The Vegetation of New Zealand
Chapter IV. — The Plant Communities
The Plant Communities.
1. Communities of Salt or Brackish Water.
a. The seaweed communities (by W. R. B. Oliver).
The rather sharp difference occasioned in the conditions of the littoral belt by the supply of water above and below low-tide mark is reflected in the nature of the algal coverings. Below low-tide level is usually a close growth of fairly tall brown algae with smaller species on and among them. Above this level only small species occur in closed or open formations. In each station is more than one association so that the two facies may conviently be termed "formations".
This formation extends from below low-tide mark up to the ordinary limit of low neap-tides. In exposed situations, however, it extends somewhat higher indicating that the daily supply of water is the controlling factor in its distribution. Generally there page 80is a growth of large species of brown algae forming a continuous vegetative covering. Beneath this tier is a lower stratum of smaller algae including many brown and red kinds while the rock-surface itself bears a covering of crustaceous and branched forms of coralline algae. According to the dominant species three principal associations, as below, are to be destinguished.
The Durvillea association is characterized by the presence of D. antarctica which is confined in its vertical distribution to the surf zone as a narrow belt generally about 1 m. wide (Fig. 6) with its upper level at low neap-tide mark. The upper margin of this belt is indeed marked by the large, placental holdfasts of the kelp. Durvillea itself extends from the Subantarctic Islands northwards as far as Cook Strait on the east to beyond Manukau Heads on the west. Below the Durvillea is a growth of smaller brown algae, including Marginaria Boryana, Lessonia variegata, Carpophyllum maschalocarpum, Cystophora retroflexa, and C, torulosa — all species ranging from 50 cm. to 1 m. high and provided with air vesicles. The undergrowth is composed af algae 20 cm. or so high, common members being Pterocladia lucida, Zonaria Turneriana, Glossophora Harveyi and Stypocaulon paniculatum. Beneath these on the rock-surface are various species of coralline algae, including branched forms, e. g. Amphiroa and Corallina, and encrusting species, e. g. Melobesia and Lithothamnion. Epiphytes are not uncommon, the most conspicuous being Porphyria subtumens (on Durvillaea) and species of Corallina (on Cystophora retroflexa).
The Carpophyllum association occurs from North Cape to Stewart Island, where Durvillea is absent, from neap-tide mark down. Carpophyllum maschalocarpum is dominant and associated with it are Lessonia variegata, Marginaria Boryana, Cystophora torulosa, C. retroflexa and, especially in the northern part of New Zealand, Carpophyllum plumosum, Ecklonia Richardsoniana and Sargassum Sinclairii; Xiphophora chondrophylla forms the upper margin. The undergrowth is similar to that of the Durvillaea association, the more common species being Melanthalia abscissa, Zonaria Turneriana, Caulerpa sedoides, Stypocaulon paniculatum and Glossophora Harveyi. The rock surface supports the usual coralline algae.
Xiphophora chondrophylla usually forms a narrow belt along the upper margin of the Durvillea and Carpophyllum associations, but if there be a nearly level rock surface at this height, this species may be regarded as the dominant member of a distinct association. On Otago Peninsula where it is well developed it has associated with it Lessonia variegata and Pachymenia lusoria. Beneath there is an abundant flora (including Codium adhaerens) and fauna.
Small emerging-algae formation.
Limited to the belt lying above low neap-tide mark the associations here grouped together are characterized by the small size of the species, the usual open nature of the community page 81and the presence of various devices1) for conserving moisture whilst exposed to the atmosphere. Various species are dominant in different tide levels and localities but the formation may be conveniently grouped into the following 4 subformations.
The coralline algae subformation is distinguished by the dominance of species of Corallina. With C. officinalis may be associated in small quantity Colpomenia sinuosa and other small algae or Hormosira Banksii, so that the two species are fairly evenly distributed2).
The small brown or red algae subformation has, as its principal association Hormosira3 dominant or sometimes pure. Scytothamnus australis and species of Apophloea also form associations on rocks between tide-marks.
The ulvoid-algae subformation includes two common species — Ulva rigida and Porphyra columbina — each forming associations and both agreeing in their possession of delicate, flat thalli thinly coated with mucilaginous matter. Porphyra inhabits exposed situations but Viva those more sheltered and subject to the influence of fresh water.
The small olive-red-algae subformation embraces two associations which occur high up in the intertidal belt and are made up of mossy algae belonging to the Rhodophyceae, though olive-brown in colour. They form low, close growths 2 or 3 cm. high and usually affect shady places. The one Bostrychia arbuscula is confined to the south of New Zealand but the other Carelacanthus spinellus is more widely distributed.
b. Zostera formation.
1 1) In the brown algae a dense outer layer; internal reservoirs in the internodes of Hormosira Banksii; the continuous central space filled with water jelly in Splachnidium rugosum; the slimy covering of S. rugosum and Codium adhaerens; the thin mucilaginous coat of Ulva and Porphyra.
2 In such a case Corallina affects wetter situations than Hormosira, so that frequently the former is found covering the bottoms of shallow pools while round their margins is Hormosira.
3 Fresh or turbid water filling the distended internodes of this plant is apparently not harmful for it luxuriates on reefs in muddy harbours.
4 There appears to be some doubt as to the species. Hooker referred a specimen from Auckland harbour to Z. marina L., remarking it was perhaps Z. angustifolia Roth. Graebner (Pflanzenreich. Potamogetonaceae: 31), cites only Z. capricorni Aschers., as occurring in N. Z., and doubts the occurrence of Z. tasmanica (p. 32). Cheeseman in both editions of the Manual gives the names as above, but is not certain as to the exact position of the deep-water plant.
c. Salt Swamp.
1. Mangrove (Avicennia) tidal forest or thicket.
This formation possesses but one species, Avicennia officinalis, the life-form of which has been described in chapter I of this Part. It forms girdles or patches of thicket or low forest between tide-marks in shallow estuaries, tidal rivers, sheltered bays and the like. It is restricted to the Auckland district and is to be seen in its greatest luxuriance in the extensive estuaries and tidal rivers of the North Auckland district and the Kaipara subdistrict (Fig 3.).
The presence of the formation depends chiefly upon the following: — A muddy substratum which, though generally deep, may be quite shallow and overlie rock; absence of frost; warmish water during summer; tide-erosion of insufficient power to uproot the young seedlings.
The substratum generally consists of an extremely soft and sticky mud light brown on the surface but at a little depth black, shiny and of evil odour. In places, very shallow pools of water, left by the retreating tide, lie on the surface of the water-saturated ground, which is everywhere honey-combed by the holes of crabs (Helice crassa), the orifices varying from 1.5 cm. to considerably less, and out of which water flows as one steps on the mud.
When growing in the greatest luxuriance, the trees, 9 in. or more high, form a close belt dull brownish-green in colour, bounding the shore of the estuary or even occupying the centre of the river-bed, the outer limit being-determined by the average low-water mark. At high tide, only the crowns of the trees are visible but, at low-water, the muddy floor is exposed and the spreading branches and bare trunks are visible. Everywhere the more or less limpet-covered, asparagus-like pneumatophores 1) rise up in thousands, projecting from the mud for a height of some 20 cm. on an average. Some are solitary, but others are more or less bunched together. Growing scattered amongst them are usually many young plants of Avicennia of all sizes, especially near the shoreward margin of the swamp.
2. The Salicornia formation.
1 1) These not only play a biological part, but strongly oppose tidal erosion and in many places, though very slowly, promote the deposition of mud and other riverborne matter, until eventually the swamp may be replaced by salt swamp or salt-meadow.
During spring tides the Salicornia is covered daily by the tidal water, the maximum time of submersion of the lowest part of the community being about 225 minutes and the minimum 50 minutes. Each month for a period of 14 days the lower part remains uncovered by water, but the higher part is uncovered for at least 24 days. Obviously, then, the Salicornia plants are subject to quite different conditions in relation to the amount of salt in different parts of the community and this, again, must be greatly affected by periods of heavy rain and the varying quantity of fresh water derived from streams flowing into the estuary &c. As for the substratum, sticky mud is hostile to Salicornia, and in such it may not grow at all. It especially favours sandy mud or well-drained muddy shingle, i. e. it cannot tolerate stagnation.
The community may be a mere fringe or at its maximum a broad carpet 100 m. or considerably more in breadth. Where fully developed, the plants grow into one another and the carpet is 15 cm., or more, in depth. Near the upper limit there is frequently more or less Suaeda maritima.
Where the tidal scour is not too strong the Salicornia traps the mud, which in time will accumulate sufficiently to raise the surface so far above the tidal waters as to allow invasion by other halophytes and eventually the etablishment of salt-swamp.
For many details in the foregoing account I am greatly indebted to Mr. P. G. Moffat, Harbour Master, Port Motueka (SN.). who has compiled a Tide Range Table for Port Motueka.
3. Juncus-Leptocarpus formation.
This well-marked formation is characterized by the strong dominance of the rush-form and the presence in large quantity of Juncus maritimus var. australiensis and Leptocarpus simplex, or the latter may alone be present.
The floristic composition of the formation consists of only 8 species (families 3, genera 6), of which there occur throughout: Scirpus americanus, S. robustus, Carex litorosa, Leptocarpus simplex and Plagianthus divaricatus.
The formation occurs on the floors of tidal rivers and estuaries where exposed to the highest spring tides and is present in all the Botanical Districts. Many of the swamps are extensive, e. g. near Havelock (SN.), Collingwood (NW.) and Invercargill (now more or less "reclaimed"), to cite only a few.
The substratum of Juncus-Leptocarpus swamp differs from that of page 84Mangrove in that it is much firmer and less muddy. The soil may be clay, loam, sand or mixtures of these; shells of certain molluscs are abundant and the surface is riddled with the holes of crabs. The community is only covered by water at the highest spring tides and then merely for a brief period. The water with which the ground is saturated is brackish and there is a maximum of salt that can be endured but though no minimum is demanded by the species, yet, if the water be too fresh, the halophytes coming into competition with ordinary swamp-plants (e. g. Typha, Phormium) cannot hold their own.
