RESPONSES OF SATELLITE OBSERVED VEGETATION GREENNESS TO CLIMATE CHANGE AND HUMAN ACTIVITY IN A SEMI-ARID BASIN OF NORTH CHINA

Changes in vegetation growth are important indicators of health of terrestrial ecosystems. Located in China's semi-arid and semi-humid transitional zone, the Fenhe River Basin is the second largest tributary of the Yellow River, which is vital for soil and water conservation in the Loess Plateau. In this study, based on the Normalized Difference Vegetation Index (NDVI) and meteorological data during 1982-2015, we evaluated the spatial-temporal distribution and changes in the vegetation greenness and meteorological variables in the Fenhe River Basin before and after the Grain for Green Program (GGP), in order to reveal the driving factors of changes in vegetation growth, and then quantify their relative contributions. The results show that since the GGP being implemented in 1999, the vegetation coverage in the Fenhe River Basin has significantly improved. Climate change and human activities are two important factors affecting the vegetation greenness detected from NDVI and the combined effects of the two factors play a leading role in NDVI change. After the implementation of GGP, the influence of climate on NDVI change has weakened, and the area proportion of human activities improving vegetation growth has raised significantly. This study is valuable for providing knowledge about the dynamic changes of vegetation in the Fenhe River Basin under the influence of climate change and human activities, and provides decision support information for vegetation restoration and sustainable development in the Fenhe River Basin.