Aims The purpose of this study was to examine and compare
two extreme value distribution functions (the Gumbel and the
Weibull functions) in modelling the distribution of the minimum
and the maximum values of representative sets of tree
diameter samples. Both of these functions were applied to the
lower and upper values of the diameter distributions of the
main forest species in northwest Spain: Quercus robur L.,
Betula pubescens Ehrh., Pinus radiata D. Don, Pinus pinaster
Ait. and Pinus sylvestris L.