The Dunedin Sub-district of the South Otago Botanical District
[Read before the Otago Branch, September 14, 1937; received by the Editor, September 15, 1937; issued separately, March, 1938.]
The first volume of the Transactions of the New Zealand Institute in 1868, “nearly a century since the botany of New Zealand first became known to science” as Colenso remarks, included a series of remarkable studies on the geographical botany of New Zealand by Buchanan, Colenso, Hector, Monro, and Travers. Especially note-worthy are Colenso's pioneer attempt to divide North Island into definite areas and vertical belts, and Hector's division of South Island into zones under the governance of the Southern Alps. Hector's results are summarised in his “ideal section” across the island from the west coast, through Mt. Aspiring, Lake Wanaka, the Lammer-moors, Taieri Hill and Dunedin, in which the contrast between the forested coastal areas and the tussock-grassland of the interior is diagrammatically shown. He remarks: “The mixed bush on the East Coast presents a marked difference from that on the west; on the whole, the timber is better grown and of larger size, and there is a much greater variety of Pines. Its most characteristic development is around Dunedin, where it is rare to meet any Ironwood, Karmahi, or Birch, which are so common on the west, Black and White Birch being wholly wanting … The plains are covered with grasses, the roots of which are gathered into tufts or tussocks, intermixed with the Bayonet grass or “Wild Spaniard” (Aciphylla Colensoi), Toumatakuru (Discaria toumatou), and a great variety of the New Zealand brooms (Carmichaelia), with small Orchids, Pimelias, and ericaceous plants.
“Advancing towards the east, the grasses acquire a different character, indicating the influence of moisture derived from the eastern sea-board.
“The yellow tussock predominates, and is intermixed with a rank growth of fern (Pteris aqulina var. esculenta), Tutu (Coriaria), several species, Flax (Phormium tenax), and the soft-leaved spear-grass (Aciphylla sqarrosa), all of which latter plants rarely occur in the interior or lake district.”
Despite this excellent start, and though much detailed exploration followed, botanists still mainly continued to refer their distributional discoveries to the political divisions, until Cockayne (1917) published his proposed botanical districts. Nor has the influence of the political boundaries yet been completely overcome, though subsequent work has shown Cockayne's natural divisions to have been on the whole well-founded. As he stated (loc. cit., p. 62) “the actual boundaries of many of the districts are extremely hard to fix, and in no few cases must always be artificial, though that detailed research which must take place in due course as phytogeographic workers increase in number will eventually find out the most natural limits.” In view of the warfare waged by man against the indigenous vegetation, however, this detailed work becomes urgent. We present the results of a close survey of a particular area, made at the suggestion of Cockayne and as a contribution to the desired result.
The North Otago Botanical District sharply contrasts with that of South Otago. On the one hand we have an area of low rainfall, great range of temperature, poorer flora and general tussock-grassland cover; on the other an area of comparatively high rainfall, lower range of temperature, richer flora, and general forest-cover. Details may be found in Cockayne (1928). Owing to the topography the boundary between the two districts is irregular, as Cockayne emphasized. This irregularity is most pronounced in the northeastern part of the South Otago District, where a deep wedge of the North Otago District, thrust south to Deep Stream in the Taieri River Gorge, isolates a more or less coastal tongue, which includes the city of Dunedin. We have found that the southern end of this tongue is also well-defined, justifying the demarcation of a definite sub-district.
While boundaries must be shown on the map (Fig. 1) as lines, it is to be emphasized that, except locally, there is a tension belt at the juncture of the districts, and of the sub-district with the main South Otago District. The lines marked, however, connect points from which a definite change in the vegetation can be observed at no great distance on either side. The area here defined comprises approximately 145,000 hectares with the city of Dunedin situated mid-way in its length from north to south, and for convenient reference it may be called the Dunedin Botanical Sub-district. The southern boundary extends from the coast a little to the south of Taieri River to Waitahuna Hill, excluding the whole of the Akatore Creek watershed and including the gorge of the Waipori River. From Waitahuna Hill (685 m.) the western boundary connects the
summit of Mt. Maungatua (897 m.), the ridge of Traquair Station at the junction of the Waipori-Middlemarch roads, Roundridge Hill, Hindon, Mt. Misery (713 m.), Scratchback Hill (701 m.) and Brothers Peak. The northern boundary joins Brothers Peak, Mt. Royal and the coastline at the mouth of Stony Creek.
