Part II
The Mid Latitude Forests of Chile

The first part of this series (McQueen, 1976) dealt, briefly, with the distribution and general characters of the ten species of Nothofagus in South America; and in more detail with the vegetation of the Magellanic region around latitude 52° to 55° S. A paper by Weinberger (1973), translated in this issue, deals bioclimatologically with the commoner species of Nothofagus, mostly around latitude 38° - 41°. The present contribution aims to complement and introduce his work, particularly from a New Zealand point of view. Comments are drawn from field observations in Chile early in 1972, and from a selection of the literature. A notable and well illustrated background to Chilean vegetation is di Castri (1968).

A general diagram of the relation of Nothofagus to altitude and precipitation around latitude 40° S. (Table 1) is repeated here for convenience from Part I (McQueen, 1976). Species of wide distribution in mid-latitude Chile are N. obliqua, N. antarctica, N. alpina^* (syn. N. procera), and N. pumilio, which are deciduous, summer-green. The evergreens are N. dombeyi and N. nitida; and localised N. betuloides at its northernmost extension from its widespread southern distribution. There are three more restricted species, all occurring around latitude 35° S: N. glauca is restricted to a few localities around Concepcion. The remaining two species, N. alessandri and N. leoni, are of even more restricted distribution.

To the New Zealander, Chilean forests around latitude 40° S. present some familiarities and many more unfamiliarities; this is a character already outlined by Godley (1960). There are both Nothofagus-dominated forests and dicotylous Nothofagus-absent forests in both countries. Sharing Podocarpus, Nothofagus, Weinmannia, Laurelia, Pseudopanax, Aristotelia and thirty-nine families with New Zealand the lowland Chilean forests are different, in the relation of species composition to structure, from New Zealand forests. One most notable difference is the understorey of the bamboo, Chusquea, in forests up to about 1,000 m altitude. Its density, in the dozen or so species found, is an important factor in prevention of regeneration when forest management is practised. page 234

Table 1
Summarised forest distribution, across Chile and Argentina at about latitude 40° S., to show distribution of deciduous and evergreen trees. Altitudes on vertical scale are approximate. All species of Valdivian rainforest are evergreen, except N. obliqua. (From Weinberger, 1973 (coast range), Dimitri (1962) and personal observations.)

It appears that Nothofagus in South America is at a competitive advantage over the majority of Chilean conifers. Reasons may be found in its biological characters, such as deciduousness, and the ability of some species to regenerate vegetatively, and apparently easier seed dispersal (McQueen, 1976). There is a marked contrast, at least on younger soils, with New Zealand, in the relation between the two groups of trees. Chilean Podocarpus plays a sub-canopy role in Nothofagus forest and dicotylous forests. Saxegothea conspicua, in the same family, will reach the upper canopy level with Nothofagus and occasionally will form pure stands (Schmithusen, 1960). Thus S. conspicua is the only tree equivalent in its structural position as a canopy or emergent tree to New Zealand species of Podocarpus and Dacrydium. The only representative of Dacrydium in Chile is a prostrate swamp plant slightly bigger than Dacrydium laxifolium. It is, however, ecologically equivalent to Dacrydium bidwillii.

Two members of the Cupressaceae in Chile are Pilgerodendron uviferum and Fitzroya cupressoides, both found growing in poorly drained soils and even in peat swamps. The first is restricted to such sites and extends southwards to the western part of the Magellanic region (McQueen, 1976). The second species, F. cupressoides, does not grow as far south, but as well as growing in bogs it will grow on very infertile soils at altitudes up to 1,000 m on the Coastal Range. These two species behave similarly to Dacrydium colensoi and Dacrydium intermedium in New Zealand. Also in the Cupressaceae in Chile is Austrocedrus (formerly Libocedrus) with one species, A. chilensis, whose ecology is different from its New Zealand relatives (L. bidwillii, L. plumosa), both of high precipitation forest areas. The Chilean species is a plant growing to the north of Nothofagus forest on the Andes as rainfall decreases northwards. It also occurs in Argentina in the rain shadow produced by the Andes mountains, where it is accompanied by N. antarctica, the most drought tolerant of South American Nothofagus (Fig. 1). A. chilensis also occupies drier intermontane basins in Chile, west of the Andes.

A similar contrast is found in the Araucariaceae: New Zealand's Agathis australis is northern, almost sub-tropical; Chile's Araucaria araucana is a high altitude species near and above the N. pumilio treeline (Fig. 2).

