Sap-flow velocities and distribution of wet-wood in trunks of healthy and unhealthy Quercus robur, Quercus petraea and Quercus cerris oak trees in Hungary

Sap-flow of Quercus robur, Quercus petraea and Quercus cerris oak trees were studied. K-43 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 diurnal 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 gamma- 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. (C)1998 Elsevier Science Ltd.