The Vegetation of New Zealand
Chapter IV. — The Plant Communities
The Plant Communities.
1. Subalpine Forest.
The distinction between lowland (in some localities), montane and subalpine forest is arbitrary, all grading into one another and possessing many species in common. Nor can definite altitudinal limits be fixed, for lowland forest in North Island may ascend to over 1000 m. altitude with its composition but little changed, but in the South Otago and Fiord districts at only 150 m. altitude, or even less, it is virtually a lower-subalpine community. So, too, the Dacrydium intermedium association of Stewart Island and the south of the Fiord district has a distinct subalpine facies. Nevertheless, in procee ling from the lowlands to the timber-line, well-marked belts of vegetation are encountered, the true lowland species, according to latitude and aspect, going out at certain altitudes and being replaced by those of the high mountains; also, there are purely high-mountain associations.
High-mountain forest, in general, is distinguished by the dominance of medium-sized or small trees which belong to very few species, together with comparatively few kinds of shrubs and ferns as undergrowth, the former being more or less of the divaricating-form, together with Phyllocladus alpinus, Wintera colorata, Myrtus pedunculata Nothopanax Colensoi, N. simplex, Griselinia littoralis and Coprosma foetidisima, and the latter the semitree fern Polystichum vestitum (in great abundance), Hymenophyllum multifldum and Blechnum procerum (generally stunted); woody lianes are absent or poorly represented and asteliads and epiphytic shrubs wanting.
The high-mountain forest flora as a whole consists of about 175 species (including hybrid swarms) (pteridophytes 32, conifers 9, monocotyledons 23, dicotyledons 111), as compared with 387 for lowland-montane forest. The species belong to 75 families and 84 genera, the largest of the former being: Filices 29, Compositae 19, Rubiaceae 15 and Podocarpaceae and Araliaceae 8 each, and of the latter: Coprosma and Olearia 13 each, Hymenophyllum 9 and Nothopanax 6.
As in the case of lowland forest, the high-mountain communities are of the rain-forest type (except perhaps bog-forest). Here they are divided into three classes, — (1.) subantarctic, (2.) subtropical and (3) bog-forest, but it is a matter of taste whether the latter should stand alone, or be included in class 1, and when a subtropical association is of a subantarctic facies it is called conditional subantarctic and is dealt with in class 1.page 255
Subantaretic high-fountain forest falls into the two divisions, Nothofagus forest — this a part of the general Nothofagus plant-formation — and tree-composite forest (conditional subantarctic) which is a formation in itself. Subtropical high-mountain forest is a part of the general subtropical forest plant-formation, and it consists of the two groups, Libocedrus-podocarp forest and low podocarp forest.
The high-mountain forests have suffered far less from the direct and indirect action of man than have those of the lowland-montane belt, and in localities of high rainfall they still occupy much the same area as in primitive New Zealand. They extend throughout the subalpine belt subject to a high rainfall of both islands and Stewart Island from the East Cape district southwards, but where the climatic-climax is tussock-grassland, sheep-farming has considerably reduced the originally-limited forest area, and the community is now restricted to gullies and, in a lesser degree, to shady slopes. In many parts of the wetter mountains, actual virgin forest still flourishes but, year by year, its area rapidly diminishes through the strong modification of the undergrowth through the action of deer.
The following are the life-forms of high-mountain forest: — trees 47 (medium-sized 7, small 22, tuft-tree 3, tree-composite 15), shrubs 44, herbs and semi-woody plants 25, grasslike plants 12, earth-orchids, 5, lianes 8, parasites 4 (woody 3, earth-orchid 1), saprophytes 1, ferns 29. The number of species of bryophytes is bound up with the rainfall; foliaceous lichens are of large size and abundant.
The special physiognomy of the forest depends upon the numerous, rather slender tree-trunks covered more or less thickly with bryophytes and lichens; the usually rather open undergrowth of shrubs and a few low trees with spreading twiggy branches; the extensive dark-coloured colonies of Polystichum vestitum, 1 m. or so high; the floor where open carpeted in places with filmy-ferns and bryophytes. At the upper limit of the forest, the incoming of subalpine shrubs and even herbs lends a new character. But the above is merely general, for the composition of an association in conjunction with its climate and edaphic conditions influences its appearance. In comparison with lowland forest the absence of the characteristic lianes, epiphytes and tree-ferns at a glance distinguishes the two classes.
b. The Nothofagus communities.
Any Nothofagus community is to be distinghuished by the dominance of one or more species of Nothofagus, these in their turn being dependant upon relative altitude and climate. But N. cliffortioides (Figs. 66, 67, 68) is frequently dominant, the other species being absent over wide areas.
The distribution of the three mountain species of Nothofagus possibly depends upon their relative xerophily, N. cliff ortioides. the most xereophytic, page 256occupying the driest and loftiest stations. N. Menziesii" with its leaves thicker and smaller than those of N. fusca, and its greater epharmonic plasticity, comes midway in its requirements, so, where the precipitation is excessive, it may form the sole subalpine forest, N. fusca dominating at a lower altitude. Where the three species occur in the same locality, N. fusca, mixed more or less with N. Menziesii, may form the lowest belt and N. cliffortioides, either pure or mixed with N. Menziesii, the highest. The effect of station on the distribution of these species is sometimes striking. Thus, according to F. G. Gibbs, on one part of Mt. Arthur (NW.) in the subalpine N. Menziesii forest at an altitude of 1020 m., N. fusca gives out and N, cliffortioides appears, but especially on dry, rocky points. In the extensive N. cliffortioides forest near the sources of the River Poulter (W. eastern part), N. fusca and sometimes M. Menziesii appear occasionally, but they are invariably confined to sheltered gullies, where the conditions are much more mesophytic than on the ridges and slopes.
Nothofagus forest is par excellence the high-mountain tree-community of New Zealand. It is absent in the following localities only: — (1.) Mount Egmont and the Pouakai Range (EW.); (2.) from the R. Taramakau almost to the R. Paringa — a distance of about 180 km. (W.); at the sources of the R. Rakaia and most of its tributaries (W., in its eastern part); in Stewart Island.
Evidently this high-mountain part of the great Nothofagus formation, which extends for so great a distance, occupies two or more altitudinal belts, and is exposed to considerable extremes of climate especially rainfall (100 to 750 cm.), must be made up of more associations than can be dealt with here but, fortunately these fall into natural groups according to the species dominating and the structure &c. of such groups in relation to rainfall and latitudinal change1. Such groups consist, in the first place, of those dominated respectively by Nothofagus cliff ortioides and N. Menziesii and, in the second place, those in which more than one species of Nothofagus in concerned. There is also a closely-related well-marked group of associations which are dealt with as a separate formation entitled mountain bog-forest, which might, however, come into the conception of the Nothofagus formation.
β. The mountain southern-beech (Nothofagus cliff ortioides) group of associations.
1 1) This does not nearly make such a great difference as might be expected. Thus, taking the whole flora of the Nothofagus communities — lowland, montane and subalpine — the total number of species is about 214, of which no less than 78 per cent extend throughout their range, while the small minority — 48 species only — are, for the most part, either quite local or restricted to South Island, where some also are of strictly limited distribution, e. g. local endemics of various districts.
In North Island, the Tararua mountains excepted, N. cliffortioides forest forms the uppermost belt on all mountains where Nothofagus is present, but on the Waimarino Plain (VP.) it descends to less than 900 m. altitude, possibly owing to former forest of a different class having been destroyed during a volcanic eruption1.- Even in South Island a N. cliffortioides association rarely descends to much below 600 m. altitude, although, as already explained, it is not an uncommon member of many lowland forests. Where there is an abundant rainfall the association is continuous with montane forest, but where tussock-grassland conditions prevail, it is generally confined to gullies, hollows, or the sheltered side of river-terraces. In such cases, there is no merging of forest and tussock-grassland, but the tree-mass ends abruptly.
Dry Nothofagus cliffortioides forest.
This class of forest is distinguished by its paucity of species, the open undergrowth and the few species of bryophytes.
In North Island, the distinct association, described below, occurs on the east of the central volcanoes (VP.) and owes its dry character to the permeable pumice soil rather than to lack of rain. In South Island, dry N. cliffortioides forest occurs at various places on the ranges, extending eastwards from the Divide (especially in NE. and E.). There, too, it is not lack of rain alone which stamps the forest, but the violent winds so frequently hot and dry.
1 1) This explanation was first suggested by E. Phillips Turner (1909: 5) who writes as follows: "The wedges of beech that penetrate the taxad forest may be the result of a volcanic discharge of hot sand or lapilli which have destroyed the original plant covering; the beech having succeeded as being the most suited to withstand the resulting exposed situation, and the (as yet) imperfect soil."
The associations of the Eastern and North-eastern districts are chiefly distinguished by the poverty of undergrowth which, frequently, when the substratum is shallow clay on a steep slope, consists merely of young southern-beeches and seedlings with patches of the mosses Dicranoloma robustum, D. leucomoloides and D. setosum. The trees are slender, about 9 m. high and their branching scanty. In many places, the ground is bare the clay showing through a coating of dead leaves and twigs; where driest the fallen trees are destitute of a mossy covering. Frequently the undergrowth is richer, but large areas may be occupied only by juvenile trees, for N. cliffortioides is short-lived, and, as the adult trees fall, light is let in, seedlings grow vigorously and the forest rapidly regenerates (Fig. 68). Lyco-podium fastigiatum and the summergreen Hypolepis Millefolium are generally abundant.
Or in the dampest places, there will be plenty of Polystichum vestitum, 60 cm. and more tall and sheets of Hymenophyllum multifidum. In some localities Sphagnum cushions are present on which may grow Oxalis lactea. The undergrowth, may consist of Coprosma propinqua, C. parviflora, C. linarii-folia (E.), and Pittosporum divaricatum (E. and NE.). In the Eastern district, Hoheria Lyallii, Griselinia littoralis and various shrubs may grow on the forest's outskirts, but usually the assocation ends abruptly and one steps from the shade of the trees into the open tussock-land.
Wet Nothofagus cliffortioides forest.
In this group of associations the undergrowth is denser than in that just described, more species occur, and there is an actual moss-carpet or small moss-cushions. The forest, too, either makes a continuous covering, extending from the montane to the upper subalpine belt, or, succeeding some other forest-association, forms the uppermost belt of tree-vegetation. All the already-mentioned species may be present and, in addition, others according to the geographical position of the forest.
Wet N. cliffortioides forest occurs in quantity on the Ruahine Mountains, the Waimarino Plain, to the west and south of Ruapehu and most likely on the highest peaks of the East Cape district. In South Island, it is common on the eastern slopes of the Southern Alps within the area reached by the north-western rain. In the Waimakariri Basin (E.) there is a most extensive area, the mountain slopes being covered with a dark mantle of trees from 600 to 1200 m. altitude (Fig. 39), but in a few localities there are small colonies of N. fusca and smaller still of N. Menziesii. In many other parts of South Island, the forest under consideration is confined to the uppermost forest-belt.
On the south of Mount Ruapehu a Nothofagus cliffortioides association occupies about the last 100 m. of the forest-mass with its timber-line at page 259about 1300 m. It contains more or less Libocedrus Bidwillii (sometimes only 5.2 m. high) and the small podocarps, Dacrydium Bidwillii and D. biforme; in places Gleichenia Cunninghamii forms close masses, and prostrate Leucopogon fasciculatus is characteristic. The following, together with those already cited, make up the bulk of the community: — Polystichum vestitum, Blechnum penna marina, Lycopodium fasiigiatum, Podocarpus nivalis, Phyllo-cladus alpinus, Gahnia pauciflora, Astelia Cockaynei, Libertia pulchella, Griselinia littoralis, Myrtus pedunculata, Nothopanax simplex, N. Colensoi, Suttonia divaricata, Coprosmapseudo-cuneata, C. parviflora and C. foetidissima. Hymenophyllum multifidum is abundant.
The Waimarino Plain's association at 900 m. altitude is much as the last but amongst its important members are some which do not reach the final forest-belt, especially: — Cordyline indivisa, Rubus australis, Carpodetus serratus, Pittosporum Colensoi, Hebe salicifolia (one or more jordanon) and Coprosma tenuifolia. On the margin of this association there is tall shrubland (an early stage of forest) containing amongst other species Phormium Colensoi, Cordyline indivisa (Fig. 69), young Nothofagus cliffortioides, Nothopanax Colensoi and Hebe salicifolia.
The extensive forest of the Waimakariri (E.), in its lower part, was fairly uniform. In places, young N. cliff or tioides dominated the undergrowth; in other places, was composed of small Phyllocladus alpinus, Griselinia littoralis and the usual Coprosmae. The floor was carpeted with several species of Dicranoloma, Hymenophyllum villosum and H. multifidum. Polystichum vestitum were abundant. Where small rivers pass through the forest there were various subalpine shrubs on its outskirts, particularly in the case of the tributaries of the River Poulter, the chief being Olearia arborescens, 0. lacunosa, 0. avicenniaefolia, Senecio elaeagnifolius and the tuft-tree, Dracophyllum Traversii. Near the timber-line, the undergrowth was far denser and species of the subalpine-scrub joined the association. Where there have been land-slips there are bright-green colonies of Hoheria glabrata.
On the rocky ground of the Pikikiruna Range (NW.), until quite recently, a remarkable Nothofagus association occurred, but, since my first visiting it in 1915, it has been almost entirely destroyed by fire and replaced by an open association of shrubs, principally species and hybrids of Hebe.
The ground on which this tree-association grew consists of most irregular, much-weathered, honey-combed mounds of hard limestone, full of holes which provide complete drainage and render the habitat, though in a very wet climate, essentially xerophytic.
Nothofagus cliffortioides, about 7.5 m. high was dominant with its slender trunks far apart, so that much light entered the association. In consequence, there was an undergrowth composed of more or less xerophytic (mostly epharmonically) shrubs &e., e. g.: Asplenium Trichomanes (rock crevices), page 260Phyllocladus alpinus, an occasional small Libocedrus Bidwillii, Uncinia caespitosa, Astelia Cockaynei, Pittosporum divaricatum, Pimelea longifolia, P. Gnidia, Metrosideros lucida, Nothopanax simplex (mesophytic), N. anomalum, Corokia Cotoneaster, Suttonia divaricata, Olearia avicenniaefolia, Traversia baccharoides.
γ. Silver southern-beech (Nothofagus Menziesii) group of associations.
This group is distinguished by the dominance of N. Menziesii, but N. fusca, N. cliffortioides and × N. cliffusca may be present, as also Libocedrus Bidwillii, Podocarpus Hallii and Weinmannia racemosa.
In North Island, N. Menziesii forest is common on the Dividing Range and the Volcanic Plateau (includes the central volcanoes) and, in South Island, in the North-western, Fiord, and South Otago districts, and portions of the Eastern and southern part of the Western districts. In certain localities, it forms the highest altitudinal belt, but only where N. cliffortioides is wanting or in small quantity. Here both montane and subalpine forest are dealt with.
All the species found in any montane-subalpine Nothofagus forest are present in some part or other of the community, but more are usually included than in the N. cliffortioides communities.
Generally the dominant trees of N. Menziesii are low, their crowns scanty, their trunks irregular, buttressed (sometimes to an excessive extent), and frequently moss-clad. The undergrowth consists of an upper tier of shrubs and a lower of floor-plants, these, however, not of equal height. In some localities, certain of the shrubs mentioned below rise as small trees above the average level. The following occur throughout: — Dacrydium Bidwillii, Phyllocladus alpinus, Wintera colorata, Aristotelia fruticosa, Nothopanax Colensoi, N. simplex, N. anomalwn, Griselinia littoralis, Cyathodes acerosa, Suttonia divaricata, Coprosma foetidissima, C. Colensoi, C. pseudocuneata and C. parviflora. Various filmy and creeping ferns, Enargea parviflora (creeping amongst moss), Libertia pulchella and species of Uncinia are common floor-plants, but of far greater physiognomic importance are the taller ferns, especially Polystichum vestitum, the silvery masses of Astelia Cockaynei and the tall green tussocks of Gahnia pauciflora (North Island and parts of NW.) or G. procera (South Island).
The upper forest of Mount Te Aroha (Th.).
1 1) The Northern montane forest is represented by Astelia trinervia, Phyllocladus glaucus, Ixerba brexioides, Alseuosmia macrophylla, Quintinia serrata, Dracophyllum latifolium and Senecio Kirkii, and the Nothofagus Menziesii association by Phyllocladus alpinus, Libocedrus Bidwillii, Enargea parviflora, Libertia pulchella, two spp. of Nothofagus. Griselinia littoralis, Nothopanax Colensoi, Coprosma Colensoi and C. foetidissima
Montane forest of East Cape district.
At an altitude of about 700 m. on the Huirau Mountains, Nothofagus Menziesii and N. fusca replace the trees of the subtropical rain-forest and Nothofagus forest — possibly with N. cliffortioides dominant in the uppermost belt — ascends to the summits. At 900 m. altitude, owing to the N. Menziesii trees being far apart, the undergrowth was so dense at the place visited that few, if any, seedlings were present on the forest-floor. This undergrowth was about 3 m. high and composed of Dicksonia lanata (the trunkless var.) in great abundance, Leptopteris superba, Astelia nervosa var. sylvestris, Enargea parviflora, Wintera colorata, Ixerba brexioides, Quintinia serrata, Nothopanax Colensoi, N. simplex, Dracophyllum latifolium, Coprosma tenuifolia, C. parviflora, C. foetidissima, Alseuosmia quercifolia and Senecio Kirkii.
Montane-lower subalpine forest of the Volcanic Plateau.
N. Menziesii is taller and with straighter trunks and larger crowns than is general in forest of this class. N. fusca is common, especially at the lower limit of the association. At first, Coprosma tenuifolia is plentiful but it gives place higher up to C. foetidissima. The fern Polypodium novae-zelandiae creeps over fallen trees. Alseuosmia quercifolia is plentiful. The other species are those common to N. Menziesii forest in general. At the lowest level, N. Menziesii is a massive tree with large buttresses; even at 900 m. altitude trees 21 m. high and 90 cm. diam. are not uncommon.
The uppermost belt of the Tararua Mountains.
The forest varies much according to exposure to wind; in the gullies, trees are 10 m. high but, on the ridges, they are much smaller. The trunks of N. Menziesii, slender, fairly straight much mossed, rise out of the undergrowth, the upper branches short and gnarled. On the floor there is much Hymenophyllum multifidum, stunted Blechnum procerum and Astelia Cockaynei. The belt begins at an altitude of about 600 m. and ends at 900 m. as a minimum. At first, there is plenty of N. fusca; Podocarpus Hallii and Weinmannia racemosa are present throughout, the latter often a shrub. Pittosporum rigidum occurs in the uppermost part with other plants of the subalpinescrub, especially Senecio elaeagnifolius. Hybrids in which Coprosma Colensoi, C. Banksii and C. foetidissima all play a part are common.
Upper forest of Mount Stokes (SN.).
1 1) Hymenophyllum villosum, H. flabellatum, H. rufescens, H. Malingii, H Armstrongii, H. tunbridgense, H. multifidum, H. scabrum, H. dilatatum, H. rarum.
Various associations of the North-western district.
From information supplied by F. G. Gibbs the association on Mount Arthur has evidently much in common with the last two, but it differs in the presence of Pseudopanax lineare and in the colonies of Dracophyllum Traversii of its upper portion. At 1020 m. N. Menziesii gives place to N. cliffortioides.
The subalpine forest of Mount Rochfort is a combination of N. Menziesii and N. cliffortioides associations, so far as canopy-trees go, but its contents and habit place it with the former. Metrosideros lucida, Weinmannia racemosa, Quintinia acutifolia, Pseudopanax lineare and, near its lower limit, Metrosideros Parkinsoni1 are common. On the floor are innumerable mosscushions, of great dimensions which intermingle, and, where a slope descends steeply, form veritable cascades. On the ground, the small shrub Wintera Traversii2 is fairly common. Astelia Cockaynei is abundant and the tufttree Dracophyllum latifolium, its trunk more slender than that of D. Traversii is frequently conspicuous.
Governor's Bush near Mount Cook hermitage (east of W. near junction with E.).
In the vicinity of Mount Cook, as is seen more clearly further on, high-mountain species occur at a low level, but this is not particularly in evidence in the small area of Nothofagus Menziesii forest.
N. Menziesii is only a slender, small tree, its trunk 45 cm. diam. at most. There is a fairly rich undergrowth as follows: — Blechnum fluviatile, B. procerum, Polystichum vestitum, Hypolepis Millefolium, Podocarpus nivalis, P. Hallii, Phyllocladus alpinus, Carex Cockayniana, Uncinia uncinata, U. caespitosa, U. leptostachya, juvenile N. Menziesii, Pittosporum tenuifolium, P. divaricatum, Rubus schmidelioides var. coloratus, Aristotelia fruticosa, Hoheria glabrata (where much light), Nothopanax Colensoi, Griselinia littoralis, Coprosma pseudo-cuneata, C. parviflora. C. linariifolia, Lagenophora petiolata and Senecio elaeagnifolius.
Associations of the Fiord and South Otago districts.
1 1) A low tree of straggling habit with a slender, rigid, leaning trunk covered with warm-brown bark, frequently prostrate and rooting at the base and finally giving off numerous twiggy branches bearing on their flanks the dark-green, rather stiff, ovate leaves, 5 cm. in length.
2 2) There is a slender, wiry, stiff stem creeping just beneath the surface of the ground and then bending upwards as an erect unbranched stem leafy for the greater part, but with leaf-scars below. The leaves are dull olive-green, waxy beneath, thick, coriaceous, oblong-obovate and 2 cm. long.
The species are those of N. Menziesii forest in general but, on the whole, the conditions on the actual Divide are more favourable for the establishment of subalpine shrubs &c., e. g. Pseudopanax lineare and Archeria Traversii var. australis, and the general bryophyte content of the forest reaches its maximum. As for the undergrowth of the Fiord-South Otago forests it was originally fairly dense the physiognomic species being various divaricating-shrubs, erect bushes of Wintera colorata and Coprosma foetidissima with far-extending, arching, twiggy branches. The upper forest belt of the Longwood Range was (or is?) remarkable for its great bryophyte cushions.
δ. Montane Nothofagus Solandri forest of the Eastern district.
Associations of this type come close to those of dry N. cliffortioides forest. They are distinguished by the dominance of N. Solandri, but some N. cliffortioides may be present and what are probably hybrids between the two; also in some localities a certain amount of Podocarpus spicatus was present.
