Art. XXXI.—The Vegetation of the Tarawera Mountains, New Zealand.
[Read before the Wellington Philosophical Society, 27th October, 1915]
On the 10th June, 1886, New-Zealanders were startled from their quiet lives by a volcanic eruption, the sounds of which reached from three to four hundred miles north and south from the seat of the outburst, while the ashes fell over an area variously estimated at from four thousand to six thousand square miles. The greatest depth of the matter ejected, measured at the lip of the great vent, was 170 ft., the top of the range being increased by this amount. It has been estimated that from two-fifths to one cubic mile of material was thrown out. The eruption took place along a flat-topped range, 3,600 ft. altitude, composed of rhyolitic lava-flows, known as Tarawera Mountains, and comprising the peaks Wahanga (northernmost), Ruawahia, and Tarawera (southernmost). This range is situated on the eastern side of Lake Tarawera, in the thermal district of the North Island, where are situated Lakes Rotorua and Taupo, well known as tourist resorts.
A gigantic rent opened along the axis of the range, running roughly north-east and south-west, commencing at the north end and extending to Tarawera, thence in a line more westerly to Lake Rotomahana, the waters of which are thought to have caused further explosions. This rent finally ended at Lake Okaro in the south, taking but three or four hours to form. Along this immense chasm in the earth, nearly nine miles long, 900 ft. deep at its greatest and 300 ft. at its least depth, and a mile and a half to an eighth of a mile wide, were no fewer than seventeen points of eruption. The fissure is not continuous, but is bridged in several places by the original surface remaining in position. This titanic feature of the North Island thermal district is at the highest points certainly the most impressive of the sights, and probably the least visited by tourists.
The north-western face of the Tarawera Range at present rises from the shores of Lake Tarawera (which is 1,032 ft. above sea-level) to a height of 2,738 ft. above it, the summit of the range being 3,770 ft. above the sea. S. Percy Smith (2, 4, and 23), who had the advantage of thoroughly exploring the mountain both before and after the eruption, describes the contour of the mountain as being unlike any other in the district, with the plateau-like summit sloping down to, say, 400 ft., the steep “mural crown” below descending for, say, another 400 ft.; the sharply inclined talus at an angle of 30° extending 1,000 ft. below the rock-faces forming the “mural crown”; and the beautifully easy slopes, lowest of all, grading down to the lake-margin as a pumice beach or ending in low cliffs at the water's edge. This is a fair average of the aspect it presents on every side, except towards the east, where a range of less elevation joins it and spoils its symmetry. The forests which once clothed the slopes of this mountain, according to the above authority, were of considerable extent, especially over the south-eastern flanks—that is, on the opposite side of the range to those described in this paper. The eruption has utterly destroyed these forests. Instances of a totara (Podocarpus totara) and rimu (Dacrydium cupressinum) standing on the edge of the chasm are given (2, p. 52).
A. P. W. Thomas (11) has written perhaps the most comprehensive report of the eruption, although he had not the advantage of having visited the
mountain prior to that event. He states that forests composed of large trees grew upon the sides of the Tarawera Mountain, and these, of course, were wholly wrecked by the eruption. Those on the site of the chasm disappeared altogether. Fortunately, T. Kirk had ascended the mountain in 1872, and his published papers (1 and 27) make it plain that where favourable to plant-life the surface of the mountain was clothed with vegetation, though on the highest parts it was scanty and stunted. A dwarf shrubby vegetation was found on the very summit of Tarawera, in sheltered places affording cover for a luxuriant growth of mosses and lichens, in which the orchids Caladenia bifolia, Thelymitra longifolia, and Orthoceras Solandri occurred. Elsewhere on the summit were Metrosideros hypericifolia, Corokia buddleoides, Coprosma lucida, Olearia furfuracea, Raoulia tenuicaulis, Dracophyllum strictum, D. Urvilleanum, Polypodium serpens, Tmesipteris tannensis; while near the summit were noticed Lycopodium volubile (2,800 ft.), Astelia trinervia (3,300 ft.), Cyathodes empetrifolia, and Gaultheria oppositifolia (3,200 ft.).
