© 2003 Heron Publishing—Victoria, Canada
Branch and foliage morphological plasticity in old-growth Thuja plicata
Zoe R. Edelstein (1) and E. David Ford (1, 2)
1. College of Forest Resources, Box 352100, University of Washington, Seattle, WA 98195-2100, USA / 2. Author to whom correspondence should be addressed (edford@u.washington.edu) / Received June 27, 2002; accepted December 30, 2002; published online June 2, 2003
Summary
At the Wind River Canopy Crane Facility in southeastern Washington State, USA, we examined phenotypic variation between upper-
and lower-canopy branches of old-growth Thuja plicata J. Donn ex D. Don (western red cedar). Lower-canopy branches were longer, sprouted fewer daughter branches per unit stem
length and were more horizontal than upper-canopy branches. Thuja plicata holds its foliage in fronds, and these had less projected area per unit mass, measured by specific frond area, and less overlap,
measured by silhouette to projected area ratio (SPARmax), in the lower canopy than in the upper canopy. The value of SPARmax, used as an indicator of sun and shade foliage in needle-bearing species, did not differ greatly between upper- and lower-canopy
branches. We suggest that branching patterns, as well as frond structure, are important components of morphological plasticity
in T. plicata. Our results imply that branches of old-growth T. plicata trees have a guerilla growth pattern, responding to changes in solar irradiance in a localized manner.
Keywords:
branch morphology, foliage angle, shoot silhouette area, SPAR, STAR, western red cedar.
