Rainfall amount shapes the soil erosion and vegetation protection effectiveness in soil conservation

Rainfall is a primary driving force of soil and water loss. However, the impacts of increasing rainfall amount (RA) on slope soil erosion are obscure, calling for a detailed integrated assessment. In particular, the relationship between dynamic RA and vegetation protection effectiveness remains poorly understood. Therefore, this study conducted a meta-analysis of 40 studies, representing 1,630 rainfall events and the associated runoff (R) and soil loss (S), collected from runoff plots across various regions of China up to the year 2023. Among these, 68.59% of the rainfall events occurred in the northern rocky mountainous region and the Loess Plateau, while 72.58% were recorded on Semi-alfisols and Amorphic soil. The runoff plots included grassland, shrubland, forest, and bare land, with RA ranging from light rain to downpours. The results indicated that increasing RA significantly promoted soil erosion and increased the slope erosion sensitivity. The weighted average runoff (WR) and the weighted average soil loss (WS) produced by downpours reached 12.06 and 11.16 times those produced by light to moderate rain, respectively. The weighted average runoff coefficient (WRC) increased from 0.24 to 0.41 as RA rose, while the weighted average sediment coefficient (WSC) from torrential rain to downpours was higher than from light to heavy rain. The vegetation protection effectiveness was influenced by both vegetation type and RA. Vegetation was more effective in controlling S than R. The effectiveness of vegetation in reducing runoff declined with increasing RA. Its ability to reduce erosion initially decreased and then increased dfrom light to torrential rain. Forest significantly reduced soil erosion and inhibited the linear relationship between ‘ln(RA)-ln(R)-ln(S)’. Additionally, this study presents a rainfall event classification based on soil loss tolerance and emphasizes that vegetation protection effectiveness is not equivalent to soil loss tolerance, thereby providing scientific support for regional soil and water conservation.