Connectivity-mediated SOC and soil texture variation in the planted shrub ecosystem in the Loess Plateau, China

Abstract

The sediment connectivity determined by hyrological processes, topography and ground cover regulates the soil redistribution, hence the sediment budget, and variation of soil properties on hillslopes. Exploring the coupling between sediment connectivity and the variation of soil properties will enhance the understanding of the role connectivity played in eco-geomorphological feedbacks. Sediment connectivity mediates the material supply and loss simultanously. There may be threshold of sediment connectivity for the soil material budget and thus the soil properties in the vegetation patches. However, scarce of quantitative linkage between the soil properties and connectivity hampered the idenfication of the threshold. This study aimed to linked the sedimentological connectivity with variation of soil orgainc carbon (SOC) and texture on hillslope in semi-arid region on the Loess Plateau in northern China. The Relative Connectivity Index (RCI_SS) integrating upslope connectivity (UC) indicating the probability of soil materials flow in and downslope connectivity (DC) describing the probability of soil resource flow out shrub patches was developed as comprehensive indicator of sedimentological connectivity. The coupling between sedimentological connectivity and the variation of SOC and soil texture was explored at the hillslope scale. Results showed that the sediment connectivity, SOC content and sand content increased from the summit to the foot slope, but the efficiency of shrub patches to retain sediment and SOC decreased. The enhanced connectivity led to the decreased efficiency of sediment and SOC retention, and the coarsening trend of soil texture. This study revealed that the sediment connectivity may contribute to the early warning of the degradation of planted shrub ecosystems from the perspective of soil properties. This study also suggested further exploration of the connectivity threshold for ecosystem state transition by adopting eco-geomorphological framework.