title: Improving sap flux density measurements by correctly determining thermal diffusivity, differentiating between bound and unbound water.
abstract: Several heat-based sap flow methods, such as the heat field deformation method and the heat ratio method, include the thermal diffusivity D of the sapwood as a crucial parameter. Despite its importance, little attention has been paid to determine D in a plant physiological context. Therefore, D is mostly set as a constant, calculated during zero flow conditions or from a method of mixtures, taking into account wood density and moisture content. In this latter method, however, the meaning of the moisture content is misinterpreted, making it theoretically incorrect for D calculations in sapwood. A correction to this method, which includes the correct application of the moisture content, is proposed. This correction was tested for European and American beech and Eucalyptus caliginosa Blakely & McKie. Depending on the dry wood density and moisture content, the original approach over- or underestimates D and, hence, sap flux density by 10% and more.
authors.affiliation: Laboratory of Plant Ecology, Faculty of Bioscience Engineering, Ghent University, Coupure links 653, 9000 Gent, Belgium. maurits.vandegehuchte@ugent.be
authors.forename: Maurits W
authors.initials: MW
authors.lastname: Vandegehuchte
authors.forename: Kathy
authors.initials: K
authors.lastname: Steppe
mesh_terms: D004058:Diffusion; D029964:Fagus / Q000502:physiology*; D006358:Hot Temperature; D006813:Humidity; D008954:Models, Biological; D010827:Physiology / Q000379:methods*; D053147:Plant Exudates / Q000502:physiology*; D013696:Temperature; D013814:Thermal Conductivity; D014867:Water / Q000378:metabolism*; D014934:Wood / Q000166:cytology / Q000502:physiology
chemical_list: D053147:Plant Exudates; D014867:Water