Anti-soil erodibility of different land use types in Northwest Guangxi Karst Regions

Anti-soil erosion index is critical for analyzing soil erosion. In this paper, 7 indices (including soil organic matter, water stable aggregate, structural damage rate, re-aggregation situation/degree, dispersion rate and <0.05 mm silt/clay content) were selected to analyze anti-soil erosion degrees of 5 different land use types via both ANOVA and principal component methods in Northwest Guangxi karst regions. The results showed that soil organic matter contents in original and secondary forestlands were significantly higher (P < 0.05) than those in fallow lands, slope farmlands and artificial forestlands. Fallow lands had higher but insignificant soil organic matter content than slope farmlands and artificial forestlands. Amounts of soil >0.25 mm water stable aggregates and re-aggregation situation/degree in original forestlands, secondary forestlands and fallow lands were significantly higher than those in slope farmlands and artificial forestlands. However, slope farmlands had significantly higher structural damage rate and dispersion rate than other land use types. Structural damage rate of artificial forestlands was significantly higher than that of secondary forestlands, but similar to those of original forestlands, fallow lands and slope farmlands. Dispersion rate of artificial forestlands was similar to that of slope farmlands, but significantly lower than those of original forestlands, secondary forestlands and fallow lands. Re-aggregation degrees of original and secondary forestlands were similar to those of fallow lands and slope farmlands, but significant higher than that of artificial forestlands. The <0.05 mm silt/clay contents of secondary forestlands, fallow lands and artificial forestlands were similar to those of original forestlands and farmlands. However, original forestlands had a significantly lower <0.05 mm silt/clay content than slope farmlands. The order of anti-soil erosion degree of 5 land use types obtained by principal component analysis was: original forestland > secondary forestland > fallow land > slope farmland > artificial forestland. It was therefore concluded that human disturbances in karst regions severely weakened soil anti-erodibility, which could be improved by leaving farmlands to fallow.