Late Holocene in central Brazil: vegetation changes and humidity variability in a tropical wetland

Abstract

The Pandeiros wetland is a high biodiversity ecosystem located within a semiarid region of the Cerrado biome, a neotropical savanna. This large wetland is of key importance for ecological and hydrological balance in central Brazil and for the conservation of the Cerrado fauna and flora. In this study, we present the first palaeoecological investigation of the Pandeiros wetland based on pollen analysis of a palm swamp sediment core encompassing the Late Holocene. Our results show that the wetland was subject to multicentennial‐scale oscillations in water availability during the Late Holocene; in particular, higher local humidity was documented between 4100 and 3100 cal a bp and from 2600 to 1000 cal a bp, and two events of drier local conditions occurred at approximately 2900 and 900 cal a bp. Our results also indicate a general decreasing trend in arboreal density in the Pandeiros River Basin from the beginning of the Late Holocene to the present, with the greatest expansion of dry forest occurring between 3600 and 3100 cal a bp.

Long‐and short‐term vegetation change and inferred climate dynamics and anthropogenic activity in the central Cerrado during the Holocene

“…After 3500 cal a bp , the expansion of a drier open cerrado is characterized by a regression of the tree pollen taxa and the palm swamp Mauritia flexuosa (<7%), and the expansion of grassland pollen (Poaceae 20%) (Cassino et al , 2018). The Pandeiros wetland record (at 460 m asl) (Sabino et al , 2021) shows the presence of a woody cerrado [mainly Astronium ( ~ 5%)] until 2890 cal a bp , when it was replaced by a more open cerrado landscape (Poaceae 18%), with the presence of Asteraceae (5–35%), Euphorbia (5–40%) and Gomphrena (2–25%), during the last part of the Holocene (Sabino et al , 2021).…”

“…In the northern and central Cerrado, floristic changes from cooler to warmer assemblages characterize the transition from the last glacial to the Holocene (Cassino et al, 2018(Cassino et al, , 2020Horák-Terra et al, 2020;Ledru et al, 2006). More contrasted responses have been observed during the early Holocene, with centennial-scale fluctuations in wet and dry conditions in the central region until 6000 cal a BP (Cassino et al, 2018(Cassino et al, , 2020, the full expansion of the Cerrado in northern Brazil from 11 000 cal a BP (Ledru et al, 2006), and the persistence of wet and cold conditions in the north-eastern region of the central Cerrado (Horák-Terra et al, 2020;Sabino et al, 2021). During the mid-Holocene the vegetation became drier (Salgado-Labouriau et al, 1998;Barberi et al, 2000;Cassino et al, 2020), responding to a weaker SASM influence over eastern Brazil (Prado et al, 2013a andPrado et al, 2013b).…”

“…During the mid‐Holocene the vegetation became drier (Salgado‐Labouriau et al , 1998; Barberi et al , 2000; Cassino et al , 2020), responding to a weaker SASM influence over eastern Brazil (Prado et al , 2013a and Prado et al , 2013b). During the late Holocene, multi‐centennial fluctuations between wet and dry conditions in northern Minas Gerais indicate the expansion of a drier Cerrado after 4000 cal a bp (Cassino et al , 2018), and two drier episodes at 2900 and 900 cal a bp (Sabino et al , 2021). However, the low resolution of the analyses (e.g.…”