Mise évidence par l'analyse anthracologique de la stabilité de la végétation sur le littoral brésilien pendant l'Holocène supérieur [Anthracological evidence of vegetation stability in the Brazilian littoral during the Late Holocene

Abstract

Anthracological studies earned out on six shell-mounds from Rio de Janeiro State (southeastern Brazilian coast) and one shell- mound from Santa Catanna State (southern Brazilian coast) showed that coastal vegetation present a marked resilience to climatic changes. In the southeastern Brazilian coast, the anthracological spectra is essentially the same between 5500 and 1400 yrs BP. Coastal sandy beach ridges were already colonized by the "restinga" (plant association charactenstic of the Brazilian coast) since at least the Middle Holocene. Depending on the site, the open restinga or the restinga forest were dominant. Forest and mangrove elements are present in all sites. In southern Brazil, no significant variation of the vegetal environment is recorded between 2500 and 1800 yrs BP. The studied site was established in the restinga environment, and the inland Atlantic Forest was probably situated quite far away. Mangrove vegetation was probably already absent from this region, which is presently under subtropical climatic conditions. No major changes of the vegetal ecosystem has taken place dunng the second part of the Holocene, notwithstanding many centuries of human occupation, pointing out to the fact that the vegetation was not greatly affected either by climatic or by anthropogenic perturbations. However, significant oscillations recorded in the mangrove vegetation from the Cabo Fno region (southeastern Brazil) might be related to climatic oscillations provoking lagoon salinity vanations. The stability of the mainland coastal vegetation is probably due to the edaphic character of coastal environments, particularly the restinga ecosystem, which is related to sandy soils and to the géomorphologie nature of sandy beach ndges. We propose that this environmental stability was a decisive factor in the sedentansation of the fisher-gatherer populations and in the maintenance of their sociocultural system.