On the margins of Tarawera Lake Kirk noticed abundant trees of Metrosideros tomentosa of large size, and also Astelia Cunninghamii, Scirpus maritimus, Ranunculus acaulis, and Chenopodium glaucum var. ambiguum. At the entrance to the gorge separating Ruawahia from Wahanga were observed large terrestrial specimens of Metrosideros robusta, and elsewhere he saw Panax Colensoi, the most prominent shrub, forming handsome dwarf bushes sheltering Hymenophyllum bivalve, H. multifidum, and other ferns; Danthonia sp., Deyeuxia quadriseta, and Pittosporum tenuifolium were also observed. He states that the total number of species collected above 3,000 ft. did not exceed seventy, and considered that the vegetation of the mountain comprised a remarkably limited number of species.*
It would be too much to assume that all vegetation was entirely killed out at the base of the mountain by the eruption of 1886. The dead stumps of large Metrosideros tomentosa trees may still be found standing at the lakeside, and many species of the family Myrtaceae are so tenacious of life that stumps with several feet of mud or scoria round them might have sprouted and produced seed. Moreover, seed might have become uncovered by the rain cutting gulches in the soft mud and sand, and have found the absence of competition from other plants a factor favourable to growth.
Thus, on account of the volcanic origin of Tarawera Mountain and the isolated position of the north-west face, the foot of which, save for one narrow isthmus, is washed by the waters of Lakes Rotomahana and Tarawera, and on account of the eruption of 1886, this area presents peculiar facility for the study of the spread of species on new ground, since only an infinitesmal fraction of the plants could have survived the 1886 eruption.†
The North-west Face.
In the spring of 1913 the author twice visited Tarawera, on the first occasion (14th September) ascending to the summit of the range by the
[Footnote] * Kirk instances other sea-littoral plants, such as Convolvulus Soldanella, Juncus maritimus var australiensis, Leptocarpus simplex, Carex pumila, Zoysia pungens, and Bromus arenarius, which are found in this thermal district, as supporting the theory of the submarine origin of the lowlands of the central portion of the North Island; but when one considers that wild water-fowl, such as shags, black swans, and wild duck, travel frequently between coast and lakes, and that shags nest in the Metrosideros tomentosa trees on the coast, a simpler explanation of the presence of these sea-littoral plants in fresh-water littoral situations far inland becomes apparent.
[Footnote] † A lithographed reproduction of a photo of Tarawera seen from the south-west before the eruption, in A. P. W. Thomas's report (loc cit.), shows dense forest to about one-third of the height above Lake Tarawera.
broad valley shown in Plate XIX, Fig. 1, lying to the north of the landing for Rotomahana Lake, and on the second visit landing on Kuaehape Beach, and, after examining the Metrosideros forest, proceeding to a point about 1,700 ft. above sea immediately above the beach.
In the midsummer of 1915–16 the author again twice visited Tarawera, on the first occasion ascending the range by the route taken in 1913, traversing the summits of Tarawera and Ruawahia, and returning from the sand crater by the scoria slope separating Ruawahia from Wahanga, and on the second occasion visiting the area called for convenience the northern face, which is separated from the area called the north-west face by a comparatively unbroken scoria slope which was traversed on the previous visit, descending from the sand crater to the lake.*
At Kuaehape Beach within a chain of the lake there are two beach-levels, the lower consisting of white pumice, barren of plant-life, but mixed with driftwood, and the upper beach, a few feet higher, composed of red pumice and sand with patches of Raoulia australis dotted about, while growing at the edge of the beach are bushes of Veronica salicifolia var and Coriaria ruscifolia. Scattered about are young plants of a naturalized Erigeron. Shrubs of Myrsine Urvillei, Cyathodes acerosa, and Muehlenbeckia complexa are near at hand, and the herb Hydrocotyle asiatica also occurs. A little to the right of the beach are lava cliffs about 250 ft. high, which are covered with a growth of young Metrosideros tomentosa forest, fringed at its margin with Coriaria ruscifolia and Veronica salicifolia var., and containing also the following: Knightia excelsa, Coprosma lucida, Leptospermum ericoides, Panax arboreum, Pittosporum tenuifolium, P. Colensoi, Geniostoma ligustrifolium, Leucopogon fasciculatum, Gaultheria antipoda var., Cyathodes acerosa, Halorrhagis erecta, Poa anceps. Where the forest reaches the shore there are many dead stumps of Metrosideros tomentosa which had been killed by the eruption. Plate XX, Fig. 2, gives a very good idea of the vigorous young growth on the lake-side.
In the broad valleys of the lower slopes, where the soil is better, the dominant plant is Coriaria ruscifolia, forming pure shrubberies, 15 ft. to 20 ft. high, the plants having numerous trunks, 6 in. to 8 in. in diameter, springing from the ground. On the gravels of temporary watercourses patches of Raoulia australis are attempting to form a covering. In the more exposed situations, where the soil is poorer and not so moist and the altitude greater, the Coriaria is replaced wholly or in part by Leptospermum scoparium (see Plate XXI, Fig. 1).
