Organic matter dynamics in tropical peatlands (Diamantina, Brasil) - development of molecular proxies to reconstruct environmental changes

Abstract

In order to predict future climate changes data on past changes are essential. The well preserved stratigraphy of peat deposits can be used to reconstruct past environmental conditions. The molecular composition of organic matter (OM) in peatlands, soils and sediments supplies information on the botanical sources (plant identity) and on the extent of decomposition during litter decay. Therefore, the molecular composition of OM is often used as a proxy for past environmental conditions, or to obtain information on the rate of carbon sequestration that is a crucial element in the global carbon cycle. Both vegetation composition and the degree of decomposition of its remains are determined by depth and fluctuation of the water table. Until present there is a large deficiency in studies which combine vegetation and decomposition characteristics to investigate OM dynamics in peatlands, and most research is concentrated on boreal and temperate peatlands, while tropical peatland ecosystems remain largely unexplored. A combination of OM proxies is essential for a solid palaeohydrological interpretation of a peat deposit, because the distribution of plant species and decomposition of their remains in peat are closely associated. Characterisation of peat by pyrolysis gas chromatography/mass spectrometry (pyrolysis-GC/MS) provides detailed information on its molecular composition. This project aims to use this molecular signature to develop chemical parameters for a palaeohydrological interpretation of tropical peat deposits (Diamantina, Brasil). Furthermore, we will examine the interaction between vegetation composition and decomposition processes, and its effects on the OM composition in tropical peat. Finally, data from the molecular chemistry will be compared with independent climate proxies obtained from the same samples.