Originally, there was an extensive area near Mount Oxford (E.), whence it extended, but not continuously along the foothills to Mount Grey on the one hand, and, on the other, to the base of Mount Torlesse. The association resembled in its physiognomy that of dry N. cliffortioides, but the trees were considerably taller; the undergrowth, too, was similar but richer in individuals and species.
ε. Life-history of Nothofagus forest.
Here the Nothofagus forest of every altitudinal belt is considered. All the species of the genus are light-demanding and grow far faster than any other tall, indigenous tree. On these properties depend the procession of events both within and without the forest. There are these two aspects of the question, (1.) the establishing of Nothofagus forest on a non-forested area and (2.) the turning of subtropical forest into southern-beech forest.
The progress of events within and outside a Nothofagus forest can be seen throughout the area of distribution of the formation. Where forest conditions prevail, on any open piece of ground, even in tussock-grassland, seeds of any species of Nothofagus will germinate and develope, if not too close, into bushy trees. From such trees seed can be carried into tussock-grassland by the wind for about 8 m., or much further, should there be no page 264obstacle in their path. Also southern-beech seeds germinate well in the shade supplied by open Leptospermum scoparium shrubland, the seedlings developing with fair rapidity and when they overtop the Leptospermum it is doomed. Still more rapid is the victory of Nothofagus when it and Leptospermum develope together. Their rate of growth is much the same, but in from 12 to 20 years the Nothofagus will be cutting off the light from the strongly light-demanding Leptospermum and in a year or two the latter will all be dead. Within certain young forests can be seen the flourishing southern-beech trees and on the floor the dead stems and branches of the original Leptospermum shrubs. Once the Nothofagus is established, species more shade-tolerating come into the association (e. g. various ferns). Frequently, especially in the lowlands, a considerable number of trees, shrubs &c. commence their existence along with the Leptospermum and the Nothofagus, e. g. Cyathea dealbata, Nothopanax arboreum, Cyathodes acerosa, Leucopogon fasciculatus, Coprosma rhamnoides, C. robusta and Olearia rani.
Inside most Nothofagus forests, no matter the altitude, the crop of young southern-beeches can be seen ready for filling up the gaps when adult trees fall. Seedlings develop well enough under the ordinary roof canopy, but not beneath the undergrowth, but their growth is slow until exposed to that much greater illumination which comes in when one of the frequently half-rotten1 trees crashes to the ground. During heavy gales many trees fall simultaneously in N. cliffortioides forest and this accounts for the large, dense stands of saplings in many subalpine localities. As soon as the much brighter light penetrates the forest the saplings and seedlings affected at once respond, no matter to what extent their growth had been restrained.
In some forests where such death of the large trees has taken place over wide areas the sapling community is astonishingly dense. All light sufficient for other plants is cut off, so the ground remains bare, except for dead leaves and twigs, and the lateral branches of the saplings are gradually suppressed. As time goes on, the greater part of the competing young trees are killed, more light reaches the floor, so that conditions allow the most shade-tolerating species of forest-plants to gain a footing and, by degrees, the original forest association is reinstated.
1 1) All the species of Nothofagus are liable to the attacks of fungi. This is least in N. Menziesii, but very severe in the case of the other species. In an apparently vigorous forest of N. fusca, frequently more than half the trees are rotten, especially if they are of large size. Sometimes this state of affairs is revealed by striking the trunk which in many instances is hollow. In other cases, the condition of a tree cannot be ascertained until it is felled, though frequently dead branches tell of its being diseased. From the economic standpoint this matter of disease is of great moment and the remedy is probably to fell the trees long before they reach their full development.
Coming now to subtropical rain-forest containing a few trees of Nothofagus fusca or N. Menziesii, and considering what is likely to be the procession of events, the question is by no means simple. Certainly, if the undergrowth is open, there will be plenty of seedlings or saplings of the southern-beech, but density not openness is the rule for such forest. All the same, under certain conditions Nothofagus forest can replace Subtropical rain-forest. Thus, after fire, if both podocarps with their accompanying trees and any species of Nothofagus be in close proximity to the bare ground, all is in favour of the new forest being dominated by Nothofagus. So, too, in localities of very high rainfall and poor soil in Nothofagus - dicotylous - podocarp forest as the podocarps die, there is a fair chance of their being replaced by Nothofagus. On the other hand, in lowland rainforest proper, the rapidity with which a dense undergrowth can be established is entirely hostile to Nothofagus. In the Ruahine-Cook and Sounds-Nelson districts with a Nothofagus association on the slopes and rain-forest proper in the gullies no southern-beech seedlings have the slightest chance to become established in the latter habitat. The investigation of G. Simpson and J. S. Thomson in the neighbourhood of Dunedin prove conclusively that an original Nothofagus forest has been replaced by the present rain-forest proper, while especially hostile to the establishment of Nothofagus seedlings are the great colonies of Blechnum discolor, and I may add those of treeferns also.
c. Conditional subantarctic forest communities.
In this type of forest Nothofagus is absent and its place taken by species floristically related to those dominating subtropical forest proper, but ecologically suited to subantarctic conditions. The dominant or important trees are of low stature and include small podocarps, Libocedrus Bidwillii, Dracophyllum Traversii and various arboreal Compositae.
This is distinguished by the dominance of several species of Olearia and Senecio, while the tuft-tree, Dracophyllum Traversii is frequently a physiognomic feature of an uncommon kind. The association is closely allied to subalpine-scrub, into which it generally merges.
The following are important members of the association: — Polystichum vestitum, Blechnum procerum, Hymenophyllum villosum (epiphytic on trunks and branches), Libocedrus Bidwillii, stunted Podocarpus Hallii, P. nivalis, Dacrydium biforme, Astelia Cockaynei, Phormium Colensoi, Hoheria glabrata, Viola filicaulis, Nothopanax Colensoi, Griselinia littoralis, Dracophyllum page 266longifolium, D. Traversii, Suttonia divaricata, Hebe vernicosa var. canter-buriensis, Coprosma pseudo-cuneata, C. parviflora, Olearia ilicifolia, O. lacunosa, O. arborescens, O. avicenniaefolia, O. nummularifolia (also several hybrid swarms with the first three species of Olearia cited above concerned in their parentage) and Senecio elaeagnifolius.
The association usually puts in an appearance at about 900 m. altitude and extends upwards for a greater or lesser distance, until, with increase of altitude or exposure to wind, it gradually becomes smaller and is transformed into subalpine-scrub. It probably occurs in the North-western district, but it is extremely abundant in the western part of the Western district where it may form a distinct belt; it also occurs on the eastern side of the Divide, especially near the sources of the Rakaia and some of its tributaries.
As shown by its composition, its most important life-forms are the tree-composite, the tuft-tree, the cupressoid, the araliad, the divaricating and the bushy deciduous tree.
The association is about 4.5 m. high. The trunks of the composites are semi-prostrate (Fig. 60), with long strips of papery bark hanging downwards. Above is a tangle of branches; beneath the forest is more or less open. Seen from without, certain of the trees, either through their colour or form, strongly affect the physiognomy of the forest. Thus Dracophyllum Traversii is indicated by its candelabra-like crown and huge reddish-brown leaf-rosettes, Hoheria by its bright light-green, Phyllocladus by its greyish, green hue, Griselinia by its shining green, darker than that of Hoheria and the shrub-composites by their rather flat crowns which, in certain species are whitish in the mass. The undergrowth consists of divaricating-shrubs of various genera, species of Hebe, Astelia Cockaynei and colonies of Polystichum vestitum and Blechnum procerum. Hymenophyllum villosum clothes many trunks and branches. A few herb-field species may be present, especially Ranunculus Lyallii and Phormium Colensoi.
Mountain toa-toa (Phylloeladus alpinus) group of associations.
This group is distinguished by the dominance or occasionally subdominance of Phyllocladus alpinus, and usually the presence of one or more of the high-mountain podocarps. It is related to bog-forest, but occurs on drier ground where more species can enter in.
The Volcanic Plateau association, here described, occurs on the north of Mount Tongariro, the upper Waimarino Plain, Hauhungatahi and other places. Sometimes, Podocarpus Hallii dominates. The trees are about 6 m. high; Libocedrus Bidwillii and some, or all, of the podocarps are present. Hymenophyllum multifidum and Astelia Cockaynei are common floor plants. The following are plentiful: Wintera colorata, Aristotelia fruticosa, Myrtus pedunculata, Nothopanax Colensoi, N. simplex, Suttonia divaricata, Coprosma tenuifolia, C. microcarpa, C. Colensoi, C. parviflora, C. pseudo-cuneata and C. foetidissima.page 267
On the shaded side of the R. Cass near its mouth (E.) there is low forest where Phyllocladus alpinus dominates and grades into river-terrace scrub with which it has many species in common, e. g. Polystichum vistitum, Blechnum penna marina. Pittosporum divaricatum, Rubus subpauperatus, R. schmidelioides var. coloratus, Coriaria sarmentosa, Discaria toum, atou (3 to 3.6 m. high), Aristotelia fruticosa, Corokia Cotoneaster, Dracophyllum longifolium (not in the scrub), Hebe salicifolia var. communis, H. Traversii, Coprosma crassifolia, C. parviflora, C. propinqua and Cassinia fulvida var. montana.
On the steep face of the Sealey Range near Mount Cook hermitage (east of W.), the Nothofagus Menziesii forest gives place to Phyllocladus alpinus forest which, in its turn, gradually merges into subalpine-scrub. The other leading members of the association are Dacrydium Bidwillii, small Podocarpus Hallii, P. nivalis, Griselinia litloralis, Dracophyllum longifolium and Senecio elaeagnifolius.
Mountain ribbonwood (Hoheria glabrata) low forest.
Hoheria glabrata is essentially a denizen of stony ground. On steep mountains (W., F.), where land-slips have occurred, this association stands out clearly from the dark forest-mass through its bright-green leaves (red and yellow in autumn), wealth of snowy blossoms in due season and deciduous habit in winter.
This association is especially well developed in the Fiord district, where it may form small groves on a substratum of large stones or extend upwards to the timber-line.
H. glabrata, about 7.5 m. high, is dominant, its trunk and far-extending horizontal branches thickly covered with moss, and depending from them an abundance of Weymouthia Billardieri (Fig. 71), and perched on them Asplenium flaccidum. Griselinia littoralis occurs here and there as a tree; Polystichum vestitum dominates the undergrowth; there is more or less Nothopanax Colensoi and Olearia ilicifolia.
Hoheria Lyallii, a closely-related species, frequently forms small clumps on river-terrace in the North-eastern and Eastern districts.
d. Subtropical rain-forest and allied communities.
Subtropical rain-forest is distinguished by the absence of Nothofagus and the presence of Libocedrus Bidwillii, Podocarpus Hallii, Weinmannia racemosa and Metrosideros lucida as dominant tall trees, but all are not of necessity present in an association.
The class of forest under consideration is not nearly so continuously distributed as is subantarctic forest. In North Island, it occurs on some of the mountains of the Volcanic Plateau and Mount Egmont and, in South Island, in the North-western district, the Western from the Taramakau to the Mahitahi, the Eastern on Banks Peninsula, the South Otago near Dunedin and Stewart Island.
β. Associations and groups of such.
Southern kawaka-totara (Libocedrus Bidwillii-Podocarpus Hallii) group.
In its various forms this is the most important of the subalpine subtropical forests. It is distinguished by the dominance of either of the species cited above, and the Libocedrus, when abundant, with its erect habit and pyramidal head, clearly defines the community even when viewed from afar. In South Island it occurs, but not everywhere, in the subalpine belt of the North-western, Western and Eastern districts and originally to some extent on hills near Dunedin; and, in North Island, on Mount Egmont and the Volcanic Plateau. As will be seen, it is closely related to tree-composite forest, indeed the latter near the source of the Rakaia is a connecting-link between the two groups.
On Mount Hauhungatahi (VP.) there is an association of this class. This mountain is an isolated extinct volcano, 1520 m. high, situated west of Ruapehu. It is forest-clad up to about 1140 m. altitude. At the base of the mountain, and below, at a height of 780 m. or less, the podocarp-forest is replaced by a southern kawaka-totara association. The trees consist of: — Libocedrus Bidwillii (first appearing at about 600 m. alt.), Podocarpus Hallii, P. ferrugineus, Dacrydium cupressinum, D. Colensoi, Weinmannia racemosa and Olea Cunninghamii. The smaller trees and shrubs of the undergrowth are Phyllocladus alpinus, Wintera colorata, Carpodetus serratus, juvenile Elaeocarpus Eookerianus, Aristotelia fruticosa, A. serrata, Melicytus lanceolatus, Myrtus pedunculata, Fuchsia excorticata, Nothopanax simplex, N. Colensoi, N. anomalum, Pseudopanax crassifolium var. unifoliolatum, Schefflera digitata, Griselinia littoralis, Suttonia salicina, S. divaricata, Coprosma grandifolia, C. robusta, C. tenuifolia, C. parviflora, C. Colensoi, C. foetidissima and Alseuosmia quercifolia. Dicksonia lanata (trunkless) ascends to 1080 m., or more, and may form much of the undergrowth, its fronds being 1.5 m. long. Many lowland ferns are common and Leptopteris superba forms considerable colonies. At an altitude of 960 m. (Phillips Turner 1909: 3), Dacrydium cupressinum, hitherto abundant, becomes much scarcer and the forest is more typically subalpine with Libocedrus Bidwillii dominant and Podocarpus Hallii, Dacrydium Colensoi and D. intermedium abundant. Tussocks of Gahnia pauciflora become characteristic and the subalpine-scrub plants of the vicinity enter into the association. In some parts of this association, as where it abuts on the Waimarino Plain, near Horopito and elsewhere, the handsome tuft-tree Cordyline indivisa is plentiful. Close to the timber-line the forest becomes very low (scrub-forest), and it is closely related to bog-forest and subalpine-scrub. Its small trees are Libocedrus, Dacrydium intermedium, D. biforme, Phyllocladus alpinus, Griselinia littoralis and Dracophyllum longifolium.
On Mount Egmont an association containing Libocedrus is apparently confined to the vicinity of the North mountain-house and does not extend page 269to the Stratford house. It commences at about an altitude of 900 m. with Podocarpus Hallii in abundance, but Libocedrus Bidwillii soon becomes dominant, though Podocarpus Hallii, Weinmannia racemosa and Griselinia littoralis are abundant. This latter is bent, arched and gnarled, while its trunk may be covered by sheets of the dark, curled leaves of Hymenophyllum villosum and yellowish-green cushions of Dicranoloma Billardieri. The common shrubs of the association are: — Wintera colorata, Carpodetus serratus, Aristotelia, serrata, Melicytus lanceolatus, Fuchsia excorticata, Nothopanax Sinclairii, N. Colensoi, Suttonia divaricata, Hebe salicifolia (form with narrow leaves), Coprosma grandifolia, C. tenuifolia (abundant), C. parviflora, C. egmontiana and Senecio elaeagnifolius var. Buchanani. The sole liane is an occasional plant of Rubus australis. Seedlings and young trees are constantly epiphytic, e. g. Coprosma lucida var. angustifolia, Griselinia littoralis, Nothopanax Colensoi and N. Sinclairii, the last two frequently killing and replacing their host. A striking feature is the profusion of bryophytes, especially Hepaticae, both on the floor and tree-trunks; the undergrowth is particularly dense and Wintera colorata plays a most important part; on the floor is an epharmone of Astelia nervosa var. sylvestris.
On the west of the Southern Alps, and extending for 160 km. or more southwards from the R. Taramakau, the southern kawaka-totara belt commences at an altitude of about 600 m., Podocarpus Hallii being the first tree to arrive. From North Island associations this differs only in certain floristic details. Weinmannia racemosa and Metrosideros lucida are abundant at first. Tussocks of Gahnia procera are a feature of the floor-vegetation. Lianes and tree-ferns are absent. At the upper limit subalpine shrubs by degrees enter in until a distinct belt of forest results.
The highest peaks of Banks Peninsula doubtless originally carried a belt of southern kawaka-totara forest, for there are ample remains, while a small piece in its virgin state still exists on Mount Sinclair. Weinmannia racemosa, Metrosideros lucida and other species are absent, but Cordyline indivisa, plentiful in Westland, but not occurring elsewhere east of the Divide, is fairly common. Other members of the association are Wintera colorata, Griselinia littoralis, Fuchsia excorticata and Nothopanax arboreum.
Kamahi (Weinmannia racemosa) group of associations.
Weinmannia racemosa is frequently dominant in parts of southern kawaka-totara forest, while, in certain localities, it forms an almost pure association — so far as tall trees are concerned.
On Mount Egmont kamahi forest is so striking that it has received the popular and expressive name of "Goblin forest". It occurs as a distinct belt from the neighbourhood of Dawson Falls to the North Egmont house and it probably extends right round the mountain.
At first, there are some comparatively low trees of Dacrydium cupressinum page 270but these soon give out and those of Weinmannia decrease in stature and become much-branched, the branches at first more or less erect, but with increase of altitude they extend far horizontally and are gnarled and irregular in shape. Both trunks and branches are covered densely with mosses, liverworts and filmy-ferns (Hymenophyllum multifidum, H. villosum, H. flabellatum) which could not be in such profusion but for frequent rain. Griselinia littoralis is an important small tree and Fuchsia excorticata occurs here and there. The undergrowth consists of ferns and rather freely-branched shrubs, the following being common: — Blechnum procerum, B. fluviatile, Polystichum vestitum, Uncinia Banksii, Astelia nervosa (unnamed jordanon), Wintera colorata, Carpodetus serratus, Coprosma parviflora, C. tenuifolia. At a higher altitude Podocarpus Hallii enters the association which then becomes equivalent to that in which Libocedrus is present. At about 1200 m. altitude, the forest gives place to subalpine-scrub
On Mount Hauhungatahi, in places, there is a Weinmannia association more or less of the "Goblin Forest" character.
Southern-rata (Metrosideros locida) group of associations.
Forest of this class is wide-spread in the Western district, it is montane rather than subalpine, but as mountain plants descend so low in that locality, it is here included with subalpine forest.
At above 450 m. altitude in the Western district M. lucida becomes dominant and the lowland podocarps gradually decrease in numbers. Weinmannia racemosa in places is so plentiful as to dominate. Quintinia acutifolia is conspicuous through its somewhat fastigiate habit as a sapling and the yellowish leaves blotched with purple but pale beneath. Many of the lowland shrubs and ferns are present. The undergrowth is dense, especially in gullies. Bryophytes (species of Gottschea, Schistochila, Aneura, Mniodendron, Plagiochila, Lembophyllum &c.) and Hymenophyllaceae abound. Leptopteris superba forms extensive colonies.
At the Franz Josef glacier, the terminal face of which descends to 213 m., the southern-rata association comes on to the ice-worn rocks at a few metres from the ice on either side of the glacier. The forest here, the roof of which has the characteristic billowy appearance, consists principally of the following: Metrosideros lucida and Weinmannia racemosa (the dominant canopy-trees), Carpodetus serratus, Coriaria arborea, Aristotelia serrata, Hoheria glabrata, Melicytus ramiflorus, Pseudopanax crassifolium var. unifoliolatum, Schefflera digitata, Griselinia littoralis, Hebe salicifolia, Coprosma lucida, Olearia arborescens and O. avicenniaefolia. The pterido-phytes include Hemitelia Smithii (tree-fern, but here of low stature), several Hymenophyllaceae, Hypolepis tenuifolia, Histiopteris incisa, Blechnum procerum, B. lanceolatum, Asplenium bulbiferum, A. flaccidum, Polystichum vestitum, Polypodium diversifolium, P. Billardieri and Lycopodium volubile.
At Mount Peel (E.) there is a small southern-rata association with page 271M. lucida as the sole tree "on rocky knolls and. slopes with a westerly-aspect (H. H. Allan, 1926: 44) which is a succession after Leptospermum ericoides"1. On the floor there may be much Blechnum procerum and Alsophila Colensoi and near streams colonies of Gleichenia Cunninghamii.
In Stewart Island at an altitude of 300 m. the forest decreases in height, Metrosideros lucida, sometimes with prostrate trunks, becomes more abundant, especially on exposed ridges, Weinmannia is still plentiful, tall Leptospermum may appear, and moss-cushions become far commoner. On the lower hills, so far as is known, at about 270 m., the forest gradually decreases in height until its interior is a tangle of stems from semi-prostrate, slender trunks. On the uneven floor great cushions of Plagiochila gigantea and Dicranoloma robusta abound (Fig. 72).
e. Montane and subalpine bog-forest.
Bog-forest is distinguished by the presence of stunted Notho-fagus trees, together with nearly always one or more of the small podo-carps and Libocedrus Bidwillii; more or less sphagnum is generally present.
Taking all the area occupied by this class of forest, the following are important members in one or more of the associations: — Hymenophyllum multifidum, H. villosum, Blechnum procerum, Hypolepis Millefolium, Gleichenia Cunninghamii, Libocedrus Bidwillii, Dacrydium Colensoi, D. intermedium, D. biforme, D. laxifolium, Podocarpus Hallii, P. acutifolius, Phyllocladus alpinus, Microlaena avenacea, Carex ternaria, C. Gaudichaudiana, Uncinia caespitosa, Gahnia pauciflora, G. procera, Enargea parviflora, Astelia Cockaynei, Libertia pulchella, Nothofagus Menziesii, N. cliffortioides, Nothopanax Colensoi and var. montanum, N. simplex, Pseudopanax lineare, Griselinia littoralis, Gentiana Spenceri, Dracophyllum longifolium, Cyathodes acerosa, Leucopogon fasciculatus, Suttonia divaricata, Coprosma pseudo-cuneata, C. parviflora and C. foetidissima.
Bog-forest occurs in any altitudinal belt of forest from the Volcanic Plateau district southwards to the Fiord and South Otago districts. It is found on ground where the drainage is bad and it is specially common where the rainfall is excessive.
The physiognomy of bog-forest depends upon the low, more or less stunted trees of Nothofagus, the cupressoid podocarps, the pyramidal Libocedrus, the irregular floor with usually cushions of sphagnum here and there, the rather dense undergrowth which is accentuated by the Gahnia tussocks and the divaricating shrubs.
1 1) In no part of this book is a description given of Leptospermum. forest, such being dealt with as an early succession in the development of kauri or southern-beech forest. It is true that stands of Leptospermum scoparium are frequently met with, but it is usually impossible to know whether such are primitive or induced. H. H. Allan (1926:44) describes a Leptospermum ericoides subassociation for Mount Peel (E.) with the Leptospermum 15 m. high and Suttonia australis as the chief member of the undergrowth.
