Determinants of spatial variability of methane emissions from wet grasslands on peat soil

Methane (CH4) emissions from soils, representing the consequence of CH4 pro duction, CH4 consumption and CH4 transport, are poorly characterised and sh ow a large spatial variability. This study aimed to assess the determinants of field-scale spatial variability of CH4 emissions from wet grasslands on peat soil. Mean CH4 emission rates of a three-year experiment at 18 plots distributed over three sites in the nature preserve "Nieuwkoopse Plassen" o n pear soil in the Netherlands were related to CH4 production and CH4 consu mption capacities of soil layers, and to soil and vegetation characteristic s. Spatial variability of CH4 emissions and possible determining factors wa s high. Annual CH4 emissions ranged from 3 to 37 g CH4 m(-2) yr(-1). Coeffi cients of variation (CV) of CH4 emissions were on average 37% among sites a nd 83% within sites. Most important determinants of spatial variability wer e CH4 production capacity (average: 211 ng CH4 g(-1) dry soil h(-1); CV: 13 1%) and aboveground biomass of sedges (Carex: spp.) (average: 0.45 g dm(-2) ; CV: 127%) (P < 0.01). Sedges may affect CH4 emissions by stimulating CH4 transport from anaerobic layers to the surface via their vascular system an d/or by serving as substrate for methanogen. For extrapolation of CH4 emiss ions to larger areas, best results will be obtained by using factors that a re easy to determine, like vegetation.