Forest Vines to Snow Tussocks: The Story of New Zealand Plants
The Aucklands are the only islands in the New Zealand subantarctic with forest. Forest forms a narrow zone up to about 50 m above sea level on sheltered shorelines and is dominated by southern rata (Metrosideros umbellata) in association with Dracophyllum longifolium var. cockayneanum and Pseudopanax simplex. Undershrubs are Coprosma foetidissima (stinkwood), the Dracophyllum and Myrsine divaricata, while on the forest floor the ferns Polystichum vestitum, Asplenium scleroprium, and Blechnum page 208durum are abundant in places. Fuchsia excorticata has been recorded from one locality and the tree fern Cyathea smithii from several sheltered north-facing valley sides in the eastern inlets. The trees of this forest are unusual in that the lower parts of their trunks and branches are inclined or even prostrate as a result of wind action. Cockayne162 describes this very graphically: 'Everywhere are the massive prostrate and semi-prostrate trunks of the southern rata, sometimes lying close to the ground, at other times forming great arches, or at others again natural bridges over the deep depressions of the forest floor.'
At a few localities at the north-east tip of the main island and on adjacent islets there is also a coastal forest of the large-leaved Olearia lyallii. This species has increased its range in Port Ross over the past century and may have reached the Auckland Islands from southern New Zealand as recently as early last century.