© 2003 Heron Publishing—Victoria, Canada
Interaction between sapwood and foliage area in alpine ash (Eucalyptus delegatensis) trees of different heights
Karel Mokany (1), Ross E. McMurtrie (1, 2), Brian J. Atwell (3) and Heather Keith (4)
1. School of Biological, Earth and Environmental Sciences, University of New South Wales, NSW 2052, Australia / 2. Author to whom correspondence should be addressed (r.mcmurtrie@unsw.edu.au) / 3. Department of Biological Sciences, Macquarie University, NSW 2109, Australia / 4. CSIRO, Forestry and Forest Products, Kingston, ACT 2604, Australia / Received August 9, 2002; accepted March 29, 2003; published online September 1, 2003
Summary
In native stands of Eucalyptus delegatensis R. T. Baker, sapwood area (As) to foliage area (Af) ratios (As:Af) decreased as tree height increased, contradicting the common interpretation of the Pipe Model Theory as well as the generally
observed trend of increasing As:Af ratios with tree height. To clarify this relationship, we estimated sapwood hydraulic conductivity theoretically based on
measurements of sapwood vessel diameters and Poiseuille’s law for fluid flow through pipes. Despite the observed decrease
in As:Af ratios with tree height, leaf specific conductivity increased with total tree height, largely as a result of an increase
in the specific conductivity of sapwood. This observation supports the proposition that the stem’s ability to supply foliage
with water must increase as trees grow taller, to compensate for the increased hydraulic path length. The results presented
here highlight the importance of measuring sapwood hydraulic conductivity in analyses of sapwood–foliage interactions, and
suggest that measurements of sapwood hydraulic conductivity may help to resolve conflicting observations of how As:Af ratios change as trees grow taller.
Keywords:
conducting tissues, leaf specific conductivity, Pipe Model, sapwood/foliage ratio, sapwood hydraulic conductivity.
