The southern Brazilian tropical forest during the penultimate Pleistocene glaciation and its termination

Abstract

To describe the composition of the penultimate glacial Brazilian Atlantic forest, we analyzed pollen, charcoal and diatoms deposited in the section from 871 to 1400 cm of core CO14 drilled in the Colônia basin in southeastern Brazil. The landscape was characterized by a cool grassland with three conifer genera: Araucaria, Podocarpus and Ephedra. Total arboreal pollen frequency did not change during the transition from glacial to interglacial conditions. Changes in Podocarpus frequency and concentration showed out‐of‐phase responses with austral summer insolation at an orbital scale while, at a millennial scale, both northern and southern hemisphere ice volume controlled the interplay between positions of the Inter‐Tropical Convergence Zone and South Tropical Front (STF), which in turn defined the latitudinal distribution of rainfall. The disappearance of Podocarpus and the decrease of Araucaria observed between ~167 and 160 ka were related to a dry interval which was not observed elsewhere. During Termination II a progressive decrease in conifer pollen taxa was in phase with a southward shift in the STF and increase in Atlantic sea surface temperatures. Our results show that southern hemisphere conifer distribution is strongly linked to austral summer insolation and winter precipitation and will be threatened by the southward expansion of the summer rainfall boundary.

Long-term adjustment of the South America Atlantic Forest to atmospheric carbon dioxide concentration

“…The higher (~ 30.4) ACL values during late MIS 6 are consistent with the dominant presence of grassland vegetation composed of an association of Poaceae, conifers (Araucaria and Podocarpus), and shrubs 30 as the ones noted today at high elevation in the state of Paraná (southern Brazil) 54 . Toward the Last Interglacial, the vegetation composition uctuated with the same species as during the penultimate glacial, except for the Poaceae, which decreased sharply, allowing shrubs to expand 55 . During MIS 5e, trees replaced shrubs, as shown in the high arboreal pollen frequencies 30 , and this trend is mirrored in the concurrent smooth decreasing of ACL (Figures 3c and e).…”