This seminar is hosted by the Oxford Centre for Tropical Forests

Abstract: One of the most remarkable features regarding the floristic distribution in the Amazonian lowlands are the numerous patches of open (savanna-like) vegetation in sharp contrast with the dense rainforest. Their occurrence in such a humid ecosystems is intriguing and several hypotheses (e.g. contrasts in topography and lithology, changes in soil nutrients and structure, or dry climatic episodes during the last glacial) have been proposed.

This talk will focus on the presentation of a new geomorphological and geological dataset based on the integration of several remote sensing techniques with the sedimentary record and the geochronology of Late Pleistocene-Holocene deposits from northern Amazonia, which contains the largest savanna patches of the region. In addition to helping reconstruct the evolution of the largest fluvial drainage basin on Earth, this approach provided a large volume of information demonstrating that savanna patches are not randomly distributed, but they are directly linked to paleomorphologies representative of past landscapes that contrast with the modern tributary network, demonstrating that their presence is largely controlled by the evolution of the physical environment. A series of plant successions caused by disturbances in the physical environment has long been predicted by the ‘seral change’ in the general theory of ‘climax’ vegetation communities. However, relating vegetation patterns to the late Quaternary depositional dynamics is a new approach not yet applied for understanding large-scale floristic dissimilarities in the Amazonia lowlands. In a large scale, the paradox of savanna intermingled with rainforest might be resolved through the understanding of the depositional dynamics in space and time and of its causative factors, in this area mostly consisting of tectonic reactivations.

Speaker: Professor Dilce Rossetti, Geologist, Brazilian National Institute for Space Research-INPE

Biography: Dilce Rossetti is a geologist at the Brazilian National Institute for Space Research-INPE, São Paulo, acting also as a researcher and scientific advisor of the Brazilian National Science Council-CNPq, Professor in the graduate school of São Paulo State University-USP, and vice-president of the International Association of Sedimentologist-IAS. DPhil - University of Colorado at Boulder. Researcher at the Goeldi Museum in Belém from 1988 to 2004.

Dilce has specialized in the reconstruction of Amazonian landscape through time, particularly focusing on the late Quaternary time, her main interest has been to integrate remote sensing techniques with the sedimentary record and the biological data aiming analyze origin, evolution and distribution of the Amazonian biodiversity.