Transpiration efficiency using 3D canopy structure

PI : Didier Le Thiec (UMR 1434 SILVA)

Collaborations : M Dassot (Ecosustain)

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Context — Drought is one of the most important abiotic stresses limiting the growth of trees and will of increasing importance for forest plantations in the coming decades. With the global changes expected, areas affected by this constraint will be expanding. To predict the consequences on the dynamics of forests and the productivity of plantations requires the understanding of the mechanisms of acclimation of trees to water deficit and the evaluation of intra and interspecific response. The optimization of water use (WUE) for the production of biomass is an important research aim in poplar. For long term studies on trees and to address scale changes it is necessary to use models. Studies of WUE at leaf level are numerous but to date, studies that address changes in scales are rare.

Objectives — The objective of the project is to determine the transpiration efficiency at the tree scale using a modeling approach that will be parametrized at the leaf level. We will try to answer this question: how can leaf WUE be integrated over the whole tree crown to calculate transpiration efficiency at the whole plant level?

Approaches — Two genotypes of poplar  have been selected according to their tolerance to drought. Half of the trees have been subjected to a reduced water input by a partial rain exclusion set-up, whereas the other half have been irrigated when necessary, in field conditions. We will also rely on experimental resources that encompass the technical platform PTEF (isotopy) as well as leaf gas exchange and sap-flow measurement devices.

Expected results and impacts — This study will supply original and integrative results concerning drought response of trees. Indeed, different scales will be studied and finally integrated, from the leaf to the tree. The results will improve our understanding of the mechanisms of acclimation to water deficit through the control of water use efficiency.