The general physiognomy of the association depends upon the dominant rush-form. Seen from a distance, it presents a dark even surface, but usually the Leptocarpus is slightly taller than the Juncus, while the Scirpus forms greener patches. Perhaps 70 to 80 cm. might be considered the usual depth of the vegetation. Growing on the driest ground, and not exposed to salt-water, except at exceptionally high tides, is a girdle of the dark-coloured rounded bushes of the divaricating-shrub, Plagianthus divaricatus, 90 cm. high or less. Landwards of this comes salt-meadow. Leptocarpus and Juncus form pure girdles or clumps, but which is the more salt-tolerating, I do not know, since in different localities, either may form the seaward girdle. Here and there in the main mass of the association are tussocks of Carex litorosa. Cladium junceum is common in the North Auckland district. Where deep pools occur, there is abundance of Scirpus robustus and with it S. americanus. Near the junction of salt-swamp and salt-meadow, various species of the latter come in, especially Salicornia australis, Apium filiforme, Selliera radicans and Cotula dioica.
Where the community occupies the shallow portion of a tidal river one bank has probably been eroded and sediment deposited near the other on which, if the tidal scour be not too great, various halophytes become established from seeds brought by birds or the water itself, or vegetative portions deposited by the tide. Later on, some of the soil-particles, continually brought by the water, are held between the plants themselves and their shoots, together with the products of decay, so that the surface is gradually raised and the swamp slowly transformed into salt-meadow. Earlier on, the Mangrove, Zostera and Salicornia formations, catching and holding the mud, may prepare the requisite conditions for Juncus-Leptocarpus swamp. The first plant to appear is Scirpus americanus, which, even after the taller members are established, holds its own on the wetter ground, thanks partly to its power of increase by means of the far-spreading rhizomes. Eventually, the taller close-growing Juncus or Leptocarpus excludes the light and the Scirpus is doomed.
The ground on which the formation occurs, if drained, is suitable for occupation by pasture, as in the case of a portion of the great salt-swamp near Invercargill.
4. Various minor communities.
Mimulus repens association.
Where sluggish streams flow through salt-meadow, but not in every locality, this association occurs. Usually, there is a fairly deep, flowing portion of the stream and a shallow sluggish part, this latter caused by a sligth overflow. In the shallower part, M. repens1 may be dense enough to hide the water. Through it may grow some Scirpus americanus, Triglochin striata var. filifolia and perhaps a little Cotula coronopifolia. In the deeper part there is Scirpus robustus with an undergrowth of more or less Mimulus. Greater stagnation of water soon brings in Cotula coronopifolia with floating stems, and the other plants are absent.
Scirpus lacustris association.
As the water of the shallow tidal river becomes far less salt, a girdle of the tall rush-like Scirpus lacustris2, 1.5 m. or so, in height, fringes the bank, but in the South Otago, Stewart and perhaps Fiord districts the association is absent. Although not depending in the least upon the Scirpus, Plagianthus divaricatus frequently forms a girdle — often indigenous-induced — on the landward side of the former, its dark hue contrasting with the green of the Scirpus.
Brackish-water submerged communities.
Ruppia maritima forms submerged masses of filiform stems and leaves on the floor of lagoons &c. and slowly-flowing streams in somewhat brackish water.
Althenia bilocularis, a smaller plant of similar life-form, also occurs in some localities on the east of the South Island under identical conditions.
Zannichellia palustris, another ecologically-equivalent species, occupies similar stations to the above.
2. The Salt-meadow Group of Communities.
a. Salt-meadow proper.
This may be defined as a close turf made up of low-growing herbs, out of which rise certain plants of the rush-form and the divaricating-shrub Plagianthus divaricatus.
1 1) A prostrate perennial herb with stout, succulent, creeping, rooting stems; prostrate or suberect branches and small, obtuse, entire succulent leaves, 4 mm. long.
2 The species also occurs on margins of lakes &c, at some considerable distance from the sea, ascending to 450 m., according to Cheeseman (1906: 778).
Salt meadow is common along the coast from north to south of the main islands but rare in Stewart Island. It usually occurs on ground subject to an occasional slight flooding by brackish-water, or on wind-swept slopes &c. liable to occasional drenching by sea-spray, but it may lie quite out of reach of water containing salt in excess. In winter or after heavy rain, pools lie everywhere on flat meadows. The soil may vary from clay to sand. None of the species seem to be dependant upon excess of salt in the substratum, though such is generally the case.
The life-forms of the species are as follows: — divaricating-shrub 1, grass-from 2 (summergreen), rush-form 3, herbs and semiwoody plants 11 (creeping and rooting 7).
The composition of salt-meadow is fairly uniform throughout New Zealand proper, but there is no regularity as to dominance of any particular species. Juncus maritimus var. australiensis, Leptocarpus simplex or Plagianthus divaricatus may be abundant in places, and probably, prior to the settlers fires, were more plentiful still, but the physiognomy of the meadow depends not on the rush-form, but on the presence of a close and even turf made up of the far-creeping perennial herbs Selliera radicans, Samolus repens and Cotula dioica. Equally abundant, indeed at times dominant, is the succulent Salicornia australis, and the summer-green grass Atropis stricta is also very common.
1 1) One or other of the jordanons of Cotula dioica is present, but in the south of the South Otago district and Stewart Island this compound species is represented by C. pulchella and C. Traillii. So, too, the extremely common Atropis stricta is represented in the above localities by A. Walkeri. Other species frequently present in salt-meadow are Suaeda maritima (wettish places), Eryngium vesiculosum, Atriplex patula (exotic). In some places the exotic Lepturus incurvatus and Plantago Coronopus form pure colonies, looking exactly as if indigenous.
b. Coastal-moor and allied communities.
Coastal moor proper consists of turf formed by a combination of various ordinary creeping-rooting halophytes, together with certain coastal ferns and low-growing plants of a subalpine-subantarctic character.
The species number about 44 (families 24, genera 32) of which the most important are: (halophytes) Salicornia australis, Samolus repens var procumbens, Selliera radicans, Cotula pulchella; (subalpine-subantarctic) Blechnum durum, Agrostis muscosa, Scirpus aucklandicus, Rumex neglectus, Montia fontana, Myosotis pygmaea var. Traillii, Euphrasia repens, Asperula perpusilla, Plantago Hamiltonii.
Coastal-moor is confined to the south of the South Otago1) and the Stewart districts and perhaps the Fiord district. The presence of the community depends upon a sour peaty soil, as substratum, the result of the subantarctic character of the climate plus the nature of the plant-covering2). The habitat is also exposed to showers of sea-spray, so that there will be a greater percentage of salt in the soil than in the case of boggy ground in general. Water frequently lies in pools and some of these are permanent.
The life-forms are well in keeping with the habitat, consisting as they do of: — turf-making herbs 23, rosette plants 13 (including 2 ferns), tussocks 4 and cushion-plants 4.
1 1) The most typical moor is on the west of the Bluff Peninsula to the south of Ocean Beach. Unfortunately this unique piece of primitive New Zealand is now so altered by the presence of stock as to be no longer the spot described in my notes before it became a grazing-ground. Smaller examples occur on the coast-line of Foveaux Strait and on some of the small islands therein.
2 That is to say, certain species occupy the ground, thanks to the favouring climate, these form peat and species more peat-tolerating still, enter in, and intensify the oxylophytic conditions.
On the low flat sandy ground to the west of the New River Estuary, the association is allied to coastal-moor, on the one hand, and dune-hollow, on the other; Euphrasia repens, Plantago Hamiltonii, and Claytonia australasica, represent the moor, and Gunnera arenaria, Geranium sessiliflorum, Selliera, Acaena novaezelandiae, A. microphylla var. pauciglochidiata and its hybrids with A. novae-zelandiae and Raoulia apice-nigra the dune-hollow1)
3. Sea-shore Communities.
a. Sandy Shore2).
Wide wind-swept stretches of sandy beach are frequently destitute of plant-life, the lower shore being washed by the sea, while the upper loose sand above high-water mark is the sport of the wind. Specially high tides too extend far beyond the average limit, and the undiluted sea-water is detrimental to the well-being of land-plants. Notwithstanding this, the dune-plants, Spinifex hirsutus, Desmoschoenus spiralis and Carex pumila creep over the loose sand, or build hillocks.
1 1) In some places Nertera Balfouriana (usually a mountain plant) is fairly plentiful, and there also occurs (restricted to a very small area) Gunnera Hamiltonii which had not been seen since its discovery 44 years ago until C. S. Smith recently found it in abundance growing on rather moist sandy ground on the seaward side of the Oreti River (SO.)
2 The plant-covering of sandy shores can hardly come into a category by itself but more properly belongs to unstable dune. Nevertheless it seems best to deal with it separately, partly because it is a distinct feature of the coast-line, and partly because it appears to be the sole station for Atriplex crystallina.
b. Beach of loose stones.
The formation (if it may be so called) occupying a beach of loose stones is open and includes many more or less distinct communities all of which are marked by a combination of the usual shore-line halophytes, together with shrubby and herbaceous mat-plants, which may be non-coastal.
The number of species found on these beaches is certainly not less than 88 (families 36, genera 63), and may be considerably more. The following are common, wide-spread species: — Deyeuxia Billardieri, Festuca littoralis, Carex ternaria, Leptocarpus simplex, Phormium tenax, Muehlenbeckia complexa, Salicornia australis, Mesembryanthemum australe, Tetragonia expansa, Scleranthus biflorus, Ranunculus acaulis, Acaena novaezelandiae, Oxalis corniculata, Linum monogynum, Pimelea prostrata, Samolus repens var. procumbens, Apium prostratum, A. filiforme, Calystegia Soldanella, Lobelia anceps, one or other of the species of Cassinia, Cotula dioica and its allies.
The formation is common along the coast, the substratum being supplied in part by shingle carried by currents and tide and cast upon the shore.
Beaches of this class offer different conditions according to size of stones, state of consolidation and amount of sand present. Between sand and gravel there is merely a question of degree, so that coarse sand and fine, gravel beaches have much the same plant-covering. Where the stones are large enough to be called shingle, the conditions approximate to those of lowland river-bed, excepting that the latter has usually a greater water-supply and more available soil between the stones, while the spray-factor is absent. But, as will be seen, certain river-bed species do occur on some shores though generally well back from the sea. Sand frequently fills up the spaces between the stones and so dune-plants enter into the associations. In the South Otago, Fiord and Stewart districts the semi-subantarctic climate leads to the formation of peat, which, collecting between the stones, encourages the settlement of species of coastal moor. This is intensified where the substratum is gravel.
The life-forms of the species for the formation as a whole are as follows: mat-plants 33 (woody 14), creeping herbs 8, tussocks 12, erect herbs or semi-woody plants 10, rosette plants 7, grass-like creeping 5, tufted grass 4, sand-binders 2, erect shrubs 4, cushions 2, Yucca-like 1.
