The effects of the Taupo Tephra eruption of c. 1718 bp on the vegetation of Mt Hauhungatahi, central North Island, New Zealand

Abstract

Abstract. An altitudinal series of eleven fine resolution pollen diagrams were used to examine the role of volcanism in forest dynamics on Mt Hauhungatahi. Partial pollen diagrams from four of these sites, chosen to illustrate the major effects of the 1718 bp Taupo eruption, are presented. Following the eruption Libocedrus bidwillii expanded in all sites. Open sites created by the eruption may have facilitated an expansion already underway as a result of more variable climatic conditions since c. 3000 bp. Weinmannia racemosa invaded upper montane forest c. 650 bp. The current altitudinal sequence of forest types, with Libocedrus dominating the subalpine and Weinmannia the upper montane forests, has thus been synthesized only within the last 1800 years. This is interpreted as a consequence of individualistic species' responses to major disturbance by the eruption. The results support nonequilibrium theories of community composition.