COMPARISON OF SAP FLOW, CAVITATION AND WATER STATUS OF QUERCUS-PETRAEA AND QUERCUS-CERRIS TREES WITH SPECIAL REFERENCE TO COMPUTER-TOMOGRAPHY

Concurrent measurements of sap velocity (heat pulse) and ultrasound ac oustic emission were performed on the trunks of mature Turkey oak (Que rcus cerris) and sessile oak (Quercus petraea) trees, Plant water stat us was assessed by measuring leaf water potential, leaf conductance an d transpiration, Wood density was estimated non-destructively on the t runk section of the plants by mobile computer tomography, which measur es the attenuation of a collimated beam of radiation traversing the tr unk in several directions, as the device rotates around the tree, Abso rption is proportional to the density of the wood, As wood density is strictly correlated to water content, this non-invasive method allows the water content in the trunk section to be evaluated as well as mapp ed. Leaf water potential declined each morning until a minimum was rea ched at midday and recovered in the afternoon, lagging behind changes in transpiration rate, Good correspondence was found between the patte rns of sap velocity and cavitation rate, A close correlation was demon strated between wood density, mater content and sap velocity, Sap flow was always higher in Turkey oak than in sessile oak, Trunk signatures by computer tomography appeared to differentiate the two oak species, with the Turkey oak stem clearly more hydrated than the sessile oak; water storage reservoirs could play an important role in tree survival during extended periods of low soil water availability and in the rel ative distribution of tree species, especially in the context of globa l climate change. Late-wood conducting elements of oak species seem to play a significant role in water transport, The mobile computer tomog raph was confirmed as a peerless tool for investigating stem water rel ations, Diurnal variations in the measured parameters under natural dr ought conditions and the differences between the two oak species are d iscussed.