Temperate Subantarctic Forests: A Huge Natural Laboratory
The Andean-Patagonian forests are the southernmost temperate forests in the world spreading over a thin strip at both sides of the Andes Mountains. This chapter introduces to a section of the book devoted to different species of these forests. Generalitie
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Temperate Subantarctic Forests: A Huge Natural Laboratory Paula Marchelli, Mario J. Pastorino, and Leonardo A. Gallo
2.1 Generalities and Particularities of the Andean-Patagonian Forests In the southern tip of South America, temperate subantarctic forests develop on both sides of the Andes mountain range. Known in Argentina as Andean-Patagonian forests, these ecosystems cover a narrow but long latitudinal strip, from 35° S (at Maule River, in Chile) to 55° S (in the southern extreme of the Tierra del Fuego archipelago, in Chile and Argentina). Their current geographic discontinuity from the other forests of South America is a remarkable feature, for which they have been considered a biogeographic island (Armesto et al. 1995). The sclerophyllous scrub and the high-Andean-steppe border the Subantarctic forests to the north; the Patagonian steppe, in Argentina, confines its development to the east, and the ocean marks its western and southern edges. This geographic isolation dates back to the Oligocene (about 23–33 My ago), when South America began to drift northward; before that, the continents of the southern hemisphere were connected as Gondwanaland (Markgraf et al. 1996). Since its origin in the late Cretaceous (ca. 90 My ago; Dettmann et al. 1990) till the separation of the continents, floristic interchange endured. This explains the relationships with other southern forests like those of Tasmania and New Zealand (i.e., disjunct distribution of genus like Araucaria, Aristotelia, Blechnum, Discaria, Lomatia, Nothofagus, Podocarpus, among others; Veblen et al. 1996). In addition, abundant neotropical elements characteristics of the “Yungas” in NE Argentina (e.g., Azara, Chusquea, Crinodendron, Drimys, Escallonia among others) reflect a history of recurrent connections with ecosystems of lower latitudes (Arroyo et al. 1995).
P. Marchelli (*) · M. J. Pastorino · L. A. Gallo Instituto de Investigaciones Forestales y Agropecuarias Bariloche (IFAB) INTA–CONICET, Bariloche, Argentina e-mail: [email protected] © Springer Nature Switzerland AG 2021 M. J. Pastorino, P. Marchelli (eds.), Low Intensity Breeding of Native Forest Trees in Argentina, https://doi.org/10.1007/978-3-030-56462-9_2
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The climate and topography along which these forests develop determine a wide variety of forest formations, soil types, and disturbance regimes, which greatly influence in species distribution as well as in their patterns of genetic variation. Then, the region is characterized by a high heterogeneity imposed by deep environmental gradients. First, the extension of these forests encompassing about 20° of latitude generate a gradient in the photoperiod with earlier start and later end of the daylight during the growing season toward the south, thus increasing day length. Also light quality and quantity differ across latitude due to seasonal variation in the distribution of semidarkness (twilight and moonlight) (Mills 2008) and the amount of solar ultraviolet radiation that decreases toward the
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