Late Quaternary vegetation, Tongariro region, central North Island, New Zealand

Abstract

Pollen profiles from sediments underlying the Kawakawa Tephra (20 000 yr BP) in the Tongariro region record 2 interstadials. The earlier interstadial, the Otamangakau, is considered to have reached its peak at c. 80 000 yr BP. Forest, similar to that of the present upper montane zone and consisting of abundant Libocedrus, Nothofagus, and podocarps, was dominant. Subalpme shrubland was prominent on sites marginal for forest. The climate was cool and wet, with temperatures perhaps as much as 2°C below present. The Otamangakau interstadial was followed by a long period of harsh climate during which there were episodes of severe erosion which stripped off most of the older soils and tephras in the region. A sparse grassland-shrubland covered the landscape. The younger interstadial, the Moerangi, began just before the deposition of the Rotoehu Ash (50–42 000? yr BP). As the climate wa~ed, shrubland spread and eventually a dense subalpine shrubland grassland, dominated by Dracophyllum, covered the landscape. Forest remained rare. At the peak of the interstadial (c. 30 000 yr BP), shrubland attained its maximum density, but the climate was cooler and drier than at present. Towards the end of the interstadial, at the time of the deposition of the Okaia Tephra (25–22 000? yr BP), grassland spread, in response to the onset of the cooler temperatures of the glacial maximum.

Keywords:

• pollen analysis
• vegetation history
• palynology
• glaciation
• climate history
• Quaternary
• vulcanism
• Tongariro, New Zealand
• Otamangakau interstadial
• Moerangi interstadial
• New Zealand palynology