Botanical Notes on Three High Peaks Overlooking the Hauraki Gulf, By

213 BOTANICAL NOTES ON THREE HIGH PEAKS OVERLOOKING THE HAURAKI GULF by Lucy B. Moore* SUMMARY Mt. Hobson (622 m), Hauturu (723 m) and Moehau (892 m), the highest points of Great Barrier Island, Little Barrier Island and Cape Colville Peninsula respectively, all support predominantly woody vegetation to their highest levels. Moehau offers the widest range of habitats, including cushion bog, and changes there since the author's observations began in 1929 are outlined. Floristically the three peaks show resemblances to and differences from one another, and selected species are listed in groups according to their occurrence here, and on other high land of the Auckland district. INTRODUCTION Auckland's north-eastern skyline boasts three mountain peaks, Hauturu (723 m), 75 km distant on Little Barrier Island, Mt Hobson (622 m), a dim 75 km away on Great Barrier Island, and Moehau (892 m, Te Moehau of earlier maps) some 69 km off on Coromandel Peninsula (Fig. 1). The latter, botanically, is about as much on an island as the other two. Cockayne (1928 p. 382) included all these places in the Thames Subdistrict (of his South Auckland Botanical District), the land boundary of which follows the Waihou River southwards almost to its source and then runs ("obviously a quite arbitrary boundary") roughly northeast to about Te Puke. Within this subdistrict, as is shown here, there is considerable diversity from south to north; long ago Adams (1885) was impressed by the difference between the vegetation of Te Aroha Mountain and that of the dividing range east of the town of Thames, and he gave contrasting lists of species characteristic of the two florulas. When later he made the first ascent of Moehau, his report (1889) was so preoccupied with the unforeseen montane element of the florula there that he failed to mention the absence of certain important species, which he had noted as.characteristic of the Thames Range, and which Kirk (1869) had recorded on Great Barrier further north. The plants of Little Barrier were listed (in Hamilton 1961) by Hamilton and Atkinson who, like Cockayne, found more ecological and floristic resemblances to the Coromandel Peninsula than to the adjacent mainland to the west. They drew attention to the unexpected absences, and recorded the presence of some species only as young plants, and the very local occurrence of others, but little of this is directly relevant to the higher altitudes. The following discussion of the vegetation and flora of the three mountain tops is based in part on direct observations on Little Barrier Island in 1942, on Great Barrier in August 1972, and on Moehau during ten visits between 1929 and 1934, totalling some 20 days on various parts of the range, supplemented by one day in 1939 and another in 1971. *c/o Botany Division, Department of Scientific & Industrial Research, Christchurch. 214 Location map 215 VEGETATION On each mountain there is a definite zonation, with some species dropping out and new ones appearing as altitude increases, and it is by the presence of these upland plants that upper levels are recognized for the present discussion. Many species, common in the lowlands, extend to even the highest tops or reappear there after being absent on intervening slopes. With the change in species there is an alteration in the structural character of the vegetation the trees finally becoming short, mostly many-trunked and thickly draped with bryophytes, though I saw no very good example of this mossy forest on Mt Hobson. On or near each summit outstanding rocks offer sites suitable for small, light-demanding plants, but only on Moehau is there extensive, well-developed peat with a low covering of cushion plants and/or sphagnum moss. All the tops have been altered to some extent. On Hauturu the disturbance has been least; surveyors made a clearing about the trig station and the few tracks have been trampled by many human feet. Mt Hobson has at least two tracks to the summit, one of them much used. The remains of a high dam at about 550 m testify to the extensive activities of bushmen over a number of years. Here stray cattle, sheep, goats, wild pigs and rabbits (all absent from Little Barrier) have access to the top but any effect they have on the vegetation is not immediately obvious. Opossums appear to be absent. The highest part that I saw, near the dam, showed little sign of having been burnt at any recent date; scrub 3-4 m tall on a narrow ridge included a mixture of high-level and lowland plants, the surrounding forest on steep slopes being dominated by Dacrydium intermedium. Moehau presents quite another picture, though one of its insular character• istics is that opossums still appeared to be absent in December 1971. Adams (1889) considered that