AN EMPIRICAL STUDY OF WOUND RESPONSE DYNAMICS ON SAP FLOW MEASURED WITH THERMAL DISSIPATION PROBES
The thermal dissipation technique (TD) has become one of the most popular methods for sap flow measurements. As other methods, the TD technique implies a damage of the wood tissue, consequently changing wood thermal properties due to healing reactions. Several studies report an underestimation of sap flow due to the wound effects and specific corrections have been developed for the individual methods. However, the wound effect has not yet been experimentally assessed for the TD method. In this paper we suggest an empirical approach to investigate the effect of wound healing on measured sap flux densities with TD probes. Our main goal is to establish specific correction factors for both ring-porous and diffuse-porous species, according to the duration of installation. Successive sets of TD probes will be installed in early- as well as in mid-growing season in diffuse- and ring-porous trees (Fagus sylvatica and Quercus petraea) in order to test the effects of dynamic wound formation. The trees will be cut in autumn and additional sets of sensors will be installed in each stem segment, thus without wound reaction. Different flux densities will be applied through the segments in the laboratory and be measured gravimetrically and by the TD sensors simultaneously. Gravimetric flow can then be compared to the TD sensors with and without wound reactions. Production of thick-walled xylem may disturb the flow path and heat conductivity around the inserted aluminium tubes of the TD probes. Therefore, we hypothesize a stronger underestimation of sap flow with increasing time since installation. A higher wound effect is also expected in ring-porous species and in warmer and wetter conditions. Wound correction factors obtained in this study could be implemented to any other TD measurements in the same species in order to improve the accuracy of the estimations of tree water use.
Wiedemann, A., Jiménez, S.M., Rebman, C., Cuntz, M. and Herbst, M. (2013). AN EMPIRICAL STUDY OF WOUND RESPONSE DYNAMICS ON SAP FLOW MEASURED WITH THERMAL DISSIPATION PROBES. Acta Hortic. 991, 107-113
sap flow, TD, wound effect, thermal dissipation method, Fagus sylvatica, Quercus petraea