New Zealand

In January 2003 John and Hilary Birks had the opportunity to visit South Island, New Zealand and to see one of the strangest and most unusual temperate alpine floras in the world. They christened the alpine zone of South Island, New Zealand the 'land of the white gentians'. John and Hilary were members of an Alpine Garden Society expedition led by John Richards (Newcastle, UK), Mark Hanger (Dunedin, NZ), and Ross Graham (Dunedin, NZ). The trip travelled from the Nelson region in the north of South Island to Mount Burns in the far south of South Island. The approximate itinerary is shown in the map (from Alpine Garden Society 1995). All photographs here and in the picture gallery are copyright of John and Hilary Birks.

The alpine flora of South Island, New Zealand is unusual in several ways:
1. It is a geographically isolated and geologically young alpine flora that has evolved with little or not contact with other floras. The mountains and alpine habitats of South Island are some of the youngest in the world, possibly only about 5-7 million years old. The alpine flora is thought to have an evolutionary time span of only about 2 million years.
2. It has a very high species diversity. The total indigenous vascular plant flora of New Zealand is about 2450 species, of these about 650 species (26%) grow in alpine habitats and about 500 species are confined to the alpine zone.
3. It has a very high endemicity, with about 93% of the alpine species confined to New Zealand and 15% of the alpine genera endemic.
4. It shows considerable adaptive radiation, with much genetic mixing through interspecific and even some intergeneric hybridisation. This can cause some identification problems. Not all taxa have yet been formally described from New Zealand.
5. It shows great variation in growth forms, with tussock grasses, cushions, low-growing prostrate woody shrubs, spear grasses, etc.
6. It shows considerable polymorphism and variation, both genetic and environmental.
7. It consists predominantly of white flowers of a simple bowl shape. This predominance of white flowers is thought to be an adaptation to the scarcity of specialised pollinators (e.g. butterflies, long-tongued bees, hawk-moths). The insect fauna is very impoverished with only 16 species of butterfly.
As Jack Drake wrote in 1972, "to appreciate the New Zealand alpines, one must free oneself entirely from the mental picture of the alpine plants of Europe, for they are entirely different."

Geology and Landscapes
South Island is at the comparable latitude of Switzerland and Washington State in the USA in the Northern Hemisphere. From a botanical point-of-view, we visited five distinct areas, illustrated below.

1. The Mount Cook (Aoraki) (3733 m) area with its extensive valley glaciers and glacial landscapes, and an oceanic climate. The area continues south to the Fiordland area of the south-west around Milford Sound. This impressive area of mountains, fjords, and glaciated valleys is comprised primarily of granite and gneiss.

Mount Cook (summit in cloud) and the Haast ice-fall	Stirling Falls, Milford Sound	Gertrude Valley, Fiordland (1000 m)

Tasman Glacier near Mount Cook	Mitre Peak, Milford Sound

2. The Marlborough area of shale and greywacke, dry climate, and extensive screes in the Mount St Patrick, Blackbirch, Island Saddle, and Mount Hutt areas.

3. The central Otago area of schist rock, gentle summit areas, conspicuous weathered tors, and continental climate, in the Old Man Range, The Remarkables, and the Pisa Range.

Mount St Patrick screes and open vegetation (1500 m)	The Pisa Range (1850 m)
Southern Alps from Mount Burns (1100 m)	Mount Burns (1430 m)

4. The southernmost Southern Alps (Southland) of granite and gneiss, highly oceanic climate, and extensive tussock grasslands in the Mount Burns area, where some of 'The Lord of the Rings' was filmed.

5. The Arthur Range west of Nelson in the far north of South Island consisting of rounded low summits formed from metamorphosed limestone and marble.

Prior to human settlement, much of South Island below about 1000-1200 m was forested with conifer-broadleaf or southern beech (Nothofagus) forest.

John and Hilary Birks only visited a few forested areas, one consisting of giant Podocarpus totara trees (Peel Forest Park at 400 m), and the others of Nothofagus (N. menzieszii, N. solandri var. cliffortioides) between about 500-1250 m (Arthur Range, Routeburn Trail). The most striking features of these forests are the abundance of tree ferns (e.g. Cyathea smithii), ferns and fern allies (e.g. Polystichum vestitum, Phymatosorus diversifolium, Gleichenia dicarpa, Lycopodium cernuum), epiphytic ferns (e.g. Asplenium flaccidum, Pyrrosia eleagnifolia), bryophytes, and lichens, ground-dwelling mosses (e.g. Dendroligotrichum dendroides) and liverworts (e.g. Hymenophyton flabellatum), a rich diversity of filmy ferns (e.g. Hymenophyllum cupressiforme, Trichomanes colensoi), and rather small and non-showy orchids (e.g. Aporostylis bifolia, Caladenia chlorostyla, Pterostylis banksii, Thelymitra hatchii).

