FLORA OF MOUNT COOK

Otago Witness, Issue 3698, 27 January 1925, Page 11

FLORA OF MOUNT COOK

By

Arnold Wall.

I—THE FIELD DEFINED. This account of the flora of Mount Cook is intended primarily as a handbook to the Alpine flora of the Moimt Cook district, but as The Hermitage itself is close to the Grassland of tne Hooker Valley, and as this Grassland extends to at least a thousand feet above the floor of the valley, especially on the southern spurs of Mount Wakefield, it has proved impossible to exclude this important plant-community, and a fairly full study of it is here given in its proper place. However, a line must bo drawn somewhere and the author decided to "ncludo all the ground north of Sawyer’s Creek and Rotten Tommy; he thus excludes tho great swamps of the Tasman Valley and I/ako rukaki, which lie beyond the seo of a work of this nature. Tho field, therefore, comprises the whole of tho Sealy Range and Sebastopol, Sawyer’s Creek, tho margins of the three groat glaciors and tho ranges abovo t horn; the Mount Cook Range, and the Malto Rrun Range. Tho Liebig Range has not been included, but it is improbable that many species are thus passed over. On the Sealy Range, Mount Softon, the Copland Range, on Mount Cook, and on Malte Brun the upward limit of vegetation has been reached and surveyed, and all plants growing noar this frontier are hero listed in their duo places; this limit in general stands at about 7000 ft, but on the Mlalte Brun Ran go at over 9000 ft. Tne vogotation of the Mount Cook district consists in the main of a zone from 3000 ft to 4000 ft broad between tho barren glacier below and the etornal snows above. Where the glaciors terminate, however, ordinary Grassland is soon established, and this is continued southward into the Mackenzie Plains. Above, the snowline makes a natural barrier, but so eager and so resouroeful is Nature that wherever bare

rocks appear, either on precipitous consolidated cliffs, as on Malte Brun and Aiguille Rouge, or on looser and more rapidly disintegrating surfaces, as on the Haast Ridge or about the head of the Tasman Glacier, certain plants will find a footing, even up to an altitude of over 90C0ft—these comprise certain species of veronica, gentian, myosotis, and a few grasses. Even quite small and completely isolated areas of rock are sometimes found to harbour a tenant or two at great altitudes

Owing to the central position of Mount Cook as regards a “ north and south ” distribution, its flora is very typical of the Southern Alps as a whole, and the great majority of its plants and plant-associa-tions are such as will generally be found elsewhere, especially along the eastern side of the whole great range which forms the backbone of the South Island. This flora might bo more correctly described as Eastern Central. Tho Main Divide is everywhere a very clear botanic frontier, separating two widely differing types of vegetation. The majestic rain-forest of Westland, with its tall trees of many sorts, and its great wealth of filmy ferns and other epiphytes, tho rain-loving shrubs

such as Olearia Colensoi, and the strangelooking, broad-leaved tree Dracophyllums, are entirely absent from Mount Cook and its immediate neighbourhood. Here everything tells of a drier climate; the little forest we have is pure mountain beech, and the flora is approximated the same as that at the heads of the Waitaki, Rangitata. Rakaia, and Waimakariri. A great deal of nor’-west rain, however, falls on tho Main Divide, and its rain-laden gusts generally sweep down the manvalleys of the eastern slope for several miles Ijofore finally parting with their load of moisture. There are, therefore, quite a number of plants which flourish at a distance of from five to ten miles from the Divide, yet cannot live in the truly dry climate of the extreme Eastern Alps, such as that of Mounts Hutt, Torlesse, and Puketeraki. These plants aro all to be found at Mount Cook, and this class includes those two noble kinsmen, Ranunculus Lyallii and Ranunculus Godleyanus, Ranunculus sericophyllus, Veronica Gilliesiana, Coprosma serrulata, Celmisia petiolata, and Celmisia glandulosa. Most oi these occur on the Rangitata down to the Lawrence, on the Rakaia to the Wilberforce, and on the Waimakariri to the Hawdon or North Branch, but very little further east.

