The Vegetation of New Zealand
Chapter I. — Introductory Remarks
It is not feasible to fix any arbitrary line of demarcation between the lowland-lower hills' vegetation and flora and those of the high mountains, since not only is the dividing-line governed by latitude but also by aspect, rainfall and other ecological factors. Thus in the Auckland botanical districts, with the exception of one or two summits of the Thames Mountains, all the hills, even when they considerably exceed 600 m. altitude, bear a vegetation of a lowland stamp and true high-mountain plants are wanting. All the same, certain species ascend far higher than others and there are more or less distinct altitudinal belts. For the rest of North Island, high-mountain species do not generally appear until an altitude of at least 800 m. is reached. In South Island, though from 400 m. to 600 m. may be taken as a fair estimate for the dividing-line (hardly such, but rather a belt where one flora merges into the other), no universal delimiting-line can be fixed. Where, particularly in the west and south, the climate is wet and cloudy days abundant, should the edaphic conditions be favourable, quite a number of species, otherwise typically alpine or subalpine, descend to sea-level even so far north as lat. 42°. In Stewart Island, not species merely, but actual subalpine associations, occur at virtually sea-level. Furthermore, the foot-hills, bases of the high mountains and the valleys of South Island, at an altitude of considerably less than 600 m., frequently possess a vegetation subalpine rather than lowland.
The area under consideration comprises North Island as a whole, excepting the actual coast-line, one or two mountain summits in the Thames subdistrict and those portions of the high mountains above an altitude of 800 m. at the very least. In South Island, the lowland-lower hills' belt is much more restricted, its greater part follows the coast-line, though it passes inland by way of the lower slopes of the mountains and the numerous valleys, so that, in places, there is lowland vegetation almost to the foot of the actual Divide. In Stewart Island, the line of demarcation may be put down at about 450 m., though it is considerably less in the south.
Notwithstanding the extensive plains of both the main islands, much of the land-surface is extremly broken and hilly, while in many places deep gorges are a characteristic feature, and in others wide shingly river-beds, so that there is great diversity of habitats throughout. The summit vegetation of comparatively low hills, if isolated or specially exposed, bears a mountain stamp both in species and physiognomy. A great deal of the page 117lowland vegetation has been not merely modified in the course of settlement but actually wiped from the face of the land. But, except in a few instances, there are sufficient indications to show clearly enough of what the primitive plant-covering consisted, so that it is still possible to give a fairly accurate sketch of primeval lowland New Zealand. Areas, too, remain absolutely in their virgin condition, but such — forest more particularly — are being so rapidly damaged by deer that areas described as still primeval in the first edition of this book are now more or less modified, while associations I saw in their primitive state more than 45 years ago are now ecologically unrecognizable!
Owing to the comparatively mild climate, and the general absence of such intense ecological factors as occur on the coast and the high mountains, the conditions for plant-life are more uniform than in the two latter belts. But the diversity of stations in different parts of the area leads to the presence of many communities and life-forms. Above all, gradual change in latitude and the relation of the vegetation to excessive rain in many parts, or to long periods of drought in others, are fundamental factors in regard to the distribution of species, and the composition, structure, and peculiarities of the communities. It is these extreme conditions which bring down to the lowlands many true high-mountain species, but this is discussed at some length in Section III, Chapter I.
The lowland-lower hills' flora consists of 1059 species and is made up of the following elements to each of which is appended its number of species: — 1. Species confined to the lowland-lower hills' belt, hereafter termed lowland 559; 2. species found both in the lowlands and high mountains 339; 3. species truly high-mountain which occasionally occur in the lowlands 115; 4. coastal species which either extend inland for some distance or occur far from the sea, but only under special circumstances 46. Leaving out of consideration the coastal and purely high-mountain elements the number of species in the lowland flora proper is 898. In addition there are at least 72 groups — many of them large swarms — of wild hybrids.
Considering first the 559 purely lowland species they consist of 103 pteridophytes (Filices 91), 10 gymnosperms, 148 monocotyledons and 298 dicotyledons which belong to 88 families and 231 genera, and 380 species (68°/o) are endemic.
