Tree dielectric measurements in a black spruce forest stand

Three ruggedized soil moisture sensors (model GS-3; Decagon 302 Devices, Pullman, Washington, USA) were installed directly into 5.6 cm pre-drilled holes (length of probes) within tree trunks, in order to provide a measure tree relative dielectric constant (RDCtree) at Diameter Breast High (DBH). The probes are sensitive to liquid water, as liquid water has a high dielectric constant. The dielectric constant (D) follows ambient temperature in winter, but is near constant when trunks are thawed in the spring (Roy et al., 2020; Matheny et al., 2015).