Bioclimatic and Phytosociological Diagnosis of the Species of the Nothofagus Genus (Nothofagaceae) in South America

International Journal of Geobotanical Research, Vol. nº 1, December 2011, pp. 1-20 Bioclimatic and phytosociological diagnosis of the species of the Nothofagus genus (Nothofagaceae) in South America Javier AMIGO(1) & Manuel A. RODRÍGUEZ-GUITIÁN(2) (1) Laboratorio de Botánica, Facultad de Farmacia, Universidad de Santiago de Compostela (USC). E-15782 Santiago de Com- postela (Galicia, España). Phone: 34-881 814977. E-mail: [email protected] (2) Departamento de Producción Vexetal. Escola Politécnica Superior de Lugo-USC. 27002-Lugo (Galicia, España). E-mail: [email protected] Abstract The Nothofagus genus comprises 10 species recorded in the South American subcontinent. All are important tree species in the ex- tratropical, Mediterranean, temperate and boreal forests of Chile and Argentina. This paper presents a summary of data on the phyto- coenotical behaviour of these species and relates the plant communities to the measurable or inferable thermoclimatic and ombrocli- matic conditions which affect them. Our aim is to update the phytosociological knowledge of the South American temperate forests and to assess their suitability as climatic bioindicators by analysing the behaviour of those species belonging to their most represen- tative genus. Keywords: Argentina, boreal forests, Chile, mediterranean forests, temperate forests. Introduction tually give rise to a temperate territory with rainfall rates as high as those of regions with a Tropical pluvial bio- The South American subcontinent is usually associa- climate; iii. finally, towards the apex of the American ted with a tropical environment because this is in fact the Southern Cone, this temperate territory progressively dominant bioclimatic profile from Panamá to the north of gives way to a strip of land with a Boreal bioclimate. Argentina and Chile. However, south of the 30th parallel, This parallelism between the climatic sequences in the grosso modo, more variable climatic conditions arise. northern and the southern hemispheres presents a signifi- Surrounding Río de La Plata there is an area with a Tem- cant difference, however. As a result of the increasingly perate bioclimate forming a large semicircle facing the narrower strip of land at the southern tip of South Atlantic ocean and extending from the southernmost America, genuinely continental bioclimates never arise outskirts of Brasil, Uruguay and the province of Buenos- and all the variants of the Mediterranean, Temperate or Aires to the Colorado river mouth. In addition, beyond a Boreal climates range from hyperoceanic to oceanic long and extremely arid strip of land –the so-called “Arid subtypes. Diagonal”– extending from Perú to the Argentinian The singular character of the flora of the American Patagonia, there is a territory with not only peculiar flora Southern Cone has been squarely captured in the des- and vegetation but also with ecosystems adapted to the 3 criptive name of “biogeographical island” frequently large macrobioclimatic categories (other than the Tropi- given to the Chilean territory (ARMESTO ET AL. 1996). cal one) according to RIVAS-MARTÍNEZ (1993, On-line): The Atacama desert to the north, the impressive and Mediterranean, Temperate and Boreal continuous Andean Cordillera to the east, the subantar- This territory shows, on a much smaller scale, the ctic ice to the south and the Pacific Ocean to the west same macroclimatic series as seen in the northern hemis- have induced a scenario where the plant biota has phere, from the Palaeotropical Kingdom to the North evolved independently from the rest of the continent Pole: i. a desert or hyperarid zone (where the change since the time when Australia and Antarctica separated from a Tropical to a Mediterranean bioclimate takes from the American Southern Cone and the Andean ba- place); ii. a zone with a variably and progressively more rrier emerged in the Eocene-Miocene epochs (STUESSY humid, Mediterranean climate, to such an extent that the & TAYLOR, 1995). increasing summer rains from the Pacific Ocean even- Correspondence: Javier Amigo. Laboratorio de Botánica, Facultad de Farmacia, Universidad de Santiago de Compostela (USC). E- 15782 Santiago de Compostela (Galicia, España). Phone: 34-881 814977. E-mail: [email protected] ISSN: 2253-6302 print/ISSN 2253-6515 on line ©Editaefa DOI: 10.5616/ijgr110001 2 J. Amigo & M. A. Rodríguez-Guitián This territory, the Austro-American Subkingdom in Background the biogeographical mapping of RIVAS-MARTÍNEZ & Given the significant contribution of the Nothofagus NAVARRO (1994) and RIVAS-MARTÍNEZ ET AL. (2011), species to the Chilean and Argentinian temperate forests, exhibits a flora with a high endemicity rate, as high as there is no shortage of studies dealing with the ecological 46% at species level (MARTICORENA 1991). The Notho- and dynamic features of the natural populations. This is fagus genus is one of the most outstanding groups in this particularly true not only of the timber-yielding species peculiar flora and links the southern half of Chile with growing in rainy, temperate areas (for a