Ascending a deep gully above Kuaehape Beach, where surface waters had cut the beds of ash into a vertical-walled ravine, the following were noticed between lake-level (1,040 ft.) and 1,500 ft. above sea-level. Shrubs or young trees—Metrosideros tomentosa, Weinmannia racemosa, Pittosporum tenuifolium, Leptospermum scoparium, Veronica salicifolia var., Olearia furfuracea, Fuchsia excorticata, Melicytus ramiflorus, Griselinia littoralis, Leucopogon fasciculatus, L. Fraseri, Gaultheria oppositifolia (in large masses 6 ft. across on the walls of the gorge), Pimelea laevigata, Solanum aviculare, Coprosma robusta, Melicytus ramiflorus, Muehlenbeckia axillaris; lianes—Rubus australis, Muehlenbeckia australis; herbs—Anagallis arvensis (naturalized), Epilobium rotundifolium, Dianella intermedia, Gahnia pauciflora, Cladium Vauthiera, Acaena Sanguisorbae var., ferns—Pteris esculenta, P.
[Footnote] * The author is much indebted to Judge Brown, Mr. Tai Mitchell (Government Surveyor), and Mr. L. D. Foster for their company and assistance in one or more of these journeys, and to Mr. Warbrick (in charge of the tourist traffic on the lake) for assistance in landing at different points.
Fig. 1.—Valley of ascent to summit, looking west Foreground, scoria slopes; middle distance scattered Coriaria bushes; background, almost pure Coriaria association on mud-covered hills deeply furrowed by surface waters, distance, Lake Tarawera
[G D Valentine, photo]
Fig. 2.—Tarawera Mountain, looking north-east, from site of Te Ariki Village (destroyed), showing Green Lake crater and mud-covered hills. Taken shortly after the eruption
Fig. 1.—Looking south-east across deepest part of Tarawera chasm, showing on opposite wall the lavas which compose the scoria slopes—the lighter, rhyolitic the darker, andesitic
[B C Aston, photo]
Fig. 2.—Taken from boat on Lake Tarawera, looking south-east, near Kauchape Beach Fringing lake are dead stumps of Metrosideros tomentosa. On the beach is a fringing shrubbery of Corana bushes merging into a tangled mass of shrubs and lianes. Higher is young forest of M [ unclear: ] and K. excelsa. of conical habit
[B C Aston, photo]
Fig. 1.—At 1,700 ft. above sea, looking south-east. Foreground of light and dark scoria, dotted with patches of Pimelea lae
ata near walking-stick stuck in ground Scattered shrubbery of Lepto–peomum
var. extending up the easy scoria slopes to the steeply inclined unstable slopes below the “mural crown” of stable lavas. On the highest point of Tarawera may be seen a cap of red scoria. In the distance is the gully separating the range into Ruawahia (left) and Tarawera proper (right)
[B C Aston, photo] Fig. 2.—At 1,500 ft. above sea, the broad valley separating the portion called “north-west face” from that called “northern face,” and more northerly to the view in Fig. 1 above. Foreground, Muchlenbeekia axillaris and pimelea patches with Leptospermum [ unclear: ] var. growing out of them, and scattered plants of [ unclear: ] middle distance, scattered [ unclear: ] and Leptospermum bushes, with background on either side of forest showing dead stumps of Met [ unclear: ] robusta distance, unstable slopes of steeply inclined scoria becoming stabilized by Raoulia and other patch-plants. On the extreme left of the picture, skirting the young forest, is the track to the sand crater
[B C Aston, photo]
Fig. 1.—Taken near view shown in Plate XXI, Fig. 2. Foreground white and black scoria mixed. Slopes becoming stable by growth of Raoulia patches and
association developing showing individuals growing from Raoulia patches
[B C Aston, photo]
Fig. 2.—At 1,700 ft. above sea looking north. Young forest on northern face, showing dead stumps of trees killed by the eruption
tremula, Lomaria capensis, Asplenium flaccidum, A. adiantoides, A. lucidum, Polypodium Billardieri, P. pennigerum, P. serpens, Hemitelia Smithii, Cyathea dealbata, Pellaea rotundifolia.
Now succeed scoria flats which support a sparse growth, 2 ft. to 6 ft. high, of Coriaria ruscifolia, Pteris esculenta, Veronica salicifolia var., Olearia furfuracea, Coprosma robusta, Weinmannia racemosa, Leptospermum scoparium, while Pimelea laevigata in patches a foot or more in diameter are closely appressed to the pumice-gravel.