High-mountain bog-forest is evidently closely related to lowland bog-forest, or rather, in certain localities, it is its continuation upwards, so it really belongs to the same formation.
Below, examples are given of high-mountain bog-forest in different parts of the Region.
The Volcanic Plateau.
Nothofagus cliffortioides is dominant and Da-crydium Colensoi frequently subdominant. The species not occurring in the associations further south are Gahnia pauciflora, Pittosporum Colensoi and Coprosma tenuifolia. Astelia Cockaynei is frequently abundant or, if the soil is particularly wet, A. nervosa var. grandis. Gleichenia Cunninghamii is common; sphagnum may be wanting. Floor and tree-trunks are thickly covered with bryophytes. Both Leptospermum scoparium and L. ericoides may be present. Libocedrus Bidwillii is sometimes abundant.
On the western side of the Tasman Mountains bog-forest — so far as I have seen it — contains stunted N. cliffortioides (about 3.6 m. high), abundance of Leptospermum scoparium, also Dacrydium intermedium, D. biforme, Elaeocarpus Hookerianus, Metrosideros Parkinsonii, Gahnia procera, Blechnum procerum and Pseudopanax lineare.
On the Rahu Saddle (Victoria Range) the association is dominated by very slender N. cliffortioides and the following are important members: Sphagnum in abundance, mats of Hymenophyllum multifidum, low cushions of Plagiochila, Phyllocladus alpinus (as a small tree), Libocedrus Bidwillii, Pittosporum divaricaium, Pseudopanax lineare, Suttonia divaricata, Coprosma parviflora, C. pseudo-cuneata and C. foetidissima. Other communities in the same locality, in addition to the above, contain Dacrydium Colensoi, D. intermedium, D. biforme and Leptospermum scoparium.
Near Tophouse (eastern part of the district, foot of St. Arnaud Range) the bog-forest contains much Sphagnum; both N. Menziesii and N. cliffortioides are present; Libocedrus Bidwillii is common and Coprosma pseudo-cuneata the characteristic species of the undergrowth. There is no Pseudopanax lineare.
Western district, eastern side of the Divide.
On the flat summits of the truncated spurs which are so common a feature of the forest-clad portion of the Waimakariri Basin, there is nearly always bog-forest containing N. cliffortioides, abundant Libocedrus Bidwillii, Dacrydium biforme and D. Bidwillii, but none of the other allied podocarps. Where the light is strong, there are sphagnum cushions carrying prostrate Leptospermum scoparium and mats of Dacrydium laxifolium.
In the same district and also in the Eastern and wetter parts of the North-eastern districts, and probably elsewhere, there is occasionally bog-forest where N. cliffortioides is the sole tree and Podocarpus nivalis the only podocarp.
Western district on west side of the Divide in southern part.
In this area, as already explained, Nothofagus is absent, but in the montane page 273and upper lowland belts there is bog-forest with abundance of Phyllocladus alpinus, Libocedrus Bidwillii with epiphytic Hymenophyllum Malingii, Dacry dium biforme, Podocarpus Hallii, P. acutifolius and various common species of such communities, including Gleichenia Cunninghammi, Aristotelia fruticosa, Myrtus pedunculata and Nothopanax anomalum.
2. Shrub Communities.
Taken as a whole, the high-mountain shrub communities are made up principally of medium-sized and tall shrubs and dwarfed trees. Other life-forms, however, are important, notably the woody lianoid and parasitic, the large tussock-form, herbaceous perennials, semi-woody plants and ferns especially, Polystichum vestitum, Danthonia Cunninghamii, D. Raoulii var. flavescens, Phormium Colensoi, Aciphylla maxima and A. conspicua. Most of the other grasses, herbs &c. which occur are hardly real members, since some occupy merely the line of tension between shrubland and their proper formation, and others are chance comers.
The number of dwarfed trees, shrubs, woody lianes and parasites is 143 (non-endemic omitting the pteridophytes 3) which belong to 29 families and 43 genera. The largest families and genera are as follows: — (families) Compositae 36 species, Scrophulariaceae 26, Epacridaceae 16, Rubiaceae 13; (genera) Hebe 25, Olearia 17, Dracopyllum and Coprosma 13 each and Senecio 9. Also many hybrid swarms play an important part, especially in Aristotelia, Dracophyllum, Hebe, Coprosma, Olearia and Cassinia. Taking the species as a whole, 65 per cent are shrubby composites, hebes, epacrids and coprosmas. Many of the species are strongly xerophytic but notwithstanding a considerable number as has been seen, thrive in the forest under hygrophytic conditions, owing in some cases to great plasticity with regard to their life-forms.
When fully developed, all the associations are closed but, in places, a few are open, owing either to being an early stage of succession or to the edaphic conditions not being suitable for some of the leading species. Apparently, the communities fall into two main classes — the one representing a definite stage of biological or it may be biological-topographical succession, and the other with a more or less distinct relation to climate may be considered a climax or subclimax community.
b. Associations usually of shingly ground.
This consists of Discaria toumatou either pure or mixed with a few medium-sized shrubs.
As explained, when dealing with lowland low tussock-grassland, the association appears as a succession following the earlier herb &c. stages of river-bed or fan vegetation but, though persisting for a considerable time, page 274it is at best but a migratory community and is replaced by other shrub-associations, tussock-grassland or even Nothofagus forest.
Discaria toumatou itself is a semi-divaricating shrub, usually about 1.2 m. high, but varying greatly epharmonically in stature, having spreading, flexible but wiry, slender, dark-coloured branches, at times more or less leafless, furnished at intervals of about 2 cm. with rather long, sharp spines (morphologically reduced shoots).
The shrubs are dotted about on the stony ground or in clumps with spaces between, but eventually they grow into one another. The dark colour of the association shows up from afar, especially in contrast to the adjacent yellow tussock-grassland. Generally, D. toumatou is the sole shrub, but one or other of the ball-like species of Hebe may be present. As in the lowlands, Clematis marata may climb over the Discaria. The stony spaces between the shrubs may be bare, but usually there is a sparse growth of tussock and some of its accompanying plants.
The association does not belong specially to the high mountains but is also common in the lowland belt. It is restricted to South Island, but is wanting in the Western and Fiord districts, except east of the Divide, where it occurs on those wide river-beds which extend into the forest-area. In the North Otago district, there is a Discaria community at from about 180 m. altitude upwards both in valleys and on slopes of "fertile" mica-schist soil. Olearia odorata is common; other species are Muehlenbeckia complexa, Clematis marata, Carmichaelia Petriei, C. gracilis (rare) and Olearia lineata.
This group of associations is distinguished by the dominance of one or usually more species of Hebe and generally some divaricating shrubs are present.
The species number about 50 which belong to 16 families and 24 genera. The following are common members in some part or orther of the group: — Hypolepis Millefolium, Blechnum penna marina, Muehlenbeckia complexa, Pittosporum divaricatum, Rubus schmidelioides var. coloratus, R. sub-pauperatus, Discaria toumatou, Aristotelia fruticosa, Hymenanthera alpina, Corokia Contoneaster, such species of Hebe as belong to the locality, Coprosma propinqua, C. parviflora, and one or more of the mountain species of Cassinia. Hebe hybrids may be in such profusion that it is difficult or impossible to recognize the species present.
The shrubs are erect. Their principal life-forms are the ball-like and the divaricating. Of less importance are the Dracophyllum. and shrub-composite forms. The lianes are slender; most not only climb, but form bushes approximating to the divaricating-form. Leaving the ferns out of consideration, 2 of the species are mesophytic and several, at most, sub-xerophytic. Eight have tomentose leaves.
Hebe shrubland is a common feature of the upper montane and sub-page 275alpine belts. Its presence, generally denotes a tussock-grassland climate, but it demands more shelter from wind than does tussock-grassland, its principal development being in the river-valleys eastward of the South Island Divide. A favourite situation is the sheltered side of river-terrace. It occurs also on the outskirts of the lower subalpine forest; on torrentfans just where they issue from a gorge, or in the mouth of the latter; on ancient river-bed and on coarse debris at the foot of some disintegrating cliff. The soil that the association affects ranges from stones mixed with fine clay and sand to deep clayey loam. The wind-factor may be extremely powerful on river-bed, but much modified on river-terrace. The soil-water must vary considerably, but-even on a steep terrace-face may be fairly abundant. The relation to snow and prolonged frost differs greatly according to aspect, but the richest development is where the sun is least powerful.
The associations vary from a close, bright-green growth of species of Hebe to a dense, dark-coloured scrub about 1.8 m. high, of divaricating shrubs1 bound together by the various lianes2 and relieved in places by the green of Hebe or the whitish hue of Olearia avicenniaefolia; Discaria toumatou is frequently present. Beneath the shrubs the ground may be bare or occupied more or less closely by certain ferns3. On many riverbeds, if the rainfall is high, or near streams flowing through tussock-grassland or fell-field or where water oozes out of the ground are thickets of the glossy-leaved Hebe buxifolia var. odora round as a cricket-ball. The cupressoid H. salicornioides sometimes grows in the North-eastern district in soil saturated with ice-cold water. Coarse rocky debris in the North-eastern and Eastern districts, larger in size than that of "Shingle-slip", is occupied in the first instance by Hebe scrub and not tussock-grassland. Rubus schmidelioides var. coloratus or R, subpauperatus and the rigid, open, dark-coloured almost leafless cushions of Hymenanthera alpina are often present.
Hebe shrubland follows on as a succession after various mat-plants have occupied the stony substratum and provided a seed-bed. Evidently, it is closely related to Discaria thicket, but the latter occupies a more sunny position. In shady situations, it may be an early stage of Nothofagus forest.
1 1) Aristotelia fruticosa, Pittosporum divaricatum, Coprosma rugosa, C. parviflora, C. propinqua, Corokia Cotoneaster, Olearia virgata, and 0. odorata.
2 2) Rubus australis, R. schmidelioides var. coloratus, R. subpauperatus, Parsonsia capsularis, Muehlenbeckia complexa, M. australis and Helichrysum dimorphum (E., limited to a small part of the R. Waimakariri basin).
3 3) Polystichum vestitum, Cystopteris novae-zelandiae, Hypolepis Millefolium, Blechnum penna marina.
The species number about 122 which belong to 28 families and 49 genera the largest being: — (families) Compositae 26, Epacridaceae 14, Scrophu-lariaceae 13, Rubiaceae 12, Filices 10; (genera) Hebe and Olearia 13 each and various hybrid swarms, Coprosma 12 and Dracophyllum 11. But, in addition to the above, various podocarps, Nothofagi, Hoheria glabrata, Leptospermum scoparium, araliads, giant Aciphyllae and Suttonia divaricata are of importance in many localities.
The general ecological conditions that determine the presence of the formation are: altitude, (which decreases from north to south or according to edaphic xerophily); violent wind (but less than herb and grass communities can tolerate); a heavy winter snow-fall, (but not the maximum); and frequent rain at all seasons. This last factor leads to the presence of a xerophytic soil rich in peat or raw humus. But, in the dry mountain areas, scrubs likewise occur, some of which are strongly bound up with edaphic conditions, as in the case of the serpentine Mineral Belt and the Senecio Monroi scrubs of the North-eastern district.
The subalpine-scrub associations differ from one another in density, floristic composition and physiognomy in different localities, and dissimilar scrubs may occupy contiguous areas. According as shrub-composite, cu-pressoid-podocarp, Hoheria glabrata, Phyllocladus alpinus, stunted Nothofagus, Dracophyllum or divaricating-shrubs dominate, so is there a different and distinct facies. In many parts of the Southern Alps Phyllocladus and Hoheria lend a most distinct appearance to adjacent patches of scrub.
A typical subalpine-scrub of a wet climate consists of a number of rigid or wiry-stemmed shrubs which grow into one another while the main branches of many are parallel to the slope and project downwards. The height may be from 2 to 3 m. and the roof fairly even. The density may be so great that one cannot force a passage through, but must actually walk upon the top! Where there is an actual belt above the forest, it gradually decreases in height as one proceeds upwards and eventually ends in low bushes hugging the ground, herb-field or fell-field cutting gaps into the association. Scrub is taller in gullies than elsewhere and on their shaded side attains its maximum height. In certain cases subalpine-scrub is merely the uppermost belt of forest with its trees stunted to shrubs, and the light-tolerating members of the undergrowth persisting. In other cases, there may be sufficient shelter from wind to allow the shrub-content of grass or herb associations to become dominant, but, on the other hand, an average excessive snow-covering, violent winds, xerophytic edaphic stations, and increase in altitude, favour herb-field at the expense of scrub. The following are the principal classes of subalpine-scrub based on the dominance of distinctive life-forms. Though distinct enough in typical examples, intermediates page 277referable to more than one class are common, and doubtless a number of distinct associations still await discovery and investigation.
β. Shrub-composite scrub.
This is distinguished by the dominance, or occasionally sub-dominance only, of shrubby or stunted arboreal species of Olearia and Senecio, one or both. Various divaricating-shrubs (spp. of Coprosma, Aristotelia fruticosa, Pittosporum divaricatum, Suttonia divaricata) will be present. Also one or other of the fastigiate species of Dracophyllum, phormium Colensoi, Cassinia Vauvilliersii, Phyllocladus alpinus, Nothopanax Colensoi and one or two species of Hebe are frequent members and Dracophyllum, Phyllocladus, Cassinia or even Hebe may in places dominate.
The trunks of the tree-composites are generally prostrate and yet treelike, their horizontal spread exceeding the height of the association. The divaricating-shrub greatly increase the general density. The roof will be fairly level but pierced here and there by Dracophyllum (Fig. 73).
Shrub-composite scrub requires a high rainfall for its full development. In North Island, it occurs on Mt. Hikurangi, the Ruahine and Tararua Mts. and Mt. Egmont. In South Island, it is a characteristic feature of the Western district on both sides of the Divide, making, in many places, a broad belt above the forest and partly filling the cirques at the sources of glacial rivers. Similar scrub occurs in the Fiord district; it is also highly developed in Stewart Island. In what follows an attempt is made to give some idea of its chief floristic characteristics in different localities.
Mount Hikurangi (EC).
The scrub occurs (from information generously supplied by W. R. B. Oliver who recently ascended this mountain on "cliffs and steep rocky slopes, especially on the northern face of the mountain". Senecio Bidwillii (50 cm. high) and Podocarpus nivalis are dominant and mixed with them are Dracophyllum recurvum, Pimelea buxifolia and Hebe tetragona. Tussocks of Danthonia Raoulii var. flavescens and Aciphylla conspicua (if this can be so termed) are common. Coprosma pseudo-cuneata and Olearia Colensoi are present. Beneath the scrub are Hymenophyllum multifidum, Lycopodium fastigiatum, L. australianum and Schizeilema Allanii.
Mount Egmont (EW.)
The scrub commences at about 1140 m. and gives out at about 1240 in. Senecio elaegnifolius var. Buchanani is generally dominant, but sometimes Dracophyllum filifolium rules. The other principal species are Podocarpus Hallii, Carmichaelia australis var. egmontiana, Nothopanax Colensoi, N. Sinclairii, Griselinia littoralis, Suttonia divaricata, Hebe salicifolia (resembling var. paludosa but probably distinct), Coprosma tenuifolia, C, egmontiana, C. parviflora, Olearia arborescens and Cassinia Vauvilliersii,
Tararua Mountains (RC.).
Olearia Colensoi is frequently dominant, but O. arborescens and Senecio elaeagnifolius are often abundant. Other page 278shrubby species are: Pittosporum rigidum, Nothopanax Colensoi, N. Sinclairii N. anomalum, Dracophyllum longifolium, D. filifolium, Suttonia divaricata, Hebe salicifolia var., Coprosma pseudo-cuneata, C. foetidissima, 0. lacunosa, 0. arborescens X lacunosa and Senecio Bidwillii.
Southern Alps and mountains of North-western district.
Olearia ilicifolia or 0. Colensoi are frequently dominant; 0. arborescens and its many hybrids with 0. ilicifolia, 0. nummularifolla, 0. avicenniaefolia, Senecio Bidwillii, var. viridis and S. elaeagnifolius are common shrub-composites1. The following occur throughout and are often important constituents: — Phyllocladus alpinus, Dacrydium biforme, D. Bidwillii, Podocarpus Hallii, P. nivalis Phormium Colensoi, Pittosporum divaricatum, Carmichaelia grandifiora, Arts-totelia fruticosa, Hoheria glabrata, Nothopanax Colensoi, N. simplex, Pseudopanax lineare, Griselinia littoralis, Gaultheria rupestris, Dracophyllum longifolium, D. Lessonianum2, Archeria Traversii, Hebe salicifolia, Hebe subalpina, Coprosma serrulata, C. pseudo-cuneata, C. parviflora, C. ciliata. C. foetidissima and C. ramulosa.
In the South Otago and Fiord districts, scrub dominated by Olearia moschata is not uncommon. Thus, in the Lake Harris hanging valley the combination is 0. moschata (dominant), Aristotelia fruticosa, Hebe Cockayniana (abundant), H. buxifolia, Coprosma ciliata and Senecio revolutus. A somewhat similar scrub occurs on the Takitimu Mountains.
On Tooth Peaks, at about 900 m. altitude, the dominant shrubby composite is Senecio cassinioides and it is accompanied by extensive colonies of Aciphylla maxima of the surprising height of 4.5 m. (Fig. 57), together with Aristotelia fruticosa, Coprosma rugosa, C. parviflora and C. rhamnoides, and as undergrowth, Hypolepis Millefolium, Poa Cockayniana and Acaena Sanguisorbae var. sericeinitens. On Rough Peaks (SO.), according to G. Simpson and J. S. Thomson (1926:373) the combination in an allied association is Senecio cassinioides, Podocarpus nivalis and Phyllocladus alpinus.
1 1) O. lacunosa and O. arborescens X lacunosa (O. excorticata is merely one of the hybrids) are abundant in the North-western and northern part of the Western districts. O. moschata is common from about the latitude of Mount Cook southwards; O. oleifolia (but this may be merely one of the swarm, O. avicenniaefolia × moschata) occurs in the South Otago and Fiord districts; O. Crosby-Smithiana, which is probably Senecio bifistulosus is confined to the central and southern parts of the Fiord district.
2 2) Dracophyllum Traversii is abundant in the North-western and Western districts; D. fiordense is confined to the central and Southern parts of the Fiord district; D. Menziesii is confined to the Fiord and Stewart districts.
. Shrub-composite scrub made up of one species only (Senecio Monroi) occurs on the Inland Kaikoura Mountains and adjacent parts of the district. The substratum is coarse shingle-slip. Elsewhere the species is a rock-plant, and in this case the stony ground, as it slowly grows, is peopled by plants from the mother-rock.
γ. Other types of subalpine-scrub.
Phyllocladus alpinus is dominant. The scrub has frequently almost the same composition as the adjacent shrub-composite scrub but dominance of the podocarp lends a distinct facies and colour. The low Phyllocladus forest of the Volcanic Plateau already described when of low stature is a scrub, as in certain gullies on Mount Tongariro and the Kaimanawa Mountains. Its other species are: Dracophyllum montanum (dominant in places), Nothopanax Colensoi, N. simplex, N. Sinclairii, Griselinia littoralis, Leptospermum scoparium, Coprosma pseudo-cuneata, C. parviflora, C. foetidissima and Olearia nummularifolia. In South Island Phyllocladus scrub is common in the eastern part of the Western district.
The Phyllocladus forest of the Sealey Range (W.), already described, gradually becomes stunted into scrub with P. alpinus dominant and the other members of the forest-association present; in its upper part Danthonia Cunninghamii comes in, and in places Hebe macrantha is common. At an altitude of about 1100 m. facing west, the scrub on the Mount Earnslaw Spur (F.) consists of large bushes of P. alpinus of great breadth, accompanied by more or less prostrate Senecio cassinioides, Podocarpus nivalis, erect Hebe buxifolia, Coprosma ciliata and Aciphylla Colensoi.
. Scrub of this type has usually Dacrydium Bidwillii or D. biforme dominant. Apparently, it is commonest on boggy, windswept or "poor" stony soil.
Near Mount Cook Hermitage on old moraine, there is a scrub of this character with yellowish-green D. Bidwillii dominant, forming bushes ± 1 m. high and 2.5 m. through and with the following more or less common: Polystichum vestitum, Phyllocladus alpinus, Podocarpus nivalis, Discaria toumatou, Aristotelia fruticosa, Hoheria glabrata, Hymenanthera alpina, Coprosma propinqua, C. parviflora, C. rugosa and Senecio cassinioides.
On boggy ground occupying roches moutonees or truncated spurs in the east of the Western district, open or dense scrub is common with either species of Dacrydium dominant.
Cupressoid-podocarp scrub also occurs at the timber-line. For example, Mount Greenland (915 m.), an isolated mountain in the north of the Western district contains near its summit a very distinct form of podocarp-scrub (Fig. 74) which though extremely dense is erect, but on the flat mountain page 280summit becomes low and open. The following is its composition:—Dacrydium biforme (dominant), Phyllocladus alpinus, tussocks of Gahnia procera, Pittosporum divaricatum, Quintinia acutifolia, Weinmannia racemosa, Elaeocarpus Hookerianus, Nothopanax Colensoi var. montanum, Pseudo-panax lineare, Leptospermum scoparium, Metrosideros lucida, Dracophyllum Traversii, D. longifolium, Coprosma pseudocuneata, Olearia lacunosa, O. avicenniaefolia, O. Colensoi and Senecio elaeagnifolius. Besides its erect habit a distinct feature of this community is the mixture of forest and scrub species.
On dry South Island mountains, Dracophyllum uniflorum forms on stony ground a more or less pure rather open scrub of a brownish colour. It burns readily and so is less in evidence than it was in the primitive vegetation. Hebe Traversii, species of Cassinia, Olearia cymbifolia, Podocarpus nivalis and Helichrysum microphyllum (NE. only) may be associated plants. Such scrub, becoming more and more open, merges into fell-field.
D. Lessonianum or stunted D. longifolium are frequently dominant in what otherwise would be classed as shrub-composite scrub but the physiognomy is completely changed. But the change is still greather when D. Traversii, a tuft-tree, projects out of subalpine-scrub.
D. Menziesii, of similar life-form to the last named — but in miniature — occasionally dominates in scrubs of the Fiord district. G. Simpson and J. S. Thomson have supplied the following particulars concerning a piece of scrub just above the timber-line on one of the mountains bounding the North Routeburn Vallay (F.). D. Menziesii is dominant; the other species are Podocarpus nivalis, Gaultheria rupestris, D. Lessonianum, Hebe subalpina, H. buxifolia, H. Cockayniana, Olearia moschata, Cassinia Vauvilliersii and Senecio revolutus. The remarkable feature is the presence of Celmisia Walkeri — usually a mat-plant — as a liane scrambling through the shrubs, its stems exceeding 1 m. in length. In Stewart Island, too, D. Menziesii becomes most conspicuous when projecting out of low dense Olearia Colensoi scrub (Fig. 73).
