© 1991 Heron Publishing—Victoria, Canada
Tree allometry, leaf size and adult tree size in old-growth forests of western Oregon
David A. King (1, 2)
1. Smithsonian Tropical Research Institute, APO, Miami, FL 34002-0011, USA / 2. Department of Biological Sciences, University of New South Wales, P.O. Box 1, Kensington, N.S.W. 2033, Australia / Received December 5, 1990
Summary
Relationships between tree height and crown dimensions and trunk diameter were determined for shade-tolerant species of old-growth
forests of western Oregon. The study included both understory and overstory species, deciduous and evergreen angiosperms and
evergreen conifers. A comparison of adult understory species with sapling overstory species of similar height showed greater
crown width and trunk diameter in the former, whether the comparison is made among conifers or deciduous trees. Conifer saplings
had wider crowns than deciduous saplings, but the crown widths of the two groups converged with increase in tree height. Conifer
saplings had thicker trunks than deciduous saplings of similar crown width, possibly because of selection for resistance to
stem bending under snow loads.
The results suggest that understory species have morphologies that increase light interception and persistence in the understory,
whereas overstory species allocate their biomass for efficient height growth, thereby attaining the high-light environment
of the canopy. The greater crown widths and the additional strength requirements imposed by snow loads on conifer saplings
result in less height growth per biomass increment in conifer saplings than in deciduous saplings. However, the convergence
in crown width of the two groups at heights greater than 20 m, and the proportionately smaller effect of snow loads on large
trees, may result in older conifers equalling or surpassing deciduous trees in biomass allocation to height growth.