Finally, at 1,550 ft., open stony slopes are reached where the rise is so gentle as to be hardly perceptible. Here the growth of shrubs is still scantier. The Pteris disappears, and the vegetation is Leptospermum ericoides, Coriaria ruscifolia, Veronica salicifolia var., Pimelea patches, and numerous young plants of the naturalized Oenothera odorata, evidently seedlings from last year's old plants. From this point to the “mural crown,” which can be seen in Plate XXI, Fig. 1, the vegetation was not inspected, the journey to the summit being made by a more southerly route, where, by avoiding the “mural crown,” and by travelling for a while on the edge of the crater, the top of the range is more easily approached (see Plate XIX, Fig. 2). On this route, in addition to many of the species already mentioned, the following were seen up to 1,800 ft.: Shrub—Aristolelia racemosa; giant reed—Arundo conspicua; herbs—Epilobium nummularifolium, Raoulia australis, Gnaphalium luteo-album, Wahlenbergia gracilis, Thelymitra sp., Danthonia semiannularis var., Raoulia glabra, Carex sp., Erechtites scaberula, and naturalized plants of Hypochoeris radicata, Sonchus oleraceus, Trifolium repens, T. pratense; ferns—Pteris esculenta.
At 1,800 ft. there were noted a few stunted shrubs of Weinmannia racemosa, Gaultheria oppositifolia, G. antipoda, Leucopogon fasciculatus, L. Fraseri, Dracophyllum subulatum, Muehlenbeckia axillaris, Cyathodes empetrifolia, Metrosideros robusta, Griselinia littoralis, Dodonaea viscosa, and Lycopodium densum; the herbs Raoulia australis and Drosera auriculata; and the ferns Lomaria penna marina, L. capense, Polypodium Billardieri.
On compacted scoria slopes at 3,000 ft. patches of Raoulia tenuicaulis (in flower), R. australis, Danthonia semiannularis var., and Hypochoeris seedlings were the higher plants, while occasionally in a damper cavity than usual a fern would be found, and patches of moss.
On the summit of the range there is a cap of red scoria, on which the only growth at present is patches of silvery Raoulia australis.
On account of the Tarawera Mountain-range having been built up by successive outflows of lava, ashes, and mud, and also on account of its isolated position, its flora might be expected to show species which are specially adapted to spreading easily by means of wind and water and birds; and this we find to be the case. Practically the whole of the plants found on the mountain are those the seed of which is thus spread. The species having succulent edible fruits—e.g., Coriaria—and therefore which are spread by means of birds, in the number of individuals hold first place on the lower slopes, while those which have light seeds, or seeds furnished with special structures enabling them to float in the wind, and capable of travelling long distances in the air, are a good second, and on the higher slopes are dominant—e.g., Raoulia and Leptospermum. And this is true of the plants observed by Kirk in 1872, before the eruption in 1886, as well as of those recorded by me in 1913, twenty-seven years afterwards.
The following are the principal forest-trees of the Rotorua district, which should, of course, be growing on the lower western slopes of Tarawera;
but those which are not probably lack a means of transport for their heavy seeds:—
Beilschmiedia tawa Benth & Hook. f. This tree constitutes 75 per cent. of the millable timber in some parts of the Rotorua district. The berry is 1 in. long, and solitary-seeded. Its distribution is effected probably entirely by rare large birds (pigeons and kaka parrots)
Kirk records the following as “chief trees of Ngongotaha (a forest-clad mountain, 2,554 ft., seven miles west of Rotorua) and the adjacent hills” (1, p 327).—
Dacrydium cupressinum Sol. Nut ovoid, about ⅛ in. long
Metrosideros robusta A. Cunn.
Beilschmiedia tawa Benth. & Hook. f
Knightia excelsa R. Br. Pubescent follicles 1 ½ in. long, tapering into the persistent style, ultimately splitting into two boat-shaped valves containing 3 or 4 winged seeds.
Litsaea calicaris Benth & Hook. f Solitary-seeded berry, ¾ in. long.
Laurelia novae-zelandiae A. Cunn. Achenes hairy, narrowed into long plumose styles. (This tree is common in the forests on the west side of Lake Tarawera)
Abundant in the forest at the north end of Lake Rotorua, according to Kirk, are the following trees:—
Elaeocarpus dentatus Vahl. Drupe about ½ in. long, oblong, ovoid, stone rugose, 1-celled, 1-seeded.
Metrosideros robusta A Cunn. Capsule coriaceous, 3-celled, 3-valved, or irregularly dehiscent, seeds densely packed, numerous, linear
Podocarpus spicatus R. Br Drupe ⅓ in. in diameter
Podocarpus ferrugineus D. Don Drupe ¾ in. long.