Manuka (Leptospermum) scrub.
This is chiefly a community of the lower subalpine or montane belts and differs but little from the allied lowland association. In Stewart Island, however, thanks to its tolerance of excessive wind through its epharmonic plasticity, it forms a belt at about 450 m. altitude, or even lower (Fig. 75). At first it is mixed with certain forest-shrubs, but it eventually becomes pure, much reduced in size and with bare stems and small head of twisted branches. Beneath are moss-cushions, carpets of Lycopodium ramulosum, tussocks of Gahnia procera, low-growing Cyathodes acerosa and prostrate Dacrydium Bidwillii.
There is closely-related Leptospermum scrub on Mount Greenland and probably other mountains in the Western district.
It has been shown, earlier on, that for the lowland-montane belt ericoid-scrub of this kind was almost all, if not all, indigenous-induced. On the contrary, there appear to be high-mountain communities of a primitive nature. For example, on Flagstaff Hill (SO.) there is a Cassinia scrub above the timber-line with Alsophila Colensoi as an unexpected member. G. Simpson and J. S. Thomson (1926:373) describe a scrub at 900 m. at the foot of Rough Peaks (SO.) with Cassinia Vauvilliersii dominant, accompanied by Dracophyllum uniflorum, Aciphylla maxima and Gaultheria rupestris, and in open spaces amongst rocks various characteristic high-mountain shrubs, including Olearia moschata and Senecio cassinioides. However, dominance of Cassinia generally means there has been burning and the association it governs must always be looked upon with suspicion.
Southern-beech (Nothofagus) scrub.
The two subalpine species of Nothofagus respond more readily to scrub-conditions than do the trees of other forest-associations, and, in consequence, more than hold their own in competition with subalpine shrubs proper, so that both N. Menziesii and N. cliffortioides forests are frequently succeeded throughout New Zealand by a scrub in which one or other dominates. Such an association may consist almost altogether of Nothofagus cliffortioides, as on many of the drier mountains of the North-western district. Generally where there is an abundant precipitation many of the ordinary subalpine-scrub species accompany the southern-beeches1.
3. Mixed communities (shrubs, herbs, semi=woody plants, grasses &c).
a. Rock vegetation.
High-montain rock vegetation consists of a series of associations made up primarily of obligate and semi-obligate rock-dwelling species and secondarily of various plants, principally xerophytes, which belong also to neighbouring associations.
1 1) On the south of Ruapehu the scrub commences at about 1200 m., N. cliffortioides is dominant. Phyllocladus alpinus, Dacrydium biforme, D. Bidwillii, Nothopanax Colensoi, N. simplex, Myrtus pedunculate, Coprosma foetidissima, C. pseudocuneata and tussocks of Gahnia pauciflora are common. On Mount Rochfort (NW.) the scrub begins at about 890 m. and consists of N. cliffortioides (dominant), N. Menziesii (both southern-beeches about 2.5 m. high) together with abundance of Dacrydium biforme and Leptospermum scoparium. Other constituents are: Phyllocladus alpinus, Pittosporum divaricatum, Pseudopanax lineare, Dracophyllum Lessonianum, Suttonia divaricatu, Olearia Colensoi and Senecio elaeagnifolius. The scrub of the Longwood Range (SO.) contains a good deal of N. Menziesii but there is much Dacrydium Bidwillii, so it may be considered an intermediate type.
Then there is the class almost confined to or extremely common on rocks but rare elsewhere, e. g. Asplenium Richardi, Microlaena Colensoi, Trisetum subspicatum, T. Cheesemanii, Agrostis subulata, Poa novae-zelandiae, Carex pyrenaica, Luzula pumila, L. Traversii, Pachycladon novae-zelandiae, Sisymbrium novae-zelandiae, Linum monogynum (excluding lowland stations), Aciphylla Monroi, A. similis, A. multisecta, A. Spedeni, Hebe tetrasticha, H. epacridea, Veronica linifolia, Shawia coriacea, Gnaphalium Lyallii, Helichrysum microphyllum, H. Selago, Leucogenes grandiceps, Senecio Haastii and S. Monroi. Taking these classes together it appears that 37 per cent of the rock-flora is composed of plants which are far and away more common on rocks than elsewhere, and it stands out clearly that the rock-vegetation is an entity quite as distinct as any other type of vegetation and not a mere collection of waifs and strays.
Taking next all classes of rock-plants together, the following are widespread common species: — Hymenophyllum multifidum, Blechnum vulcanicum, Pteridium esculentum, Polypodium pumilum, Podocarpus nivalis, Dichelachne crinita, Danthonia Raoulii var. flavescens, D. setifolia, the species of Koeleria, Poa caespitosa,, P. Colensoi, P. intermedia, Festuca novae-zelandiae, Agropyron scabrum, Schoenus pauciflorus, various vars. of Luzula campestris or allied species, Phormium Colensoi, Muehlenbeckia axillaris, Scleranthus biflorus, Stellaria gracilenta, Colobanthus acicularis, Tillaea Sieberiana, Acaena Sanguisorbae (various vars.), Coriaria sarmentosa, Hymenanthera alpina, Pimelea Traversii, P. prostrata, Epilobium pedunculare, E. glabellum, Lepto-spermum scoparium, Aciphylla Colensoi, Anisotome aromatica, Angelica montana, Corokia Cotoneaster, Gaultheria rupestris, Suttonia nummularia, Hebe epacridea, Veronica Lyallii, Celmisia bellidioides, Raoulia bryoides, Helichrysum Selago, H. bellidioides, Leucogenes grandiceps and Senecio bellidioides (or one of its near allies).page 283
Rock at various stages of plant-colonization is a common feature of the high mountains, but different ranges vary greatly in this regard. Speaking generally, the alpine belt and the river gorges of the lower levels are the most rocky localities. The volcanoes of North Island furnish much rock with their extensive lava flows (Fig. 76), weathered into fantastic forms. or, as huge blocks, piled one upon another. Mountain rock may form perpendicular cliffs, as in river gorges, much weathered crags, or be worn down to the level of the hillside. In any case, perfectly smooth rocks are rare and there are generally abundant crevices, ledges and hollows where soil can accumulate. The conditions offered for plant-life are most diverse according to the position of the rock with regard to sun, wind and moisture, and they range from intensely xerophytic to distinctly hygrophytic. Even opposite sides of the same gully often contain these opposing classes.
Ecologically, the species fall into obligate and facultative chasmophytes and soil-demanding plants. Such a soil is readily formed in a moist climate both on flat rocks and in depressions and hollows, so that a plant-covering may eventually be established not to be distinguished from that of the adjacent herb-field. At the same time, there are some species that especially affect soil-covered rocks, e. g. Anisotome pilifera, Dracophyllum Kirkii, Celmisia Walkeri, and, in general, herb-field species.
The life-forms of the 180 rock-plants are as follows: —trees dwarfed to shrubs 3, shrubs (often dwarfed) 58, grasslike-plants 21, rushlike plants 2, herbaceous and semi-woody plants 88 and ferns 8. Cushion-plants number 15, rosette-plants flattened to the rock 8 and cupressoid-shrubs 5.
As to the physiognomy of rock-vegetation, obviously all depends upon the species present, and this is governed entirely by the variety of rock-habitat they occupy. Frequently, the association is so open that it presents no striking features, but sometimes the shrub-form with some distinct species in excess, or the cushion-form, may be exceedingly striking.
β. The rock-communities.
North Island communities.
On the central volcanoes there are no obligate rock-plants. The vegetation is scanty and besides mosses and lichens consists only of deep-rooting desert or steppe xerophytes, especially, Danthonia setifolia, Poa Colensoi, Anisotome aromatica, Gaultheria rupestris and Helichrysum alpinum1.
1 1) This name I am giving to the North Island representative of Helichrysum bellidioides of South lsland (Xeranthemum bellidioides Forst. f., based upon material collected at Dusky Sound — F.) By Hooker the North Island plant was united with H. prostratum of the Subantarctic Province, but the figure of this species in the Flora Antarctica shows sessile flower-heads, whereas in H. alpinum, they terminate the branches, the extremities of which are drawn out into bracteate peduncles. From H. bellidioides, H. alpinum is at once separated by its wider, larger leaves which are There are other associations, distinguished by the presence — perhaps abundance — of other true rock-plants, e. g. Epilobium gracilipes with glabrous above. Grown, side by side, the two species are to be recognized at a glance. In the Lord Auckland Islands, as well as H. prostratum, there is H. bellidioides, and probably the two cross. In addition to the species cited, Veronica spathulata may be present, and on the great lava-flow from Te Mari (part of Mt. Tongariro) various subalpine-scrub shrubs are slowly being established.
On Mount Egmont most of the fell-field and tussock-grassland species occur on rock, but, in addition to the species of the last paragraph, the following need citing: Coprosma repens, Pentachondra pumila, Drapetes Dieffenbachii, Forstera Bidwillii and Celmisia glandulosa var. latifolia.
The Tararua Mountains, though subject to much rain, mist and cloudy skies, possess an extreme xerophyte in Raoulia rubra1, a typical vegetable-sheep, its cushions green however, and about 30 cm. diam. The other rock species are fell-field plants, e. g. Anisotome aromatica, A. dissecta, Pentachondra pumila, yellowish-green cushions of Phyllachne Colensoi, Helichrysum alpinum and Leucogenes Leontopodium. Where rocks are near subalpine-scrub, certain shrubs are present, notably Senecio Bidwillii (leaves very thick).
South Island dry mountains communities.
In the North-eastern and Eastern districts, in their upper montane and subalpine belts, the Colobanthus acicularis association occurs with that species dominant. This species is a small, pale-green cushion-plant, made up of very narrow leaves, ± 12 mm. long with long acicular points. The accompanying plants mostly come from the neighbouring tussock-grassland and are: Dichelachne crinita, Danthonia setifolia, Poa caespitosa, Festuca novae-zelandiae, Agropyron scubrun, Phormium Colensoi, Muehlenbeckia axillaris, Stellaria gracilenta, Scleranthus biflorus, Tillaea Sieberiana (semi-obligate rock-plant), Carmichaelia subulata, Discaria toumatou, Hymenanthera alpina, Leptospermum scoparium, Aciphylla Colensoi, Angelica montana, Cyathodes acerosa, Suttonia nummularia, Wahlenbergia albomarginata, Helichrysum bellidioides, Raoulia australis and Senecio bellidioides.
1 1) Apparently this crosses with Leucogenes Leontopodium, one of the hybrids being the so-called species Raoulia Loganii (Buch.) Cheesem. Elsewhere, similar hybrids occur between Leucogenes grandiceps and Raoulia bryoides one of which — described from one individual only — is Helichrysum pauciflorum T. Kirk. Probably Raoulia Gibbsii Cheesem., Leucogenes Grahami Petrie and a Stewart Island plant, originally referred by me to R. Longanii (in this case one parent would be R. Goyeni) are all edelweiß-vegetable sheep hybrids. H. H. Allan and myself have found a number of other forms to which we attribute the same origin, and we have given to all such the provisional hybrid generic name of × Leucoraoulia.
The Pachystegia insignis association, already described for the lowlands, ascends to upwards of 900 m. with Senecio Monroi as a member which — Pachystegia absent — dominates dry rock-faces up to 1500 m. or more altitude (NE.).
In the North-eastern district, in the upper subalpine and alpine belts, a strongly xerophytic station is provided by stacks of much-weathered greywacke standing out from vast shingle-slips (screes). A black fruticose lichen may dominate. Pressed as closely to the rock as possible will be numerous, hard, circular greyish cushions of Raoulia bryoides, the largest some 30 cm. diam. and 17 cm. deep. But the most striking plant, to which the name of the association must be given, is Helichrysum coralloides1; many of the following will be present: — Helichrysum Selago and H. microphyllum (closely related to H. coralloides), hybrids between the last-named and H. selago — but the 3 species rarely present at the same time, Hymenanthera alpina, forming rigid, open cushions of divaricating stem, Hebe decumbens or H. pinguifolia issuing from crevices, Pimelea Traversii, Colobanthus acicularis, perhaps the beautiful white-flowered Myosotis saxatilis, hard rosettes of Epilobium crassum and probably flattened sheets of Podocarpus nivalis. H. coralloides is confined to the North-eastern district, but dry alpine rocks in many parts of the Eastern and North Otago districts bear a closely-allied association2.
1 1) An open shrub some 40 cm. high, if sheltered, but a true cushion, if fully exposed (Figs. 64, 65); its shoots cylindrical, 8 mm. diam. and the small, glossy appressed leaves looking like tubercles, the spaces between being packed with white wool; the leaves are densely tomentose beneath and it is the hairs of adjacent leaves being entangled which makes the white wool, the actual stem being very slender and glabrous and not as stated by Cheeseman (1925:986) "⅓ in. diam. densely tomentose between the leaves". On shady rocks in gorges of the Inland Kaikoura mountains the shrub may exceed 90 cm. in height with the width equalling this height and the branches spreading and drooping.
2 2) Hebe pinguifolia, H. epacridea, H. tetrasticha, Gaultheria rupestris and stunted Leucogenes grandiceps are common in the Eastern district. Hebe Buchanani, and near the mountain summits Pachycladon novae-zelandiae occur in North Otago. Nasturtium latesiliquum, N. fastigiatum and N. Enysii with large rosettes clinging to the rock and far-penetrating thick root are local species occurring respectively in the North-western, the North-eastern and Eastern districts, but N. fastigiatum also extends into the Western district in the Mount Cook area, and N. Wallii (west of So.).
Communities of South Island wet mountains.
In the lower subalpine belt the rocks are altogether in the forest-areas, and when in the open occur only on river-beds or the sides of gorges. In such places, various forest-trees and subalpine shrubs are common jutting out from the rocks. In the wettest districts extremely steep cliffs may be actually covered with a close scrub, the rock having become faced with a thick sheet of soil held in position by a network of matted roots. A times, the whole of such a covering slips away for many metres leaving the steep rock-face bare and dripping. Rock of such gorges in the Western district at an early stage may be merely dotted here and there with various herbs and semi-woody plants, e. g, Veronica linifolia (the characteristic true rock-plant), Deyeuxia pilosa, Poa novae-zelandiae, Schoenus pauciflorus, Angelica montana, Epilobium glabellum, Veronica Lyallii, Craspedia uniflora (one or other of the jordanons), and Senecio Lyallii; extensive colonies of Phormium Colensoi are characteristic.
In the upper Clinton Valley, on the smooth face of the precipice where water constantly trickles, there is a curious association consisting of a close growth of a species of Hepaticae which is hidden by a prostrate grass, its culms pressed closely to the liverwort, pointing downwards and forming an open flat continuous mat. Numerous plants of Celmisia verbascifolia grow through the grass their leaves no longer erect but hanging downwards (Fig. 78). Drier cliff is occupied by a combination of Blechnum procerum, Phormium Colensoi and Coriaria angustissima, to be replaced as more soil accumulates, or where the cliff is less steep, by a shrub-association of Hoheria glabrata, Aristotelia serrata, Fuchsia excorticata and Hebe saliciflora var. communis.
The rocks of old moraine rising out of a subalpine herb-field, or steep buttresses, usually ice-worn, or the irregular, rocky walls of a gully rapidly become covered with peat — where such can rest or cling — made from bryophytes, lichens and early spermophyte settlers. Such stations are colonized by many species from the adjacent herb communities, as well as by a few obligate or semi-obligate rock species and others common on rocks. These include great mats of Hymenophyllum multifidum (epharmonic, curled-leaf form), Microlaena Colensoi, the prostrate Dracophyllum Kitkii page 287(NW., W.), Anisotome pilifera, Aciphylla similis, Celmisia Walkeri, and Leucogenes grandiceps; the shrubs Gaultheria fupestris, Coprosma serrulata and Senecio Bidwillii are common1).
The alpine rocks, if steep, have a sparse vegetation which will include some of the following (the extreme altitudes are mostly from A. Wall, (1925: 19, 20): —Hymenophyllum multifidum, Polypodium pumilum, Microlaena Colensoi, Agrostis subulata, Poa novae-zelandiae (2100 to 2400 m.), Carex pyrenaica, C. acicularis (2400 m.), Marsippospermum gracile (2100 m.), Luzula pumila (2400 m.), Colobanthus acicularis (2400 m.), Hectorella eaesfitosa (2100 m.), Ranunculus Buchanani (SO., F., 2100 m.), R. Grahami (W. in Mount Cook area, 2700 m. and more), Nasturtum Enysii (2400 m.), N. Wallii (SO.), N. fastigiatum, N. latesiliquum (NW.), Cardamine depressa, Pachycladon novae-zelandiae, (SO., F. — 2100 m), Hymenanthera alpina (2100 m.), Epilohium rubromarginatum (NW., W., 2400 m.), Schizeilema Haastii (2100 m.), S. exiguum (NO., SO., F.), Aciphylla Hectori (NO., F., SO.), A. Spedenii (SO., 1800 m.), A. Dobsoni (NO., SO — 2100 m.), A. simplex (SO., 1800 m.), Angelica montana, Anisotome imbricata (SO., F.), Gentiana sp., divisa, (W., Mount Cook area, 2400 m.), Myosotis suavis (east of W., 2100 m.), M. macrantha, M. pulvinaris (SO.), M. concinna (NW.), Hebe ciliolata (2100 m.), H. epacridea (2100 m.), H. Haastii (over 2700 m.), Celmisia brevifolia (SO.), C. Hectori (SO., F., W. 1800 m., C. ramulosa (SO. F.), Raoulia eximia (2100 m.), R. Buchanani (SO., F.), R. Youngii (W., SO.), R. subulata, Leucogenes grandiceps and Cotula pyrethrifolia.
Stewart Island rocks.
Almost any of the subalpine plants may be found on rocks. This is not because they are specially adapted for such a station, but because peat is readily formed in the mountain climate on flat rock surfaces or in crevices, and because the frequent rain never allows the rocks to become too dry for bog xerophytes. The following are the only special rock-plants: Polypodium pumilum, Anisotome flabellata, Raoulia Goyeni and Helichrysum grandiceps.
b. Vegetation of loose, stony debris.
1. The shingle-slip formation and allied communities.
1 1) The following are some of the herb-field species of such rocks: Pachycladon novae-zelandiae (SO., F.), Coriaria angustissima, Acaena Sanguisorbae vars. pilosa and sericeinitens, Epilobium chloraefolium var. venom, E. Matthewsii (F.), Anisotome Haastii, A. capillifolia (SO., F.), Aciphylla divisa (W., SO., F.), A. mvltisecta (F.), Veronica catarractae (F.), V. Lyallii, Ourisia caespitosa, O. sessilifolia, O. prorepens (SO., F.), O. qlandulosa (F., SO., NW.), the so-called Plantago Brownii, P. lanigera, Forstera tenella, F. sedifolia and var. oculata, Celmisia Gibbsii (NW.), C. rupestris (NW.), C. Du Rietzii (W., NW. — part of C. Sinclairii of the Manual), C. discolor (= C. intermedia Petrie NW., W.), C. Bonplandii (SO., F.), C. petiolata, C. verbascifolia (SO., F.), Craspedia uniflora in a wide sense, Senecio bellidioides, S. southlandicus (SO.), S. scorzoneroides.
The species fall into two classes — obligate (25 species) and facultative (8 species) — and taking both classes together the 33 species belong to 14 families and 19 genera. The following list includes all the species: — obligate) Poa sclerophylla, Stellaria Roughii, Ranunculus Haastii, R. chordorhizus, R. pauciflorus, R. crithmifolius, Notothlaspi rosulatum, Swainsona novae-zelandiae, Epilobium pycnostachyum, Anisotome carnosula, A. diversifolia, Convolvulus fracto-saxosa, Myosotis Colensoi = (M. decora), M. Traversii, M. angustata — perhaps, M. Cockayniana, Hebe macrocalyx, Veronica Cheesemanii, Lobelia Roughii, Wahlenbergia cartilaginea, Haastia Sinclairii, H. recurva and var. Wallii, Raoulia cinerea, Craspedia alpina — forms in fell-field may be identical —, Cotula atrata and var. Dendyi and the hybrids between them, (facultative), Claytonia australasica, Notothaspi australe, Acaena glabra — almost obligate, Anisotome filifolia, Hebe lycopodioides, H. tetrasticha, H. epacridea and Haastia pulvinaris.
The station, as will be seen from what follows, is strongly hostile to plant-life and but few species are so constructed as to be able to gain a footing, or, if such should happen, to thrive and produce offspring.
The much-jointed greywacke and allied rocks, which comprise the greater part of New Zealand mountains, become so rapidly disintegrated that stone-fragments accumulate to such an extent as to cover the slopes for hundreds of metres. Here and there jagged masses of much corroded rock jut out from these stone-fields but hardly break the monotone of the vast, grey even slopes which extend from the lower subalpine-belt to the mountain-tops. Gullies, often with rocky walls seam the mountain sides, their floors occupied by a stream, its source the base of some great stone-field where all on a sudden water bursts forth.
The stones themselves differ in size but the bulk are generally small, perhaps 5 or 6 cm. long by 2 cm. broad, though some may be much larger. Those of the upper layer are quite loose and, as the surface is steep, they are liable to slide downwards, considerable breadths, when disturbed, moving en masse. At 30 cm. or more below the surface, the ground is more stable and there is generally a good deal of finer debris, sand, and even clay mixed with the coarser stones. Although quite dry on the surface, at a few centimetres depth the substratum is damp, and deeper still ample water, but icy-cold, is available for plants. The climatic features of the habitat depend upon extreme exposure to wind; strong radiation of heat from the stones; powerful heating of the stones themselves and, at times, very bright light. Within the space of a few hours the plants are frequently subjected page 289to burning heat and considerable frost, or one hour they may be surrounded by moist air and the next be exposed to a strong, dry wind. Those which are evergreen bear a heavy weight of snow for four months at a time or more. Nor are occasional droughts unknown. It is obvious then that the ecological conditions of shingle-slip are distinctly those of desert, while in addition there is marked instability of surface. This latter character has, in part, led to the occupation of the ground not merely by certain peculiar life-forms but by 25 distinct species which do not occur in any other formation.
