西南喀斯特山地水土流失特点及有关石漠化的几个科学问题

Characteristics of water loss and soil erosion and some scientific problems on karst rocky desertification in Southwest China karst area

由于特殊的岩土组构,喀斯特坡地的水土流失具有如下特点：地表和地下流失相互叠加;地表产流、产沙少;纯碳酸盐岩区地下流失比例大。论文区别了石漠化和石质化的科学内涵,指出了喀斯特山地石漠化的核心是土地的石质化,提出了按照地面物质组成与裸岩率叠加的石漠化分类系统。根据土壤中硅酸盐矿物的物质平衡,提出了不同碎屑岩含量碳酸盐岩区的土壤允许流失量介于5%~500 t/（km2.a）之间。喀斯特坡地土壤虽然肥沃,但总量太少,矿质养分不足可能是石质坡地植物生产力低的重要原因。此外,根据农耕驱动土地石质化的机制,提出了相应的石漠化治理对策建议,具体是：（1）不但要治标,提高植被覆盖率,更要治本,防止或减缓土地石质化,同时还要增加群众收入;（2）按照坡地岩土组成的垂直分带特点,因地（土）制宜,开展治理;（3）重视矿质肥料的施用;（4）在纯碳酸盐岩土石质和石质坡地农田的小型蓄水工程修建中,要加强集流面建设。

Because of specific rock and soil composition and texture in the karst superficial zone,warter loss and soil erosion on slopes in karst area is of the following characteristics：（1） superimposition of soil loss on the ground surface and under the ground;（2） limited ground surface runoff and sediment yields;and（3） higher sediment contribution from underground soil loss.This paper distinguishes scientific concept of karst land desertification and karst land rockification,points out that the rockification being the core of karst land desertification,and proposes a superimposed classification system for karst land desertification. The soil loss tolerances are mainly controlled by the proportion of clastic rocks and range between 5t/（km2.a） and 500t/（km2.a）,which are derived from silicate mineral budgets in soils.The soils are fertile,but the land is poor because of limited soil body amount on rocky slopes;and the low plant productivities are probably caused by the shortage of mineral nutrient supply.According to the mechanism of karst land rockification being driven by the stress of cultivation,following countermeasures against karst land desertification are suggested：（1） not only improving vegetation to cure the symptoms,but also preventing or mitigating land rockification to cure the basic cause and increasing farmers＇ incomes;（2）countermeasures against karst land desertification should be suit to the vertical zoning conditions of rock and soil compositions in karst mountains;（3） paying more attention to application of mineral fertilizers;and（4） using the surfaces of field roads and paths as water harvesting catchments to collect runoff for micro water storage tanks on cultivated rocky or stony land.