The Nature Settings And Their Diversity In Different Regions In The Progressing Of Rocky Desertification In Guizhou Karst Area

Guizhou province is located in the center of a widespread karst region in southwest of China, which is the largest one in the world. The province is undergoing the process of rocky desertification, which is apparent and deteriorating in recent years, and furthermore becomes an obstacle to the development of local economy and improvement of local citizen's living standards. It is well known that detailed study on the mechanism of rocky desertification lays the bases to harness it, however, the present study is mainly focused on qualitative study and is obviously lacking in quantitative and spatial one. Due to the various physiognomy in this province, the extent and leading factors of rocky desertification are different from one district to another, and the differences should be taken into consideration when dealt with rocky desertification related problems.This paper studied various effect factors including lithology, types of physiognomy, gradient, precipitation and soil type, in rocky desertification process in Guizhou by using geographic information systems (GIS) as an instrument. Detailed analysis is made by spatially superimposing above-mentioned factors as a layer onto the map of rocky desertification within the GIS method, further analysis also made on the spatial distribution of those factors and main driving forces in different districts. The following conclusions are drawn from the analysis.I .The correlation of rocky desertification and lithology is obvious in reason that lithology in the karst region is mainly of limestone and the extent of desertification is higher than that of dolomite. Rocky desertification occurred more frequently in limestone-continuously-distributed area than that of others, and mostly in moderate and severe degree; this is also true to dolomite-continuously-distributed area. It can be drawn that usually pure carbonate lays bases for the occurrence of rocky desertification.II. The incised depth of physiognomy has made a great impact on the progressing of rocky desertification, which is a conclusion from the analysis of the correlation between physiognomy types and the extent of desertification. The deeper the physiognomy is incised, the more frequently desertification occurs; the more the relative height is, the more serious impact of incised depth on the desertification is made. Therefore, the highest possibility of the occurrence of rocky desertification is in those areas combined of conic hills and depressions. As to the impact of gradient onrock desertification, it is evident that when the gradient of a slope is bigger than 25 degree, the occurrence possibilities of the desertification at low or moderate or strong intensity are all very high. Meanwhile, it is mainly at low or moderate intensity when the gradient is smaller than 18 degree. The precipitation of an area also plays a role in rocky desertification, especially when it is more than 1200mm. Over that amount, the more the precipitation there is, the more severe desertification there will be. The intensity is mainly low or moderate when the amount is less than 1100mm. The rocky desertification of three levels of intensity is most likely to occur in rocky soil and limestone soil among all different soil types, while the low or moderate intensity ones occur in yellow soil and regosol. The moderate or severe rocky desertification is also very likely to occur in yellow-blown soil; at the same time, the occurrence possibility of moderate desertification in the area with alpine meadow soil is high.III. When analyzed the main leading forces in the progress of rocky desertification in different types of physiognomy in karst regions, it can be concluded that the formation of rocky desertification is based on the fragile geological environments, which are intensively disturbed by human activities. On the one hand, a large-scale continuously distributed carbonate is dominant in the progress of desertification, which also decides the soil depth and distribution of soil type; on the other hand, the gravity p...