Tree-line varies from about 1200 m in the Nelson area to about 900 m in the Mount Burns area.

Tree-line about 1000 m in Milford Mountains	Tree-line on the Arthur Range at 1200 m

At, and just above, tree-line there is an abundance of low-growing densely twiggy dwarf-shrubs with very small slender leaves, slender wiry stems, and wide divaricating branches. This growth form occurs in 63 species in 20 genera in 17 families. Examples include Muehlenbeckia axillaris (Polygonaceae), Coprosma cheesemanii (Rubiaceae), and Discaria toumatou (Rhamnaceae). Two hypotheses have been presented to explain the high frequency of divaricating shrubs – (1) climatic adaptation and (2) defensive mechanism against browsing by moas, large flightless birds, now extinct, that took the place of browsing mammals. Analysis of the gizzard contents of fossil moas shows that moas ate these shrubs, along with other plants. This suggests that the climatic hypothesis, namely that the growth-form is a protection from wind abrasion, dessication, and frost damage at or near tree-line may be correct.

Low-Alpine Zone
This is characterised by snow-tussock grasslands of Chionochloa species that occupy 200-500 m above the tree-line. This is a rather unusual alpine life-form outside tropical mountains and the subantarctic region and has similarities to the Pampas grasslands (Cortaderia) of South America.

A wide variety of species occur in the low-alpine tussock grasslands, often in gaps between tussocks. These include several species of Aciphylla (speargrass or wild Spaniards) in the Apiaceae family (e.g. Aciphylla aurea, A. crosby-smithii, A. congesta, A. kirkii), the mountain flax Phormium cookianum (Phormiaceae), dragon-leafs Dracophyllum menziesii and D. uniflorum (Epacridaceae), and a variety of herbs, many of which are white flowered. These include Myostis suavis, Viola cunninghamii, Euphrasia revoluta, Ourisia glandulosa (Scrophulariaceae), Gentiana corymbifera, G. divisa, Chionohebe densifolia (Scrophulariaceae), the tall daisy-like Dolichoglottis lyallii (yellow), D. scorzoneroides (white), and hybrids (pale yellow), and the elegant Bulbinella gibbsii var. balanifera (Liliaceae). Buttercups are well represented, with, for example, Ranunculus gracilipes, R. "berggrenii", R. insignis, and the so-called Mt Cook Lily R. lyallii, the great mountain buttercup. Species of Geum occur locally (e.g. G. uniflorum, G. leiospermum). There is a staggering diversity of low-growing shrubs and dwarf-shrubs, including members of the largely (and large!) New Zealand genus Hebe with almost 100 species. Attractive Hebe species seen included H. subalpina, H. pinguifolia, H. petriei, H. pauciflora, H. epacridea, H. albicans, and the 'whip-cord' H. ochracea and H. hectorii. The Daphne family (Thymelaceae) has several beautiful low-growing dwarf-shrubs in South Island, including Kelleria croizatii, K. dieffenbachia. Pimelea oreophila, P. sericeovillosa, P. suteri, and P. traversii. Pentachondra pumila is an elegant dwarf member of the Epacridaceae growing in the low-alpine zone.

Patterned mires or 'cushion bogs' occur locally on flat or gently sloping ground in the low-alpine zone in the oceanic mountains of the Southern Alps (e.g. Mount Burns).

These mires and associated small tarns support a range of fascinating plants including the cushion-forming Donatia novae-zelandiae (Donatiaceae), the insectivorous Drosera stenopetala, D. arcturi, and Utricularia monanthos, the low creeping Kelleria paludosa, the yellow Euphrasia cockayneana, and the submerged aquatic Myriophyllum triphyllum.

High-Alpine Zone
Above about 1500 m, the vegetation cover becomes discontinuous, the snow-tussock grasses begin to disappear, and the high-alpine zone occurs between the nival zone of permanent snow and ice and the low-alpine zone, from about 1500 to about 2000 m.

Snowbanks and herbfields irrigated by snow-melt are locally common, with an abundance of Psychrophila (= Caltha) obtusa and elegant low-growing plants such as Ranunculus pachyrrhizus, R. sericophyllus, Dracophyllum prostratum, Euphrasia monroi, and E. australis, and the tall fern Polystichum cystostegia. Open wet gravels by snowbeds support Cardamine bilobata, C. corymbosa, and the rare Pachycladon novae-zelandiae.

