Late Holocene development of two wetlands in the Te Paki region, far northern New Zealand

The history of two wetlands in far northern New Zealand is examined from stratigraphic and palynological evidence. Although both the Te Werahi and Ponaki wetlands appear superficiallysimilar (both are dominated by raupo, Typha orientalis, and both are barriered by unvegetated coastal sands), radiocarbon dates show that they are of very different ages. The Te Werahi wetland shows organic sedimentation covering at least the last 3,700 years. This suggests it originated at the time that sea-level reached its present position around 6,500 years B.P. A sharp rise in the abundance of charcoal particles in sediments from the Te Werahi wetland indicates an increase in fire frequency between 2,620 and 2,150 years B.P. A phase of forest reduction, and destabilization of coastal sands, may date to this period. The Ponaki wetland has developed within the last 200–300 years. We argue that fire removed the vegetation and led to erosion of catchment soils and destabilization of coastal sands. Blocking of the stream outlet by a sand barrier probably accounts for subsequent wetland development or expansion. Pollen and sediment data support these conclusions

A late Quaternary vegetation history for far northern New Zealand

Pollen diagrams are described for 2 sites near Cape Regina from far N North Island. Forest persisted throughout the last 17 000 yr and while initially containing cooler elements change indicating a maximum in diversity and complexity was attained between 10 000-6800 BP. This was the warmest and probably most mesic environment represented in the record. Nothofagus was never an important element and Dacrydium cupressinum, Podocarpus spp. and tree ferns dominated throughout. Agathis australis expanded from c11 500 BP but declined after 3000 BP, perhaps associated with increased droughtiness. Shrubland also occurred throughout the record; natural fire was an important component in their function. Fire incidence increased in the recent past suggesting it was an agent in forest destruction following human occupanc