Effects of Near Soil Surface Characteristics on the Soil Detachment Process in a Chronological Series of Vegetation Restoration

The effects of near soil surface characteristics on the soil detachment process might be different at different stages of vegetation restoration. This study was performed to investigate the effects of near soil surface factors on the soil detachment process by overland flow. Soil samples were collected from two natural grasslands of different ages and subjected to flow scouring. The results indicated that the effects of near soil surface characteristics on soil detachment were substantial during vegetation restoration. The total reduction in soil detachment capacity of the 1-yr-old grassland was 98.1%, and of this total, 7.9, 30.0, and 60.2% was attributed to the litter, biological soil crusts (BSCs), and plant roots, respectively. In the 24-yr-old grassland, the soil detachment capacity decreased by 99.0%, of which 13.2, 23.5, and 62.3% were due to litter, BSCs, and plant roots, respectively. Combined with previously published data for a 7-yr-old grassland, the influence of plant litter on soil detachment was demonstrated to increase with restoration time, but soil detachment was also affected by the litter type and composition. The role of BSCs was greater than that of plant litter during the early stages of vegetation recovery. However, its contribution weakened with time. The influence of plant roots accounted for half to two-thirds of the total near soil surface factors, of which >72.6% was attributed to the physical binding effects of roots. The correction coefficients of near soil surface characteristics for rill erodibility were determined for the Water Erosion Prediction Project model.