On the coastal hills outside the southern boundary, kamahi-rata (Weinmannia racemosa-Metrosideros lucida) forest is the dominant feature, contrasting strikingly with the podocarp-dicotyledonous forest of the sub-district which ceases abruptly near Akatore Creek. West of the Taieri Plain, southern-beech (N. Menziesii) forest—as far as the area is concerned—reaches its local southern limit on the slopes of Mt. Maungatua and in the gorge of the Waipori River, and the extension of the boundary to Waitahuna Hill encloses this forest. The western line described above follows ridges connecting high hills sheltering the area from the westerly and north-westerly gales. Forest and shrub-communities, primitive or induced, reach their fullest development in this shelter, but west of this divide grassland has complete control and tall or low tussock dominates according to exposure to sun or wind. Festuca novae-zelandiae is the principal species in the drier positions, but it is replaced by Danthonia flavescens or Poa caespitosa where the moisture content of the soil is higher. The cessation of lowland forest defines the northern boundary.
Geologically the sub-district falls into three divisions. We are indebted to Dr. F. J. Turner, of Otago University, for the following particulars:—
(1) The western portion, including the high hill-country, underlain by quartzo-feldspathic and mica schists of the Maniototo series. (2) The coastal portion—roughly that lying east of the Waikouaiti River, Silverstream and Lower Taieri River—mantled by a thick cover of marine quartz sandstones, greensands, mudstones, and calcareous sandstones of Upper Cretaceous and Tertiary age, or as in the Taieri Plain, by Pleistocene and Recent stream-gravels. (3) An irregular portion, centred on the town of Port Chalmers and occupying approximately 13,000 hectares, covered by a varied series of volcanic rocks (basalts, trachybasalts, trachytes and phonolites).
Along the coast-line precipitous projecting headlands enclose stretches of sandy beach backed by sand-dunes, or by rock, eroded clay or cliffs of sandstone. The set of the ocean current is from the south, and river and stream outlets are diverted in dune areas to the protected northern sides of the headlands. At Hoopers Inlet, Papanui, Purakanui, Waitati and Waikouaiti, tidal inlets spread over flats of considerable extent. Taieri River, Brighton Creek, Kai-korai Stream and Waikouaiti River are tidal for some distance inland. In the southern portion, rounded hills—intersected by the lower Taieri Gorge, and terminating on their highest point at Saddle
Hill (477 m.)—lie between the sea and Taieri Plain. West of this plain are Mt. Maungatua and lower hummocky hills rising to the western boundary. The northern portion is everywhere hilly with ridges trending in a south-westerly—north-easterly direction; intervening spurs form basins, as at Dunedin, Waitati and Waikouaiti, open to the sea and sheltered from the full violence of the drying westerly and north-westerly gales. Between the main divide and the sea the highest peaks are Silver Peak (760 m.), Mt. Cargill (680 m.), Swampy Hill (666 m.), Mt. Flagstaff (666 m.) and Mt. Watkin (626 m.)
A rain-fall span of 63 to 115 cm. is sufficiently wide to cover the rainfall received on any part of the area with due regard to differences in altitude and latitude. The number of wet days and the mean monthly rainfall are fairly evenly distributed throughout the year, as is shown in the following table kindly provided by the Director of the Meteorological Office.
The prevailing winds are from the south-west and north-east. Westerly and north-westerly winds are not infrequent, seldom of long duration and usually followed by south-westerly “busters.” The trend of the hills leaves the sub-district fully open for the most part to the prevailing moisture-bearing south-west and north-east winds and effectually breaks the full violence of the drying westerly and north-westerly gales. The south-westerly rains reach their average limit at the northern boundary, as the rainfall figures given for Palmerston South, which is outside that boundary, will show. The average number of days when visibility is less than 1 kilometre is recorded as 7.4. Heavy cloud masses, however, frequently obscure the higher slopes, evaporation is checked and the general effect of cloud on the vegetation is greater than fog records would indicate. At low altitudes snowfall occurs on the average some five days in the year. Falls are seldom prolonged and thaw is usually rapid. On higher land, under frost conditions, the heavier coating is slower to move, but there is never a long-continued snow-covering.