Hybridisation may be as prevalent among Nothofagus in South America as in New Zealand. Forms seen by the author included a N. obliqua with N. glauca characters, at the north of the Nahuelbuta National Park at 37° 47′ S, and the apparent variety N. obliqua var. macrocarpa of the Cerro Roble at 33° S. Even the variety in leaf size of N. obliqua s.s. collected further south suggests a hybridism in two representatives of the N. ‘menziesii’ pollen group in South America. By contrast, in the N. ‘fusca’ group representatives, among the deciduous species the common, and often adjacent, N. antarctica and N. pumilio retain their own characters. Amongst the evergreens of page 236

Fig. 1 (left): Austrocedrus chilensis east of the Andes near Lago Meliquina, Argentina, 40° 20′ S, at 1,000 m altitude. A few stunted Nothofagus antarctica accompany it in this dry country.
Photo: D. R. McQueen
Fig. 2 (right): Araucaria araucana over the bamboo, Chusquea, and Nothofagus antarctica at 1,200m, Paso Tromen, Chile-Argentina, 39° 41′ S. Photo: D. R. McQueen

this group, N. dombeyi and N. betuloides, although very similar, and overlapping slightly in range at about 40° - 41° S, are always clearly distinguishable.

Returning to characters of the South American representatives of the N. ‘menziesii’ group: N. obliqua and N. glauca, these deciduous species have a different ecology from the evergreen N. menziesii of New Zealand. N. obliqua and N. glauca are lowland, and northern in distribution, tolerating a degree of summer drought.

The implications to paleoecology of the N. ‘menziesii’ pollen group are important. This pollen has existed in New Zealand since the Cretaceous (Couper, 1960) and has been interpreted in pre-Pleistocene times as an indicator of cooler climates (McQueen et al., 1968). Such opinions may need revising if this group were, in the Cretaceous and Tertiary, represented in New Zealand by more thermophilic species of the group, such as exist today in South America and Australia.

Nothofagus in Chile around Latitude 40° S

The Deciduous Nothofagus

Nothofagus obliqua

Nothofagus obliqua (Fig. 3) is deciduous and is capable of vegetative reproduction after damage by fire. It was formerly widespread in the central valley of Chile from 38° S near sea level to about 41° S (Clarke, 1964). N. obliqua does extend further north at increasing altitude and is the northernmost Nothofagus found in Chile, recorded in its form N. obliqua var. macrocarpa as far north as the Cerro Roble (33° S), part of the Coastal Range above the truly Mediterranean climate of Central Chile. At this locality the present author saw only its lower limits, very deformed trees in gullies forming tongues down into the Mediterranean scrub. This scrub contained mostly species quite unknown in New Zealand, but did include, however, Sophora macrocarpa and Muehlenbeckia hastata.

In its higher altitude northern distribution at about 700 m to 800 m Nothofagus obliqua exists as a distinct ‘form’ recognised by Chilean

Fig. 3: Nothofagus obliqua 10m high with Sophora microphylla and Aristotelia maqui, in a low rainfall basin, Rio Truful Truful, Chile, 420m altitude, lat. 38° 40′ S. The Nothofagus is here close to its aridity limit, and typically much taller with adequate precipitation.
Photo: D. R. McQueen

page 238

Fig. 4: Nothofagus antarctica at 1,300m in the Nahuelbuta National Park, Chile (lat. 38° 47′ S). Araucaria araucana is in the background.
Photo: D. R. McQueen

botanists. This particular form was seen on the approaches to the Nahuelbuta National Park on the Coastal Range at 37° 47′ S. It was in an area overgrazed and damaged by felling and lopping of trees for charcoal burning. These trees were responding in the same way as would a European tree and showed a surprising similarity in form and in surrounding degraded landscape to some of the more southern deciduous oaks of the Mediterranean basin. Higher altitude stands of N. obliqua, up to 1,350 m altitude on the same range, were growing on flat ground, frequently frosty, as described by Weinberger. The inclusion of this area within the National Park and protection from grazing had resulted in very good regeneration by seed.

It is in its main lowland distribution from 38° - 41° S that N. obliqua attains its best growth, up to 40m height. As shown in Weinberger (Fig. 5) N. obliqua ascends only to about 500m altitude on the drier eastern flanks of the coastal range at latitude 40° S. It is found to a similar altitude in the Andes where it frequently grades into Valdivian rainforest with N. alpina as an emergent.

In the Central Valley most of the forests of N. obliqua have been converted to farm land but the vegetative regrowth of N. obliqua has allowed scattered trees to remain, giving a very European appearance to the landscape.

The occurrence of summer frosts on the plains occupied by Nothofagus obliqua is ample evidence of cold air drainage off the page 239

Fig. 5: Nothofagus alpina on the east of the Cordillera Peladar, Chile. Altitude 400m; latitude 40° 10′ S.
Photo: D. R. McQueen

Andes and, to a lesser extent, off the Coastal Range. Allowing more extremity in frost in winter, it appears that N. obliqua as a deciduous tree is well suited to such sites and to the higher altitude flat sites described by Weinberger.

