The Vegetation of New Zealand
Chapter I. — The Vegetation of the Kermadec Islands
The Vegetation of the Kermadec Islands.
The species of vascular plants number 117 (pteridophytes 38, monocotyledons 25, dicotyledons 54) and they belong to 42 families and 89 genera, the largest families being Filices 33 species, Gramineae 13, Com-page 325positae 9 and Cyperaceae 6, but only 6 genera contain 3 species or more, the largest being Asplenium with 5 species. The elements of the flora are as follows: — Endemic 15 species (9 closely related to New Zealand species and 3 of Polynesian, 2 of Norfolk Island and 1 of New Hebrides affinity); New Zealand 89 of which 65 are Australian, but 45 of such occur in Norfolk Island or Lord Howe Island — one or both; and Australian (other than those also New Zealand) 7. With regard to the destribution of the New Zealand element in New Zealand proper it is as follows: North Island 89 (14 Auckland districts only), South Island 74 (17 extending but little beyond lat. 42), Stewart Island 41.
The general ecological conditions of the Kermadecs are a combination of a humid subtropical1 climate, coastal conditions, and an extremely porous soil. According to W. R. B. Oliver (1910:125) from records from Feb. to March 1908 inclusive calm days are rare and the wind often blows with violence. The rainfall is fairly evenly distributed throughout the year (171 cm. spread over 176 days — Feb. to Oct.). In cloudy and rainy weather a mist continually hangs about the hilltops and its influence is reflected by a distinct forest association. The temperature ranged between a minimum (Aug. 4th) of 8.1° C. and a maximum (Feb. 1st) of 29.4° C. but there were hotter days in January.
The physiognomic plants.
The following are the leading physiognomic plants all of which are either identical with, or closely related to mainland species: — Metrosideros villosa (Myrtac.), Rhopalostylis Ckeesemanii (Palmae), Suttonia kermadecensis (Myrsinac.), Ascarina lanceolata (Chloran-thac.), Myoporum laetum (Myoporac), Corynocarpus laevigata (Corynocarp.), Melicytus ramiflorus (Violac.), Coprosma petiolata (Rubiac), Macropiper excelsum var. major (Piperac), the endemic tree-ferns (Cyathea Milnei, C. kermadecensis) and a number of herbaceous ferns, especially, Pteris comans, Polystichum aristatum, Nephrolepis exaltata, Dryopteris glabella and Blechnum norfolkianum. Only a few of the above need notice.
Metrosideros villosa is either a lofty tree 20 m. high or its massive trunk is more or less prostrate. In the latter case, trunk-like branches pass upwards from the prostrate trunk. Aereal roots are extremely abundant in both forms; in the erect tree they grow downwards, pass into the soil and function as stems; in the prostrate form they make entangled masses at the base of the trunk. The leaves are similar to those of M. tomentosa but smaller.
Rhopalostylis Cheesemanii closely resembles R. sapida but is taller. Suttonia kermadecensis is a low tree, 6 to 10 m. high with smooth reddish-gray bark and dense foliage of elliptic-oblong, dark-green, coriaceous leaves page 326and with the small flowers produced, in part, on the naked twigs. Ascarina lanceolate is a tall shrub or low tree much resembling A. lucida, already described. Coprosma petiolata is very similar to C. chathamica; it varies from a quite prostrate shrub to a low tree 6 m. high. Cyathea Milnei has a stout trunk 2 to 8 m. high, clothed above with persistent withered leaves while C. kermadecensis is a magnificent plant, 15 to 20 m. high with a naked trunk 1 to 2 m. diam. at the base which consists chiefly of aereal roots.
Autecology of the plants.
The trees and shrubs number 22 (trees 17, shrubs 5), but many of the former epharmonically become shrubs. In stature 6 trees are of medium height (sometimes almost tall) and 11 of low stature and 2 shrubs are tall and 3 of medium height. Two trees of but low stature in New Zealand proper in the Kermadecs reach a height of 20 m. or more.
The life-forms and the number of species to each are as fellows:— canopy-tree 4, tuft-tree 3 (ferns 2, palm 1), bushy-tree 10, brushy-shrub 4, straggly shrub 1. One species may perhaps be considered xerophytic and 1 subxerophytic. Aereal roots are abundant in Metrosideros villosa and are in harmony with a moist atmosphere. In wet forest, states Oliver, "the prostrate trunk of a tree may be a metre above ground supported by hundreds of large and small root-props, and sending up large branches like distinct trees".
As for the leaves of the trees and shrubs they may be defined as follows: — compound 5, simple 17, very large 5, large 2, medium-sized 11, small 4, coriaceous, thick &c. 9, thin 13, glabrous 19 and hairy 3.
Herbs and semi-woody plants number 78 of which 13 are annuals or biennials, 4 summergreen, 11 semi-woody, 67 herbaceous, 15 xerophytes or subxerophytes and 63 mesophytes. Regarding height 23 are very tall, 20 tall, 27 of medium stature and 8 of low stature.
The life-forms and number of species to each are as follows: — (1) Annuals and biennials 13, consisting of creeping and rooting grass 1, erect tufted grass 2, turf-making grass 1, erect-branching herb 8 and erect-branching semi-woody plant 1. (2) Perennials 65, consisting of: (a) semi-woody plants 10, which include (a) wandering 3, consisting of erect-creeping lycopod 1, straggling and branching plant 1 and mat-herb 1; and (?) spot-bound 7, consisting of: prostrate-straggling plant 1, large succulent mat-plant 1, erect-branching plant 3 and straggling plant 2; and (b) herbaceous perennials 55, which include (a) wandering 19 consisting of: erect-creeping 12 (ferns 9, rush 1, grass 2), mat-herbs 6 and tufted rush 1; and (?) spot-bound 36 consisting of: erect unbranched fern 1 (summergreen), tufted 20 (ferns 12, grass-form 8) tussocks 6 (grass 2, rush 3, sedge 1), earth-orchids 2, erect-branching herbs 5, semi-erect branching 1 and trailing herb 1.
