Influence of Landscape Pattern Evolution on Soil Conservation in a Red Soil Hilly Watershed of Southern China

Abstract

The Tingjiang Watershed is a typical mountainous area with red soil in the south of China. Due to the high rainfall intensity, significant cultivated land expansion, and accelerated urbanization, ecological problems such as soil erosion are prominent in the study area. Based on the land use, precipitation, digital elevation model (DEM), normalized difference vegetation Index (NDVI), and soil types in 2000, 2010, and 2020, the landscape pattern and soil conservation in the Tingjiang Watershed were assessed at the sub-watershed scale. The spatial correlation between soil conservation and landscape pattern was analyzed using GeoDA software. The results show the following: (1) From 2000 to 2020, the total amount of soil conservation decreased by 4.15 × 108 t. In terms of spatial analysis, the amount of soil conservation in the Tingjiang Watershed showed an upward and then downward trend in the north and a downward trend in the south, with the most obvious downward trend in the southeast and the northeast. (2) Fragmentation of the overall landscape pattern in the Tingjiang Watershed has increased. The discrete degree and homogeneity of patches decreased in Changting County, while landscape heterogeneity and homogeneity increased in Shanghang, Liancheng, and Yongding Counties. (3) Soil conservation was significantly correlated with the landscape indices patch density (PD), landscape shape index (LSI), mean patch area (AREA_MN), patch cohesion index (COHESION), splitting index (SPLIT), and Shannon evenness index (SHEI). Sub-watersheds with low soil conservation had landscape splitting index, landscape dispersion, patch type richness, and boundary complexity. These areas were mainly distributed in the southern part of the watershed. Sub-watersheds with higher soil conservation were characterized by low patch fragmentation and strong connectivity of dominant patches, which were mainly located in the northern part of the watershed. (4) The spatial error model (SEM) fit better in 2000, 2010, and 2020 compared with the spatial lag model (SLM) and ordinary least squares regression (OLS). The diagnostic results of the SEM model show that among the six landscape indices, PD, SHEI, and AREA_MN are the main influencing factors affecting soil conservation in the watershed to different degrees. The purpose of this study was to investigate the response state of soil conservation capacity as landscape patterns evolve in the Tingjiang Watershed, with the goal of providing a reference for landscape planning and management as well as soil erosion management in the watershed.