华南丘陵区2种土地利用方式下地表CH4和N2O通量研究

CH4 and N2O Fluxes from Soil Surface of 2 Land Use in Hilly Area of South China

摘要:

采用静态箱-气相色谱法对华南丘陵区马尾松林和果园地表CH4 和N2O通量及其主要影响因子进行了观测(马尾松Pinus massoniana林为期16个月，果园15个月)，比较和分析了不同土地利用方式下地表CH4和N2O通量的季节变化, 地表CH4和N2O通量与温度和土壤含水量的关系以及凋落物对地表CH4和N2O的通量影响。结果表明, 在有凋落物覆盖下，马尾松林和果园年均地表CH4通量分别为-3.41±0.3和-3.24±0.44 kg CH4 hm-2a-1；年均地表N2O通量分别为4.57±0.50和11.99±0.67 kg N2O-N hm-2a-1；去除凋落物情况下，马尾松林和果园年均地表CH4通量分别为-2.98±0.44和-1.93±0.53 kg CH4 hm-2a-1；年均地表N2O通量分别为3.12±0.28和9.42±0.56 kg N2O-N hm-2a-1。2种土地利用方式对地表CH4影响较小，对N2O通量的影响较大，果园地表N2O通量显著大于马尾松林(P<0.01)。马尾松林和果园土壤对CH4的吸收在旱季(10~3月)高而雨季(4~9月)低，N2O排放雨季较高而旱季较低。土壤含水量对地表CH4和N2O的通量影响比温度要大。凋落物对地表CH4通量的影响较小，对N2O通量的影响较大，凋落物对马尾松林和果园N2O排放的贡献率分别为31.71％和21.40％。研究还表明，地表N2O通量存在明显的降雨驱动效应。

Abstract:

The CH4 and N2O fluxes from soil surface of different land use in a hilly area of South China were examined from 2004-03-30 to 2005-07-27. CH4 and N2O fluxes were measured with closed static chamber and a modified gas chromatograph (HP5890Ⅱ) in situ in two different land-use types: plantation mainly composed of Pinus massoniana and orchard of Dimocarpus longan, respectively. There were two sets of plots at both sites respectively: ones were covered with litters on the surface soil and the others without litters. The annual average CH4 fluxes from plot with litters were -3.41±0.3 kg CH4 hm-2a-1 in the pine plantation and -3.24±0.44 kg CH4 hm-2a-1 in the orchard; annual average N2O fluxes were 4.57±0.50 kg N2O-N hm-2a-1 and 11.99±0.67 kg N2O-N hm-2a-1, respectively. The annual average CH4 fluxes from plot without litters were -2.98±0.44 kg CH4 hm-2a-1 in the pine plantation and -1.93±0.53 kg CH4 hm-2a-1 in the orchard; annual average N2O fluxes were 3.12±0.28 kg N2O-N hm-2a-1 and 9.42±0.56 kg N2O-N hm-2a-1, respectively. N2O fluxes from soil surface were closely related to the types of land use. They were significantly higher from orchard than those from pine plantation (P<0.01). CH4 absorptions were higher in dry season (October~March) and lower in rainy season (April~September). N2O fluxes were higher in rainy season and lower in dry season. The results indicated that CH4 and N2O fluxes from soil surface were affected by soil water content more than temperature. CH4 absorptions were affected little by litter removal. The litter decomposition accounted for 31.71％ and 21.40％ of the total N2O emissions from the pine plantation and from orchard soil surface, respectively. The result also indicated that there was a dominant driving effect of precipitation on the N2O flux from soil surface in rainy season.