Effects of Vegetation Restoration on Soil Physical Properties in the Wind-Water Erosion Region of the Northern Loess Plateau of China

In the northern Loess Plateau that has been severely affected by windwater erosion, shifts from arable land to forest or grasslands have been promoted since 1998, using both native and introduced vegetation. However, there is little knowledge of the ecological consequences and effectiveness of the vegetation restoration in the region. Therefore, relationships between watershed-scale soil physical properties and plant recovery processes were analyzed. The results show that soil physical properties such as bulk density, hydraulic conductivity, mean weight diameter, and the stability of >1?mm macro-aggregates have been significantly ameliorated in the 020?cm soil layer under secondary natural grasslands. In contrast, re-vegetation with introduced species such as Caragana korshinskii or Medicago sativa had adversely affected the soil physical properties, probably due to the deterioration of soil water conditions and lower organic matter inputs resulting from severe erosion. Reductions in bulk density and increases in saturated hydraulic conductivity could be used as indicators of soil structure amelioration since they are closely related to most other measured properties. Practical considerations for future re-vegetation projects are suggested, particularly that native species with lower water consumption rates than the introduced species should be used to avoid further soil degradation.