Table 1.

Summary of linear models for f₀ and D₀. The entries are adjusted R²-values for ordinary least-squares linear regression models. In the case of f₀, the three architectural indices are CVR, crown asymmetry and aspect ratio. In the case of D₀, the two architectural indices are total tree volume and crown area. The numbers in parentheses for the open-grown trees correspond to the insets in figure 5, they demonstrate the sensitivity of linear models to outliers in this sample.

		field data		model results
		N	f0 ∝ dbh/H2	N	f0 ∝ dbh/H2	f0 ∝ dbh/H2 × (A1 + A2 + A2)	D0 ∝ H + dbh	D0 ∝ H + dbh+ A1 + A2
broadleaf	temperatea	63	0.32	568	0.42	0.83	0.09	0.12
	tropical	41	0.09	348	0.16	0.56	0.16	0.29
	open-grown	59	0.45	54 (42)	0.82 (0.18)	0.93 (0.42)	0.29	0.69
conifers		603	0.77	—	—		—	—
all trees		765	0.55	970	0.62	0.86	0.26	0.40

^aFor temperate deciduous trees, the field data were measured in full-leaf. All models are specified in Wilkinson notation. For details on linear model selection, see electronic supplementary material, figures S1–S4.