THE UNIQUE FLORA AND VEGETATION OF NEW ZEALAND.

Forest and Bird, Issue 22, 1 October 1930, Page 8

THE UNIQUE FLORA AND VEGETATION OF NEW ZEALAND.

For various reasons the plant-life of New Zealand is of peculiar interest, especially its extreme isolation from other landmasses, its flora of diverse origin but with an astonishing number of endemic* species and group after group of wild hybrids, the numerous and often peculiar life-forms of its members, its having developed unmolested by grazing and browsing mammals, and its vegetation, so diversified that only a continent extending into the tropics can claim an equality. The ferns, fern-allies, and seed-plants by no means make up the whole New Zealand flora, but in addition hundreds of species have been described of the less highly organised plants (the mosses, liverworts, algae, fungi, etc.), but they certainly do not nearly represent the total number of such.

Taking the flora as a whole, a large proportion of the species are evergreen; conspicuous flowers are far from common; annuals and plants which die yearly to the ground are rare; water-plants are few in number; turf-making grasses are not abundant ; and bulbous plants are almost negligible. Altitude, on the one hand, and proximity to the coast, on the other, have a profound bearing on the distribution of the species. Thus about 140 species are confined to the coast-line or its immediate vicinity, and 9 families and 35 genera containing 41 species are virtually coastal. Then there are about 560 species which are confined to the lowlands and lower hills, and there are no less than 24 families and 103 genera which are purely lowland. Finally, there is a plentiful high-mountain flora, with about 510 species belonging to 38 families and 87 genera, which never descend to the lowlands, but as compared with the lowland flora the number of genera (only 16) confined to the high-mountain belt is trifling.

Latitude has also a strong bearing on plant-distribution, and, apart from a gradual change, there are three critical parallels of latitude—36 deg. S., 38 deg. S., and 42 deg. S.— near which (it may be somewhat to the north or south of the line) many species attain their southern limit. On the other hand, Cook Strait and Foveaux Strait are of but little moment as barriers to advance or retreat. Far greater is the influence of wet and dry local climates, which is most striking when two such areas impinge on one another as in the case of the wet area which extends from the Tasman Sea to near the eastern base of the Main Divide, which is forest-clad to the timber-line, and the dry area extending thence to the east coast, which is clothed *Found wild nowhere else.

with tussock-grassland. In the dry area of Marlborough and the contiguous wet western area of north-western Nelson, there are 36 species confined to the dry area (locally endemic) and 39 to the wet area. So, too, dry Central Otago possesses 15 locally endemic species. Speaking of the distribution of the species in a wide sense, there is every transition, from those which extend continuously from the north of the North Island to Stewart Island to those found in only one limited area.

The physical features of New Zealand; its many types of climate, especially with regard to the annual rainfall and the number of rainy days; its varied altitude, ranging from sea-level to the snowfields of the Southern Alps; its many kinds of soils, particularly their water-holding capacity; the diverse frosttolerating ability of the species; their aggressive powers — largely a matter of their life-forms and inherent plasticity—all these and other factors have led to a most varied Vegetation made up of a host of plant communities, some of which appear out of place in the Temperate Zone. Thus between tide-marks in the northern rivers and estuaries there is a true mangrove community—an unexpected occurrence outside of the tropics; and even so far south as north-western Nelson groves of tall palm-trees are a striking feature. But, more than all else of an unexpected character —though familiar enough to all New Zealanders—is the lowland forest, which resembles in no whit the forests of temperate Europe, Asia, or America, but is a true tropical rain-forest. This tropical character is shown in its groups of tall tree-ferns, which may exceed 40 feet in height; in its wealth of ferns of all kinds; in the abundance of woody, ropelike climbing-plants and huge perching-plants far up in the forest canopy; in the several tiers of undergrowth, consisting of low trees and tall shrubs with smaller shrubs and ferns beneath. and the ground clothed with a deep carpet of filmy ferns, liverworts, and mosses, while the tree-trunks are similarly clad: in short, the forest exhibits prodigal luxuriance of growth, and Nature, as it were, runs riot. Rarely does one tall canopy tree dominate, but the uppermost storey of the forest is constructed out of the crowns of various kinds of trees growing side by side, just as the undergrowth is composed of many species. But no forest is homogeneous in its structure, for differences in the topography of the area, in the water content of the soil, and in the relative amount of light in the interior of the forest, lead to various combinations of species. All the same, especially so far as the tall trees are concerned, there is an advance towards stability and uniformity, so that all the forests if not interfered with are progressing towards a “climax association,” as it is named, with (as a rule) the tawa (Beilschmiedia tawa ) dominant

to the north of latitude 42 deg., and the Kamahi (Weinmannia racemosa ) dominant southwards.

The vegetation of the high mountains is both of great scientific interest and full of rare beauty. It is composed of no less than 966 species, and it is certain that a good many more species will be discovered. How strongly of New Zealand origin is the flora is revealed by the fact that of the 514 purely high-mountain species all except 16 are endemic, and probably sof these are endemic also. The headquarters of the true high-mountain species is in the South Island, their total being 473, as compared with 105 for the North Island, a matter which should cause no surprise since the area for plants above the forest-line is far and away less than in the South Island, where also the average height of the mountains is much greater.

With but few exceptions the most beautiful flowers of New Zealand belong to the high-mountain flora, so that in due season many plant-communities are natural flower-gardens of extreme loveliness. There are the giant buttercups, white and yellow but nearly all the flowers are of these colourswhich may be seen by the acre; the lovely ourisias, with the flowers in whorls round the stem, tier above teir, as in some of the Asiatic primulas, or the glistening green leaves, as in O. caespitosa, may form mats on stony ground bearing multitudes of delicate blossoms ; the eyebrightstrue alpine gemstheir flowers white with a yellow eye or purple throat, or yellow altogether; forget-me-nots, yellow, bronze, purplish, or white; the snow-groundsel, its large marguerite-like flowers produced in such profusion that the mountain-meadow glistens like a snowfield; the two kinds of edelweiss, far surpassing their Swiss elder sister in beauty, the flowers of the “everlasting” kind, their outer leaves flannelly and snow-white. But above all other plants of the mountains, not only for their beauty of flower, leaf and form, but for their abundance in all situations, come the various species of Celmisia. “Go where you will”—to quote from “The Vegetation of New Zealand” (ed. 2, p. 238) — sub-alpine and alpine herb-field and their silvery foliage strikes the eye, it may be in stately rosettes of dagger-like leaves, in circular mats trailing over the ground, or in dense cushions. Their aromatic fragrance fills the air; from early till late summer some of their white heads of blossom may be seen, while in due season, gregarious species clothe both wet herb-field and dry stony slopes with sheets of white.”

. . . . Finally, in course of time, a state of stability will be reached, and a new flora, composed partly of exotic plants and partly of those indigenous to the soil, will occupy the land, and save in the national parks and scenic reserves, but only if these are kept strictly in their natural condition as to both plants and animals, this new flora will build up a vegetation different from that of primeval New Zealand. Extract from “The New Zealand Official Year-Book, 1930, by Dr. L. Cockayne, C.M.G., Ph.D., F.R.S.