小流域尺度土壤可蚀性(K值)的变异及不同采样密度对其估值精度的影响

以观音寺小流域为例,通过高密度采样,利用EPIC模型中土壤可蚀性K值计算公式计算了可蚀性K值,并运用逆距离加权插值方法生成了研究区的K值分布图。经典统计学方法分析表明,在小流域尺度下土壤可蚀性K值存在很强的空间变异性,其变异系数达39.94%。因此,定量监测、评价流域水土流失时,K值的这种空间变异性不能忽略。对不同采样密度下K值空间估值精度的评价表明,当采样点数目均匀地减少一半时,即4个/km2的样点密度下,K值估计误差仍然可以控制在25%以内。

Spatial Variability of Soil Erodibility K Value and Influence of Sampling Densities on K Value Accuracy at a Scale of Small Watershed

Taking the Guangyinsi watershed as an example,soil erodibility K values were calculated using EPIC model at large sampling densities,and the distribution map of K values was made using inverse distance weighting spatial interpolation.Classical statistical analyses show significant spatial variability of soil erodibility K values at a scale of small watershed,the variance coefficient of which is 39.94%.Therefore,the spatial variability should be taken into account in soil erosion monitoring at a scale of small watershed.The relative error of K values is less than 25% when half of the total samples,4 samples per square kilometer,are taken.