Knightia excelsa R. Br.
L [ unclear: ] itsaea calicaris Benth. & Hook.
Much less frequent, he says, are—
Weinmannia racemosa Linn. f. Capsule ⅕ in. long, 2– to 3–valved, seeds hairy, minute, and numerous.
Fusanus Cunninghamii Benth. & Hook. f. Drupe ⅓–½ in long.
Ixerba biexioides A Cunn. Capsule ¾ in. diameter; seeds large, oblong, compressed.
Carmichaelia sp., probably C juncea Col. Common in many parts of the Rotorua district. Leguminous seeds.
In addition to those given by Kirk might be mentioned from my own observations—
Persoonia toru A. Cunn. Common on Karamea (Rainbow Mountain). Drupe ½ ⅓ in. long; 1- or 2-celled, with single seed in each cell.
The forest near Te Wairoa, the Maori village buried at the time of the eruption, now contains—
Laurelia novae-zelandiae A. Cunn. This species, which exhibits a decided preference for swampy land, may require soil-conditions which do not occur on Tarawera.
At the Te Ngae forest, about ten miles farther away, I noticed—
Podocarpus dacrydioides A. Rich. Fruit a black ovoid nut, about ⅙ in long, seated on a red fleshy receptacle.
Carpodetus serratus Forst. Fruit globose, size of small pea, almost fleshy, indehiscent 3–5-celled, seeds numerous, pendulous.
Clematis indivisa Willd. Achenes with a plumose tail often more than 2 in. long.
List of Species found on Tarawera Mountain, North-western Face, in September, 1913, and the Summer of 1915–16.
[A letter “B” prefixed to the name of the species denotes the probability of its being spread by birds, and “W” by wind. “?” before a name denotes that the method of disposal is doubtful, but possibly wild animals (rabbits or hares), or floated across by water, or carried by water-fowl.]
B.Melicytus ramiflorus Forst. Small berry, ⅕ in.
B.Pittosporum tenuifolium Banks & Sol. Capsule woody and seeds sticky.
B.—Colensoi Hook. f. Capsule woody and seeds sticky.
B.Aristotelia racemosa Hook. f. Berry size of a pea.
W.Dodonaea viscosa Jacq. Above 1,400 ft. Membranous compressed capsule, very broadly 2–3-winged; wings membranous.
B.Coriaria ruscifolia Linn. Above 1,400 ft. Crustaceous achenes invested by juicy petals.
B. Rubus australis Forst. Many succulent 1-seeded drupes crowded upon a dry receptacle.
? Acaena Sanguisorbae Vahl. var. Achenes attached to fruiting calyx provided with 4-barbed bristles.
? Weinmannia racemosa Linn. f. Above 1,400 ft. Capsule containing small hairy seeds.
W. Drosera auriculata Backh. Above 1,400 ft. Seeds minute.
[The section below cannot be correctly rendered as it contains complex formatting. See the image of the page for a more accurate rendering.]
W. Halorrhagis erecta Schindl. Seed small, dry, 2–4-seeded, nut 1/10 in. long with 4 ribs dilated into wings.
B. Gunnera monoica Raoul. Small fleshy drupe.
W. Leptospermum scoparium Forst. Above 1,400 ft. Woody or coriaceous capsule, containing numerous linear seeds.
W.—ericoides A. Rich. Above 1,400 ft. Linear seeds.
[The section below cannot be correctly rendered as it contains complex formatting. See the image of the page for a more accurate rendering.]
|W. Metrosideros florida Smith. Above 1,400 ft.||Coriaceous or woody capsule; seeds numerous, linear.|
|W. —robusta A. Cunn. Above 1,400 ft.|
|W — tomentosa A. Rich.|
|W. Epilobium junceum Sol.|
|W. —rotundifolium Forst.|
|W. — pubens A. Rich.||Capsule 4-angled, seeds numerous, furnished with a tuft of long hair at the summit.|
|W. —nummularifolium R. Cunn.|
|W. — melanocaulon Hook.|
|W. — microphyllum A. Rich.|
|W. — glabellum Forst.|
B. Fuchsia excorticata Linn. f. Fleshy, many-seeded berry.
? Hydrocotyle asiatica Linn. 2 dry, indehiscent, cohering carpels.
