plant biogeography

Population size and structure of 52 isolated Nothofagus fusca stands were investigated in the lower Otira Valley, 3-6 km from a major population centre in the upper Taramakau catchment. The approximate age of N. fusca pioneer trees, estimated from partial increment cores and calculations based on diameter growth rates, indicated that nearly all isolated stands originated after 1600 AD, predominantly during the periods 1600-1760 AD and 1865-1910 AD.

Scattered small stands of Nothofagus truncata occur in the upper Taramakau catchment, Arthur's Pass National Park, beyond the previously assumed range of the species in north Westland. Restricted to older soils on stable north to north-west slopes, the N. truncata stands are surrounded by N. fusca dominated forest and their upper altitudinal limits at 370-500 m border N.fusca-N. menziesii or N. solandri: var. cliffortioides forest.