Edaphically (Wright, 1965), N. obliqua is associated with the trumao soils, formed from volcanic ash with allophane as a dominant clay. These soils are characterised by friability to depth and high water retention throughout but nevertheless only a limited depth is penetrated by tree roots.

In the Central Valley the contrasting poorly drained, reworked volcanic ash nadi soils are the site for trees of lower fertility demand such as Nothofagus nitida, and formerly stands of very large Fitzroya cupressoides.

Nothofagus antarctica

Nothofagus antarctica rarely grows to more than 10m high and is multi-branched, deciduous as it N. obliqua. As described by Weinberger, it behaves in a similarly plastic way in middle latitude page 240

Fig. 6 (left): Nothofagus pumilio just below treeline at 1,400m, Cerro Chepalco, Argentina. Latitude 40° 20′ S.
Photo: D. R. McQueen
Fig. 8 (right): Nothofagus dombeyi, Antillanca mountain road, Chile. The bamboo, Chusquea sp., beneath is 5-6m high. Altitude 800m; latitude 40° 40′ S.
Photo: D. R. McQueen

Chile as it does in Magellanic Chile, occupying at lower altitudes poorly drained nadi soils (Wright, 1965). It descends in cold air drainage sites to 900m or less, and as in the far south forms a subalpine scrub above the N. pumilio treeline on both flanks of the Andes, frequently in association with Araucaria araucana on the Andes and on the Coastal Range (Fig. 4). Weinberger rightly considers N. antarctica as a plant with a wide tolerance of thermal and atmospheric saturation ranges. He further draws a very interesting comparison involving the occurrences of N. antarctica in the Andes, where it occupies valley flats above about 900m. Here the valley floor is occupied by N. antarctica, and other Nothofagus species are located in the zone above the occurrence of heavy frosts. Weinberger points out that similar valley bottom sites in Magellanic Chile would be occupied by N. pumilio. The general temperature regime of the Magellanic area is considerably colder than that of the Andes, particularly during the growing season. Weinberger suggests that the virtually constant westerly winds of the Magellanic area cause far greater mixing of air masses and prevent cold air page 241

Fig. 7: Nothofagus pumilio and bamboo, Chusquea sp., on andesitic ash, Antillanca mountain road, Chile. Altitude 950m; latitude 40° 20′ S.
Photo: D. R. McQueen

drainage during the summer, thus allowing the growth of the less frost tolerant N. pumilio on many of the flat areas around Punta Arenas. However, the present author's observations around Puerto Natales (latitude 52° S), where there are extensive areas of N. antarctica in valley bottom flats with N. pumilio on the slopes, suggests that further away from the more oceanic conditions around the Straits of Magellan, summer frost may play an equally important role in the distribution of extensive stands of N. antarctica in valley bottoms in the Magellanic area.

Nothofagus alpina

Nothofagus alpina (Fig. 5), which occurs above N. obliqua on the Coastal Range and the Andes, is likewise deciduous, intermingling with N. obliqua lower down and with the evergreen N. dombeyi above. In common with N. obliqua, N. alpina has vigorous vegetative reproductive habits and one stand seen in the Andes originated from trees engulfed in 60cm of basaltic ash in about 1870. It then resprouted, was felled about 1945, and resprouted again. Excavation showed that the regeneration was from the root collar and from root suckers.

Nothofagus pumilio

Nothofagus pumilio, as in Magellanic Chile, forms the treeline on the Andes, the small-crowned deciduous trees looking, in leaf, page 242 very like N. solandri var, cliffortioides (Fig. 6). The forest floor at altitude is generally herbaceous and open but at lower altitudes in the N. pumilio zone the bamboos, Chusquea spp., are, to New Zealand eyes, odd companions to Nothofagus (Fig. 7).

It is in the upper parts of the N. pumilio zone that Araucaria araucana occurs in large but rather isolated areas between 38° and 40° S on the Andes and in the Nehuelbuta region of the Coastal Range at about latitude 37° S. This erect-growing conifer is either emergent above the N. pumilio canopy or above a matrix of low N. antarctica scrub above the N. pumilio treeline (Fig. 2). Apparently the robust yet flexible branches of Araucaria shed the snow that is the cause of the treeline krummholz of N. pumilio (Eskuche, 1973), thus giving a double treeline.

The Evergreen Nothofagus

Nothofagus dombeyi

N. dombeyi (Fig. 8) is a tree climatically of a very wide tolerance, concentrated in Chile in climates of oceanic tendency, but widespread there on to sites of edaphic stress, such as the nadi soils, moraines and lahars. It will thrive as a coloniser even on such ‘new’ sites in areas exposed to the dry easterly wind, the puelche, whose temperature extremes outdo most Canterbury nor'-westers (see Fig. 8 of Weinberger).

