The inversion of gap proportion data for canopy structure variables has bee
n widely used in plant canopy analysers. However, the results for most fore
st canopies tend to be biased, due to the foliage clustering at different s
tructural levels. To invert the gap frequency data in forest stands for the
canopy leaf area index, new gap fraction formulas are proposed capable of
taking explicitly into account the clustering of foliage into crowns as one
of the most important clustering levels. The formulas are based on the giv
en mathematical expressions for the crown shape and on the Poisson or binom
ial tree distribution patterns. (C) 1999 Elsevier Science B.V. All rights r
eserved.