Urbanization delays plant leaf senescence and extends growing season length in cold, but not in warm, areas

Urbanization is quickly becoming one of the most important drivers of global environmental change as human population and economic development rapidly increase. However, the effects of urbanization on plant phenology, especially leaf senescence and the length of growing season across large spatial scales, are still understudied. Previous work suggested that urbanization advances leaf-out in cold regions but delays it in warm regions. We thus hypothesize that the effects of urbanization on leaf senescence, and consequently the length of growing season, are also dependent on climate context. Both in situ observations and remote sensing-based phenological datasets strongly supported our hypothesis. Specifically, we found that urbanization delayed leaf senescence and extended growing season length in cold regions. However, urbanization advanced leaf senescence and shortened growing season length in warm regions, implying the positive effects of urbanization on growing season length in cold regions may be weaker in a warmer future.