Lindsay (1868, p. 28) states that “Evidence already exists of the production of an artificial climate in some parts of Otago, or of the modification of the natural climate, by man's operations, especially as to drainage and timber-felling. These operations tend, in Otago, to render the climate drier and warmer, and such a change has already been experienced in the settled districts around Dunedin, as the result of swamp-draining and timber-clearing.” Whatever the result of man's operations in the future, the dense low fog drifts with drizzling rain—the “Scotch mists” of the pioneers—so frequently experienced during the earlier years of the settlement, have almost entirely disappeared. In that earlier climate the vegetation developed, but present climatic conditions, if long continued, must modify that original character.
|Bushey Park, Palmerston South.|
The vascular flora consists of 560 species (pteridophytes 74, conifers 10, monocotyledons 155, dicotyledons 321), which fall into 78 families and 231 genera. Distinct wild hybrid groups occur in at least 21 genera. Of the 560 species, the following have been hitherto unrecorded for the area:—Acaena hirsutula Bitter. var. (West Harbour, coastal), Acaena sericei-nitens Ckn. (Mt. Maunga-tua), Carex comans Berggr. (Chain Hills), Carex dipsacea Berggr. (Wickliffe Bay), Carex Petriei Cheesem. (Wickliffe Bay), Coprosma Astoni Petrie (Silver Peaks), Coprosma Cheesemanii W. R. Oliv. (Mt. Maungatua), Epilobium erectum Petrie (common), Epilobium pictum Petrie (Woodside), Juncus antarcticus Hook. f. (Mt. Maunga-tua), Juncus luxurians Col. (East Taieri, Evansdale), Juncus maritimus Lam. var. australiensis Buchen. (Evansdale), Juncus pauciflorus R. Br. (Brighton, Whare Flat), Nertera ciliata T. Kirk (Mt. Maungatua), Poa intermedia Buch. (Mt. Flagstaff, Mt. Watkin), Poa Kirkii Buch. (Mt. Maungatua), Poa seticulmis Petrie (Mt. Maungatua, Waitati Hill), Puccinellia Scott-Thomsonii Jansen (Waikouaiti), Schizeilema Haastii Domin. (Mt. Maungatua), Scirpus antarcticus Linn. (Mt. Maungatua), Scirpus basilaris Clarke (Hoopers Inlet), Suttonia nummularia Hook. f. (Mt. Maungatua), Uncinia rubra var. fallax Kukenth (Mt. Flagstaff), Utica linearifolia Ckn. (Mt. Watkin), Wahlenbergia Colensoi N. E. Brown (Waitati).
Just west and north of the boundaries two undescribed shrubs, species of Dracophyllum and Hebe, are common and clearly indicate a change in climatic conditions. The Dracophyllum occurs on cliff edges and rock surfaces at Lee Stream, Deep Stream, in the Taieri Gorge at Sutton and on limestone at the Horse Range. This plant has been included by Oliver (1928, p. 690) in D. rosmarinifolium, but differs from that species in its rock habitat and in its long pendant branches with long narrow leaves. It is a conspicuous plant in its habitat. The Hebe is common near stream edges, occurring frequently with H. salicifolia var. communis. It attains a height of 120 cm., with leaves 2.2 cm. in length and 0.6 cm. in breadth. It is plentiful at Lee Stream, Deep Stream, near creeks on the Rock and Pillar Range and on the banks of the north branch of the Waikouaiti River near Mt. Watkin and at Stoneburn Creek. These two shrubs do not occur in the sub-district and as indicators of a change in climate may be included as boundary-line plants for the area with the following species:—Pimelea pseudo-Lyallii (or a close ally) and Coprosma robusta (Horse Range); Celmisia Hookeri (Horse Range, Shag Point, Stoneburn Creek); Danthonia Raoulii var. rubra (Upper Waipori); Cyathodes Colensoi (western slopes of Mt. Maungatua and Upper Waipori); Senecio southlandicus (Otokia and southwards); Metrosideros lucida (plentiful south of Taieri River). Species belonging to the adjoining botanical districts which occur but sparingly in the sub-district are Weinmannia racemosa, Melicytus lanceolatus and a species of Carmichaelia—probably C. subulate. W. racemosa is known only where mists lie on the eastern slopes of Mt. Cargill, Mt. Mihiwaka and Signal Hill; M. lanceolatus is found
on the higher slopes of Mt. Flagstaff, Mt. Cargill and Mt. Mihiwaka, and in lesser amount at Flagstaff Creek near the Silverstream water-race, at Wakari and at West Taieri. It is extremely localised in its distribution and is nowhere plentiful in the sub-district, but south of the boundary it is a common small tree in the rata-kamahi association, in which its yellow-green leaves and spreading crown are at times a prominent feature. The Carmichaelia occurs on the exposed western sides of the East Taieri hills and is common west and north of the sub-district limits.
