VEGETATION RESPONSE TO VOLCANIC-ERUPTIONS ON EGMONT VOLCANO, NEW-ZEALAND, DURING THE LAST 1500 YEARS

Re-establishment and recovery of indigenous vegetation following volca nic activity on Egmont Volcano, Taranaki, over the last 1,500 years ha s been investigated by pollen analysis. Tephras were recovered in situ and used as dating planes. Analyses from a total of seven cores from four locations at altitudes from 1,200-285 m are reported here. Vegeta tional change results firstly from edaphic change following the additi on of large quantities of dry tephra to a wet site. Changes at Manganu i Bog relate closely to the cushion and hollow structure of the bog. S econdly change results from the type of event and the scale and intens ity of damage to the plant community. Analyses at Stratford Mountain R oad show that a pyroclastic flow (c. 1,980 years BP) devastated the le atherwood (Brachyglottis elaeagnifolia) scrub. Re-establishment, furth er delayed by subsequent minor events, took > 1,400 years. This commun ity however, proved resistant to the more recent Burrell Ash and Lapil li showers. In the forest, emergent and canopy species suffer the most immediate damage and then die. Decapitation of the emergents and open ing up of the canopy then allows aggressive species such as Coriaria a nd Weinmannia to increase. Lianes and epiphytes also respond to the in creased light intensity. The present composition of the lower montane forest dominated by Weinmannia differs from that before the Burrell ev ents. Some possible changes to the tephrochronology of the last 500 ye ars are suggested.