Where the boulders are largest, vegetation is the most scanty, the commonest plants being the halophytes, Apium prostratum, Calystegia Sol-page 90danella and Senecio lautus. this latter through its strong plasticity being able to respond rapidly to change of conditions. Further from the influence of the waves, there may be Phormium tenax, Scirpus nodosus, and excepting south of about latitude 44° Mariscus ustulatus and Lobelia anceps.
The terrace bounding the shingle shore, being both more stable and less halophytic, possesses a more varied plant-covering. P. tenax, either in clumps, or as a continuous belt is a fairly common feature. On Cuvier Island it is mixed with Arundo; in South Canterbury it forms for a considerable distance a more or less continuous girdle; at Big Bay and Paringa (South Westland), this belt is so near the sea that, in rough weather, it arrests the floating driftwood. Muehlenbeckia complexa, as a mat-plant, is a common feature of terraces or high foreshores, and such mats favour the settlement of other plants e. g. Rhagodia nutans, Linurn monogynum, Senecio lautus, and at the present time certain introduced species. The following are some of the more common species of shingle or boulder terrace: — Pteridium esculentum, Scirpus nodosus, Carex testacea, Acaena novae-zelandiae, Oxalis corniculata, Linum monogynum, Euphorbia glauca, Pimelea prostrata, Leptospermum scoparium, Apium prostratum, Dichondra repens, Cassinia leptophylla or retorta according to latitude.
On the terrace of the Nineteen Mile Beach (E.) where the Canterbury Plain and Pacific Ocean meet, as well as many common species of such a habitat, are mats or low cushions of Raoulia lutescens and open circular mats — grey and green respectively — of the leafless, rush-like Muehlenbeckia ephedroides and a prostrate epharmone of Carmichaelia subulata. The Muehlenbeckia also occurs on shingly shore near Cook Strait where when sand comes in there are low cushions of a variety (unnamed) of Raoulia australis and stiff mats of the usually erect shrubs Coprosma propinqua and Plagianthus divaricatus. As for the associations of fine gravel in a semi-subantarctic climate the following list gives some idea: Scirpus aucklandicus, Carex pumila, Urtica australis (Dog Island, Foveaux Strait), Muehlenbeckia complexa, Rumex neglectus, Tetragonia expansa, Chenopodium glaucum, Atriplex crystallina, Lepidium tenuicaule (root very long), Tillaea moschata, Ranunculus acaulis, Geranium sessiliflorum, Myosotis pygmaea var. Traillii, Cotula pulchella, C. Traillii.
The most important matter connected with the development of the vegetation dealt with above is the role of mat-plants — more especially shrub-mats — in trapping seeds and functioning as seed-beds. At the present time this power is potent in bringing exotic species into parts of the habitat not exposed to sea-spray. Amongst such may be noted Holcus lanatus, species of Bromus, Hordeum murinum, Silene anglica, various herbaceous Leguminosae, Anagallis arvensis, Sherardia arvensis, Sonchus arvensis and other composites.
The vegetation of an extensive dune-area consists of several distinct plant-formations or parts of such, yet all are treated here under one head, partly for convenience and partly because the various habitats are the result of topographical change, each leading in distinct sequence to the next.
The total number of species for the whole dune-area is about 150 (families 50 genera 100) of which some 50 are common. The following are virtually confined to dune-areas, sandy shores or small sandy spots: (shrubs) Pimelea arenaria, Coprosma acerosa, Cassinia retorta (but now of wider range through the influence of the settler); (herbs) Ranunculus recens (vr.), Euphorbia glauca, Gunnera arenaria, G. Hamiltonii, Calystegia Soldanella; (grass-like) Spinifex hirsutus, Deyeuxia Billardieri, Desmoschoenus spiralis, Festuca littoralis, Carex pumila; (small rushlike) Heleocharis neo-zelandica. Excluding Stewart Island, about 61 species extend throughout. The following species of considerable range, but not of necessity extending throughout, are abundant: Spinifex hirsutus, Arundo conspicua, Festuca littoralis, Mariscus ustulatus, Scirpus nodosus, Desmoschoenus spiralis, Carex ternaria, C. pumila, Leptocarpus simplex, Cordyline australis, Phormium tenax, Libertia peregrinans, Scleranthus biflorus, Muehlenbeckia complexa var. microphylla, Acaena novae-zelandiae, Oxalis corniculata, Pimelea arenaria, Leptospermum scoparium, Gunnera arenaria, Centella uniflora, Lilaeopsis novae-zelandiae, Euphorbia glauca, Coprosma acerosa, Lobelia anceps, Selliera radicans, Cassinia leptophylla, Cotula dioica.
Dunes are the most common of New Zealand coastal land-forms and occupy no less than 127000 hectares while they extend inland in some places for a distance of 12 km. The most extensive areas are on the west coast of North Island but considerable dunes also occur on the east and north of South Island and the west of Stewart Island, the area for both islands, (9700 hectares) being still considerable.
The plant-covering of the dunes is fairly uniform throughout New Zealand, Lord Auckland and Kermadec Islands excepted, but certain latitudinal changes are evident due partly to climatic and partly to historical causes. Desmoschoenus, Deyeuxia Billardieri, Festuca littoralis, Euphorbia glauca and Coprosma acerosa occur on most of the unstable dunes. Spinifex hirsutus extends but a short distance past lat. 42°; the ecologically-equivalent species of Cassinia (retorta, leptophylla, fulvida) are each in the order given the dominant or sole form in the northern Central and Southern botanical provinces. Pimela arenaria, common on dunes in both the main islands, is represented in the South Otago district and Stewart Island by P. Lyallii. A variety of Geranium sessiliflorum is abundant on semi-stable dunes in the South Otago district and Stewart Island, but absent page 92elsewhere. Certain species of Raoulia are confined to particular localities and conditions.
Since dune phenomena are the same the world over it would serve no purpose to supply details regarding the making of dunes, nor need anything be said concerning the ecological conditions of the habitats. There is the usual foredune, the dune-complex and the wandering-dune, but there is every transition from an area possessing every dune feature, and with "Sand mountains" 60 m. high or more, to small hillocks on a sandy shore. In some parts of Taranaki and Auckland, cliffs, themselves often consolidated dunes, face the ocean, while at high-water there is no exposed beach at their base. Such are capped by enormous deposits of sand which are not infrequently advancing inland.
Dune-vegetation exhibits a gradual procession of events in harmony with the increasing stability of the substratum, the foredune marking the unstable commencement and the fixed inland sand-hill the stable climax. Stages also occur where a new class of associations branches off that may be merely transitory or become permanent, their persistence depending upon the stability of the dune-area as a whole.
Sand grass dune.
This is distinguished by the presence of one or both of the powerful sand-binders, Spinifex hirsutus ((Fig. 8) or Desmoschoenus spiralis, nor need there be any other species.
In North Island and the north of South Island where both plants are present they rarely intermix, while their characteristic colours, — silvery (Spinifex), yellow (Desmoschoenus), plainly indicate which dominates, giving the dune also a special physiognomy. S. hirsutus does not extend inland for any distance, but Desmoschoenus occurs, wherever there is drifting coastal sand. Near Foveaux Strait Festuca littoralis is an early comer, and sometimes a primary dune-builder. Occasionally, the tufts of Spinifex or Desmoschoenus form a close covering, but usually there are more bare patches than vegetation. At certain places on the west coast of the Ruahine-Cook district a very uniform foredune, looking like an artifical embankment, extends for several kilometres at a time covered with Spinifex (Fig. 8).
As sand-grass dune becomes more stable, thanks to its occupation by the major sandbinders, Calystegia Soldanella, Deyeuxia Billardieri, Festuca littoralis and Scirpus nodosus gain a footing and probably also some of the sand-tolerating shrubs. The rarer Euphorbia glauca belongs to the same association. In Stewart Island, Sonchus littoralis may be present. Calystegia Soldanella often covers the sand completely with a shining green mantle. Low dunes of that kind persist for a considerable time, the dune itself acting as a solid obstacle thus causing a protecting wind-trough to be formed between itself and the advancing sand.
This is distinguished by the dominance of certain sand-page 93collecting shrubs, together with various erect ericoid shrubs, the sand-collectors being the essential feature.
The dominant species are Pimelea arenaria (P. Lyallii in South Otago and Stewart districts), Coprosma acerosa and one or more (according to the locality) of the species of Cassinia. The following are early members of the association: Deyeuxia Billardieri, Festuca littoralis, Scirpus nodosus and Calystegia Soldanella.
The physiognomy of the association depends upon the open cushionform and yellow hue of the Coprosma (the Pimelea is far rarer and frequently wanting) and the grey or yellow Cassinia (according to the species).
At a greater distance from the sea, or when exposed to weaker sand-advance or erosive wind-action, the above shrubs will form a closed covering and may be reinforced by others, especially Leptospermum scoparium. The great tussocks of Arundo conspicua (Fig. 9.), and the huge tussock-like, green masses of Phormium tenax and P. Colensoi are frequently present, the latter being common in the North Auckland district. There too, Leptospermum ericoides and Leucopogon fasciculatus not erect but forming spreading mats, are abundant.
This, the climax of constructive dune-building, frequently lies far back from the sea, and is of considerable age and perhaps denotes a rising coast. In places where the wind strikes obliquely, or is not frequent, fixed-dune may lie just behind the foredune.
The sand is covered by a much more cohesive humus-containing layer of blackish sand than is that of unstable dune. It is sometimes as much as 30 cm. in depth, formed from the decay of many generations of plants.
At the present time, the vegetation is much modified but three distinct groups of associations stand out distinctly enough — grassland, shrubland and fern (Pteridium) heath.
The grassland, no longer primitive, consists of many exotic grasses and Leguminosae together with (North Island) the indigenous Microlaena stipoides and forms of Danthonia semiannularis and D. pilosa. Zoysia pungens is common in northern localities, but generally where there is less loam.
The shrubland consists of one or more of the species of Cassinia and Phormium tenax, Arundo conspicua, Microlaena stipoides, Biscaria toumatou, species of Carmichaelia and Scirpus nodosus are common members in many localities. On the northern shore of Foveaux Strait certain species of Acaena are abundant and there are many silvery patches of Raoulia australis and R. apice-nigra; tussocks of Poa caespitosa also are plentiful. Pimelea Lyallii replaces P. arenaria, and other plants not found on dunes further north are Geranium sessiliflorum (a dune variety), Wahlenbergia congesta and Gnaphalium trinerve.
Hollows and sand-plains.
An advancing dune-ridge leaves, in its wake, flat sandy ground which may continue to be further hollowed out by wind-page 94action, until moisture rising from the water-table damps the surface-sand and stops further sand-movement. Such a hollow is quite stable and ready for occupation by non-psammophytes.
