Land use evaluation and scenario analysis towards sustainable planning on the Loess Plateau in China - case study in a small catchment

摘要

The Loess Plateau has been suffering from serious soil erosion for a long time, which originated in a population growth about 2000 years ago. After then, the rapid increase in human activity has led to more areas became used for grain production. Original vegetation has been destroyed and soil erosion has become more and more serious. Most research works indicate that the soil erosion on the Loess Plateau is mainly induced by irrational land use structure and low vegetation coverage. Controlling soil erosion is a significant factor in making a sustainable land use planning for the Loess Plateau. In this study, a procedure towards such a planning is presented, based on results from a research project in a small catchment on the Loess Plateau. A land suitability evaluation for rain-fed agriculture based on biophysical parameters, and a comparison between land suitability and current land use, were first carried out. Some potential land use scenarios, based on surveys on biophysical and socio-economic parameters in the catchment, and plans by the authorities, were proposed for further evaluation of their effects on soil erosion, economic feasibility and social acceptance. The scenarios were tested by (i) simulation modeling, to show the differences in erosion, and (ii) from studies on the influence of the scenarios on farmers' economy and their response. The results indicated that the following land use scenario was acceptable: all land with deep soil and slopes smaller than 15degrees is used for agriculture cropland, possibly combined with biological conservation measures, such as mulching combined with improved fallow, and all land with steeper slopes than 15degrees is used for other purposes (orchards and other cash trees, woodland, shrubland, grassland). A great reduction of on-farm income, however, would be induced on the short term by such a scenario. Local farmers will find it difficult to accept it unless financial support from external sources is available. On the long term, the scenario will be promising for both economic income improvement and soil erosion control since some production will be obtained from the conversion of cropland into orchards/cash trees (preferably on slopes 15-25degrees). Thus the land use modification should be carried out gradually. On the short term (5 year), it is suggested that cropland on steeper slopes than 25degrees is returned to woodland/shrubland/grassland while also fruit trees are planted on slopes 15-25degrees. Within 10 years, cropland with slopes steeper than 15degrees is suggested to be converted into orchard/woodland/shrubland/grassland