Temporal Variations in Sediment Connectivity in Karst Watersheds

Abstract

Sediment connectivity reflects the connectivity between sediment sources and sinks and helps to understand soil erosion and sediment transport processes. However, the potential effects of climatic factors and vegetation restoration on sediment connectivity are not fully understood, especially in the karst area of southwest China which has a serious rocky desertification and fragile ecological environment. The purpose of this study was to quantify the connectivity index (IC), runoff and sediment yield changes induced by the coupling impacts of climate change and vegetation restoration in six typical karst watersheds. The annual climate, vegetation, land use, soil, runoff and sediment yield data were collected during 2000-2019. The parameters of IC were calculated based on source-sink landscape index. The Partial least squares structural equation model (PLS-SEM) were used to quantify the impacts of climate change and vegetation restoration to IC, and runoff and sediment yield changes. The results showed that the average IC value ranges from 2.10 to 2.98 during 2000–2019 with an insignificant decreasing trend. PLS-SEM analysis showed that the climatic and vegetation factors together only explained 0-7% of the IC value change. In contrast, the climatic and vegetation factors can explain 53%~90% of the runoff dynamics, and climate factors, vegetation dynamics, runoff and IC value together explain 21%~67% of the sediment yield variation. These results are helpful for understanding the temporal variation in IC and is of great significance for ecological restoration and sediment delivery control in karst areas.

Keywords: Soil erosion, Sediment connectivity index, Source-sink landscape index, Land use and land cover, Karst ecosystems