Environmental change in Northland, New Zealand during the last glacial andHolocene

The Quaternary vegetation and climatic history of the northernmost region o f New Zealand, Northland, has long been the subject of speculation. Althoug h the coverage is incomplete and individual records are punctuated by gaps or marked changes in sedimentation rates, poor resolution and dating uncert ainties, recent work points to environmental changes that differ significan tly from those at higher latitudes in New Zealand. Conifer-angiosperm fores t has been important in Northland during most of the last glacial cycle wit h Agathis australis- and Nothofagus truncata-dominated communities prominen t during interstadials and stadials, respectively. Fire and effective preci pitation appear to have exerted greater influence on vegetation development s than temperature although the latter may control the competitive balance between Agathis and Nothofagus and will influence the environmental respons e to precipitation changes. With the exception of human impacts during the last millenium, the most striking vegetation changes are associated with wi despread fires towards the end of the last glacial and the moist preceding interstadial. In contrast, pre-human era Holocene environments have been co mparably stable although there is some evidence for increasing natural dist urbance and a drier, slightly cooler climate during the late Holocene. In s everal key aspects - a glacial maximum-to-lateglacial dry phase; very moist interstadial preceding the last glacial maximum; no widespread loss of for est; and the importance of fire and precipitation change in vegetation deve lopment during the last glacial cycle generally - Northland shows stronger affinities with south-eastern Australia than with other regions in New Zeal and. (C) 1999 INQUA/Elsevier Science Ltd. All rights reserved.