Forest Vines to Snow Tussocks: The Story of New Zealand Plants
Temperate South America and Antarctica
Temperate South America and Antarctica
Temperate South America, much wider than New Zealand in the north but narrowing southwards, is in some respects like the South Island of New Zealand on a much larger scale. The Andes and the Southern Alps both lie more or less at right angles to the prevailing westerlies, so page 233climates are wet in the west and much drier in the east. The Andes are much higher than the Southern Alps in the north at about 34° S, but they diminish in height southwards.
To the east of both mountain ranges are plains, but those in South America are much more extensive and in places drier than those of New Zealand. To the west in the South Island, and at equivalent latitudes in South America, the mountains come close to the sea with at most a narrow coastal plain in both places. Further to the north in South America the pattern is somewhat different as here there is a central valley running north-south, which is enclosed by the Andes to the east and a coastal range to the west. The major difference between the two regions is that in South America there is continuous land from 47 to about 55 °S, whereas these latitudes in the New Zealand region are largely occupied by sea with only scattered islands.
The capital of Chile, Santiago, and the northern tip of New Zealand lie at the same latitude, 34°S, but there is little correspondence between the plants of the two places. The central valley of Chile at this latitude is semi-arid and going northwards the aridity increases until perhaps the driest deserts in the world are reached in Peru. Going southwards, climates become moister and from about 40°S they are comparable in their range of temperature and moisture regimes to those of New Zealand in the same latitudes.
On the seaward slopes of the coastal ranges from about 40 to 47°S and ranging in altitude from 300 to 500 m there is a moist closed forest without Nothofagus. Similar forests are to be found on the eastern flanks of the coastal range and the western slope of the Andes, although in these cases the deciduous Nothofagus obliqua is present as an emergent. This forest type is comparable both vegetationally and floristically to the conifer broadleaf forest of New Zealand, although its conifers in fact are few and inconspicuous.
Compared with forests at similar latitudes in New Zealand there are fewer species overall in the Chilean forests as well as fewer vines and epiphytes. Shared tree and shrub genera are Podocarpus, Weinmannia, Laurelia, Pseudopanax and Griselinia. Shared epiphyte genera are Griselinia, Luzuriaga and the ferns Asplenium, Grammitis and Hymenophyllum. Chilean vines are not related to those of New Zealand. A sight which is strange to New Zealand eyes is the presence in this South American forest type of clumps of the bamboo Chusquea quila and the substitution for our page 234asteliad nest epiphytes of the bromeliad Fascicularia bicolor and for our ground astelias another bromeliad Greigia sphacelata. These bromeliads can be considered southern outliers of a family of specialised epiphytes that is richly developed in the Amazon rain forests.
Nothofagus forests are also extensively developed in southern South America.192 There are 10 species of Nothofagus altogether, 2 belonging to the N. menziesii group and 8 to the N. fusca group. Seven species are deciduous (both of the N. menziesii group species and 5 of the N. fusca group), generally in response to seasonal drought or cold.
Above the lowland forest on the seaward slopes of the coastal range there is first a zone of evergreen Nothofagus involving two species in succession, then below treeline the deciduous N. antarctica. This is similar to the Nothofagus cunninghamii/N. gunnii pattern in Tasmania. On the inner coast range and the western Andes the pattern is different. Above the lowland forest the zonation sequence is deciduous, evergreen, then deciduous Nothofagus.
The two deciduous species of the N. menziesii group, unlike N. menziesii itself, are tolerant of some seasonal drought and used to form forests in the central valley from 38 to 41 °S and further north at higher altitudes on the coastal range. Sophora microphylla and species of Aristotelia and Muehlenbeckia are sometimes associated with these species of Nothofagus.
Conifers associated with Nothofagus forests are Podocarpus species in the subcanopy, Saxegothea conspicua in the canopy and Araucaria araucana as an emergent near treeline in Nothofagus pumilio forests.
Going southwards in South America beyond New Zealand latitudes Nothofagus forest continues as the only type of forest to 55 °S or about the latitude of Macquarie Island. Only three species of Nothofagus are present in these latitudes — the evergreen N. betuloides and the deciduous N. pumilio and N. antarctica.
From about 52 to 55°S the sequence from west to east is: an open moorland with little forest; evergreen N. betuloides; deciduous N. pumilio and N. antarctica; and short tussock grassland on the eastern plains. It has been suggested that the lack of forest in the west is due to the cloudy and thus cooler climate.192 As conditions become drier and somewhat warmer to the east, evergreen Nothofagus forest can be supported, then deciduous Nothofagus forest and finally in the driest conditions of all only grass and shrubland. Alternatively, it has also been page 235proposed that the lack of forest in the east is due to the diorite rocks there which form a thin infertile soil.191
The moorlands are of particular interest as they have cushion bogs very similar ecologically to those of New Zealand and Tasmania and with related floras. Genera shared with New Zealand are Oreobolus, Gaimardia, Phyllachne, Donatia, Astelia, Drosera and Lepidothamnus. Lepidothamnus fonckii has a very similar growth habit to the pygmy pine (L. laxifolius) of New Zealand.
The short tussock grasslands of the eastern plains are similar in general appearance to those of the eastern South Island and also involve species of Festuca. The associated shrubs and herbs are mostly unrelated to those of New Zealand with the exception of small species of Discaria (matagouri in New Zealand).
Above treeline in southern South America are extensive alpine areas.193 There does not seem to be a well developed mountain shrubland zone as in some New Zealand mountains, although reduced, shrubby forms of Nothofagus antarctica may play that role. In poorly drained places cushion bogs similar to those already described occur, and on rocky sites fellfield with a predominance of cushion plants including large specimens of Azorella and the related Bolax. In the north where the Andes are at their highest there are extensive screes with some specialised plants similar to those of New Zealand, but not related to them.194
The southern tip of South America and the tip of the Antarctic Peninsula (Grahamland) of Antarctica are only about 800 km apart and are connected by a loop-like submarine ridge bearing several islands. Unlike adjacent South America, however the present day plants of Antarctica can be dismissed quite briefly. Moss cushions and lichens grow on exposed rock on the Antarctic Peninsula and some rocks free of ice on the main part of Antarctica, particularly in the strange 'Dry Valleys' near the Ross Sea. The only flowering plants are two small species on the Antarctic Peninsula: a grass, Deschampsia antarctica, and a chickweed relative, Colobanthus quitensis, both of which are also found at the southern end of South America and elsewhere.