_4)排放进行了原位观测.结果表明,RF、NP和NN处理下CH_4排放通量分别为-0.0042~18.29、0.03~16.78和0.10~26.76mg·m~(-2)·h~(-1),平均排放通量分别为10.22、4.25和14.15 mg·m~(-2)·h~(-1)(以每平方米每小时消耗/产生的C量(mg)计),水稻生长季是主要排放期,但休闲季CH_4排放量仍占全年CH_4总排放量的14%.没有水稻处理的CH_4排放量显著低于有水稻处理(p0.01);而不施氮肥处理的CH_4排放量显著高于施肥处理(p0.01).CH_4排放通量与5 cm深土壤温度呈显著正相关(p0.01),随着温度的升高,甲烷排放量呈指数增加.CH_4排放通量与1~4 cm的稻田水深呈显著负相关(p0.01),随着水深的增加,甲烷的排放呈指数迅速下降;而与4~8 cm的稻田水深无相关性,甲烷的排放也变化缓慢.由此表明,土壤温度和水深在很大程度上调控着CH_4的排放.此外,研究结果也显示将冬水田休闲期改为旱作可减少CH_4排放,对环境有利.

Characteristics of methane emission from winter flooded paddy field in the hilly area of central Sichuan Province

This study was conducted to investigate CH₄ fluxes and associated environmental factors from a typical winter paddy field in the hilly region of central Sichuan Province. Three treatments were set, i.e. rice-flooded fallow rotation (RF), no plant (NP) and no nitrogen fertilizer (NN). CH₄ fluxes were analyzed by the static opaque chamber and gas chromatography techniques. The results showed that CH₄ fluxes from treatments of RF, NP and NN varied from -0.0042~18.29, 0.03~16.78 and 0.10~26.76 mg·m^-2·h^-1, with average fluxes of 10.22, 4.25 and 14.15 mg·m^-2·h^-1, respectively. The emissions of CH₄ mainly occurred in a paddy soil during rice-growing season. However, emissions of CH₄ in non-cropping season accounted for 14% of the total annual emissions, which could not be ignored. CH₄ emission after treatment of RF was significantly higher than that of NP but lower than that of NN (p<0.01). CH₄ emissions were positively correlated with soil temperature at the 5 cm depth (p<0.01) due to the exponential increase of the amount of methane emissions with temperature. CH₄ fluxes were negatively related to water depth in 1~4 cm of paddy fields (p<0.01), which suggested that soil temperature and water depth significantly influenced the fluxes of CH₄. The study also indicated that wheat cultivation in paddy soils during non-cropping season might be an effective way to reduce the release of CH₄, which facilitated decreasing the emission of greenhouse gasses.