If we follow carefully the distribution of particular species we find, owing partly to the great diversity of the surface and partly to tho central position of Mount Cook, certain species which belong quite specifically to one or other of the four chief divisions, north, south, east, and west. Thus at very high altitudes we get the tiny Veronica ciliolata. a typical western plant. On loose shingle and steep slopes of rough detritus occurs Haastia Sinelairii, a true southern form, common on the Otago Alps, but replaced in the north by Haastia recurva; also, Veronica, Buchanani, Celmisia Hector i, and Raoulia Parkii abound here and in Otago, but extend very little further north than this. Among the typical Eastern Alpine plants are Raoulia eximia (vegetable sheep), Exocarpus Ridwillii, Heliehrysum JSelago, 11. depressum, and a few plants of the northern ranges find their farthest south in this neighbourhood. such as Cardamine Enysii, Veronica Haastii, and Schizeilima Haaslii. Very few plants are restricted to this one area, but among those which flourish onlv at very high altitudes there are some which have not hitherto been found elsewhere, such as Ranunculus Grahami and Myosotis suavis. T hese were first collected by Peter Graham during his long career at chief guide at The Hermitage. The noble Ranunculus Godleyanus hag its main centre of distribution hereabouts, extending to the head of the Rakaia on the north and east, and on the west to the Waiho and adjoining rivers.

The complexity of the forces which determine tne character of our flora can be clearly exhibited even within the nartoav limits imposed upon this particular study. Thus although the Mount Cook Range is separated from that of Mount Sealy by a very few miles, a comparison of tne lists of species noted upon them shows that this trifling distance has its effects. Upon the more easterly range of Mount Cook, for example, all along tho summit from the Ball Pass to Mount Wakefield, Haastia Sinelairii, Raoulia eximia, and Heliehrysum Youngii abound, whilst they aro not recorded from the opposite range. On the other hand. Ranunculus Godleyanus and Ourisia macrocarpa figure in the lists from the Copland Range, which is on the Main Divide, but not upon the Mount Cook Range. Here the determining factor presumably is rainfall.

Again, a comparison of tho northern faces of Sebastopol which is only an extended spur of the main Sealy Range—practically the Divide—with the southwardfacing slopes of Governor’s Bush, only a few chains distant, shows that the mere direction of the facing may be the allimportant factor; for here on the one side we see a community ot rain-loving shrubs forming a dense subalpin e scrub, almost like that of the West Coast, whereas on the other we find such plants as manuka, Eaocarpus Bidwillii, and Heliehrysum Selago, all of which belong equally to the flora of the Eastern Alps, and are thoroughly characteristic of a dry climate. Yet again the presence of tho Scabweod (Raoulia lutescens) in the Tasman Valley is due to tho nature of its domicile. The composition and amount of soil (and subsoil, iif any), the degree of isolation, and exposure to violent winds—all these play their part in the determining the character of tho vegetation in such a plaeo, bo that here, within a very few miles of the Main Divide and the rain-forest of the West Coast, wo find the most typical plant oi the depleted lands—the “man-made” desorts —of Central Otago—the driest climate in Now Zealand, Tho plants of the Now Zealand mountains aro nearly all peculiar to this country, and this is not surprising since these ranges stand so far aloof from all others. Our mountain flowers aro for the most part our own pride and Thus all the veronicas, senecios, oleanas, and forget-me-nots, and all the buttorcuns but ono in om list aro found nowhero olse, though these great groups are, of course, represented by othor spocies in other lands. The entire genus Celmisia. with the exception of a solitary species (Celmisia longifolia), found also in Australia and Tasmania, is confined to New Zoaland. Raoulia is in the same position, while tho genus Haastia ig quite unrepresented elsowhera There are, however, some very remarkablo exceptions to this general rule. The

F. rubra) tlro almost world-wide 'in" their distribution though the former is now regarded rather as a distinct species than a i ariety o[ sheep’s fescue, of which Cbewing s fescue is a well-known form. The small Carex pyrenaica, which takes its lame from the Pyrenees, occurs on high mountains tii' .ughout Europe, in North America and Japan, and both (he North and (south Islands of New Zealand. The sweet woodrush of the Old Land, Luzula campestr's „ a i most a citizen Qf lh(> world’ and is recognised in New Zealand in ; varieties, in which one, Var. migrata, ' er y .nke tho common English form. , ? alpine grass, T risetum subspicatum, much is common at high altitudes in the ooiithern Alps, occurs generally in the high mountams of both hemispheres. The common silver tussock (Poa caespitosa) grows also in Australia and Tasmania; ua run on ia semi-annuJaris in Australia; f ° J grass (Ilierochloe reddens) in Fuegia, -Tasmania, and Victoria. he extremely variable Oreomyrrhis anciit ola, of which three very different varieties are recognised in New Zealand is iound, as its name implies, in tho Andes, and it occurs in Australia and Tasmania. J he nearest mountains to ours are those °noAf MS^ra * a - tk® highest of which are over i DOOFt and about 1200 miles distant from Us * A fair number of alpine and subalpine species are common to tho Australian Alps and the Mount*Cook district. Above sOCoft the following species, which are also found in New Zealand, are recorded in the Australian Alps: Poa oespitosa, Luzula campostris, Scleranthus bifloL u f» Pentachondra pumila, Leucopogon crascri, Nertera deprossa, Celmisia longifolia, Ereehtites quadridentata, Microseria Torsten, and a few ferns.

