Ecosystems of Coastal Sand Plains

8.1 Restingas

8.1.1 Geological History and Vegetation Physiognomy

The Atlantic rain forest of Brazil is one of the 25 biodiversity hotspots in the world. In the south eastern state of Rio de Janeiro it is surrounded by various marginal plant communities, one of which is the restinga (Scarano 2002; Scarano et al. 2005a). It stands on quaternary terrains, i.e. sandy coastal plains between the rain forest and the sea (Martin et al. 1993; Scarano et al. 1997). The vegetation has its origins mostly associated to the rain forest and there are hardly any endemic plant species (Rizzini 1979; Araujo 2000). Migration from the Atlantic forest to the restingas was successful for ecologically plastic species, which were able to adjust to the more extreme and seasonal conditions imposed to the restinga habitats (Scarano 2002). Approximately 80% of the plant species occurring in the restingas of the state of Rio de Janeiro are also found in montane rainforests (Araujo 2000). Along the coastline of Rio de Janeiro the quaternary sandy deposits and dunes date mostly from the Holocene, having been established and re-established from 5000 to 3000 years BP, but further north under the influence of the Paraiba do Sul river in some areas marine sandy deposits date from the Pleistocene (120,000 years BP) and remained acquiring their final shape after a series of invasions and regressions of the sea during the Holocene (Martin et al. 1993).

The restingas comprise a mosaic of plant communities ranging from open, patchy formations to forests (Fig. 8.1A,B). Across a transect from the sea inland, successive sand dune ridges, vegetation islands on the sand plain and dune forests, and where the ground water table is high, open fresh water lagoons and swamp forests contribute to the physiognomy of the landscape (Reinert et al. 1997; Duarte et al. 2005). The very diverse plant communities found in therestingas are subjected to conditions as extreme as seasonal drought and oligotrophy on the one hand, and permanent flooding on the other (Henriques et al. 1986). Thus, the flora of a given restinga plant community often is very different from the flora of closely adjacent communities (Araujo et al. 1998).

Fig. 8.1A, B Restinga vegetation physiognomies. A Patchy restinga vegetation with vegetation islands viewed from a sand dune ridge with a dune forest in the foreground (dry restinga of Mas-sambaba, 22° 56' S, 42° 13' W). B Fresh water lagoon with a swamp forest in the background (at the intermediate restinga of the Jurubatiba National Park, 22°00' -22°23' S, 41°15' -41°45' W)

Fig. 8.1A, B Restinga vegetation physiognomies. A Patchy restinga vegetation with vegetation islands viewed from a sand dune ridge with a dune forest in the foreground (dry restinga of Mas-sambaba, 22° 56' S, 42° 13' W). B Fresh water lagoon with a swamp forest in the background (at the intermediate restinga of the Jurubatiba National Park, 22°00' -22°23' S, 41°15' -41°45' W)

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