© 2002 Heron Publishing—Victoria, Canada
Variation in specific needle area of old-growth Douglas-fir in relation to needle age, within-crown position and epicormic
shoot production
Hiroaki Ishii (1, 2, 3), E. David Ford (1), Melissa E. Boscolo (1), A. Carolina Manriquez (1), Megan E. Wilson (1, 4) and Thomas M. Hinckley (1)
1. College of Forest Resources, University of Washington, Seattle, WA 98195-2100, USA / 2. Biosphere Dynamics Research Group, Institute of Low Temperature Science, Hokkaido University, Sapporo 060-0819, Japan / 3. Author to whom correspondence should be addressed (hishii@pop.lowtem.hokudai.ac.jp) / Received February 5, 2001; accepted August 8, 2001; published online December 1, 2001
Summary
Variation in specific needle area (SNA; cm2 projected fresh needle area g–1 oven-dried needle weight) was investigated in relation to needle age, within-crown position and epicormic shoot production
in 450-year-old Douglas-fir (Pseudotsuga menziesii Mirb. (Franco) var. menziesii) trees. Specific needle area decreased with increasing needle age. The magnitude and rate of change in SNA with needle age
were greatest for lower-crown branches, and decreased toward the middle- and upper-crown branches. For all branches, there
was no difference between regular and epicormic shoots in the relationship between SNA and needle age. Specific needle area
decreased with increasing distance from branch base, and this relationship was significant for the majority of needle age
classes of the upper- and middle-crown branches. In the lowercrown branches, SNA did not vary with distance from branch base
for the majority of needle age classes. For all branches, there was no difference between regular and epicormic shoots in
the relationship between SNA and distance from branch base for the majority of needle age classes. These results indicate
that renewal of foliage by epicormic shoot production maintains needle quality. Branch SNA increased linearly with decreasing
height in the crown at a mean rate of 0.951 ± 0.110 cm2 g–1 per vertical meter. Total needle area of branches was estimated from total needle dry weight taking into account within-branch
variation in SNA. Analyses of allometric relationships between branch size and foliage amount (needle area and needle dry
weight) showed that branch length was a better predictor of foliage amount than branch diameter for old Douglas-fir trees.
Total needle dry weight and needle area of the sample trees, estimated from branch length and branch height and taking into
account vertical within-crown variation in branch SNA, ranged from 42.4 to 154.2 kg and from 246.2 to 816.0 m2 per tree, respectively.
Keywords:
foliage area estimation, morphological plasticity, needle morphology, Pseudotsuga menziesii, tree aging.
