Carbohydrate reserves of poles

To what extent does the trees canopy cover opening modify carbon allocation between growth and storage functions?

PI :  Françoise Ningre
Joint Research Unit for Forest and Wood Resource Studies (LERFOB)

Co-applicants : Joint Research Unit for Forest Ecology and Ecophysiology (EEF)

Collaboration : Nathalie Breda (EEF), Bastien Gerard (EEF), Jacqueline Marchand (EEF), Catherine Collet (LERFOB)

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Context — Natural and anthropogenic canopy disturbances are major and frequent processes of forest dynamics. The ability of trees to respond quickly to the canopy cover opening determines their ability to reach the upper part of the canopy. It constitutes an essential element of the competitiveness of the trees in relation to their immediate neighbors.

This project focuses on poles (mature trees, potentially very old but with small diameters) present in the lower stratum in irregular settlements. It aims to predict the dynamics of growth under the effect of thinning (through the use of seven experimental sites installed in 2007).

Focused concentration on these poles and the total absence of competition with neighboring trees will allow for a better understanding of this extreme process linked to canopy opening. The project takes into account two species: beech trees with high competition tolerance and sessile oak trees which are less tolerant of competition.

Objectives — The project aims to test the variation of the carbon allocation between dominant trees and those trees released from competition for 6 years. It will also aim to determine the response of the two selected species: beech and sessile oak , and will examine how they react differently to the sudden opening of the cover.

Approach — To investigate the extent of modified carbon allocation in the growth function in individuals released from competition compared trees not released competition determined from their mensuration (height, diameter, etc.), architectural traits (proportion of living Crown forks…) or ontogenesis (age, growth rate). Measuring levels of carbohydrate reserves at the end of the growing season will allow us to evaluate carbon allocation (storage function).

Expected results and impacts — Research is expected to lead to characterized responses of trees to the opening of the canopy cover and to further our understanding of the processes that determine the resumption of growth for both species. The issuance of guidelines or recommendations may then be envisioned for developing forest management to be sustainable, productive and adapted to climatic constraints.