以小流域为单元 ,根据山地防护林体系配置的特点 ,采取定位和半定位研究方法 ,分层次对山地防护林体系蓄水保土功能进行监测分析。研究结果表明 :不同地类及用地方式 ,不同森林类型保持水土效益差异较大 ,在滇中高原 ,裸地和坡耕地是流域产沙的主要来源 ,农耕地侵蚀量是林地的 18.7～ 36 .0倍 ,裸地侵蚀量远大于坡耕地 ,高达林地的 10 0倍左右 ;营建防护林体系后 ,防护效益显著 ,土壤侵蚀模数随森林覆盖率的增加而减少 ,流域森林覆盖率由 18.6 %上升到 42 .4%时 ,土壤侵蚀模数减少 36 % ;坡地造林后 ,地表径流减少 79.44 %～ 96 .9% ,泥沙削减 87.8%～ 99.9% ;要使山地小流域水土流失得以控制 ,森林覆盖率必须达到 30 %以上 Taking the small watershed as a unit, according to the characteristics of the mountain shelterbelt system configuration, the research methods of location and semi-location were adopted to monitor and analyze the function of water and soil conservation of mountain shelterbelt system. The results showed that different types of land and land use, different types of forests to maintain water and soil benefits vary greatly, in the Central Yunnan Plateau, bare land and slope farmland is the main source of sediment yield, agricultural land erosion is 18.7 to 36. 0 times the amount of erosion on the bare land is much larger than that of sloping farmland and up to about 100 times as high as that of the forest land. After building a shelterbelt system, the protective efficiency is significant, and the modulus of soil erosion decreases with the increase of the forest coverage, and the forest coverage of the watershed rises from 18.6% By 42.4%, the modulus of soil erosion decreased by 36%. After afforestation on the slope, the surface runoff decreased by 79.44% -96.9% and the sediment reduction by 87.8% -99.9%. To control the soil erosion in the mountainous small watershed, the forest Coverage must be above 30%