Vegetation stability in the Brazilian littoral during the late holocene - anthracological evidence

Resumo

Anthracological studies carried out on six sambaquis from Rio de Janeiro State (southeastern Brazilian coast) and one sambaqui from Santa Catarina State (southern Brazil) showed that coastal vegetation presents a marked resilience to climatic changes. Charcoal samples were collected from vertical profiles along the entire sambaqui height and examined under reflected light microscope. 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 resting vegetation since at least the Middle Holocene. Depending on the site, the open resting or the resting forest are 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 resting 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 during 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 Frio region (southeastern Brazil) might be related to climatic variations, is probably due to the edaphic character of coastal environments, particularly the resting ecosystem, which is related to sandy soils and to the geomorphologic nature of sandy beach ridges.