流域尺度下地形属性对土壤质地类型变异的影响——以重庆市彭水县一小流域为例

为探究流域尺度下地形属性对土壤质地类型变异的影响，以西南地区重庆市彭水县的一个流域为研究区，基于成土母质和地形因子，运用分类回归树（Classification and regression tree，CART）模型，对研究区1165个样点数据进行分析。结果表明：成土母质和地形因子均对土壤质地类型有重要影响，相对重要性较高的因子排序：成土母质（PAR） > 风效应（WindEff） > 地形湿度指数（SAGATWI）；不同母质、不同质地之间地形因子存在显著差异，风效应（WindEff）和漫射辐射（DiffuseIns）分别是奥陶系和志留系母质条件下影响土壤质地分类的相对重要性最高的地形因子；流域尺度CART模型解释率为86.3%，说明CART模型对土壤质地分类精度高。研究表明，基于成土母质和地形因子构建的模型解释效果好，影响显著，可为该地区土壤利用区划和管理提供科学依据。

Effect of topographic attributes on soil texture class variations at a watershed scale: A case study of a basin in Pengshui County of Chongqing, China

A total of 1165 samples were collected from the topsoil at a depth of 20 cm to explore the effect of soil material and topography on the variation of soil texture classification over a basin of Pengshui in Chongqing, southwest China. Classification and regression tree (CART)method was applied to class the soil texture based on parent materials and terrain indicators (elevation, slope, slope height, slope length, flow accumulation, SAGA topographical wetness index, flow path length, vector ruggedness, measure multi-resolution index of valley bottom flatness, multi-resolution index of the ridge top flatness, diffuse insolation, wind effect, wind exposition index). The major influencing factors on soil texture class variability were investigated by the CART model. The results showed that:Parent material and topographic factors both had important effects on soil texture class variations, the factors with higher relative importance were parent material (PAR) > wind effect (WindEff) > SAGA topographic wetness index (SAGATWI); The relative importance of terrain attributes to soil texture class variations varied with parent materials, wind effect (WindEff)and diffuse insolation (DiffuseIns) were the most essential variables for the Ordovician and the Silurian. The CART model produced a good accuracy with 86.3% (P<0.05) for the watershed. The results could provide a scientific basis for the rational planning and management of soil utilization in this area.