New Zealand has been isolated from other land masses for so long a period that a vegetation has developed which has definite characteristics of great interest. Among these may be noted the large number of endemic species (those found only in New Zealand); the great number of species within certain genera (as species of Olearia); the absence or poor development of genera which flourish in Australia (Acacia); the number of plants with distinctive juvenile and adult forms (Pseudopanax crassifolium); the presence of some plants with affinities to plants in South America, South Africa, and Malaya (Hebe); the large number of hybrids within the genus (Nothofagus)and others; the divaricating growth forms of many coastal plants, as well as those from other habitats, and the cushion-like habit of alpine plants (Raoulia); and the large number of plants which have inconspicuous flowers, small, lacking in colour, and often unisexual (Coprosma). These are some of the main characteristics of the New Zealand flora of which the general aspect is that of large areas of dense forests with evergreen trees, scrub land with manuka, and a profusion of ferns, especially tree ferns.
The New Zealand Botanical Region consists of three principal islands: North Island, South Island, and Stewart Island, which lie between 34° 25' and 47 20' S. It includes also the Kermadec Islands (29° 15' – 31° 24' S) lying some 600 miles north-east of Auckland, the Chatham Islands (43° 35' – 44° 25' S) some 480 miles east of Christchurch, and the subAntarctic Islands, in six widely spread groups between 48° – 55° S and 159° – 179° E. The wide extent of latitude and altitude that is included in this region supports a great variety of conditions for plant growth. About 83 per cent of the species of flowering plants and all species of gymnosperms are endemic. Many of the lower forms of plants are also endemic, including about 35 per cent of the algae and ferns, and many of the liverworts, mosses, and lichens.
The date at which New Zealand became separated from any large land mass is very vague, but certainly it was in very early times as shown by the large number of endemic species. The flowering plants which show affinities with plants of the Malayan region, such as kauri, Aciphylla, and Carmichaelia, are quoted in support of theories of ancient land connections. It is impossible to reconstruct the nature and extent of this ancient vegetation, though much research has recently been done in Paleobotany. But it is evident that vegetative changes took place as ice ages came and went, and climatic conditions changed. By the time the Maoris began to occupy the country, they found vast areas clothed in dense forest. In the centre of the North Island, however, volcanic eruptions had caused widespread destruction of the forests, the charred remains of which may now be found beneath showers of pumice and ash. Again, Maori occupation, especially in the use of fire for clearing areas for cultivation and for hollowing out their canoes, resulted in further forest losses. It was inevitable that European settlement, accompanied by the introduction of mammals, had far-reaching effects upon the vegetative cover. The indigenous vegetation had developed without the presence of land mammals (except two species of bat), but in recent years many of those introduced by man have been responsible for a great deal of damage to the vegetative cover. Many of these animals such as deer, goats, opossums, and the like not only eat leaves and destroy undergrowth, they trample young plants and so prevent the natural regeneration of forests, but they also make possible the onset of soil erosion and the general destruction of landscape features on a large scale.
The distribution of plants in New Zealand is very restricted but this is not surprising when one considers how sudden within a short distance are the changes from sea level to snow line; how the high mountains cause a great variation in rainfall; and how varied are the soil and other conditions in sheltered valleys, on mountain screes, and on wind-swept shores. All types of habitat are found within short distances and each is occupied by distinct types of plants. Many of the plants found in the exposed coastal regions or in high altitudes are xerophytes. The vegetation of the North Island varies much from that of the South Island; it seems that Cook Strait forms a natural barrier to the distribution of many species. Two other definite boundaries seem to be 38° S latitude in the North Island and 42° S latitude in the South Island. In the forests of North Auckland, Great Barrier Island, and Coromandel Peninsula the kauri and taraire are dominant trees, but are not found below 38° S. Tawa is found in central North Island and to 42° S. Plants of general distribution throughout the country are manuka (Leptospermum scoparium) and bracken fern (Pteridium esculentum). A feature of the landscape is the wealth of tree ferns, and the profusion of other ferns within the shady forests has given rise to the use of a fern leaf as a national emblem.
