内蒙古典型草原土壤固碳潜力及其不确定性的估算

Estimation of soil carbon sequestration potential in typical steppe of Inner Mongolia and associated uncertainty

以内蒙古锡林郭勒盟典型草原围封和放牧对照的实测数据为基础,比较了不同植物群落类型的碳储量和固碳量,并估算了重度退化草地完全恢复后的土壤固碳潜力.结果表明:在局地尺度上,以羊草、大针茅和克氏针茅为优势种的3种植被类型的年均固碳量均随着围封年限的增加而减少.羊草和大针茅草原群落的碳储量显著高于克氏针茅草原群落,而在过牧导致的退化过程中,后者流失了更多的土壤有机碳,其固碳潜力高于前两者.在区域尺度上,内蒙古典型草原土壤表层0～20cm的固碳潜力在-0.03×104～3.71×104kgC·a-1范围内变化,总固碳潜力为12.1×108kgC·a-1.不确定性分析发现,忽略石砾含量不会造成土壤固碳潜力估算值的较大偏差,而气象数据空间插值造成的误差为±4.7×109kgC·a-1.假设未来生长季降水的平均变化值为-3.2mm·(10a)-1时,土壤固碳潜力将减少1.07×108kgC·(10a)-1.

Based on the measurements in the enclosure and uncontrolled grazing plots in the typical steppe of Xilinguole, Inner Mongolia, this paper studied the soil carbon storage and carbon sequestration in the grasslands dominated by Leymus chinensis, Stipa grandis, and Stipa krylovii, respectively, and estimated the regional scale soil carbon sequestration potential in the heavily degraded grassland after restoration. At local scale, the annual soil carbon sequestration in the three grasslands all decreased with increasing year of enclosure. The soil organic carbon storage was significantly higher in the grasslands dominated by L. chinensis and Stipa grandis than in that dominated by Stipa krylovii, but the latter had much higher soil carbon sequestration potential, because of the greater loss of soil organic carbon during the degradation process due to overgrazing. At regional scale, the soil carbon sequestration potential at the depth of 0-20 cm varied from -0.03×104 to 3.71×104 kg C·a-1, and the total carbon sequestration potential was 12.1×108 kg C·a-1. Uncertainty analysis indicated that soil gravel content had less effect on the estimated carbon sequestration potential, but the estimation errors resulted from the spatial interpolation of climate data could be about ±4.7×109 kg C·a-1. In the future, if the growth season precipitation in this region had an average variation of -3.2 mm·（10 a）-1, the soil carbon sequestration potential would be decreased by 1.07×108 kg C·（10 a）-1.