there was nothing upon the mountain to support life — neither bird nor beast - "so that, after a few expeditions have been made to fully explore the summit for plants, Te Moehau will probably be left undisturbed except for the wind". How wrong he was! Maclaren (1899) wrote of "tracks worn into mud by the wild cattle that abound on Moehau" and settlers told us of long-haired aggressive beasts that had been on the mountain "since Adam and Eve were boys", but we saw no signs of their presence on the many high ridges we explored in the 1930's (Moore and Cranwell, 1934). We saw numbers of goats, and noted how well the line cut by surveyors served them as a route along the top of the main ridge through thick wind-scrub. From our own experience we could easily believe tales of animals being bailed up here for killing, as if in a fenced race. Pigs we heard often and their wallows were numerous, but not towards the real summits. Later Mason and Chambers (1950) recorded wild sheep in kamahi forest. A boggy slope on the eastern face of the trig peak had obviously been burnt; we were told by Mr Bronlund, who had lived within sight of it at Stony Bay since about 1895, that the only fire he had ever seen there was one "lit by Bill Wharfe in a dry summer" about 1899. In more recent years visitors to the tops have been relatively numerous, and observers with specific projects have maintained camps there. During the last 35 years there have been great changes. In 1971 goats were seen in mobs right to the top, droppings gave good evidence that cattle 216 frequented the upper levels, and in full daylight two large pigs wandered about the broad open slope below and to the east of the trig peak. Photographs show that the area of open ground increased there as trees died, and that extensive grassland developed. Even the previously impenetrable short scrub on the main ridge between the trig and the rocky peak has been opened up and, though still mostly woody, it is now easily traversed in any direction by man or beast. On the south side, immediately under the rocky peak, there is an undamaged remnant of the tightly interlaced mossy forest that was once much more extensive. Below the rocky peak in the direction of the top of the Hope ridge the area of open wet bog has expanded greatly. New landslips have occurred and one of them below the bog that occupies the head of the Ongohi stream, may have taken with it the only plant of Cordyline indivisa that we ever saw on the mountain. In contrast to all this down-graded vegetation, a new forest, with Libocedrus bidwillii as the vigorous dominant, is growing up on the rounded eminence of the trig peak, partly on the sunny, boggy slope amongst cushions of Oreobolus pectinatus, and partly within the area of the old burn on the eastern side. FLORISTICS The following list sets out some of the striking contrasts between the species to be found on the upper levels of the three mountains, and indicates more general distributions. Records were assembled from the published papers listed below and from field notes (principally those of Cranwell and Moore 1929-1934 from Moehau, confirmed to a large extent by a list compiled by A.E. Esler in 1971), and by reference to herbarium specimens. Collections at Botany Division, Department of Scientific and Industrial Research, made by A.P. Druce in recent years, have added much useful information about the plants of the Thames and Kaimai Ranges, but the numerous specimens brought from Great Barrier to the Auckland Museum by R.C. Cooper between 1960 and 1970 have been by no means fully investigated. The Pirongia records of Gudex (1955) were supple• mented by others from R.I. Bell. A provisional checklist of the plants of Great Barrier Island, lowland as well as upland, has been prepared, using the more obvious published sources (chiefly Kirk, 1869) and also some herbarium specimens; this may be consulted at Botany Division. The list of selected species presented here is not rigidly critical. It is offered as a basis for checking by botanists and in the hope that it may stimulate comparisons by workers in other groups. An obvious example concerns frogs of the genus Leiopelma, which have not been found on the Barrier islands (Stephenson, 1961). The whole "main axial elevation of the Hauraki Peninsula, an elevation that has its northern termination in the Great Barrier Island" (Maclaren, 1899) presents many problems for discussion by biogeographers and biohistorians. 217 SELECTED SPECIES LIST On Moehau but not on Great or Little Barrier Islands. A. Species here reaching their northern limit and not known elsewhere on Coromandel, Thames, Kaimai, Hunua or Pirongia Ranges: far removed from other occurrences and all low-growing plants of open places, either peat bogs or rock.

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