Abstract
Sap-flow of Quercus robur, Quercus petraea and Quercus cerris oak trees were studied. 43K radioisotope tracing, the heat pulse velocity technique and the Granier-method were employed. Numerous intense pulses were observed in healthy Quercus petraea superposing onto the usual diumal change. Only a few pulses were observed in unhealthy Quercus petraea, in healthy Quercus cerris and healthy and unhealthy Quercus robur trees. Proportion of wet-wood assessed by γ- and X-ray computer tomography and magnetic resonance imaging was significantly less in healthy Quercus petraea trees than in healthy Quercus cerris trees. Proportion of wet-wood was higher in healthy trees than unhealthy trees of both species.