Fig. 3.

Example of combined water content (MSE) in one of the storage pools and flow measurements (PFG-TSE) in the stem of a 4 years old oak during a developing drought period, followed by rewatering (indicated by the line). Water content of the bark as (represented by the relative amplitude, the fraction of signal intensity with respect to that of pure water, averaged over all pixels in the mask of the bark as highlighted in the inserted image of the stem), the flow conducting area and volume flow in the active xylem (the xylem ring just inside the bark and the cambial zone). For reference three psychrometer sensor readings of the water potential at three different positions on the stem of the same oak are given (Unpublished results of Homan N, Sperry JS and Van As H)