On the Occurrence of the Silver Southern-Beech (Nothofagus Menziesii) in the Neighbourhood of Dunedin.

Transactions and Proceedings of the Royal Society of New Zealand, Volume 59, 1928, Page 326

On the Occurrence of the Silver Southern-Beech (Nothofagus Menziesii) in the Neighbourhood of Dunedin. By G. Simpson and J. Scott Thomson. [Read before the Otago Institute, 9th August, 1927; received by the Editor, 16th May, 1928; issued separately. 17th August, 1928.] Plates 48-51. 1. General. A question of considerable moment in plant-geography is the occurrence of species which, though common enough elsewhere, are most limited in numbers in some particular locality. The forest in the neighbourhood of Dunedin (South Otago Botanical District) supplies several interesting problems of this class, one of which, to be considered here, deals with that fundamental matter concerning New Zealand forests in general—the relation between subtropical forest composed of broad-leaved dictotylous trees and podocarps, and subantarctic forest where one or more species of Nothofagus dominate. As will he seen further on, there are in the Dunedin area some twelve pieces of Nothofagus Menziesii forest, mostly quite small, indeed, out of all proportion to the original forest-covering of the area, and the question at once arises, “Is the silver southern-beech (N. Menziesii) a new arrival, or is it merely a survivor of a former host?” To attempt an answer to this important question is the main object of this paper. Secondary to this is the presentation of various matters referring to these Dunedin Nothofagus communities, and especially the placing on record of their distribution and composition. Finally, in the light of our new knowledge concerning Nothofagus in the Dunedin area, we are in a position to examine critically L. Cockayne's bold theory (1921: 322-23 and 1926: 39) regarding the relation between the two great classes of New Zealand rain-forest—the subtropical and the subantarctic. The said theory is based on the present latitudinal, altitudinal, and ecological distribution of Nothofagus forest in New Zealand, and it suggests that at one time the Nothofagus forest was the chief tree-community; but that it has been gradually replaced by the subtropical forest of Malayan origin, the Nothofagi having been slowly suppressed where the soil is comparatively fertile, and that the Nothofagus forests could only remain intact on the poorer ground or at higher altitudes where the climate is hostile to a majority of the subtropical forest species. At the time of the settlement of Otago there can have been at no place near Dunedin any considerable area of Nothofagus. The whole of the slopes on both sides of the harbour were covered with dense subtropical rain-forest*Hereafter cited as rain-forest, but it must be remembered that rain-forest in New Zealand includes both the subtropical and subantarctic forests.; that on the west stretching from

the water's edge to the high ridges of Mount Cargill and Flagstaff Hill and extending northwards to beyond the Waikouaiti River. With few breaks this forest covered the hills to the west of Dunedin and along the slopes north and west of the Taieri Plain. The gullies to the east of the plain were also thickly forest-clad, and the reserve at Taieri Mouth gives evidence of the once splendid rain-forest which at that time clothed the hills along the coast-line. In this extensive area Nothofagus Menziesii has previously been reported from the following places only, the authority for each locality being given in parenthesis:—(1) Ravensbourne, Dunedin Waterworks and West Taieri†After West Taieri comes the convenient “etc.,” which not merely tells nothing, but is misleading, since it suggests that other areas of Nothofagus Menziesii were well known, and that the species was fairly common. (Dunedin Field Club, 1916: 21); (2) near Leith-Waitati Road (Watt, 1924: 674-75); (3) Mount Cargill, above Main North Road (Petrie, 1896: 573). Exhaustive enquiries among bushmen and others brought to light a few more localities, and field-work has augmented the list, so that to the above we have been able to add the following:—(4) Pigeon Plat (a few trees only), (5) Fergusson Creek (a stand of considerable area in higher forest with remnants also near Leith-Waitati Road, and on south side of Double Hill), (6) Bethune Gully (a mature stand in the midst of rain-forest), (7) Flagstaff Creek (isolated trees along the creek bed), (8) Boulder Hill (stand on the south side of this hill), (9) Traquair Burn, Outram Glen (trees along creek bed, evidently a remnant), (10) Taieri Mouth (remnant of once large stand which has been cut down and milled), (11) Source of south branch of Waikouaiti River, (12) Silver Peaks (an extensive area of pure southern-beech forest). No doubt other isolated trees or groups of trees are still unrecorded, and at many places they have been cut down. Several such spots have been pointed out to us by settlers,*From experience we find that records of Nothofagus by settlers must be received with great caution, since besides species of Nothofagus many other trees are “birch”—as they call such—to them. but as all evidence of their existence is now destroyed their occurrence at these points cannot be accepted for the purposes of this paper. The above newly-recorded areas were carefully examined, and in several of them the trees were counted, the diameters of their trunks measured, the occurrence of seedlings and saplings noted, and the age of saplings determined by counting their annual rings. Notes were also taken of the composition of the surrounding forest, of the undergrowth immediately under the Nothofagus trees and also that of the forest floor-covering, especially with regard to its light-reducing properties. 2. The Areas Known Prior to the Date of This Paper. It seems best to deal with each reported area in the order they have been recorded; they are as follows:— (a) At Ravensbourne and the Dunedin Waterworks (Ross Creek) no traces can now be found, and the trees have evidently been destroyed.