Near the edges of the shingle-slip, the stones are far less liable to move, and there is stability - sufficient for species other than those adapted to the moving debris to settle down, so that, by degrees, the formation is transformed into fell-field. But towards such change the actual shingle-slip association contributes nothing, its members are too far apart and too few to supply appreciable humus to the soil. The formation is indeed distinct in itself and not a phase in the development of fell-field but a definite vegetation-entity the origin of which is wrapped in obscurity.
Shingle-slip, in its unstable and typical form, is confined to those mountains of South Island with a tussock-grassland-climate and is most strongly in evidence in the North-eastern and Eastern districts. Where there is abundant rain the conditions for accumulation of debris are unfavourable, while its occupation by non-shingle plants is much more easy. Certain scoria-slopes of North Island volcanoes are ecologically similar to true shingle-slip.
Taking both the obligate and facultative species together their life-forms are as follows: — herbs 21 (summergreen 14, evergreen 7), semiwoody plants 4, grass-form 1, shrubs 5, biennials 2. Most of the obligate species have important features in common and several of distinct affinities closely resemble one another. Thus, 17 are much the same colour as the stones; all have thick, fleshy or coriaceous leaves and in 24 species they are in rosettes; underground stems more or less strongly developed occur in 17 species, while in 16 the portion of the plant above the ground is annual; with but 2 exceptions, the shoots lie close to the stones and, although this leads to their being buried, the stems have the faculty of growing upwards, while the leaf-texture in many is such as not to be readily damaged by rolling stones. The roots generally extend, in part, horizontally and then descend more ore less deeply. Twenty one species are glabrous, but, on the other hand, the species of Haastia and Craspedia alpina are woolly, the latter being very noticeable through its long, snow-white wool.
β. The associations of true shingle-slip and their allies.
Those of the South Island dry greywacke mountains.
On the dry greywacke South Island mountains most of the shingle-slip species occur page 290at some point or other, the southern limit being the Takitimu Mountains. In some places, Stellaria Roughii is alone present, since it probably can occupy a more unstable position than any other species. But, generally, Poa sclerophylla, Notothlaspi rosulatum (Fig. 79), Ranunculus Haastii, Anisotome Haastii, Epilobium pycnostachyum, Lobelia Roughii, Craspedia alpina and Cotula atrata are present, and such, together with Hebe epacridea, H. lycopodioides and H. tetrasticha is the usual association of the Eastern district. The plants occur only here and there, indeed one may examine a shingle-slip for hundreds of metres and find no plants or, at best, a solitary example of Stellaria Roughii. On the fairly stable ground near the head of the debris-field there may be a few grey mats of the semi-woody Haastia recurva.
In the North-eastern district the association is richer than in the Eastern, for, in addition to the species cited above, are Wahlenbergia cartilaginea — a rosette-plant somewhat resembling a European crusty saxifrage — Myosotis Cockayniana, Convolvulus fracto-saxosa, Raoulia cinerea (rare) and Swainsona novae-zelandiae (also E., but apparently rarer).
On fine limestone debris at Castle Hill (E.) there is a distinct association at an altitude of 600 m., and rather more, with the following composition the species marked* being restricted to the above locality. The stony slope is fairly stable and its margin much more so than for shingle-slip in general. On the unstable debris are: Notothaspi rosulatum, in great abundance; Ranunculus pauciflorus*, but confined to one small area; Myosotis Traversii; and, where stable, M. Colensoi*; Poa acicularifolia; Lepidium sisymbrioides, with extremely long roots; Oreomyrrhis andicola var. rigida; Senecio lautus var. montanus and Carmichaelia Monroi.
The Haastia pulvinaris association.
This association is characteristic of the alpine belt of the North-eastern district both in its driest part and at its junction with the North-western district. Haastia pulvinaris is exactly of the same cushion-form (Fig. 58) as the other great vegetable-sheep, Raoulia eximia, already described, but the shoots are much thicker and the leaves larger and more woolly. The great pale-yellow cushions 2 to 3 m. long and 60 cm. or more thick may dot the shingle-slip as far as the eye can reach. The larger examples grow amongst the biggest stones but certainly, in many cases, are not attached to the underlying rock. They do not seem to grow on the finer debris. They are usually much longer than broad, an this is accentuated by de sliding stones from above piling up against them so that the upper surface may be partially buried. Many deaths take place from such burials. Various species are epiphytic on the cushions especially, Danthonia Raoulii var. flavescens, D. setifolia, Celmisia spectabilis and C. viscosa.
The association of the Western district.
Nearly all the eastern shingle-slip species are absent and various herb-field or fell-field plants are present page 291especially Podocarpus nivalis, Acaena Sanguisorbae var. sericei-nitens, Epilobium glabellum, Oxalis lactea, Geranium microphyllum, Cotula pyrethrifolia, Celmisia Du Rietzii and great sheets of Leucogenes grandiceps. True shingle-slip plants are represented by Epilobium pycnostachyum, Hebe macrocalyx, Veronica Cheesemanii and Haastia Sinclairii (distinct from the Fiord var.), while Epilobium rubro-marginatum (semi-shingle species) is frequently abundant at the highest altitudes.
Vegetation of scoria slopes (VP., EW.).
The scoria slopes of the Volcanic Plateau, and Mount Egmont, present conditions quite as severe as true shingle-slip and, as on certain slopes of Mount Ngauruhoe, may be without plant-life. But there are often a few species distantly dotted about especially: Luzula Colensoi, Claytonia australasica, Gentiana bellidifolia (Fig. 80), Anisotome aromatica1, Poa Colensoi and Gaultheria rupestris. The most characteristic plant of Ruapehu &c. for this station is Veronica spathulata2 (Fig. 62).
Vegetation of rock-slides.
This association or group of associations is distinguished by the presence of certain species of Ranunculus and the local var. of Haastia Sinclairii. It was first described by J. Simpson and J. S. Thomson (1926:376–77) who proposed the name "rock-slide".
The station consists of large blocks of stone the spaces between which filled with far smaller particles form the rooting-places for the plants. The large rocks "broken and thrown into vast slopes" are comparatively stable; they cover large areas and are bare of vegetation. On Rough Peaks (the area investigated by the above botanists) the association consists of Haastia Sinclairii, as above, Ranunculus Scott-Thomsonii — a true debris-plant with stout rhizome and rosettes of trifoliolate leathery, grey, glabrous leaves, a polymorphic hybrid swarm between the latter and a var. of R. Buchanani growing in its vicinity, and occasional patches of the silvery Celmisia Hectori.
On Tooth Peaks (junction SO. and F.), at an altitude of about 1050 m. where the stones are very large, the vegetation is more of a fell-field character and consists of yellowish-brown mats of Podocarpus nivalis, almost black open cushions of Hymenanthera alpina and plants of Aciphylla maxima. There is also some Acaena Sanguisorbae var. pilosa, Muehlenbeckia axillaris, Coprosma propinqua, Senecio cassinioides and a good deal of Pimelea prostrata.
1 1) This may be an epharmone or a distinct variety; at any rate it has a true debris form with coriaceous leaves and an extremely thick, deeply-descending tap-root.
2 2) A prostrate herb or perhaps semi-woody plant forming a close soft mat upon the ground composed of flexible, decumbent stems branching freely near their extremities; the leaves are small, hairy, soft and thick; the root of extraordinary length giving off many close, more slender secondary roots; and the flowers large, for size of plant, white and produced in the greatest profusion (Fig. 62).
2. Vegetation of river-beds, fans and allied habitats.
This has been described at some length for the lowland and montane belts and the definition given for its class of vegetation applies here also. The physiographical and ecological conditions as there indicated match closely those of subalpine river-bed, as far as the larger rivers are concerned, except just at their glacier sources. Even the species are much the same, as is the procession of events in plant-colonization. Such differences, as there are, arise from climate and the colder water of the substratum, while certain species, according to locality, are present which do not descend to or are rare in the lowland belt. Lowland river-bed of the Western and Fiord districts however approximates closely to that of the mountains.
The South Island species, omitting those of fell-field or herb-field which occur in the upper torrent beds, number about 72 and belong to 23 families and 38 genera. Their life-forms are as follows: — grass-form 11 species, herbs 32, semi-woody plants 18 and shrubs 11. At most 10 species belong to the high-mountain flora but nearly all of these descend to the lower montane belt. As in the lowlands the most important members of the formation are the species of Epilobium and Raoulia1 with E. melanocaulon characteristic of the dry areas and E. glabellum of the wet. Other common species are the grey, low shrub Helichrysum depressum looking half-dead with grey rigid stems and scanty small appressed leaves; great circular mats of Muehlenbeckia axillaris; several species of Acaena; Veronica Lyallii in the wet and V. Bidwillii in the dry areas or stations; Helichrysum bellidioides, Coriaria lurida; C. angustissima (where abundant rain) and the vast polymorphic hybrid swarm between them in which C. sarmentosa also plays a part, Veronica catarractae (F.), Angelica montana, Discaria toumatou and Raoulia glabra. Raoulia Haastii, which forms large green cushions, is the characteristic plant of many river-beds in the Eastern and Western districts and occasionally occurs in the South Otago district.
Subalpine torrent beds of the wet mountains, especially near their sources, contain more or less of the fell-field and herb-field species and their open plant-covering may resemble that of the adjacent fell-fields. So, too, the old bed of the wider valleys often has a considerable florula and the association may be closed, but it is generally rather tussock-grassland dotted with shrubs than fell-field. Hebe buxifolia var. odora and Carmichaelia grandiflora are common on old river-bed on the wet eastern side of the Divide (W.), Coprosma brunnea, its wiry stems hugging the stones, is characteristic, and soft cushions of Myosotis uniflora occur occasionally.
1 1) E. pedunculate, E. glabellum, E. melanocaulon, E. microphyllum, E. rostratum, E. macropus, R. tenuicaulis, R. Haastii, R. glabra, R. australis, R. Parkii (where the climate is specially dry) and R. lutescens.
Vegetation of fans.
The vegetation is that of river-bed and commences with the usual species of Epilobium and Raoulia. Finally tussock-grassland or Discaria scrub may be established but the indermediate stage may possess many circular mats of Muehlenbeckia axillaris and extensive colonies of the ferns Blechnum penna marina and Hypolepis Millefolium.
The association occurs principally in the drier areas and the fans — sometimes of great size — are built up by the stony debris deposited at the mouths of gullies or gorges by their streams as they open out on to the valleys, river-beds or plains. Their vegetation depends upon the supply of stones brought down by the torrent and this again is correlated with the age of the gully and the plant-covering of its walls. Fans may be either active or passive, and every transition between the two can be seen. The stony surface is much steeper than that of river-bed in general. There are water-channels but these are usually dry except during heavy rain, the actual stream running underground. Many of the stones are large and much of the debris coarse and piled up into comparatively high but quite unstable terraces liable during flood to damage or absolute destruction.
Closely related to fan vegetation, on the one hand, and to Hebe scrub, on the other, especially in the Eastern district, is an open association with Hymenanthera alpina dominant and, growing between the stones, Hypolepis Millefolium and Blechnum penna marina. The other members of the community are frequently Geranium microphyllum, species of Acaena and their many hybrids, Myosotis australis (yellow flowers, probably not identical with the Australian species), and various shrubs, especially Discaria. The substratum consists of large, lichen-covered stones either at the foot of river-terrace or at the base of mountain slopes, particularly in the montane and lower subalpine belts. Cystopteris novae-zelandiae is common beneath the shrubs.
c. The fell-field, grassland and herb-field series of communities.
This series of communities is considered under one head, though each is probably a distinct formation, for they intergrade so constantly that no hard and fast line can be drawn between them. This resemblance has become greatly intensified during the past 76 years through the sheep-farmer burning the vegetation and through the changes wrought by overstocking with sheep, cattle, rabbits, deer, and other grazing and browsing mammals. At the present time, induced fell-field is to be seen, but little different, if different at all, from virgin fell-field, where, originally, tussock-grassland, or even forest, ruled. Burning tall tussock-grassland rapidly transforms this vegetation-type into low tussock-grassland, whilst burning the latter, year by year, leads to erosion of the substratum and the incoming of fell-field. And still further burning in the presence of sheep &c., brings about a habitat page 294where only obligate or facultative shingle-slip species, or xerophytes of river-bed, can gain a footing.
Though the foregoing state of affairs applies particularly to the dry South Island mountains, it must not be thought that the plant-covering of the wet mountains is altogether virgin. Even there burning, on the one hand, and deer, on the other, have led to great changes and, lacking a clue, the modified community would unhesitatingly be considered primitive. Nevertheless, there are many wide areas where virgin vegetation can still be seen, especially on certain North Island mountains and in the North-western, Western, Fiord and Stewart districts.
Not only does the presence of exotic species indicate modification of the plant-covering, but even the superabundance of certain indigenous species. For instance, in the lower subalpine belt of dry mountains, profusion of Celmisia (Fig. 55), Chrysobactron, Acaena and Phormium Colensoi must be looked at askance. On the other hand, with but few exceptions apparently few, if any, indigenous species, absent in a virgin association, seem to have gained a footing in those now modified or induced, nor are the exotic aliens of real importance in forbidding the entry, or spread, of the true members of a community.
The fell-field formation consists of a group of associations of an extremely open character made up, for the most part, of low-growing xerophytes or subxerophytes and with tussock-grasses present only to a quite limited extent.
The number of species, including a few of the commoner hybrid swarms, is 282 which belong to 40 families and 96 genera, of which the most important are: — (families) Compositae 62, Gramineae 34, Scrophulariaceae 30, Umbelliferae 17, Ranunculaceae 12; (genera) Celmisia 26, Hebe 16, Ranunculus 12, Acaena and Coprosma 7 each.
The following are common species of wide range:— Blechnum penna marina, Lycopodium scariosum, L. fastigiatum, Podocarpus nivalis, Deyeuxia avenoides, Danthonia Raoulii var. flavescens (in a wide sense) and var. rubra, D. setifolia, Poa Colensoi, P. Lindsayi, Festuca novae-zelandiae, Uncinia compacta, Marsippospermum gracile, Astelia Cockaynei, Exocarpus Bidwillii, Muehlenbeckia axillaris, Claytonia australasica, Stellaria gracilenta, Colobanthus crassifolius, Geum parviflorum, G. leiospermum, Acaena Sanguisorbae var. pilosa, Acaena microphylla, A. inermis and hybrids between the three species, Carmichaelia Monroi (in a wide sense), Geranium sessiliflorum var. glabrum, Coriaria lurida, C. sarmentosa, × C. sarlurida, Discaria toumatou, Viola Cunninghamii, Hymenanthera alpina, Pimelea prostrata, P. pseudo-Lyallii, Drapetes Dieffenbachii, Leptospermum scoparium, Epilobium tas-page 295manicum (in a very wide sense), E. Hectori, E. chloraefolium var. verum, E. peduncular e (in a wide sense), E. glabellum, E. novae-zelandicae, Hydrocotyle novae-zelandiae var. montana, Aciphylla Colensoi, A. squarrosa (in a very wide sense), Gaultheria rupestris, Pentachondra pumila, Cyathodes Colensoi, Leucopogon Fraseri, Dracophyllum uniflorum, Suttonia nummularia, Gentiana corymbifera, Myosotis australis (probably distinct from the Australian species of that name), Pygmaea pulvinaris, Ourisia caespitosa, Euphrasia revoluta, E. zealandica, Pratia macrodon, Forstera Bidwillii, Phyllachne Colensoi, Celmisia Du Rietzii, C. discolor (= C. intermedia Petrie), C. spectabilis, C. viscosa, C. laricifolia, C. longifolia, C. Lyallii, C. Haastii, Gnaphalium Traversii, Raoulia grandiflora, Helichrysum bellidioides, Cassinia Vauvilliersii, Craspedia uniflora (in a very wide sense), Cotula pectinata, C. pyrethrifolia and Senecio bellidioides ore one of its near allies.
Fell-field vegetation occurs on all the dry mountains but on the wet mountains only on especially stony ground or on a substratum subject to strong erosion; it is absent in Stewart Island. Vertically, it occupies more or less of the subalpine and alpine belts, but, in ascending, the species decrease considerably in number, though a few, absent below, reinforce the depleted community. The greatest development of fell-field is on the dry greywacke mountains of South Island, but it must be emphasized that much is merely induced through the burning of tussock-grassland or Nothofagus forest.
Fell-field falls naturally into that of dry and of wet mountains. Naturally too, the ecological conditions supplied by these opposite classes differ considerably, but the fundamental factors governing the formation as a whole are everywhere similar. Foremost, stands out the unstable substratum due to frequent erosion, rapid or insidious, dependant upon rain and wind in relation to a more or less friable surface, or to readily-moved stony debris. Such a substratum is altogether hostile to a closed community, so the excess of bare ground readily becomes the sport of wind and water, while that bearing vegetation is easily undermined. Then, on exposed parts of the mountains, especially ridges, summits and slopes facing the full blast of the wind, only those plants which hug the ground or form dense cushions can exist, even though the substratum be stable enough. Also very shallow soil favours fell-field. The deep snow-covering of the alpine belt leads physically to erosion during its melting and ecologically to a growing-period of short duration and ice-cold water for the roots. The plants are continually exposed to frost, except in winter when lying under their covering of snow, and, though these frosts are not really severe, a plant may be frozen hard during the night and exposed to strong insolation early in the day. In short, fell-field conditions are less favourable for vascular plants than those of any other high-mountain habitat, shingle-slip excepted.
Coming now to the life-forms, the main classes and number of species to each class are as follows:—shrubs 60, semi-woody plants 54, herbs 116, page 296grass-form 47, rush-form 1 and ferns 4. With but few exceptions, the plants are of very low stature no less than 144 (51%) being prostrate or close to the ground, while hardly any of the remainder exceed 30 cm. in height, the greater part being much less. There are 28 cushion-plants but in the most exposed positions certain species, usually erect, assume that form or else are flattened to the ground. As for the erect species, 10 are tussocks and some 15 have rigid stems or leaves (Aciphylla). As for leaves, these are small in 200 species (71%), most being very small and 5 species are leafless and several, leafy elsewhere, almost leafless, and in nearly all the species which also occur in other formations their leaves are reduced considerably beyond their average size. With regard to texture, nearly all the species have coriaceous, thick, hard or stiff leaves and those of the grasses are rolled. In fact, fell-field plants stand in harmony with the violent, frequent, long-persisting winds.
The life-history of fell-field is fairly clear and on most mountains its beginnings, its prime, and its destruction can be seen. Its earliest stage is the sparse colonization by xerophytes — some coming from neighbouring rocks — of stony debris (e. g. margin of shingle-slip) so soon as this is sufficiently stable. In course of time, should nothing upset this stability, a small amount of humus will accumulate, the stones themselves will break up into fine particles, fairly good seed-beds will be established, particularly through the incoming of mat-plants, and species from tussock-grassland or herb-field can enter the community; indeed, if stability is maintained, as on the flattest ground, well-watered by melting snow, or in hollows where snow lies long, considerable patches of closed vegetation may be established — oases, as it were. On the contrary, the disintegration, ever in progress, renders fell-field far from long-lived it being in a constant state of destruction and renewal. A heavy snowfall is before all else the most powerful factor for damage on a large scale, since it leads to snow avalanches which tear up the surface destroying all vegetation and depositing the remains on the gully-floor hundreds of metres below. Seeds germinate well enough, when they get the chance, and in New Zealand at any rate it is not as Warming suggests (1909:256) a relation between seed-germination and climate that determines the openness of fell-field, but largely the disintegration factor.
At the present time, in lower-subalpine fell-field, though the associations look virgin enough, except for a few exotic species of no real moment, in many cases it is indigenous-induced as already explained. To cite a few examples of induced fell-field there is that of Porter's Pass (E.), Jack's Pass (NE.) and the lower subalpine slopes of Mount Ida (NO.).
β. Fell-field of the dry mountains or a specially dry substratum.
This well-marked community is distinguished by the dominance of Dracophyllum recurvum, together with certain shrubs — page 297usually more or less prostrate — and a few low-growing herbs and semi-woody plants.
The species number about 54 (families 21, genera 37) of which the following are important: — Gleichenia circinata, Podocarpus nivalis, Dacrydium laxifolium, Danthonla setifolia, Pimelea prostrata, Gaultheria rupestris, Dracophyllum recurvum, Epacris alpina, Pentachondra pumila, Gentiana bellidifolia, Hebe laevis, H. tetragona, Ourisia Colensoi, Euphrasia tricolor, Coprosma depressa, Celmisia spectabilis and Raoulia australis var. albo-sericea.
The association under consideration occurs on the Volcanic Plateau and mountains adjacent at an altitude of 1080 to 1350 m. Apparently, there is a related association on the Ruahine Mountains.
The habitat strongly favours xerophytes. The soil to a great depth, is merely pumice, scoria and andesitic lava mixed with sand from their desintegration. Where level, and sufficient plants are present, there is a layer of black sandy humus 2.5 to 5 cm. deep, the dryness of which leads to its being blown away. The water-holding capacity of the soil is of the slightest, and the water-table lies far below the surface, moreover the evaporating action of sun and wind comes strongly into play. On a cloudless summer day, the surface-soil becomes burning hot to the hand and the heat penetrates markedly for at least 7 to 8 cm. The easily-moved soil brings about conditions similar to those of a dune-area, in fact dunes occur. Where there is absence of water and exposure to wind, desert pure and simple results, but with increase of humidity comes a denser plant-covering and the entry of more mesophytic species.
Regarding the life-forms there are 30 shrubs, 15 herbaceous and semi-woody plants, 7 grasslike plants, 1 moss and 1 fern. About 61 per cent are more or less prostrate; the cushion, ball-like, needle-leaved, divaricating, leafless and tussock forms are represented. Dracophyllum recurvum itself forms rounded, open cushions or low mats, 60 cm. diam., made up of much-branching, rigid stems bearing apical semi-rosettes of strongly recurved, reddish-orange, stiff leaves each 1.2 to 3.8 cm. long.
