Ecophysiological interpretation of the mechanisms and dynamics of sap production in sugar maple

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Sugar maple is a key species in Canada's economy, playing an important role in forestry, tourism, food and agriculture. Under the current global warming, this species and its main product, maple syrup, are experiencing a significant pressure by the changing environmental conditions. It is now urgent to anticipate these changes, adapt the productive system of sap extraction in the Southern regions, and take advantage of new development opportunities for the Northern regions. I propose innovative long-term monitoring using automatic sensors for the automatic collection of physiological and weather data, and sap production in sugar maple at high temporal resolution. My proposal aims to develop and test the first mechanistic model describing flow and production of sap. In particular, I (1) describe the circadian cycles of sap flow and variation in the stem; (2) determine the anatomical and physiological traits associated with a high productivity of sap; (3) quantify the impact of weather on the dynamics and amount of sap produced in spring; and (4) combine all empirical observations to build a first theoretical model describing the mechanisms of sap production in sugar maple. Starting with one permanent plot already running since 2017, I would like to equip other permanent plots across the sugar maple range with dendrometers and sap flow probes to monitor each 30 min the physiological conditions of stems in spring, at the end of dormancy. Sap production can be measured automatically using rain gauges connected to tapping sugar maples. Bud break and leafing are detected at a daily resolution by phenocam, i.e. using digital images collected by digital cameras installed in the field. All sensors are activated by dataloggers of a weather station collecting environmental and soil moisture conditions. The model will be used to predict the effects of changing conditions on stem rehydration and spring growth reactivation and their consequences on the timings and duration of sap production. The results will help to understand and quantify the processes underlying sap flow and spring sap production, and quantify how the sugar season will be affected by the climate change. This project will suggest the adaptations of the production system during sap harvesting. More generally, it will support the strategies of producers to maintain the productivity of populations in the South, and increase the exploitation of sugar maple at the Northern stands.