New Zealand Journal of Botany abstracts

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Patterns of species composition, recruitment, and growth within canopy gaps in two New Zealand kauri (Agathis australis) forests

N. J. ENRIGHT

Department of Geography
University of Melbourne
Parkville, Australia 3052

R. M. BARTLETT
C. R. DE FREITAS

Department of Geography
University of Auckland
Private Bag 92 019
Auckland, New Zealand

Abstract Within-gap patterns of forest species composition, tree growth, and associated micro- climate were investigated in two kauri (Agathis australis) forests in northern New Zealand. Detrended correspondence analysis (DCA) of sites at Trounson Kauri Park revealed a gradient of changing species composition from gap centre to forest understorey. However, while some species were typical either of the understorey (e.g., Dysoxlylum spectabile) or the centre of large gaps (e.g., Knightia excelsa, Leucopogonfasciculata), no species was restricted solely to gap edge sites. Growth of potted tree seedlings over 6 months at different locations in and near a large canopy gap revealed a significant positive relationship between percent canopy openness (%CO) and height increase for each of the five species tested. The early successional tree Kunzea ericoides showed the greatest height increase at gap centre, while the long- lived conifer Dacrydium cupressinum had the greatest height increase in the forest understorey. DCA of within-gap vegetation at Huapai Reserve over the first 5 years following gap formation revealed several trends: (1) sample plots in the root zone on the southern side of the gap were most similar to gap centre plots, while those on the northern side were most similar to the forest understorey; (2) species composition (DCA loadings on the first axis) was significantly correlated with %CO; (3) at 9 of 10 sample locations within the gap, resprouts and individuals from the seedling bank were more likely to capture the available canopy space than seedlings established after gap creation.

Keywords canopy gap; canopy openness; micro- climate; Agathis australis; tree species diversity

B92038 Received 20 August 1992; accepted 25 May 1993
New Zealand Journal of Botany, 1993, Vol. 31: 361-373
0028-825X/93/3104-0361 $2.50/0 © The Royal Society of New Zealand 1993

PDF file of entire paper: medium quality (1089K); (scanned from paper original: notes about this process)

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