Reduced rainfall frequency accelerates leaf fall in autumn in the Northern Hemisphere
A study conducted by an international team with participation from CREAF reveals that it’s not just how much it rains, but how often, that determines when trees shed their leaves. This timing has significant implications for ecosystems and the global carbon cycle.
Climate change is altering not only the total amount of rainfall worldwide but also its timing and regularity. While scientists have long recognized that temperature and total rainfall influence plant growth and seasonal cycles, the role of rainfall frequency has been less explored. New evidence suggests that how often it rains can strongly affect ecosystems, plant physiology, and even the global carbon cycle.
Led by Xinyi Zhang and co-authored by Prof. Josep Peñuelas, our study published in Nature Communications investigates how rainfall frequency shapes the timing of autumn leaf fall in the Northern Hemisphere. The findings show that fewer rain events, regardless of total rainfall, can significantly speed up leaf shedding, impacting plant productivity and carbon absorption.
Using satellite-derived vegetation indices and long-term carbon flux data from 1982–2022, the team examined how temperature, sunlight, and rainfall patterns affect leaf fall. They found a clear trend: areas with less frequent rainfall see earlier leaf drop, even if annual precipitation totals remain stable.
The images illustrate the progressive aging of leaves: healthy green leaves (left), early yellowing leaves (center), and fully aged brown leaves (right). Reduced rainfall frequency accelerates this process, highlighting the impact of drought stress on leaf senescence. Composition of photos from: Pixabay/klickblick, Pixabay/CAWFotografie, Pixabay/kubicek_robert.
Lower rainfall frequency increases drought stress by drying the soil around roots and the air, limiting photosynthesis and accelerating plant aging. This shows that the timing of rainfall can be just as important, or even more so, than the total amount of rain.
The study highlights that changes in rainfall patterns can profoundly affect ecosystems in ways traditional climate metrics may miss. Less frequent rain can intensify drought effects, even when total rainfall appears unchanged, with cascading consequences for forest productivity, nutrient cycles, and biodiversity.
Rosa Casanovas-Berenguer and Josep Peñuelas
CREAF
Esfera UAB
References
Zhang, X., Wang, X., Zohner, C.M., Peñuelas, J., Li, Y., Wu, X., Zhang, Y., Liu, H., Shen, P., Jia, X., Liu, W., Tian, D., Pradhan, P., Belarmain Fandohan, A., Peng, D., Wu, C. 2025. Declining precipitation frequency may drive earlier leaf senescence by intensifying drought stress and enhancing drought acclimation. Nature Communications 16, 910 (2025). Doi: 10.1038/s41467-025-56159-4.
