A 1.8 million year history of Amazon vegetation

Author(s):Show less -

Kern, Andrea K. ; Akabane, Thomas Kenji ; Ferreira, Jaqueline Q. ; Chiessi, Cristiano M. ; Willard, Debra A. ; Ferreira, Fabricio ; Sanders, Allan Oliveira ; Silva, Cleverson G. ; Rigsby, Catherine ; Cruz, Francisco W. ; Dwyer, Gary S. ; Fritz, Sherilyn C. ; Baker, Paul A.

• Document type: Journal article
• Source: QUATERNARY SCIENCE REVIEWS; v. 299, p. 18-pg., 2023-01-01.

Abstract

During the Pleistocene, long-term trends in global climate were controlled by orbital cycles leading to high amplitude glacial-interglacial variability. The history of Amazonian vegetation during this period is largely unknown since no continuous record from the lowland basin extends significantly beyond the last glacial stage. Here we present a paleoenvironmental record spanning the last 1800 kyr based on palynological data, biome reconstructions, and biodiversity metrics from a marine sediment core that preserves a continuous archive of sediments from the Amazon River.Tropical rainforests dominated the Amazonian lowlands during the last 1800 ka interchanging with surrounding warm-temperate rainforests and tropical seasonal forests. Between 1800 and 1000 ka, rainforest biomes were present in the Amazon drainage basin, along with extensive riparian wetland vegetation. Tropical rainforest expansion occurred during the relatively warm Marine Isotope Stages 33 and 31 (ca. 1110 to 1060 ka), followed by a contraction of both forests and wetlands until ca. 800 ka. Between 800 and 400 ka, low pollen concentration and low diversity of palynological assemblages renders difficult the interpretation of Amazonian vegetation. A strong synchronicity between vegetation changes and glacial-interglacial global climate cycles was established around 400 ka. After 400 ka, interglacial vegetation was dominated by lowland tropical rainforest in association with warmer tem-peratures and higher CO2. During cooler temperatures and lower CO2 of glacial stages, tropical seasonal forests expanded, presumably towards eastern Amazonia. While this study provides no evidence sup-porting a significant expansion of savanna or steppe vegetation within the Amazonian lowlands during glacial periods, there were changes in the rainforest composition in some parts of the basin towards a higher proportion of deciduous elements, pointing to less humid conditions and/or greater seasonality of precipitation. Nevertheless, rainforest persisted during both glacial and interglacial periods. These findings confirm the sensitivity of tropical lowland vegetation to changes in CO2, temperature, and moisture availability and the most suitable conditions for tropical rainforests occurred during the warmest stages of the Mid Pleistocene Transition and during the interglacial stages of the past 400 kyr.(c) 2022 Elsevier Ltd. All rights reserved. (AU)

• FAPESP's process: 12/50260-6 - Structure and evolution of the Amazonian biota and its environment: an integrative approach
• Grantee: Lúcia Garcez Lohmann
• Support Opportunities: BIOTA-FAPESP Program - Thematic Grants
• FAPESP's process: 19/24349-9 - Assessing the effects of past and future climate change on Amazonian biodiversity (CLAMBIO)
• Grantee: Cristiano Mazur Chiessi
• Support Opportunities: BIOTA-FAPESP Program - Regular Research Grants
• FAPESP's process: 18/15123-4 - Past perspectives on tipping elements of the climate system: the Amazon Rainforest and the Atlantic Meridional Overturning Circulation (PPTEAM)
• Grantee: Cristiano Mazur Chiessi
• Support Opportunities: Research Grants - Research Program on Global Climate Change - Young Investigators - Phase 2
• FAPESP's process: 14/05582-0 - The Amazonian biota structure and evolution and its environment: Amazon Basin paleobotany and palynology
• Grantee: Andrea Kern
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 15/18314-7 - Pollen-based vegetation reconstruction during the last glacial interglacial-cycles from Western Tropical Atlantic marine cores
• Grantee: Andrea Kern
• Support Opportunities: Scholarships abroad - Research Internship - Post-doctor
• FAPESP's process: 19/19948-0 - Influence of Late Pleistocene climate changes on the Amazon vegetation
• Grantee: Thomas Kenji Akabane
• Support Opportunities: Scholarships in Brazil - Doctorate