Holocene environmental changes in the Sao Francisco de Paula region, southern Brazil

Holocene paleoenvironments have been interpreted from a radiocarbon dated pollen and charcoal record of the Sao Francisco de Paula region on the southern Brazilian highland. Today the region is characterized by pastureland and small patches of disturbed Araucaria forest. The region receives 2450 mm per annum. This is the highest precipitation rate in southern Brazil. Studied surface samples represent the modern pollen analog of the anthropogenic influenced vegetation. Pollen analytical studies of the 84 cm long core, collected from a small basin with clay, organic matter and peat deposits, show that pollen and spores of the lower core section (84 and 46 cm depth) have been almost destroyed. This period between ca. 7500 and 4000 C-14 yr BP was too dry for conservation of pollen and spores in the basin. Climate must have been markedly drier than today during early and mid Holocene times. After 4000 C-14 yr BP, preserved pollen grains reflect wetter conditions than before and indicate the predominance of campos (grassland) vegetation with small areas of Araucaria forest in the study region. Forest expansion is documented since 1060 C-14 yr BP and expansion of Araucaria angustifolia trees itself since 850 C-14 yr BP. During the last 1000 yr, rainfall must have been much more intensive with no or only short dry periods such as the modem climate. The results confirm the vegetational and climatic changes documented front the Araucaria forest region of Santa Catarina and Parana State. Concentration and accumulation rates of carbonized particles are somewhat higher during the last 850 C-14 yr BP than before, indicating an increased fire frequency. (C) 2001 Elsevier Science Ltd. All rights reserved.