New Zealand Journal of Botany abstracts

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Genotypic variation of dead leaf retention by Cordyline australis (Lomandraceae) populations and influence on trunk surface temperatures

Warwick Harris

Landcare Research
P.O. Box 69
Lincoln 8152, New Zealand

Present address: Lincoln Botanical, 16 Aylmers Valley Road, Akaroa 8161, New Zealand. Email: wdaharris@clear.net.nz

Ross E. Beever
Stephanie L. Parkes

Landcare Research
Private Bag 92710
Auckland, New Zealand

Tony McSeveny

Landcare Research
P.O. Box 69
Lincoln 8152, New Zealand

Abstract  The retention of dead leaves covering the trunks of 8-year-old trees of Cordyline australis (cabbage tree, ti kouka) was significantly different between 28 wild populations from a 12° latitudinal range in New Zealand when grown under uniform garden conditions at Mt Albert, Auckland (36°53′S, 174°43′E) and Lincoln, Canterbury (43°38′S, 172°29′E). Particularly at Lincoln, trees of populations originating from south of latitude 38°45′ mostly had trunks fully covered by dead leaves at the time of observation. Temperatures recorded at Lincoln at heights of 1.40 m and 0.05 m showed that chilling on the trunk surface was reduced by a cover of dead leaves, particularly at 0.05 m during radiation frosts. This effect was separated from the shelter effect of the green leaf tufts of trees and shelter between trees in the experimental plantation. The adaptive function of the retention of dead leaves on the trunk of C. australis in frost-prone locations in southern New Zealand is considered with reference to other possible adaptive functions.

Keywords  Cordyline australis; cabbage tree; genotypic variation; dead leaf retention; latitudinal variation; temperature insulation; adaptive functions; New Zealand

B04005; Received 13 February 2004; accepted 25 July 2004; Online publication date 9 December 2004
New Zealand Journal of Botany, 2004, Vol. 42: 833–845
0028–825X/04/4205–0833 © The Royal Society of New Zealand 2004

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