内蒙古农牧交错带土地利用变化对CH4吸收的影响

于2008~2010年,根据邻近样地采样原则,选择位于内蒙古农牧交错带的天然草地和不同开垦时间的农田作为研究样地(G-草地; C5-开垦5a的农田;C10-开垦10a的农田;和C50-开垦50a的农田),利用静态箱法通过3a的野外试验,研究土地利用类型变化对CH4吸收的影响.结果表明:天然草地转变为农田后,不同开垦年限的农田土壤和草地土壤CH4吸收存在显著差异2008年(FCH4=273.7, P<0.001), 2009年(FCH4=264.8, P<0.001)和2010年(FCH4=362.4, P<0.001).草地转变为农田促进CH4吸收,2008, 2009 和2010年生长季的生长季(4~10月),草地CH4吸收量最低分别为141.4,210.0,236.0mg/m2.2008~2010年农田土壤CH4累积吸收量与草地土壤相比增加20%~280%.农田开垦年限影响CH4吸收,随着农田开垦年限的增加从开垦5~50a,CH4累积吸收量降低.相关分析表明,不同土壤CH4吸收与土壤水分含量和NH4+-N 含量呈负相关关系(R2=0.7380, P<0.01).草地转变为农田后,土壤水分含量和NH4+-N 含量驱动不同开垦年限的农田土壤和草地土壤CH4吸收差异.

Land-use change from grassland to cropland affects CH4 uptake in the farming-pastoral ecotone of Inner Mongolia.

CH4 uptake were compared after grassland and cropland soils in the agro-pastoral ecotone of Inner Mongolia over three growing seasons (2008~2010). Four adjacent sites with different land-use histories were selected, including grassland (reference site) and cropland 5, 10 and 50 years after conversion. The flux measurements were obtained using a closed-chamber method and were performed continuously from April to October in 2008, 2009 and 2010 in study site. The results showed a significant difference in CH4 uptake between cropland and grassland in 2008 (FCH4=273.7, P<0.001), 2009 (FCH4=264.8, P<0.001) and 2010 (FCH4=362.4, P<0.001). Grassland had the lowest CH4 uptake values of 141.4mg/m2, 210.0mg/m2 and 236.0mg/m2 in the 2008, 2009 and 2010 sampling seasons, respectively. The cumulative CH4 uptake of cropland soil increased by 20%~280%, compared with the grasslands from 2008 to 2010. Decreased cumulative CH4 uptake was observed with an increase in cropland age from 5 to 50 years. CH4 uptakes were negatively correlated with soil NH4+-N (R2=0.7380, P<0.01) and soil moisture. Our study indicated that CH4 uptake existed obviously differences among the sites during 3 growing seasons and the soil physical-chemical properties drive these differences.