The final destiny of such areas does not depend upon their plant-covering but on the stability of the adjacent dunes. Thus one of two things may happen, — there may be an invasion of sand and reversion to dune-conditions, certain associations arising only to be destroyed, or there may be a long stage of stability and a succession of associations culminating in a climax-association, two of which — swamp and swamp-forest being ordinary lowland communities are not dealt with here.
The primary groups of associations. Frequently the first arrival on the damp sand is Gunnera arenaria (creeping and rooting herb forming circular patches, 8 cm. to 2 m. diam., of small rosettes of thick, pale-green or brownish leaves flattened to the ground). Scirpus cernuus, Ranunculus acaulis, Epilobium Billardieranum, E. nerteroides, Lilaeopsis novae-zelandiae and especially Carex pumila are characteristic. Lobelia anceps, Limosella tenuifolia and Myriophyllum Votschii in North Island and northern dunes of South Island. Should there be no incoming of sand the following common halophytes next occupy this non-halophytic station: the species and hybrids of Apium, Samolus repens var. procumbens, Selliera radicans, Cotula coronopifolia, C. dioica and one or more of its near allies. Finally, colonies of the rush-like Leptocarpus simplex may take complete possession of the ground1) Should the hollow not become moist, Carex pumila early takes possession, increasing at a great rate through its far-creeping rhizome. A rapid drift favours Spinifex which quickly builds multitudes of low, rounded mounds.
The secondary groups of associations. Generally at some distance inland but occasionally just beyond the foredune, the sand-hollows may be closely coveredby shrubland with Leptospermum scoparium dominant (Fig. 10.). In the North Auckland district, and southwards for some distance, many species of the gumland shrubland are present, especially Leptospermum lineatum, Pomaderris phylicaefolia, Leucopogon fasciculatus, L. Fraseri, Pimelea prostrata and abundance of Cassinia retorta; also there will be more or less of both species of Phormium — but not usually in the same locality — and Arundo conspicua. On the northern shore of Cook Strait, Leptospermum scoparium often forms a closed association, especially where the surface is wet, when certain swamp-plants will be present, e. g. Heleocharis Cunninghamii Carex ternaria, Potentilla anserina var. anserinoides and Coprosma propinqua. In the Eastern district, in addition to abundance of Leptospermum scoparium, there is more or less Discaria toumatou.
1 1) On the north shore of Foveaux Strait Raoulia australis is plentiful, Pimelea Lyallii builds small sand-filled cushions, rosettes of the sand variety of Geranium sessiliflorum are here and there, Ranunculus recens (also EW.) occurs locally and in the North Auckland district Heleocharis neo-zealandica forms slightly raised patches.
Ancient sandhills occur in the South Otago district near the Bluff Estuary and along the lines of the ancient straits of Stewart Island. The Bluff dunes are separated from the estuary by Sphagnum bog (now almost gone). They are covered with Danthonia Raoulii var. rubra and the following non-dune, frequently subalpine plants are present: — Blechnum penna marina, Lycopodium fastigiatum, Gaultheria perplexa and Helichrysum bellidioides. The Stewart Island dunes bear a heath-like vegetation, including Leptospermum scoparium (dominant), Gleichenia circinata (abundant), Pteridium esculentum, Lycopodium ramulosum, the creeping subalpine podocarp Dacrydium laxifolium, Cladium Vauthiera, Phormium Colensoi, Enargea parviflora, Leucopogon Fraseri, Pentachondra pumila and Coprosma repens. The high-mountain character of this combination is remarkable.
Forest is rare on the dune-areas. Swampy sand-plain may occasionally contain Podocarpus dacrydioides forest. Various coastal and inland-coastal trees occur in dune-gullies and sheltered hollows in the North Auckland district, Kaipara subdistrict, and on the north shore of Cook Strait, e. g. — Macropiper, Knightia, Corynocarpus and Myoporum. On the lee-slopes of the high western dunes of Stewart Island, there is a luxuriant low forest in which Griselinia littoralis and Metrosideros lucida dominate. Very similar forest occurs on the dunes in the south-east of the South Otagb district. On the ancient dunes near the Ruggedy Mts., Stewart Island, according to Poppelwell (1913: 283) there is Dacrydium cupressinum-Weinmannia forest. On the dune-area facing Foveaux Strait westwards of the Oreti River there was formerly much forest consisting of close-growing, stunted Podocarpus totara and P. spicatus. Remnants remain in sheltered hollows, and, even in the open in places where the forest was cut down, it is naturally reinstating itself with P. totara in the form of much-branched spreading bushes.
5. Rock and Cliff Vegetation.
1 1) It is not easy to draw the line as to true coastal-rock formations. Thus, at Jackson Bay, Westland, there is an isolated rock, only to be reached at low-water, 3 to 4 m. high, on the flat top of which grows a collection of forest mesophytes, while in peat, on its face, is a dense mat of Enargea, a denizen of wet subalpine, or sometimes lowland forests.
Rock-surfaces are common on the coast and vary from high vertical cliffs, their bases washed by the waves, to flat sea-worn rocks hardly raised above the water. According to the nature and aspect of the rock most diverse stations are available for plant-life. On a vertical wall of hard rock with an even surface exposed to a maximum of salt-spray, there are no plants except a few lichens, but a sheltered rock in a rainy locality, with many cracks, crevices and ledges where soil can lodge, will support a rich vegetation.
Although rock associations are at first open, rooting-places are so limited in area, that there may be keen competition between the early comers. The soil-making ability of the plants may have much influence upon the ultimate composition of the association, certain peat-formers being able to furnish a soil of considerable depth and great water-holding capacity. Chasmophytes cannot gain a footing, until there be sufficient soil in the cracks or crevices. This may consist of small rock-fragments and sand weathered in situ, or blown soil. Accumulations, 2.5 to 5 cm. in depth, are quite frequent. The seedlings must be able to tolerate periods of drought. Succulency, thick coriaceous leaves, prostrate and rosette-forms are frequent and advantageous. Often the roots form a mat, as with certain rock-ferns, while even long roots may at first extend laterally along a fissure.
b. The Mesembryanthemum group of associations.
This group is distinguished by the dominance of Mesembryanthemum australe which may be virtually pure or have associated with it various halophytes, or if in a position less exposed to sea-spray, non-halophytes enter the associations. Probably all the really important species for the whole group of associations are mentioned in what follows.
1 1) Perhaps Arthropodium cirrhatum, Anisotome flabellata, Hebe obtusata and Celmisia Lindsayi come into this category.
2 Besides true coastal chasmophytes, the rock-vegetation includes more inland species than any of the other shore formations. Even lianes are not wanting, their sub-xerophytic structure, such as it is, being of advantage for the severe conditions of the open.
With less spray, other plants enter in and Mesembryanthemum becomes of decreasing importance. Rocks of many shapes, the outcome of much weathering, standing at various distances from the water, obviously offer much more varied conditions than a high wall-like cliff, and so possess a richer flora. The following are frequently present: — Polypodium diversifolium, Cyclophorus serpens, Arundo conspicua (especially in the north), Poa anceps var. condensata, Agropyrum multiflorum, A. scabrum, Scirpus cernuus, S. nodosus, Cladium Sinclairii (north), Leptocarpus simplex, Phormium tenax, Muehlenbeckia complexa, Rhagodia nutans (but not south of Banks Peninsula), Colobanthus Muelleri, epidium oleraceum, Tillaea moschata (south), Linum monogynum, Coriaria sarmentosa, Pimelea prostrata1), Leptospermum scoparium, Samolus repens var. procumbens, Lobelia anceps (south to Banks Peninsula and Okarito), Selliera radicans, Lagenophora pumila, Sonchus littoralis, and one or other of the species of Cassinia2
c. Pohutukawa (Metrosideros tomentosa) cliff.
1 1) There are one or two other species of Pimelea, including the badly-understood P. Urvilleana, but the taxonomy of this group needs careful revision, based on field study.
2 The following are restricted in distribution: — Hymenanthera crassifolia (vicinity of Cook Strait to the South Otago district but apparently absent on west coast of South Island); H. obovata and its hybrids with the above (both sides of Cook Strait); the series of hybrids of which the so-called, species" Coprosma Kirkii is based on specimens from different localities in the north of the North Auckland district (at different points on the North Island coast, but probably in far more localities than have been recorded.) The group, in its entirety is almost certainly a hybrid swarm with C. propinqua as one of the parents and perhaps C. retusa as the other, but possibly other species are concerned.
3 Metrosideros tomentosa is common along the coast of North Island from Three Kings Islands to lat. 39° on the west but not quite so far on the east. Inland it occurs on the shores of several lakes (VP.) and has been reported from Lake Waikare moana (E.C.)
In fairly sheltered positions the combination of species is considerable but with increase of wind and spray only the true coastal plants remain. Astelia Banksii 1 in pure colonies may be plentiful on rock-faces. Peperomia Urvilleana 2, both epiphytic and rupestral, is frequently abundant. The ferns Asplenium lucidum, Polypodium diversifolium and Cyclophorus serpens are often common. Arthropodium cirrhatum may be so abundant as to cover the rock with greenery for many square metres. Mats of Poa anceps var condensata are characteristic and various shrubs and other life-forms are represented 3
d. Associations with Phormium Colensoi dominant.
Phormium Colensoi4 is a common feature of high or low cliffs of the East Cape and Ruahine-Cook districts, whence it extends along the coast of the Sounds-Nelson and North-eastern districts and by way of the west coast of South Island — P. tenax also frequently coastal — to Stewart Island. Certain fairly well-marked communities may be distinguished as follows:
Hebe macroura association.
This well-marked association of a more or less open character is distinguished by the abundance of Hebe macroura 5 and the presence of the rather tall, semi-woody plants Senecio Banksii and S. Colensoi.
1 1) The thick, stiff, linear, tapering leaves, 1.4 m. long, dark-green above and silvery beneath are in great tufted masses. Thick masses of dead leaf-bases surround the living leaf-sheaths and function as a waterholding and food-containing apparatus.
2 A succulent herb with glabrous, very thick, orbicular leaves ± 8 mm. long and far-creeping, rooting stems.
3 Coriaria arborea, Leptospermum scoparium, Pseudopanax Lessonii, Hebe macrocarpa, H. salicifolia, Olearia furfuracea and Brachyglottis repanda may be more or less common, and so too, Arundo conspicua, Phormium tenax, Rhagodia nutans, Mesem-bryanthemum australe with its accompanying halophytes, as well as other coastal forest or scrub plants, according to the degree of shelter.
