Fig. 9

Electrical resistivities (ER) measured from May 2018 to August 2019 on 44 fir trees (15 at Guery 1, 20 at Guery 2, and 9 at Saint-Germain). Each close point corresponds to the mean of the raw measured ERs for each of the 3 study sites (to facilitate visualization, SE has been removed). Open points correspond to the simulation of ER values computed according to the Lou et al. (2019) model in case of the electric properties of the trunk keep stable, and only the temperature (here the monthly mean) changes. The good similarities between the raw and simulated curves show that the variations of measured ER values over the seasons are clearly due to the temperature effect