Spatial and temporal variations of land use and vegetation cover in Southwest China from 2000 to 2015.

Southwestern China is an important ecologically resource area and ecologically fragile area in China, which plays an important role in the national project of "Clear Waters and Green Mountains". Based on land use data set with a 1 km spatial resolution and combined with land use transfer matrix, we analyzed the characteristics and driving forces of land use change in Southwest China from 2000 to 2015. Based on the MODIS remote sensing index, we calculated the vegetation coverage in Southwest China using the dimidiate pixel model, and analyzed the changes of the normalized vegetation index (NDVI) and vegetation coverage. Results showed that the main land types were woodland, cropland and grassland. The built-up land area increased by 5874 km(55.8%), the cropland area decreased by 6211 km, and grassland decreased by 2099 km. From 2000 to 2015, the area that had been changed to built-up land was the largest, mainly from cropland (contributed 68.2%), woodland (contributed 19.2%) and grassland (contributed 13.1%). The transformed areas were mostly close to urban area. The area and rate for the transformation of cropland were 7079 km and 2.2% respectively, accounting for 46.0% of all the transferred out areas. Most of the woodland were transformed from grassland (61.8%), mainly distributed in central and southern Guizhou and western Yunnan. Both NDVI and vegetation coverage were significantly increased, indicating that the whole region was greening. NDVI of both natural vegetation and cropland increased significantly, while the NDVI of areas with expanded build-up land decreased. Therefore, natural vegetation and cropland dominated the vegetation change in this region. Results of the resi-dual analysis showed that both climate change and human activities contributed significantly to the greening trend.