Mesure du flux de sève par sonde de dissipation thermique unique : exploitation du régime transitoire

Abstract

• In thermal dissipation method the stationary regime is used to estimate sap flow density from the temperature difference between a heating probe and a non-heating one. • A new approach, based on the non-stationary regime of a single heating probe, is investigated on an olive tree branch. Probe temperature is monitored for different flow densities and for heating and cooling modes. Measurement sequences of 10 min using 5 s time steps are made just after the heating is switched on or off. • Results show that temperature variation has a quasi-exponential phase whose duration decreases for increasing flow densities. Thermal indices using temperature of the probe measured at initial, final, and intermediate times ti were developed. Relationships between sap flow density and thermal indices were found to be linear for ti = 10 s−60 s with better coefficients of determination in cooling mode (R 2 = 0.94−0.96) than in heating (R 2 = 0.83−0.93). Validation tests confirmed the robustness of the