B. Panax arboreum Forst. 2–4-celled succulent exocarp.
B. Griselinia littoralis Raoul. Above 1,400 ft. Small 1-seeded berry.
B. Coprosma lucida, Forst. 2-seeded fleshy drupe.
B. — robusta Raoul. Above 1,400 ft. 2-seeded fleshy drupe.
W. Celmisia longifolia Cass var. Composite linear achene.
W. Olearia furfuracea Hook. f. Above 1,400 ft. Composite; achenes small with pappus hairs.
[The section below cannot be correctly rendered as it contains complex formatting. See the image of the page for a more accurate rendering.]
|W. Gnaphalium japonicum Thunb||Achene minutely papillose.|
|W. — luteo-album Linn.|
W. Vittadinia australis A. Rich. Linear pubescent achene; pappus copious.
W. Raoulia australis Hook. f. var. lutescens T. Kirk. Achenes with numerous extremely slender pappus hairs.
W.—tenuicaulis Hook. f. Above 1,400 ft. Achenes with copious pappus hairs.
W. —glabra Hook. f. Puberulous achenes.
W.Erechtites scaberula Hook. f. Achenes with many series of copious soft slender pappus hairs.
W. Senecio lautus Forst. Achenes linear, pappus copious.
W. Sonchus oleraceus Linn. Achenes with many series of copious soft slender pappus hairs.
? Wahlenbergia gracilis A. DC. Capsules 2–5-celled; seeds numerous, small, compressed.
B. Gaultheria antipoda Forst. var Above 1,400 ft. Capsule included in large and succulent calyx and lobes, seeds minute.
W. —oppositifolia Hook f Above 1,400 ft. Capsule dry; seeds minute.
B. Cyathodes acerosa R Br. A baccate succulent drupe.
B.—empetrifolia Hook f Above 1,400 ft 3–5-celled small drupe.
B. Leucopogon fasciculatus A. Rich. Above 1,400ft. Small baccate drupe.
B.—Fraseri A Cunn Above 1,400ft. Small baccate drupe
W. Dracophyllum subulatum Hook f Above 1,400 ft. 5-celled capsule with numerous seeds. Rare.
B. Myrsine Urvillei A DC Fruit small, globose, drupaceous, dry or fleshy.
? Geniostoma ligustrifolium A Cunn. Capsule splitting into 2 boat-shaped valves; seeds numerous.
B. Solanum aviculare Forst. Large many-seeded berry.
W. Veronica salicifolia Forst var Above 1,400 ft. Capsule.
|B.Muehlenbeckia australis Meissn.||Small nut enclosed in a succulent perianth|
|B.—axillaris Walp Above 1,400 ft.|
? Knightia excelsa R Br Coriaceous 1-celled, 4-seeded follicles, 1 ½ in. long, tapering into a persistent style, ultimately splitting into 2 boat-shaped valves; seeds winged at the top.
B. Pimelea laevigata Gaertn. Above 1,400 ft Fruit usually baccate.
W. Thelymitra longifolia Forst Orchid; seeds very minute.
W. Microtis porrifolia R. Br Orchid; seeds very minute.
B Dianella intermedia Endl. Berry.
? Juncus sp Capsule, small-seeded
? Typha angustifolia Linn. var. Aquatic.
? Gahnia pauciflora T Kirk Hard and bony nut
? —Gaudichaudiana Steud. Above 1,400 ft. Nut small.
? Carex sp. Nut.
W. Deyeuxia fiiliformis Petrie Caryopsis
W. Danthonia semiannularis R. Br. var. Above 1,400 ft. Caryopsis.
W. Dichelachne crinita Caryopsis.
W. Arundo conspicua Forst Caryopsis.
W. Poa anceps Forst Caryopsis
W. Cyathea dealbata Swartz Spores.
W. Hemitelia Smithii Hook Spores.
W. Pellaea rotundifolia Hook Spores.
W. Pteris aquilina Linn. var esculenta. Above 1,400 ft. Spores.
W. — tremula R. Br. Spores.
W. Lomaria lanceolata Spreng. Above 1,400 ft. Spores.
W. — penna marina Trev. Above 1,400 ft. Spores.
W. — capensis Willd. Above 1,400 ft. Spores.
W. Asplenium adiantoides C. Chr. Spores.
W. — lucidum Forst. Spores.
W. — flaccidum Forst. Spores.
W. Polypodium pennigerum Forst. Spores.
W. — serpen's Forst. Spores.
W. — Billardieri R. Br. Spores.
? Trifolium repens Linn. Possibly introduced by rabbits, hares, horses, or pigs.
W. Erigeron canadensis Linn.
W. Hypochaeris radicata Linn.
W. Anagallis arvensis Linn.
W. Oenothera odorata Jacq.
? Erythraea Centaurium Pers.
? Rumex Acetosella Linn.
If the above list be analysed it will be seen that of ninety-one species observed on the isolated north-western face, twenty-four (or 26 per cent.) may be called bird-distributed, fifty-three (or 58 per cent.) wind-distributed, and only fourteen (or 15 per cent.) are difficult to account for.
