New Zealand Journal of Botany abstracts

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The dynamics of Agathis australis-Nothofagus truncata forest in the Hapuakohe Ecological District, Waikato Region, New Zealand

LISETTE COLLINS

Department of Biological Sciences
University of Waikato
Private Bag 3105
Hamilton, New Zealand
Present address: Environment Waikato, P.O. Box 4010, Hamilton East, Hamilton, New Zealand.

BRUCE BURNS

Landcare Research
Private Bag 3127
Hamilton, New Zealand

Abstract  In mixed stands with Agathis australis (kauri), Nothofagus truncata (hard beech) has frequently been described as not regenerating and appearing unhealthy. Hypotheses proposed by other authors to explain the dynamics of these stands that would lead to these observations include 1) the two species replace each other reciprocally, 2) a climate change-induced replacement of N. truncata by A. australis is occurring, and 3) N. truncata acts as a long-lived "nurse" for A. australis. These hypotheses were investigated by conducting stand structural analyses in the Hapuakohe Ecological District. The basal area of each species was not positively correlated with the density of saplings and seedlings of the other species, which does not support the reciprocal replacement hypothesis. N. truncata was not less abundant than A. australis and was regenerating at some sites, thus not supporting the theory of replacement induced by climate change. N. truncata was generally younger or of similar age to A. australis, suggesting that N. truncata does not act as a "nurse". Stand age structures suggest that both species establish in stands initiated by forest disturbance. Eighty-six percent of the N. truncata were healthy. The poor health of N. truncata further north may be caused by the senescence of relatively even-aged cohorts, extrinsic factors, or a result of the health of N. truncata declining as it nears its northern limit.

Keywords  Nothofagus truncata; Agathis australis; hard beech; kauri; Hapuakohe; demography; regeneration; stand structure

B00043
Received 11 October 2000; accepted 6 April 2001

New Zealand Journal of Botany, 2001, Vol. 39: 423-433

0028-825X/01/3903-0423 $7.00 (c) The Royal Society of New Zealand 2001

PDF file of entire paper: medium quality (916K); (scanned from paper original: notes about this process)

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