The general aspect of vegetation is that of the conspicuous plants such as the flowering plants and conifers, and the ferns and lycopods. But of importance are the inconspicuous plants: the lichens of barren rocky regions, the mosses and liverworts of the humid interior of the forest, the fungi which are so often overlooked, and the algae both of sea and of fresh water.
The New Zealand forest is typically dark green in all seasons of the year and has little resemblance to forest of similar latitudes in the Northern Hemisphere. Deciduous trees, summer-green herbs, and annual plants are uncommon. Most of the canopy trees are evergreen with thick, tough leaves as Beilschmiedia tawa, B. taraire, and Nothofagus species. A few species of Fuchsia (Onagraceae), Sophora (Leguminosae), Hoheria (Malvaceae), and Aristotelia (Elaeocarpaceae), trees of shorter growth in the sub-canopy layer, have thinner leaves and show deciduous habit in varying degrees.
In lowland vegetation summer-green herbs are of little importance. In some areas are found small orchids (Thelymitra and Pterostylis) and in swampy areas Typha muelleri (fresh water swamps) and Scirpus americanus (salty swamps). In montane tussock grasslands are Coriaria spp., and in alpine meadows Ranunculus lyallii as herbaceous forms, while in higher altitudes on screes on the Southern Alps are found Anisotome carnosula (Umbelliferae) and Ranunculus haastii. In the sub-Antarctic Islands commonly found herbaceous plants are Bulbinella rossii (Liliaceae) and Pleurophyllum criniferum (Compositae). Allan noted the scarcity and unimportance of indigenous annuals.
A common habit of growth is found in divaricating shrubs, with densely tangled branches, small leaves, and inconspicuous flowers. Over 50 species show this habit, of which common examples are Plagianthus divaricatus of coastal salt swamps, Coprosma rhamnoides of forest, Melicope simplex of coast and forest, with Corokia cotoneaster and Sophora prostrata of open hillsides.
Mat and cushion forms of growth are characteristic of two endemic Compositae genera, Raoulia and Haastia, found mainly in the South Island. Large plants of these with their dense growth of leaves, thickly covered with white hairs, have been aptly termed “vegetable sheep”.
In swampy areas are toetoes (Cortaderia spp.), large clumps of native flax (Phormium tenax and P. colensoi), and cabbage trees with great tufts of sword-like leaves (Cordyline spp.).
Of plants showing distinct juvenile and adult forms there are some striking examples in New Zealand. Most noticeable among these is the lancewood (Pseudopanax crassifolium) of which the juvenile form has a slender stem with rigid deflexed leaves of leathery texture and sharply toothed margins, which may be 2 to 3 ft in length. The adult has a thick trunk with a crown of broad, short, erect leaves. The young trees of rimu (Dacrydium cupressinum) is an extremely graceful tree of drooping habit, with tiny leaves closely pressed to the stems, but the older tree is erect, with long straight trunk and a crown of larger leaves. Some plants when young have a divaricating habit, with small leaves, as Pennantia corymbosa and Hoheria angustifolia, but lose this habit in the adult stage and grow erect with larger leaves.
Another form of growth is seen in the tussock country where “bunch grasses” cover large areas. These are referred to as low and tall tussock, red and silver tussock, and snow tussock, and are species of Poa, Festuca, and Chionochloa.
Other areas are referred to as scrub country. These are often regions where forest has been destroyed by man, or by volcanic ash, and the dominant plants now are manuka, bracken fern, tauhinu (Cassinia), and plants of similar type. Where such an area is left undisturbed, especially by introduced animals, natural regeneration of native forest may take place.
