Art. XI.—On a Subalpine Element in the Flora of Banks Peninsula.

Transactions and Proceedings of the Royal Society of New Zealand, Volume 46, 1913, Page 56

Art. XI.—On a Subalpine Element in the Flora of Banks Peninsula. By R. M. Laing, M.A., B.Sc. [Read before the Philosophical Institute of Canterbury, 6th August 1913.] There is to be found on the hill-tops of Banks Peninsula a plant association of a totally different character from that which clothes, or has recently clothed, the lower portions of the hills. This association, though consisting of species which often reach sea-level in the southern parts of New Zealand, may be termed “subalpine,” in that on Banks Peninsula it is generally found at altitudes of 2,000 ft. and upwards, though in places some of the species belonging to it extend downwards to 1,500 ft. (as on Cooper's Knobs), or even lower. There are traces of it on the Lyttelton Hills, it is more conspicuous on Cooper's Knobs, and it is abundant on Mount Herbert, Mount Fitzgerald, and Mount Sinclair, the highest points of the peninsula. It is found, as a rule, most fully developed on the southern sides of the hills. These are generally rockier and steeper than the northern flanks, and, being exposed to the south-westerly winds and rains, are generally colder and moister than the drier northern faces, which are exposed more fully to the rays of the sun.

On Mounts Fitzgerald and Sinclair the subalpine element is best developed. Several species occur there which I have not found elsewhere. On approaching the latter mountain from the south-east by the old Purau line we find the bush suddenly disappear at about 2,600 ft., and the remaining portion of the peak is covered with a subalpine meadow, approaching, however, in some of its characteristics to a fellfield. The plant association is composed chiefly of Danthonia flavescens (var. apparently intermediate between D. flavescens and D. Raoulii), interspersed with Achiphylla Colensoi, Hierochloe redolens, Danthonia semiannularis, D. Cunninghamii, Phormium Cookianum, and tufts of Poa Colensoi. A little farther up, Raoulia glabra, Wahlenbergia saxicola, Anisotome aromatica, Drapetes Dieffenbachii, and Ourisia macrophylla (forma) make their appearance. None of these yet mentioned, except Hierochloe redolens, Poa Colensoi, and Danthonia semiannularis are to be found lower down the mountain-side. On Mount Fitzgerald other subalpine forms appear. Amongst these may especially be noted an unexpected form of Veronica Lyallii. This species I have not seen elsewhere on the peninsula. Indeed, several of the species here show some variation from the typical forms. This is perhaps not to be wondered at, as the Ourisia and Veronica are not to be found nearer than Porter's Pass, fifty miles away. It is almost to be expected that, as far at least as alpine plants are concerned, these hill-tops should present the characteristics of an insular flora. The nearest point to the peninsula at which Drapetes occurs is Mount Gray, some thirty-odd miles to the northward. Between Mounts Sinclair and Fitzgerald is to be seen the beginnings of a subalpine scrub, consisting of Dracophyllum uniflorum var. acicularifolium, Myrsine divaricata, Olearia ilicifolia, and O. nummularifolia—an unexpected species, not to be found elsewhere on the peninsula, so far as I know. A silvery-white form of Acaena Sanguisorbae is also abundant between this point and Mount Herbert, and is occasionally to be met with elsewhere. On the south-eastern slopes of the peninsula there has been a Nothofagus forest, which perhaps may also be included under the term “subalpine,” as it occupied chiefly the tops of the hills. It is now nearly completely destroyed; but at one time it stretched along the tops of the ridges behind Long Bay* This is the Long Bay on the eastern side of the peninsula to Damon's Bay, outside Akaroa Heads. The forest crosses the ridge to the Akaroa side of the hills immediately behind the town near the Stony Bay track, but I have not been in this portion of it. It probably does not descend anywhere below 1,500 ft. The species of beech represented in it are Nothofagus fusca, N. cliffortioides, and N. Solandri. N. fusca is there in largest quantity, and often in magnificent specimens. N. Solandri is found on the ridge immediately behind Long Bay, varying much in the form of its leaf, which sometimes approaches that of N. Blairii. Small quantities of N. cliffortioides are intermingled with it. Cordyline indivisa and Panax Colensoi, which are not common elsewhere on the peninsula, occur within or on the edges of the forest, together with a considerable number of other species which, however, are elsewhere abundant on the peninsula. The presence of this subalpine element is perhaps to be expected on hills which reach to an altitude of 3,000 ft., particularly when it is remembered that many of the species here recorded come to a lower level elsewhere.

