Unraveling pre-Columbian occupation patterns in the tropical forests of French Guiana using an anthracological approach

International audienceIn Amazonia, a growing body of studies has shown that rainforests were affected by human occupation in many areas during pre-Columbian times, inducing changes in their floristic compositions. The northern part of Amazonia, and in particular the Guiana Shield, is much less studied, although past human occupations have also been documented in this region. Therefore, the actual impact of pre-Columbian societies on Guianan forests is still poorly known. Here we explore 12 sites in the dense forest of Nouragues, central French Guiana, ranging from a priori non-anthropogenic to clearly anthropogenic, using an anthracological approach. Soil charcoals were radiocarbon dated to assess the chronology of the past human occupations, and identified to determine shifts in vegetation cover. Our results show that two main periods of occupation can be distinguished on several sites in the Nouragues area: a first one between ca. 1,300 and 1,000 cal bp and a second one between ca. 600 and 400 cal bp. Charcoal identification reveals the presence of a secondary vegetation during this most recent period of occupation, as shown by the presence of pioneer and heliophilic taxa, suggesting that human activities induced and favored this kind of vegetation. The presence of valuable wood and edible species in the anthracological record could reflect selective exploitation of the former around dwelling areas and a concentration of the latter within anthropogenic sites. As shown by our anthracological results, all the sites which contained charcoal were once under forest cover, including those that are now covered by pseudo-bamboos or by liana forests. We therefore suggest that the type of human activity (e.g. dwelling or food production) may have had different impacts on the structure and composition of subsequent vegetation resulting either in anthropogenic forests or liana and pseudo-bamboo patches after land abandonment