Lianes and epiphytes, usually associated with tropical and subtropical forest, are found in great profusion. Climbing by various means are characteristics of such plants as species of Clematis(by means of twining stems or petioles),Tetrapathaea (by means of tendrils), supplejack (Rhipogonum scandens) (by twining), bush lawyer (Rubus australis) (by hooked spines), and the climbing rata (Metrosideros florida) and many ferns (by roots). The perching habit of growth, merely for a place to live, is common among mosses and ferns (Asplenium flaccidum), but there are also many flowering plants such as the perching lilies (Astelia spp.), the perching kohuhu (Pittosporum), and many orchids (Dendrobium and Earina). Some species of Metrosideros and Pittosporum begin life as epiphytes. Metrosideros robusta sends roots towards the ground, and is found later to have almost replaced the tree on which it has germinated. There are few parasites. Elytranthe tetrapetala (the scarlet mistletoe) and Loranthus micranthus (the common New Zealand mistletoe) are woody shrubs which live as semi-parasites. Dactylanthus taylori, pua reinga, is a unique plant which is a root parasite and has been found in the North Island on roots of Pittosporum, Nothofagus, and Coprosma. The parasitic and saprophytic habits are common among the fungi.
The majority of New Zealand plants produce flowers which are small and inconspicuous. The predominant colours are white and greenish, and in many plants the flowers are unisexual, the genus Coprosma illustrating all these points. Even in plants found elsewhere with coloured flowers, as the rose coloured Calystegia sepium, the flowers in New Zealand are white. In alpine flora the flowers are much more conspicuous but are mostly white or cream in colour. Of the gentians, which are of brilliant colours in other countries, there are 24 species which are nearly all pure white or faintly streaked with colour. In Auckland Islands and other sub-Antarctic islands there are flowers with brighter colours, and the gentians range from white to crimson on different plants.
In midsummer there are bright red flowers of pohutukawa (Metrosideros excelsa) and the southern rata (M. umbellata) and the dull golden blossoms of kowhais (Sophora species). There are a few winter-flowering trees such as Neopanax arboreum with small inconspicuous unisexual flowers, and Vitex lucens with dull red flowers.
A striking feature is the number of species, about 15 per cent, which have unisexual flowers; these are mainly dioecious. Nearly all species of the two genera Clematis and Rubus are dioecious, while in Cotula and Bulbinella this habit is found only in the New Zealand species of each genus.
The coastline of New Zealand extends from 4,000 to 5,000 miles, with a great variety of physical features, sandy beaches, gravel and boulders, rocky stormtossed headlands, and often stretches of sand dunes.
There are about 600 species of seaweeds, some always submerged, others in intertidal zones, which are in three main classes, each with a distinctive colour according to the place in which they live. Agar was previously imported from Japan, for its use in food preparations and for scientific work. Now agar is extracted from Pterocladia lucida and P. sapillacea from our own shores. Corallina officinalis is one of the red seaweeds that extract calcium salts from sea water and their tissues become impregnated with lime. Red seaweeds are submerged, the brown seaweeds occupy the next zone and very common is Hormosira banksii, like a string of beads, found in rock pools. Among the kelps are the giant kelp Durvillaea antarctica, the bull kelp D. utilis, and the bladder kelp Macrocystis pyrifera, which is washed up on shore by a storm. The green seaweeds are found in shallow water, exposed for long periods between tides and represented by sea lettuce (Ulva), the thick fleshy masses on stones formed by Codium adhaereus and Caulerpa brownii which resembles a twig of the tree rimu. The Maoris called this and other seaweeds by the name rimu.
Sandy shores are too unstable to support many plants. In sheltered places the shore convolvulus (Calystegia soldanella) and the shore buttercup (Ranunculus acaulis) are found. On rocky shores there is more variety; many herbaceous and semi-woody plants are found, with more restricted distribution. In the south are a native dock (Rumex neglectus, the bronze Gunnera and Crassula moschata. A few of the more widespread plants are the true flax (Linum monogynum), some hardferns (Blechnum species), a small sedge (Scirpus cernuus), the succulent glasswort (Salicornia), and the yellow-button (Cotula coronopofolia). “Wandering” sand dunes extend inland in some areas and only plants with long underground stems can withstand the constant movement of the sand. Where such are established they arrest the progress of sand which often threatens to invade farm lands. Shore convolvulus (Calystegia), pingao (Scirpus frondosus), and Spinifex hirsutus are useful for this purpose. Sand coprosma (Coprosma acerosa), two species of Pimelia, and the Cassinias form compact shrubby growth in some exposed areas.
