Impacts of the climate change on the vegetation in Maqu county in the upper reaches of Yellow River

The variations characteristic of vegetation and their relationship with climate variables in Maqu County of Yellow river upper reaches area between 1982 and 2003 were examined by using the monthly GIMMS NDVI data and local meteorological records. It indicated that the annual mean of NDVI increased weakly from 1982 to 2003, and the NDVI increase speed is the fastest in summer, the spring NDVI increased from 1982 to 2000 but decreased after 2000, autumn NDVI and winter NDVI decrease, The growing season of the pasture advanced was the main way answer to global warming since recent 22 years. And the cover degree in middle standard (0.3~0.5 NDVI values) is increased and that in high standard (ges0.7 NDVI values) is decreased. The impact of the climate change on the NDVI was different in different periods. The influence that the temperature and the precipitation on the NDVI in interdecadal scale are obviously but it was not notably in season scale except the summer temperature impact on the NDVI. In all, temperature was the main factor which influences on the vegetation growing in high height and cold area. Furthermore, an index was defined to reflect the turning green period (TGP) using the satellite data; it is the maximum value which equals 0.05 of the slope of the NDVI variation in term of the vegetation changing. It showed the TGP was effected by the temperature and it brought forward with the temperature rising. Trends in the TGP revealed advanced 3 day/10 years with the temperature from April to the may increased 0.6 square/ten years.