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Formation and paleoenvironmental reconstruction of methanogenic histosols from the Campina do Encantado Peatland (Pariquera Açu, SP)

Abstract

Peatlands are wet ecosystems formed by Histosols that account for only 3% of the earth's surface, but store a third of the C stock of all soils. Globally, Histosols are important C sinks formed throughout the Holocene and Late Pleistocene. Water stagnation, nutrient availability, pH and Eh, and the floristic composition of the vegetation that is the parent material of the peat, are factors that control the composition and dynamics of methanogenic microorganisms. However, such mechanism remains not fully understood, especially in tropical environments, where there are few reports of methanogenic peatlands. The main objective of this project is to characterize and describe the processes related to the production and release of carbon dioxide (CO2) and methane (CH4) in tropical Histosols, using a peculiar bog that produces CH4 in anomalous quantities located in Campina do Encantado State Park, in Pariquera-Açu (SP). Pyrolysis gas-chromatography/mass-spectrometry (pyrolysis-GC/MS) will be used to characterize the organic matter (OM) composition of Histosol cores with different levels of CH4 production. The molecular composition of peat OM provides a fingerprint of the composition and (past) processes of peat decomposition that will be used to evaluate its cause-effect relationships with methanogenesis. Together with the measurement and determination of the isotopic composition of CO2 and CH4, as well as through the detection and quantification of methanogenic and methanotrophic microorganisms, it will be possible to identify the main mechanisms responsible for the emission of these gases. Peatlands are excellent environmental archives, and the history of this peatland will be reconstructed by cross-linking molecular information from OM with palynological and isotopic C data. The results will increase our understanding of the formation and degradation of tropical peatlands in near-sea-level environments, and its role in present and future climate change. (AU)