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

Because of specific rock and soil composition and texture in the karst superficial zone, water 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 500(t/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.