Xing Wen’s research while affiliated with Chinese Research Academy of Environmental Sciences and other places

Based on the SPOT VEGETATION NDVI data, the spatial-temporal variations of vegetation cover in Hexi region of Gansu province were analyzed by using the MVC (Maximum Value Composites) method and the linear regression analysis during 1999 to 2009, the NDVI change trends and characteristics of different land use types were extracted. According to the results, during the last 11 years, the vegetation cover showed an increasing trend in the overall Hexi region with the rate of 3.70%/10a. The improved area and degraded area account for 24.37% and 3.80% of the total area respectively, vegetation improved region is greater than the degraded region significantly. The vegetation cover has obviously increased in the oasis agriculture region, however, the degraded area of vegetation cover are mainly distributed in the southeastern high altitude mountainous area. Viewed from the land use types, in addition to the NDVI of forest and high coverage grassland have declined, other types have increased.

Taking the Landsat MSS(1975) TM & ETM+ (1990, 2000, 2005 and 2010) satellite images as the basic data sources, we extract the distributional information of oasis in the Heihe River Basin during 1975-2010. The results shows that: (1) Oasis expands from 1975 to 2010 and the growing rate especially quickly after the year of 2000, and Oasis reaches the top area of 8218.52 km;2; in 2010. (2) Oasis is composed by cropland, forest, wet land, cities and settlement place in the study area. The cropland, which occupies about 60% of the oasis, and the cities and settlements expanded gently, and the forest and wet lands are changeful relatively.