Abstract: Based on 3S（GIS，RS，GPS）technique, a comparative analysis was made on the landscape dynamic changes in the Kerqin sandy land areas with different desertification formation causes. The results showed that in past 20 years, the desertified land in Baxiantong, where the desertification process was mainly affected by human activities, had a greater change extent, which represented in the transformation from mobile and semi-fixed sands to fixed sands and from fixed sands to cropland and woodland. In Weiliansu, where the desertification process was mainly affected by natural disturbance, the desertified land had smaller changes, and mainly manifested in the inter-transformation among different types of sands. In the areas dominated with human activities, the spatiotemporal pattern of fixed sand had significant changes, i.e., the association of fixed sand decreased in 1985-1995, reflecting the enhanced human disturbance, but increased in 1995-2005, reflecting the comparatively weaker human disturbance. In natural disturbance dominated areas, the spatiotemporal pattern of mobile sand changed obviously, with the fractal dimension index decreased and the area increased in 1985-1995 and the fractal dimension index further decreased but the increased area being restrained in 1995-2005, indicating that the effect of combating desertification was prominent during 1995-2005.

Key words: Plant community, Species diversity, Maintaining mechanism