Map Showing Distribution of Nothofagus Menziesii

(b) That part of the Taieri Plain known as “West Taieri” had a considerable covering of Nothofagus which extended from Woodside Glen to Waipori, and included the slopes of Maungatua. Much of this area has been cut over in earlier years and fires have taken their toll, the present forest being mainly that reserved in the Woodside Domain and in the Dunedin City Corporation's Reserve at Waipori. At Woodside N. Menziesvi occurs along the bed of the stream at about the level of the plain (some 45m. altitude) and runs up the sharper ridges to approximately 200m. At that height it forms a belt extending right along the hillsides above the rain-forest and giving out, at about 600m. altitude, in the valleys dividing up the tussock-dad slopes of Maungatua. Above this belt a thicket of Leptospermum scoparium runs up to the scrub-line. Along the edges of the creeks and throughout the rain-forest below the line of the Nothofagus forest the following species occur*This list, with, few exceptions or additions may, to save repetition, be taken as typical for the forest vegetation surrounding and in contact with most of the Nothofagus stands listed.:— Alsophila Colensoi, Aristotelia serrata, Asplenium bulbiferum, A. flaccidum, Astelia nervosa var. sylvestris, Blechnum discolor, B. fluviatile, B. lanceolatum, B. Patersoni var. elongatum, B. procerum, Carpodetus serratus, Cassinia Vauvilliersii, Clematis indivisa, Coprosma areolata, C. crassifolia, C. foetidissima, C. linariifolia, C. lucida, C. parviflora, C. propinqua, C. rhamnoides, C. rotundifolia, Coriaria arborea, Cyathea dealbata, Cyclophorus serpens, Dacrydium cupressinum, Dicksonia squarrosa, Fuchsia excorticata, Griselinia littoralis, Hebe salicifolia var. communis, Hemitelia Smithii, Leptopteris hymenophylloides, L. superba, Leptospermum ericoides, L. scoparium, Loranthus micranthus, Melicytus ramiflorus, Metrosideros hyperidfolia, Muehlenbeckia australis, Myrtus obcordata, M. pedunculata, Nothopanax Colensoi, N. Edgerleyi, Olearia arborescens, Parsonsia heterophylla, Pennantia corymbosa, Podocarpus ferrugineus, P. spicatus, P. Hallii, P. totara, Polypodium Billardieri, P. diversifolium, P. grammitidis, Polystichum Richardi, P. vestitum, Pittosporum eugenioides, P. tenuifolium, Pseudopanax crassifolium var. unifoliolatum, Rhipogonum scandens, Rubus australis var. glaber, R. cissoides, Suttonia australis, S. divaricata, Tupeia antarctica, Wintera colorata. In this particular locality Edwardsia microphylla also occurs abundantly. The parasitic Elytranthe Colensoi with its beautiful red blossoms and large green leaves covering the branches of the southern-beech is a glorious sight in December and January. Very little undergrowth occurs in the greater part of the southern-beech forest, but in places opened to the light by falling trees or by the axe, seedling trees and saplings occur in profusion. (Fig. 1.) In the vicinity of streams the forest-floor is covered by various ferns and brypophytes, trees of the undergrowth and shrubs spring up in every open space and, in spots that have been cleared, become so dense that progress through them is almost impossible. Nothofagus Menziesii as a fully developed forest-tree here holds its own against all-comers, but its seedlings are quickly suppressed by the aggressive subtropical rain-forest trees and shrubs. The southern-beech seedlings grow vigorously on the drier ridges and slopes, but

cannot compete in the moist and shaded places with the larger-leaved, fast-growing shrubs and second-layer trees. The grassland and subalpine scrub above the upper margin of the forest have been repeatedly burned, and fire has cut into the standing trees. The incoming vegetation, consists mainly of Aristotelia serrata, Blechnum discolor, B. procerum, Carpodetus serratus, Dracophyllum, longifolium, Griselinia littoralis, Hebe salicifolia var. communis, Nothopanax Colensoi, N. simplex, Pittosporum eugenioides, P. tenuifolium, and Rubus australis var. glaber, while Cassinia Vauvilliersii and Hebe buxifolia are dominant in the scrubland together with occasional plants of Aciphylla Scott-Thomsonii, and A. Colensoi. Seedling and sapling southern-beeches occur usually on rising- ground where the soil is shallow or where the fern is open. Leptosperum scoparium sometimes forms dense thickets which contain seedling plants of Carpodetus serratus, Clematis indivisa, Coprosma rhamnoides, Griselinia littoralis, Nothopanax Colensoi, N. simplex, Parsonsia heterophylla, Pseudopanax crassifolium var. unifoliolatum, Suttonia australis and occasional plants of Asplenium bulbiferum, Astelia nervosa var. sylvestris, Blechnum discolor, B. fluviatile, and B. procerum. At Waipori the southern-beech forest again follows the stream and spreads along the higher ground while much the same conditions govern forest-rejuvenation. Seedlings are plentiful on the broken debris of the higher slopes, but the trees of the rain-forest close up all open spaces on shaded or lower levels. Wherever fire has destroyed the original plant-covering, a dense scrub of Leptospermum scoparium and L. ericoides covers the damaged areas. Corokia Coton-easter, Edwardsia microphylla, and Helichrysum glomeratum growing on the sunnier side of the gorge, are indicators of fairly dry and free soil. Here, as at Woodside, in midsummer Elytranthe Colensoi beautifies the otherwise sombre forest. In places along the sides of the road seedling southern-beeches are quite common but never in competition with the usual second-growth vegetation. The leaves of the southern-beech in this locality are attacked by a species of Eriophyes. (c) The Waitati locality. A few trees only occur at this spot (approx. 150m. altitude) which are evidently a remnant of a stand long since milled. (d) The Mount Cargill stand (altitude 425m.). L. Cockayne rightly supposes (1926: 30) that these trees had “probably gone long ago.” The whole of the old trees were milled, and only the old stumps remain, but from these and from the stumps of some second-growth trees, not long ago destroyed, and from an examination of the young trees still left standing, a conclusion as to the extent of the stand and the rate of growth of saplings was obtained. Many of the stumps are very large and the following measurements, taken June 5th, 1926, show that the original trees were of considerable age. Original large trees (14 in number) now cut down and burnt, leaving burnt stumps only from which the following mean diameters were taken: (Mean diameters), 68cm., 73cm., 86cm., 96cm., 96cm.,