The landscape varies from a plantless expanse of scoria, by way of a most open covering of a few species, to one almost closed where the whole florula is present. The abundance of Dracophyllum recurvum gives a general reddish or reddish-brown colour to wide areas. Where denser, yellows, pale greens, yellow-greens and silver make a coloured patchwork and, where densest, the species, more or less flattened to the ground, form irregular oases of considerable size, but under unfavourable conditions the black scoria is merely dotted at distant intervals by silvery patches of the Raoulia, small straw-coloured tussocks of Danthonia setifolia, vivid green semi-cushions of Pimelea prostrata and isolated dark rosettes of Gentiana bellidifolia (Fig. 80), but the scene is one of desolation. More consolidated ground is occupied by reddish-orange patches of Dracophyllum recurvum raised but a page 298few centimetres above the substratum or as higher sand-filled cushions; cushions of the flat-stemmed, leafless Carmichaelia orbiculata (Fig. 81) occur occasionally, and epharmonic cushions of Dacrydium laxifolium (Fig. 70). On the "oases", the shrubs &c. growing mixed together catch the flying sand and build irregular mounds 30 cm. high with the margins either ragged or hold firmly by a close mat of D. laxifolium or Podocarpus nivalis which may extend out to the bare ground. Dunes are occupied by the same species as the mounds, but in addition there may be Coriaria lurida, Muehlenbeckia axillaris, Olearia nummularifolia, Phyllocladus alpinus and stunted Nothofagus cliffortioides.
The subalpine group of associations of the dry South Island mountains.
This group is distinguished by the special physiognomic importance of great sheets of Podocarpus nivalis and low, depressed brownish bushes of Dracophyllum uniflorum, together with (generally) various species of Celmisia, yucca-like Aciphylla Colensoi and tussocks of Danthonia Raoulii var. flavescens.
At a low estimate the number of species and hybrid swarms (9) is 140 (families 33, genera 65). As so many species are mentioned in what follows no list is given here.
The group of associations is found on those mountains situated outside the average line reached by the westerly rainfall and is restricted to the Sounds-Nelson, North-eastern, Eastern and North Otago districts. It extends vertically from about 900 m. to 1200 or even 1500 m. altitude, but the altitude reached and its area are determined by the nature of the substratum, clay favouring tussock-grassland and rock-debris fell-field.
Viewed from some lofty ridge in the North-eastern district, grey mountain slopes in all directions meet the eye apparently quite devoid of vegetation, indeed nothing could appear more desert-like (Fig. 67, in background). To be sure, not all the dry mountains look so barren but they rarely possess anything like a continuous covering throughout the subalpine and alpine belts, but show, at best, vast debris-fields divided by narrow triangular lines or strips of vegetation which descend towards the brown tussock-grassland or dark forest. Such lines, or patches, raised slightly above the general level stand out from the desert of unstable stones. A closer view shows that there is rarely a continuous plant-covering. Patches of clayey, stony soil, large or small, abound containing sometimes the remains of dying plants, the long roots exposed, but rarely are they to be seen in process of occupation.
The soil is of diverse origin and may be stones merely (e. g. consolidated shingle-slip), loess, glacier-clay or clay from underlying rock. It is obvious, that through unstability of the substratum, these soils must frequently be mixed together. As plant-colonization proceeds, a variable amount of humus accumulates and the soil becomes more or less loamy. The water-content varies much according to the season of the year and to position with regard to page 299the sun, a certain average shade favouring closed vegetation; if the number of rainy days be sufficient.
The physiognomy of the vegetation depends, in the first place, upon the yellowish mats of Podocarpus nivalis rooted amongst the stones and extending for several metres and upon the spreading, rather open brown bushes of Dracophyllum uniflorum, which give a brownish hue to subalpine slopes conspicuous even from the base of the mountain. Low, dark cushions of the almost leafless divaricating-shrub Hymenanthera alpina (Fig. 83, but not subalpine in this figure), small hard-leaved plants of Gaultheria rupestris and the glaucous-leaved species of Hebe, with prostrate gnarled black stems and imbricating leaves crowded near the ends of the branches are all plants of particularly dry and exposed stations. Other shrubs of dry ground are Carmichaelia Monroi (forming open, low cushions of short, broad, leafless, rigid, flat stems) Cyathodes Colensoi (dark-coloured mats), prostrate Dracophyllum pronum. On certain mountains from the North-eastern to the North Otago district grows the remarkable Corallospartium crassicaule, an intensely xerophytic shrub with a stout, rigid, sparingly-branched, yellow grooved stem, 1 m. or more high, and about 2 cm. diam.
The abundance of herbs and semi-woody plants, nearly all prostrate or low-growing, depends upon the degree of moisture in the soil. Where dry, but few species are present, especially Scleranthus biflorus, Muehlenbeckia axillaris, Colobanthus crassifolius, Acaena inermis, A. Buchanani (Central Otago and Mackenzie Plain), Geranium sessiliflorum var. glabrum, Pimelea pseudo-Lyallii, P. sericeo-villosa (NE. to NO.), Drapetes Dieffenbachii, Hydrocotyle novae-zelandiae var. montana, Pratia macrodon, Helichrysum bellidioides, Cotula pyrethrifolia, C. pectinata and Senecio lautus var. montanus.
Moister places, especially where shaded, contain a richer vegetation, which of course may include many of the above. Green mats of Ourisia caespitosa (showy when one mass of white blossom) are characteristic. The following may also be present: Ranunculus Enysii, R. Monroi or var. dentatus, R. multiscapus, R. Sinclairii, R. gracilipes, Geum parviflorum, Geranium microphyllum, Oxalis lactea, Viola Cunninghamii, Drapetes Lyallii, Epilobium pedunculare (in a wide sense), E. chloraefolium, Schizeilema hydrocotyloides, Oreomyrrhis andicola (in a wide sense), Anisotome aromatica, Gentiana patula, Myosotis pygmaea (in a very wide sense), Veronica Lyallii, V. Bidwillii, Euphrasia Monroi, E. revoluta, E. zealandica, Plantago Brownii, Coprosma repens, Wahlenbergia albomarginata, Forstera sedifolia, F. Bidwillii, Craspedia (one or other of the species), Senecio bellidioides and Taraxacum magellanicum.
The alpine group of associations of the dry South Island mountains.
This group is distinguished by the extremely open character of the vegetation and the presence of a few species rarely seen below 1200 m. altitude, or generally higher, e. g. Luzula pumila, L. Cheesemanii (rare and local) and page 300Pygmaea pulvinaris. The species number about 65 (families 22, genera 42), but only some 45 belong to fell-field proper. The most important species are mentioned below.
The habitat consists for the greater part of consolidated debris similar to that of shingle-slip but stable for the time being. There are, however, hollows where snow lies for a long time, the vegetation of which is closed more or less and far richer in species; indeed, it really stands in a category by itself and is related, on the one side, to herb-field and, on the other, to the carpet-grass association. Indeed, its ecology and species are distinct from those of fell-field, nevertheless it is convenient to deal with it here. For fell-field proper the ecological conditions are much the same as for shingle-slip vegetation, so far as heat, cold, rain, snow and wind are concerned, but the stable substratum puts the plants in a different class so far as their life-forms are concerned.
At a certain altitude, differing considerably according to the ecological conditions, the vegetation of the mountain-side changes all on a sudden, and the alpine-belt commences. The first indication is the incoming of great mats of the stiff-leaved Celmisia viscosa and the thin-leaved C. Haastii — species which affect ground abundantly watered by melting snow. Celmisia incana (west of NW.), accompanied by Danthonia australis, occupies a similar position.
As members of the fell-field proper, there will be in some part or other of the community the following: — Claytonia australasica, Epilobium tasmanicum (in a wide sense), Schizeilema hydrocotyloides, S. Roughii (NE.), one or more of the Aciphylla Monroi group, Gaultheria rupestris, Pentachondra pumila, Hebe tetrasticha (E.), H. Cheesemanii (parts of NE.), H. epacridea, H. decumbens (SN., NE.), Pratia macrodon, Wahlenbergia albomarginata (epharmone, compact and thick-leaved), Phyllachne Colensoi (dense, green cushions), Celmisia laricifolia (low cushion or mat), Raoulia grandiflora, R. bryoides (usually a rock-plant), Leucogenes grandiceps (usually a rock-plant), and low, dark-coloured mats of Cotula pectinata.
Fell-field dependant on the chemical nature of the substratum.
On the Dun Mountain (SN.) at an altitude of less than 900 m., the luxuriant Nothofagus forest of the limestone gives place on the magnesian soil almost without any transition to scrub, fell-field and tall tussock-grassland (Fig. 44). Not only does this soil influence the associations but it changes the life-forms, so that trees beyond its influence are merely shrubs on the belt (the spp. of Nothofagus, Griselinia littoralis). Taking the species of shrub-land and fell-field together, for these associations merge into one another, the following are the most important: Phyllocladus alpinus, Poa sp. (related to P. acicularifolia), Festuca sp. (unnamed), Phormium Colensoi, Astelia Cockaynei var., Thelymitra longifolia, Libertia ixioides var., Exocarpus Bidwillii, Nothofagus fusca, N. cliffortioides, Muehlenbeckia axillaris, Colobanthus mollis, Claytonia australasica, Notothlaspi australis, Pittosporum divaricatum, page 301Hymenanthera alpina, Pimelea Suteri, Leptospermum scoparium, Anisotome aromatica, A. filifolia, Griselinia littoralis, Dracophyllum pronum, Cyathodes acerosa, Suttonia divaricata, Myosotis Monroi, Hebe buxifolia, Coprosma proplnqua, C. foetidissima,× C. prorobusta, Helichrysum bellidioides, Cassinia albida var. serpentina and Olearia serpentina.
γ. Fell-field of the wet mountains.
This series of associations is distinguished from that of the dry mountains by the presence of plants of a more mesophytic character and by the absence, usually, of the most intense xerophytes.
The species number about 167 (families 30, genera 71); the commoner species are mentioned below. The life-forms are as follows: — shrubs 24, semi-woody plants 34, herbs 77, grass-like plants 28, rush-like plants 1, ferns 3.
The community, in large part, is a thinning out of the species of herb-field and tussock-grassland, together with the addition of certain plants usually rupestral and a few rare except in this class of fell-field.
The Tararua Mountains near the summits of their highest peaks on stony ground bear a fell-field association, consisting principally of the following: — Danthonia Raoulii var. flavescens, Ranunculus insignis, Anisotome dissecta, Hebe Astoni (cupressoid), green cushions of Phyllachne Colensoi, Celmisia hieracifolia (Fig. 83), C. oblonga, Raoulia grandiflora (Fig. 84) and Leucogenes Leontopodium (Fig. 63).
On Mount Egmont, with increase of altitude, the herb-field becomes more open until on scoria slopes plants are merely dotted about or far distant, the most important being Poa Colensoi, Luzula Colensoi, Epilobium glabellum var. erubescens, Claytonia australasica and Anisotome aromatica.
South Island wet mountain fell-field is virtually restricted to the North-western, Western, South Otago and Fiord districts. The vegetation is richer than that of dry mountain fell-field and the species far more striking. Thus the following Ranunculi are particularly, noteworthy: — R. insignis (NW.), R. Monroi (NW. but also on certain dry mountains), R. sericophyllus (W.) growing amongst large blocks of stone accompanied by the summer-green fern Polystichum cystostegia, R. Simpsonii (F.), R. Buchanani (SO., F.) and the hybrid swarm between the last two, R. Godleyanus (W. — Rakaia Basin to Mount Cook area), R. Grahami (W., Mountain Cook area), R. pachyrhizus (SO., F.). Generally the above are much dwarfed as compared with their herb-field form. The following also are characteristic: — Mar-sippospermum gracile (stiff, rush-like tussock, 20 cm. high), Microlaena Colensoi, Danthonia crassiuscula (small tussock with stiff somewhat horizontal leaves), Poa Cockayniana (large, thick mats), Uncinia macrolepis, U. fuscovaginata, vars. of Acaena Sanguisorbae and hybrids between them, Coriaria angustissima, C. lurida and hybrids between the two, Viola Cunninghamii, Carmichaelia grandiflora (in a wide sense), Epilobium glabellum, E. rubro-page 302marginatum (NW., W.), E. tasmanicum (in a wide sense), Aciphylla divisa, A. similis, A. crenulata (W.), Dracophyllum Kirkii, Suttonia nummularia, Hebe macrantha, Veronica Lyallii, Ourisia sessiliflora, Phyllachne Colensoi, P. clavigera, Celmisia sessiliflora, C. laricifolia, C. Du Rietzii, C. brevifolia, C. Bonplandii, Leucogenes grandiceps, Cotula pyrethrifolia, Raoulia Hectori (SO., south of W. on east), Senecio scorzoneroides and S. revolutus (SO., F.) forming wide mats.
The community occurs both in the subalpine and alpine belts. The substratum is too stony to allow the species to grow at all closely e. g. shingle-slip of large stones fairly stable, which forms a broad path from the alpine stony ground to river-bed (Fig. 87) or glacier; firm talus below cliffs; old river-bed at the head of rivers from glaciers; stony ground in the alpine-belt. Evidently the subalpine area must be the richest in species and the vegetation merges into tall tussock-grassland and herb-field. Various mat-forming species of Celmisia are frequently physiognomic. In the Western district, Leucogenes grandiceps may form great silvery mats on debris near the base of alpine cliffs.
In the Fiord district silvery mats of Celmisia Hectori may dominate, accompanied by abundance of the glaucous, cut-leaved Ranunculus Buchanani, the pale-lemon flowered R. Simpsonii and their many hybrids. An allied association on Rough Peaks (west of SO.) is thus vividly described by G. Simpson and J. S. Thomson (1926:375). "At about 5000 ft. altitude large flat stones almost completely cover the ground, and there Celmisia Hectori formed an almost pure association, the plants growing in between and over the stones, so that for many acres nothing is to be seen except C. Hectori and the protruding stones, with occasional plants of Abrotanella inconspicua, Celmisia Haastii, Marsippospermum gracile, Phyllachne Colensoi and Senecio revolutus. A few plants of Aciphylla similis and A. Spedeni were also present, but very few. This association is most striking: the great sheets of glistening silvery leaves of the Celmisia framing the grey flat rocks and shining in the sun made a sight never to be forgotten."
In the North-western district there is a remarkable montane plant-association which occurs on the plateau extending from near the coal-mining township of Denniston and rising gradually to the slope of Mount Rochfort, its lowest level being about 600 m. Owing to the plateau being exposed to the full face of the westerly wind from the Tasman Sea, it is without forest notwithstanding a very high rainfall. The substratum is flat, rocky or paved with small stones or, in places sandy or clayey and sticky; rocks of various sizes stand out here and there. The plants are all flattened closely to the ground: they root in the chinks between the stones; there is far more bare ground than vegetation. Where large rocks supply shelter, shrubs prostrate in the open grow more or less erect and even Nothofagus page 303cliffortioides is present i. e. but for the wind there would be forest. The following, nearly all high-mountain plants, are the principal species: — Leptospermum scoparium (dominant), Dacrydium Bidwillii, D. laxifolium, Danthonia Raoulii var. rubra?, D. australis (a species of the alpine belt), Carpha alpina, Hypolaena lateriflora, Pimelea Gnidia or an unnamed species, a species of Dracophyllum allied to D. uniflorum, Cyathodes empetrifolia, Gentiana Town-soni, Donatia novae-zelandiae, Celmisia dubia and Senecio bellidioides.
Grassland is that great group of associations — the largest of the high mountains — in which grasses dominate but where, at times, herbs play an almost equal part. The group falls into the distinct ecological classes of tussock-grassland and mat-grassland — this quite limited in extent —, and the former naturally divided into tall and low, as already defined for the lowlands.
It is not feasible to supply definite figures regarding the floristic composition of grassland since, as will be seen, it is a matter of opinion whether to include tall tussock-herb field in herb-field or in the group under consideration. Therefore, I am giving a rather low estimate which omits those species belonging mainly to associations grasslike in physiognomy but herb-field in content.
The number of species admitted here is 249 which belong to 39 families and 104 genera, the largest being as follows: — (families) Gramineae 56 species, Compositae 43; (genera) Danthonia 14, Celmisia 12, Poa 11, Acaena 10, Ranunculus 9 and Carex and Epilobium 8 each — 4 hybrid swarms are included, but many are omitted, and rather more than half the species belong also to fell-field. The most common species are cited when dealing with the communities.
Grassland, though abundant on all mountains, is most in evidence where forest is wanting. At the present time, its area is much smaller than in primitive New Zealand, since burning and grazing have eradicated the grasses and left behind the non-inflammable and unpalatable species most of which belong to fell-field, the latter, as an indigenous-induced community having replaced the grassland. Where forest is absent, high-mountain grassland is merely a continuation upwards of that of the lowland-lower montane belt, the main difference in the former being the dropping-out of a few lowland species and the gradual, or sometimes sudden, incoming of true high-mountain plants. Grassland requires a more "fertile" soil than fell-field and attains its greatest development on a clay substratum with more or less humus on the surface; indeed, the tussocks themselves gradually supply the latter.
The amount of rain required is different for different classes of grass-page 304land but, the higher the rainfall the larger the herb-field content. The ordinary high winds of the mountains and extreme insolation are not antagonistic, but snow lying to a great depth and for a long period is more or less harmful.
The life-history of grassland has been discussed when dealing with lowland-lower montane grassland. In the upper subalpine and alpine belts grassland appears to be a succession following fell-field dependant on increase in the average stability of the substratum. Once tussocks are established, their humus-making power comes into play and species other than those tolerating fell-field conditions can gain a footing. On the other hand, the tussocks themselves will increase in quantity and eventually make the entrance of further species difficult, the tussock-form being a dominant climax-form just as is the tree-form in forest. Nor are these two forms, so distinct in themselves, as ecologically different as one might think since both are strongly hostile to light-demanding species.
β. Low tussock-grassland.
This is a group of associations distinguished by the complete dominance of small tussock grasses ± 30 cm. high, together with a number of herbs and semi-woody plants and a few shrubs and ferns. There are several distinct groups of associations dependant upon the dominant tussock-grass.
The number of species &c. of low tussock-grassland is about 215 which is not far from the estimate for grassland in general, but it must be remembered that in that estimate many herb-field species were excluded.
The Festuca novae-zelandiae group of associations.
This group, or possibly association, is distinguished by the dominance (usually) of Festuca novae-zelandiae and the presence — but not always — of Poa caespitosa, frequently in very limited amount, though occasionally dominant under special circumstances. This class of vegetation up to ± 600 m. altitude has been already dealt with.
High-mountain low tussock-grassland occurs to a limited extent in North Island on the Volcanic Plateau at an altitude ranging round 900 m., but, in South Island, it is abundant throughout on mountains where forest is absent and ascends upwards to 1200 m. or considerably higher. At the highest altitude it occupies sunny positions, those more shaded being clothed with tall tussock-grassland. At there is little, if any, of the community that is not more or less modified, the chief change being great reduction both in size and number of the tussocks, so that their ecological influence is lessened as well as there being far more open ground. In primitive New Zealand the tussocks would touch one another, much light being cut off from the ground and the light-demanding members of the association page 305a considerable majority — be wanting or present only in small quantity1 .
Coming now2 to the general structure and composition of the community, as the high-mountain plants enter in, the facies changes to some extent. Specially important in this regard is the abundance of yucca-like Aciphylla Colensoi with its yellowish, erect bayonet-like leaves, 40 cm. high, now dotted here and there, but in the primitive grassland forming dense thickets impassible to even horsemen. The low, green circular cushions of Celmisia spectabilis, 90 cm. diam. and the mats of C. novae-zealandiae or its allies also lend a distinct aspect to the plant-covering. Most of the species enumerated for the lowland lower-montane belt are present and, in addition, the following may be cited: — Blechnum penna marina, Hypolepis Millefolium (where stony), Lycopodium fastigiatum, Ophioglossum coriaceum, Koeleria novo-zelandica, Danthonia Buchanani (E., NO., SO., F.), Poa Kirkii, P. Lindsayi, Uncinia rubra, Phormium Colensoi (moist or shaded places), Chrysobactron Hookeri vars., Muehlenbeckia axillaris, Stellaria gracilenta, Ranunculus Monroi var. dentatus, Acaena inermis, A. microphylla and their hybrids, Viola Cunninghamii, Drapetes Dieffenbachii, Epilobium elegans, Hydrocotyle novae-zelandiae, Anisotome aromatica, Gaultheria depressa, Pernettya nana, Dracophyllum uniflorum (dotted here and there and rising above the tussock), Cyathodes Colensoi, Gentiana corymbifera (abundant in many places and very handsome with its numerous large white flowers raised on a stout peduncle 30 cm. high), Myosotis australis (flowers yellow), Hebe pimelioides var. minor (stony ground, flowers blue), Coprosma Petriei (forming a continuous turf several sq. metres in area), Celmisia novae-zelandiae or its allies, Helichrysum bellidioides, Raoulia glabra, R. subsericea, Cassinia Vauvilliersii, C. fulvida var. montana, C. albida (SN., NE.), the hybrids between the last three (these shrubs in patches or dotted about) and Taraxacum magellanicum.
Poa Colensoi or P. intermedia (blue-tussock) grassland.
1 1) Experiments and observations have clearly shown that the number of species increases when the tussock is burnt and heavy grazing permitted, and that the species decrease when stock is excluded and burning no longer practised. The great masses of dead leaves which surround mature, unburnt tussocks are also hostile to the presence of other species. Further, various turf-making species — e. g. Raoulia subsericea, Coprosma Petriei — greatly extend their areas of occupation.
2 2) What is said regarding the ecological conditions of low tussock-grassland in the lowland-montane belt applies here also, so nothing is said here on this head.
Danthonia setifolia grassland.
How wide-spread this class of grassland may be I do not know, nor whether it is primitive or induced. On Horseshoe Hill (comparatively wet part of NE.) at an altitude of 1200 m. Danthonia setifolia is dominant; amongst other common species present are: some Danthonia Raoulii var. flavescens, Pimelea pseudo-Lyallii, Drapetes Dieffenbachii, Dracophyllum uniflorum, Coprosma ramulosa and Cassinia albida.
γ. Tall tussock-grassland.
Tall tussock-grassland is distinguished by the strong dominance of one or more of the varieties — several unnamed — of Danthonia Raoulii, together with a more or less large content — in one class very large — of shrubs, semi-woody plants and herbs.
As tall tussock-grassland grades, on the one hand, into low tussock-grassland and fell-field — yet still with one or other tall tussock dominant — and as, on the other hand, if strong dominance of a life-form counts, the transition to herb-field — rich in species of that formation — must be included, it becomes evident that tall tussock-grassland must contain pretty well all the species belonging to the three communities. Any statistics then regarding the species as a whole would be superfluous and misleading.
Tall tussock-grassland is common in both islands and there is a hint of its presence in Stewart Island. At the present time it is most common in the subalpine belts, but originally in the drier mountains it descended to the montane belt, nor can it really be separated from lowland tall tussock-grassland, except for convenience. Burning, however, quickly spells the death of the large tussocks and the smaller tussocks take their place, such replacement making a community not to be distinguished from one that is virgin, except by its history.