Juncus maritimus var. australiensis and Leptocarpus simplex, either singly or in combination, may dominate salt swamps from the North Cape to Banks Peninsula. Further south Leptocarpus only is found.
The mangrove, Avicennia resinifera, is characteristic of muddy tidal estuaries of the North Island to 38° S on the east coast, but not so far south on the west coast. This is a very unusual plant with many peg-like roots and a seed that begins germination before it leaves the plant.
Certain trees form a narrow belt of coastal forest. The pohutukawa, Metrosideros excelsa, common in the north, reaches to 38° S; the karaka, Corynocarpus laevigatus, is in the South Island also and is abundant on the Kaikoura coast to about 42° S; the ngaio, Myoporum laetum, also extends to the South Island as far as Dunedin.
In the sheltered eastern harbours of Stewart Island and the Auckland Islands, the southern rata, Metrosideros umbellata, forms a coastal forest belt reminiscent of pohutukawa in the far north. Large-leaved composites are common on the coast in the south: Senecio reinoldi of Stewart Island, S. stewartiae and Olearia lyallii on the Snares, and O. lyallii in the north of Auckland Islands.
A remarkable group of endemic species with tropical affinities is found on the northern off-shore islands. Among these are Meryta sinclairii (Araliaceae), a large-leaved tree, abundant on Three Kings Islands and Hen and Chickens Islands and representing a genus centred on New Caledonia; Xeronema callistemon (Liliaceae), common on Poor Knights and Hen Islands, is related to X. moorei of New Caledonia. Elingamita johnsoni (Myrsinaceae), an endemic of about a dozen trees on West Island, Three Kings, resembles Tapeinosperma of New Caledonia. Tecomanthe speciosa (Bignoniaceae) is a woody climber related to T. hillii of Queensland, of which only one plant has been found on Great Island, Three Kings.
Plectomirtha baylisiana (Anacardiaceae), a single tree on Great Island, Three Kings, is related to Semecarpus of Indo-Malaya.
The first settlers found a large part of New Zealand covered by forest, but in areas such as North and South Auckland, the central volcanic plateau, and inland Hawke's Bay, burnings by Maoris or volcanic eruptions had resulted in extensive areas of grassland, fern, and scrub. Only in the drier parts of the South Island were there large areas of indigenous grassland at low elevations, and evidence suggests that a good deal of this had been in forest in the not-far-distant past. Forests are of two main types.
This is a sub-tropical rain forest in which growth is extremely luxuriant, with small trees, shrubs, ferns, mosses, and liverworts in abundance. The large canopy trees are evergreen, often clothed with epiphytes and festooned with climbing plants. Groves of tree ferns are a notable feature. Despite its tropical appearance, however, this forest does not compare with that of the tropics proper in diversity of tree species. The most important trees only can be mentioned here; none of them is found in the Campbell Islands, and only Metrosideros umbellata in the Auckland Islands where it appears as gnarled and stunted in growth.
The kauri – Agathis australis (Araucariaceae) – is perhaps the most famous timber tree of New Zealand. It is prominent in forests of North Auckland, the Coromandel Peninsula, and the Barrier Islands, extending to 38° S. The resin is of great value and the digging of kauri gum over large areas shows that these forests must formerly have been of much greater extent. Closely related are two species of Libocedrus (Cupressaceae): L. bidwillii, pahautea, and L. plumosa, kawaka, which are cypress-like trees with bark which falls in long thin strips. These are cone-bearing plants or gymnosperms.
There are representatives of three genera of Podocarpus in New Zealand, also cone-bearing plants and usually dioecious. Podocarpus totara is widely distributed and prominent in central North Island. Most of the totara in Westland is the closely related P. hallii which ascends to higher altitudes. P. spicatus, matai or black pine; P. dacrydioides, kahikatea or white pine; and P. ferrugineus, miro, are common in lowland forest.
Most other large forest trees belong to the flowering plants and include taraire, Beilschmiedia taraire, (Lauraceae), one of the commonest trees of the forest of North Auckland, which disappears at 38° S. Beilschmiedia tawa, also an important tree in North Island forests, occurs locally in the eastern South Island to 42° S.
