Response of Spring Phenology to Climate Change across Tibetan Plateau

To investigate the climate change effects on spring phenology at a spatial-temporal scale in Tibetan Plateau, an algorithm of dynamic threshold was applied to extract start of season (SOS) based on MODIS 250 m 16-days NDVI products. Then, the phenological responses to climate change were assessed by the linear regression of phenological dates against the current monthly temperature from 2000 to 2009. The vegetation ecosystems are sensitive to climate warming in Tibetan Plateau (2.72-9.72 days°C^-1). The SOS of meadow and steppe were advanced by up to 8.17 days°C^-1 and 5.69 days °C^-1 under climate warming. Finally, we investigated the impact of altitude on the spring phenology dates for steppe and meadow in 2000 and 2009, respectively. For each degree warming along with the altitude, the spring phenology was advanced by about 2.04 days and 1.8 days for steppe and meadow, respectively. Compared to the spring phenology variation adapted to local climate gradient (along with altitude gradient), the spring phenology on the Tibetan Plateau under climate warming is more sensitive, with about 3 times larger response amplitude.