Distribution of Soils and Landform Relationships in Permafrost Regions of the Western Qinghai-Xizang (Tibetan) Plateau, China

Abstract

We evaluated software predictions involving soil distributions across landscape positions using selected soil morphology and terrain features in the permafrost regions of the Qinghai-Xizang (Tibetan) Plateau. The relationships presented are based on the Soil Taxonomy System and the 2010 soil suborders coupled with defined environmental factors and predict the spatial distribution of the soil suborders, using the See 5.0 decision tree software integrated with the soil-land inference model. Ten environmental factors closely related to permafrost-affected soil formation were selected as variables for the model: soil parent material, land surface temperatures, elevation, slope gradient, slope aspect, planform and profile curvatures, wetness index, and Normalized Difference Vegetation Index. A total of 62 soil profiles from 2010 were used for model building and validation. The results showed that the soils in the study area were primarily Turbels, Cryids, and Psamments, which cover 47.9%, 22.3%, and 11.7%, respectively, of the total area. Altitude had the closest relationship with soil type; in addition, permafrost played an important role in the soil-forming processes, which led to higher water content in the higher altitudes than in the lower altitudes in the arid areas. The thickness of the active layer in the study area was usually more than 2 m; however, additional consideration of the thickness of the active layer within the Soil Taxonomy System is required.