Study On Karst Rocky Desertification Forming Process And Its Control Technology

Guizhou province is the distributive center of karst in China. Rocky desertification caused by long-term disturbance, became a powerful obstacle of economic development and local people's survival, and is being a research hotspot now. As a whole, basic researches on rocky desertification were lack, especially in forming process, classification and degree estimated, and with some misunderstandings. This study started from analysis of cause and driving forces, through a great amounts of samples investigation, adopted a method of time replaced by space using samples at differ places constituted a serial time sequence to study the type, forming and evaluation This study defined a whole conception for rocky desertification and considered that rocky desertification was same as the sandy desertification, both belong the category of desertification, its essential change was the degradation of productivity. The exiting district, character, reason and essential of rocky desertification were as well defined. Rocky desertification land is a multiple system composed by nature and economic society. Disturbance from outer system —human society, was essential reason to form rocky desertification which was a result of the action of human disturbance to natural environment. When human disturbance exceeded a self-regulation threshold of karst nature system, resulted in land system gradually degraded, usable resources reduced and eco-environment worsen, consequently it increased the degree and size of disturbance and degradation of environment. It is a positive feedback cycle relation between two sub-systems that affected each other. The serious contradiction between resource and human that population density exceeded the carrying capacity of land and low productivity due to poor economy was the main source of human disturbance. Rain energy and gravitational potential energy were original energies of rocky desertification form in nature ecosystem, and were direct or primary motivity. The properties in each element of the ecosystem played a role on stimulating, accelerating and overlapping or restraining, lessening erosion of soil and water, its essential was the enhanced or weakened intensity of motivity from a kinetic viewpoint. Human disturbance and societal economic activity etc. were indirect or second motivity to forming rocky desertification, which essential was the change intensity of motivity to achieve enhance or stimulation of the direct motivity, which result in lessening effect of inhibitory or buffer action to nature ecosystem and to accelerate the process of rocky desertification. But human positive disturbance such as restoration of vegetation or control engineering could play an opposite role as before. Rocky desertification could be classified two types that were apparent and recessive types based on its lithology. Apparent rocky desertification developed from pure limestone, dolomitic limestone or limy dolomite that have more rate of rocky exposedness, complex and various micro-site, thin and fragmentary soil. The properties of recessive rocky desertification that there are characterized by the content of stone, simplex site, thin but continuant soil covered, low or even not rocky exposedness. There are obviously differences in topography, physiognomy, hydrology, site, and vegetation restoration between the both types, which come from difference of rocky dissolved process because of different rocky components. The forming process of rocky desertification was a degraded process of land productivity, which principal expressive form was the vegetation degradation. By comparing with undegraded land and analysing the changes of biomass and vegetation properties, 4 stages have divided they are initial, medium, last and end stage. In the process, community biomass, coverage and height had reduced, plants developed to xenophile, soil dry bulk and stickiness increased, soil structure worsened, soil aeration decreased, soil organic matter and nutrient loss and leached seriously, and productivity decreased. The environment developed from demulcent medium degree to droughty direction with high temperature, low moisture, windy with great, changes greatly and disadvantageous site for plants growing. The estimation of rocky desertification degree is the precondition of vegetation restored and eco-system rebuilt. Surrounding the center of land productivity degradation, estimated index system had been calculated, using a hierarchy analysis to balance indexes and compared different sizes between rocky desertification land and undegraded land, namely using Euclidean distance from original stage to degraded stage of rocky desertification. The far distance, the more degraded degree. The light, medium, strong and ultra strong 4 grades of degree based on size of rocky desertification index were graded, and the relationship of rocky desertification degree with differ disturbance types were studied. Based on the above researches, this paper suggested that rocky desertification prevention and control should be classified and planned as a whole based on system theory and in a small drainage area unit. The rocky desertification land is a coupling system constituted by human society and nature environment. Taking measures to protect existing environment and promoted restoration of natural vegetation and ecosystem rebuilding is one side of rocky desertification prevention and control. Combining with adjusted of industrial structure and energy resource innovation, improving land productivity, developing economy; reducing or eliminating sources of disturbance is the other side. It should be made a crossed system at time and space and putting in practice at the same time. Cooperating with correlative engineering projects of state to solve the question of financing shortage. The prevention and control patterns, for different degrees of rocky desertification, objects and direction of land using were summarized, which possess an important referring value to prevent and control of rocky desertification.