HOLOCENE VEGETATION, CLIMATE AND HISTORY OF A RAISED BOG COMPLEX, NORTHERN NEW-ZEALAND BASED ON PALYNOLOGY, PLANT MACROFOSSILS AND TEPHROCHRONOLOGY

A Holocene history of vegetation, climate, and ombrogenous mire develo pment is presented from pollen and plant macrofossil analyses of sedim ents at Kopouatai Bog, a large, raised, restiad bog in northern New Ze aland. Tephra layers of established ages, supplemented by numerous rad iocarbon dates, provide a secure chronology. The earliest peats, overl ying last glacial sediments, and dated at c. 11700 radiocarbon years B P, with extensive accumulation after c. 10360 BP, are dominated by pol len of warm temperate podocarp-angiosperm forest, indicating a moist, mild early-Holocene climate. The bog began as a series of small solige nous mires within lowland podocarp-dominated swamp forest but was most ly oligotrophic by c. 8500 BP. Feat accumulation rates have varied spa tially and temporally, averaging 0.9 mm yr(-1) in central and southern areas. The deposition of deltaic muds in the northern part of the bog accompanied a marine transgression c. 6500-5000 BP, while elsewhere a n associated groundwater table rise resulted in a temporary return to mesotrophic conditions. As the marine influence subsequently receded, the northern areas remained subject to regular flooding, but underwent rapid peat growth at a mean rate of 1.7 mm yr(-1), while oligotrophic conditions returned to other parts of the bog. Regional vegetation de velopments indicate a change, c. 6000 BP, to drier, frostier condition s during the late Holocene. Ascarina lucida and Agathis australis may be used as regional pollen-stratigraphic markers for the early Holocen e and late Holocene, respectively. The loss of tall trees and expansio n of subcanopy species and seral vegetation in forests near Kopouatai Bog, just before the deposition of Kaharoa Tephra (c. 700 BP), are lik ely evidence for human activity dating from at least this time.