Responses of vegetation greening and land surface temperature variations to global warming on the Qinghai-Tibetan Plateau, 2001-2016

The Qinghai-Tibetan Plateau (QTP), as the "third pole of the earth", is China's the source of many driving ecological factors in China. However, in the context of increasing global change, the QTP is facing increasing ecological and environmental problems, such as vegetation degradation and land surface temperature (LST) changes. Here, we first analyzed the spatiotemporal trends in the optimized soil-adjusted vegetation index (OSAVI) and the LST. Then, we explored the relationship of vegetation and LST changes to climatic factors. Finally, we calculated the response relationship of the spatial and temporal changes in vegetation and LST to global climate change. The results show that from 2001 to 2016, the vegetation coverage on the QTP showed an overall upward trend, with significant spatial and temporal heterogeneity. The average annual increase in the OSAVI value was 0.0071, and the areas with significant OSAVI change trends accounted for 26.3% of the study area. Both OSAVI and LST showed a significant decreasing change trend with increasing altitude. From 2001 to 2016, the LST on the QTP generally showed an upward trend, with a variation of 0.3824 degrees C. Most of the LST peaks occured around July in each year, and climate warming will cause the peak time to occur earlier. In terms of spatial distribution, the change rate of the LST trend over the southern Himalaya and Hengduan Mountains was more than 40%. The LST in this area was negatively correlated with OSAVI, and the annual mean value of OSAVI showed a negative trend in this area, with a change rate of 10%. In the QTP region, from 2001 to 2016, climate change affected vegetation growth and surface temperature trends. During the growing season, spring and summer, OSAVI had a significant positive correlations with the atmospheric temperature (AT), but not with precipitation. In the same seasons, LST and AT showed very significant positive correlations, but were not correlated with precipitation. In autumn, OSAVI had no correlation with AT or precipitation, while LST had a positive correlation with AT and precipitation.