Nature 401, 907— 911 (1999).

In the last sentence of the abstract the relative growth rate equation, presented as (1/M) (dM/df), should read (1/ M) (dM/dt). Also, the sentence following that containing equation (5) should read “Thus, regardless of any possible time dependence of either the proportionality constants or the density, a plot of M1/4 versus M1/40 for fixed times t and t0 for any species should yield a straight line with a universal slope of unity but with an intercept that depends on the time interval and the species.”

In other words, the primary relationship is in terms of mass, M and not diameter, D. Equations (4) and (5), which relate the dependence of trunk diameter, D, on time, t, are only valid if the proportionality constant A ≡ CD/ρ3/8 is time-independent; A is the proportionality constant in the allometric relation D = AM3/8 of equation (3). This is needed because data are typically given in terms of D rather than M. The other proportionality constants, CG and C B, occurring, respectively, in the growth equation (2) and allometric equation for metabolic rate (3), can be time-dependent.

As our analysis of the data assumed time-independence of all of these coefficients as well as of wood density, ρ (see below equation (6)), this oversight does not affect our results or conclusions. If A were slowly varying, it would contribute a small correction to the unit slope prediction given by (t - t0)d, where d is the logarithmic derivative of A. This is expected to be very small, especially as the time interval (t - t0) is small relative to the lifespan of the species sampled. Furthermore, any time dependence in A is almost certainly smaller than its variation across species and effects arising from neglecting maintenance costs in the growth equation (2). We thank J. Banavar, J. Damuth, A. Maritan and A. Rinaldo for bringing this oversight to our attention.