It is in Argentina that N. dombeyi reaches its fullest and most continuous extent. On the rain shadow eastern flank of the Andes this species descends from the sub-alpine N. pumilio forests down to the semi-arid N. antarctica and Austrocedrus chilensis forests of the western Patagonian plains.

In its tolerance of the rain shadow climate of the east of the Andes and in many of its attributes in the higher rainfall areas of Chile N. dombeyi appears remarkably similar in its ecology to N. solandri var. cliffortioides, of New Zealand, but N. dombeyi does not ascend to the treeline. At its easternmost limit of precipitation in Argentina N. dombeyi is found only on relatively deep and friable volcanic ash soil. Rocks from which the ash has been eroded and recent shingle fans are occupied by Austrocedrus chilensis, which as well grows erect, beyond any continuous cover of N. antarctica.

Nothofagus nitida

Nothofagus nitida (Fig. 9), the other evergreen species treated in detail by Weinberger, is found only on the Coastal Range and to the south of Puerto Montt in the areas where the chain of the Andes is near the sea. N. nitida is a species of quite narrow ecological tolerance to temperature and moisture fluctuations. It is most similar in its growth and in its favoured habitats to Nothofagus menziesii in New Zealand, but does not reach the alpine treeline.

Although Weinberger had only one meteorological station for N. betuloides, it may be considered that N. betuloides, being predominant page 243

Fig. 9: Nothofagus nitida, Cordillera Peladar, Chile. Altitude 700m; latitude 40° 10′ S.
Photo: D. R. McQueen

south of about latitude 48° S, is an ecological vicariant of N. nitida. They both occupy very similar climatic conditions.

There remain three species not studied in detail by Weinberger; first N. alessandri, a species of very limited distribution (Clarke, 1964) around 35° S. The present author (McQueen, 1976) in Table 1 ascribed this species on published evidence to the Nothofagus ‘brassi’ pollen group, but later work has shown that N. alessandri belongs to the N. ‘fusca’ pollen group (letter N. T. Moar p. 266).

The second species, although apparently formerly of wide distribution, is now limited to stands near Concepcion. This is N. glauca, a species apparently similar ecologically to N. obliqua.

A third species which was not mentioned in my previous contribution, N. leoni, is again of a very limited distribution in the province of Maule (35° 40′ S) and is a deciduous tree with leaves intermediate in size between N. alessandri and N. glauca (F. Schlegel S. pers. comm.).

Acknowledgements

Visits to these forests accompanied a project on N. antarctica generously financed by Victoria University of Wellington, the N.Z. University Grants Committee and by Le Ministère des Affaires Etrangères, Paris. I also wish to express my gratitude to Dr. F. Schlegel S., Director of the Instituto de Silivicultura y Reafforestacion page 244 of the Universidad Austral de Chile, to Dr. B. Muller-Using, then at the same Institute, and their colleagues for their help and invaluable guidance in the forests of the area. My thanks are also due to Dr. P. Hajek and his colleagues at the Universidad Catolica de Chile, Santiago.

Mr. Olaf John, of Wellington, reproduced from colour slides all photographs in both Parts I and II of this series and merits my particular thanks.

References

di Castri, F., 1968: Esquisse écologique du Chili. Biol. de l'Amerique Australe IV: 7-52. Centre Nationale de la Récherche Scientifique, Paris.

Clarke, D., 1964: The Forests of Southern Chile and the Argentine. Quart. Journ. Forestry: 20-31, 120-134.

Couper, R. A., 1960: New Zealand Mesozoic and Cainozoic plant microfossils. N.Z. Geological Survey Pal. Bull. 32: 87pp.

Eskuche, U., 1973: Estudios fitosociologicos en el norte de Patagonia. Phytocoenologia 1 (1): 64-113.

Godley, E. J., 1960: The botany of southern Chile in relation to New Zealand and the Subantarctic. Proc. Royal Soc. B, 152: 457-475.

McQueen, D. R., Mildenhall, D. C., Bell, C. J. E., 1968: Paleobotanical evidence for changes in the Tertiary climates of New Zealand. Tuatara 16 (1): 49-56.

McQueen, D. R., 1976: The ecology of Nothofagus and associated vegetation in South America. Tuatara 22 (1): 38-68.

Schmithusen, J., 1960: Die Nadelholzer in den Wald-gesellschaften der Sudlichen Anden. Vegetatio 9, 4-5: 313-327.

Weinberger, P., 1973: Bezichungen zwischen mikroklimatischen Faktoren und naturlicher Verjungung araukano-patagonischer Nothofagus Arten. Flora 162, 8: 157-179.

Wright, A. C. S., 1965: The Volcanic Ash Soils of Chile. F.A.O. Rome, Report 2017: 201 pp.