Journal of the Royal Society of New Zealand abstracts
Floodplain and regional scale variation in earthquake effects on forests,
Westland, New Zealand
Louise E. Cullen1,3, Richard P. Duncan1, Andrew
Wells2, and Glenn H. Stewart1
1Ecology and Entomology Group, Soil, Plant and Ecological Sciences
Division,
P.O. Box 84, Lincoln University, Canterbury, New Zealand.
Email: duncanr@lincoln.ac.nz
2Department of Conservation, Private Bag 701, Hokitika, New
Zealand.
3Present address: School of Plant Biology, Faculty of Natural
and Agricultural Sciences,
University of Western Australia, 35 Stirling Highway, Crawley WA 6009, Australia.
Abstract Using existing and new tree age data, we assess
spatial variation in earthquake effects in Westland at regional and floodplain
scales. In Westland there have been four major episodes of forest cohort establishment,
three of which appear to relate to Alpine Fault earthquakes in AD c. 1460,
1610-1620, and 1717, and the fourth of which coincides with a Fiordland earthquake
in AD 1826. The AD 1826 event had its greatest effect in south Westland.
In contrast, the impacts of the AD 1610-1620 and 1717 earthquakes were more
extensive, with forest cohort initiation following both events occurring
throughout Westland. However, these two events differed in their effects
at the floodplain scale, with the AD 1610-1620 event triggering a larger
aggradation event on floodplains than the AD 1717 event. Variation in earthquake
effects at a regional scale most likely reflects variation in earthquake
magnitude and the location of the epicentre. At a floodplain scale, variation
in effect could reflect differences in both earthquake magnitude and shaking
and the amount of sediment stored in upland catchments as a consequence of
the time elapsed since the last event.
Keywords aggradation events; Alpine Fault; earthquakes;
earthquake impact; forest cohort establishment; forest disturbance; Westland
R02017 Received 19 June 2002; accepted 28 May 2003; online publication
date 19 November 2003
© Journal of the Royal Society of New Zealand, Volume 33, Number
4, December 2003, pp 693-701
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