The leaves of the plants here dealt with may be characterized as follows: compound 25, simple 49, very large 16, large 6, of medium size 18, page 327small 25, very small 9. coriaceous &c. 26, thin 48 glabrous 65 and hairy 9, 4 species are leafless.
Lianes and epiphytes, similar to those so characteristic of forests in New Zealand proper, are wanting, but there are a few lianoid coastal herbs and in wet forest many bryophytes and some of the usual New Zealand epiphytic pteridophytes.
The plant communities.
Here I am not usually giving names to the associations based on the nature of the vegetation, or the dominance of species, but am mostly distinguishing them by the nature of their edaphic position
Coastal-rock vegetation is related to that of the North Auckland district. The following are important members: — Asplenium obtusatum, Poa poly-phylla (endemic), Mariscus ustulatus, Scirpus nodosus, Parietaria debilis, Mesembryanthemum australe, Tetragonia expansa, Apium prostratum, Samolus repens var. strictus, Lobelia anceps and Coprosma petiolata (endemic).
Talus slopes at the base of sea-cliffs, named by Oliver Mariseus slopes, are covered with close-growing tussocks of Mariscus ustulatus together with the ferns Pteris comans and Hypolepis tenuifolia, tussocks of Scirpus nodosus and Carex kermadecensis and shrubby Myoporum laetum.
Coastal scrub forms a belt, where there is sufficent space, between the foot of the cliffs and high-water mark; it also constitutes most of vegetation of Meyer Island. Shrubby Myoporum laetum is dominant. Other members of the association are: Pteris comans, Mariscus, Carex kermadecensis, Macropiper excelsum var. major, Canavalia obtusifolia and Sicyos australis (tendril liane).
Sand dunes are extremely limited in area. Ipomaea pes caprae is easily dominant and extends for some metres on to the beach, other species are Imperata Cheesemanii (endemic), Scirpus nodosus and Apium prostratum.
Gravel flat vegetation occurs in Denham Bay and extends for 2 km. with an average width of 74 m. It is subject to frequent drenching by sea-spray. The leading species are: — Ipomaea pes caprae (dominant), Imperata Cheesemanii, Deyeuxia Forsteri, Mariscus ustulatus (sub-dominant), Scirpus nodosus (abundant), Tetragonia expansa, Myoporum laetum, Calystegia Soldanella, Scaevola gracilis and Erechtites prenanthoides.
Inland rocks bear the following important rock-plants:— Cyclophorus serpens, Asplenium Shuttleworthianum, Psilotum triquetrum, Carex kermadecensis, Peperomia Urvilleana, Mesembryanthemum australe, Hydrocotyle moschata, Hebe breviracemosa (endemic), Scaevola gracilis (endemic) and Lagenophora pumila.
Warm ground near steam vents where the steam strikes directly contains no plants, but at a short distance away there is a close growth of Nephrolepis axaltata, Polypodium diversifolium, Lycopodium cernuum, Psilotum triquetrum and Paspalum scrobiculatum.page 328
Swamps are few and small. Typha angustifolia var. Brownii is dominant. Other species are: — Blechnum procerum, Histiopteris incisa and Juncus polyanthemos; where the water is shallow near the margin of the Green Lake there is a belt of Typha.
Forest occupies virtually the whole of Sunday Island and is a distinct expression of climate. The forest may be divided into the two classes, wet and dry.
Wet forest is composed of a mixture of trees none of which is dominant. The principal trees are: —Ascarina lanceolata, Melicytus ramiflorus, Notho-panax kermadecensis, Suttonia kermadecensis and Coprosma acutifolia. Metrosideros villosa, of huge dimensions, occurs in places. Frequently one species or another makes a pure stand. Rhopalostylis Cheesemanii and Cyathea kermadecensis are generally extremely plentiful. The abundance of epiphytic ferns is a striking feature.
Dry forest is characterised by the dominance of Metrosideros villosa. The average height is some 20 m. There are 3 tiers of vegetation. Different combinations form the lowermost tier in different localities, e. g. Polystichum aristatum 1 to 2 m. high may make an impenetrable mass, or Nephrolepis cordifolia occupy wide areas, its matted roots spreading, over the ground or fallen logs or climbing the tree-fern trunks, or again the undergrowth be merely a dense mass of the stems of Macropiper. The second tier may consist of small trees, the palm and tree-ferns, the first-named being especially Melicope ternata, Boehmeria dealbata, Coriaria arborea, Corynocarpus laevi-gata, Melicytus ramiflorus, Suttonia kermadecensis, Myoporum laetum and Coprosma acutifolia. In places the palm forms colonies (Fig. 94). The third tier consists of the Metrosideros together with Corynocarpus and Myoporum which almost equal it in stature. The forest-roof is fairly dense.
1 1) According to Cheeseman (1888: 156–7) various tropical fruits or vegetables were grown by the settler who then, with his family lived on the main island, e. g. the banana, sugar-cane, pineapple, guava, custard-apple, mango, oranges, shaddocks and citrons.