Abstract:

Using a dimidiate pixel method, the annual maximum vegetation coverage in Three Gorges Reservoir Area (TGRA) from 2000 to 2009 was estimated based on the MODIS NDVI remote sensing data. Furthermore, the temporal-spatial variation and its driving force of annual maximum vegetation coverage were analyzed at pixel scale. The results showed that the annual maximum vegetation coverage was high in the most area of TGRA, and approximate 92% of the whole area had the annual maximum vegetation coverage greater than 60%. The annual maximum vegetation coverage increased with the increasing of elevation and slope. In recent 10 years, annual vegetation coverage of the whole area showed a weak increasing trend. The pixels with significant increase or decrease in the annual maximum vegetation coverage were only 7.16% of total pixels, and the vegetation coverage of Shizhu, Jiangjin and Fengdu had high degradation risk out of the total 20 counties. Precipitation was the dominant driving factor for annual fluctuation of vegetation coverage in TGRA. The annual maximum vegetation coverage was notably related to the accumulated precipitation from May to August. However, there was obvious spatial difference in the correlation. The significant positive correlation pixels mainly distributed in the western hilly farmland in TGRA, where the increase of precipitation can promote the vegetation growth. The precipitation was considerably negatively correlated with the vegetation coverage at the higher sea levels in the northeastern part of TGRA.

Key words: vegetation fraction, dimidiate pixel mode, NDVI, spatial and temporal variations, Three Gorges Reservoir Area