VEGETATIONAL HISTORY OF A SITE IN THE CENTRAL AMAZON BASIN DERIVED FROM PHYTOLITH AND CHARCOAL RECORDS FROM NATURAL SOILS

Analysis of phytoliths and macroscopic charcoal from natural soils nea r Manaus, Brazil shows that the central Amazonian terra firme forest h as not been stable during the Holocene. Phytolith taxonomic compositio n and radiocarbon ages indicate that a closed forest has continuously existed in the area since at least 4500 yr B.P., but that forest compo sition and species abundance changed significantly sometime during the Holocene Epoch. There is no evidence that the vegetation experienced swidden cultivation. The distribution and dates of the charcoal in the soils indicate that forest fires between 1795 and 550 yr B.P. burned an area of about 200 hectares. Vegetational changes and fires appear t o be a result of climatic drying that may have affected large areas of the Amazon Basin over the past 5000 to 7000 years. Soil phytolith ana lysis is a promising tool for the study of environmental history in th e humid tropics and may reduce the previous dependence on lake and swa mp sediments, at least for the Holocene Epoch. (C) 1996 University of Washington.