Sediment yield is closely related to lithology and landscape properties in heterogeneous karst watersheds

As one of the largest contiguous karst regions in the world, Southwest China is vulnerable to soil erosion because of its unique geology and inappropriate land use. Understanding the linkages between geological conditions, land cover patterns and sediment yield is thus of paramount importance to effectively control sediment delivery in heterogeneous karst watersheds. The objective of this study was to examine how the specific sediment yield was related to lithology and landscape variables for 40 karst watersheds in southwest China. Due to these watershed variables were highly codependent, partial least squares regression (PLSR) was applied to elucidate the relationship between the sediment yield and 30 lithology and landscape variables. The first-order controls were determined by calculating the variable importance for the projection (VIP). Predictors with VIP scores larger than 1 were considered to be the most influential predictors of the PLSR model. Results indicated that the lithology and landscape indeed exerted substantial influence on sediment yield (explained variance: 66.8%) for the investigated 40 watersheds. Specifically, the first dominant factor for sediment yield was karst coverage (VIP = 2.19), followed by dolomite coverage (VIP = 1.42), landscape shape index (VIP = 1.33), patch richness (VIP = 1.23), relative patch richness (VIP = 1.23), number of patches (VIP = 1.22), and Simpson's diversity index (VIP = 1.03). The PLSR technique enabled the elimination of codependency among the variables and facilitated a more unbiased view of the control factors for sediment yield. Therefore, this approach is recommended as a useful tool for identifying the dominant factors controlling sediment yield in heterogeneous karst watersheds.