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Martin Novak, Czech Geological Survey (Czech Republic)
Eva Prechova, Czech Geological Survey (Czech Republic)
Ivana Jackova, Czech Geological Survey (Czech Republic)
Frantisek Buzek, Czech Geological Survey (Czech Republic)
Petra Pacherova, Czech Geological Survey (Czech Republic)
Marie Adamova, Czech Geological Survey (Czech Republic)
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Peatlands accumulate one third of the world's soil carbon. During climatic warming, higher emanations of greenhouse gases, accompanying thinning of peat deposits, may lead to further temperature increases. We explored the relationship between C cycling in peatlands and climate by a combination of downcore reconstructions and laboratory manipulations of peat cores collected in the Czech Republic (Central Europe) and northern Sweden (Northern Europe). The formation of CO2 and CH4 during peat decomposition depends not only on temperature, but also on organic matter quality. Preliminary data indicated that bulk C can become both isotopically lighter and heavier downcore, but it is not known which C species are responsible for these isotope shifts. Therefore we examined vertical changes in peat organic matter speciation. We sequentially extracted and quantified the following organic C forms in peat: soluble fats, oils and waxes; soluble carbohydrates; soluble phenolics; total hot-water solubles; holocellulose; α-cellulose; hemicellulose; lignin; and acid-soluble carbohydrates. Seven most abundant C forms were analysed also isotopically. Sofar, δ13C data were obtained for two sites with a positive downcore δ13C shift in bulk peat. At Velke Darko (Czech Republic), three types of vertical δ13C trends were observed when C forms were analyzed separately: throughout the profile, δ13C of lipids was the lowest in the system, fluctuating around ?30 per mil. At a depth of 30 cm, δ13C of lipids was 8 per mil lower than that of cellulose. δ13C of all forms of cellulose, carbohydrates and phenolics overlapped, increasing smothly downcore from ?27 to ?22 per mil. δ13C of lignin, also increasing downcore, was off-set relative to cellulose by 2 per mil to more negative values, but never became as low as δ13C of lipids. At Stor Amyran, a site located near the Polar Circle, δ13C of both lipids and lignin were more negative compared to Velke Darko. At the same time, δ13C of cellulose at Stor Amyran was higher than δ13C of cellulose at Velke Darko. The northern site showed less steep increase in δ13C of bulk peat with increasing depth. We propose that this pattern is a result of slower peat decomposition at the northern site.
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