Since whaling stations were set up on the shores of Otago more than one hundred years ago and especially since the organised settlement in 1848, cutting, clearing, sawmilling and fire have destroyed the greater part of the primitive vegetation. Much of the land below 365 m. altitude is now cultivated and grazing extends to the higher levels. Portions of the once extensive plant-covering are still preserved in the watersheds of the Waikouaiti River, the Leith, Silverstream and Waitati, at Taieri Mouth, Mt. Maungatua, Silver Peaks and West Harbour, and in smaller associations elsewhere. Probably no plant species has entirely disappeared. Despite repeated burning, tussock-grassland, as in parts of Mt. Flagstaff and Swampy Hill, is not so greatly modified as might have been expected and shrub associations are not completely destroyed. Much of the original subalpine vegetation on the summits of Mt. Maungatua and Swampy Hill still remains. The remnants, however, are little in evidence when viewing the area as a whole and the physiognomy generally is greatly altered.
The bulk of the sub-district carried forest of the two main New Zealand types—rain-forest and southern-beech forest.
B. The Forests.
a. Southern-beech forest. This was confined to comparatively small patches in the sub-district, mostly hemmed in by rain-forest, of which some remain in a much modified state. In the stands still existing there is sparse undergrowth, and the trees are over-mature. While seedlings grow vigorously on the drier ridges and slopes, elsewhere they are suppressed by other vegetation. Characteristic of the shrub-and second-layers are:—Coprosma pseudocuneata, C. rhamnoides, Nothopanax simplex and Griselinia littoralis. The evidence strongly supports the view that these Nothofagus areas are remnants of an earlier more extensive forest now in the last stages of suppression by rain-forest. A detailed study was published by Simpson and Thomson (1928).
Rain-forest proper occurs from sea-level to an altitude of approximately 600 m. and in the primitive vegetation it clothed shaded hill slopes, stream valleys and ravines. The needs of settlement and of agriculture and the demands for grazing lands early
reduced its proportions, but its general character may be determined from a few remaining areas not greatly modified. It occurs in two distinct belts, podocarp-dicotyledonous forest ranging from sea-level to approximately 365 m. altitude and Libocedrus Bidwillii-Podocarpus Hallii forest continuing to the forest limit or lapping over the lower divides and hill-tops, where, as at Mt. Cargill, fog is frequent. The average ceiling height of fog and cloud-drift marks the incoming of L. Bidwillii forest in which the undergrowth is similar to that of the lower forest where Dacrydium cupressinum is conspicuously dominant and in places may form pure stands. Podocarpus totara, sub-dominant, is plentiful and P. ferrugineus and P. spicatus are common components. The trees may be closely placed, the bronzed foliage of the dominant rising plume-like beside the greener podo-carps, but in more open associations the tall trees tower up through a dense roof of second-layer growth. Tree-ferns are much in evidence and Clematis indivisa and Rubus australis scramble through the branches of the highest trees. The second layer is composed mainly of Aristotelia serrata, Carpodetus serratus, Cyathea dealbata, Dicksonia squarrosa, Fuchsia excorticata, Griselinia littoralis, Hemi-telia Smithii (very common), Melicytus ramiflorus, Nothopanax Colensoi, Paratrophis microphylla, Pennantia corymbosa, Pitto-sporum eugenioides, P. tenuifolium, Pseudopanax crassifolium, Suttonia australis and Wintera colorata. Under this cover is a tangled growth of shrubs consisting mainly of Coprosma