Remotely sensed identification of the differentiating factors controlling vegetation drought responses on the Tibetan Plateau

Abstract:

With a typical alpine meadow ecosystem, the Tibetan Plateau is a highly representative location to observe the effects of climate change on ecosystems. Although continuous global warming has significantly influenced the vegetation growth on the Tibetan Plateau, the force driving the response of vegetation to droughts on the Tibetan Plateau is still obscure due to relatively limited evidence. With the research objectives of understanding the spatial heterogeneity of the vegetation response to drought and identifying the key potential environmental factors influencing the response behind the superficial elevation dependence on the Tibetan Plateau, we introduced three remotely sensed vegetation indexes and multi-scale drought indexes, including the Standardized Precipitation Index (SPI) and Standardized Precipitation–Evapotranspiration Index (SPEI), to determine the spatial response of vegetation growth to drought from 2000 to 2015. Land surface temperature, land cover, snow cover, population density, and soil texture were selected as potential drivers behind elevation control. The results showed that vegetation tended to be green in the east and brown in the west, and an average of 14.3%/12.0% (SPI/SPEI) of the vegetation growth on the Tibetan Plateau was significantly affected by drought. On average, 14.32%/12.02% (SPI/SPEI) of the area was significantly affected by water effectiveness (p<0.05). The drought responses of vegetation growth were mainly influenced by the land surface temperature, with the highest contribution rate of 65.8% at 3000-4500 m intervals. The time lag of response is mainly dependent on the proportion of grassland, with the highest contribution rate of 81.7% at 4500-6000 m intervals. The results provide reasonable evidence for a deeper understanding of the elevation dependence of the alpine ecosystem response to drought.