116cm., 116cm., 116cm., 122cm., 122cm., 137cm., 137cm., 167cm., 167cm. Other stumps still remain but these were too far decayed to afford reliable details. Mean diameters of trees (second growth) recently cut down (34 in number) : (Mean diameters) 5cm., 8.3cm., 8.3cm., 8.9cm., 9.5 cm., 10.2cm., 10.2cm., 10.2cm., 10.2cm., 10.8cm., 10.8cm., 10.8cm., 10.8cm., 10.8cm., 10.8cm., 11.4cm., 11.4cm., 11.4cm., 11.4cm., 12.1cm., 12.1cm., 12.1cm., 12.7cm., 14cm., 14.6cm., 14.6cm., 15.2cm., 17.1cm., 17.1cm., 17.1 cm., 17.8 cm., 19.7 cm., 24.1 cm., 24.1 cm. Some sixty southern-beech saplings with mean diameters ranging from 2.5cm. to 32cm. still stand in small groups or as individuals usually with a protecting growth of Fuchsia excorticata, species of Coprosma and Rubus australis var. glaber, but elsewhere the ground is cleared for grazing and seedling plants are absent. The forest surounding this group on the north and west is composed mainly of Libocedrus Bidwillii (dominant at this level and forming an almost pure association as the ground rises), Podocarpus ferrugineus, P. Hallii, P. totara, Dacrydium cupressinum, and the usual trees and shrubs of the undergrowth; Phyllocladus alpinus is present also Dracophyllum longifolium which here attains a large size, some specimens measured being over 25cm. diam. Every indication points to the whole forest being of considerable age, and the Nothofagus stand of very limited extent in recent times. 3. An Account of the Nothofagus Areas not Previously Recorded. (a) Pigeon Flat (245m. altitude). At this spot only a few trees remain, and little evidence can be obtained to determine the extent of the original stand. The surrounding rain-forest has been cut over time and again, and the largest N. Menziesii (106cm. diam.) stands at the corner of a paddock with a wire fencing fastened round its trunk. The fact of Nothofagus occurring at this point, however, is important. (b) Fergusson Creek. Close to where the creek crosses the Leith-Waitati Road, and on both slopes of the gully, N. Menziesii occurred in stands of considerable size and tramways were run in many years ago to bring out both the southern-beech and the surrounding forest-trees. Young trees of N. Menziesii came up in several places and have reached maturity, but never as a close association. Cattle followed the bushmen, and second-layer trees and ferns crept in, filling up the steeper ground. At present, cattle-tracks lead through this to the flatter land above. Nearer the source of the creek at an altitude of approx. 300m. the forest is dense and, though similar in composition to the forests already mentioned, is much wetter, containing as it does many small streams and hollows which drain Swampy Hill. Species of Hymenophyllum grow luxuriantly and bryophytes abound. The lichen vegetation is well developed, and the whole area is exposed to heavy coastal mists. Almost pure stands of Dacrydium cupressinum are common, Leptospermum scoparium following where the forest has been cleared. Here a Nothofagus Menziesii stand occupies an area of about a hectare in extent, closely hemmed in by the rain-forest, and the whole area is densely covered

with second-layer trees and shrubs of which Coprosma foetidissima is dominant. The humus covering of the ground is deep and overlaid with liverworts and mosses; young plants of Nothofagus are found in a few places, but generally the undergrowth is exceptionally dense; tree-ferns and Blechnum discolor cover up all openings in the almost unbroken tangle and Leptopteris superba is plentiful. Individual Nothofagus trees occur sometimes at considerable distances from one another, but around these individuals, and in the intervening spaces, their seedlings have not developed. Further north, towards Double Hill (altitude about 300m.) a patch of sapling N. Menziesii is growing amongst Leptospermum scrub, probably seedlings from trees now destroyed. (c) Bethune Gully. This area of Nothofagus is of particular interest in that it stands as an unbroken colony in the midst of a heavy association of rain-forest which commences at an altitude of about 100m. and extends unbroken to near the summit of Mount Cargill. A Dacrydium cupressinum-Podocarpus ferrugineus association runs up to approximately 450m. (the level of the Nothofagus); Podocarpus Hallii comes in as the ground rises and, above the Nothofagus (Fig. 2), Libocedrus Bidwillii is dominant; Dacrydium biforme is present, trees of the undergrowth, mainly species of Nothopanax and Coprosma occur throughout and tree-ferns are common in the lower forest. Mosses, lichens and filmy ferns clothe the fallen timber and lower trunks of the larger forest trees and Blechnum discolor is abundant (Fig. 3) everywhere along with Nertera dichondraefolia. Leptopteris superba and L. hymenophylloides are common while Polystichum vestitum occurs in the more open spaces. The forest on the upper ridges has been burnt, leaving skeleton trees and fallen stumps, and through part of this the usual trees of the second-layer have sprung up. The higher ground is fenced for cattle and Cassinia Vauvilliersii is the common shrub. Table A. Number of N. Menziesii Present. with Mean Diametres Ranging From Approx. Percentage of Total Number of Nothofagi Present. 4 0.5cm.— 2.5cm. 2.4% 6 Above 2.5cm.— 5 cm. 3.6% 14 " 5 cm.— 7.5cm. 8.4% 17 " 7.5cm—10 cm. 10.2% 17 " 10 cm.—15 cm. 10.2% 13 " 15 cm.—23 cm. 7.8% 14 " 23 cm.—30 cm. 8.4% 21 " 30 cm.—45 cm. 12.6% 15 " 45 cm.—60 cm. 9.0% 15 " 60 cm.—76 cm. 9.0% 13 " 76 cm.—91 cm. 7.8% 7 " 91 cm.—106 cm. 4.2% 5 " 106 cm.—122 cm. 3.0% 3 " 122 cm.—137 cm. 1.8% 3 " 137 cm.—152 cm. 1.8% 1 " 167 cm.-182 cm. 0.6% Total: 168 in the group.

