Vegetation restoration enhances soil erosion resistance through decreasing the net repulsive force between soil particles

Vegetation restoration is a valid way to improve soil erosion resistance by enhancing the stability of soil ag-gregates. Past studies have shown that the net force (the sum of electrostatic, hydration, and van der Waals forces) between soil particles had crucial effects on the stability of soil aggregates. However, little is known about the influence of vegetation restoration on the net force and soil erosion resistance, which hinders our quantitative understanding of this process at the particle to particle level. In this study, to quantitatively analyze the influence of vegetation restoration on soil net force and their relationship with aggregate stability and erosion resistance, we collected soil samples from four different restoration stages (including farmland, grassland, shrubland, and forest), then used Na+-saturated soil aggregates (1 to 5 mm model aggregates) to conduct our experiments. The stability of soil aggregates and erosion resistance were tested through the wet sieving method and rainfall simulation experiments. Our results indicated that the soil net force was repulsive and decreased with vegetation restoration. The stability of soil aggregates and erosion resistance increased with vegetation restoration. With the decrease of electrolyte concentration, the net force and splash erosion rate both first increased (from 1 to 10-2 mol L-1) then remained stable (from 10-2 to 10-4 mol L-1), while the soil aggregate stability first decreased (from 1 to 10-2 mol L-1) then remained stable (from 10-2 to 10-4 mol L-1). The experimental results of soil aggregate stability and splash erosion rate changing with electrolyte concentration could be well explained by soil net force. Moreover, the rate of splash erosion and the stability of soil aggregates showed a significantly negative linear relationship (P < 0.01). Overall, the results indicated that the vegetation restoration process could reduce the net repulsive force of soil particles and thus increase the stability of soil aggregates and erosion resistance. These findings provided quantitative information about the mechanistic understanding of vegetation restoration improving soil erosion resistance.