Particulate organic carbon (POC) in relation to other pore water carbon fractions in drained and rewetted fens in Southern Germany

Numerous studies have dealt with carbon (C) contents in Histosols, but there are no studies quantifying the relative importance of the individual C components in pore waters. For this study, measurements were taken of all the carbon components (particulate organic carbon, POC; dissolved organic carbon, DOC; dissolved inorganic carbon, DIC; dissolved methane, CH₄) in the soil pore water of calcareous fens under three different water management regimes (rewetted, deeply and moderately drained). Pore water was collected weekly or biweekly (April 2004 to April 2006) at depths between 10 and 150 cm. The main results obtained were: (1) DIC (94-280 mgC l^-1) was the main C-component. (2) POC and DOC concentrations in the pore water (14-125 mg Cl^-1 vs. 41-95 mgC l^-1) were pari passu. (3) Dissolved CH4 was the smallest C component (0.005-0.9 mg Cl^-1). Interestingly, about 30% of the POM particles were colonized by microbes indicating that they are active in the internal C turnover. Certainly, both POC and DOC fractions are essential components of the C budget of peatlands. Furthermore, dissolved CO₂ in all forms of DIC appears to be an important part of peatland C-balance.