The absence of certain species may be noted. Perhaps, of forest-trees, the absence of all species of Nothofagus would be dismissed lightly, as few patches of Nothofagus forest are known in the Rotorua area; but on looking more carefully into the matter it is certainly singular that the highest mountain in that neighbourhood should not have been peopled by Nothofagus, were it not that its seeds are not obviously spread by birds or wind. Indeed, a knowledge of how Nothofagus seed is distributed may perhaps help to solve many points in the distribution of the genus at present a puzzle to ecologists. The genus occurs at Waimarino and on the volcanic mountain Ruapehu (four species), on the lower slopes of the Kaimanawa Mountains (three species), on Mount Hikurangi, on Te Aroha Mountain (volcanic), in the Mangorewa and Omanawa Gorges, and on the Mata [ unclear: ] Road near Te Puke.
Buchanan (29) in 1866 noted that the forest on Mount Egmont (an isolated volcanic mountain more distant from any Nothofagus forest on non-volcanic mountains than is Ruapehu, Tarawera, or Ngongotaha, and rising from sea-level to 8,200 ft) is chiefly peculiar through the absence of Nothofagus, and his observations, which related to a limited portion of the mountain, have been confirmed for the remainder of the area by subsequent observers.* On the other hand, Ruapehu (9,175 ft.) and Te Aroha (3,126 ft.) are not many miles distant in an air-line from Nothofagus-clad geologically ancient mountains, and therefore, judging from analogy, Nothofagus should some day appear on Tarawera.
Dracophyllum is a genus which occurs very sparingly on this portion of Tarawera, and Ixerba, Dacrydium, Podocarpus, Melicope, Carmichaelia, Carpodetus, Phyllocladus, Fusanus, and Parsonsia, all plentiful in the
[Footnote] *The author ascended Mount Egmont to the summit by the Inglewood track on the 14th February, 1901, and again on the 20th March, 1910.
Rotorua district, have not been observed on any portion of the north-west or northern faces. They are large-seeded plants, although some have fleshy fruits, and are no doubt distributed by large birds. One of the two naturalized rosaceous species may possibly have been spread by wild horses, which are said to fatten on the fruits.
The Northern Face.
From the sand-crater which separates the northernmost peak (Wahanga) from the middle peak (Ruawahia) after a few hundred feet of steep scoria descends a beautifully easy slope of scoria down to the lake-edge This slope is comparatively bare of continuous scrub growth until near the 40 ft. terrace above the lake, when a shrubbery of Leptospermum, &c., is encountered. This slope, where it descends without a break, forms a natural boundary separating what may be called the north-western area from the northern area. The area north of this boundary has been visited on two occasions. Numerous dry vertically walled ravines about 40 ft. deep run roughly parallel to each other, making progress across country slow. Landing near the eucalypts at the north end of the lake, several aquatic and semi-aquatic plants were noticed. In small stagnant pools was the submerged Nitella (two species), Potamogeton Cheeseman, and Mynophyllum sp, while on the margins were Glossostigma elatinoides (with pinkish flowers) and Typha angustifolia var.
Progress on to the 40 ft. terrace (the lake rose 40 ft. at the time of the eruption and afterwards subsided, this may be the beach formed at that time) was made easy by the tracks of wild horses. Several naturalized plants were noticed—e g., Rumex crispus, Oenothera (in beautiful yellow flower), Anagallis arvensis, Rumex Acetosella, Carduus pycnocephalus, Sonchus arvensis, Erigeron canadensis, Verbascum Blatteria, Bartsia viscosa, and, what is lamentable, Rosa rubiginosa and Rubus fruticosus. There is no doubt if these latter two get thoroughly established on the mountain they will be a fearful curse in days to come. The Oenothera seems to be able to thrive on the bare scoria without the aid of any humus, and is rapidly travelling up the mountain. A most interesting fact is that the great Coriaria association is here dying out. The tree form of Coriaria ruscifolia, 15 ft. high, with many large trunks springing from one root, as described above, are now dead. This accords with an observation of Mr C. Way, of the Wairoa accommodation-house, that, although the Coriaria is the first shrub to take possession of volcanic ejectamenta, it is comparatively short-lived. Here, where it is obviously dying out from old age, it is giving place to vigorous thickets of Aristotelia racemosa and Fuchsia excorticata. Aristotelia is entirely dominant in places, and is 20–25 ft high, but associated with it are Solanum aviculare, Melicytus ramiflorus, Cyathodes acerosa, Muehlenbeckia complexa, Asplenium flaccidum, and A. adiantoides. Some 50–60 ft above the lake the open scoria slope is reached, which leads to the sand-crater arete of Tarawera Here a most remarkable change is going on, which is unfolded to one as the gradual ascent is made. The gentle slope is covered in places with uneven patches of Raoulia australis and R glabra. These are the dominant patch plants. Others are Pimelea laevigata, Muehlenbeckia axillaris, and even Leucopogon Fraseri. Olearia furfuracea, the dominant composite shrub of the mountain, in full flower is a fine sight. Occasionally, where the water-supply is favourable, lichens and moss may perform their usual function of transforming the barren rock into fertile soil, but the Raoulia must be accounted the great humus-maker of this mountain.
