Forest stability during the early and late Holocene in the igapó floodplains of the Rio Negro, northwestern Brazil

Abstract

Located at the northwestern part of the Amazon basin, Rio Negro is the largest black-water river in the world and is one of the poorest studied regions of the Amazon lowlands. In the middle-upper part of the Rio Negro were retrieved sediment cores form Lake Acarabixi, which were analyzed using pollen, spores, charcoal, and geochemistry. The aim of this study was to detect the influences from humans and river dynamics on the vegetation history in the region. Two main periods of vegetation and river dynamics were detected. From 10,840 to 8240 cal yr BP, the river had a direct influence into the lake. The lake had a regional input of charcoal particles, which reflected the effect of the dry Holocene period in the basin. Furthermore, highland taxa such asHedyosmumandMyrsinewere found at that time along with igapó forest species that are characteristic to tolerate extended flooding likeEschweilera,Macrolobium, Myrtaceae,Swartzia, andAstrocaryum. During the late Holocene (1600 to 650 cal yr BP), more lacustrine phases were observed. There were no drastic changes in vegetation but the presence of pioneer species likeVismiaandCecropia, along with the signal of fires, which pointed to human disturbances.

Analysis of Suspended Sediment in the Anavilhanas Archipelago, Rio Negro, Amazon Basin

“…However, the Negro and Branco rivers were not in a stable condition for sedimentary processes in the Late Quaternary [11,62,65]. Considering that the current conditions of the Negro River were established in the last 1000 years [11,65], the sedimentation rate estimated in this study indicates a deposition of approximately 30 cm of pelitic deposits in the Anavilhanas region. These results reinforce the idea that the Anavilhanas, which have little erosion process, still has areas with active deposition and an environment that continues to slowly form.…”

“…Sediment dating from Lake Acarabixi, located on the Negro River floodplain upstream from the Mariuá Archipelago based on radiocarbon dating, indicate that Negro River had more energy and strong seasonality around 10,840 years cal BP [65]. Additionally, that after 8240 years cal BP, a change lowered the energy and reduced the river dynamics.…”

Synergistic impacts of anthropogenic fires and aridity on plant diversity in the Western Ghats: Implications for management of ancient social-ecological systems

“…Alongside other long-term, pollen-based diversity studies in the tropics (e.g., Weng et al, 2006;Figueroa-Rangel et al, 2012;Palazzesi et al, 2014;Rodríguez-Zorro et al, 2018), this record echoes the unique ecological character of the tropics at large: the tree-covered landscape matrix is the most important determinant of sustaining biodiversity in the tropics. From a conservation point of view, our results further underline the need for maintaining trees in human-influenced tropical landscapes.…”

In search of the ice age tropics, a tribute to Prof. Daniel Livingstone and Prof. Paul Colinvaux

“…The fossil pollen data relate changes in forest composition to changes in North Atlantic sea-surface temperature. The record from Lake Acarabixi (Rodriguez-Zorro et al, 2018) lends weight to inferences that Amazonia was already forested at the onset of the Holocene (following Colinvaux et al, 1996), although the composition of the fossil pollen shows marked differences between the early Holocene and modern times. The Serra do Tabuleiro peat bog record, presented by Behling and de Oliveira (2018) is from the Atlantic rain forest and captures the transition from open woodland to Atlantic rain forest at the onset of the Holocene.…”