Time-sensitive effects of vegetation restoration on slowing down soil erosion: Evidence from Northeastern China with Mollisols

• Nonlinear variation of soil erodibility along a black soil erosion time series. • The extent and manner to which plant roots reduce soil erodibility varies as soil erosion continues. • Threshold effect of soil erodibility and vegetation restoration effectiveness was found as soil erosion increases. • Seasonal freeze–thaw also contribute to the time-sensitive effects of vegetation restoration. The loss of fertile topsoil caused by erosion leads to the relative change of soil profile configuration, which consequently leads to a series of changes in soil properties. These changes will theoretically affect vegetation restoration efficiency, resulting in a threshold effect of soil erodibility and vegetation restoration effects as soil erosion continues. In this study, we simulated the decrease of the topsoil layer caused by erosion (that is, the thickness of the black soil layer was 30 cm, 20 cm, 10 cm, and 0 cm in order) by filling pots with different proportions of black soil and deposition layer soil to represent the time series of soil erosion: no erosion, mild erosion, moderate erosion and severe erosion. The soil disintegration characteristics in the time series of black soil erosion with and without vegetation ( Bromus inermis ) were compared, and the response of this process to seasonal freeze–thaw was further considered. We found that in the absence of vegetation, the disintegration rate was the highest at moderate erosion with the intensification of black soil erosion. That is, moderately eroded black soils had an even higher soil erodibility than severely eroded black soils. Vegetation can significantly reduce soil disintegration rates and enhance soil resistance to seasonal freeze–thaw, this is highly dependent on the combined effects of soil stratification and subsequent root characteristics. Our findings revealed that both soil erodibility and vegetation restoration efficiency of degraded stratified soil have threshold effects as soil erosion degree increases. In other words, the effects of vegetation restoration on preventing soil erosion are time-sensitive. Moreover, seasonal freeze–thaw can also affect soil erodibility and vegetation restoration efficiency by changing soil properties and root characteristics. These findings may help determine effective vegetation restoration strategies in areas with similar soil types, profiles, and bioclimatic characteristics to the black soil areas.