© 1993 Heron Publishing—Victoria, Canada
Three dimensional distribution of needle and stem surface area in a Douglas-fir
Warren L. Webb (1) and Michael J. Ungs (2)
1. Department of Forest Science, Oregon State University, Corvallis, OR 97331, USA / 2. McLaren Company, 1135 Atlantic Avenue, Alameda, CA 94510, USA / Received May 20, 1992
Summary
The distribution of needles and branches in the crown of a 14-m tall Douglas-fir was investigated for the purpose of developing
a three-dimensional structure for use with radiation transfer models. We found a linear relationship between the basal area
of main branches originating at the bole and the total one-sided planimetric surface area of the foliage attached to each
branch. A similar linear relationship was found between the branch basal area and the mass of stem material on the branch.
Total silhouette area (needles plus branch material) did not vary significantly horizontally along the branch length, but
stem surface area declined linearly from near the bole to the branch tip. Needle surface
silhouette area and leaf area index increased along the main branch from near the bole to the branch tip. Silhouette leaf
area (STAR) did not vary along the main branch.
The needle area density (NAD) (m2 m–3) was calculated for each of the lower 11 whorls; the vertical distribution of NAD increased from the base of the bole to
the top of the crown.
Keywords:
branch, canopy, conifers, leaf area density, photographic technique, silhouette area.
