Nutrient Balances of Rewetted Fens – Groundwater Lysimeter Results

With the raising of groundwater levels to protect fens and the climate, there may be a risk of nutrients, such as nitrogen or potassium, leaching into the groundwater. Great amounts of nutrients, which are accumulated largely by peat forming plants like Phragmites australis and Carex spec., are conveyed into rewetted fens through high amounts of introduced water. Nitrogen leaching into the groundwater is very low even at the beginning of flooding and there is no sudden, pronounced leaching. Only a portion of potassium is taken up by plants whereas the rest might be found in the groundwater. Increasing nutrient inputs must be expected as soon as more contaminated water is added contributing to the regeneration of groundwater and increasing the pollution with nutrients at once

Evapotranspiration of Rewetted and Drained Fen Soils With Grass – Long Term Lysimeter Studies

In the context of reducing greenhouse gas (GHG) emissions to combat climate change, rewetting of peatlands is of particular importance. High groundwater levels covering organic matter in the soil prevent its oxidation to CO2. The amount of water needed to allow the rewetting of peatlands can be determined in lysimeter studies. The evapotranspiration in fens depends essentially on the groundwater table, the vegetation (transpirational active biomass) and the saturation deficit of the atmosphere. After rewetting, these factors can lead to an evapotranspiration of 1000 l m-2 a-1 and even 2000 l m-2 a-1 in dry years depending on the vegetation. In a long term experiment over 20 years, the lysimeters planted with Phragmites australis showed the highest evapotranspiration rates, followed by those covered with Carex species. Evaluation of these results for a large, flooded, rewetted fen area in the Havelländisches Luch in the federal state of Brandenburg, Germany, with Phragmites confirmed the high values of evapotranspiration measured at the groundwater lysimeter station of ZALF in Paulinenau