Regulatory mechanism of soil and water conservation measures on understorey erosion in a subtropical hilly region

Abstract

Vegetation restoration affects soil erosion by altering near soil-surface characteristics and hydrodynamic mechanisms. However, the regulatory mechanisms of vegetation restoration in reducing soil erosion under forests are not fully clear. Five soil and water conservation measures (SWCM) with different vegetation structures and characteristics were used in the pure forest of Pinus massoniana which included the grass and shrub, grass, grass and shrub + level furrow, grass, shrub and trees and grass + fish-scale pits, to analyze the impact of vegetation restoration on near soil-surface characteristics and soil erosion. The data were analyzed using Structural Equation Modeling (SEM) to find the key indicators affecting soil erosion under forest. The findings revealed that, as opposed to the control plots (CK), there were significant alterations in the near soil-surface attribute following the application of SWCM. These changes were characterized by an increase in soil porosity, soil water content, soil nutrient content, root biomass, litter, and vegetation cover, and a decrease in soil compaction, disintegration coefficient, and bulk density, with the most significant improvement occurring in 0–10 cm soil layer. The SWCM significantly reduced soil erosion, with runoff and soil loss reduction ranging from 60.46 % to 74.09 % and 67.62 % to 79.99 %, respectively. Structural equation models revealed the influence of SWCM on soil erosion. Specifically, soil water content and litter had a favourable influence on reducing soil erosion, root biomass had a direct positive impact on soil erosion, and vegetation cover directly leads to a reduction in soil erosion. Soil physical properties primarily influenced soil erosion through their effect on vegetation cover. Combining bioengineering and vegetation measures is superior at enhancing soil structure, improving nutrient content, and decreasing soil erosion compared to single vegetation measures. It is recommended to combine bioengineering with vegetation strategies to effectively curb understory forest erosion and enhance soil quality in pine forests.