Fig. 1—Rejuvenation of Nothofagus Menziesii on ridge at Woodside where large trees have been felled. Fig. 2.—Nothofagus Menziesii in Bethune Gully, 6.7 metres in circum. At 0.6 metres from ground and 5.3 metres at 1.8 metres from ground. Buttresses at base of trunk.

Fig. 3.—Dense growth of Blechnum discolor in the Nothofagus community at Bethune Gully which forbids development of seedlings of any kind. Fig. 4.—General view of the Silver Peaks Nothofagus forest, one sq. kilometre in extent.

Fig. 5.—Nothofagus Menziesii saplings within the Silver Peaks forest. Fig. 8.—Community of Phomium Colensoi and certain shrubs at head of Silver Peaks forest.

Fig. 7.—Rejuvenation of Silver Peaks forest where margin of forest had been broken.

Table A seeks to give an accurate survey of all the Nothofagi present *All seedlings 30cm. or more in height are included in the list, but the diameters of the smaller plants give no indication of their age, as will be shown in Table C. in this isolated colony, together with their diameters. The light-intensity in the above colony was 1/55th of that outside the forest. Many of the southern-beech trees are clad to their tops with Cyclophorus serpens, and everywhere lichens reach high up into the upper branches; Asplenium flaccidum is a common epiphyte. The lichens † For the identification of these we are indebvted to Dr. G. Einer Du Rietz, of Upsala, who accompanied us on a visit to the forest. He also kindly identified specimens from Silver Peaks forest. present were a species of Ochrolechia, several species of Pannaria, Parmelia subphysodes, Parmeli (species not identified), Pseudocyphellaria Colensoi, P. chlorolerica, P. episticta, P. subvariabilis, Sphaerophorus melanocarpus, Sphaerophorus tener, Sphaerophorus (sp.), Sticta latifrons, S. sinuosa, and a species of Usnea. Seedling plants a few centimetres in height are common growing on moss on fallen tree-trunks, and a few have germinated on the forest-floor, but seedlings with a height of 25cm. or more are practically non-existent. Saplings with small diameters are unhealthy, often decayed at their tops, and seem unable to continue for long the struggle for existence with the surrounding vegetation. A feature of this colony is the unusual lateral spread of some of the very old trees, which denotes a much more open association than is the case to-day. In a few places light has been let in by fallen trees, and along a fence-line the undergrowth has been opened up, but the close ground-covering of Blechnum discolor (Fig. 3), and the fast-growing species of Nothopanax and Coprosma quickly discount the advantage given by the incoming light. The main factors prohibiting germination and rejuvenation of the Nothofagus in this locality seem to be, (a) lack of light caused by density of foliage of the parent trees and second-layer growth, (b) depth of raw undecomposed humus, (c) in places the close floor-covering of Blechnum discolor, Nertera dichondraefolia, and bryophytes. (d) Flagstaff Creek. The few trees occurring here (altitude about 150m.) may be a remnant of a more extensive group destroyed in recent years; but the fact of their being close to a much-used road to North Taieri, and that no record has been made of their presence, would appear to leave little doubt that the group has not been extensive since the district was first settled. Only one large tree exists, now much decayed and broken. All stand on the edge of the creek, and are the only forest trees present. Ulex europaeus and Cytisus scoparius hem in the stream, while Griselinia littoralis, Leptospermum ericoides, L. scoparium, Melicytus lanceolatus, Pseudopanax crassifolium var. unifoliolatum, and other small trees also occur. During the last few years afforestation has been carried out by the Dunedin City Reserves Department and is rapidly covering up the grassland. The smaller southern-beech trees probably originated as seedlings from the large specimen, the seeds being carried the short distance from the parent plant by floodwaters, or even by wind.

