Modeling water transportation and storage in sapwood — model development and validation

I have described a single tree water flux model that combines the stomatal conductance model based on plant physiological knowledge with the concept of fluid mechanics used to describe water transportation and storage in sapwood. The model was parameterized and validated using field data of the water budget of Cryptomeria japonica [J. Jpn. For. Soc. 78 (1996) 66] determined by weighing a suspended cut tree. In their experiment, water transportation and storage in the sapwood and leaves and the sapwood potential were examined under ordinary conditions and extreme conditions where water uptake was stopped by sealing the cut stem surface. Numerical experiments show the information to reproduce the observed results: low intensity of stomatal response to decreasing leaf water potential and lower hydraulic conductance of the crown sapwood than the conductance of the trunk sapwood. The model reproduced the observed results under both ordinary and extreme conditions using only information of observed physical size and hydraulic properties, except for the information on low values of hydraulic conductance of the crown sapwood.