Metrosideros genus (Myrtaceae) is represented by about 11 endemic species. The best known is M. excelsa, pohutukawa, which grows in coastal forests in the north, and also on Three Kings; it is often grown in gardens and parks for its showy red flowers. M. robusta, northern rata, overtops most forest trees in the North Island and extends to about Greymouth in the South Island. It begins as an epiphyte on a tree such as rimu; finally the host tree dies and the rata replaces it. The southern rata, M. umbellata, is important in montane forests in the South Island, especially in the west. Some species are climbers, with woody rope-like stems, such as M. scandens and M. perforata, which have a general distribution in coastal and lowland forests. Their flowers are red. There is also M. albiflora, the white-flowered species, found mainly in kauri forest. The Leptospermums, too, belong to this family; these are the manukas of lowland to montane marginal forests.
Weinmannia racemosa (Cunoniaceae), the kamahi, is the commonest forest tree, extending from about 38° S to Stewart Island, and is important both in lowland and in montane vegetation. North of 38° S is the less common W. sylvicola, tawhero.
Pittosporaceae is represented by some 25 endemic species, found mainly on the margins of forests. Pittosporum eugenioides (tarata, lemonwood), P. tenuifolium (kohuhu), and P. crassifolium (karo) are attractive trees which are often cultivated.
Of the family Araliaceae, Neopanax is a genus of trees and shrubs showing great variety in the form of leaves; N. arboreum is found in lowland forests throughout and N. colensoi in montane forest. Pseudopanax crassifolium (horoeka, lancewood) is remarkable for the difference between juvenile and adult forms. Schefflera digitata (patete) is another member of this family which is widely distributed.
There are about 45 species of Coprosma (Rubiaceae) which are nearly all endemic and unisexual. C. lucida (karamu) and C. robusta (also known as karamu) are very common in forest shrubland, and C. repens (taupata) is found mainly in coastal regions.
Other trees include Carpodetus serratus (putaputaweta), Aristotelia serrata (makomako, the wine-berry), Plagianthus betulinus (Malvaceae), Melicytus ramiflorus (mahoe, whitey wood, of the violet family), Fuchsia excorticata (kotukutuku or konini) with loose papery bark and small greenish flowers. Two species of Griselinia are endemic: G. littoralis (the broadleaf) and G. lucida (puka, the shining broadleaf), both of which are often epiphytic.
Common ground plants in forest areas are: Microlaena avenacea (Gramineae), Astelia nervosa (Liliaceae), Cardamine heterophylla (Cruciferae), species of Uncinia and Carex (Cyperaceae), Epilobium (Onagraceae), Nertera (Rubiaceae), Hydrocotyle (Umbelliferae), and Ranunculus. The floor of forest of this kind is covered by an abundance of ferns, mosses, and liverworts. The tree ferns Cyathea and Dicksonia have been mentioned. Other genera well represented are: Asplenium, Blechnum, Adiantum, Histiopteris, Hymenophyllum, and Grammitis.
Oliver (1930) listed 50 species in New Zealand which are habitually epiphytic and classifies them as follows: semi-woody pteridophytes 3, filmy ferns 20, tufted ferns 7, creeping ferns 5, succulent herbs 2, orchids 7, and the tussock plants Collospermum hastatum and Astelia solandri. Four shrubs as epiphytes are Senecio kirkii, Griselinia lucida, Pittosporum kirkii, and P. cornifolium. Also prominent are the following lianes and climbers: Freycinetia banksii (kiekie), Rhipogonum scandens (supplejack), and species of Tetrapathaea tetranda (passion-flower), Parsonsia (Maori jasmine), Rubus (bush lawyer), and Clematis. Of particular interest is a group of climbing species of Metrosideros, with a habit apparently unique in the Myrtaceae.
