Mahjoub I., Masmoudi M. M., Lhomme Jean-Paul, Ben Mechlia N. (2009). Sap flow measurement by a single thermal dissipation probe : exploring the transient regime. Annals of Forest Science, 66 (6), p. 608. ISSN 1286-4560.
Titre du document
Sap flow measurement by a single thermal dissipation probe : exploring the transient regime
Mahjoub I., Masmoudi M. M., Lhomme Jean-Paul, Ben Mechlia N.
Source
Annals of Forest Science, 2009,
66 (6), p. 608 ISSN 1286-4560
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 t(i) were developed. Relationships between sap flow density and thermal indices were found to be linear for t(i) = 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 single probe method with lowest error obtained for t(i) = 20 s. Single probe method seems to be a promising technique to measure tree sap flow. Its application could be considered under cooling mode using t(i) = 20 s and relatively short measurement sequences e. g. 5-10 min.