areolata, C. propinqua, C. rhamnoides, C. rotundifolia, Melicope simplex, Myrtus obcordata, M. pedunculata, Suttonia divaricata, with trailing stems of the lianes Clematis indivisa, Muehlenbeckia australis, Parsonsia capsularis, P. heterophylla, Rhipogonum scandens, and Rubus australis. The common epiphytes are Asplenium flaccidum, Cyclophorus serpens, Earina autumnalis, E. mucronata, Hymeno-phyllum sanguinolentum, Lycopodium Billardieri, Polypodium Billardieri, P. diversifolium, P. grammitidis, Polystichum adianti-forme, Tmesipteris tannensis, and occasionally Griselinia littoralis, Nothopanax Colensoi and N. Edgerleyi. Metrosideros hypericifolia roots along the ground and clings to the trunks in close masses. The common plants on the floor are Astelia nervosa var. sylvestris, Blechnum capense, B. discolor, B. fluviatile, B. lanceolatum, Lepto-pteris hymenophylloides, L. superba, Microlaena avenoides, Nertera dichondraefolia, and Polystichum vestitum. There is a wealth of lichens; mosses and liverworts drape fallen trunks and open spaces and the parasites Loranthus micranthus and Tupeia antarctica are generally in evidence. At stream banks and ravines, the forest edges are filled by tree-ferns, Aristotelia serrata, Carpodetus serratus, Coriaria arborea, Fuchsia excorticata, Griselinia littoralis, Hebe salicifolia var. communis, Melicytus ramiflorus, Nothopanax Colensoi, Polystichum vestitum and Schefflera digitata. There is frequently a close growth of Astelia ncrvosa var. sylvestris or Microlaena avenoides and moist banks are clothed with an abundance of ferns, Epilobium rotundifolium, Gunnera monoica var. albocarpa, Lagenophora pumila, Pratia angulata, Ranunculus hirtus and Stellaria parviflora. At higher altitudes, Olearia arborescens and O. ilicifolia with their hybrids, Coprosma foetidissima, C. rugosa, Drcophyllum longifolium, and Nothopanax simplex are prominent.
Amongst the more conspicuous forest lichens are the following: Catillaria melastigea, Collema leucocarpum, Lobaria adscripta, Myxodictyon chrysostictum, Nephroma zelandicum, Parmelia caperata, P. cetrata, P. enteromorpha, P. pertusa aff., P. subphysodes, P. trichotera, Peltigera dolichorrhiza, Psoroma sphinctrinum, Sphaerophorus australis, S. tener, Sticta chloroleuca, S. coronata, S. crocata, S. filix, S. flavicans, S. fossulata, S. fragillima, S. impressa, S. latifrons, S. psilophylla, S. subcaperata, S. variabilis and Usnea xanthopoga. Regarding the lichen vegetation and flora generally, a striking feature of the area is the presence of a Cladonia Sullivani-C. pycnoclada-Thamnolia vermicularis association on the summit bogs of Mt. Maungatua. Equally noteworthy is the occurrence of Umbilicaria vellea, Usnea acromelana and U. ciliata at the low altitude of 300 m. near Waikouaiti reservoir.
In forest generally mosses and hepatics are much in evidence, and the floor may be covered where shade is deep or mist conditions frequent. The lower branches and trunks of the trees will carry some or other of the following moss species: Acrocladum auriculatum, Camptochaete angustata, C. arbuscula, C. pectonata, Ceratodon purpureus, Cladomnion ericoides, Cryphaea tenella, Dicranoloma Menziesii var. rigidum, D. platycaulon, D. pungens, D. robustum, Echinodium hispidum, Hymenodon piliferus, Hypnum chrysogaster, H. cupressinum, Hypoterygium concinnum, Lembophyllum clandestinum, Leptodon Smithii, Leptostomum inclinans, Leptotheca Gaudichaudii, Lepyrodon australis, Lygodon intermedius, Macromitrium erosulum, M. eucalyptorum, M. Weymouthii, Orthorrbrynchium elegans, Orthotrichum hortense, Plychomnion aciculare, Pteryygophyllum quadrifarium, Rhacromitrium crispulum, Rhizogonium novae-hollandiae, Sematophyllum amoenum, Tinidens tenellus, Weymouthia cochlearifolia, W. mollis and Zoopsis setulosa.
