Spatio-temporal Variations of Fractional Vegetation Coverage and Influencing Factors in Qianxi'nan Prefecture from 2000 to 2015

It is essential to appraise the spatio-temporal variations of vegetation coverage in Karst rocky desertification areas for ecological protection and restoration. Taking Qianxi'nan Prefecture in Guizhou Province as an example, based on MOD13Q1 image data, the fractional vegetation coverage (FVC) was calculated by using pixel dichotomy method. With the trend analysis, Hurst index, residual analysis and hotspot analysis, the spatial-temporal variations and future trend of FVC in Qianxi'nan Prefecture from 2000 to 2015, as well as the impacts of climate change and human activities on FVC were analyzed. The results show that: (1) The FVC of Qianxi'nan Prefecture was increasing from 2000 to 2015, which was higher in the southeast and lower in the north. The growth rate of FVC in non-Karst areas was higher than that in Karst areas. (2) The FVC of Qianxi'nan Prefecture was improving. The improvement area accounted for 40.38%, mainly distributed in the eastern part of Zhenfeng County, the western part of Wangmo County and the south-central part of Pu'an County. The proportion of vegetation improvement area in non-Karst area (41.53%) was greater than that in Karst area (39.37%). The degradation areas were mainly distributed in the built-up areas of cities, counties and their surrounding areas, and the basically unchanged areas are widely distributed. (3) The predicted area of future continuous improvement (13.30%) was greater than that of future continuous degradation (9.77%), and the uncertain future change area accounted for 68.02%. Therefore, it is necessary to strengthen ecological management and restoration in uncertain change area and vegetation degradation area. (4) Among temperature and precipitation factors, the former played a substantial role in Qianxi'nan Prefecture. The Grain for Green Project and the urban development intensity are the main human factors leading to variations of FVC in Qianxi'nan Prefecture.