(e) Boulder Hill. This group, about half a hectare in extent, and at an altitude of about 210 metres, is confined to the shaded side of a ravine on the south side of Boulder Hill. An almost continuous belt of Leptospermum scoparium of great density forms the outside margin of the forest and encloses an association of the following plants:—Aristotelia serrata, Carpodetus serratus, Coprosma linariifolia, Fuchsia excorticata, Griselinia littoralis, Leptospermum ericoides, Nothopanax Colensoi, N. simplex, Pseudopanax crassifolium var. unifoliolatum, and Suttonia australis. The interior of the stand is fairly open, and most of the above-mentioned plants enter into it, while Blechnum discolor and B. procerum occur sparsely on the forest-floor. Polypodium diversifolium and Asplenium flaccidum are present on the tree-trunks, but species of Hymenophyllum are absent, the habitat being comparatively dry. Libocedrus Bidwillii is represented by one tree only (20cm. diam.) growing in the midst of the southern-beeches. The larger trees of the group form a rough circle enclosing those of smaller diameters, and no seedlings or saplings occur on the outer margin of the area. Table B gives the number of Nothofagi* All seedlings 30cm. or more in height are included in the list. present, together with their respective diameters. Table B. Number of N. Menziesii present. With Mean Diameters Ranging From Approx. percentage of Total Number of Nothofagi present. 13 0.5cm.—2.5cm. 9.5% 34 Above 2.5cm.—5cm. 24.8% 23 " 5cm.—7.5cm. 16.8% 9 " 7.5cm.—10cm. 6.6% 24 " 10cm.—15cm. 17.5% 16 " 15cm.—23cm. 11.7% 10 " 23cm.—30cm. 7.3% 6 " 30cm.—45cm. 4.4% 1 " 45cm.—60cm. 0.7% 1 " 122cm.—137cm. 0.7% Total: 137 in the group. The light-intensity in the above group was 1/25th of that outside the forest. (f) Traquair Burn. This stand of Nothofagus (altitude 60cm.) follows the creek for a short distance, and is composed entirely of small trees. On both sides the banks rise quickly, and in places precipitately, to hillsides covered with Leptospermum scoparium and in the larger growth of this the following are abundant:—Aristotelia serrata, Clematis indivisa, Coprosma crassifolia, C. linariifolia, C. parviflora, C. rotundifolia, Coriaria arborea, Corokia Cotoneaster, Fuchsia excorticata, Griselinia littoralis, Helichrysum glomeratum, Melicytus ramiflorus, Pittosporum eugenioides, P. tenuifolium, Pseudopanax crassifolium var. unifoliolatum, Rubus australis var. glaber, and R. cissoides. The stream rises quickly up beyond this through ground densely clad with small trees, and present as groundplants are Asplenium bulbiferum, A. flabellifolium, A. flaccidum,

Blechnum discolor, Cyclophorus serpens, Pellaea rotundifolia, Polypodium diversifolium, and Polystichum vestitum. The soil is very free and dry, no tall trees of rain-forest are present, and as the whole area has been repeatedly burnt, particulars of its original covering cannot now be obtained. Leycesteria formosa, Cytisus scoparius, Ulex europaeus, and introduced grasses now occupy much of the burnt-over area. (g) Taieri Mouth. An examination of the remnant of forest now reserved at this seaside resort indicates the type of vegetation that spread into all the gullies and over much of the hillsides along the coast in the locality. Dacrydium cupressinum is dominant, while Podocarpus ferrugineus, P. spicatus, and P. totara are abundant, and seedlings of all these are plentiful. Leptospermum scoparium covers some of the drier ridges and Fuchsia excorticata, Griselinia littoralis, Leptospermum ericoides, Melicytus ramiflorus, Nothopanax Colensoi, N. Edgerleyi, N. simplex, Pittosporum eugenioides, P. tenuifolium, Pseudopanax crassifolium var. unifoliolatum, Suttonia australis, and Wintera colorata are the smaller trees present. Some parts of the forest near stream-beds are extremely shady and ferns grow profusely. Generally the association is open and easily traversed, but species of Coprosma along with Leptospermum scoparium form tangled masses on the ridges. The road to Waihola from Taieri Mouth runs along a ridge, and on this road about one kilometre from the Mouth, and at an altitude of about 60m., Nothofagus trees were, many years ago, felled and drawn down the ridge to a saw-mill near the beach. Young trees not suitable for milling were left and many seedlings came up. Since that time, the secondlayer trees and srubs with Rubus australis var. glaber and Muehlenbeckia australis have grown over the cleared area and, as the reserve at this point is not well protected, cattle-tracks are plentiful throughout. N. Menziesii was found by us at this point, and the forest on both sides of the ridge is an association of Dacrydium cupressinum, Podocarpus ferrugineus, and P. spicatus, Nothofagus evidently occupying the ridge only. At several places further south other scattered trees were located. (h) Source of the south branch of the Waikouaiti River. This locality for Nothofagus was located only, and time as yet has not allowed a proper examination to be made of either the forest or of the occurrence of seedlings. Without doubt further groups still occur in this heavily-wooded area and in the vicinity of Mount Misery, one group being located at Horseshoe Bend, Waikouaiti River. (i) Silver Peaks. This interesting stand (Fig. 4), over one square kilometre in extent, situated at the source of the south branch of Christmas Creek, is unbroken. It consists of pure Nothofagus Menziesii forest and is completely isolated from the usual rainforest. The position is exposed to the full blast of southerly winds, and is within the area covered by driving mist during cloudy or wintry weather. Lichens make an almost complete covering of trunks and branches, a species of Usnea being the most noticeable; indeed the general appearance of the forest could best be compared with that of Nothofagus growing on shaded hill-slopes in the Fiord Botanical District. Amongst other lichens present are species of

