Responses of autumn vegetation phenology to climate change and urbanization at northern middle and high latitudes

Shifts in vegetation phenology caused by climate change and human activities play a crucial role in regulating global terrestrial ecosystems' nutrients and carbon cycling. However, the mechanism underlying autumn vege-tation's phenological reaction to urbanization remains unexplained. Using normalized difference vegetation index (NDVI) and a nighttime light remote sensing dataset, we examined the dynamics of the end of the growing season (EOS) and responses to climate change and urbanization from 1992 to 2015 across the northern middle and high latitudes (north of 30 degrees N). EOS exhibited an advanced trend with a pace of-0.22 days/yr across the study area. The spatial proportion of advanced EOS was 62.66%, which was more pronounced north of 60 degrees N. In most regions, increased precipitation delayed EOS, whereas daytime temperature (Tmax) and nighttime tem-perature (Tmin) exhibited the opposite impacts on EOS, which was related to water availability in the study area. In general, we found that higher urbanization could induce earlier EOS in warm regions (south of 46 degrees N) and delay EOS in cold regions (north of 46 degrees N). Urbanization could cause an increase in Tmin and Tmax, and EOS exhibited a significant negative sensitivity to Tmin across the urbanization levels, which decreased from-0.175 days/degrees C to-0.112 days/degrees C. Our results indicated that urbanization could advance the EOS by increasing Tmin, however, such a negative effect may be weakened with the development of urbanization. Our findings demonstrated the complicated influence mechanisms of autumn vegetation phenology induced by climate change and urbanization, which provides a unique perspective for exploring the contribution of growing season vegetation to the carbon sink and global carbon balance.