Tree water content based on water dielectric and thermal properties

Water content in green stems (living trees) is a growing field. However, it is really difficult to have reliable measurements. Partially because we don’t really have a sensor dedicated for its measurement. Given that it is used in many other measurements, such as sap flow, remote sensing, etc., we often use other sensors for its measurement. In broad terms, there are two major types of sensors used for this purpose: thermometric, and dielectric sensors. The dielectric sensors can be split into various types such as frequency domain or time domain. In this project, we are validating both thermometric and frequency domain sensors. Our goal is to generate reliable equations capable of estimating volumetric water content in living stems of three major boreal species: Norway spruce (Picea abies), Scots pine (Pinus sylvestris) and Silver birch (Betula pendula). An additional area of study in our project, is the effect of freezing and thawing cycles on water content measurements. Thermometric and time/frequency domain sensors fail during the phase change of water-ice. However, we are developing a series of equations that would correct these measurements.