Distribution characteristics of rural settlement on different lithology in karst area：A case study of Pingguo City

Located in Baise City， Guangxi Zhuang Autonomous Region， Pingguo City has high terrain in the north and low terrain in the south， with low mountains and hills in the north and south， and karst landform in the middle.The karst landform area of the city accounts for 61.67% of the total area， which is a typical karst landform area. The whole area belongs to the south subtropical monsoon climate zone， with a total area of 2，458 km2， with 9 towns and 3 townships under its jurisdiction. In 2018， the total population of its jurisdiction was 520，412， and the GDP was 17.653 billion yuan. The total area of rural settlements in the city is 4，825.15 hm2，the area of rural settlements in karst area is 3，564.20 hm2 ， and the area of non-karst area is 1，260.95 hm2. In this study，GIS spatial analysis，CV value analysis of Voronoi figure，landscape pattern index analysis including patch number，total patch area，patch area ratio，patch density，average patch area and average shape index are used to explore the spatial distribution characteristics of rural settlements on different lithologies in the study area from the aspects of aggregation degree and morphology. The distribution characteristics of rural settlements in karst and non-karst areas were compared and analyzed in this paper， as well as the distribution characteristics of rural settlements with different lithologies in villages and towns.The data processing and analysis of rural settlements areas under different lithology in different townships can effectively eliminate the influence of other factors such as terrain and landform， and location conditions. The results show that，（1）The rural settlements in the karst area are complex and irregular in Pingguo City， and the aggregation degree is lower than that in the non-karst area；（2） Rural settlements on the same lithology show similar distribution characteristics in different villages and towns；（3） CV results show that the aggregation degree of rural settlements in limestone and limestone with dolomite is highest；（4）Landscape pattern index analysis show that the morphology of rural settlement is complex in the two lithology types of carbonate rocks with clastic rocks and carbonate rocks interbedding with clastic rocks.This study explores and analyzes the spatial distribution of rural settlements on different lithologies in karst area，and to a certain extent promote the study of rural settlements in the karst area. However， there are still many shortcomings and further research content needs to be done. Future research can analyze the driving force of rural settlements change more accurately by analyzing the evolution trends of rural settlements on different lithologies， and further explore the distribution law of rural settlements in karst areas more deeply by introducing new research methods.