4 The coastal plant differs somewhat from the subalpine forms. The leaves crowded and bunched together are about 1.4 m. long by 9 cm. broad, the lower half of each is erect, owing to the sides of the blade being pressed together, but the upper half droops downwards. When P. tenax is also present there will most likely be more or less hybrids which betray their origin in forms of capsule ranging between the erect blunt capsule of P. tenax and the drooping, twisted, acute, longer one of P. Colensoi.
5 A shrub of spreading, drooping habit, the stems leafy near the extremities only, the leaves moderate-sized, rather broad and the flowers white and sweet-scented. Ecologically similar is Hebe salicifolia var. Atkinsonii of the neighbourhood of Cook Strait and the Marlborough Sounds.
The dominant Hebe may grow through the numerous mats of Poa follosa var. condensata and hang down the face of the cliff. Various coastal herbs and semiwoody plants and shrubs are present2 For a list of the species see Cockayne, L. 1916: 207–208. The Hebe is closely related to H. Cookiana. Also here may come the vegetation of the cliffs (lava conglomerate) to the south and probably the west of Mount Egmont. On these Phormium tenax is common; the other species are: Adiantum affine (widespread on coastal rocks in general), Blechnum durum (the first record for North Island), Poa anceps, Poa species related to P. pusilla, Scirpus cernuus, Macropiper, Mesembyanthemum, Melicytus rami-florus, Gunnera strigosa (characteristic), Apium, Samolus, Hebe as above, Plantayo BaouMi, P. Masonae, Coprosma retusa, C. propinqua X retusa?, Selliera, Lobelia anceps, Gnaphalium trinerve, Senecio lautus, Sonchus littoralis. In sheltered gullies H. macroura is erect and it is associated with one of the jordanons of H. salici-folia (with which it is almost certain to cross), tall Arundo conspicua, Phormium Colensoi and Coriaria arborea or sarmentosa.
Hebe salieifolia var. Atkinsonii association.
This is distinguished by the presence — often in abundance — of the above Hebe, together with various halophytes. There are certain distinct subassociations, two of which are dealt with here.
The quasi-mountain subassociation is distinguished by its mountainlike facies due to the presence of common mountain species or to such as resemble plants of that character3 The community occurs on cliffs in the south of the Ruahine-Cook district and, the more shady and soil-containing the habitat, the greater the number of species and the denser the growth Festuca multinodis forms dense mats and, in addition to the species of the footnote and the Hebe, there is abundance of Cyclophorus serpens, Asplenium flaccidum, Polystichum Richardi, Mesembryanthemum australe, Linum monogynum and Wahlenbergia gracilis. Increase of light leads to the outgoing of many species, but shrubs and certain forest plants4 enter in.
1 1) For a list of the species see Cockayne, L. 1916: 207–208. The Hebe is closely related to H. Cookiana. Also here may come the vegetation of the cliffs (lava conglomerate) to the south and probably the west of Mount Egmont. On these Phormium tenax is common; the other species are: Adiantum affine (widespread on coastal rocks in general), Blechnum durum (the first record for North Island), Poa anceps, Poa species related to P. pusilla, Scirpus cernuus, Macropiper, Mesembyanthemum, Melicytus rami-florus, Gunnera strigosa (characteristic), Apium, Samolus, Hebe as above, Plantayo BaouMi, P. Masonae, Coprosma retusa, C. propinqua X retusa?, Selliera, Lobelia anceps, Gnaphalium trinerve, Senecio lautus, Sonchus littoralis.
2 Scirpus nodosus, Apium prostrafrum, Samolus and probably other halophytes, Lobelia anceps, Lagenophora pumila, Cassinia leptophylla, Senecio Banksii, S. Colensoi and Sonchus littoralis.
3 Especially Festuca multinodis, Aciphylla squarrosa, Raoulia australis (in driest stations), Plantago Raoulii (form with broad, thick leaves), Pimelea subimbricata, Myo-sotis Forsteri (rare), Craspedia maritima, Senecio lagopus and, of course, Phormium Colensoi itself.
4 For instance, Brachyglottis repanda. On isolated rocks near Cape Turakirae — RC. (Aston, 1912: 212, the usually epiphytic orchids Dendrobium Cunninghamii (as a thick mat), Sarcochilus adversus and Bulbophyllum pygmaeum are present.
e. Coastal-fern association.
This is distinguished by the presence and frequent dominance of Blechnwn durum and Asplenium obtusatum while B, Banksii may be common.
The association is of a subantarctic character. It occurs in the South of South Island and Stewart Island where the climate favours the making and accumulation of raw humus but is hostile to the well-being of most species; in consequence the community is clearly defined.
In addition to the ferns, the following are generally present: — Myosotis ' albida (coastal herb with thick, soft, hairy leaves ± 10 cm. × 5 cm., in erect rosettes), Hebe elliptica more or less prostrate is common, but it is a chasmophyte so not dependant on peat, tussocks of Poa Astoni (± 30 cm. high, leaves rolled, rigid, green, almost pungent), Tillaea moschata (a spraytolerator). The last named is one of the pioneers and a soil-maker. As the soil becomes abundant various coastal-moor species gain a footing, especially Scirpus aucklandicus, Gentiana saxosa, Plantago Hamiltonii, and. Cotula pulchella, together with the usual halophytes.
f. Rocky shore vegetation.
The vegetation of fairly flat, rocky shores is generally rather a mixture of distinct communities in miniature than a defined association. Thus, owing to unevenness of surface, besides pure rock there are depressions where soil or water can accumulate and tiny salt-meadows, swamps and pools with aquatics are dotted about.
1 Coriaria sarmentosa, Leptospermum scorparium, Suttonia australis, Shawia pani-culata, Brachyglottis.
2 Adiantum affine, Polystichum Richardi, Asplenium lucidum, Poa anceps, Scirpus nodosus, Arthropodium (abundant), Astelia Solandri, Freycinetia, Peperomia Urvilleana, Macropiper excelsum, Pittosporum cornifolium (on the ground), Corynocarpus, Dodonaea viscosa, Hymenanthera obovata, Metrosideros robusta, M. Colensoi, Griselinia lucida, Apium prostratum, Solatium aviculare, Coprosma robusta.
g. Rock associations of local occurrence.
Sand-eroded rock, north coast of Cook Strait.
Between the Rivers Waitotara and Wangaehu much rock, at a short distance from the coast, has been cut into fantastic forms by wind-borne sand, an extremely xerophytic station being thus provided. The association consists partly of dune-plants (Festuca littoralis, Coprosma acerosa) and partly of semi-subalpine species (Raoulia australis, Pimelea prostrata). In some places south of the R. Wanganui are larger, flatter rock-surfaces on which are the remains of perhaps a rather ancientplant-covering consisting of Myoporum laetum, Dodonaea viscosa, the small forest-tree Suttonia australis and the divaricating, frequently subalpine Corokia Cotoneaster.
Where the rock is cut to a base-level a flat stony desert results. The rock-floor is strewn with sand-worn stones and there is a thin covering of small gravel and coarse sand. Pimelea prostrata and Coprosma acerosa are dotted about everywhere in equal numbers (Fig. 12), and, in the lee of the latter, there is generally a tongue of sand (Fig. 13). Silvery cushions of Raoulia australis occur here and there; Spinifex and Desmoschoenus form lines where the sand is finest; there are colonies of Zoysia pungens and yellow cushions of Scleranthus biflorus.
Celmisia semicordata association.
This occurs a little to the north of lat. 42° (NW.). At one spot near the coast the prevailing westerly wind, hemmed in by two adjacent headlands, strikes the summit of the cliff and its immediate vicinity with especial force. In consequence, the subtending girdle of forest is first dwarfed and then broken through. The rocks at a little distance from the edge of the cliff possess a plant-covering physiognomically more like that of subalpine rocks than of the coast. The moist climate favours the formation of peat on the rock; possibly a certain amount of spray is carried by the wind but it must be soon washed from the soil. The subalpine Celmisia semicordata is abundant. Other plants present, frequently subalpine, are: — Oreobolus pectinatus, 0. strictus, Phormium Colensoi, Pimelea longifolia, Cyathodes empetrifolia, Olearia avicenniaefolia and Senecio bellidioides. Several plants of the adjacent heath are present and stunted forest-trees and lianes; the coastal element is represented by Asplenium obtusatum, Scirpus nodosus, Plantago Hamiltonii and Senecio rotundifolius.
Celmisia Lindsayi association.
This is confined to cliffs in the South Otago district from Nugget Point southwards. The cliffs and rocky slopes, where there is soil or debris, are occupied by Metrosideros lucida forest, page 102Leptospermum thicket or Hebe elliptica-Phormium tenax scrub. The Celmisia association is quite distinct from those. It is situated on the solid rockface, (Fig. 14) or the youngest debris, and so is the first of a series of associations terminating in forest. Celmisia Lindsayi (Fig. 15), forming circular patches 90 cm. or more diam. is dominant. Anisotome intermedia, its leaves 76 cm. or more in length, is a companion plant, -but seems to prefer the debris as a station. Tussocks of Poa Astoni, on the rock, ancT Hierochloe redolens, on the debris, complete the association. Further to tho south, the Celmisia may be absent, but the Anisotome continues on cliffs to beyond Curio Bay.
Cliff-vegetation, west coa-t of Stewart Island.
The vegetation of these cliffs is worthy of mention because it includes Celmisia rigida and Anisotome flabellata, two endemic Stewart Island plants. C. rigida grows in peaty ground on the summit of the cliffs. The Anisotome is a chasmophyte confined to rock. Its roots are of an extraordinary length. The pale-green, pinnate, thick, fleshy leaves, 2.5 cm. long, are in small rosettes, which, pressed closely together, are flattened to the rock. Neuter of the species is purely coastal.
The readily weathered greywacke on both sides of Cook Strait, and of the islands therein, forms in many places" screes which in their physical conditions greatly resemble the debris fields ("shingle-slips") of the high mountains, but the climate being vastly more equable, and the surface of the screes more stable, the vegetation is far richer, nor does it include any highly specialized species restricted to the habitat.
On the northern shore of Cook Strait the scree has an open plantcovering as follows: Poa caespitosa (where most consolidated), Muehlenbeckia complexa var. microphylla (as a mat), Acaena novae-zelandiae, Epilobium novae-zelandiae, Aciphylla squarrosa, Calystegia Soldanella and some exotics.
On Kapiti Island (Cook Strait) the screes are frequently quite bare but in places they support an open association the chief members being the above Muehlenbeckia, Arundo conspicua and Cassinia leptophylla. (Fig. 16.)
