AMAZONIA RAIN-FOREST FIRES - A LACUSTRINE RECORD OF 7000 YEARS

Although human influence dominates present-day Amazonian rainforest fi res, old charcoal fragments, buried in the soils or in lacustrine sedi ments, confirm that fire has played a major role in the history of Ama zonian forests. These fires may have influenced the present-day divers ity and structure of the rainforest and if these fire-favorable events of the past reoccur there may be drastic consequences for the future of the Amazonian forests. Detailed studies of Carajas lake sediments p ermit identification of these past fire events, through microscopic ob servations of small charcoal fragments. They also permit, through radi ocarbon dating, a better definition of their timing and make it possib le to relate them to past paleo-environmental and paleoclimatic condit ions. The paleodata indicate that fire events were concomitant with sh ort dry climate episodes whose frequency of occurrences has varied dur ing the last 7000 years. These dry events may be related to past clima te conditions observed in different regions of tropical South America.