© 1995 Heron Publishing—Victoria, Canada
Climate influences the leaf area/sapwood area ratio in Scots pine
Maurizio Mencuccini (1, 2) and John Grace (3)
1. University of Florence, Institute of Forest Ecology and Silviculture, Via S. Bonaventura 13, 50145 Firenze, Italy / 2. Boyce Thompson Institute for Plant Research, Tower Road, Ithaca, NY 14853-1801, USA / 3. University of Edinburgh, Institute of Ecology and Resource Management, Darwin Building, Mayfield Road, Edinburgh EH9 3JU,
Scotland, U.K. / Received March 16, 1994
Summary
We tested the hypothesis that the leaf area/sapwood area ratio in Scots pine (Pinus sylvestris L.) is influenced by site differences in water vapor pressure deficit of the air (D). Two stands of the same provenance were selected, one in western Scotland and one in eastern England, so that effects resulting
from age, genetic variability, density and fertility were minimized. Compared with the Scots pine trees at the cooler and
wetter site in Scotland, the trees at the warmer and drier site in England produced less leaf area per unit of conducting
sapwood area both at a stem height of 1.3 m and at the base of the live crown, whereas stem permeability was similar at both
sites. Also, trees at the drier site had less leaf area per unit branch cross-sectional area at the branch base than trees
at the wetter site. For each site, the average values for leaf area, sapwood area and permeability were used, together with
values of transpiration rates at different D, to calculate average stem water potential gradients. Changes in the leaf area/sapwood area ratio acted to maintain a similar
water potential gradient in the stems of trees at both sites despite climatic differences between the sites.
Keywords:
hydraulic architecture, Pinus sylvestris, stem permeability, transpiration, xylem water potential.