Parmelia, Pseudocyphellaria Billardieri, Sphaerophorus melanocarpus, and S. tener. Trees of all sizes are present, some of them very large, the lower portions of their trunks being draped with Polypodium diversifolium. Asplenium flaccidum is a common epiphyte. The trees of the undergrowth are principally Coprosma pseudocuneata, C. rhamnoides, and Nothopanax simplex. Some large trees of Griselinia littoralis and Libocedrus Bidwillii are present. In places there is a good deal of rejuvenation within the forest (Fig. 5). A peculiar feature of this stand is that the specimens of Libocedrus are widely spaced and drawn up by the height of the Nothofagus to beyond their usual stature, and the majority are dying out; no seedling plants of Libocedrus were seen. In the forest heavy lateral growth of N. Menziesii is not very evident, most of the trees running up to their full height with but little branching, and the crowns are sparse. The upper margin of the Nothofagus association ascends to approximately 600m., and the scrub-vegetation above is chiefly Cassinia Vauvilliersii, Coprosma parviflora, Danthonia flavescens, Dracophyllum longifolium, D. uniflorum, Nothopanax Colensoi, Olearia arborescens, and Phormium Colensoi (Fig. 6). On the west Danthonia flavescens meets the edge, and some higher exposed ridges run down in tongues, in part dividing the forest. On the east the ground is more shaded and moist, Blechnum procerum, Cassinia Vauvilliersii, Coriaria lurida, and Nothopanax Colensoi being the dominant plants. The mountain carries sheep, and burning is evident, in many places extending to the forest; seedlings and sapling trees are plentiful wherever the margin is broken (Fig. 7). The forest-floor is much broken up by wild pigs, and the fern-covering is usually Polystichum vestitum, though Blechnum discolor occupies occasional openings. The greatest opponent to the forest growth is the fungus Cyttaria Gunnii which grows in grape-like colonies completely surrounding the stems of the saplings and on the branches of more developed trees causing large galls to form, many of them 30cm. or more in diam. In young trees the growth is altogether retarded, and everywhere throughout this forest branches are seen terminating abruptly at the gall, the upper part withering and falling away. In other cases the branch survives and is repeatedly attacked, galls often appearing at intervals along the branch. 4. Effect of light. A comparison of the differing rates of growth of Nothofagus under differing light-conditions is important. The specimens, measurements of which are given in Table C, were taken at random from the interior of the Nothofagus communities in the localities mentioned, and the annual rings were counted along a smooth bevelled section. The light-intensity in each locality was obtained by taking an average of six readings with a Wynne's exposure meter and comparing that average with an average of the light outside the forest.

Table C. Bethune Gully. Light Intensity 1/55th. Age. Height. Diam. Average Increase in Diam. per Year. Years. Metres. Centimetres. Centimetres. 22 2.43 1.5 0.0682 52 2.59 2.9 0.0558 70 6.09 3.8 0.0543 55 6.09 4.2 0.0764 71 5.48 4.8 0.0676 75 4.87 5.1 0.0680 85 5.18 6.4 0.0753 101 6.09 7.0 0.0693 Average increase in diameters per year = 0.0668 centimetres. Boulder Hill. Light Intensity 1/25th. Age. Height. Diam. Average Increase in Diam. Per Year. Years. Metres. Centimetres. Centimetres. 26 2.43 1.6 0.0615 31 2.59 2.5 0.0806 57 3.65 2.7 0.0474 44 4.87 3.4 0.0773 55 4.57 3.8 0.0691 50 5.48 3.8 0.0760 82 6.09 6.4. 0.0780 89 6.40 7.3 0.0820 Average increase in diameters per year = 0.0715 centimetres. Silver Peaks. Light Intensity 1/13th. Age. Height Diam. Average Increase in Diam. Per Year. Years. Metres. Centimetres. Centimetres. 24 2.43 1.8 0.0750 26 4.57 2.5 0.0961 39 4.87 3.7 0.0948 50 5.48 3.7 0.0740 46 6.09 3.8 0.0826 50 5.79 4.8 0.0960 69 5.18 6.7 0.0971 51 6.70 7.3 0.1431 Average increase in diameters per year = 0.0948 centimetres. The above figures clearly show the effect of the light-intensity on the growth of the saplings. The Bethune Gully habitat with a light-intensity of 1/55th produced saplings showing an average increase in diameters of only 0.0668 centimetres per year. The Boulder Hill habitat with a light-intensity of 1/25th produced saplings showing an average increase in diameters of 0:0715 centimetres per year, while the comparatively open forest at Silver Peaks

with a light-intensity of 1/13th produced saplings with a more rapid rate of growth still (0.0948cm.). Table D will serve to illustrate the rate of development under more open conditions. The specimens tabulated were taken from the remnant left at Mount Cargill (No. 3 habitat), and their mean diameters across the first 15 annual rings were taken, also the mean diameters of trees when felled. It is evident that during the first 15 years they were living under more adverse light-conditions than those experienced during the latter half of their existence. Table D. Specimens taken from Mount Cargill (No. 3 habitat). Specimen. Mean Diam. at 15 Years. Mean Diam. and age when felled. Average Increase in Diam. Per Year. No. 1 1.9cm. 17.8cm. at 30 yrs. 0.5933cm. No. 2 2.5cm. 14.6cm. at 32 yrs. 0.4562cm. No. 3 3.8cm. 12.1cm. at 30 yrs. 0.4033cm. No. 4 3.8cm. 15.2cm. at 31 yrs. 0.4903cm. No. 5 3.8cm. 17.1cm. at 30 yrs. 0.5700cm. No. 6 5.0cm. 14.0cm. at 32 yrs. 0.4375cm. Average increase in diameters per year = 0.4917 centimetres. The intensity of the light must also, amongst other factors, influence the germination of seedlings. The Bethune Gully and Boulder Hill communities were particularly studied in this regard as they afforded an excellent opportunity for statistical analysis, both being totally surrounded by other forest, practically untouched by man or stock, and of a size that could be accurately surveyed. A study of the figures concerning these groups—Tables A and B—will show that in the Bethune Gully group with a light-intensity of 1/55th of that outside, seedlings and saplings with diameters ranging from 0.5cm. —2.5cm. were present only to the extent of 2½% of the total plants, while in the Boulder Hill stand, with a light intensity of 1/25th of that outside, the proportion present was about 10%. It is also interesting to note that in the Silver Peaks forest, where the light intensity is 1/13th of that outside, seedlings and saplings occur freely. In this connection it must be borne in mind that the diameters and heights of many of the saplings are quite disproportionate to their age (see Table C). 5. Differences between nothofagus forest and subtropical rain-forest. In order to arrive at some logical conclusion on the occurrence of Nothofagus in all these widely-separated localities, the differences must first of all be noted between these southern-beech groups and the subtropical rain-forest which surrounds them. The Nothofagus communities are usually composed of tall trees with sparse crowns, and they are generally open enough to make

