In this study, we adopted and integrated GIMMS NDVI (1982–2006) and MODIS NDVI (2001–2013) remote sensing data to analyze spatial-temporal variations of desert vegetation and its response to climatic changes in the Hexi area, Gansu Province during 1982-2013. In addition, the model of desert vegetation phenology has been constructed, which includes GD (Greenup Date), SD (Senescence Date) and LG (Length of Growth Season), and the spatial-temporal variations of desert vegetation phenology, furthermore its response to climate changes was also been analyzed. The results of this research reveal that:
the desert vegetation activities mostly remain stable in the Hexi area from 1982 to 1999 (PhaseⅠ), which was significantly improved in 52.11% of the area during 2000-2013 (PhaseⅡ), except for individual areas that was suffered desertification increasing in the PhaseⅡ.The desert vegetation had been largely stable in different river basins during the PhaseⅠ, however, the improvement trend occurred in all river basins especially in the Shule River Basin of the western Hexi area during the PhaseⅡ. The vegetation improvement phenomenon mainly occurred in the middle and lower reaches of the Shule River Basin and the Shiyang River Basin. During the period of 1982 to 2013, the significant restoration area of typical desert vegetation accounted for 40.7% of the total typical desert vegetation regions, which was higher than that of the mountain desert vegetation (18.45%).
As a whole, there were insignificant advancing ratios observed for the GD and the SD, respectively, with -6.2d/10a and -1.8 d/10a during 2000-2013, and insignificant prolonged ratio of the LG was 2.77 d/10a. The GD and the SD have advanced tendency in the majority of the Shiyang River and the Heihe River basin, but the change was different in the Shule River Basin from 2000 to 2013. Besides, the advanced tendency of the GD, the SD, and extension of the LG of the mountains desert vegetation were relatively obvious than that of the typical desert vegetation.The main factors for vegetation growth were precipitation of spring and summer, the vegetation growth was affected by precipitation during March and August that covered about 95% of the total desert vegetated land, and the temperature had little effect on the growth of desert vegetation. the mountain desert vegetation growth was influenced more significantly by precipitation than the typical desert vegetation, because of lower drought-resistance...