summary, see the Holantarctic Floristic Kingdom (sensu TAKHTAJAN VEBLEN ET AL. 1996), but also of species occurring in the 1986). The genus is included in the monotypic Nothofa- Chilean mediterranean territory (DONOSO 1996). Since gaceae family and in the order Fagales, whose morpho- all these species are of great interest for the timber in- logical similarities with the Fagaceae of the northern dustry (DONOSO 1998), the quantitative aspects of their hemisphere earned them the geobotanical name of autoecology (DONOSO 2006), genetic variability (DONO- “southern beech trees”. SO ET AL. 2004), ecophysiology (ALBERDI ET AL. 1985; The Nothofagus genus with its 36 known species has ALBERDI 1996) and even palaeohistory (MARKGRAF ET been considered as one of the key genera in showing the AL. 1996) have already been studied. migration and evolutionary patterns of the southern The phytosociological behaviour of each of these hemisphere biota. The genus is of great interest for pa- Nothofagus species has also been studied. Since laeobotany on account of three relevant features: 1) it is OBERDORFER (1960) clearly established the syntaxono- made up of tree species which are usually important mical arrangement of the mediterranean and temperate components of the climatophilous forests; 2) the fruit has vegetation of Chile, some later contributions by Argen- low dispersal ability which largely limits its propagation tinian authors, such as ESKUCHE (1968, 1969, 1973, 1999, to land routes; and 3) there are abundant fossil records of 2002) or ROIG (1998), and Chilean authors, such as the genus, and particularly of its unmistakable pollen PISANO (1970, 1977), DOLLENZ (1982a), RAMÍREZ ET AL. grains (HILL & DETTMANN, 1996). (1983, 1989), SAN MARTÍN ET AL. (1984, 1991b, 1991c), There are 10 species belonging to the Nothofagus ge- have described particular associations for clearly-defined nus which can be found in the South American extratro- territories. However, a great variety of names of associa- pical territory (either Mediterranean, Temperate or Bo- tions (RAMÍREZ ET AL. 1987; SAN MARTÍN & RAMÍREZ real). They are the following (the order corresponds more 1987), communities (GAJARDO 1994) or vegetation belts or less to the occurrence of the species from north to (LUEBERT & PLISCOFF 2006) have been published in south): wide-ranging studies dealing with large territories but no 1. Nothofagus macrocarpa supportive relevés have been published to adequately 2. N. glauca support those names or has there been adequate nomen- 3. N. alessandri clatural validation. To avoid possible misinterpretations, 4. N. obliqua there is urgent need of a careful syntaxonomical revision 5. N. alpina using the International Code of Phytosociological No- 6. N. dombeyi menclature (WEBER ET AL. 2000). 7. N. nitida This paper provides a description of the phytosocio- 8. N. betuloides logical behaviour of the South American Nothofagus 9. N. pumilio species and co-relates their communities with the biocli- 10. N. antarctica matic belts suggested by RIVAS-MARTÍNEZ (1993, On- line). The species can also be arranged to reflect the 3 large ecological groups involved (RAMÍREZ 1987): i. large- leaved, deciduous species peculiar either to the “Medite- Brief description of the territory rranean region” or to areas with a submediterranean-like In Chilean territory the Nothofagus forests extend summer (species 1 to 5); ii. perennial species associated right across the country, from latitude 33° south to Tierra with the “Valdivean region” (6 to 8); and iii. small- del Fuego (Figure 1). Meanwhile, on the other side of the leaved, deciduous species peculiar to the “Subantarctic Andean Cordillera, in Argentina, their presence is res- region” (9 and 10). Although some publications by Chi- tricted to a narrow strip of land that originates at latitude lean authors support the existence of an eleventh taxon, 35° south and runs parallel to the impressive Andean viz., Nothofagus leonii Espinosa, considering it a forest range up to the south apex of the continent. In Chile, in species on account of its distinct morphological features addition to the Andes, there is the so-called Cordillera de (RAMÍREZ ET AL. 1997) and auto-ecological profile la Costa, a group of mountain ranges running parallel to (DONOSO 2006), in all cases they have recognized its the Pacific coast. This cordillera is much older than the hybrid character. The taxon is the result of the natural Andes and, consequently, the peaks are much lower as a crossing of N. obliqua and N. glauca, and has obviously result of long-term erosion. been found where these two species overlap. For this In the land strip between latitudes 32° and 37° south reason we have not included it in our study nor have we the Andean Cordillera has imposing peaks. These are the included other hybrids that do not always have an ortho- Mediterranean Andes, with peaks above 5,000 and 6,000 dox name, despite having begun to be recognized and masl (for example, Aconcagua, 6,959 m). Going south, described in the last decades (DONOSO & ATIENZA 1984; between latitudes 37° and 41° south, we find the so- DONOSO ET AL.

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