Shoot architecture was quantified by measuring the "maximum silhouette area
ratio" (R-max). R-max was calculated from the maximum silhouette area (or
projected area) of the intact shoot, divided by the silhouette area of the
leaves or phylloclades (leaf-like flattened stems) when they are removed fr
om the shoot and laid out flat. Like conifers of the Northern Hemisphere (N
H) with non-appressed foliage, the R-max of shade-adapted shoots ranged fro
m 0.5 to 1.0 in New Zealand (NZ) conifers with non-appressed foliage. Defin
ing a "leaf" to mean either a true leaf or a phylloclade, the following was
found: leaf area/leaf dry weight, leaf area/shoot dry weight, and leaf dry
weight/shoot dry weight, were all similar in the shade-shoots of NZ and NH
conifers. None of these variables were significantly correlated with R-max
in the NZ conifers, unless species with leaves averaging less than 4 mm(2)
in size were excluded from the analyses. Foliage dry weight/shoot projecte
d area was strongly correlated with R-max. NZ conifers had both smaller and
larger mean leaf sizes in comparison to NH conifers. The mean projected ar
ea per shade-adapted leaf of NZ conifers varied from 2.7 to 436 mm(2). In N
H conifers, the mean projected area per shade leaf varied from 12 to 83 mm(
2). Except for the strikingly larger range in leaf size in NZ conifers, the
data support a hypothesis of strong convergent evolution of shade-shoot ar
chitecture in NZ and NH conifers. The results are discussed in relation to
photosynthesis, stand production, and the ecological distribution of conife
rs.