These may be dominated by one or more of the four native evergreen species of Nothofagus, often in association with certain podocarps. Beech species are not found on Stewart Island or Mount Egmont, and are also missing from a large segment of the west coast of the South Island. Beech forest may occur from sea level to timber line and in regions with rainfall as low as 25 in. per annum or as high as 250 in. per annum. Nothofagus truncata (hard beech) is the only species found north of about latitude 37°. It was common on islands in the Hauraki Gulf near Auckland and isolated patches are known in North Auckland. It is important in the Marlborough Sounds and western Nelson and reaches the Taramakau River in Westland. N. fusca (red beech) is closely related to N. truncata and extends from about 37° S to Lake Manapouri (45 ½ S). N. menziesii (silver beech) ranges from about 37° S to the southern limit of the genus in New Zealand and is the only beech found in the forests of the extreme south-east South Island. It is often found at timber line. N. solandri var. solandri (black beech) occurs at lower altitudes from near Lake Taupo to the northern half of the South Island, while N. solandri var. cliffortioides (mountain beech) tends to higher altitudes from the latitude of Taupo to the southern limit of the beeches, although absent from the Tararua Range.
Podocarpus hallii and Dacrydium cupressinum are podocarps commonly associated with beech forest.
The interior of Nothofagus forest is, in general, more open than that of podocarp-dicotylous forest. In wetter areas there is some undergrowth but in the driest forest there is very little vegetation under the dense canopy. Some shrubs and small trees commonly found are Pseudowintera colorata, Coprosma foetidissima and C. pseudocuneata, Neopanax colensoi and N. simplex, Phyllocladus alpinus, Myrsine divaricata, and small-leaved species of Pittosporum. Where there is sufficient moisture, bryophytes and ferns (such as a few species of Blechnum, Hymenophyllum, and Polystichum) carpet the forest floor, with herbaceous plants such as Nertera, Microlaena. There are few lianes or epiphytes, except mosses and lichens.
Climatic change: Holloway (1954) has shown that South Island beeches are invading new areas and that podocarps are failing to regenerate on many sites. He suggests that this was initiated about A.D. 1300 by a fall in mean or effective temperature, which gave the beeches a relative advantage over the podocarps. The long-living podocarps may still persist in situations now unfavourable to them.
Wardle (1963) suggests that climatic deterioration became most intense between A.D. 1600 and 1800, and that more recently increased regeneration of podocarps has occurred.
New Zealand is no exception to the general rule that the upper limit of continuous woody vegetation (usually formed here by species of Nothofagus) is lower in the Southern than in the Northern hemisphere at similar latitudes. In the Tararua Range the upper limit of the beech is lower than expected, with a belt of scrub above it. Zotov (1938) suggested that this depression of the beech is due to frequent fog formation. Most areas, however, where there is a wide belt of sub-alpine scrub lack beech altogether. This scrub can be an impenetrable barrier of prostrate trunks and stiff interlocking branches. The main type, classified by Cockayne (1928) as “shrubcomposite” scrub is dominated by species of Senecio and Olearia. Also common are Phyllocladus alpinus (mountain toatoa, celery pine), Podocarpus nivalis (mountain totara), Hebe spp., and divaricating shrubs such as Aristotelia fruticosa, Myrsine divaricata and Pittosporum divaricatum.
New Zealand is well isolated from other lands, and particularly from those with high and extensive mountain systems. These mountainous areas support some 500 species which do not extend to the lowlands.
The main diversity is in the South Island, but alpine vegetation is found throughout the North Island mountain chain and isolated patches occur in the Coromandel Range.
Composites are important in the alpine vegetation, and pride of place is taken by Celmisia, a predominantly herbaceous genus, of which there are some 58 species in New Zealand and one in Australia. In C. coriacea the lanceolate leaves are in large tufts, with a silvery pellicle and may be 60 cm long. At the other extreme the leaves of C. laricifolia are tiny and needlelike. Other composites are Helichrysum, Leucogenes (native edelweiss), Haastia, and Raoulia (vegetable sheep).
The largest genus of the Scrophulariaceae in New Zealand is Hebe, which is well represented at high altitudes. Particularly interesting are the “whipcord” Hebes with leaves reduced almost to scales – H. lycopodioides and H. cupressoides. Ourisia and Euphrasia contribute attractive species to the alpine vegetation. Other prominent genera are Gentiana and Ranunculus, the latter having an important centre of evolution in New Zealand. Most striking is R. lyallii of the Southern Alps with peltate leaves up to 24 cm in diameter and large inflorescences of white flowers.
