Late holocene changes in the vegetation of Western Taranaki investigated by soil palynology : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy at Massey University

Abstract

The study area in western Taranaki is dominated by the andesitic volcano, Mount Egmont.Palynological study of 22 fossil pollen sites from a vide range of sediments has produced evidence of change in vegetation over last 4000 years.The resilience of the indigenous vegetation ensured survival of temperate lowland forests until the arrival of European settlers about 150 years ago.Within this period,deforestation of the lowlands has been almost complete.Surviving forest is protected within Egmont National Park. There is little evidence of pre-European deforestation,but indications of earlier fires are thought to be due to an increase in the Maori diet of Pteridium rhizomes,dictated by a change of climate about 400yr B.P. Information has been gained in general terms about the effects of older tephras and in detail about damage and recovery after tephras deposited within the last 400 years.A revised tephrochronology for the last 400 years is offered. Palynological evidence suggests that an equable climate existed between 4000-1400yr B.P. A decline of Ascarina from very high values at this time to low values at 400yr B.P. has been interpreted as due to a prevalence of droughts.Since 400yr B.P. the climate has been wetter and cooler.This, together with the availability of newly exposed sites due to volcanic activity,has resulted in a dominance of Weinmannia in the Mount Egmont forests. Such dominance is not seen in pollen profiles of older sites over the last 4000 years.