What makes leaves fall in autumn?

A new process description for the timing of leaf senescence in temperate and boreal trees

Leaf senescence is the process that allows trees to recapture nutrients (for example nitrogen) from their leaves before they are shed in late autumn. During senescence, the green chlorophyll pigment is degraded and the yellow to red colors of other pigments (for example carotenoids) become visible. The process of leaf senescence is crucial not only for tree growth and development, but also to define the duration of the growing season and the possible role of forest ecosystems in mitigating climate change. However, we do not fully understand the mechanisms behind leaf senescence in deciduous trees and in particularly which environmental factors trigger its starting date. Is it day length or temperature? And what is the impact of drought and site fertility on this process? The LEAF-FALL project aims to unravel these mechanisms, understand better the tree dynamics during the autumn season and improve the climate models currently lacking information on this topic.