黄土高原退耕还林工程中的现存问题及有关建议

花岗岩母质土壤区在洞庭湖流域广泛分布。由于内在机理及洞庭湖流域特殊的气候条件和人地关系状况，使这一类土壤区成为洞庭湖流域最为严重的水土流失地区之一，并引起了严重的环境、社会、经济后果。花岗岩分布区地形陡峭、风化速度快，风化层深厚，极易导致水土流失。在内生动力和外部动力的共同作用下．水土流失的时序特征与风化层各层的特性紧密相关。为了科学治理，首次尝试对湿润区花岗岩水土流失区进行区域界定并作了类型区划分。

Existing Problems and Suggestions on Program for Conversion of Farmland to Forestland or Grassland in Loess Plateau

A granite based soil region is distributed widely in the drainage area of Dongting Lake. Intrinsic characteristics of granite, special weather conditions and the relationship between humans and land in the Dongting Lake drainage area make this soil region one of the most seriously affected by soil erosion and causes very bad environmental, social and economical results. In the granite area, topography is steep, weathering is rapid, the layer of weathering is very deep and the soil is very easily eroded away. With inherent and external erosion forces acting together, it is possible to relate a time sequence to the features of every weathering layer. On the basis of observations to the granite bedrock, the authors indicate the soil erosion region in different areas, suggest the time sequence characteristics of soil erosion and reveal the temporal and spatial differences between soil erosion occurrences. To manage the extent of the study, the authors first try to classify the regional differences in granite soil erosion within wetter areas.