Effects of vegetation restoration on soil properties along an elevation gradient in the karst region of southwest China

Abstract

Vegetation restoration effectively prevents soil degradation. However, the changes in soil properties that occur in fragile ecosystems in response to vegetation restoration are unclear. The aim of this study was to investigate the effects of vegetation restoration on soil physicochemical properties and saturated hydraulic conductivity (Ks) at different elevations. Restoration strategies included natural shrubland (NR), managed plantation forest (PF), cropland (CR), and secondary forest (SF). Topsoil (0–15 cm) samples were collected from seven counties in the karst region of southwest China. The soil nutrients were significantly (p < 0.05) higher in both NR and PF than in CR but were lower in SF. Soil physical properties (bulk density, porosity, texture, and Ks) were significantly (p < 0.05) different between CR and SF but not significantly different between NR and PF. Hence, the short restoration period (~15 years) had a stronger influence on soil nutrients than on soil physical properties. The soil properties following different land-use types were affected by elevation. For SF and PF, soil Ca, total nitrogen, and sand content were significantly (p < 0.05) negatively correlated with elevation. For NR, only sand content was significantly (p < 0.05) negatively correlated with elevation. No soil parameters were significantly correlated with elevation in CR. Soil nutrients increased to a greater extent in the low-elevation area (150–500 m) than in the high-elevation (1000 to 1200 m) areas. This discrepancy could be explained by the relatively increased biomass after vegetation restoration. Clay content variation was the main factor controlling Ks variation. The change in clay content was greater in low-elevation areas than in higher-elevation areas, where higher weathering and erosion rates were caused by strong hydrothermal conditions. Accordingly, the present study showed that the variations in soil properties observed after vegetation restoration are influenced by both land-use types and elevation.