Abstract:

Land degradation has been quickly expanding in Hechi Region of northwestern Guangxi Zhuang Autonomous Region and results in the decreases of farmland and the limitation of agricultural development.Based on the Landsat TM remote sensing images and DEM data，and combined with socioeconomic statistical data，spatialtemporal analysis and logistic regression model were employed to quantify the spatial and temporal changes of farmland and study its driving mechanism from 1952 to 2006 in 11 counties of Hechi，northwestern Guangxi.The spatial analysis indicated that the changes of total farmland areas had experienced four stages from 1952 to 2006：Rapid increase，fluctuant change，rapid decrease，and slow decrease.The spatial change rates were unbalanced as the farmland of the west part sharply decreased in latest 20 years，which was due to the dominant driving forces of policy effects.According to the results of Logistic regression，we extracted 7 explanatory variables associated with effects on the farmland distribution.The logistic regression models analysis of driving mechanism showed that altitude and population distribution were the most important driving forces，and then followed by slopeⅠ (0~5°)，GDP，distance to main roads，distance to main towns.The explanatory variable of main driving force and the sensitivity of explanatory variable to farmland distribution probability were different from each county.The altitude，slopeⅠ(0~5°)，and GDP were more sensitive to farmland distribution probability than the other explanatory variables.The spatial distribution probability of farmland in eastern part was greater than that in other parts of Hechi Region.

Key words: Guangxi Zhuang Autonomous Region/ Karst/ Farmland/ Logistic Regression Analysis