Charcoal in the soils and paleofires in distinct regions of Brazil
by
Susy Eli M. Gouveia
Centre for Nuclear Energy in Agriculture (CENA), Box 96, 13400-970, Piracicaba/SP, Brazil
Coauthors: L.C.R. Pessenda (Center for Nuclear Energy in Agriculture CENA - University of São Paulo, Brazil), M.-P. Ledru (University of Montpellier 2, Institut des Sciences de l’Evolution, France), R. Aravena (University of Waterloo, Canada), A. S. Ribeiro (Federal University of Sergipe, Aracaju, Sergipe, Brazil) and J. A. Bendassoli (CENA, São Paulo, Brazil)

Charcoal fragments present in Brazilian soils record natural fires, being probably the result of dry periods and suggesting the occurrence of climatic changes in the past. However, the role of anthropogenic activities in prehistoric fires can’t be discarded. The pattern of charcoal distribution in the soils varies with region. The southeastern area shows little burning activity in the late Pleistocene and early Holocene, followed by millennia of greater activity (6000-3000 C-14 yr BP). The intensity of biomass burning in the last 1000 years appears low compared with that of the middle Holocene and seems more similar to the early Holocene. The northeastern area shows few charcoal amount, however C-14 dates cover most of the Holocene. In the southern Amazon Basin C-14 dates also cover most of the Holocene, with two maxima concentrations of charcoal around 7500-6000 BP and ca. 2000 BP.

Palaeoclimatic interpretations from charcoal distribution in the soils, soil C-13/C-12 analysis, anthracology and palynology show a great coherence. Palaeoenvironmental studies carried out in the central, southeastern and south regions of Brazil indicate a probable presence of dry climate during the late Pleistocene and increase of humidity during the middle Holocene. Modern climatic conditions became established after ca. 3000 BP. Studies developed in the NE Brazil and in the south and central Amazon region indicate a more humid phase from late Pleistocene to the early Holocene, a presence of a drier climate from ~9000 yr BP to 4000-3000 yr BP, confirmed by the occurrence of paleofires at the study sites, and the return to a more humid phase and probably similar to the present climate from 4000-3000 yr BP to the present. The difference among the regions may be connected with seasonal movements of the Inter-Tropical Convergence Zone (ITCZ).

Date received: October 30, 2004