On the Sounds-Nelson coast facing Cook Strait, there may be Myoporum laetum (far broader than its height), Dodonaea viscosa and the Muehlenbeckia.
6. Coastal Scrub.
By "scrub" is meant throughout this book a close growth of compact shrubs or stunted trees, one or both, in which dense life-forms, particularly the divaricating, the ball-like, and the rhododendron-form (shrub-composite) play a major part. In "shrubland", on the contrary, the community may page 103be more or less open, the life-forms more yielding, less dense and with branches more slender and more twiggy in character. Shrubland when low may quite well be designated "heath".
The number of species, not counting those of stunted forest, is about 41 (families 18, genera 23). The following are especially common on some part or other of the coastline: — Phormium Colensoi, Freycinetia Banksii, Urtica ferox, Muehlenbeckia australis, M. complexa, Pittosporum crassifolium, Melicope simplex, Melicytus ramiflorus, Dodonaea viscosa, Leptospermum scopgrium, Metrosideros perforata, M. scandens, M. lucida, M. tomentosa, Dracopfyyllum longifolium, varieties of Hebe salicifolia, H. elliptica, Myoporum laetum, Coprosma lucida, C. retusa, C. crassifolia, Olearia operina, 0. angustifolia, 0. Colensoi, 0. Solandri and Seneeio rotundifolius.
The life-forms and number of species to each fall under the following heads: — Trees or tall shrubs stunted to dense, dwarf or medium shrubform 15, lianoid cushions 4, liane forming entanglements on ground 1, ericoid shrubs 4, rhododendron-form 6, divaricating-form 3, giant tussockform 2, bushy but dense shrubs 4, open rather straggling shrub 1, dracophyllum-form 1.
b. Tree-composite scrub.
The following, apart from the two species of Olearia, are the principal constituents of both associations: Phormium Colensoi, Leptospermum scoparium, Metrosideros lucida, Dracophyllum longifolium, Hebe salicifolia var. communis, Hebe elliptica, × H. ellipsala, Olearia Colensoi and Senecio rotundifolius.
The Senecio rotundifolius association.
1 1) A tall shrub or even low tree up to 3 m. high or more but frequently prostrate in part. The numerous, stout, rigid, naked branches covered with smooth brownish bark spread widely and form, through their final branching, a rounded head of stiff branchlets covered with the large round leathery leaves, bright shining green above but beneath clad with buff tomentum.
2 0. angustifolia and 0. operina are-extremely closely-related species of exactly the same life-forms, being either low trees with a dense, broad, hemispherical crown (Fig. 17) or tall shrubs with more or less erect or far-spreading horizontal branches, furnished with coriaceous, more or less lanceolate leaves ± 8 cm. long, covered beneath with white tomentum and arranged in semi-rosettes at the extremities of the stiff branches. The large flower-heads have with ray-florets, but the disc-florets are yellow in 0. operina and purple in 0. angustifolia. The latter when in company with 0. Colensoi gives rise to a polymorphic hybrid swarm the forms of which almost exactly intermediate between the two are the false species 0. Traillii
Where the wind strikes with greater violence, Leptospermum scoparium appears and increases in amount with increase of wind-intensity, becoming by degrees of lower stature until, as a wind-shorn shrub, it takes the front position on rocky headlands (Fig. 2). On the other hand, where there is complete shelter the Senecio sub-association is absent, the mesophytic small forest-trees, shrubs and ferns coming to the front.
The macrocephalous Olearia association.
Dominance of Olearia angustifolia or of 0. operina apparently denotes a more exposed station than does that of the Senecio. There are two distinct subassociations with 0. angustifolia or 0. operina dominant respectively.
Olearia angustifolia coastal scrub is strongly xerophytic, a condition demanded by its position on headlands (Fig. 17) and islets fairly in the track of the frequent, violent, cold subantarctic gales, which, at times spray-laden, strike the plants and saturate the shallow, porous soil1 The community is common on the most exposed parts of the coast of the Stewart district; there is also a small piece at the base of the Bluff Hill. Seen from a distance, the scrub is defined by its sage-green colour. Where most exposed, it consists of 0. angustifolia and 0. Colensoi2 with perhaps a few plants of the hybrids between them and on certain islets Senecio Stewartiae. Generally, the shrubs are prostrate, but the branches eventually curve upwards. Within there is a tangle of rigid stems. The coastal ferns are the sole, but distant floor-plants.
1 1) It is astonishing how, in such a station, where nanism would appear the response requisite, thick, stiff, tomentose leaves, in rosettes, rigidity of branches and a dense globular life-form, permit the presence of small trees and, in the case of 0. Colensoi, broad leaves, 18 cm. long.
2 This may be identical with 0. Lyallii of the Subantarctic Province, the leaves being far larger than in 0. Colensoi of the high mountains.
A transition between Senecio and Olearia scrubs occurs at Mason Bay and on Codfish Island. The general character is much as already described, but the sage-green colour is relieved by green patches of Griselinia littoralis, especially at some distance from the sea. Where sufficient light penetrates, there are great colonies of Stilbocarpa Lyallii, which spread for many metres, thanks to its vegetative increase by means of arched runners. The bright-green, shining, thin leaves, each 30 cm. or more diam., stand on long stalks, 90 cm. above the ground.
Olearia operina coastal scrub is confined to the Fiord district. It is distinguished by the presence of 0. operina and the absence of 0. Colensoi and, when in its more sheltered positions, a greater abundance of forest mesophytic trees or shrubs1 which latter may form a distinct girdle. Its northern limit appears to be Big Bay (F.).
c. Hebe elliptica scrub or thicket.
At various localities in the Otago fiords, on the shores of Foveaux Strait, in Stewart Island and in a modified form at Otago Harbour, there is a scrub in which H. elliptica2 dominates, but it is more open wherQ the spreading H. salicifolia var. communis occurs, and then there will be form after form of × H, ellipsala.
At the base of the Bluff Hill, besides H, elliptica 1.8–2.4 m. high, Olearia drborescens, Nothopanax arboreum, Fuchsia excorticata and Aristotelia serrata are more or less common, and there are × H. ellipsala and Melicytus lanceolatus. Beneath the shrubs are Astelia nervosa var. sylvestris and the coastal ferns.
On the larger of the Open Bay Islands, in one place, at any rate, is a scrub of H. elliptica (a large-leaved form) 4 m. high, over which climbs Muehlenbeckia australis while beneath is Astelia nervosa var. sylvestris, Histiopteris incisa and Asplenium obtusatum. The soil is deep, coarse peat.
1 1) Principally Pittosporum fasciculatum, Coriaria ruscifolia, Aristotelia serrata, Fuchsia excorticata, Nothopanax Colensoi and Pseudopanax crassifolium var. unifoliolatum. Hebe elliptica, H. salicifolia var. communis and X H. ellipsala are extremely common. Just above the salt-swamp at the head of Doubtful Sound the community is about 3.6 m. high. In addition to the species already mentioned, it contains juvenile Dacrydium cupressinum and Podocarpus totara, Plagianthus divaricatus, Carmichaelia arborea, Myrtus pedunculata and Suttonia divaricata. The slender branches are covered with mosses and Hymenophyllum sanguinolentum and Nothopanax Colensoi is an epiphyte. Such a community is far removed from scrub and is rather incipient forest,
2 Hebe elliptica in its, typical" form extends all along the west coast of South Island with its northern limit in North Island west of Mount Egmont. On the east coast of South Island it does not reach lat. 45°, but it reappears in the Marlboroug-h Sounds (rare) and as var. crassifolia reaches Kapiti Island and one place on the north shore of Cook Strait.
d. Liane scrubs.
This is distinguished by a more or less pure close growth of the usually root-climbing Freycinetia Banksii, its rigid stems raised but little above the ground and forming an entangled mass. The community occurs in rocky places all along the west coast of South Island and is especially common close to high water-mark in the Fiord district. Its richest development is on the more northerly of the Open Bay Islands (W.), growing on hard calcareous rock. There it is about 2 m. high and of an extreme density. The stout stems each 12 cm^ circumference, bearing an abundance of thick, yellowish-green, sword-shaped leaves, are twisted in all directions, and interwoven, thus forming a rigid entanglement. The density is often increased by an admixture of the lianes Muehlenbeckia australis and Calystegia tuguriorum.
At the bases of sea-cliff gullies of the North-western district a subassociation occurs distinguished by the presence of Melicytus ramiflorus, Coprosma lucida, Olearia avicenniaefolia, Senecio rotundifolius and Seneciq elaeagnifolius, and if the two last are growing in proximity there will also be the hybrids between them.
In certain localities where hillsides slope shorewards (RC, SN., Banks Peninsula &c.) there may be many cushion-like rounded or pyramidal bushes of Muehlenbeckia complexa var. microphylla the dark, wiry stems intertwined. Such liane-shrubs are dotted about or intermingle.
Scrub consisting of M. australis occurs on the more southerly of the Open Bay Islands (W.). The plants, sometimes mixed with the fern Histi-opteris incisa, grow into one another making close thickets.
Liane-scrubs frequently denote the existence of former forests, and in the case of the Open Bay Islands afford strong evidence of an earlier connection with the mainland (Cockayne 1905 c: 373, 374).
On the beach near Nugget Point (SO.), there is a thicket of the shrubby nettle, Urtica ferox together with the ferns Pteridium esculentum and Hypolepis rugosula and the shrubs Melicytus ramiflorus and Fuchsia excorticata, Muehlenbeckia australis binding the whole into a close mass. A similar scrub, but with fewer nembers, occurs on Centre Island, Foveaux Strait and probably on some of the other islands of the Stewart district.
e. Forest scrub.
Forest scrub consists of communities made up of trees dwarfed by fairly intense coastal conditions, especially wind. Where the latter is particularly intense the scrubs are of extreme density and may be termed "wind-scrub", but this ecological class is not always coastal. Between tall forest and wind-scrub there are many transitions, while the effect of the wind is plainly visible in the shorn crowns of the trees forming a dense page 107canopy sloping shorewards. A good many kinds of trees1, both coastal and inland enter into forest-scrub communities. Lianes are usually abundant either binding the dwarf trees closely together or themselves become shrubs pure and simple. Beneath the thick canopy herbaceous ferns and even tree-ferns may be present. Here a few special associations are alone dealt with.
The North Cape.
Where exposed to frequent wind there is a forestscrub with an epharmone of Phyllocladus trichomanoides, 1.2 m. to 1.8 m, high (Cheeseman, 1897: 363) together with Pittosporum umbellatum, Melicope simplex, Pseudopanax Lessonii and the shrubs Pittosporum pimeleoides and Corokia Cotoneaster.
