Analysis of Spatial and Temporal Variations about Vegetation Fractional Cover in Urumqi City from 2000 to 20 1 4
Based on four periods of remote sensing images of TM/ETM+/OLI (2000,2006,2010 and 2014)and digital elevation model of ASTER GDEM,the vegetation fractional cover distribution maps in the four periods were got by conducting the pixel dichotomy model using NDVI (Normalized Difference Vegetation Index). Further,the vegetation coverage level maps in the four periods were overlaid with alti-tude map,slope gradient map and slope aspect map respectively. The map were generated using digital el-evation model ASTER GDEM to calculate and analyze the distributions and variations of vegetation cover in the horizontal and vertical direction. Finally the temporal and spatial changes of vegetation fractional cover,the vegetation improvement/degradation and the driving forces were analyzed. Massive degradation and significant improvement like the shape of U and the 2006 as a turning point showed the trends of veg-etation fractional cover in the four periods. Compared with 2006,the vegetation cover of temperate semi-shrubby and dwarf semi-shrubby desert region in the north of Urumqi County and in the northeast of Mi-dong District were improved to some extent. And the vegetation cover of temperate dwarf semi-arboreou desert in the north of Midong District and temperate dwarf needlegrass,dwarf semi-shrubby desert steppe in Dabancheng District were improved more significantly in 2014. Therefore,the distributions and varia-tions of vegetation cover in Urumqi city was affected by natural factors such as precipitation,terrain factors (elevation,slope,aspect)and vegetation cover type and so on,as well as anthropogenic factors including economic activity and ecological conservation program. Desert grassland coverage had stronger instability, which was coupled by natural and anthropogenic factors,so we should improve the level of protection. Especially,a variety of ecological protection projects of forestry and grass in recent years in Urumqi city were carried out on a large scale,which played a vital role in the promotion of vegetation frac-tional cover and improvement of the ecological environment of Urumqi city.
vegetation fractional coverNDVIchange trends of vegetationterrain factorsUrumqi
NETL
NSTL
万方数据
维普
