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Forest Vines to Snow Tussocks: The Story of New Zealand Plants



Most of Australia is much drier than New Zealand and as a consequence most Australian vegetation types and their floras are very different from ours.182,183 Vegetation types with counterparts in New Zealand — moist closed forests and open alpine communities — are restricted to the wetter and more mountainous eastern fringe of the continent and Tasmania. Even here it is estimated that prior to the arrival of man only about 1 per cent of Australia was occupied by closed forests and much less than that by alpine communities.

Closed Forests

These extend in scattered patches from north Queensland to Victoria and Tasmania. The closed forests without Nothofagus have been divided latitudinally into tropical, subtropical and warm temperate. The first is found in north Queensland and is characterised by leaves of mesophyll size; the second ranges from central Queensland to central New South Wales and has a predominance of notophylls (small mesophyll); and the last straddles southern New South Wales and eastern Victoria and is predominantly microphyllous.184 A number of the genera prominent in these forests are shared with New Zealand, for example Elaeocarpus, Beilschmiedia, Dysoxjlum, Syzygium and the vines Freycinetia, Ripogonum and Parsonsia, but in most cases there are many more Australian than New Zealand species. Woody vines and vascular epiphytes are conspicuous page 224in the more northern of these Australian forests, but are less common in the south at the same latitudes as New Zealand's North Island. In Queensland 'strangling' figs may occur as emergents and, in places, species of Agathis and the related Araucaria. In Queensland also the abundant nest epiphytes are ferns — species of Asplenium, Drynaria and Platycerium (Stags Horn Fern) — equivalent ecologically to the asteliad nests of New Zealand.

Closed forests where species of Nothofagus dominate or co-dominate are scattered through south-east Australia near the coast and Tasmania. In eastern Victoria and Tasmania the species involved, Nothofagus cunninghamii, is closely related to N. menziesii of New Zealand. Nothofagus moorei of montane sites in north central New South Wales and near the New South Wales, Queensland border also belongs to the 'N. menziesii group', but has larger leaves than either N. cunninghamii or N. menziesii.

As in New Zealand the Nothofagus forests in Australia have relatively few species and few or no lianes and vascular epiphytes. Several other tree species are often associated with Nothofagus including Ceratopetalum apetalum (perhaps the counterpart of Weinmannia of the same family in New Zealand) Atherosperma moschata and in Tasmania, the conifers Dacrydium franklinii and Phyllocladus aspleniifolius. Tree ferns are common, particularly in canopy gaps and gulleys.

Open Forest

In this category trees grow sufficiently far apart so their crowns do not form a continuous canopy and the ground as a consequence is not heavily shaded.

In tall open forest, also known as wet sclerophyll, very tall species of Eucalyptus are dominant. One of these, E. regnans, is the tallest flowering plant in the world, attaining a height of 100 m or more. Tall open forest is restricted to maritime south-east Australia, Tasmania, and a small area at the tip of south-west Australia. Where soils are relatively fertile, ferns predominate in the ground cover and where it is infertile, heath-like shrubs, belonging to the Myrtaceae, Proteaceae, Rutaceae and other families predominate. This forest type is restricted to fairly moist climates and perhaps in the absence of fire it would be succeeded by closed forest.

Low open forest occupies drier sites, sometimes further inland than those of tall open forest, in eastern, northern and south-eastern Aus-page 225tralia and Tasmania. Relatively short species of Eucalyptus predominate in the tree stratum together with species of other genera in the same family and other drought-resistant species such as the scale-leaved Casuarinas. On fertile sites, tall grasses form the ground cover and on infertile sites heath-like shrubs. Sometimes trees are absent and pure grassland or heathland results.

Tall Shrubland

In the southern parts of South and Western Australia there is a special type of shrubland known as Mallee. Here the dominant eucalypts are multistemmed and regenerate after fire from bulky woody tubers known as lignotubers. Generally inland from the eucalyptus-dominated communities, where climates are drier and soils infertile, drought-resistant species of Acacia, particularly A. aneura (mulga), prevail. The sometimes sparse ground cover comprises grasses and shrubs.

Hummock Grassland

Succeeding the Acacia shrubland in the arid heart of Australia is a grassland dominated by the prickly small tussocks of grasses, mainly belonging to the genus Triodia.

Chenopod Low Shrubland

In south central Australia on calcareous, sometimes semi-saline, soils there is a low shrubland where the salt-tolerant family Chenopodiaceae is strongly represented.

Subalpine and Alpine Communities185

Despite its size, the continent of Australia has generally low relief and it is only in the south-east and in Tasmania that mountains rise above treeline. The mountains are not of alpine form, but are basically raised plateaus with fringing scarps. Glaciation was extensive during the Ice Age in Tasmania and as a result there are more steep and rocky sites in the mountains there than on the mainland.

The zone 400–500 m below treeline is occupied by woodland dominated by a few small species of Eucalyptus (Snowgums). In Tasmania there are, in addition, thickets of a shrubby deciduous species of Nothofagus, N. gunnii, which belongs to the N. fusca group. Associated with page 226the Nothofagus are species of Athrotaxis, the only southern hemisphere genus of the conifer family Taxodiaceae.

Frosty valley floors below and above treeline are occupied by a tussock grassland with species of Poa, Danthonia and other genera.

Above treeline, particularly on the mainland, an important plant community is a herbfield of short grasses and such genera as Celmisia, Craspedia and Euphrasia growing on fairly deep, well-drained soils. Below persistent snow patches is an even shorter herbfield with species of Plantago, Neopaxia, Caltha and Ranunculus as in New Zealand. Less common on the mainland, but well developed in Tasmania is a shrubbery on rocky sites comprising genera shared with the heaths of the lowlands.

Poorly drained sites support bogs with Sphagnum moss, a variety of small shrubs, sedges and small species of Astelia. In Tasmania alone cushion bogs with species the same as or related to those of New Zealand are frequent. Species present include Donatia novae-zelandiae and Phyllachne colensoi (shared with New Zealand) and species of Oreobolus and Astelia.

Above snow patches comes a type of fellfield with low species of Coprosma and Colobanthus and, on wind-exposed rounded ridge crests, a different type with, among other genera, Chionohebe and Drapetes, which are also shared with New Zealand. From photographs the latter community looks not unlike the summit plateau fellfield of Macquarie Island.