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Forest Vines to Snow Tussocks: The Story of New Zealand Plants

Fellfield

Fellfield

On the higher, steeper mountains, particularly of the South Island, herbfield gives way with increasing altitude to fellfield (Fig. 105). As a result of the severe environmental conditions in this zone, plants of this type of vegetation are both sparse and specialised. They are subjected to low average temperatures, heavy frosts, deep snow for part of the year, violent winds, and at times strong sunshine, which may raise the temperature of the extensive areas of exposed rock very considerably. Erosion by frost action and wind is quite rapid particularly on the greywacke sandstone of the Southern Alps and other axial ranges. The resulting angular fragments may form a thin layer of debris on ridge crests and sides; but gravity, assisted by wind and, more dramatically, avalanches, constantly moves the products of erosion downslope, so there is little opportunity for the development of even thin soils. Rock outcrops and bluffs in this zone provide more sheltered and secure sites for plants. Nevertheless a number of them do establish away from outcrops, especially in deeper debris on moderate to gentle slopes. Of these, some are small prostrate Hebe shrubs which are also to be found on rock outcrops. They are not of the whipcord type, but have small rounded leaves arranged in attractive patterns. Hebe haastii and H. epacridea (Fig. 106) are yellow or orangey-green; H. petriei is grey-green. Small herbs are more common — several diminutive grasses and sedges, and one to several species of Epilobium, Ranunculus, Celmisia, Gentiana, Myosotis and Parahebe. Small cushion plants also occur; these include Hectorella caespitosa, the softly pubescent species of Chionohebe, Phyllachne colensoi, and sometimes extensive mats of the silver grey Celmisia sessiliflora.

Rooted into clefts of rock outcrops or other stable sites are a number of rather larger and more striking plants. Hebes are prominent and include both whipcord and non-whipcord species. Notable among larger herbs are the grey-green, hairy Ranunculus buchananii with large, white flowers and the yellow-green R. grahamii with large yellow flowers. The former grows in the south-west of the South island, the latter only in the vicinity of Mt. Cook.144 Attractive as well as curious, because of their similarity to the edelweiss of the Swiss Alps, are two species of page 185
Figure 105 (above) Fellfield on the Black Birch Range, Marlborough.Photo: J. W. Dawson.

Figure 105 (above) Fellfield on the Black Birch Range, Marlborough.
Photo: J. W. Dawson.

Figure 106 (left) Hebe epacridea.Photo: M. D. King.

Figure 106 (left) Hebe epacridea.
Photo: M. D. King.

page 186Leucogenes—L. leontopodium throughout the North Island and the northeastern South Island and the smaller leaved L grandiceps throughout the South Island and Stewart Island. The flowers of both species are white and woolly with yellow to orange centres.
Most outstanding in these situations, however, are a number of large cushion plants, some of which, because of their hummocky form and woolly pubescence, are known as 'vegetable sheep'. These larger cushion plants are extremely firm in texture and sometimes a metre or more in diameter. The vegetable sheep belong to the daisy family (Compositae) and they are essentially shrubs — as is evidenced by the tortuous woody stems revealed by the erosion of dead plants. The living leaves of branch tips at the cushion surface closely invest one another as permanent buds, while the dead interior leaves break down into a blotting paper-like, water retentive mass, which fills the spaces between the branches. The Canterbury vegetable sheep (Raoulia eximia), found on drier eastern mountains from mid-Canterbury to north Otago, is
Figure 107 A rock in fellfield on the crest of the St. Arnaud Range, northern South Island. Frost action has formed fissures in the rock where small cushions of Colobanthus canaliculatus (left) and Raoulia bryoides (centre and right) have established.Photo: J. W. Dawson.

Figure 107 A rock in fellfield on the crest of the St. Arnaud Range, northern South Island. Frost action has formed fissures in the rock where small cushions of Colobanthus canaliculatus (left) and Raoulia bryoides (centre and right) have established.
Photo: J. W. Dawson.

page 187
Figure 108 Large cushion of the Marlborough vegetable sheep, Haastia pulvinaris. Mt. Cupola, Nelson Lakes National Park.Photo: J. W. Dawson.

Figure 108 Large cushion of the Marlborough vegetable sheep, Haastia pulvinaris. Mt. Cupola, Nelson Lakes National Park.
Photo: J. W. Dawson.

Figure 109 Close view of a portion of a Haastia pulvinaris cushion showing the branchlet tips closely invested by woolly leaves. Photo: J. W. Dawson.

Figure 109 Close view of a portion of a Haastia pulvinaris cushion showing the branchlet tips closely invested by woolly leaves. Photo: J. W. Dawson.

grey-green in colour and the velvety leaf buds are often compressed into more or less hexagonal shapes. Several other species of Raoulia form smaller cushions in fellfield (Fig. 107). The more handsome (in my view) Marlborough vegetable sheep (Haastia pulvinaris) is restricted to the drier mountains of the north east of the South Island. The large cushions are buff to pale yellow in colour and the leaf buds are larger and woollier than those of the raoulias (Figs. 108, 109).
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Two spaniards (Aciphylla) are notable cushion plants in fellfield. A. dobsonii in South Canterbury and North Otago may form perfectly hemispherical cushions more than half a metre in diameter (Fig. 110), while A. simplex of Central Otago forms somewhat smaller cushions. Both species have thick, rigid leaves coloured bright orange-yellow.

The two flowering plants of fellfield which hold the altitude record are Hebe haastii and Parahebe birleyii, both having been recorded at 2900 m in the Mt. Cook region.144 At 2800 m Ranunculus grahamii is not far behind. Above these altitudes only lichens and mosses cling to steep rocky faces in the zone of permanent snow.

Figure 110 Hemispherical cushion of the cushion spaniard, Aciphylla dobsonii. Mt. St. Bathans, Otago.Photo: J. W. Dawson.

Figure 110 Hemispherical cushion of the cushion spaniard, Aciphylla dobsonii. Mt. St. Bathans, Otago.
Photo: J. W. Dawson.