Functional Ecology and Community Dynamics

Leader : Guillaume SIMIONI

The Functional Ecology and Community Dynamics discipline combines skills in dendrometry, ecophysiology and modelling. We study the functioning and dynamics of forest stands and landscapes, particularly in response to climate change. The growth and ecophysiological response of trees and stands are analysed under natural conditions and in the face of anthropogenic modifications (silviculture, fire management) or in response to climate (drought, temperature). These studies combine long-term monitoring in situ, experiments in situ and occasionally in controlled environments, and modelling.

More recently, we have been studying the risk of drought through observation and experimentation on two ecosystems: one typically Mediterranean, adapted to drought because it is frequently subjected to this hazard (holm oak-Aleppo pine mixture), and the other mountain-Mediterranean, more vulnerable to this type of disturbance (beech-fir forest). We are also studying the effect of silviculture on the response of cedars to drought.

The work in this area is based on a range of field systems: experimental plots for long-term observation at different altitudes on Mont Ventoux, an instrumented site for long-term monitoring of water and carbon balances in the Font-Blanche mixed forest, comparative plantations (PlantaComp), and systems for comparing silvicultural treatments (cedar).

Measurements at the Font-Blanche site, combined with simulations using the NOTG (3D carbon balance) and SUREAU (tree hydraulics) models, were used to characterise the components of the carbon cycle of the Aleppo pine/evergreen oak mixture, as well as the hydraulic vulnerability of these species.  In a mountain environment, the study of beech and fir tree rings has enabled us to compare the response of these two species to drought and the changes in their optimum production levels with altitude in recent years. All of this work has led to a model of the decline of the Pectin Fir, which is more likely to be explained by a progressive lack of carbon due to successive droughts than by a massive summer embolism.

We also work with the Physics and Ecology of Fire team. In this context, we are particularly interested in the processes involved in the circulation of water in the plant, which are a gateway to understanding the dehydration of woody plants under drought conditions and acclimatisation to drought.