喀斯特小流域土壤有机碳空间异质性及储量估算方法

Study on spatial heterogeneity and reserve estimation of soil organic carbon in a small karst catchment

为了准确估算土壤有机碳储量,利用网格法采集2755个土壤剖面,共计23536个土壤样品,研究了喀斯特小流域土壤有机碳含量分布特征,并以"土壤类型法"为基准,对土壤分布面积、石砾含量、岩石裸露率、土层厚度等指标进行修正,合理的优化了土壤有机碳储量计算公式,探索出一种专属于喀斯特地区土壤有机碳储量的估算方法,结果表明:不同土层深度和土壤类型下土壤有机碳含量存在明显差异,土壤有机碳含量随着土层深度的增加而逐渐减小,不同土属的有机碳含量减小的幅度有所差异,不同坡位和坡向的有机碳含量大小为:阳坡>阴坡,坡中上部>坡顶>坡中>坡中下坡>坡底,不同土地利用方式下土壤有机碳含量大小顺序为:林地>灌草地>旱地>水田;土壤有机碳含量与坡度、海拔、岩石裸露率均呈极显著正相关关系,与土层厚度、土壤容重呈显著负相关;喀斯特地区土壤异质性较大,不同修正指标对土壤有机碳储量估算的影响程度为:土壤厚度>岩石裸露率>石砾含量>土壤有机碳含量>土壤容重;通过修正后的计算公式估算出普定后寨河小流域表层20 cm土壤有机碳密度区间为3.53—5.44 kg/m^2,平均值为:1.24 kg/m^2,100 cm土壤有机碳密度区间为4.44—14.50 kg/m^2,平均值为12.12 kg/m^2,土壤有机碳储量为5.39×10~5t。

Using a grid-based sampling method, 2755 soil profiles consisting of 23536 soil samples were sampled and analyzed to study the spatial distribution of soil organic carbon （SOC） in the karst basin of Guizhou Province. Further, we established an estimation method of SOC stock exclusively for karst after correcting for soil distribution area, particle content, percentage of exposed rock, and there were obvious differences in the SOC decreased with an increase in soil depth, soil thickness, and optimizing the calculation formula. The results showed that content of different soil types and at different soil depths. The content of SOC but the extent of the decrease differed in soils of different types. The content of SOC in soils on shady slopes was higher than that in soils on Sunny slopes. The content of SOC at different slope positions decreased in the following order： upper-middle, top, middle, lower-middle, and bottom. There was extensive SOC heterogeneity in the karst area. The order of SOC content under different land use patterns was as follows ： woodland 〉 shrub grassland 〉 dry land 〉 paddy field. SOC content showed a very significant positive correlation with slope, elevation, and percentage of exposed rock, and a significant negative correlation with soil thickness and soil bulk density. There was a large spatial variability in SOC in the karst area, with the influences of different indicators for SOC reserve estimation being as follows： soil thickness 〉 percentage of exposed rock 〉 particle content 〉 content of SOC 〉 soil bulk density. Using the revised formula to make estimations, the SOC density of the surface 20 cm of soil in a small watershed of the ttouzhai River catchment in Pndin was 3.53-5.44 kg/m2, with an average value of 1.24 kg/m2. The SOC of the surface 100 cm of soil was 4.44-14.50 kg/m^2, with an average value of 12.12 kg/m2, and the SOC storage was 5.39 × 105 t.