青藏高原土壤可蚀性K值的空间分布特征

Spatial Distribution Characteristics of Soil Erodibility KValue in Qinghai-Tibet Plateau

土壤可蚀性反映了土壤对水力侵蚀作用的敏感性,是进行土壤侵蚀评价和预报的重要参数。收集了青藏高原1 255个典型土壤剖面资料,采用模型计算和面积加权分析方法确定了每一个土壤亚类的土壤可蚀性K值,结合青藏高原1∶100万土壤类型图,分析了青藏高原土壤可蚀性K值的空间格局特征。结果表明,青藏高原土壤可蚀性K值平均为0.230 8,低可蚀性、较低可蚀性、中等可蚀性、较高可蚀性和高可蚀性土壤面积分别占该区面积的5.60%,18.23%,24.35%,44.02%和7.80%。土壤可蚀性以中等可蚀性和较高可蚀性为主,二者分布面积之和达1.77×106 km2,占青藏高原总面积的68.37%;较高可蚀性、高可蚀性土壤主要分布在青藏高原中西部的羌塘高原、柴达木盆地和横断山区的低海拔河谷中。青藏高原土壤可蚀性K值具有明显的垂直分异特征,在横断山区最为显著,土壤可蚀性随海拔高度升高而降低。不同海拔高度的水热分异影响了土壤的理化特性,进而决定了青藏高原土壤可蚀性的垂直分带特征。

Soil erodibility is an important index to measure soil susceptibility to water erosion, and an essential parameter needed for soil erosion evaluation and soil erosion prediction. Based on 1 255 typical soil profile data, the values of soil erodibility（K values） of all the soil types on the Qinghai--Tibet Plateau were calculated by erosion- produtivity impact calculator（EPIC） mathematical model and GIS. On which the weighted averages of the areas with the different values of soil erodibility are derived, and the distribution of the values of soil erod- ibility is analyzed based on map（1 ： 1 000 000） of soil types in the Qinghai--Tibet Plateau. The results showed that the mean value of soil erodibility was 0. 230 8, and the area of lower, less lower, moderate, less higher, higher erodibility soils occupied 5.60%, 18.23%, 24.35%, 44.02% and 7.80% of the Qinghai-- Tibet Plateau, respectively. The total area of moderate and less higher erodibility soils is 1. 77 × 10^6 km2 which is 68.37% of the total research area. The less higher and higher erodibility soils distribute in the Qiangtang Plateau, the Qaidam Basin and the valley of the Hengduan Mountains. Soil erodibility vertical variations are obvious in the Qinghai--Tibet Plateau, and especially in the Hengduan Mountains. Soil erodibility shows a decreasing trend from lower altitude to higher altitude. The physical and chemical properties of soils are affected by the water and the heat condition along an elevational gradient, and then the vertical variations of the physical and chemical properties of soils determine the vertical variations of the soil erodibility.