Metrosideros tomentosa scrub.
M. tomentosa, dwarfed to ± 1.8 m. high, is dominant. The community occurs at many points of the coast of the Auckland districts, especially at the base of wind-swept cliffs (Fig. 21). For instance, below the cliffs of the Waitakerei Hills, (SA.) growing on a stony terrace in a shallow clay soil, is a scrub of the following composition: — M. tomentosa (dom.), Cordyline ausfralis, Macropiper excelsum, Pittosporum crassifolium, Corynocarpus laevigata, Pseudopanax Lessonii, Coprosma grandifolia, C. retusa, Brachyglottis repanda.
1 1) The following may be cited but the list is far from complete: Podocarpus totara, P. spicatus, Phyllocladus trichomanoides, Nothofagus cliffortioides, N. Solandri, Carpodetus serratus, Edwardsia microphylla, Melicope simplex, Dysoxylwn spectabile, Coriaria arborea, Pennantia corymbosa, Dodonaea viscosa, Melicytus ramiflorus, Leptospermum scoparium, Metrosideros lucida, M. tomentosa, Griselinia lucida, G. littoralis, Dracophyllum longifolium, Suttonia australis, Myoporum laetum, Coprosma retusa, Olearia augustifolia, Brachyglottis repanda.
2 Rangitoto Island is an ancient volcano situated in the Hauraki Gulf, more or less circular in form, about 6 km. diam. and from its centre rises the scoria cone some 270 m. high surrounding which is an extensive lava-field made up of blocks of scoria of all sizes piled upon one another and full of gullies, hollows and chasms. There is no visible water on the island, the rain passing at once through the open substratum, though some must be absorbed by the porous rock. Notwithstanding the apparently inhospitable nature of the habitat, more than 180 species of indigenous spermophytes and pteridophytes occur on the island, and although bare patches are frequent enough, there are notmerely rock-plants present but both open and closed scrub and even forest Every stage of plant-colonization also can be seen, from occupation of rock by lichens, liverworts, mosses and even Bymenophyllaceae, to actual forest. But on the island generally the trees remain at the shrub stage, bloming and fruiting abundantly.
These are mostly wind-scrubs. Thus, at Titahi Bay (north shore of Cook Strait, RC.) there is an admirable example of such a scrub, (H. H. Allan, 1926: 72–76) which occurs on a somewhat concave slope slightly sheltered from the wind, only the taller shrubs receiving its full force. The lianoid Metrosideros perforata is dominant but growing as a ball-like shrub ± 1 m. high, and with it are associated a number of stunted trees and shrubs2 Various lianes bind the plants-together and on the floor are the ferns Asplenium adiantoides, A. flabellifolium, A. lucidum and Polypodium diversifolium.
On the isthmus connecting Nugget Point (SO.) with the mainland the wind-scrub is about 1 m. high and made up of species common in the adjacent forest3 and so dense that one can walk upon it, nor can the plants be disentangled without using force.
Near the Whangamoa Inlet (SN.) where the greywacke cliffs have been greatly weathered and debris suitable for occupation by shrubs has been provided there is an unusual community which consists of: great tussocks of Phormium Colensoi and low rather willow-like bushes of Dodonaea viscosa.
7. Coastal Forest.
1 1) White Island is a small cone in the solfatara stage, 2.4 km. diam., 328 m. high, situated in the Bay of Plenty and distant from the mainland 48 km. From its crater pass off great clouds of steam highly charged with hydrochloric acid. It is the presence of this gas (W. R. B. Oliver, 1915) that governs the distribution of plant-life on the island, since where the fumes strike there is complete absence of vegetation. In foggy weather, Oliver graphically states, "it may be said to rain dilute. Hydrochloric acid".
2 Podocarpus dacrydioides, P. spicatus, Macropiper excelsum, Pennantia corymbosa (juvenile form), Melicytus ramiflorus, Caprosma propinqua, C. rhamnoides and, where the scrub merges into coastal forest, Myrtus bullata, M. obcordata, X M. bullobcordata and Shawia paniculata,
3 Podocarpus totara, Wintera color ata, Carpodetus, Fuchsia excorticate, Coprosma propinqua, C. foetidissima and the lianes, Muehlenbeckia australis, Raoulia australis, Fuchsia perscandens and Parsonsia heterophylla which bind the shrubs tightly together.
Coastal forest is distinguished ecologically by its low stature and close, more or less wind-swept roof, and floristically by the presence, but not invariably, of various trees or other plants belonging to the coastal element. In what follows, not only coastal forest proper is dealt with but certain associations, here called "semi-coastal", linking up with the lowland forest of the particular locality.
It would serve no purpose to supply statistics regarding coastal forest since, as will be seen, no true line can be drawn between such and lowland forest; in fact, in many places, coastal forest differs mainly from that of the adjacent lowlands in the greater abundance of wind-tolerating members which may form a seaward girdle.
As seen in chapter III of this section the coastal trees number 24, but only the following are at all common in any association and some of these are limited to a special part of the coast: — Macropiper excelsum, Pittosporum crassifolium, P. umbellatum, Dodonaea viscosa, Metrosideros tomentosa, Pseu-dopanax Lessonii, Myoporum laetum and Coprosma retusa. In addition, certain inland trees1 play an important part.
Coastal forest occurs all round the shore of the two main islands and Stewart Island where wind and spray do not forbid. Also, in especially sheltered positions, semi-coastal forest comes close to the beach and in the Western district, even where fairly exposed to the prevailing wind, true lowland podocarp-broad-leaved tree forest flourishes quite near the flat shore, protected merely by a narrow girdle of more or less spray-tolerating trees. On wind-swept islands all the forest may be of a coastal type.
Associations where true coastal trees are most in evidence belong to the Auckland districts and, in proceeding southwards, such trees gradually decrease in number, until from Banks Peninsula to Foveaux Strait only Myoporum laetum remains, while in the Western, Fiord and Stewart districts the true coastal tree element is absent2
1 Hedycarya arborea, Carpodetics serratus, Pittosporum tenuifolium, Weinmannia racemosa, Edwardsia microphylla, Melicope simplex, M. ternata, X M. tersimplex, Dysoxylum spectabile, Coriaria arborea, Pennantia corymbosa, Alectryon excelsum, Melicytus ramiflorus, Leptospermum scoparium, Metrosideros lucida, Myrtus bidlata, Fuchsia excorticata, Nothopanax arboreum, Pseudopanax crassifolium var. unifoliolatum, Griselinia littoralis, Dracophyllum longifolium, Suttonia salicina, S. australis, Geniostoma ligustrifolium, Vitex lucens, Coprosma robusta, C. lucida, Olearia rani, Br achy glottis repanda.
2 Hardly any of the coastal trees can tolerate more than a-few degrees, of frost, and when it is remembered that nearly all the genera are palaeotropic, while 6 species extend to countries warmer than New Zealand, it seems highly probable that the coastal treeflorula is but a remnant of one much larger and that the species frequent the shore-line rather on account of the mild maritime climate than through possessing special "adapt-ations". On the other hand, the almost frostless climate of the west coast of South Island is not unsuited for some of the coastal trees unless the colder summers and excessive rainfall are antagonistic Perhaps the absence in the Western district of those species exteuding to the North-western may be ascribed to the repopulating by plants of the Westland coastal plain after the glacial period.
b. Groups of associations.
1. The Metrosideros tomentosa (Pohutukawa) group.
Pohutukawa forest is distinguished by the dominance, subdominance or presence in fair quantity of M. tomentosa. Corynocarpus laevigata may be in abundance or even dominate.
Forest of this class extends throughout the Auckland districts to the north-west coast of the East Cape district but, though M. tomentosa reaches lat. 39° on the west coast of North Island, how far along that coast south-wards from Manakau Harbour the coastal communities under consideration extend, or extended, I do not know.
It is not feasible at this period in the history of New Zealand to give details regarding the original composition of the associations of this group so, only a general account can be attempted, limiting descriptions to what I have personally seen of such forest from the far north of North Island to about lat. 37°.
The forest is lower the tree-trunks more slender and the undergrowth more open than in rain-forest generally. Where wind-swept, the roof is close, but, as the forest depends on shelter, the wind-effect is not strongly marked. Metrosideros tomentosa is generally dominant, but Corynocarpus is often a most important member and will give a distinct facies. Leptospermum scoparium may dominate a subassocation as in gully-forest surrounded by shrubland. The commonest of the remaining coastal trees are Macropiper, Pittosporum crassifolium, Dodonaea viscosa and Pseudopanax Lessonii. Common non-coastal trees are Knightia, Beilschmiedia taraire (in some parts), Dysoxylum, Hoheria populnea (in the far north), Melicytus ramiflorus, Suttonia australis and Vitex lucens. Tree-ferns (Cyathea dealbata, C. medullaris) are abundant. Rhipogonum scandens, Muehlenbeckia australis and Freycinetia are common lianes. Astelia Banksii, as a huge epiphyte, is frequent in the forest, and prostrate Freycinetia, Paratrophis microphylla, Melicope ternata (also as a tree), Leucopogon fasciculatus, Geniostoma, Rhabdothamnus, various species of Coprosma and Brachyglottis repanda may form the undergrowth. Many of the smaller ferns will be present, especially, — Adiantum hispidulum, Pteris comans, P. macilenta, P. tremula, Blechnum filiforme (liane), Doodia media, Asplenium bulbiferum, A. lucidum, Polystichum Richardii, Dryopteris pennigera, D. velutina, Polypodium diversifolium, Arthropteris tenella (on rocks), Cyclophorus serpens. Near streams, there may be in the far north the fine, large-but thin-leaved herb Colensoa physaloides.page 111
In certain parts of the Auckland districts groves or girdles of Metrosideros tomentosa (Fig. 19), at times adorn the shore just above high-water mark. Such trees have only short primary trunks from which spring numerous ascending branches, which, copiously branching, form dense heads covered with wind-resisting, thick, green leaves, white beneath with dense tomentum. Frequently, the association may be pure, but at other times certain of the coastal trees may be present.
2. The Corynocarpus (Karaka) group.
This group is distinguished by the dominance or fair abundance of Corynocarpus laevigata, associated with such coastal trees and shrubs and spray-tolerating non-coastal species as belong to the locality where the community is found.
Corynocarpus1 forest extends from the North Auckland district to the north of South Island and thence along the east coast to about lat. 43°. It is abundant at various places in the Egmont-Wanganui, Ruahine-Cook and North-eastern districts but, in proceeding south, the number of species greatly decreases.