In swamps are found plants which can survive in loose soil which is covered, more or less, by water; many of these plants grow also in drier conditions. Podocarpus dacrydioides may form swamp forest and Cordyline australis is also common under varying conditions. The New Zealand flax, Phormium tenax, raupo, Typha muelleri and Carex secta are most commonly found. Genera common to bogs include sedges, some ferns (Gleichenia), the rush (Hypolaena), Dracophyllum, Hebe, Dacrydium, and Leptospermum. In the bogs on the mountains and lowlands further south are plants of cushion bog type in which representatives of the genera Oreobolus, Phyllachne, Gaimardia, and Donatia are found. Most striking is the mangrove (Avicennia resinifera) a tree of twisted and gnarled stems, which grows in salty estuaries from North Cape to about 38° S. In ponds and slow-moving rivers are Potamogeton spp., water-milfoils (Myriophyllum), and water chickweed (Montia fontana). In addition there are many fresh-water algae, a very large group of plants, living in many different situations including scums on ponds or thread-like forms, one-celled plants, and those forms of blue-green algae which belong to the thermal regions.
The New Zealand native grasslands are dominated by species with the tussock or “bunch grass” habit. These have much mechanical tissue and do not die back to the ground in winter. Tussock grasslands are found from sea level to the alpine zone and fall into two broad categories. Low-tussock grassland is dominated by species of Festuca and Poa, a half-metre or more in height and yellow-brown in general appearance, and belongs to lower, drier areas. Talltussock grassland is dominated by one or another of the snow grasses (Chionochloa spp.), which are usually a metre or more high and yellow, green-brown, or red-brown in appearance. They are generally found today at higher altitudes and in wetter conditions.
Low-tussock grassland: About a century ago this community covered considerable areas of eastern South Island from sea level to 800–900 m and in many places invaded areas where beech forest had been cleared. Large areas of induced low-tussock grassland occur also to the east of the central plateau of the North Island.
A detailed study by Barker (1953) on Hunters Hills, South Canterbury, listed the dominants in low-tussock areas as Festuca novae-zelandiae (hard tussock), Poa caespitosa (silver tussock), and Poa colensoi (blue tussock). Hard tussock is the most abundant, it is deep rooted, and dominant on steep, exposed slopes. Silver tussock is shallow rooted, grows in more mesophytic conditions, and, unlike the other two, does not occur in tall-tussock grassland. The blue tussock grows with the other species and may be dominant locally on shallow soils. The spiny shrub Discaria toumatou (wild Irishman) and the Aciphyllas (spear grasses) are also common on low-tussock areas.
Tall-tussock grassland: Tall tussock communities are found on Mount Egmont and from there southward throughout the high country of both Islands, sometimes above forest. At lower levels tall tussock may be found on coastal hills, as on Banks Peninsula, or on the Southland Plain.
Chionochloa rubra (red tussock) dominates large areas in central North Island devastated by volcanic eruptions. In the South Island it is common on poorly drained terraces and abundant particularly in Southland. C. pallens and C. flavescens are important in the North Island mountain chain, and with C. rigida dominate in the South Island. C. crassiuscula is common in South Island mountains, and with C. pungens forms the meagre high-altitude grassland found on Stewart Island. In northern South Island C. australis, a lax species with smooth leaves, forms a slippery “carpet” grassland. The dominant species in the Hunters Hills tall tussock are C. rigida and the cotton plant, Celmisia spectabilis, with Festuca novae-zelandiae and Poa colensoi. The cotton plant has tufts of stout linear-oblong leaves with dense tomentum beneath, and a well protected growing point enabling it to survive forest fires. In inland North Otago a snow-tussock community of Chionochloa rigida, with Festuca matthewsii common, was described by Connor (1961).
