On the Conifer Regeneration Gap in New Zealand: The Dynamics of Libocedrus Bidwillii Stands on South Island

Abstract

For the evergreen conifer-broadleaved forests of New Zealand, many authors have postulated widespread regeneration failure due to climatic change during the past millenium. The structures of stands characterized by L. bidwillii, one of the main species for which regeneration failure has been postulated, were studied in 5 South Island localities representing a wide range of site conditions and species composition. Small-scale gap-phase regeneration of L. bidwillii occurs where poor drainage reduces the abundance and vigor of young trees of most of the species in the gap. Where the vegetation has been massively disturbed by exogenous phenomena such as landslides or extensive windthrow, L. bidwillii often establishes in relative abundance in association with trees such as Phyllocladus alpinus and Nothofagus solandri. The regeneration failure hypothesis is a logical consequence of climax theory according to which old stands are expected to be in equilibrium. A dynamic scheme which does not require a stable end-point for succession and which emphasizes continuous change, even in old forests, is more consistent with the dynamics of L. bidwillii.