Near Tongaporutu (north of west coast, EW.) H. H. Allan reports that the following northern trees occur in the association: — Entelea arborescens, Sideroxylon novo-zelandicum, Vitex lucens, Olearia furfuracea var. rubicunda and O. albida. The main floor plant is Asplenium lucidum, and Marattia fraxinea occurs in gullies. As for the bulk of the species it is much same as in the next association.
1 C. laevigata itself extends on the east coast of South Island to Banks Peninsula (nearly lat. 44°) but, on the west coast, where its association might well be expected, not quite to lat. 42°; for instance Townson (1906: 407) reports only "isolated patches" and a few trees on the banks of the Buller. Also, as the Maoris were accustomed to plant this tree near their villages, doubt must frequently arise as to its occurrence in certain localities not being due to this cause. Few trees spread more rapidly by means of seed, and so its presence in apparently primeval forest does not disprove its being absent in the primitive community.
2 Such are Macropiper excelsum, Paratrophis opaca, Urtica ferox, Hedycarya arborea, Corynocarpus, Melicytus ramiflorus, Pseudopanax crassifolium var. unifoliolatum, Myoporum, Coprosma retusa, and of these the last two and the Urtica are nearest the shore.
3 The principal are Rhopalostylis sapida, Knightia, Pittosporum tenuifolium, Melicope ternata, Dysoxylum spectabile, Pennantia, Fuchsia excorticata, Nothopanax arboreum, Coprosma grandifolia, Brachyglottis repanda and Olearia rani.
Along the coast of the North-eastern district, though more or less Corynocarpus may be present, the association is generally dominated by Myoporum laetum1, which at times is virtually pure. The remaining tree, if Macropiper and Dodonaea be excepted, are those of the adjacent lowland forest2
3. The Myoporum (Ngaio) group.
This group is distinguished by the dominance of Myoporum laetum pure at times, but usually a number of non-coastal trees are present.
Myoporum forest occurs in all the Botanical Districts of South Island, excepting the Western, North Otago and Fiord. Its composition depends upon the degree of exposure to sea-spray, and to the dropping out of the true coastal species in proceeding southwards. For the North-eastern district the association has been already described along with Corynocarpus forest.
In the Sounds-Nelson district, facing Cook Strait where the north-west wind strikes obliquely, the trees are dwarfed but furnished with far-extending lateral branches and the members may be only Myoporum (dom.), Macropiper excelsum, Dodonaea viscosa, Coriaria arborea, Coprosma robusta, Solanum, aviculare and Shawia paniculata.
In the South Otago district in addition to Myoporum — there the sole coastal tree — Melicytus ramiflorus is exceedingly plentiful and not infrequently dominates. As for the other species they are merely those of the ordinary lowland forest of the neighbourhood, and have been cited for the coastal forest of the North-eastern district but excluding Melicope ternata, Dodonaea, Macropiper and Alectryon, all of which, except the first-named being in coastal forest of Banks Peninsula.
4. Nothofagus coastal forest.
This is merely the ordinary Nothofagus forest of the particular locality greatly dwarfed by wind blowing almost constantly from the same quarter. Where the wind strikes with greater intensity still forest dwarfed to scrub, as already described, is the final stage in its reduction.
1 1) This will tolerate a maximum of sea-spray. Thus, facing Cook Strait in the Sounds-Nelson district, leafy branches come down to the ground and extend into the drift-wood of the shore. The leaves of such shoots are remarkably large and thick being frequently 7.5 m. long X 2.5 cm. or more broad and about 1.5 mm. thick.
2 For instance: Carpodetus, Pittosporum tenuifolium, Edwardsia microphylla, Melicope ternata, Pennantia, Alectryon excelsum, Aristoielia serrata, Melicytus ramiflorus, Fuchsia excorticata, Nothopanax arboreum, Griselinia littoralis, Suttonia australis, and Urtica ferox are common in some localities.
Forest of the class under consideration occupies the flat ground near the summit of the wall-like cliffs to the south of Westport. Nothofagus cliffortioides is dominant; the other important constituents are: Phyllocladus alpinus, Nothofagus fusca, Weinmannia racemosa, Metrosideros lucida and Dra-cophyllum longifolium. The principal lianes are Freycinetia and Metrosideros perforata. A somewhat similar association occurs on the slopes of the Paparoa Mountains, southwards from the Barrytown coastal plain, where there is every transition from lowland forest so scrub.
5. Coastal forest of certain small islands.
If an island is sufficiently small the vegetation as a whole is more or less affected by the wind, and the forest is stunted and of a coastal character. Here only associations belonging to none of the preceeding groups are dealt with.
The Three Kings Islands.
According to Cheeseman — the only botanist who has visited this group — there are two distinct tree associations, the one dominated by Leptospermum scoparium1 and the other by Meryta Sinclairii2 — an araliad with enormous entire leaves in great rosettes.
The Poor Knights.
1 1) This occurs on the Great King, an island only about 2.8 km. long, 1.2 km. wide and 300 m. high. The Leptospermum is 3.6 m. to 7.5 m. high and growing in its company are Davallia Tasmani, Paratrophis Smithii, Pittosporum Fairchildii, Alectryon grandis — these 4 peculiar to the group — and Cyathea medullaris, Melicope ternata, Hedycarya arborea and Coprosma macrocarpa.
2 This association is restricted to an islet lying between the Great and West Kings which is only 1.2 km. long by 0.8 km. wide. The community is truly tropical in aspect. Not only is Meryta dominant but there is luxuriant Cordyline australis and as undergrowth the large-leaved Macropiper excelsum var. major and supra-luxuriant Pteris comans. Meryta there varies in height from 3 m. to 4.5 m. according to the degree of shelter.
6. Semi-coastal forest.
At an indefinite distance from the coast, depending perhaps in some measure upon salt-laden winds extending inland, and still more upon the sea having receded comparatively recently, various coastal and semi-coastal species are present in the ordinary rain-forest proper of the locality. The most important of these species are Macropiper excelsum, Dysoxylum spectabile, Corynocarpus laevigata, Alectryon excelsum, Dodonaea viscosa and Myoporum laetum, while the following are common in their respective areas of distribution: — Cyathea medullaris, Blechnum filiforme, Polystichum Richardi, Aspleniumlucidum, Pteris macilenta, P. tremula, Freycinetia Banksii, (as a ground plant), Rhopalostylis sapida, Paratrophis microphylla, Melicope ternata, Tetrapathaea tetrandra (liane), Myrtus bullata, Solanum aviculare, Geniostoma ligustrifolium, Coprosma grandifolia, Olearia rani, Brachyglottis repanda. With these will occur the various common podocarps, Metrosideros robusta, Elaeocarpus dentatus and other ordinary lowland forest trees and shrubs.
Such forest is ecologically similar to lowland forest, but it will only tolerate slight frosts, consequently it occurs in its full development only in North Island and the northern part of South Island. However, lacking a good many of its members, it extends on the east coast to Banks Peninsula and on the west coast to Greymouth.
Further to the south on the east coast there is no forest until the South Otago district is gained and there the semi-coastal tree-association is marked by the presence of Myoporum laetum and particularly the abundance of Melicytus ramiflorus, while Griselinia littoralis, Hoheria angustifolia and Edwardsia microphylla are characteristic. Semi-coastal forest of this character is almost a thing of the past. On the west coast, there is from about lat. 43° southwards almost continuous forest but there is little of semi-coastal type, ordinary broad-leaved — podocarp communities — with more or less Nothofagus in the Fiord district — coming almost to the shore, but frequently sheltered in the Western district by a girdle of trees, as already described, or a belt of tall Phormium tenax.
The Dysoxylum spectabile (kohekohe) association is distinguished by either the dominance or the presence in large numbers of Dysoxylum spectabile1 and usually there is a good deal Macropiper excelsum2
1 1) As occurring near the coast this is a small tree about 6 m. high or considerably less with cauliflorous trunk covered with a rather pale smooth bark, spreading tortuous stout branches and a close head of large pinnate leaves more than 30 cm. long with broad shining leaflets of vivid green and, in winter, the naked trunk and thick branches bear drooping panicles ± 30 cm. long of waxy-white flowers.
2 The other species present are the usual trees, shrubs and ferns already cited. On Stephen Island, there is a good deal of Coprosma retusa as a small tree, and the palm, Rhopalostylis sapida, ascends into the forest roof
The association was formerly common in many places — either adjacent to the coast or up to 2 km. or more inland — in the south of the Egmont-Wanganui and Ruahine-Cook districts and the north of the Sounds-Nelson and North-west districts. As the community occupied remarkably fertile soil suitable for artificial pasture only remnants, usually much damaged persist.
On the islands in Cook Strait, especially Kapiti and Stephan Island, and on the wind-swept peninsula called Pepin Island (SN.), the association is of a true coastal character with a close roof (Fig. 22) while within the Dysoxylum possesses far-extending, twisted, gnarled branches.
Stunted podocarp forest probably occurs, or occurred, in many places In the northern part of the Western district there is a narrow strip of strongly wind-shorn forest which, between Greymouth and Hokitika, consists of stunted Podocarpus dacrydioides and Dacrydium cupressinum, 6 to 9 m. high (dominant) and the branches of the first-named are much more widely-extended than usual, also Carpodetus, Weinmannia racemosa, Aristotelia serrata, Fuchsia excorticata, Suttonia salicina, Coprosma Lucida, C. foetidissima, C. areolata. Griselinia lucida and Astelia Cunninghamii are common epiphytes. Metrosideros perforata and Rubus australis are the principal climbers.
Metrosideros lucida forest, in which the Metrosideros is almost the sole tall tree, forms a belt in Stewart Island coming between the coastal scrub and the Weinmannia-rimu forest. As undergrowth there are the usual ferns and shrubs (few in number) of the district. Similar forest occurs in the South Otago district on the shore of Foveaux Strait. It is of extreme interest that this association is almost identical with the Lord Auckland Islands' forest—a matter to which I called attention in 1904, and which impressed Sir Joseph Hooker so greatly that he wrote me (dated Nov. 15th, 1904) as follows: "Of all the facts which you have marshalled that of the Rata forest in the Auckland Islands is the most pregnant and of the Antipodean flora the least expected".
On the seaward slopes of the Paparoa Mountains (south of NW.) the forest as a whole is much stunted but — where the composition is that of rain-forest proper — the dark, rounded heads of M. lucida stand out at fairly regular intervals above this stunted assemblage of trees, shrubs, tree-ferns &c.