It may, however, be pointed out that on the same hills many northern species find their southernmost limit, at least on the east coast—e.g., Macropiper excelsum, Alectryon excelsum, Passiflora tetrandra, Dodonaea viscosa, Rhopalostylis sapida, Corynocarpus laevigat, and Hedycarya arborea. The lower valleys of the hills are almost subtropical in character, whilst the hilltops have a vegetation similar to that of the adjacent alps. The contrast is a striking one, as within 2,000 ft. one can pass from a coastal flora with strong resemblances to that of Nelson or Wellington to a plant association of a subalpine type. Indeed, though containing fewer species, the association at the tops of Mounts Sinclair and Fitzgerald are very similar to those met with at similar or somewhat greater heights on the Canterbury mountains between Mount Torlesse and Mount Gray. It should, perhaps, be mentioned here that the existence of this subalpine florula was pointed out as long ago as 1869 by Sir Julius von Haast (Trans. N.Z. Inst., vol. 2, p. 118), who, in classifying the main zones of vegetation in Canterbury, writes thus: “Subalpine zone… It ranges from 2,500 ft. to 4,500 ft., and includes the lower portion of the interior of the province and the highest summits of Banks Peninsula.” No attempt, however, so far as I know, has been made to describe the phytogeography of this locality, except in so far as there are species from it recorded in the lists of Messrs. J. F. and J. B. Armstrong, in vols. 2 and 12 of the Transactions. The following species, recorded by Mr. J. F. Armstrong, might be expected to appear in this list, but I have not seen them on Banks Peninsula: Craspedia alpina, Epilobium crassum, Veronica Raoulii. The same may be said of the following additional species recorded by Mr. J. B. Armstrong: Ranunculus pinguis, Acaena adscendens, Drosera binata, Epilobium purpuratum, Pozoa hydrocotyloides, Ligusticum piliferum, Celmisia coriacea, C Lyallii, C. spectabilis, Cotula pectinata, O. pyrethrifolia, Raoulia tenuicaulis, Myrsine nummuularia, Myosotis capitata, Veronica cupressoides, Euphrasia Monroi. Most of these have clearly been recorded in error; others possibly have once existed on the peninsula, but have now become extinct. It is barely possible that one or two of them may still be found. Attached is a list of the species that may be regarded as confined to the mountain-summits of the peninsula. Whether this florula is to be regarded as a collection of waifs and strays or the remnant of a more widespread flora of glacial times I shall not endeavour to discuss here. List of Species. [Those marked with an asterisk have apparently not been recorded hitherto from Banks Peninsula.] 1. Aciphylla Colensoi* Hook. f. 2. Anisotome aromatica Hook. f. Cooper's Knobs, and generally abundant above 1,800 ft.; also on The Tors (Lyttelton Hills). 3. Anisotome Enysii(?) (T. Kirk) Laing. Castle Rocks, Heathcote, One Tree Hill, hills behind Akaroa; occasionally found below 1,000 ft. 4. Cordyline indivisa Steud. Near the Akaroa Summit Road and in beech forests. 5. Danthonia flavescens Hook. f. Common above 1,500 ft. 6. Dracophyllum uniflorum Hook. f. var. acicularifolium Cheesem. Cooper's Knobs, and common above 1,800 ft. 7. Drapetes Dieffenbachii Hook. f. Common above 2,000 ft.

8. Lagenophora pinnatifida* Hook. f. Summit of French Peak, and at edge of beech forest, and on northern ridge of Waikerakikeri Bay. 9. Gaultheria antipoda Forst. var. depressa Hook. f. Mounts Fitzgerald and Sinclair. 10. Gunnera monoica Raoul. Ridges behind Akaroa. 11. Libocedrus Bidwillii Hook. f. From Mount Sinclair to hills behind Akaroa. 12. Myosotis pygmaea Col. Possibly not uncommon, but easily overlooked. Though elsewhere fourd at sea-level, this is only to be seen on the hill-tops of the peninsula. Doubtless the greater amount of moisture there has determined the situation. This is probably true also of Lagenophora pinnatifida, which I found only on the very summit of French Peak, and on the top of the ridge elsewhere. 13. Myosotis australis R. Br. Lyttelton Hills; rare (with white flowers only). 14. Nothofagus cliffortioides* (Hook. f.) Oerst. Long Bay Ridge. 15. Nothofagus Solandri (Hook. f.) Oerst. Long Bay Ridge. 16. Nothofagus, fusca (Hook. f.) Oerst. Stony Bay to Damon's Bay. 17. Olearia ilicifolia* Hook. f. Mount Sinclair (2,500 ft.), Purple Peak. Sometimes found at lower altitudes on the peninsula. 18. Ourisia macrophylla (forma) Hook. Common above 2,000 ft., forming matted patches which cover the ground to the exclusion of all other vegetation. The plant is always creeping; petioles, midribs, and veins pilose, upper surface and margins of the leaves more sparsely covered with short hairs. Leaves membranous, capsule¼ in. long or less. Flowers, December to February. The same form occurs at Reefton, and doubtless elsewhere on the West Coast. 19. Oxalis magellanica* Forst. Mount Fitzgerald. 20. Pentachondra pumila R. Br. Brasenose only. 21. Raoulia australis Hook. f. Purple Peak only. Originally found by Raoul; now apparently almost extinct. 22. Raoulia glabra* Hook. f. Common above 2,000 ft.; Lyttelton Hills, very rare. 23. Schizeleima Hookeri* (Drude) Donin. Rare; Mount Pleasant, Lyttelton, behind Governor's Bay, near sea-level in Checkley's Bush (Akaroa). 24. Senecio lagopus Raoul. Turf hill-tops behind Akaroa. 25. Senecio saxifragoides Hook. f. A common chasmophyte above 1,000 ft., generally on the south-west faces of the hills. 26. Uncinia rubra Boott. in Hook. f. Tops of Mounts Fitzgerald and Sinclair, and probably elsewhere. 27. Veronica Lavaudiana Raoul. Abundant, and coming down to 900 ft. 28. Veronica Lyallii (forma) Hook. f. Forming dense patches, often covering many square yards on the southern faces of the cliffs on Mount Fitzgerald. Leaves 1/10 in. to¼ in. long, with only two serratures on each. Racemes 1 in. to 2 in. long, rising from near the ends of the branches; apparently a dwarf form. The plant has the leaves of V. Bidwillii, with the inflorescence of V. Lyallii. 29. Wahlenbergia saxicola* A. D.C. Top of Mount Sinclair. Though else-where at sea-level, here only on the highest summits.