A LATE HOLOCENE POLLEN RECORD OF DEFORESTATION AND ENVIRONMENTAL-CHANGE FROM THE LAKE TAUANUI CATCHMENT, NORTHLAND, NEW-ZEALAND

Late Holocene pollen and sediment records from the Lake Tauanui catchm ent, northern New Zealand, indicate that the lake formed about 5500 ye ars ago following a series of volcanic events in the Tauanui Volcanic Centre. These volcanic events initiated a volcanosere resulting in a m ixed conifer-hardwood forest. Dacrydium cupressinum was the dominant t ree. Agathis australis was always present. Changes similar to those re gistered in other Northland pollen diagrams are apparent. At ca 4000 y r B.P., when the climate became cooler and drier than before, a fire o ccurred in the catchment area causing erosion of the surrounding slope s and some destruction of forest. Fluctuations in abundance of many fo rest species, including Ascarina lucida, A. australis and D. cupressin um, from ca 3500 yr B.P. indicate repeated disturbance, increasingly s o after 1600 yr B.P. Summer droughts and increased frequency of cyclon ic winds are suggested as the cause. Major anthropogenic deforestation events defined by palynology occurred across many parts of the New Ze aland landscape at ca 700 yr B.P. At Lake Tauanui anthropogenic forest disturbance, radiocarbon dated to ca 1000 yr B.P., is indicated by si gnificant decline in all tree and shrub elements with concomitant incr ease in pteridophytes, especially Pteridium esculentum. Charcoal conce ntration increases steadily from the onset of disturbance, and in the final phase after the arrival of Europeans, major clearance of vegetat ion is indicated. Herbs increase markedly in this period, in diversity and abundance.