© 1990 Heron Publishing—Victoria, Canada
Integration of sapflow velocity to estimate plant water use
T. J. Hatton (1), E. A. Catchpole (2) and R. A. Vertessy (1)
1. Australian Centre for Catchment Hydrology, CSIRO, Division of Water Resources, G.P.O. Box 1666, Canberra, ACT 2601, Australia / 2. Mathematics Department, University College, University of New South Wales, Campbell, ACT 2600, Australia / Received September 14, 1989
Summary
The heat pulse technique provides an estimate of sapflow velocity at one position within the xylem of an individual plant.
Previous experience has shown that the velocity profile across the conducting area cannot be assumed to be constant, necessitating
several such point estimates for a reasonable characterization of the velocity profile with depth. These point estimates must
be integrated over the sapwood conducting area to derive flux. The most common method is to fit a one degree of freedom least-squares
polynomial to the point estimates, and then to integrate this equation across the sapwood profile and around the bole. An
alternative method is presented based on a weighted average approach. The latter is shown to be a more robust estimator of
flux when velocity profiles exhibit large curvatures.
