Methane emissions from wet grasslands on peat soil in a nature preserve

The area of wet grasslands on peat soil in the Netherlands is slowly increa sing at the expense of drained, agriculturally used grasslands. This study aimed (i) to assess the contribution of wet grasslands on peat soil to meth ane (CH4) emissions, and (ii) to explain differences among sites and betwee n years in order to improve our understanding of controlling factors. For t hese purposes, a field study was conducted in the period 1994-1996 in the n ature preserve "Nieuwkoopse Plassen", which is a former peat mining and agr icultural area. Net CH4 emissions were measured weekly to monthly with vent ed closed flux chambers at three representative sites, and at ditches near these sites. Three-years average of CH4 emissions was 7.9 g CH4 m(-2) yr(-1 ) for Drie Berken Zudde, 13.3 for Koole, and 20.4 for Brampjesgat. Ditches near the sites emitted 4.2-22.5 g CH4 m(-2) yr(-1). The time-course of CH4 emissions for all experimental sites and years was fit with a multiple line ar regression model with ground water level and soil temperature as indepen dent variables. Lowering or raising the ground water level by 5 cm could de crease or increase CH4 emissions by 30-50%. Therefore, ground water level m anagement of these grasslands should be done with care.