The following 24 families and 103 genera are confined, or almost so, to the lowlands and lower hills, those marked* being endemic: — (families) Salviniaceae, Psilotaceae, Araucariaceae, Pandanaceae, Sparganiaceae, Palmae, Lemnaceae, Burmanniaceae, Amaryllidaceae, Moraceae (also coastal), Piperaceae (also coastal), Lauraceae, Monimiaceae, Rutaceae, Meliaceae, Icacinaceae, Sapindaceae (also coastal), Elatinaceae, Passifloraceae, Tetrachondraceae, Verbenaceae (also coastal), Solanaceae, Gesneriaceae and Capri-page 118foliaceae (ascends occassionally to the lower subalpine forest); (genera) Loxsoma*, Cyathea, Hemitelia, Leptolepia*, Lindsaya, Adiantum, Cheilantes, Pellaea, Paesia, Pteris, Doodia, Athyrium, Diplazium, Nephrolepis, Arthropteris, Cyclophorus, Lygodium, Todaea, Marattia (Filices), Azolla (Salviniac.) Phylloglossum (Lycopod.), Tmesipteris, Psilotum (Psilotac.), Agathis (Araucariac.), Freycinetia (Pandanac.), Sparganium (Sparganiac.), Paspalum, Isachne, Oplismenus, Simplicia*, Amphibromus, Arundo (Gramin.), Mariscus, Fimbristylis, Lepidosperma (Cyperac.) Rhopalostylis (Palmae), Lemna (Lemnac.), Sporadanthus* (Restionac), Rhipogonum. Dianella (Liliac.), Bagnisia (Burmanniac.), Dendrobium, Bulbophyllum, Earina, Sarcochilus, Spiranthes, Orthoceras, Caleana, Acianthus, Cyrtostylis, Pentalochilus*, Calochilus, Townsonia (Orchid.), Peperomia, Macropiper — also coastal (Piperac), Ascarina (Chloranthac.), Paratrophis — also coastal (Morac.), Elatostema, Parietaria, Australina (Urticac.), Persoonia, Knightia (Proteac.), Mida (Santalac.), Loranthus, Phrygilanthus (Loranthac.), Dactylanthus (Balanophorac.), Polygonum (Polygonac.), Alternanthera (Amarantac.), Hedycarya, Laurelia (Monimiac.), Beilschmiedia, Litsaea, Cassytha (Laurac,), Ackama* (Cunoniac.), Chordospartium*, Notospartium* (Legum.), Pelargonium (Geran.), Phebalium, Melicope (Rutac.), Dysoxylum (Meliac.), Pennantia (Icacinac.), Hoheria* (Malvac.), Elatine (Elatinac.), Melicytus (Violac.), Tetrapathaea* (Passiflor.), Eugenia (Myrtac.), Schefflera (Araliac.), Centella, Daucus (Umbell.), Olea (Oleac.), Geniostoma (Loganiac.), Sebaea (Gentian.), Calystegia — also coastal (Convolv.), Tetrachondra (Tetrachondrac.), Vitex, Teucridium* (Verbenac.), Scutellaria (Labiatae), Jovellana (Scroph.), Rhabdothamnus* (Gesneriac.), Alseuosmia* (Caprifoliac.), Colensoa* (Campan.), Siegesbeckia, Centipeda, Braehyglottis*, Picris (Compos.).
The principal families and genera of the lowland flora, together with the number of species to each are as follows: — (families) Filices 91, Orchidaceae 51, Cyperaceae 48, Compositae 43, Scrophulariaceae 22, Leguminosae 20, Rubiaceae 17, Gramineae 15, Myrtaceae 12, Ranunculaceae 11, Umbelliferae, Liliaceae, and Onagraceae each 10, Pittosporaceae and Araliaceae each 9; (genera) Coprosma 13, Olearia 12, Thelymitra and Carmichaelia each 11, Hymenophyllum and Carex each 10, Scirpus, Pterostylis, Pittosporum and Hebe each 9, Blechnum, Cladium and Epilobium each 8, Trichomanes, Dryopteris, Lycopodium, Juncus and Metrosideros each 7.
Coming next to the distribution of the 559 lowland species in New Zealand proper, 190 occur from about the north of North Island to about the south of South Island and of these 106 extend to Stewart Island; 499 (155 confined thereto) occur in North Island and of these no less than 105 are found only to the north of lat. 38°, or extend only a short distance south of that line; only 398 (54 confined thereto) occur in South Island, and of these the large number of 120 lie to the north of lat. 42°, or do not extend very far to the south of that line, leaving only 276 species for page 119the South Island lowland flora proper; finally 120 (5 confined thereto) occur in Stewart Island. Change of altitude brings about considerable change in the flora. Thus 133 species ascend only to between 600 and 900 m. (mostly in North Island, much lower in most of South Island), but of these 110 do not ascend to more than 100 m. and some of these are confined almost to sea-level, while 75 are so rare as to be of no moment with regard to the general vegetation.
