Holocene vegetation and fire dynamics in central-eastern Brazil: Molecular records from the Pau de Fruta peatland

Tropical climate dynamics play a major role in the global climate system. Precipitation patterns in the Serra do Espinhaço Meridional (Minas Gerais, Brazil) are influenced by both the South Atlantic Convergence Zone (SACZ) and the Inter Tropical Convergence Zone (ITCZ). This makes the area important for the interpretation of climate dynamics. The composition of the Holocene Pau de Fruta peat deposit was analysed using pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS). Molecular records agreed well with δ13C and δ15N stable isotopes, C content and mineral content, and pollen records. Changes in peatland plant species composition and fire occurrence indicated several wet and dry periods for the Pau de Fruta peatland during the Holocene; from the beginning of the Holocene to 7400 cal yr BP (phase I; dry and cold), from 7400 to 4200 cal yr BP (phase II; wet and warm), from 4200 to 1000 cal yr BP (phase III; dry and warm), from 1000 to 400 cal yrBP (phase IV; wet and warm) and from 400 cal yr BP to the present (V). The hydrological shifts showed a chronology comparable with that described in other palaeoclimatic studies for central-eastern Brazil, indicating that local conditions agree with regional ones. Analytical Py of the peat deposit provided a multi-proxy record via the identification of specific markers for both peatland plants (vegetation) and charred material (fire), whereas the general chemistry provided information on the degree of decomposition of the organic matter. Molecular chemistry of the peat core sampled at high resolution provided insight into peatland C dynamics, which is important for the interpretation of C sequestration in tropical peatlands. Molecular aspects accurately reflected local environmental change. The general agreement of Py data with pollen and inorganic chemistry supports the use of the molecular approach, because it provides local proxy indicators for peatlands, avoiding a mixture of local and regional signals.