内蒙古河套灌区不同盐碱程度土壤CH4吸收规律

土壤盐碱化严重威胁土地可持续利用和温室气体排放.本研究选择内蒙古河套灌区3种盐碱土壤［S1：盐化土壤，电导率（EC）4.80 dS·m^-1；S2：强度盐碱土壤，电导率（EC）2.60 dS·m^-1；S3：轻度盐碱土壤，电导率（EC）0.74 dS·m^-1］.利用静态暗箱法野外原位观测研究盐碱土壤甲烷（CH₄）吸收规律.结果表明，不同盐碱程度土壤CH₄吸收每年均存在显著差异，2014年生长季（F=18.0，P<0.001），2015年生长季（F=23.6，P<0.001）和2016年生长季（F=28.4，P<0.001）.轻度盐碱土壤CH₄累积吸收量最高，盐化土壤累积吸收量最低.随土壤盐碱程度加重，土壤CH₄累积吸收量降低.轻度盐碱土壤CH₄累积吸收量在2014~2016年3个生长季（4~10月）分别为150.0、119.6和99.9 mg·m^-2；重度盐碱土壤CH₄累积吸收量比轻度盐碱土壤分别降低27%、28%和19%；盐化土壤CH₄累积吸收量比轻度盐碱土壤分别降低35%、35%和53%.冗余分析表明，盐碱土壤CH₄吸收通量与土壤EC的投影在第一主成分轴正方向和反方向，土壤EC越高，CH₄吸收通量越低.土壤电导率EC是调控盐碱土壤CH₄吸收的关键因子，相关系数r为-0.8809（P<0.01，n=9）.

CH4 Uptake in Different Saline-alkaline Soils in Hetao Irrigation District, Inner Mongolia

Soil salinization poses a great threat to sustainable land use and the limitation of greenhouse gas emissions. In this study, three saline alkali soils, saline soilelectrical conductivity (EC) 4.80 dS·m^-1], high saline-alkaline soil (EC 2.60 dS·m^-1), and low saline-alkaline soil (EC 0.74 dS·m^-1) in the Hetao Irrigation District of Inner Mongolia were selected as research plots. Field experiments were conducted to study the uptake of methane (CH₄) in the crop-growing season (April-October) for three years (2014-2016) using the static box method. There were significant differences in the soil CH₄ uptake among the soil types in 2014 (F=18.0, P<0.001), 2015 (F=23.6, P<0.001), and 2016 (F=28.4, P<0.001). The uptake of CH₄ by the soil decreases with increasing soil salinity. The accumulated CH₄ uptake was 150.0 mg·m^-2, 119.6 mg·m^-2, and 99.9 mg·m^-2 in the low saline-alkaline, high saline-alkaline, and saline soil in 2014, respectively. The cumulative uptake of CH₄ was 27%, 28%, and 19% lower in the high saline-alkaline soil and 35%, 35%, and 53% lower in the saline soil than in the low saline-alkaline soil in 2014, 2015, and 2016, respectively. Redundancy analysis shows that the projection of the CH₄ uptake flux and EC of saline-alkaline soil are in the positive direction, and in the opposite direction to the first principal component axis. The higher the soil EC, the lower the CH₄ uptake flux. Soil EC was found to be the key factor controlling the uptakes of CH₄, with a correlation coefficient (r) of -0.8809 (P<0.01, n=9).