LATE QUATERNARY VEGETATION AND CLIMATE DYNAMICS IN AMAZONIA AND CARBON STORGE CHANGES

Paleovegetational studies on the Amazon rain forest and savanna ecosystems in tropical South America indicate that vegetation has changed substantially during the late Quaternary. For instance, new pollen data of lacustrine sediment cores from Lagoa Grande and Lagoa de Cima of Serra Norte region in eastern Amazonia (Carajas, Pará State) document marked changes between rain forest and savanna during several glacial and interglacial periods. Results from Lagoa da Confusão in southeastern Amazonia (Tocantins State) show that during last glacial and early Holocene times the landscape was grass savanna and savanna woodland. The region was more forested by the stronger presence of gallery forest and Amazon forest trees during mid and late Holocene times. The paleovegetation infer a markedly drier climate (low precipitation rates and long annual dry season) during the glacial periods compared to the modern climate. Pollen data from the Colombian lowland in northwestern Amazonia show a marked Amazon rain forest expansion into the savannas of the Llanos Orientales, starting at 6000 14C yr B.P. A Holocene record from the eastern Amazon Basin indicate a marked change by the reduction of terra firme (unflooded) rain forests and an increase of várzea and igapó (seasonally flooded) forests since the last 2500 14C yr B.P. Marked modifications of the Amazon rain forest point to a significantly lower carbon storage by forests in tropical South America during glacial and early Holocene times than during the late Holocene.