Tropical Rain Forest and Climate Dynamics of the Atlantic Lowland, Southern Brazil, during the Late Quaternary

Abstract

Palynological analysis of a core from the Atlantic rain forest region in Brazil provides unprecedented insight into late Quaternary vegetational and climate dynamics within this southern tropical lowland. The 576-cm-long sediment core is from a former beachridge "valley," located 3 km inland from the Atlantic Ocean. Radiocarbon dates suggest that sediment deposition began prior to 35,000 14 C yr B.P. Between ca. 37,500 and ca. 27,500 14 C yr B.P. and during the last glacial maximum (LGM; ca. 27,500 to ca. 14,500 14 C yr B.P.), the coastal rain forest was replaced by grassland and patches of cold-adapted forest. Tropical trees, such as Alchornea, Moraceae/Urticaceae, and Arecaceae, were almost completely absent during the LGM. Furthermore, their distributions were shifted at least 750 km further north, suggesting a cooling between 3• C and 7• C and a strengthening of Antarctic cold fronts during full-glacial times. A depauperate tropical rain forest developed as part of a successional sequence after ca. 12,300 14 C yr B.P. There is no evidence that Araucaria trees occurred in the Atlantic lowland during glacial times. The rain forest was disturbed by marine incursions during the early Holocene period until ca. 6100 14 C yr B.P., as indicated by the presence of microforaminifera. A closed Atlantic rain forest then developed at the study site. C 2001 University of Washington.

Ancient associations of aquatic beetles and tank bromeliads in the Neotropical forest canopy

“…Thus, the estimated divergence between the populations of C. bimaculatus from the northern and southern Mata Atlântica (2.2-4 MYA; Fig. 2) is in agreement with phylogeographic evidence from pitviper populations in this region, showing a divergence of 3.8 MYA in the wake of orogenic events that caused changes in precipitation regimes and fragmentation of the Atlantic Forest (21,22). The genetic split between these lineages is supported by the fixation of subtle morphological differences.…”

Contrasting simulated past and future responses of the Amazonian forest to atmospheric change

“…Coral-based (Guilderson et al 1994) and foraminifera-based (Mix et al 1999) tropical sea-surface temperature reconstructions and analyses of noble gas concentrations in Brazilian groundwater (Stute et al 1995) show a maximum LGM tropical cooling of 5°C. Brazilian palynological data suggest a cooling of between 3 and 7°C (Behling & Negrelle 2001;Behling 2002). Kaolinite oxygen and hydrogen isotopes in palaeosols from the Colombian Bogotá basin suggest an LGM cooling of 5-7°C (Mora & Pratt 2001 temperatures up to 12°C lower during the LGM (Thompson et al 1995(Thompson et al , 1998, although this interpretation has since been reassessed to be more in the region of 3°C (for more details see Pierrehumbert 1999).…”

Late Pleistocene and Holocene Vegetation, Climate Dynamics, and Amazonian Taxa in the Atlantic Forest, Linhares, SE Brazil

“…Few studies based on palynology have demonstrated the permanence of the Atlantic Forest during the entire Holocene (e.g. Behling and Negrelle 2001). Most of these studies propose forest expansion or modification of forest species composition during the late Holocene, in response to inferred more humid climates.…”