Spatial and temporal characteristics of soil erosion in a typical karst basin in southwest China and its response to the landscape pattern of rock desertification

Abstract

Soil erosion is a process of migration and redistribution of soil substances in the landscape, which is regulated by topography, vegetation, human activities and their spatial pattern. At the watershed scale, changes in landscape pattern are important factors in determining the degree of soil erosion. Taking Dabang River Basin as the study area, based on the three phases of land use data, remote sensing image data and daily rainfall data from eight stations in the basin in 2010, 2015 and 2020, the rocky desertification factor (D) was introduced into the general soil loss equation RUSLE to calculate the soil erosion in Karst and non-Karst Areas in 2010, 2015 and 2020 respectively. The relationship between landscape pattern and soil erosion was analyzed from two aspects: type level index and landscape level index. The results showed that: 1) From 2010 to 2020, the average soil erosion modulus in The Dabang River Basin decreased first and then increased. The average soil erosion modulus in the non-karst region was about twice that in the karst region, and the average soil erosion modulus in the karst region decreased first and then increased. The mean soil erosion modulus in the non-karst area showed an increasing trend; 2) Under different slope grades, the erosion was mainly slight and mild, and the area of slight erosion was the largest, and the area of very strong and severe erosion increased as the slope increased. the area of strong, very strong and severe erosion increased in the slope zone below 15°, the area of light and moderate erosion decreased, and the area of slight, strong and very strong erosion increased in the slope zone from 15 to 25°, and the area of slight erosion increased in the slope zone above 25° area increased and light, moderate and strong erosion area decreased in the slope zone above 25°; 3) The landscape pattern of the Dadang River Basin changed significantly from 2010 to 2020. At the landscape level, the number of patches increased and the average patch area decreased. At the type level, the area of paddy field, woodland and shrubland decreases and the area of dry land, grassland, construction land and water body increased, and the dominant land type in the watershed changed from woodland to grassland; 4) The amount of soil erosion was positively correlated with patch type area, landscape percentage, maximum patch index and aggregation index, and positively correlated with edge density; 5) There was a linear relationship between soil erosion and Shannon diversity index (SHDI) and Shannon mean index (SHEI) at landscape level. The results can provide reference for land use planning and soil and water conservation measures.