Spring phenology outweighed climate change in determining autumn phenology on the Tibetan Plateau

As the third pole of the Earth, the Tibetan Plateau (TP) is highly sensitive to climate change. Phenological changes in spring (i.e., the start of the growing season, SOS) over the TP are of much debate, while our understanding on the variation of autumn phenology (i.e., the end of the growing season, EOS) is still lacking. Given the significance of tracing the latest variation of EOS induced by the ongoing global change, we used the currently longest time series (1982-2018) of the normalized difference vegetation index of the Long Term Data Record from the Advanced Very High Resolution Radiometer (AVHRR LTDR NDVI) and investigated the responses of EOS to biological and climatic factors. We found that the EOS showed an insignificantly delayed trend at an average rate of 0.14 days center dot decade(-1) on the TP. This variation was found for all vegetation types except for alpine sparse vegetation. We further showed that spring SOS had the largest contribution to the interannual variations in EOS, where 46.5% of the vegetated areas showed significantly positive correlations between SOS and EOS (p < .05). Temperature (26.5%) and precipitation (18.8%) also had significant positive impacts on EOS, while the contribution of radiation was negative (11.3%). These correlations were regulated by local hydrothermal conditions, especially for precipitation gradients. Using the longest satellite data currently available, with the state-of-art data processing, we demonstrated a weakly delaying trend of EOS and the controlling role of spring phenology on the interannual variability of EOS, which is of great significance to improve our comprehension of the interactions between vegetation dynamics and climate change in the future.