© 1992 Heron Publishing—Victoria, Canada
Integration of sapflow velocity in elliptical stems
Thomas J. Hatton (1), Diana Greenslade (2) and Warrick R. Dawes (1)
1. Hydroecology Group, CSIRO Division of Water Resources, GPO Box 1666, Canberra, ACT 2601, Australia / 2. Ocean Technology Group, University of Sydney, Sydney, NSW 2006, Australia / Received July 11, 1991
Summary
The estimation of water flux through the stem of a plant by point estimates based on the heat pulse technique requires integration
of the velocity profile. The polynomial integration method and the weighted average technique both assume radial symmetry
about the bole. A method is introduced that solves the equations for the ellipse in the weighted average technique, and includes
an optimizing algorithm for the placement of sensors. The sensitivity of sapflow estimates through stems to increasing eccentricity
is examined by means of analytical solutions and simulation. The error in sap flux measurement resulting from the radial approximation
of the sapwood conducting area is expressed analytically and shown to be small over the range of eccentricities (e < 0.8) expected in nature. Simulations where radial symmetry is assumed for elliptical stems show substantial error in mean
velocity (and thus flux) with modest eccentricities (e > 0.4).