On wind-exposed summit areas, species-rich cushion-field occurs growing on surprisingly deep, loess-rich soils, alternating with very open areas and frost-heaving and patterned ground such as stone-stripes and solifluction lobes.

Pisa Range snow beds	Temple Basin
Island Saddle	Mt St Patrick Range

Many attractive low-growing cushion plants occur in this habitat, including Phyllachne colensoi, P. rubra (Stylidiaceae), Hectorella caespitose (Hectorellaceae), Myosotis pulvinaris, Chionohebe myosotoides, C. pulvinaris, C. thomsonii, Euphrasia 'cushion species', Anisotome flexuosa (Apiaceae), A. imbricata var. imbricata, and several species of Raoulia (scab-weeds), a large and predominantly New Zealand genus of mat and cushion species, including R. grandiflora, R. mammillaris, and R. apice-nigra.

Cliffs and rock outcrops in the high-alpine zone provide specialised habitats for the beautiful Ranunculus buchananii and its hybrids with R. lyallii, and for Myosotis macrantha.

Extensive very open screes between 1300 and 1800 m are characteristic of the shale and greywacke areas on the eastern side of the Southern Alps in the Marlborough area. The average slope is 32 degrees.

A remarkably rich flora occurs on these seemingly inhospitable screes. Closer examination shows that many of these plants have leaves that are glaucous grey or brown in colour and waxy in texture and are effectively camouflaged. It is unclear what the purpose of such camouflage might be, but one hypothesis is camouflage from browsing by the now extinct moa. Fascinating plants of these screes include the penwiper Notothlaspi rosulatum (Brassicaceae), Ranunculus haastii, R. crithmifolius, Lignocarpa carnosula (Apiaceae), Geranium sessiliflorum, Leucogenes grandiceps (Asteraceae), Leptinella atrata, Haastia recurva (Asteraceae), Myosotis elderi, and the low-growing pea-relative Swainsonia novae-zelandiae. Willowherbs have their world headquarters in New Zealand growing on screes, river gravels, and other naturally open habitats. These include Epilobium alsinoides ssp. atriplicifolium, E. pycnostachyum, and the local Nelson endemic E. vernicosum.

Some of the most remarkable New Zealand alpine plants occur in so-called fell-field within the high-alpine zone. These are areas of relatively stable rock within or near unstable screes. The plant cover and soil are very sparse. In the South Island 'rain-shadow' mountains of Nelson and Marlborough they are associated with greywacke rock and are extremely distinct (even from an aeroplane!) by the occurrence of large, pale-coloured cushion plants known as 'vegetable sheep'.

Vegetable sheep include Raoulia bryoides, R. mammillaris, R. australis, R. eximia, and the large, coarser Haastia pulvinaris. Within these fell-fields there are few associates such as grasses and Luzula spp.

The genus that is most closely associated by alpine botanists and alpine gardeners with New Zealand is Celmisia, or mountain daisies. There are at least 62 described species, 59 of which occur in New Zealand. They rank with the snow tussocks as being the most important and striking feature of New Zealand alpine botany. Hybridisation and phenotypic variation are widespread, and identification is not always simple. Celmisia shows all possible variations on a vegetative theme, ranging from cushion forms (C. sessiliflora) to large conspicuous forms (e.g. C.coriacea, C. semicordata). A selection of Celmisia species is shown here. These include C. sessiliflora, C. coriacea, C. petriei, C. traversii, C. petiolata, C. monroi, C. hectorii, C. discolor, C. bellidioides, C. viscosa, and C. semicordata.

Conservation
One of the most striking features of the New Zealand landscape is the huge number of introduced plants, with over 2000 exotic species established in the wild. Recent predictions by Stephen Halloy and Alan Mark (2003, Arctic, Antarctic and Alpine Research 35: 248-254) suggest that with a temperature rise of 3ºC about 200-300 (33-50%) of the 650 indigenous alpine species will become endangered and be put at risk, or even become extinct by 2100 as a result of the loss of alpine areas by forest encroachment, habitat fragmentation, invasion by introduced species, and direct climatic effects.

Further Reading
Alpine Garden Society (1995) Special New Zealand Issue. Quarterly Bulletin of the Alpine Garden Society 63(3): 216-336
Dawson, J. (1993) Forest vines to snow tussocks. The story of New Zealand plants. Victoria University Press, Wellington.
Mark, A.F. & Adams, W.M. (1995) New Zealand alpine plants. Godwit, Auckland.
Philipson, W.R. & Hearn, D. (1967) Rock garden plants of the Southern Alps. Caxton Press, Christchurch