With the Landsat-TM images in 1990、2000 and 2010 as a data source, fractional vegetation cover in Hechi District was calculated by using the dimidiate pixel model based on NDVI and was classified into five grades. Overlaying the fractional vegetation cover maps and the geological map, the impact on fractional vegetation cover exerted by geological structure was analyzed. Finally, the landscape pattern of change in fractional vegetation cover during this period was studied using a landscape pattern analysis program FRAGSTATS by analyzing 10 Landscape indices at class-level and at landscape-level to show the changing feature of landscape pattern. The results indicate that: 1) The fractional vegetation cover in the study area was increased from 1990 to 2010 and the region with high and relatively high vegetation fractions were still dominant in the area. 2) The landscape heterogeneity and fragmentation of the study area were declined, while landscape dominance was increased in the study area. 3) The patch shape of the study area mainly depended on natural landform and natural environment condition from 1990 to 2010. 4) The aggregation degree of the whole landscape was generally increased. The whole landscape in the study area has been more and more controled by several types of the vegetation coverage grades during 1990-2010.
The ecological restoration of vegetation landscape in the study area was significant, which tallies with economic social development in the stage of 1990-2010. The research findings will lead to the change of ecological restoration of vegetation landscape in no-karst district is more obvious than it in karst district. The landscape in karst district is more scattered and more complex than it in no-karst district. Ecological conditions in karst district is more easily destroyed and difficultly restored than it in no-karst district. These may explain the particularity of karst ecosystem.