The original tussock grassland evolved in the absence of grazing animals, and has been modified in greater or lesser degree during a century of stocking. In drier areas, such as Central Otago and inland Marlborough, the results have been serious. Here burning and stocking opened up the grassland, making an ideal home for rabbits. Their depredations accelerated vegetation changes which included spectacular increase of scab weed (Raoulia australis), a composite mat plant. Legislation has been introduced to control both burning and rabbits.
The vegetation of these islands is that of ferns, liverworts and flowering plants. On Kermadec Islands (29 15' – 31 24' S) are some 117 species, 12 per cent of which are endemic and 76 per cent found in New Zealand. In lower altitude dry forest are Metrosideros kermadecensis, Cyathea milnei, Myrsine kermadecensis, Coprosma petiolata, with Corynocarpus laevigatus and Myoporum laetum. In wetter forest above are Ascarina lanceolata, Cyathea kermadecensis, Rhopalostylis cheesemanii together with Melicytus ramiflorus.
The Chatham Islands (43° 35' – 44 25' S) support 257 species of which 14 per cent are endemic and 86 per cent grow in New Zealand. Two endemic genera are Coxella and Myosotidium. There are no podocarps or large trees on these islands. The karaka and nikau palm (Rhopalostylis sapida) are prominent with endemic species of Myrsine, Hebe, Olearia, and Senecio.
On the sub-Antarctic Islands there are about 193 species of which about 31 per cent are endemic and 63 per cent occur in the North or South Islands. Pleurophyllum, a large-leaved herbaceous composite, is the one endemic genus and there are three species.
The Snares (48° S) have Olearia lyallii and Senecio stewartiae forest and grassland dominated by Poa litorosa and Poa foliosa. On the Auckland Islands (50° 32' S) a narrow belt of Metrosideros umbellata coastal forest in sheltered eastern inlets is replaced by a tangled scrub of Myrsine divaricata, Cassinia vauvilliersii, Coprosma spp., Neopanax simplex, Dracophyllum longifolium, and stunted M. umbellata to about 300 m. Above this is Chionochloa antarctica grassland. Campbell Island (52° 22' S) has a belt of Dracophyllum scrub to about 130 m in sheltered situations, above which is Poa litorosa grassland. C. antarctica grassland, now diminished in area, is found on the floors of certain valleys. On Antipodes Island (49° 41' S) Poa litorosa is the dominant tussock, and of the 57 species only the three species of Coprosma are woody. There are no woody plants on Macquarie Island (54° 30' S), which supports only 31 species of flowering plants, three ferns, and one Lycopodium. Poa foliosa grassland is common.
by Eric John Godley, M.SC.(N.Z.), PH.D.(CANTAB.), F.R.S.N.Z., Director, Botany Division, Department of Scientific and Industrial Research, Lincoln.
Manual of New Zealand Flora, Cheeseman, T. F. (1925); The Vegetation of New Zealand, Cockayne, L. (1928); D.S.I.R. Bulletin No. 107 (1954), “An Ecological Study of Tussock Grassland”, Barker, A. P.; New Zealand Journal of Science and Technology, Vol. 19 (1938), “Some Correlations Between Vegetation and Climate in New Zealand”, Zotov, V. D.; New Zealand Journal of Science, Vol. 4 (1961), “A Tall-tussock Grassland Community in New Zealand”, Connor, H. E.; Journal of Ecology, Vol. 18 (1930), “New Zealand Epiphytes”, Oliver, W. R. B.; Ibid., Vol. 25 (1937), “A Consideration of the Biological Spectra of New Zealand”, Allan, H. H.; New Zealand Journal of Botany, Vol. 1 (1963), “The Regeneration Gap of New Zealand Gymnosperms”, Wardle, P.; Transactions and Proceedings of the New Zealand Institute, Vol. 42 (1910), “The Vegetation of the Kermadec Islands”, Oliver, W. R. B.; Transactions and Proceedings of the Royal Society of New Zealand, Vol. 82 (1954), “Forests and Climate in the South Island of New Zealand”, Holloway, J. T.; Descriptive Atlas of New Zealand, McLintock, A. H. (ed.) (1959), “Pre-European Vegetation of New Zealand”.