New Zealand Journal of Botany abstract
A late Holocene history of natural disturbance in lowland podocarp/
hardwood forest, Hawke's Bay, New Zealand
JANET M. WILMSHURST
Department of Zoology
University of Canterbury
Private Bag 4800
Christchurch, New Zealand
Present address: Manaaki Whenua - Landcare
Research, P. O. Box 69, Lincoln 8152, New
Zealand
MATT S. McGLONE
TREVOR R. PARTRIDGE
Manaaki Whenua - Landcare Research
P. O. Box 69
Lincoln 8152, New Zealand
Abstract Palaeoecological investigations of sediment cores
from two lake basins in the Tutira and Putere districts of Hawke's Bay
demonstrate the impact of volcanic activity, fires, and storms on the
vegetation and soil stability before human settlement and deforestation. A
"disturbance curve" derived from the classification and ordination of pollen
records, and correlated with charcoal and sediment records, illustrates
relative forest disturbance over time. Before anthropogenic forest clearance in
Hawke's Bay, forest composition fluctuated frequently as a result of
disturbance from fires, droughts, and a major volcanic eruption. Each natural
disturbance, indicated by short-term increases of seral taxa, was followed by
complete forest redevelopment. Cyclonic storms were not a major cause of
disturbance to lowland
podocarp/hardwood forests in the region, nor to the bracken-scrubland
vegetation that replaced the forest after clearance. However, storms scoured
and rapidly transported riverbank sediments into the lake basins. Compared with
the preceding natural disturbances, deforestation by early Maori settlers
represents a type and magnitude of disturbance previously unrecorded in the
cores.
Keywords charcoal; disturbance; erosion; fire; lake sediment;
pollen; Taupo Tephra
B95051
Received 1 November 1995; accepted 21 August 1996
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