Camille Roy
Master student
Department of Environmental Sciences

Supervised by:

Alexandre Roy (Regular member)

Co-supervised by:

Oliver Sonnentag (Regular member)

Research project description

Monitoring tree hydraulic strategies in the boreal forest based on measurements and modelling

Introduction: The boreal forest plays a crucial role in carbon cycles, but the interactions between climate and vegetation within this ecosystem are little understood. In addition, the tree hydraulics strategies and its response to water stress is not well known but could provide feedback that could increase the resilience of the boreal forest. It is now recognized that tree water storage (TWS) provides a buffer against daily water requirements for respiration (Matheny et al., 2015), where water storage in the trunk can provide 10-50% of the water for daily perspiration. The project proposes the innovative use of probes and modelling for the temporal monitoring of TWS on boreal species to better understand the response of these species to water stress. Objectives: The purpose of this project is to characterize the hydraulic strategies of different species in the boreal forest. The project is developed through the achievement of two specific objectives spread over two years. The first objective is to quantify these strategies using different instruments for measuring the TWS. The second objective will be to use the collected data to validate and calibrate the tree hydraulic model FETCH (Finite Difference Ecosystem-Scale Tree Crown Hydrodynamics model), which simulate the water movement in the tree depending on the tree hydraulic strategies. Study sites: The first site is the SIRENE experimental site located at the Université de Sherbrooke. The species observed at this site is the red pine. The second site is the Montmorency Forest of Université Laval, which is mainly composed of balsam fir trees. The third site is the Southern Old Black Spruce (SOBS), Saskatchewan, which is dominated by black spruce. Finally, the James Bay – Lemoyne site will also be observed. It is a boreal forest site, also dominated by black spruce. The four sites are equipped with dielectric probes in the trees and probes measuring soil moisture. Material and methods: The first step will be to analyze the data of different probes (dielectric probes, dendrometers, sap flow probes) installed at the four boreal forest sites. Since the installed dielectric probes measure the permittivity and not the water content of the trees directly, the probes will also need to be calibrated in the laboratory. For the second objective, the SOBS site will be used for the validation of the FETCH model, where parameters of the model will be adjusted according to the measurements obtained from objective 1. References: Matheny et al. (2015), Observations of stem water storage in trees of opposing hydraulic strategies. Ecosphere 6(9):165. Mirfenderesgi et al. (2016), Tree level hydrodynamic approach for resolving aboveground water storage and stomatal conductance and modeling the effects of tree hydraulic strategy. Journal of Geophysical Research: Biogeosciences 121.7: 1792-1813. Pappas et al. (2018), Boreal tree hydrodynamics: asynchronous, diverging, yet complementary. Tree physiology 38.7: 953-964. Mavrovic et al. (2018), Dielectric characterization of vegetation at L band using an open-ended coaxial probe. Geoscientific Instrumentation, Methods and Data Systems 7.3: 195-208.

Research Site Coordinates

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