Concentrations of dissolved organic carbon in peat soils as influenced by land use and site characteristics — A lysimeter study

• DOC concentrations were predominantly driven by peat degradation and pH.
• Soil organic carbon content and water table depth were less important.
• No seasonality of DOC concentrations could be detected.

The release of dissolved organic carbon (DOC) from peatlands implies a loss of sequestered carbon. During the last two decades, an increase of DOC exports in Europe and North America has been reported. The influence of land use on DOC has been contradictorily discussed and a lack of knowledge exists particularly for fens in Northeastern Germany. Therefore, we aimed to investigate DOC release from fen soils with differing land use intensity. To exclude climatic influences and water level fluctuations, a lysimeter study was performed. The lysimeter vessels contained three histosols from Northeastern Germany and varied in peat quantity, substrate quality, water table depth, pH and vegetation, as these factors are strongly influenced by land use intensity. Water for DOC analysis was sampled biweekly over a two year period. DOC release ranged from 4 to 123 mg/L− 1 with a median of 32 ± 22 mg/L− 1. Lowest DOC concentrations were found at deeply drained gleysols and at relatively slightly decomposed, acidic histosols. Highest concentrations were measured in the most degraded histosols. Degree of decomposition and pH were found to be the major driving factors for DOC release. Long-lasting rewetted lysimeters were not observed to release a lower amount of DOC than drained ones, which may be of importance when restoration of degraded peatlands is intended. As lysimeters from the same site released relatively similar amounts of DOC despite their varying management during the last 50 years, it appears that peatlands have an individual potential for DOC release.