New Zealand Journal of Botany abstract
Late Holocene forest disturbance in Gisborne, New Zealand: a comparison of
terrestrial and marine pollen records
JANET M. WILMSHURST
Landcare Research
P.O. Box 69
Lincoln 8152, New Zealand
DENNIS N. EDEN*
Landcare Research
Private Bag 11052
Palmerston North, New Zealand
PAUL C. FROGGATT
Research School of Earth Sciences
Victoria University of Wellington
P.O. Box 600
Wellington, New Zealand
*Present address: c/o Postal Centre, Ashhurst,
New
Zealand.
Abstract A late Holocene (from c. 5500 yr B.P.) record of
vegetation change is presented for the Gisborne region, based on pollen,
charcoal, and tephra analyses of a terrestrial and a marine core. Up until the
time of anthropogenic deforestation about 650 yr B.P., well drained lowland
areas were covered with a Prumnopitys taxifolia, and Dacrydium
cupressinum-dominated podocarp/hardwood forest. The poorly drained
Dacrycarpus dacrydioides-dominated alluvial swamp forests were not as
vulnerable to fire, and remained on the Gisborne Plains until European drainage
and clearance began in the 19th century. In the last 5500 yr B.P., the lowland
forests have been disturbed by at least five ashfalls originating from volcanic
eruptions in the Central Volcanic Region. Where the terrestrial and marine
cores overlap, comparisons of the pollen records show the vegetation changes
and taxa present to be comparable. The fire record was not clear in the marine
record, as the charcoal curve was diluted with high background levels of
reworked charcoal. Sedimentation rates from the marine core indicate that
erosion in the Waipaoa catchment has increased significantly since European
clearance of soil-protecting remnant forest and fern/scrubland and its
replacement with pasture.
Keywords charcoal; deforestation; disturbance; El
Niño; fire; human impact; New Zealand; pollen; Poverty Bay; tephra;
vegetation history; volcanism
B98049
Received 5 August 1998; accepted 25 February 1999
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