Most fens in Northeast-Germany have been drained since the late 18^th century with a consequent increase in intensity of agricultural land use until the early 1990s. This cultivation resulted in severe peat degradation. Nowadays schemes are introduced to restore such degraded wetland sites. However, little is known about the impact of these restoration schemes on nutrient dynamics in soil and water.

We investigated the effects of changes in land use and a raise of the groundwater table on nitrogen, phosphorus, and carbon in soil, soil solution, and groundwater at six sites with variable land use and management in the “Drömling” fen area. Changes in land use from intensive crop production to extensive pasture reduced nitrogen and phosphorus leaching from soil into groundwater. An alder swamp forest site contained much higher inorganic nitrogen and dissolved organic carbon contents in soil and water than a site under grassland because of enhanced degradation of the peat layer under this forest. Increasing groundwater tables partly decreased mineral nitrogen content of the topsoil. However, peat decomposition due to a lowering of the groundwater table in summer and slow rewetting in autumn caused high N mineralisation peaks followed by temporarily high nitrate contents in groundwater at sites with an existent peat layer. Higher water tables increased phosphorus and carbon contents in the groundwater due to a decreased redox potential, which increased phosphorus solubility and intensified leaching of dissolved organic matter from the peat. The results show that variation in water table levels is an important factor controlling the concentration of N, P and DOC in soil solution and groundwater.