1 1) At Cass (E.) adjacent to the Biologic Station burning has led to the dominance of Poa Colensoi. H. H. Allan (1926:81) describes as indigenous-induced a P. Colensoi association for Mount Peel (E.) caused by burning the Celmisia Lyallii fell-field of 1500 m. altitude, the Celmisia not being able to regenerate after burning, but the Poa regenerating quite well. On the other hand, Celmisia spectabilis — well able to tolerate burning — becomes more plentiful.
The community falls into two distinct classes dominated respectively by Danthonia Raoulii var. rubra or var. flavescens or its close allies. D. crassiuscula, a smaller tussock than the above, may also be dominant, hut its presence usually denotes herb-field rather than tussock-grassland.
Red tussock (Danthonia Raoulii var. rubra) grassland.
This is distinguished by the dominance of Danthonia Raoulii var. rubra. It occurs in bot North and South Island. The lowland associations of South Otago and Stewart Island really come here.
The association of the Volcanic Plateau is no longer virgin, wild horses and cattle having grazed on it for many years and more recently rabbits having become common, nevertheless, the facies is still primitive. The association covers much of the pumice-scoria soil on the Volcanic Plateau at an altitude of from 900 to 1200 m. The tussocks some 75 cm. high usually a metre or more apart, but in places they touch. Celmisia longifolia (silvery in colour) is abundant. Erect, dark-coloured, fastigiate bushes of Dracophyllum subulatum, 45 cm. high, affect the general physiognomy. The following also play a notable part: — Lycopodium fastigiatum, Hierochloe redolens, Danthonia setifolia, Poa anceps, P. caespitosa (probably distinct from the common South Island variety), Gaultheria depressa, G. perplexa, many Gaultheria hybrids, Leucopogon Fraseri, Cyathodes Colensoi, Pentachondra pumila (bluish-green patches), circular mats of Coprosma depressa, the beautiful Euphrasia tricolor, low cushions 90 cm. diam. of Celmisia spectabilis and rooting, flat glaucous mats of Celmisia glandulosa var. vera.
In South Island red-tussock grassland apparently denotes a colder or wetter situation than low tussock-grassland. It appears to be essentially a community of the montane or, at most, the lower subalpine belt. In the South Otago district it may be continuous with the tall grassland of the lowland and montane belts but further north it rarely descends much below 900 m. altitude. Sphagnum bog is readily occupied by red-tussock and so converted into grassland. In South Otago, Herpolirion novae-zelandiae and Oreostylidium subulatum are abundant.
Snowgrass (Danthonia Raoulii var. flavescens) grassland.
1 1) To accurately ascertain the status of the many forms of D. Raoulii var. flavescens will be a matter of considerable difficulty involving much close study both in the field and the garden. In the first place, comes in the question of epharmony. For instance, is the form of the Mineral Belt an epharmone or a jordanon? A plant I have had for many years in cultivation supports the belief that it is a jordanon, but this only genetic experiment can solve. And this case is one of comparative simplicity. Frequently one or more of the jordanons of var. flavescens grow side by side with var. rubra and, in such cases, there is a swarm of hybrids. Possibly, too, D. Cunninghamii is involved in such hybridity. Moreover, jordanons of D. flavescens may be ecologically different, especially in the degree of rolling of the leaf; i. e., the associations cannot all be similar in their ecological demands. Cases of this kind occur again and again in the New Zealand flora, and probably in all floras, and, in no few examples it is hopeless to really understand the ecology of a community until the taxonomic status of its members is understood — a matter almost invariably neglected by plant ecologists.
Snow-grass associations are extremely common in South Island and appear in their greatest strength on the wet mountains, but much vegetation where D. Raoulii var. flavescens is abundant must be referred to herb-field. On the dry mountains, and even in the fairly wet South Otago district, much of the community has been wiped out by fire and the large area remaining is usually greatly modified. Originally in South Otago, as may be seen even yet, snowgrass associations descended nearly to sea-level.
On the driest mountains (NO., NE.) the community is not wanting. For instance, on the Inland Kaikouras, there is more or less grassland of this type which is specially distinguished by the presence of numerous, immense, globose, bright-green plants of an unnamed variety of Aciphylla squarrosa together with low cushions of Celmisia spectabilis and some patches of Carmichaelia Monroi.
On Mount Peel (E.), a rather wet mountain, H. H. Allan (1926: 76–79), shows that in the lower part, the community contains much the same species as low tussock-grassland but, on the shaded slopes, it is more or less of a herb-field character.
On the range separating the Ahuriri Valley from Lake Hawea (E.) the snowgrass association commences at about 1200 m. altitude and has almost the same character up to 1540 m., when Celmisia Lyallii puts in an appearance.
In the South Otago district the association of the sunny side of Walter Peak remains purely grassland up to the final rocks, the herb-field element being virtually absent. But, on the shaded side of the mountain, where, from the end of April till the beginning of August, there is no direct sunshine, at less than 900 m. altitude the association contains a good many high-mountain shrubs and herbs. On the Hector Mountains the snowgrass belt begins at about 1100 m. altitude. In many places the tussock is extremely dense. Aciphylla Colensoi is abundant; there is a good deal of Chrysobactron Hookeri. The following species are fairly common: Deyeuxia page 309avenoides, Agrostis Dyeri, Poa intermedia, Festuca novae-zelandiae, Gentiana corymbifera (or an allied species), Wahlenbergia albomarginata, Celmisia coriacea, C. Lyallii and Helichrysum bellidioides. At its upper limit (1320 m.) the Danthonia tussocks become scattered and Poa intermedia becomes dominant while many of the higher-mountain plants put in an appearance.
Mat-grassland as dealt with here includes mat-grassland proper where the grass extends in a. continuous thick sheet over the ground together with those communities where tussock is absent and the grass either forms a continuous close turf or consists of flat mats or low cushions growing either closely or at some distance apart.
The carpet-grass (Danthonia australis) association.
This remarkable association, together with its subassociations, is distinguished by the dominance of Danthonia australis1 which forms a continuous carpet upon which grow (exist) many fell-field species. It is confined to the alpine belt of the North-western, the wettest part of the North-eastern and the north of the Eastern districts, where it may cover the mountain-side for many square metres, or, where the conditions are unfavourable, make merely small patches.
The mats form a slightly hummocky dense covering to the ground quite slippery when walked on. The closeness of growth is antagonistic to other plants, the most important of which are flat cushions of Celmisia spectabilis, C. viscosa, C. Lyallii and C. discolor according to the locality. Here and there are a few tussocks of Danthonia Raoulii var. flavescens or in some localities D. crassiuscula. Where there is a little open ground a few fell-field species, e. g. Pimelea pseudo-Lyallii, Hebe lycopodioides, Aciphylla Monroi, Celmisia laricifolia &c, may be present, but are not really a part of the association.
Probably the association is a climax succession following fell-field, and the species in part are gradually dying out, Danthonia australis being most aggressive and changing its form and becoming lianoid can kill and replace vigorous shrubs.
Needle-grass (Poa acicularifolia) association.
This is distinguished by the strong dominance of Poa acicularifolia. This grass is much-branching and forms close flat leafy cushions, or patches, 7 to 15 cm. diam. The leaves are 4 to 8 mm. long, involute, curved, rigid, smooth and sharp-pointed.
1 1) D. australis forms dense mats 5 cm. or so thick. Beneath, there is much dead grass. The culms and leaves are flattened to the ground and all point one way. The stem is creeping, slender, much-branched and covered thickly for 10 cm. or more with old leaf-sheats. At this point, quite short roots are put forth, but longer ones, 6 to 7 cm. in length pass off from the base of the leafy stems. The leaves have broad sheaths almost equalling the blades. The latter are stiff, hard, wiry, closely involute, smooth, polished, 2.5 to 5 cm. long, needle-like, and rather sharp-pointed.
So far this grass is known only from the Mount Arthur Plateau (NW.), certain lowland limestone hills in the east of the North-eastern district the Mineral Belt of the Dun Mountain (SN.) and the Trelissick Basin of the Upper Waimakariri (E.), where it occurs between 600 and 900 m. altitude. The following description refers only to the area last mentioned.
The closeness of the grass cushions is in proportion to the stoniness of the ground, the plant itself thriving on consolidated stony debris. Near shingle-slip various species of that association, as described earlier on, are present. In the body of the association many species of low tussock-grass-land occur; Plantago spathulata is very plentiful.
Mountain-twitch (Triodia exigua) association and its allies.
Triodia exigua is a small turf-making grass spreading extensively by means of its long, much-branching rhizomes which form a matted tangle. The leaves are narrow, about 2.5 cm long, filiform, stiff and almost pungent. Where dominant, there is a close, dense sward looking almost as if regularly mown. Certain other quite low-growing plants, mostly with creeping underground stems, grow in this association, e. g. Triodia pumila, T. Thomsoni, Carmi-chaelia nana, C. Enysii, C. uniflora (one or other of the three), Leucopogon Fraseri, Wahlenbergia albomarginata and Gentiana serotina (E.). The association occurs from the North-eastern to the North Otago districts.
Where the ground is particularly stony one or other of the species of Carmichaelia noted above is dominant forming broad patches of short, flat, erect green stems. There may also be present more or less prostrate Discaria toumatou, round mats of reddish-leaved Acaena inermis, the close turf-making semi-woody Coprosma Petriei, Wahlenhergia albomarginata, low, flat, silvery cushions of Raoulia lutescens and probably R. australis. The association occurs throughout the drier mountain valleys of South Island.
In the upper Clutha Valley (NO.) there is an ecologically-similar community with the usually coastal Zoysia pungens dominant, but this is at best a lower montane association.
Poa pusilla in certain parts of the montane and lower subalpine Western district forms a fairly close turf with which may be associated Carmichaelia uniflora, Asperula perpusilla, Mazus repens and Pratia angulata.
Herb-field is distinguished by the abundance of various large herbs — some more or less mesophytic — which may either dominate, or tall tussock grasses or even shrubs be the dominant life-form. The vegetation is generally closed but open herb-field must also be distinguished where the composition is virtually that of closed herb-field.
Though it seems best to treat the community as defined above, it should page 311certainly be divided into the following classes: (1.) Herb-field proper, where herbs and low shrubs dominate and tall tussock, if present, plays a very small part, (2.) shrub herb-field, where tall shrubs are conspicuous, the herbs filling the spaces between; (3.) tall tussock herb-field, where Danthonia Raoulii var. flavescens dominates but the var. rubra may be important and probably D. ovata; and (4.) D. crassiuscula herb-field, where that grass is dominant. To give an account of herb-field on these lines, though most desirable, simplifying, as it would, herb-field ecology, is impossible at the present time, no one having made the necessary studies. All the same these terms are used to some extent.
The number of species for-the whole formation including only 10 hybrid swarms (there are at least 35) is 308, about 68 per cent of which belong also to fell-field. They belong to 35 families and 91 genera of which the following are the largest: — (families) Compositae 68, Gramineae 30, Um-belliferae 29, Scrophulariaceae 27; (genera) Celmisia 43, Aciphylla 15, Ranunculus and Gentiana 13 each, Ourisia 9, Danthonia, Epilobium, Hebe and Euphrasia 8 each and Coprosma and Anisotome 7 each. As so many of the species are cited in what follows, to supply a list of the most common would be superfluous.
Herb-field occurs in North Island on the Dividing Range from the highest peaks of the East Cape mountains southwards (EC., RC.), on Mount Egmont (EW.) and, to a limited extent, on the central volcanoes; and, in South Island, on both sides of the Southern Alps subject to the western downpour together with the mountains of the North-western district, many in the South Otago district, and those of Stewart Island, but there, for the most part, the community is that form I am calling, Herb-moor". The vegetation of snow-patches in fell-field is closely related to herb-field.
The formation, especially herb-field proper, occurs on all the high mountains subject to frequent rain and where the climate is less favourable for disintegration of rock and soil than on the dry mountains but much more favourable for the maikng and accumulation of raw humus or peat. Where fully developed, the members grow closely and there is no bare ground, but there is every transition in this regard from herb-field to fell-field.
As already explained, it is not easy to draw the line between herb-field and tall tussock-grassland, for the two imperceptibly merge one into the other. The degree of steepness of the ground is apparently the main selecting-factor the steeper the slope, so long as humus can accumulate, the more favourable is it for tall grassland while, the more level the ground, the richer the herbaceous content. Thus, herb-field proper attains its richest development on the various passes of the Southern Alps (900 to 1500 m. altitude); on the basin-like beds of corries; on the floors and lower slopes of glacier-cirques and on the more gentle mountain slopes in general. Throughout the greater part of the western Southern Alps the vegetation page 312was until recently absolutely virgin, but it is now modified, in places, by the destructive action of red-deer, chamois, and other introduced mammals.
The special soil-conditon, a surface of peaty humus. has been brought about by the plants themselves. Although frequently sopping wet, cessation from rain for a few days, a quite common occurrence, brings about a striking change for the plants, which is met by their xerophytic "adaptations".
The composition and structure of the associations stand in close relation to the average amount of water in the soil, so that the formation may be divided into wet and dry, the soil conditions being reflected in the composition of the vegetation. Altitude is not really a factor of much moment, for the formation at its most luxuriant development, so far as the size of the herbaceous plants is concerned, occurs at sea-level in the Lord Auckland Islands and herb-moor at the same altitude in Stewart Island. Also, at 300 m. altitude or thereabouts, well developed herb-field is present in some of the narrow valleys of the Fiord district where forest has either been destroyed or never been established owing to the frequent snow avalanches.
Coming now to the life-forms of the 308 species they include 47 shrubs, 147 herbs, 65 semi-woody plants, 40 grass-like, 3 rush-like and 6 ferns. Cushion-plants number 12, summergreen plants 17, herbs &c. grasses and ferns above 15 cm. high 54, plants with very hairy or tomentose leaves 59, and nearly all the shrubs are prostrate though the usual form may be erect. Speaking generally, the formation, especially dry herb-field, is less xerophytic than fell-field, indeed certain characteristic members are mesophytes distinguished by large, glabrous leaves (Ranunculus Lyallii, Ourisia macrocarpa vars. calycina and cordata, Anisotome Haastii). Even species with marked xerophytic structure can develope leaves of considerable size (Celmisia coriacea, 60 X 7 cm. Aciphylla maxima, 2 m. long).
The physiognomy of herb-field is dominated over considerable areas by the extraordinary abundance of various species of Celmisia (Figs. 83, 89, 90), their more or less silvery leaves and, in season, multitudes of white flowers (Fig. 89) being very conspicuous. Then come the great Ranunculi, sometimes covering several hectares at a time, or areas — equally large — may be a glory with the great snowy flowers of Senecio scorzoneroides. Many shrubs add to the variety with beauty of form and numerous blossoms while, ecologically, they provide shade and shelter; in short, the most beautiful herbaceous plants of the New Zealand Region, those of the Subant-arctic province excepted, occur in subalpine herb-field, and, when in full bloom, the highest slopes of the Ruahine-Tararua Mountains, or the virgin passes of the Southern Alps, where alpine and subalpine vegetation mingle, are lovely natural gardens (Figs. 84, 89 and 91).
Dominance in a minor degree is exhibited by the presence in quantity of other plants. Thus, one or other of the large species of Astelia may by page 313abundant (Fig. 91) or giant Aciphyllae the striking feature. Altitude brings in one or more of the cushion-forms of Celmisia, (Fig. 92) and the species as a whole become smaller, while the special grass will be Danthonia crassiuscula. In fact, the large mesophytes are replaced by xerophytes or subxerophytes of the same genera, e. g. Ourisia macrocarpa by 0. sessilifolia. But little can be said here concerning the smaller modifications of the plant-covering, all that is attempted being a quite general account of the communities, laying stress, as far as my knowledge goes, on what seems fundamental.
β. North Island dry herb-field.
Mounts Te Moehau (T.) and Hikurangi (EC.)
Te Moehau (725 m. alt.) is the northern outpost of the true high-mountain plants (Adams, J., 1889: 39–40) where upon the open ground appears to be a small patch of herb-field, containing Danthonia setifolia?, Oreobulus pectinatus, Carpha alpina, Pentachondra pumila, Cyathodes empetrifolia, Ourisia macrophylla and Celmisia incana. No more herb-field vegetation occurs until the summit of Hikurangi (1704 m.) 297 km. distant southwards is reached where some 44 high-mountain species occur, including — of a herb-field character — all the above and the special high-mountain species Ranunculus insignis, Gentiana bellidifolia, Celmisia spectabilis, Raoulia grandiflora and Leucogenes Leontopodium.
The Tararua Mountains.
The striking feature of the association is the enormous quantity of Astelia Cockaynei in clumps 2.5 m. × 1.9 m. or as a continuous covering for many square metres at a time. In many places Danthonia Raoulii vars. rubra and flavescens dominate. The circular clumps of Ranunculus insignis are characteristic, the green leaves contrasting with the equally abundant silvery sheets of Leucogenes Leontopodium (Fig. 63). The following conspicuous plants are abundant: Chrysobactron Hookeri, Aciphylla conspicua, Anisotome dissecta (rather tall with finely-cut leaves), flat circular cushions of Celmisia spectabilis and C. hieracifolia (Fig. 83) and the much smaller C. oblonga. Certain subalpine shrubs appear in the association, e. g. Coprosma pseudo-cuneata, Hebe evenosa but the following belong properly to the community: Gaultheria depressa, Dracophyllum pronum, the cupressoid Hebe Astoni, prostrate or rounded bushes 30 to 60 cm. high of the Daphne-like Pimelea Gnidia (Fig. 89). The following are the more or less important of the smaller grasses and herbs: Poa anceps, Triodia australis (sometimes turf-forming), Ranunculus geraniifolius, Oxalis lactea, Epilobium chloraefolium var. verum, E. Cockaynianum, Veronica diffusa, Ourisia caespitosa and Euphrasia tricolor. The association consists of about 53 species.
1 1) By the settlers the association is ealled the Moss, so that one might think flowering-plants were absent. Certainly large white hummocks — greyish when dry — of Rhacomitrium pruinosum on certain parts of the mountain give a characteristic aspect to the scene. These hummocks are dense, rounded and average about 70 cm. in length to 60 cm. in breadth and 10 to 12 cm. in depth. Frequently, two or more of the cushions, becoming united, form amorphous masses, or they may be separated by the general carpet of herbs. Within a cushion the moss is dead and full of moisture. Usually various herbs grow on them, but eventually such are buried. On some parts of the mountain the cushions are absent, their representative being patches of a yellowish-green moss.
The substratum consists of scoria with a certain amount of humus on the surface. The rainfall is excessive and but for the porous soil the surface would be boggy.
The association consists of a more or less close turf dotted here and there with taller plants either singly or in small groups. The turf consists principally of the following: — Hymenophyllum multifidum, Lycopodium fastigiatum, Danthonia setifolia, Anisotome aromatica, Gaultheria depressa, Coprosma repens, C. ramulosa, Forstera Bidwillii var. densifolia, Celmisia major, C. glandulosa var. latifolia, Raoulia glabra, Helichrysum alpinum and Cotula squalida. Everywhere in January the plant-covering is marked by the beautiful white whorls of flowers of Ourisia macrophylla, 27 cm. or so high rising from the rosettes of pale-green, purple-edged leaves. Ranunculus nivicola, with its large golden blossoms, also gives special stamp to the association. In places, silvery patches of Celmisia major, its narrow leaves recurved, are physiognomic. Other species rising out of the general groundwork are brown bushes of Dracophyllum filifolium (12 cm. high), flat-topped yellowish cushions of Cassinia Vauvilliersii (17 cm. high, 27 cm. diam.) and bright-green Hebe buxifolia.
γ. South Island dry herb-field.
It would be impossible, even were anything approaching exact details available, to set forth in a short general account of South Island dry herb-field proper the relation of this or that dominant or subdominant species to topographical conditions, soil, climate &c. Suffice it to say that in some places shrubs dominate, in other places tussocks dotted about or in small groups are subdominant, in others Phormium Colensoi or again in others species of Celmisia or Ranunculus are physiognomic.
1 1) They fall into the two categories of those with wide leaves which in one class (C, petrocata, C. Traversii &c.) arch downwards at their extremities, and those with narrow stiff leaves (C. Armstrongii, C. Petriei, C. Lyallii).
The giant buttercups lighting up a hillside with their white or yellow blossoms are both of extreme physiognomic importance and beauty. Ranunculus Lyallii (Fig. 91) is the most striking and wide-spread occurring, as it does, from the Spenser Mountains to Stewart Island; it is particularly plentiful in the Western district. The great glossy, green peltate leaves spreading horizontally, raised on stout stalks 30 to 45 cm. high, cut off the light from the ground and forbid other plants to gain a footing, this being also assisted by the broad, half-buried, thick rhizomes paving the substratum. In the North-western district, R. insignis occupies a similar station, and in the Fiord district R. Buchanani makes wide colonies, but usually only at a higher altitude and on more stony ground, a happening in accord with its more xerophytic structure. When growing in company with R. Lyallii great variety is lent to the community by the polymorphic hybrid swarm between the two, one individual of which has been described as a species under the name R. Matthewsii.
Astelia Cockaynei and A. Petriei are common in many places. The latter with its shorter, more rigid, glossy leaf ascends to the alpine belt and completely fills snow-patch hollows; the smaller A. monticola (W., F.) behaves similarly.
1 1) C. Traversii with rusty tomentum and leaf margined with same is characteristic of the northern part of the Southern Alps and neighbouring mountains; it occurs also in the Fiord district. C. Armstrongii, its leaves stiff, sword-like and with a conspicuous orange midrib is the plant par excellence of the Westland side of the Southern Alps. C. verbascifolia, C. holosericea and C. Petriei are characteristic of the Fiord district, the latter has dagger-like leaves, green and glossy above, satiny-tomentose beneath and the margins much recurved. C. lanceolata, intermediate between C. coriacea and C. Armstrongii is common in the southern half of the Fiord district.
2 2) To J. A. McPherson (Director of Parks and Reserves, Invercargill) I am greatly indebted for particulars regarding the herb-field proper of Mount Glasgow (1400 m. — coastal range of NW.) — hitherto undescribed. As about 1100 m. altitude the subalpineforest gives out and is fringed by an extremely narrow belt of Olearia Colensoi and Phormium Colensoi passing through which the herb-field at once commences. This association is distinguished by the extreme abundance of Celmisia Dallii accompanied by large quantities of C, Armstrongii and Anisotome Haastii and various species of Hebe are dotted about, e. g. H. vernicosa, H. buxifolia and their hybrids. There are many forms of Senecio Bidwillii including some with toothed leaves (perhaps hybrids with Olearia arborescens). Other species of moment are Aciphylla Hookeri, A. polita, Gentiana montana, Ourisia macrophylla, Hebe macrantha and a cross or crosses with H. buxifolia and Celmisia incana.
