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.