progress through them a comparatively easy matter. This is in marked contrast to conditions prevailing in rain-forest, progress through which is often well-nigh impossible unless the slasher or axe is brought into play. In southern-beech forest tree-ferns are frequently absent or few in number, and species of Coprosma and Nothopanax are as a rule the greatest bar to progress. The forest-floor covered with closelymatted undecomposed leaves carries comparatively few ferns as compared with the wealth of the latter in rain-forest; the ground is usually drier and filmy ferns and the larger lichens are not a feature. Rubus and Muehlenbeckia are absent and, while Asplenium flaccidum and Polypodium diversifolium are common, other vascular epiphytes are not strongly developed. Cyclophorus serpens, a plant of dry situations, is here the one exception. Mosses and liverworts occur but do not make the close green mantle common to associations of rainforest. In almost every case these isolated groups of Nothofagus are confined to ridges or convex slopes holding but little moisture, and the surrounding rain-forest occupies the moister and more level situations. The most striking difference between the two types of forest, however, is the conditions offered for the germination and development of seedlings within the precincts of the forests themselves. If these local Nothofagus communities are not actually hostile to the seedlings of N. Menziesii, they certainly do not encourage them within their borders. The rain-forest treats its progeny in an altogether different manner, better conditions for the germination and future welfare of the young plants being afforded. Regeneration in the southern-beech forest depends on the death of the older trees; light is admitted allowing the young trees to develop. An instance of this may be recorded from a sapling growing in the Boulder Hill group. It had 18 annual rings in the first 2cm. of its diameter and then grew only 12 additional rings to reach 18cm. diam. Evidently a fallen tree had let in the light and the plant had rushed ahead. Seedlings in abundance are found only in the outer edge of pure southern-beech forest, as for instance at Silver Peaks where there is no enveloping rain-forest, or in places where fallen trees or cleared spaces let in the necessary light. We have found that Nothofagus seeds invariably germinate, and seedlings are established and flourish best under the following conditions: (a) Along the edges of burnt or cleared forest; (b) where the soil has been disturbed by flooding or land-slips; (c) where the ground-covering of undecayed humus has been disturbed by temporary grazing or other means, e.g., rooting of wild pigs. This disturbance enables the young plants to take root, where in heavy humus ground seeds would perhaps germinate but would not obtain roothold and develop. The vitality of Nothofagus and its capacity for flourishing in extremely diverse situations must not be overlooked. Trees growing near streams, on stream-banks and in positions exposed to frequent flooding, are as well-developed and healthy as are those on the ridges, and are quite able to carry—as at Woodside and Maungatua—huge masses of Elytranthe Colensoi without seemingly being greatly affected.

6. Examination of cockayne's theory in the light of the occurrence of nothofagus in the dunedin area. As nothing in nature can stand still and all forest is in a continual state of change, Nothofagus must either be a new-comer throwing out its seedlings into the surrounding or adjacent rainforest and spreading on all sides, or else it is a remnant of primeval forest making its last stand against an invader. From our observations we are convinced that there is no middle course, that the two types of forest do not live amicably together and pursue a common destiny. There is no real union, and as Cockayne states (1926: 27): “There is properly not one but two distinct plant-formations side by side.” A study of all these isolated Nothofagus groups in the Dunedin area convinces us of the truth of Cockayne's statement, and creates a lasting impression that these groups are slowly but surely being choked out by the pressure of the antagonistic rain-forest. That species once common can be wiped out, is shown by the fate of Podocarpus spicatus in Stewart Island where Weinmannia racemosa has almost replaced it (Cockayne, L., 1921: 124). It is natural to expect an invader of an island to take possession first of the shores, then to encompass the lower country and finally to push up into the high lands as far as conditions will allow. One would not expect and certainly we can supply no evidence of an invasion of Nothofagus from the higher country down into the lower. These local groups, stands, or colonies of N. Menziesii are usually surrounded by rain-forest but never surround such forest, nor does the Nothofagus ever appear on the margin of the rain-forest, pushing its way in as would be the normal course of attack. In the Dunedin area Nothofagus seedlings or saplings do not occur outside of their own colonies, and do not develop without the incoming of light, and this the encroaching undergrowth of the rain-forest absolutely prohibits. In certain stages of the conflict it is possible for isolated Nothofagus trees to be left, dotted here and there, in the midst of the subtropical forest, thus giving the impression that a mixed Nothofagus-subtropical forest-association is being viewed, but though individual N. Menziesii trees do occur in this manner, this stage is very little in evidence in the Dunedin area. These isolated trees will of course persist for hundreds of years in such situations, but even if their seeds germinate, the seedlings are suppressed and expansion becomes impossible. When we consider the unthinkable amount of time that the fight has been going on, the comparative slowness of decisive results, and the wide areas—North Auckland to Foveaux Strait—over which the struggle is being waged, it is little wonder that here and there places occur in which the result of the battle may not appear to be in favour of the legions of the subtropical rainforest. Moreover, taking into consideration the vast areas already occupied by Nothofagus in New Zealand, if it be a new-comer it certainly should be a very aggressive one. That this is not so may easily be seen by studying any of the local groups cited in this paper. For instance, at Bethune Gully, southern-beech trees of great age are present in numbers, trees moreover which to all appearances are