Most of these grow in New Zealand at much lower elevations owing to the differonce in climate, and, in fact all but one or two flourish with us from sea level to about oOOOft or 4000 ft; none of them would be considered as typical alpine, hardly even, as sub-alpine plants. Several of our typical genera, however, are represented by different species from ours in these Australian Alps, such as Dantlionia, Pimelea, Aciphylla, Craspedia, Olearia, Raoulia, and Heliehrysum, and these point to a rather remoter affinity and a longer period oi isolation. It is really but a very minute proportion of the mountain flora of New Zealand that may be said to coincide exactly with that of Australia. The Now Zealand flora as a whole, considered in its relation to the flora of the world, is found to consist c-f fa) a Malayan or tropical element; (b) an Australian element; (c) an element which is called Fuegian or Andine; (d) .on element called by Skottsberg “Old Antarctic,” and (e) an element which Dr Cockayne calls Palacc-Zelandic.

The first of these, the tropical, is naturally absent from the Alpine flora which alone concerns us here. The Australian element above-mentioned points to a time when land was continuous between the present Australia and New Zealand, but beyond saying that this was very long ago indeed, science will not commit herself to any exact period. The Fuegian or Andine element tells us equally clearly of a very ancient connection between New Zealand and South America, probably by way of a circumpolan continent, usually called Antarctica. Genera belonging to this continent, and now existing in both New Zealand and South America, have been called hicentric. Thus (1) genera which originated in South America have reached US' by way of .Antarctica (2) genera which originated here have reached South America by the same route, and (3) genera which originated in Antarctica are now represented in Australia and New • Zealand and South America, especially in the Andes. Among the Andine representatives in the Mount Cook flora are probably Disc-aria, Schizeilima, Oreomyrrhis. and Ourisia. Australian and New Zealand genera which are represented in the Andine America include Astelia, Drapetes, Phyllachne, and parts of Myosotis and Veronica. The old Antarctic element includes many of our typical Alpine genera, such as Oreobolus, Carpha, Uncinia, Rostkovia, Nothofagus Colobantlius, Caltha, Gunnera, and Abrotanella. These are in bare outline the views of Skottsberg. But the whole question is highly debatable; the evidence is so slight, and the time so inconceivably remote that no certain conclusions concerning these distant land connections and the exact sequence of the events may ever be reached. Since it is certain, however, that in the comparatively recent past New Zealand was far larger than it is now, extending eastward as far as the Chatham Islands and the various outlying groups—the Antipodes, Auckland and Campbell Islands—and possibly much further, it seems certain also that a part of our flora, perhaps the main part, originated and developed within New Zealand itself. This element is tho Palceo Zelandic. It is, of course, impossible to decide in the case of many genera, whether they should be considered “Old Antarctic” or “Palseo-Zelandic”; the nature of the evidence does not permit of a hard and fast line. But it. seems fairly certain that Celmisia, Aciphylla, and Raoulia must bo placed among the Palteo-Zelandios; they represent the primitive flora of that continent of which the present New Zealand is merely a relic. These are in bare outline tho views of Dr Cockayne, and the whole subject has been handled by him in a masterly manner in his “Plants of New Zealand and Their Story.”

This conception of a “Greater Ne w Zealand,” isolated for long ages after its connections with either Malaya or Australia had been sundered, is not only a majestio thing in itself, but commends itself as a reasonable hypothesis in full harmony with tho known facts and explaining most of tho strikingly distinctive features of our present flora- During the long period of its isolation certain genera developed very great numbers of species which are peculiar to this country—Veronica. Celmisia, and Kpilobium, for example—and it is quite probable that, numerous as the modern species nre, they represent only a fraction of those that formerly existed. Tho characteristic tree-composites, Olearia and Senecio, which are so conspicuous a feature of tho southern flora of New Zealand and of tho outlying islands also doubtless developed in this area.