Soil erosion is one of the common forms of land degradation worldwide. Over the past decades, a series of ecological restoration programs have been conducted to reduce soil erosion, prevent water pollution and restore riparian ecosystems worldwide. In these projects, large areas of uncultivated land and slope farmland were converted to shrubland, woodland or terrace, and forming a particular landscape configuration on different geographic location. The changed habitats have significant impacts on regional hydrologic cycle and soil delivery process. 

 However, the relationship between changed habitats and soil susceptibility to erosion were not yet fully understood. The spatial variation of soil erodibility factor (K) at watershed scale and its relationship with controlling factor, especially factors associated with long-term restoration, are still uncertain, which restricts the understanding of soil erosion mechanisms.  

JIANG Qinghu, under the guidance of Prof. LIU Feng from Wuhan Botanical Garden, conducted a systematic survey in a representative ecological rehabilitated watershed, and then quantified the spatial variation of K and its relationship with potential impact factors.  

This study found that the K values were the highest in the mid-stream region in the watershed, decreased in the downstream regions, and were the lowest in the upstream regions. No obvious patterns were observed in the distributions of K with respect to the slop in either soil layers. Among the four land use types, the K values of land use types changed with the order of shrubland > terrace and slope farm land > woodland.  

The variation in soil erodibility was closely related to soil texture and soil organic matter (SOM). The external environment variables (spatial location, topography and plant coverage) could indirectly affect K mainly by changing the SOM content. Therefore, ecological restoration measures and ongoing changes in land use could significantly affect the physical and chemical soil properties thereby affecting K. 

These results indicated that in this type of restored watersheds more endeavor should be paid to expand forest coverage, to increase soil organic fertility, and to weaken plowing, which will help in spatial planning and optimizing ecological rehabilitation measures at watershed scale. 

Results were published in Science of The Total Environment entitled “Spatial pattern of soil erodibility factor (K) as affected by ecological restoration in a typical degraded watershed of central China”. This study was funded by the Natural Science Foundation of China and the Chinese National Key Development Program for Basic Research.  

Structural equation model assessing the effects of the spatial variables (WL and SP) and other environmental variables (plant, Topo, ST, and SOM) on K (a, the surface soil; b, the sub-surface soil) (Image by WBG)