2. Leptospermum ericoides Subassociation.
Leptospermum ericoides has been noted as a tall tree of considerable girth, but particulars of its occurrence in definite areas as a dominant species are not frequently recorded. Hooker (1867, p. 70) described it as a tree from 3 m. to 12 m. in height. Kirk (1889, p. 123) states that “large groves or forest patches consisting entirely of this species were not infrequent in many localities, but the excellence of the timber for firewood and its value in the arts has led to their destruction in the vicinity of settled districts.” Later (1899, p. 158) he gives its height as from 6 m to 18 m. with trunks from 30 to 90 cm. in diameter and Cheeseman (1925, p. 589) gives a similar description. Allan (1926, p. 44) describes a Leptospermum ericoides subassociation at Mt. Peel in which Suttonia australis is plentiful along with Coprosma rhamnoides and C. parviflora. Cockayne (1928, p. 271) in a footnote says that it is usually impossible to state whether such subassociations are primitive or induced. Cranwell and Moore (1935, p. 307) give an interesting account of the occurrence of this species in pure stands on Taranga Island.
L. ericoides still occurs as distinct stands in a few places in the sub-district and it has undoubtedly been destroyed in many localities since early colonization. Mr. P. Thomson, writing to the Otago Daily Times under the pseudonym of “Pakeha,” refers to the occurrence of L. ericoides forest in the area as follows:—(a) Feb. 17, 1865, when he was proceeding up Pine Hill Road: “A considerable portion of the town supply of firewood is brought from this quarter, and we can observe all round the gaps which have been made in the manuka forest, the trees in which have a most peculiar appearance, standing straight up like a wall. The road is lined here and there by large heaps of cut firewood, ready to be carried into town.” (b) Feb. 17, 1865, when crossing over Pine Hill towards North-East Valley: “The gully ended in a large clearing from which all the timber had been removed to town, being principally manuka.” (c) Jan. 29, 1868, when on the north side of the Leith-Waitati Saddle, going towards Blueskin (Waitati): “After traversing a considerable portion of the flat, at a part where another small stream came down from the hill on our right, a sudden change in the timber became apparent. Instead of matai, rimu, kahikatea and other pines, the prevailing tree became the manuka, mixed with red mapau and here and there a moko-moko, grass-tree, hinau-eini,” etc. (d) March 8, 1870, when walking up Kilmog Hill en route to Oamaru: “On the right of the road rises a high sloping hill, covered with timber, amongst which there is some large manuka, a good deal of which is being cut down for fencing,” etc.
Many interesting stands of this subassociation still exist in the watershed of the Silverstream, South Waikouaiti River, Waitati Stream, and their tributaries. On sharp ridges and near upper forest margins, the growth of this species is comparable with that recorded by Allan for Mt. Peel, but in most lower forest situations the trees are even taller and with larger diameters. On a ridge near Wetherstone Creek, a tributary of Waitati Stream, Dacrydium cupressinum is regenerating freely underneath the Leptospermum canopy, the trees varying from 1 m. to 12 m. or more in height, with diameters up to 20 cm. The dominant small tree is Suttonia australis, accompanied by Coprosma linariifolia, Myrtus pedunculata, Notho-panax Edgerleyi, Pittosporum eugenioides, Pseudopanax crassifolium and Wintera colorata. Other trees of the area are present, and the principal shrub is Coprosma rhamnoides; Rubus australis and R. schmidelioides occur, and, as recorded by Cockayne (1908, p. 16), the juvenile growth of R. schmidelioides creeps along the forest floor. In this locality the Leptospermum trees are, by measurement of fallen trees, some 21 m. in height with diameters from 20 to 50 cm. The trees of the second-layer are drawn up to unusual heights and Loranthus micranthus is parasitical on the upper branches, sometimes hanging suspended in considerable masses. Leptospermum ericoides subassociation reaches its southern limit near Dunedin, and the species is rare in the south.
3. Melicytus ramiflorus Subassociation.
Melicytus ramiflorus is an abundant small tree in many situations in the area and frequently forms a forest subassociation. On
rocky slopes in rain-forest areas, as on the middle slopes of Mt. Flag-staff above Ross Creek Reservoir, the trunks are frequently 1 m. in diameter, branching widely from the base, and, from the several trunks thus formed, the tree finally divides at the crown into many small branches carrying foliage near the extremities only. The trees are widely spaced with the crowns meeting to form a continuous canopy some 10 m. above the floor. Large trees of Griselinia littoralis and Fuchsia excorticata are present in quantity, and scattered throughout are Aristotelia serrata, Carpodetus serratus, Nothopanax Colensoi, N. Edgerleyi and Pittosporum eugenioides. The floor is open; the undershrubs are Coprosma areolata, C. rotundifolia and C. rhamnoides and saplings of Nothopanax Colensoi, Pennantia corymbosa, Pittosporum eugenioides, Suttonia australis and Wintera colorata occur in small quantity, but none are of large size and many are dead. Clematis indivisa, Metrosideros hypericifolia, Muehlen-beckia australis, Parsonsia heterophylla, Rhipogonum scandens and Rubus australis occur sparingly.
