Phenology refers to the study of the biological cycle of living organisms (plants, animals, insects, etc… ). Scientists studying phenology are particularly interested in the timing of biological events and their relation with local and global environmental changes such as temperature increase or natural/anthropic disturbances for example.

In this project, I am interested in plant phenology and more specifically trees and forests. The phenological cycle of trees can be described by five distinct phases, four of which are associated to clear visual changes of the canopy:

1- Growth: By using reserves stored during the previous year, tree unfolds its leaves when environmental conditions are favorable. First leaves will start to capture light and CO₂ while evaporating water, initiating the photosynthesis. CO₂ will be transformed into sugar that will be used to replenish reserves and to construct new material for branches, roots, other leaves, flowers and fruits. The plant grows.

2- Growth cessation: When growth stops, the tree prepares for winter.  The most visible change in the canopy is the formation of buds.

3- Dormancy induction: Winter dormancy refers to the period of the year when trees wait for favorable environmental conditions in order to grow again their leaves. Dormancy induction takes place during autumn. During this phase the tree will recover an important part of the material invested in the leaves (like nutrient as nitrogen and phosphorous for instance). This traduces by a clear change in color of the leaves. This is quickly followed by leaf fall.

Following leaf fall, two dormancy stages can be recognized: Endo-dormancy and Eco-dormancy.

4- Endo-dormancy: It refers to an inhibition of buds development induced by internal factors of the bud. Environmental factors alone cannot restart bud development during this phase. The transition between endo and eco-dormancy cannot be detected visually.

5-Eco-dormancy: On the opposite, eco-dormancy refers to the dormancy stage during which the bud is again able to sense environmental changes and remains dormant, waiting for weather conditions to be favorable for leaf unfolding. The end of eco-dormancy is traduced by a visible change in bud shape which start to enlarge and open. This is what we call bud burst.