© 2007 Heron Publishing—Victoria, Canada
Changes in sapwood permeability and anatomy with tree age and height in the broad-leaved evergreen species Eucalyptus regnans
Jacqueline R. England (1–3) and Peter M. Attiwill (1)
1. School of Botany, University of Melbourne, Victoria 3010, Australia / 2. Present address: Ensis—a joint venture between CSIRO and Scion, Private Bag 10, Clayton South, Victoria 3169, Australia / 3. Corresponding author (jacqui.england@ensisjv.com) / Received July 30, 2006; accepted December 4, 2006; published online May 1, 2007
Summary
Increases in plant size and structural complexity with increasing age have important implications for water flow through trees.
Water supply to the crown is influenced by both the cross-sectional area and the permeability of sapwood. It has been hypothesized
that hydraulic conductivity within sapwood increases with age. We investigated changes in sapwood permeability (k) and anatomy with tree age and height in the broad-leaved evergreen species Eucalyptus regnans F. Muell. Sapwood was sampled at breast height from trees ranging from 8 to 240 years old, and at three height positions
on the main stem of 8-year-old trees. Variation in k was not significant among sampling height positions in young trees. However, k at breast height increased with tree age. This was related to increases in both vessel frequency and vessel diameter, resulting
in a greater proportion of sapwood being occupied by vessel lumina. Sapwood hydraulic conductivity (the product of k and sapwood area) also increased with increasing tree age. However, at the stand level, there was a decrease in forest sapwood
hydraulic conductivity with increasing stand age, because of a decrease in the number of trees per hectare. Across all ages,
there were significant relationships between k and anatomy, with individual anatomical characteristics explaining 33–62% of the variation in k. There was also strong agreement between measured k and permeability predicted by the Hagen-Poiseuille equation. The results support the hypothesis of an increase in sapwood
permeability at breast height with age. Further measurements are required to confirm this result at other height positions
in older trees. The significance of tree-level changes in sapwood permeability for stand-level water relations is discussed.
Keywords:
development, sapwood hydraulic conductivity.
