Amazonia has been recently included in discussions on the role of tropical peatlands in the global carbon cycle owing to extensive peatlands up to 7.5 m thick, reported from Western Amazonia (Peru). The aim of this study was to explore peat accumulation in Central Amazonia (Brazil). Of seven field sites, six located in the Negro River basin and one close to the junction of the Negro River with the Amazon, four had a peat deposit from 0.10 to 2.10 m thick. Another two sites had other organic soil type which could not be called peat. Only one site did not have any organic deposit. The loss-on-ignition (LOI), carbon content and dry bulk density, measured for the four peatland sites, varied from 17.7 to 97.4 %, 11 to 59 %, and 0.0002 to 0.572 g cm−3, respectively. All sites were classified as minerotrophic based on pH and peat thickness. The study confirms that Amazonian peatlands are not limited to Western Amazonia but also exist in Central Amazonia. We could not find as thick and extensive peats as in Western Amazonia, which we suggest is due to differences in rainfall and hydrology, tectonic conditions, topography, subsoil type and frequency of fires.
KeywordsBrazil Central Amazonia Peat South America Tropical peatland
We thank João Rocha, Isis Perdigão, Brazilian villagers and the staff of the National Institute for Research in the Amazon (Instituto Nacional de Pesquisas da Amazônia, INPA) for help during the field work; Kari Kortekuru, Marko Pesu and Hanna Tuomisto for field equipment; Orlando Cruz Junior, Marjut Wallner and the Department of Geology of the University of Turku for laboratory facilities; and Kalle Ruokolainen and Leif Schulman. In addition, we thank the Kone Foundation, the GEOMA Modelling Network of the Brazilian Ministry of Science and the Societas Biologica Fennica Vanamo for funding. The collected peat samples belong to INPA. A portion of each sample was sent by INPA to the University of Turku, Finland, for the laboratory analyses.
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