Author Description

The area of wet grasslands on peat soil in the Netherlands is small, but slowly increasing at the expense of drained, agriculturally used grasslands. Net CH 4 emissions were measured at wet grasslands on peat soil in the nature preserve "Nieuwkoopse Plassen", which is a former peat mining and agricultural area with narrow grassland and reed fields surrounded by ditches. Ground water level is kept near the surface via the water level of the ditches. Mean ground water level is 10-20 cm below the surface. N input is 30-50 kg N ha sup-1/SUPyr sup-1/SUPvia atmospheric deposition. Measurements were carried out at three sites, Drie Berken Zudde, Koole and Brampjesgat, during three years. The sites were considerable sources of CH 4 with average CH 4 emissions of 79, 133 and 204 kg CH 4 ha sup-1/SUPyr sup-1/SUP, respectively. Ditches near the sites emitted 42-225 kg CH 4 ha sup-1/SUPyr sup-1/SUP. The time course of CH 4 emissions for all experimental sites and years was fit with a multiple linear regression model with ground water level and soil temperature as independent variables. Lowering or raising the ground water level by 5 cm could decrease or increase CH 4 emissions by 30-50%. Therefore, ground water level management of these grasslands should be done with care (Chapter 2). Spatial variability of CH 4 emissions was high. Most important determinants of spatial variability were CH 4 production capacity and aboveground biomass of sedges ( Carex spp.). Sedges and other plants may affect CH 4 emissions by stimulating CH 4 transport from anaerobic layers in the soil to the surface and by serving as substrate for methanogens (Chapter 3).