干旱区生态环境知识资源中心

Heavy grazing is recognized as one of the main causes of vegetation and soil degradation and desertification in the semiarid Horqin sandy grassland of northern China. Soil physical and chemical properties were examined under continuous grazing and exclusion of livestock for 8 years in a representative desertified sandy grassland. Exclosure increased the mean soil organic C, total N, fine sand and silt + clay contents, inorganic C (CaCO(3)), electrical conductivity, and mineral contents (including Al(2)O(3), K(2)O, Na(2)O, Fe(2)O(3), CaO, MgO, TiO(2), MnO), microelements (Fe, Mn, Zn, B, Cu, Mo), and heavy metals (Pb, Cr, Ni, As, Hg, Cd, Se), and decreased the coarse sand content, bulk density, and SiO(2) in the top 100 cm of the soil. Livestock exclusion also improved available N, P, K, Fe, Mn, and Cu, exchangeable K(+), and the cation exchange capacity, but decreased pH, exchangeable Na(+), and available S, Zn, and Mo in the top 20 cm of the soil. The greatest change in soil properties was observed in the topsoil. The results confirm that the desertified grassland is recovering after removal of the livestock disturbance, but that recovery is a slow process.