older than the oldest trees of the surrounding rain-forest, and although these have had time for their progeny to settle down over large tracts of country, the change is retrogressive, not progressive! The extreme age of these old trees makes the observer wonder why they have not, so to speak, populated the earth, especially when the capacity of the seedlings for rapid and forward growth is taken into account, a rate of growth much in excess of that of any of the species of New Zealand rain-forest. That if man does not interfere the larger-leaved forest trees will ultimately push back and replace the Nothofagus is, however, certain. The dense entangled undergrowth of second-layer trees, the shading canopy of shrubs and tree-ferns, and the close floor-covering of Blechnum and Polystichum, will in the end inevitably conquer in the struggle of the subantarctic primeval vegetation against the subtropical invader! Summary And Conclusions. 1. The paper deals with the relation, in the country adjacent to Dunedin (South Otago Botanical District), of the subtropical forest to the subantarctic forest—the former a forest dominated by broadleaved dicotylous trees and podocarps, and the latter (taking the formation for all New Zealand) by one or more species of Nothofagus. 2. Most of the forest near Dunedin is subtropical, but there are also at least twelve pieces of Nothofagus Menziesii forest, mostly quite small, and the question to be answered at once arises, “Is N. Menziesii a new arrival or merely a survivor of a former host?” 3. This question leads up to a verification or negation of L. Cockayne's theory that Nothofagu forest was originally the chief tree-community of New Zealand, but that it has been gradually replaced on the more fertile ground by a subtropical forest of Malayan origin, so that now it is restricted to the poorer ground and to the higher altitudes. 4. Prior to this study, only 5 pieces of Nothofagus forest had been recorded near Dunedin (of these, 3 remain), but the authors record 9 more, one of which is no less than a square kilometre in area. 5. Each of the Nothofagus communities is described in detail, and lists of the species are given. 6. One area—Bethune Gully—is an unbroken colony of N. Menziesii standing in the midst of a heavy association of subtropical forest, all its Nothofagi (168) were measured and a table is presented placing them into 16 classes according to their average diameters, and the percentage of trees for each class is given. 7. A similar table is presented for 137 Nothofagi in another of the areas. 8. Three other tables are presented which show the relative rates of growth of 8 trees in 3 areas, the light-intensity of each area as compared with that of the open being respectively 1/55, 1/25, and 1/13, the average annual increase in diameter for the young trees in each area being respectively 0.0668cm., 0.0715cm., and 0.0948cm. 9. A fourth table shows the rate of growth of 6 trees under still stronger light, the average annual increase in diameter being 0.4917cm.

10. A main difference in structure between subtropical forest and Nothofagus forest is the extreme density of the former and the openness of the later. 11. The interior of the Nothofagus communities is not favourable for the establishment of seedling Nothofagi, the most favourable positions being (a) along the edges of burnt or cleared forest, (b) where the surface-soil has been disturbed by grazing or rooting animals, and (c) where the soil has been disturbed by flooding or land slips. 12. The conclusions regarding the matters outlined in 2 and 3 are as folows:— (a) Either Nothofagus is a new-comer or the forest it dominates is a remnant of an earlier primeval forest. (b) The study of the isolated Nothofagus groups in the Dunedin area supports Cockayne's theory, for such groups are slowly but surely being suppressed by the antagonistic subtropical forest. (c) There is no evidence of an invasion of Nothofagus from the higher levels to the lower. (d) The local groups of Nothofagus forest are usually surrounded by subtropical forest and they never surround the latter, nor does Nothofagus ever appear on the margin of subtropical forest, pushing its way into that community. (e) Nothofagus seedlings or saplings do not occur outside of their own class of forest nor can seedlings become established beneath the dense undergrowth of subtropical forest. (f) Were Nothofagus a new-comer it should be very aggresive whereas, in the Dunedin area, quite the contrary is the case Papers Etc., Referred to. Cockayne, L., 1921. The Vegetation of New Zealand, pp. 124, 322-23. Cockayne, L., 1926. Monograph on the New Zealand Beech Forests, Part 1, pp. 27, 30, 39. Dunedin field club, 1916. Catalogues of the Indigenous and Introduced Flowering Plants, Ferns, and Seaweeds, occurring in the Dunedin District, p. 21, Dunedin, Orr, Campbell and Co. Petrie, D., 1896. List of the Flowering Plants indigenous to Otago, with indications of their Distribution and Range in Altitude, Trans. N.Z. Inst., vol. 28, p. 573. Watt, M. N., 1924. Leaf mining insects of New Zealand, Trans. N.Z. Inst., vol. 24, pp. 674-675.