Fingerprinting sediment sources in two typical watersheds in the dry-hot valleys of Southwest China: The role of gully and orchard land

Abstract

Identifying the contributions of sediment sources is important for effectively understanding soil erosion processes, adopting appropriate management measures, and optimizing soil conservation strategies. Currently, the sediment fingerprinting technique has gained significant attention worldwide to assess the contributions of sediment sources; however, such studies in the dry-hot valleys of Southwest China, one of the most important sediment sources for several major rivers (e.g., the Yangtze, Mekong, Salween and Yuanjiang River), are largely lacking. In this study, two typical, small watersheds in the dry-hot valley in the Yuanjiang river, which were representative of the landscape, were selected to quantify the relative contributions of potential sediment sources based on the sediment fingerprinting technique. In the orchard-forest watershed, four potential sediment sources, including the slope and level of orchard land, forest, and gully, were identified, while two sources (gully and slope) were identified for the shrub-grass watershed, and the relative contributions of these sources were estimated based on the Bayesian model. The results indicate the following:1) The gully contributed to 55.43% of the total sediment in the shrub-grass watershed, indicating that gully erosion is still significant in the dry-hot valleys, which is in accordance with several previous studies; 2) the ecological restoration in the gully in the orchard-forest watershed has greatly improved the vegetation cover from 2014 to 2021 and substantially reduced the sediment contribution of the gully, indicating that vegetation restoration is an effective ways to reduce sediment yield at the watershed scale; and 3) the orchard land, with an area proportion of<40%, in the orchard-forest watershed contributed to more than 90% of the sediment; this highlights the dominant role of orchard land in sediment yield in the watershed of the dry-hot valley, implying that suitable conservation strategies are necessary to protect soil in the orchard-related watersheds. This study quantitatively evaluated the relative contributions of the main sediment sources in dry-hot valleys, a natural gully, a gully with vegetation restoration, and orchard land, through combined studies. The results of this study could be helpful for deploying appropriate measures to reduce soil erosion and sediment yield in dry-hot valleys.