Hemitelia Smithii is not uncommon, Dicksonia squarrosa occasionally appears and on the floor are young plants of these tree-ferns and usually Polystichum vestitum with Asplenium bulbiferum, Blechnum discolor and Leptopteris hymenophylloides in smaller numbers. Other ferns are Blechnum lanceolatum, Leptolepia novae-zealandiae, Polypodium diversifolium, and Polystichum adiantiforme; occasional epiphytes are Asplenium flaccidum, Cyclophorus serpens, Earina mucronata, Polypodium diversifolium and Tmesipteris tannensis. In moist situations the fern covering is fairly close, but where the floor is dry a few ferns only persist in pockets amongst rocks and the soil has a neutral or even slightly alkaline reaction (Thomson and Simpson, 1936; p. 192).
4. Myoporum laetum Coastal Forest.
The greater part of this once extensive coastal forest has been destroyed and much of that remaining is open to cattle and sheep. Scattered remnants, however, protected from or inaccessible to stock, still remain. The crowns of the trees are bushy and in exposed situations are wind-swept to fantastic shapes. Light is admitted between the crowns, undershrubs are everywhere plentiful and frequently they form almost impenetrable thickets. The composition of the small tree and shrub growth is fairly constant, but the dominants of exposed positions are sub-dominant or sparse in more sheltered places. Coprosma areolata C. crassifolia, Corokia cotone-aster, Helichrysum glomeratum, Hymenanthera crassifolia, Melicope simplex, Myrtus obcordata, Suttonia australis and S. divaricata, wind-shaped, intertwined and densely branched on the leeward side, fill in the outer edges. Other tree and shrub species present are Coprosma propingua, Cordyline australis, Edwardsia microphylla, Griselinia littoralis, Hebe elliptica, H. salicifolia var. communis, Hoheria angustifolia, Melicytus ramiflorus, Pennantia corymbosa, Pittosporum eugenioides, P. tenuifolium, Plagianthus betulinus, Podocarpus totara, Pseudopanax crassifolium and Solanum aviculare.
Angelica geniculata, Clematis indivisa, Muehlenbeckia australis, Par-sonsia heterophylla, Rubus australis and R. cissoides are common climbing components, while Calystegia tuguriorum and Tetragonia trigyna scramble amongst the marginal shrubs. Acaena sanguisorbae A. hirsulata var., Asplenium lucidum var. Lyallii, Halorrhagis erecta and Polypodium diversifolium are frequent ground plants.
Myoporum laetum coastal forest apparently does not occur south of the Taieri River.
c. The Induced Communities. The few published accounts of induced plant-communities in New Zealand indicate that these may be characteristic of the districts in which they occur. For the sub-district the following may be noted. In the rain-forest remnant known as the “town-belt” at Dunedin, Melicytus ramiflorus is displacing Fuchsia excorticata over considerable areas. Extensive thickets of Hypericium androsaemum have developed on many areas where forest has been felled. To a less extent communities of Leycesteria formosa, Ulex europaeus and Cytisns scoparius also occur. Of considerable interest is the fact that some of these communities are in turn succumbing to indigenous species, notably Leptospermum scoparium, L. ericoides, Hebe salicifolia, Pittosporum tenuifolium, P. eugenioides, Suttonia australis and species of Coprosma. So, too, on Flagstaff Hill, Phormium tenax has assumed dominance over a mixed community of exotics and indigenes, and Aciphylla Colensoi tends to do the like (Cockayne, Simpson and Thomson, 1932).
Leptospermum ericoides and L. scoparium and the exotic Ulex europaeus dominate neglected areas and are particularly aggressive following the burning of shrub communities and grassland. In the tension belt to the north and west they persist to some extent in sheltered gullies but do not spread and rapidly give place to tussock-grassland as conditions become severe.
We are indebted to Dr H. H. Allan, Plant Research Bureau, Wellington, for his interest at all times and to Mr. G. O. K. Sains-bury, Wairoa, for identification of mosses.
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