As it languishes in vigour, owing to age, from it grow other plants, the chief woody ones being Coriaria and Leptospermum, and sometimes Pittosporum, but also herbaceous plants such as Trifolium and Rumex Acetosella. Four stages may thus be predicted for the repeopling of the plant-covering of this open area (excluding the ravines, which are able to jump the first and possibly the second stages): First, the patch plants; secondly, the Coriaria; thirdly, the Aristotelia, with possibly Fuchsia and Melicytus; fourthly, forest.
The scoria slope is now left at about 150 ft. above the lake, where the track towards the spur is found overgrown with Aristotelia, Rubus australis, Coprosma lucida, C. robusta, Veronica salicifolia var., and Coriaria.
A densely wooded ridge on the north of the scoria slope is investigated. It consists of Weinmannia racemosa, which is perhaps the dominant growth, but the composition is very varied. Knightia excelsa stands out above all the other young growth in cylindrical or slightly conical tops. A patch of tree-ferns is noticed. Giant Fuchsia and Weinmannia, with Melicytus ramiflorus, all about 30 ft. high, with a bare floor, form a subassociation of their own, supplanting the dying Coriaria, nearly as high. Higher on the spur, 500 ft. above the lake, the growth is more varied, being a thick mass of Panax arboreum, Olearia Cunninghamii, Brachyglottis repanda, Lomaria capensis, Veronica salicifolia var., young Wenmannia, Gaultheria oppositifolia, G. antipoda var., Carex Gaudichaudiana, and Cyathodes acerosa. At 675 ft. above the lake numerous dead stumps of Metrosideros occur These may either be M. tomentosa or M. robusta, young plants of both being common in flower on the open slopes at this altitude and higher. The ravines, four or five of which were crossed diagonally in returning to the scoria slope, yielded some valuable information as to the composition of the forest before the eruption. One dead Beilschmied tawa with a broken trunk 15–20 ft. high was 3 ft. in diameter, and springing from its side was a young tree about 18 m. in diameter 4 ft. from the ground, where it forked into a tree 35–40 ft. high. Close to this was a dead giant Litsaea calicaris stump 4 ft. in diameter at the surface, and 9 ft from the ground, where broken, 3 ft. in diameter; and attached to it was a young living shoot. Other dead Litsaea stumps showed that there had been a forest containing many of these, and young thickets of saplings showed that it was being re-established. Melicytus was also found springing from old dead stumps. Only two Beilschmiedias, both with young live growth springing from the dead stump, were, however, seen. Other plants not hitherto met with on the mountain are Rhipogonum scandens, Schefflera digitata, Hemitelia Smithii, Hedycarya arborea, Asplenium bulbiferum, Lomaria lanceolata, Gaultheria rupestris, Astelia Cunninghamn, Elaeocarpus dentatus, Cyathea, dealbata, Lycopodium volubile. Also present were Fuchsia excorticata, Asplenium lucidum, Polypodium Billardieri, P. pennigerum, Myrsine Urvillei, Dianella intermedia, Metrosideros robusta, Gunnera monoica, Vittadinia australis.
On the northern face of the mountain the following additional species were noted: Elaeocarpus dentatus Vahl, Olearia Cunninghamii Hook. f., Gaultheria rupestris R. Br., Hedycarya arborea Forst., Beilschmiedia tawa Benth & Hook, Litsaea calicaris Benth. & Hook., Cyathea dealbata Swartz, Hemiteliaa Smithii Hook., Lomaria lanceolata Spreng., Asplenium flabellifolium Cav.; together with the following naturalized species—Rubus fruticosus Linn., Rosa rubiginosa Linn., Sonchus arvensis Linn., Carduus pycnocephalus Linn, Verbascum Blattaria Linn., Bartsia viscosa Linn., Rumex crispus Linn.
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28 “New Zealand Plants and their Story” L Cockayne, 1910 p. 54
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