Sediment connectivity in different karst watersheds

As a key parameter reflecting the hydrological and soil erosion processes, sediment connectivity is influenced by many factors such as the climate, lithology, soil, topography, and landscape. However, there are few studies on decoupling these factors on sediment connectivity in karst watersheds of southwest China, which is featured by extreme climate, unique lithology, rugged topography, and heterogeneous landscape. To address this issue, the objective of this study was to quantify the relative importance of climate, lithology, soil, topography and landscape on sediment connectivity by partial least squares-structural equation model (PLS-SEM) in 40 typical karst watersheds in southwest China. Results showed that the average annual connectivity index (IC) ranged from -0.46 to 1.73 during 2009-2012 for different watersheds. The 92% of the IC variation can be explained by climate, lithology, soil, topography and landscape, among which topography and landscape are the main factors controlling the change of IC. Specifically, the topographic factors have the most significant positive influence on the IC (P < 0.01, path coefficient (β) = 0.708). Different from topography, landscape factors had a significant negative effect on IC (P < 0.05, β= -0.249). By clarifying the coupling relationship framework among the variables, the results are helpful to understand the spatial heterogeneity of sediment connectivity, and provide valuable information for formulating soil and water conservation strategies and optimizing land resource utilization in karst watersheds.