The late pleistocene and holocene vegetation history of Taranaki, North Island, New Zealand

Abstract

Pollen diagrams are presented from four lowland Taranaki sites which collectively span the last 13 000 years. Atc. 13000 years ago, lowland Taranaki was occupied by an open grassland in which shrubland was restricted and forest scarce. Beginning c. 12 500 years ago, there was a rapid transition, essentially complete by 11 000 years ago, to tall complex conifer/broad-leaved forest in which Prumnopitys taxifolia was the most abundant tall tree. By 9500 years ago, the last of the cool temperate forest elements (most notably Nothofagus menziesii and Libocedrus bidwillii) had been eliminated from the forest, and Dacrydium cupressinum had supplanted Prumnopitys taxifolia as the most abundant tall podocarp tree. In coastal regions, Ascarina lucida and Dodonaea viscosa were abundant. From 5000 years ago, Ascarina lucida and Dodonaea became much less common, and Ascarina lucida is now nearly extinct in the Taranaki region. Knightia excels a and Lagarostrobos colensoi spread during the late Holocene.

The early grassland phase suggests harsh climatic conditions, perhaps characterised by severe drought and frost, although annual average temperatures cannot have been much more than 4-5°C below those of the present. The subsequent spread of tall conifer/broad-leaved forest indicates a prolonged and apparently uninterrupted climatic amelioration. Early Holocene conditions seem to have been close to those of the present, although climatic variability and extremes were much reduced. From 9500 years ago to the present, climatic change was slight, but there is some indication of increasing summer water deficits and increased disturbance to the vegetation after 5000 years.

Keywords:

• Taranaki
• late-glacial
• Holocene
• Pleistocene
• pollen analysis
• tephra
• volcanoes
• climatic change
• conifer/broad-leaved forests