Certain subalpine shrubs invade the associations especially: — Phyllo-cladus alpinus, Hebe subalpina, Coprosma pseudocuneata, C. ramulosa, C. crenulata, C. serrulata (spreading widely by means of underground stems), Gaultheria depressa, G. rupestris, Pentachondra pumila and Carmichaelia grandiflora.
The following — equally important — are of restricted distribution: — Dracophyllum Menziesii (F.), Hebe vernicosa in various forms (SN., NW., north of NE.), Coprosma depressa (NW., north of W. — but records untrustworthy) and Senecio revulutus (SO., F.).
The general carpet of the community is a striking feature where the taller plants are not greatly in evidence or it may merely fill intermediate spaces between them. The following are more or less common throughout: — Hymenophyllum multifidum, Blechnum penna marina, Lycopodium fastigiatum, Hierochloe Fraseri, Agrostis Dyeri, Deyeuxia pilosa, Deschampsia Chapmani, Trisetum antarcticum, Danthonia setifolia, Poa pusilla, P. caes-pitosa, P. Cockayniana, P. Colensoi, Festuca one or more unnamed species, Uncinia compacta, U. fusco-vaginata, Carex dissita var. monticola, Astelia linearis, Ranunculus foliosus, Caltha novae-zelandiae, Geum parviflorum, G. uniflorum, Acaena Sanguisorbae vars., Geranium microphyllum, Coriaria lurida, C. angustissima, Viola Cunninghamii, Epilobium chlorae folium var. verum, Aciphylla similis, Anisotome aromatica, Angelica decipiens, Euphrasia revoluta, E. zelandica and other species according to locality, Plantago Brownii, Wahlenbergia albomarginata, Phyllachne Colensoi, P. clavigera, Forstera sedifolia, F. Bidwillii, Gnaphalium Traversii, Helichrysum belli-dioides, Craspedia various allied species, Cotula pyrethrifolia, Senecio belli-dioides, S. Lyallii and Taraxacum magellanicwn.
δ. Tall tussock-herb field.
The North Island communities.
Most likely there is herb-field of this character on all the high mountains, but its nature on Mount Egmont is beyond dispute. Danthonia Raoulii var. rubra is dominant and between the tussocks there is a close turf made up of all the neighbouring herb-field species, as already described. The association occupies the slopes, whereas herb-field proper is confined to the gullies, the controlling factor as to which kind of herb-field shall occupy the ground being the length of time this is covered by the winter snow, the tall tussock-herb-field being far longer free from snow.
The South Island communities.
In South Island the communities are dominated by Danthonia Raoulii var. flavescens, or it may be D. crassiu-scula or perhaps D. ovata (F.). Most, if not all the herb-field proper species of the particular locality will be represented. Seen from a distance the community resembles tall tussock-grassland proper, but a close view reveals the large herbaceous plants (Ranunculus, Celmisia) and various shrubs. Though the group of associations stands intermediate between herb-field proper and tall tussock-grassland it is no mere tension-belt (ecotone), for it occupies wide areas where herb-field proper may be absent.
Tall tussock-herb field occurs principally in those South Island mountains exposed to an excessive rainfall. A familiar instance is the community near Mount Cook (east of W.) which may be the sole representative of herb-field from the scrub-line to the alpine fell-field. As for its ecological distribution I have not nearly sufficient data, but suggest it may require a gentler slope and rather moister soil than tall tussock-grassland proper. The presence of the herbaceous, semi-woody and shrubby members depends upon open spaces between the tussocks, but, those shade-tolerating as young plants, are the most likely to become established. The tall rosettes of various species of Celmisia (C. Lyallii and the great C. Petriei themselves tussocks), the shade-casting leaves of Ranunculus Lyallii and its massive rhizomes covering the ground, and the dense habit of certain shrubs, enable all such to bid defiance to the tussocks which, nevertheless, remain dominant.
As for the history of the community it may be a succession following herb-field proper and the herbaceous-shrubby element be the remains of the original association. On the other hand, tall tussocks and the herb-field element may have developed side by side as they increased the humus content of a preceding fell-field association, or, in places, the community may replace bog by way of wet herb-field. In any case, no matter its origin, at the present time tall tussock-herb field is apparently a climatic climax-community, as in the hanging valley near Lake Harris (F.).
There is no need to give details regarding the species making this class of herb-field, for all those of herb-field proper are concerned. In the alpine belt, however, the dominant grass is Danthonia crassiuscula, which page 318is much smaller than D. Raoulii var. flavescens, and which may take on to some extent a mat-grass habit and so be somewhat hostile to other species. In this group of associations the alpine herb-field species are strongly represented.
ε. South Island wet herb-field.
This group of associations is usually distinguished by the dominance of the summergreen Senecio scorzoneroides, together with abundance of Schoenus pauciflorus, and Hebe buxifolia var. pauciramosa (a compound var.) is characteristic.
The presence of wet herb-field depends upon a more badly-drained substratum than that of dry herb-field and a more peaty soil. Frequently, streams carry away more or less of the surplus water so that the soil — though always wet — is not so "sour" as that of herb-moor. The flat ground of subalpine passes and the most depressed parts of corries and hanging vallies are the special site of wet herb-field.
In some localities, the Senecio, when in full bloom, renders extensive areas white as a snow-field or, if the yellow S. Lyallii is present the many hybrids will add flecks of yellow, pale-yellow and cream. Where there is no stagnation Ranunculus Lyallii and many dry herb-field species may be present, including the species of Astelia. The following may receive special mention: — Dacrydium laxifolium, Hierochloe redolens, H. Fraseri, Deyeuxia pilosa, Danthonia crassiuscula, Carex ternaria, Chrysobactron Hookeri, Ranunculus foliosus, Geranium microphyllum, Viola Cunninghamii, Epilobium chloraefolium var. verum, Aciphylla Lyallii, Oreomyrrhis andicola in a wide sense, Dracophyllum prostratum, Gaultheria depressa, various species of Gentiana, various species of Euphrasia, Ourisia macrocarpa vars. calycina and cordata, 0. caespitosa, Coprosma repens, Donatia novae-zelandiae (Fig. 92), Celmisia petiolata, C. verbascifolia, C. glandulosa var. vera, Craspedia uni-flora in a wide sense, Helichrysum bellidioides, Microseris Forsteri and Taraxacum magellanicum.
Herb-moor is here considered as a formation intermediate in character between wet herb-field and bog, which is distinguished by the absence of tall plants and the abundance of turf-forming, prostrate and cushion species.
The species number about 141 which belong to 31 families and 20 genera, the largest being: (families) Gramineae and Cyperaceae 14 species each, Scrophulariaceae 12, Umbelliferae 11; (genera) Celmisia 11, Carex 8 and Raoulia 6.
The following are characteristic South Island species: — Carpha alpina, Oreobolus pectinatus, 0. strictus, Astelia linearis, Hectorella caespitosa, page 319Ranunculus Berggreni, certain small Aciphyllae, Anisotome imbricata, A. lanuginosa, Dracophyllum muscoides, Myosotis pulvinaris, Hebe dasyphylla, Ourisia glandulosa, Plantago lanigera, Coprosma repens, Phyllachne clavigera, P. rubra, Donatia novae-zelandiae, Celmisia ramulosa, C. brevifolia, C. sessili-flora, C. argentea and the hybrids between the last two, Raoulia Hectori and Cotula serlcea.
Herb-moor is confined to the flat-topped mountains of the South Otago District, the Dunstan Mountains (NO.) and Stewart Island. The association called by me winter-bog (1908: 30) of the Volcanic Plateau is similar in various ways, and small areas of wet herb-field in the high mountains generally come into the ecological conception of the formation.
Herb-moor attains its full development on badly-drained, peaty ground exposed to a subantarctic climate. Thus, the long, narrow, plateau-like summits of those South Otago mountains at over 1800 m. altitude, lying within the full influence of the south-west wind, and where the winter snow lies until November or even the end of December, are ideal. Deep, wet peat; frequent driving rain or snow; violent gales; cloudy skies but, at times strong insolation, are the leading ecological factors. The base of the plants being clothed with a wet, sticky, peaty covering reaches about its maximum development. Evidently, the formation is closely related to bog., but certain bog species, including Sphagnum, are wanting and the substratum, though wet enough, in no part lies under water unless for a brief period.
The life-forms of the community are as follows: — shrubs 17 species, herbs 67, semi-woody plants 23, grass-like plants 30, rush-like plants 2, ferns 2. Cushion-plants number 30, but many other species at times assume this form and there are 48 mat-plants and, again others epharmonically become mats.
South Island herb-moor.
On the narrow summit-plateau of the Old Man Range (SO.), Herb-moor has attained its richest development. The winter snow lies well on into the summer and in shady places may not melt. The plateau is frequently swept by the full fury of a south-west gale, rain-bringing or snow-bringing, but always piercingly cold. The peaty surface of the ground is cut into hummocks separated by basin-like depressions about 38 cm. deep and 60 cm. across which are united into a more or less connected trench, so that the plateau is traversed by parallel trenches. The hummocks are rounded, about 90 cm. across, and usually densely covered with vegetation which extends, though different in composition, into the basins.
The following species, all of low stature, are common on the hummocks: — Hierochloe Fraseri, Agrostis subulata, Poa Colensoi (greatly dwarfed), Ranunculus novae-zelandiae, Drapetes Lyallii, Anisotome lanuginosa, Dracophyllum muscoides, Hebe Hectori (cupressoid), H. dasyphylla, Phyllachne Colensoi, P. rubra, Celmisia argentea, C. brevifolia, C. viscosa, Craspedia uniflora in a wide sense, Raoulia grandiflora, R. Hectori and Senecio belli-dioides (glabrous form).page 320
In the basins the small rosettes of Ranunculus Berggreni are abundant; in shallow hollows where snow lies long are wide breadths of Celmisia viscosa and C. Haastii, as on South Island mountains in general. Where the wind attains its maximum velocity all vegetation may be destroyed except the rigid low, dense cushions of Dracophyllum muscoides. Natural monoliths of micaschist stand up here and there — one the "Old Man" from which the range gets its name — and on the debris near them there are many silvery cushions of Raoulia Hectori, also small cushions of Myosotis pulvinaris and dense Dracophyllum muscoides.
On Mount Pisa Plateau (1500 to 2100 m. alt.) much the same community as just described is present, except, that over wide areas the prostrate reddish-brown branches of a species of Dracophyllum (possibly prostrate epharmonic D. uniflorum) are physiognomie Much of the ground is covered with pebbles of quartz; also, it is traversed by streams and much better drained than the Old Man Range.
The Rock and Pillar Range (1430 m. alt., SO.) has much the same association as described above, but the species are rather fewer, and in full strength occur on consolidated flattish stony debris. Maungatica (SO., 900 m. alt.) likewise carries herb-moor but with fewer species. Celmisia coriacea var. stricta, C. argentea and Dracophyllum prostratum are common.
Stewart Island herb-moor.
This association is distinguished by the abundance of Danthonia pungens, Dracophyllum rosmarinifolium (its mat and turf forms), Astelia linearis, Carpha alpina and Microlaena Thomsoni, and is made up of two subassociations — the one confined to granite and the other to mica - schist, but the relative steepness of the slope may be an important factor.
Various species of the lowland belt, though eminently suitable, are absent, e. g. Blechnum penna marina, Gleichenia alpina, Schizaea fistulosa var. australis (probably an epharmone), Dacrydium laxifolium, Danthonia Raoulii var. rubra, Gaultheria perplexa, Ourisia Crosbyi and O. modesta. Further, the following are wanting in South Island herb-moor: Lycopodium ramulosum, Microlaena Thomsoni, Danthonia pungens, Chrysobactron Gibbsii, Aciphylla Traillii, Dracophyllum rosmarinifolium (but in herb-field, F.), D. Pearsonii, Gentiana lineata, Hebe Laingii and Raoulia Goyeni.
As for the subassociations on the granite (Mount Anglem), the following are wanting: Euphrasia Dyeri, the so-called Celmisia linearis (most likely C. argentea × longifolia) and Senecio scorzoneroides and Celmisia argentea is rare, and the following are restricted thereto: Schoenus pauciflorus, Uncinia compacta var. caespiciformis, Hebe Laingii, Ourisia prorepens, 0. sessilifolia and a mat - Celmisia of the C. discolor group (originally referred to C. Sinclairii).
Seen from a distance, the association presents a most even and smooth surface, but when walking on it, one soon perceives it to consist of a dense page 321mass of plants, springy to the tread, into which the feet sink but which rise back into their former position. There is a ground-work of the dominant species, others entering in according to changes in water-content, and perhaps becoming dominant. The above ground-work consists of pale-green grasslike tufts of Carpha alpina, the leaf apices straw-coloured dead and twisted; close low cushions of Donatia novae-zelandiae, the green leaves with bright orange tips pressed together into small rosettes; Dracophyllum rosmarini-folium much like Donatia but the leaves more open and tipped with red; green cushions of Oreobolus pectinatus and growing through and mixed with the whole almost everywhere Astelia linearis and the small, flat, glaucous leaves of the grass. Microlaena Thomsoni. Although the covering is made up so largely of cushions, that form is masked through their growing into one another. At less than one metre apart, everywhere project obliquely above the general mass tufts of the rigid, sharp-pointed pale-green or reddish-brown leaves of the ungrass-like grass Danthonia pungens. On the schist mountains, where the soil becomes drier, the general carpet is everywhere dotted with the silvery, dense cushions of Celmisia argentea (Fig. 90) and those more open, and greenish-tinged of C. linearis (its status already explained), which, growing together form conspicuous, silvery cushions.
Stewart Island herb-moor is in harmony with that semi-subantarctic climate which permits the establishment of what are really high-mountain communities at sea-level; indeed it commences at less than 600 m. altitude and barely reaches 900 m. at its highest point.
a. Bog, water, and swamp communities.
α. Bog associations.
Bog associations are those in which more or less Sphagnum is nearly always present, together with some of the following species: — Gleichenia alpina, Dacrydium laxifolium, Carpha alpina, Oreobolus pectinatus, Carex Gaudichaudiana, Eypolaena lateriflora, species of Gaimardia, species of Drosera, Halorrhagis micrantha, Liparophyllum Gunnii, Phyllachne Colensoi, Donatia novae-zelandiae, Celmisia glandulosa and Olearia virgata.
The number of species for the high-mountain part of the formation is 138 which belong to 33 families and 77 genera, the largest being Compositae 15 species, Cyperaceae 14 and Epacridaceae 9, but none of the genera exceed 6 species. Those most widely spread appear in what follows.
Bog occurs throughout all the high-mountain area wherever the drainage is insufficient to forbid water lying on the ground for considerable periods. Usually the bogs are small. The habitat is not governed principally by rainfall, for bogs occur both where such is heavy and where it is quite light; in the latter case, the bog-community depends upon the substratum being in close proximity to streams liable to flood or springs and shallow lakes. On the contrary, in an extremely wet climate, bogs may originate page 322on flat ground distant from streams &c., for, m such a climate Sphagnum can become established on steep slopes and other unlikely places.
As to the life-forms of the species, there are 29 shrubs, 11 semi-woody plants, 65 herbs, 23 grass-like plants, 6 rush-like and 4 ferns. Most of the shrubs are prostrate, even if usually erect elsewhere, e. g. Leptospermum scoparium, Olearia virgata; cushion-plants number 11.
A bog-association may be a succession following swamp; primary succession culminating in tussock-grassland, herb-field or shrubland; or even a climax where the water-supply is constant. In some measure the permanency of the bog depends upon the ability of the sphagnum by its upward growth to bury the invading grasses, herbs and shrubs. If these grow faster than the moss the latter is doomed. Thus, small bogs are rapidly transformed into grass, herb and shrub associations, as in the case of one I have known on Jack's Pass (NE.) for some 25 years and noted getting gradually smaller and smaller. A closed community of Celmisia coriacea and Astelia Cockaynei in its vicinity was originally Sphagnum bog.
Various classes of bog.
Schoenus pauciflorus bog is extremely common in the montane-subalpine tussock-grassland area of South Island and it occurs also to some extent on the Volcanic Plateau but as a somewhat different association. The reddish colour of the Schoenus tussocks in contradistinction to the brown grass renders the community conspicuous even from a distance. Although the bog is traversed by running streams, the ground is sopping wet. Sphagnum cushions are usually plentiful and growing on them certain small herbs, e. g. Blechnum penna marina, species of Drosera, Geranium microphyllum, Viola Cunninghamii, Haloorhagis micrantha, Nertera Bal-fouriana and Celmisia longifolia var., Chrysobactron Hookeri var. angustifolia is usually abundant.
Closely related to the above in the North-eastern and Eastern districts are associations where Schoenus is not dominant, Sphagnum abundant and shrubs present e. g. Leptospermum scoparium, Gaultheria depressa, G. rupestris, Dracophyllum uniflorum, Hebe buxifolia and Cassinia Vauvilliersii. Astelia Cockaynei is frequently an important feature. In many places, Carex Gaudichaudiana dominates. More or less Danthonia Raoulii var. rubra is usually present, but rather as an invader from the grassland surrounding the bog than as a true member of the community.
Cushion-bog, so-called from the abundance of that life-form in the associations, is common in the subalpine-belt of many South Island wet mountains. The bog is usually quite small. The special feature is the numerous, small, dense cushions of the following, some of which may be absent: — Oreobolus pectinatus, 0. strictus, Gaimardia ciliata, G. setacea, Phyllachne clavigera, P. Colensoi and Donatia novae-zelandiae. In addition most of the following will be present: — Gleichenia alpina, Dacrydium laxifolium, bushes of D. Bidwillii, Carex Berggreni (SO.), Carpha alpina, Hypolaena page 323lateriflora, Astelia linearis, species of Drosera, prostrate Leptospermum scoparium, Plantago triandra, Pentachondra pumila, Cyathodes empetrifolia, C. pumila, one or more species of Gentiana, Celmisia longifolia var. alpina or other variety and C. glandulosa var. vera. The extensive bog association of the upper Routeburn hanging valley is of this class and, in addition to most of the above are Hebe buxifolia var. paucibrachiata and H. Hectori, Sometimes, especially in open places in subalpine forest, prostrate Dacrydium Bidwillii, is physiognomic and stunted Nothofagus cliffortioides common.
Hypolaena-Gleichenia bog is another type. It greatly resembles the allied bog of the lowland belt. Bog of this character occurs on the Volcanic Plateau, but its presence depends upon abundant ground-water supplied by melting of the winter snow since the drainage is good. Gleichenia alpina is plentiful but the grass-like Carpha alpina with its pale-green leaves, withered and twisted at their extremities, is the special feature. There is abundance of Oreobolus pectinatus, Viola Cunninghamii and Celmisia glandulosa var. vera. In the same district where the conditions are truly boggy the dark-green Liparophyllum Gunnii forms close mats together with a turf of Carpha alpina, Scirpus crassiusculus, S. aucklandicus and Gnaphalium paludosum. Utricularia monanthos is extremely plentiful. Other common plants are Danthonia Raoulii var. rubra, Juncus antarcticus, Carex ternaria, Aciphylla squarrosa, Gentiana bellidifolia, Coprosma repens and Craspedia minor. Better drained, though constantly wet ground, brings Hypolaena and Gleichenia into dominance accompanied by abundance of Hebe buxifolia, and many fell-field shrubs much dwarfed are raised on drier mounds above the general level.
Hypolaena bog on the Rahu Saddle (NW.) is distinguished by the abundance of bushes of Dracophyllum palustre forming patches about 90 cm. long and about 60 cm. high of its slender twiggy, blackish, crowded branches; also Cyathodes empetrifolia is conspicuous and there is some Phormium Colensoi.
β. Water and swamp vegetation.
Here are included associations of running and still water and those of flushes, but excluding those of dripping rocks. The species number only 11 which belong to 8 families and 9 genera.
Where streams flow swiftly Algae and perhaps a moss or two are present, their presence on stones marking the usual depth of the water. In winter many glacial streams, even of considerable size, are quite dry and during the rest of the year the amount of water varies greatly. Montia fontana is characteristic and often fills small, shallow brooks, even floating upon the surface or forming close cushions in shallow, fairly rapid streams (Fig. 93). Epilobium macropus — physiognomic from its large flowers — is common in shallow parts of slow-flowing subalpine brooks and in shallow water of depressions in river-beds, a station likewise of Claytonia australasica. page 324In South Island on margins of montane streams reddish tussocks of Carex Buchanani grow in abundance. On the Volcanic Plateau and in many parts of South Island, Gunnera dentata forms close masses in very shallow water and on the wet ground adjacent, its leaves flattened to the soil excluding other plants. In many South Island shallow streams, there is a close growth of the slender-stemmed Schizeilema nitens distinguished by its small shining, trifoliolate, thin, glabrous leaves. Ranunculus Cheesemanii (NE., north of E.) is frequent in places where water generally lies. R. depressus, in a very wide sense, is common on still water. In fairly rapid brooks there is often a dense growth of Myriophyllum propinquum, the leaves submerged and on the water-surface float the brown leaves of Potamogeton Cheesemanii.
Soil constantly wet through water rising out of the ground is occupied by many species, of which the following are particularly common: — Carex Gaudichaudiana, C. Petriei, Scirpus aucklandicus, Juncus novae-zelandiae, Claytonia australasica, Acaena saccaticupula, Oxalis lactea, Viola Cunning-hamii, Epilobium pedunculare var. brunnescens, Pratia angulata, Plantago triandra, Gnaphalium Mackayi and species of Craspedia.
The associations of lakes and tarns differ but little from those of the lowland belt. The same species of Potamogeton and Myriophyllum are present and the swamp species of the margin are lowland plants, e. g. Heleocharis Cunninghamii, Cladium glomeratum, Carex subdola, C. secta, C. pseudocyperus. Isoetes alpinus and Pilularia novae-zelandiae, submerged aquatics, are probably common.
There is but little swamp of a high-mountain character. Carex virgata or C. secta are frequently dominant and C. ternaria, C. stellulata and C. diandra are extremely common. In the deepest water Typha angustifolia var. Muelleri dominates. On the margin, there is usually a bog community in which Plantago triandra and Isotoma fluviatilis may be plentiful.
Swamp occurs principally in montane valleys of South Island and owes its origin to frequent flooding of the ground by rivers and streams, especially during rapid melting of snow; where the drainage is insufficient, it is readily transformed into bog.