A 6000 year palaeoenvironmental record from Harataonga, Great Barrier Island, New Zealand

Abstract

A pollen, sediment, and tephra record from a drained swamp at Harataonga contains a history of the local coastal environment from the Mid Holocene. This commences c. 6000 cal yr BP in a freshwater environment with swamp forest composed mainly of Laurelia, Leptospermum, Ascarina, and Cyathea spp. Dodonaea and Cyperaceae grew on margins of this forest. Forest on the hills surrounding the wetland comprised mainly Metrosideros, with emergent Dacrydium and Libocedrus. Ascarina, Rhopalostylis, and Cyathea dealbata type were a significant part of the under-storey of the hillside forest.

Around the time of deposition of the 5550 cal yr BP Whakatane tephra, a freshwater lake developed at the site. Extensive Cyperaceae swamp developed on the fringes of the lake. Shortly after c. 2900 cal yr BP, Dacrycarpus briefly invaded swamp forest, possibly as a result of storm disturbance, and the site made the final transition to swamp. Myrsine and then Hebe shrubs invaded fringes of the swamp as the water table fell, possibly as a result of a change to drier conditions in the Late Holocene. Polynesian deforestation, as indicated by the presence of abundant charcoal and Pteridium spores, is recorded in this core as occurring shortly after deposition of the c. 600 cal yr BP Kaharoa tephra.

Keywords

Palynology, Holocene, anthropogenic disturbance, Whakatane tephra, Kaharoa tephra, Great Barrier Island.