New Zealand Journal of Botany abstracts

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Can Podocarpus totara and P. hallii be distinguished by bark thickness?: A study on the southern coast of Southland/Otago, New Zealand

T. Matsui*
J. B. Wilson

Botany Department
University of Otago
P.O. Box 56
Dunedin, New Zealand

C. J West

Southland Conservancy
Department of Conservation
P.O. Box 743
Invercargill, New Zealand

*Present address: Department of Plant Ecology, Forestry and Forest Products Research Institute,
Matsunosato 1, Tsukuba-shi, Ibaraki-ken, 305-8687, Japan. Email: tematsui@affrc.go.jp

Abstract  Bark thickness has been said to be the key character in distinguishing Podocarpus totara from P. hallii. However, even this character has proved difficult to use, especially in the southern South Island coastal dune forests dominated by species of Podocarpus. Five stands of such forests were sampled in which bark thickness and tree diameter at breast height (dbh) of 527 trees were measured. Linear regression and analysis of variance indicated that bark-thickness:dbh ratios differed between sites. Two hypothetical regression lines were constructed to represent what seemed to be, from the data, pure P. totara (a steep slope) and P. hallii (a shallow slope). At all sites, the actual thickness:dbh slope over all trees was intermediate between the hypothetical P. totara and P. hallii slopes. However, two sites seemed to be almost pureP. totara, perhaps with hybrids from a nearby stand of P. halliiin one case, and the other three sites comprised various mixtures of the two species, in many cases including likely hybrids. It was concluded that measuring bark thickness generally, but not infallibly, distinguishes the two species.

Keywords  bark thickness; Podocarpus; P. totara; P. hallii; sand dune; identification

B02075; Received 29 November 2002; accepted 21 November 2003; Online publication date 3 June 2004
New Zealand Journal of Botany, 2004, Vol. 42: 313-320
0028-825X/04/4202-0313 © The Royal Society of New Zealand 2004

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