The Research On The Evolution Mechanism Of The Karst Land Use System And Optimal Regulation Models

The fragile Karst eco-environment is one of the key factors that hinder the sustainable development in the Southwest China. The increasing attention has been paid to the studies of the Karst land use. Based on the related theories, methods and achievements developed from the sciences of geography, land and system, this paper involved the basic theories and methods concerning Karst land use in terms of structure and pattern, spatio-temporal evolution, driving factors and mechanism, evaluation of sustainable land use and optimal regulation models. Furthermore, applying varied research methods including model method, "3S" technology, grid method and method of artificial neural networks, and collecting the data on Karst land use in Du'an in the 1977,1988,1999 and 2005, this paper carried out a case studies on the evolvement mechanism and optimal regulation models of Karst land use system. The following results were obtained:(1) Bare rock land had the biggest proportion among the structure of Karst land use in Du'an and slope plowland was dominant; concentration indices and efficiency of land use were lower; evolvement of Karst land use system in Du'an showed pattern of up-down-up; the changes of land use was featured with instability and multi-direction.(2) Bare rock land, bush land and slope plowland dominated in the changes of the land use structure of Karst land use in Du'an; more than half of the total areas did not changed, and the rest of land use types changed as follows: forest land was degenerated into bush land, sparse land or grassland; bush land and grassland were degenerated into bare rock land or small and medium bare land in the bare rock land and forest and grassland were developed into plowland; spatial distribution of land use was characterized with bush land being developed into plowland, in particular, small and medium bare land in the bare rock land were conversed into plowland; land use type change in different regions were unparallel and system evolvement fluctuated.(3) Karst land degeneration in Du'an resulted from drastic contradiction between human and land. Land degeneration exacerbated and its spatial distribution extended from downtown to east and west. Change of spatial distribution showed pattern of extension, reversion and stabilization.(4) Karst land use system in Du'an was sensitive to precipitation, lithology, soil, physiognomy, sea level and slope. The important driving forces for the evolvement of Karst land use were population, economy, income of peasant, advancement of agricultural science and technology, policy and regulation and consumption structure of energy. External driving force posed the most intensive impact on the change of plowland areas, but rather lower on bare rock land.(5) Sustainability assessment of Karst land use were divided into 5 grades: unsustainability, low sustainability, moderate sustainability, relatively strong sustainability and strong sustainability. Five optimal regulation models were developed as followes: fruit-medicine cultivation and water and land efficiency cropping, forest reservation paralell to stock raising, mixed agriculture and forest management, high efficiency ecological agriculture in hill and valley, reallocation.