三峡库区坡地植被─土壤环境变化及土地利用的研究

Study on the Slope Vegetation-SoiI Environmental Change in Shanxia Reservoir Area and Its Land Utilization

三峡库区现有坡地植被是由亚热带常绿阔叶林演替而来的天然次生林和荒地草坡及人工林植被。森林覆盖率从２０世纪４０年代的４５．５％降至１９８５年的２１．７％，而且面积分布不均匀呈“岛状”和“斑块状”。坡地植被的退化导致了土壤瘠薄。土壤石砾含量６％～３０％；土层较薄４０～６０ｃｍ；土壤母质松软再加之人们不合理利用土地，使水土流失加剧。为了控制库区坡地植被─土壤环境变化，防止进一步土壤侵蚀，１９９２年采用生物活篱笆复合农林经营技术。生物活篱笆是采用速生、萌生力强、能固Ｎ的植物材料沿等高线种植，使较陡坡地保持水土达到合理利用土地的目的。试验选择刺槐、黄荆、马桑、新银合欢、紫穗槐、龙须草、香根草等乔灌草。种植３ａ后植被覆盖达３５％，产沙量３．３ｇ／ｍ２，而人为翻耕没有植被覆盖的产沙量高达３７．９７ｇ／ｍ２。

The slope vegetation succession in Shanxia Reservoir Area has been changedfrom the subtropical evergreen forest to the natural coppice forest,barren herb slope andplantations. Its forest coverage decreased from 45.5%in 1940 to 21.7%in 1985 and theforests distributed unevenly,shaping like island,speckles and blocks. The deterioration ofthe slope vegetation led to the unfertile soil characteristics :content of stone particles in thesoil is 6%～30%;thickness of soil layer 40～60 cm;texture of soil soft.During·the heavyraining season (April～ October),soil erosion is serious. Besides,the irrational land ex-ploitation in this area intensified the soil erosion. To bring the change of the slope vegetationand environment under control,the technology of planting bio-living-fence and agroforestrywas adopted.The method is using the tree species,which are fast-growing,easy-sproutingand good at fixing N for contour line planting to prevent the slope from further erosion. Theplant species selected are : Robinia pseudoacacia,Vitex negundo,Coriaria sinica,Leucacenaleucocephala,Amorpha fruticasa,Vetiveria nigritana,Carex spp.,arbor,shrub and herbspecies. 3 years after the cultivation he forest coverage increased to 35%and the content ofmud and sand in the running water from the slope was 3.3g/m2,while that on the landwithout vegetation was 37.97 g/m2.