Da. Coomes et Pj. Grubb, A COMPARISON OF 12 TREE SPECIES OF AMAZONIAN CAATINGA USING GROWTH-RATES IN GAPS AND UNDERSTOREY, AND ALLOMETRIC RELATIONSHIPS, Functional ecology, 12(3), 1998, pp. 426-435
1, The relative growth rate of saplings of 12 species from an oligotro
phic lowland rain forest were measured in treefall gaps and understore
y. Mean relative height growth (R-H) within treefall gaps was found to
be slowest for tall-tree species with branched saplings, intermediate
for subcanopy trees and fastest for tall-tree species with unbranched
saplings. Most species had similar R-H within the understorey. R-H va
lues were not related to leaf mass per unit area (LMA) or foliar N con
centrations. 2, Allometric relationships between the total leaf area (
TLA) and height were dependent upon light conditions; in general sapli
ngs of a given height had a greater TLA in treefall gaps than in under
storey. The species with the largest estimated TLA values in gaps tend
ed to have the greatest R-H values in gaps; no such trend emerged in t
he understorey. The values of the allometric coefficients were not rel
ated to foliar properties. 3. The relationship between stem diameter a
nd height was only weakly dependent on light conditions and the relati
onship between the growth rates in these dimensions was also weak. The
lack of plasticity may reflect the fact that the height-diameter rela
tionship has little bearing on a sapling's tolerance of shade. 4. One
way of accommodating the dependence of allometry upon irradiance is to
add R-H as a covariate. We derive a relationship between growth rates
from this resource-dependent allometric equation and show that it rea
sonably describes measurements taken in the caatinga forest.