Disentangling influences of driving forces on intra-annual variability in sediment discharge in karst watersheds

Fengjiao Pan; Zhenwei Li; Hongxia Xie; Xianli Xu; Liangxia Duan

doi:10.1016/j.scitotenv.2024.171486

Disentangling influences of driving forces on intra-annual variability in sediment discharge in karst watersheds

Sci Total Environ. 2024 May 1:923:171486. doi: 10.1016/j.scitotenv.2024.171486. Epub 2024 Mar 5.

Authors

Fengjiao Pan¹, Zhenwei Li², Hongxia Xie¹, Xianli Xu³, Liangxia Duan⁴

Affiliations

¹ College of Resources, Hunan Agricultural University, Changsha 410128, China.
² Huanjiang Observation and Research Station for Karst Ecosystem, Key Laboratory for Agro-Ecological Processes in Subtropical Region, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha 410125, China. Electronic address: lizhenwei337@isa.ac.cn.
³ Huanjiang Observation and Research Station for Karst Ecosystem, Key Laboratory for Agro-Ecological Processes in Subtropical Region, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha 410125, China. Electronic address: xianlixu@isa.ac.cn.
⁴ College of Resources, Hunan Agricultural University, Changsha 410128, China. Electronic address: duanliangxia@hunau.edu.cn.

PMID: 38447723
DOI: 10.1016/j.scitotenv.2024.171486

Abstract

The intra-annual variability in sediment discharge was considerably influenced by the climate variability and vegetation dynamics. Because of the coupled or relationships between climatic and vegetation variables, it is still challenging to decouple the direct and indirect effects of climate variability and vegetation dynamics on hydrological and sediment transport processes. The purpose of this study is to decouple influences of individual driving force on intra-annual distribution of sediment discharge during 2003-2017 using the partial least squares structural equation model (PLS-SEM) method in four typical karst watersheds of Southwest China. The coefficient of variation (Cv), Completely regulation coefficient (Cr), Lorenz asymmetry coefficient and Gini coefficient were used to represent the intra-annual sediment discharge variability. Results showed that the monthly sediment discharge (190 % < Cv < 353 %) exhibited greater variability than its potential affecting factors (18 % < Cv < 101 %). From the PLS-SEM analysis, the water discharge, climate, and vegetation together explain 57 %-75 %, 64 %-79 %, and 53 %-80 % of the total variance in Cv, Cr, and Gini coefficient, respectively. Specifically, water discharge exerts the largest influence on sediment discharge variability (0.65 ≤ direct effect ≤0.97, P < 0.05), while vegetation dynamic mainly indirectly affects sediment discharge variability (-0.88 ≤ indirect effect ≤ -0.01) through influencing water discharge. The climate factors also principally indirectly affect the sediment discharge variability (-0.47 ≤ indirect effect ≤0.19) by affecting water discharge and vegetation. The PLS-SEM can effectively reveal the driving force and influencing mechanism of intra-annual sediment discharge changes, and provide an important reference for regional soil and water resources management in karst watersheds. Future studies can decouple the influences of the extreme climate, unique lithology, discontinuous soil, heterogeneous landscape, and special geomorphology on spatial variability in sediment discharge across different karst watersheds.

Keywords: Completely regulation coefficient; Gini coefficient; Karst ecosystems; Lorenz asymmetry coefficient; Soil erosion.