Composition of carbon fractions and potential denitrification in drained peat soils

SUMMARY The organic matter of five low‐moor peat soils and one eutrophic raised‐bog peat soil was chemically characterized by C fractionation and ion‐exchange chromatography of amino acids and carbohydrates. C fractions were related to potential denitrification, D pot , as a measure of microbial activity and C availability, determined by the acetylene inhibition technique. Chemical and physical properties vary distinctively between different kinds of peat, and show increasing C/N ratio and decreasing bulk density and ash content within the profile. Generally, the carbon composition reflects the geobotanical origin of the peat. In most samples more than 65% of organic C consists of non‐hydrolysable C. Readily hydrolysable neutral sugar C represents up to about 12% of organic C, usually decreasing with depth. The recalcitrant fraction of neutral sugar C is much smaller (1 to 4.2% of organic C) and does not vary with depth. The content of readily hydrolysable glucose exhibits a strong profile differentiation that decreases with depth, whereas the higher contents of recalcitrant glucose carbon (12/0.5 M H 2 SO 4 ) in the lower peat horizons reflect their cellulose character. Regression analysis between D pot and single C components explains up to 51.5% of the variability. Combining fractions which point to C availability (readily hydrolysable glucose) and microbial metabolism (amino acids), it is possible to estimate D pot with a certainty of more than 80%.