Environmental changes during the last millennium based on multi-proxy palaeoecological records in a savanna-forest mosaic from the northernmost Brazilian Amazon region

Abstract

The environmental changes and the dynamics of the savanna-forest mosaic, over the last 1050 years, have been reconstructed by pollen, charcoal, radiocarbon dating mineralogical and geochemical analyses of sediment cores taken from three different Mauritia flexuosa palm swamps in the northernmost part of the Brazilian Amazon region (northern state of Roraima). Studies on the relationship between the modern pollen rain and the regional vegetation provide additional information for the interpretation of the fossil pollen records. The fossil pollen assemblages and geochemical results indicate relatively wet climatic conditions throughout the recorded period. Despite these moist conditions, fires were frequent and are one of the reasons for the dominance of a grassy savanna instead of forest expansion in the study area. Considering the generally wet climatic conditions, these fires were most likely caused by human activities. Even today, fires hinder forest expansion into savanna areas. Sandy hydromorphic soils may also act as an edaphic control to maintain the current sharp boundary between forest and savanna ecosystems.

Climatic and anthropogenic drivers of northern Amazon fires during the 2015–2016 El Niño event

“…), human‐ignited fire has markedly influenced the boundaries between forest and savanna areas, killing pioneer forest species invading savanna areas and hence hampering forest expansion (Meneses et al. ). Conversely, an expansion of forests was reported in certain areas of the state after 200 cal yr BP, allegedly because of the decline and displacement of indigenous populations after the arrival of European settlers and consequent reduction in fire occurrence (Meneses et al.…”

“…On the other hand, the analysis of charcoal concentrations of surface sediments in the forest–savanna transition of this region indicated that forest cover acted as an effective buffer during the last millennium, blocking fire entrance into forested ecosystems (Meneses et al. ). As in other parts of Amazonia, forest fires were probably a rare event in Roraima before the 20 th century (Schroeder et al.…”

“…In the state of Roraima, located in the northernmost part of the Brazilian Amazon (Fig. 1), integrated pollen and sedimentological records suggest that, despite the moist conditions in the last 1,050 yr (Meneses et al 2013), human-ignited fire has markedly influenced the boundaries between forest and savanna areas, killing pioneer forest species invading savanna areas and hence hampering forest expansion (Meneses et al 2015). Conversely, an expansion of forests was reported in certain areas of the state after 200 cal yr BP, allegedly because of the decline and displacement of indigenous populations after the arrival of European settlers and consequent reduction in fire occurrence (Meneses et al 2013(Meneses et al , 2015.…”

Late-Holocene gallery forest retrogression in the Venezuelan Guayana: New data and implications for the conservation of a cultural landscape

“…Charcoal pieces from wood found in the studied records suggested that fire contributed with the vegetation changes observed. A more complex picture was recently presented by Meneses et al (2015) in the same region, where three late-Holocene Palaeoecological records exhibited different trends: forest reduction in one place and more stable forest/palm swamp patches in the others. These findings stress the role of human-made fires in shaping savanna/ palm swamps/forest mosaics, but also point out the importance of the extremely poor, acidic soils present in the region, and local edaphic and microclimatic variations, as significant controls on the current vegetation patterns.…”

Protein extraction methods of tomato, environmental changes of the Amazon Forest in Roraima (northernmost part of Brazil) for the last 1000 years, and histological characteristics of a dolphin species

“…In a very interesting study, Maria E.N.S. Meneses and colleagues have analyzed the environmental changes for over 1000 years of the Amazon forest located in the state of Roraima (Meneses et al 2015). Using multiple lines of evidence such as geochemistry and palinological data from three different sediment cores, these authors were able to establish the vegetation dynamic in the last millennium in this region, providing some explanations on how the current sharp boundaries between the forest and savanna ecosystems have been maintained.…”