Phenology and photosynthesis

Compared to spring phenology, autumn phenology trends are less distinct, and the magnitude of changes is smaller. This is partly due to multiple confounding factors influencing end-of-season (EOS) dynamics. This project investigates the relationship between autumn phenology and photosynthesis.

Our findings show that increased photosynthesis does not lead to earlier leaf shedding in autumn. While a short-term (inter-annual) relationship exists—likely driven by variations in spring phenology and constrained leaf longevity—this pattern does not hold at decadal scales or across spatial gradients. This challenges the interpretation of a recent study by Zani et al. (2020) on the drivers of autumn phenology.

Rather than being driven by carbon sink saturation (i.e., plants ceasing activity once sufficient carbon has been assimilated), long-term trends in climate and rising CO2 levels enable plants to extend their growing season. This allows them to overcome leaf-longevity constraints, meaning that an earlier leaf-out trend does not necessarily result in earlier leaf-off. Instead, the opposite is observed—both in long-term temporal trends and spatial patterns.

This project has been published in Nature Ecology and Evolution Marqués et al. (2023).