Effect of Land Use on Soil Degradation in Alpine Grassland Soil, China

Grassland soils in Northern China are being seriously degraded under cultivation and grazing. This study investigated the impacts of land use on soil erosion and soil fertility in alpine grassland of China. Land uses included three levels of pasture degradation, lightly (LDP), moderately (MDP), and heavily degraded pasture (HDP) classified based on vegetation cover, and cultivated fields ranging from 1 to 50 yr of cultivation. Soil samples were collected from 18 sites at seven locations in Chernozemic soils between elevations of 2600 to 3000 m. Soil erosion was estimated by 137 Cs radioactivity. When pasture was heavily degraded, 137 Cs activity was significantly reduced, and organic C (OC), total N, and cation-exchange capacity declined by 33, 28, and 18% respectively. Cultivation of grassland worsened soil erosion, and after 8-, 16-, and 41-yr cultivation soil OC decreased by 25, 39, and 55%, respectively. Regionally, 59% of OC was lost within 30 to 50 yr of cultivation. There were concomitant losses of total N and exchange capacity. On cultivated soils, soil erosion and mineralization were equally responsible for organic C losses. Pasture degradation and cultivation also caused changes in soil P. Mineralization of organic P, incorporation of subsoil by tillage following erosion, and fertilization increased levels of Ca-P in cultivated fields. This study indicated that grassland degradation and cultivation caused not only severe soil erosion, but also fertility decline and chemical changes of P dynamics.

[1]  M. Oliver,et al.  The utility of 137Cs for measuring soil redistribution rates in southwest Niger , 1998 .

[2]  Im Neuenheimer Feld,et al.  AN EVALUATION OF SOIL CONSERVATION TECHNIQUES IN THE ECUADORIAN ANDES , 1995 .

[3]  R. W. Sheard,et al.  Comparison of Conventional and Automated Procedures for Nitrogen, Phosphorus, and Potassium Analysis of Plant Material Using a Single Digestion1 , 1967 .

[4]  H. Dregne.  Soil erosion: cause and effect , 1987 .

[5]  D. Walling,et al.  The use of caesium-137 measurements to establish a sediment budget for the Start catchment, Devon, UK , 1997 .

[6]  E. Jong,et al.  Predicting the Temporal Relationship between Soil Cesium‐137 and Erosion Rate , 1984 .

[7]  E. Jong,et al.  PRELIMINARY INVESTIGATIONS ON THE USE OF 137Cs TO ESTIMATE EROSION IN SASKATCHEWAN , 1982 .

[8]  R. Protz,et al.  Distribution of natural radionuclides and 137Cs in soils of southwestern Ontario , 1999 .

[9]  E. Jong,et al.  The importance of erosion in the carbon balance of prairie soils , 1988 .

[10]  L. Vilela,et al.  Chemical fractionation of phosphorus, sulphur, and molybdenum in Brazilian savannah Oxisols under different land use , 2000 .

[11]  G. Cozzi,et al.  Avoidance of degradation of alpine pasture through grazing management: Investigations of change in vegetation nutrition characteristics as a consequence of sheep grazing at different periods of the growing season , 1993 .

[12]  K. Hall,et al.  Animals as Erosion Agents in the Alpine Zone: Some Data and Observations from Canada, Lesotho, and Tibet , 1999 .

[13]  R. Kachanoski.  Estimating soil loss from changes in soil cesium-137 , 1993 .

[14]  I. Salcedo,et al.  Nutrient and soil organic matter dynamics under shifting cultivation in semi-arid northeastern Brazil , 1992 .