The lowland-high mountain element of the flora consists of 339 species (60 families, 158 genera). The following families and genera, absent in the purely lowland element, are represented: — (families) Marsiliaceae, Balanophoraceae, Portulacaceae, Saxifragaceae, Stackhousiaceae, Plantaginaceae (coastal also), Stylidiaceae; (genera), Alsophila, Pteridium, Leptopteris (Filic.) Pilularia (Marsiliac), Hierochloe, Trisetum (also coastal), Deyeuxia, Triodia, Koeleria, Danthonia, Poa, Festuca, Agropyrum (Gramin.), Hypolaena (Restionac.), Phormium, Enargea, Chrysobactron, Arthropodium (also coastal), Microtis, Townsonia (Orchid.), Tupeia* (Loranth.), Montia (Portulac.), Scleranthus (Carophyl.), Myosurus (Ranun.), Sisymbrium (Crucif.), Quintinia, Ixerba*, Carpodetus* (Saxifrag.), Acaena — also coastal (Rosac.), Stackhousia (Stackhousiac.), Aristotelia (Elaeocarp.), Viola (Violac.), Oreomyrrhis, Lilaeopsis, Aciphylla (Umbel.), Siphonidium* (Scroph.), Plantago — also coastal (Plantag.), Isotoma (Campan.), Oreostylidium*, Forstera (Stylid.), Vittadinia, Pachystegia*, Cassinia — also coastal, Microseris, Taraxacum (Compos).
With regard to the distribution of the 339 lowland-high mountain species 138 (40%) occur throughout North and South Islands, 286 in North Island (9 being restricted thereto) but of these 132 are wanting to the north of the Thames subdistrict and by far the greater part appear for the first time (i. e. in proceeding from north to south) in the East Cape, Volcanic Plateau and Egmont-Wanganui districts. South Island possesses 330 species (42 being confined thereto) and Stewart Island 181.
The species of the element under consideration may be roughly divided into the following 3 classes to each of which is appended its number of species: — (1) species most frequently lowland 123; (2) those most frequently high-mountain 104; (3) those belonging equally to either class 112. These figures might give the impression that the lowland-high mountain species belong equally to these two floras, but this would be erroneous. To begin with, about 50 per cent. of the species are absent in the Auckland districts, if the Thames subdistrict be excluded; further, 258 species do not extend upwards beyond the lower-subalpine belt, and only 69 and 12 species respectively enter the upper subalpine and alpine belts. The greater part, indeed, of the 339 species attain their extreme altitudinal limit either in that portion of the tussock-grassland area where lowland and high-mountain species mingle or to the montane and subalpine forest, the page 120members of which are exposed to conditions materially different from those of an open subalpine or alpine hillside. Further, many plants of lowland lakes, swamps and bogs find conditions not very different from what they are accustomed in the allied habitats up to about 900 m. altitude. So, too, the conditions offered by rocks and riverbeds from sea-level to 600, or even 900 m. altitude in some localities, are pretty much the same.
Some of the species common to the lowlands and the high mountains, including some of the category which descend to the lowlands only under special circumstances, occur so abundantly both in certain lowland, or coastal, and high mountain formations as to be of great physiognomic importance, especially Polystichum vestitum, Gleichenia circinata, Podocarpus nivalis, Poa Colensoi, P. intermedia, P. caespitosa, Festuca novae-zelandiae, Danthonia Raoulii var. rubra, Hypolaena lateriflora, Phormium Colensoi, Nothofagus Menziesii, Weinmannia racemosa, Discaria toumatou, Leptospermum scoparium, Metrosideros lucida, Dracophyllum longifolium, Suttonia divaricata, Hebe salicifolia, H. Hulkeana, Coprosma foetidissima, Pachystegia insignis, Raoulia australis, R. lutescens, R. tenuicaulis and Cassinia Vauvilliersii. Although the same species may be present in the subalpine, alpine and lowland belts yet under the local environments the life-form may be altogether different as in the case of Leptospermum scoparium, as a low tree in lowland forest and a prostrate, rooting mat on subalpine moor, or Weinmannia racemosa a tall, massive tree in the lowlands and a dense shrub in the subalpine scrub.