SPATIAL VARIABILITY OF METHANE, NITROUS-OXIDE, AND CARBON-DIOXIDE EMISSIONS FROM DRAINED GRASSLANDS

Emissions of CH4, N2O, and CO2 from soils are the result of a number o f biological and physical processes, each influenced by several enviro nmental and management factors exhibiting spatial variability. This st udy aimed to assess the spatial variability and spatial dependence of CH4, N2O, and CO2 emissions and their underlying soil processes and pr operties from grasslands on drained peat soil (Terric Histosol). Emiss ions and possible controlling factors were measured at a field locatio n in Sweden. Measurements were done on two adjacent sites on peat soil on two successive days for each site. Spatial variability was analyze d with trend analysis and variograms. Both sites consumed small amount s of atmospheric CH4, i.e., 0.03 and 0.05 mg CH4 m(-2) d(-1), and emit ted N2O and CO2, i.e., 5 to 19 mg N2O m(-2) d(-1) and 4 to 6 g CO2 m(- 2) d(-1). Spatial variability of emissions was high, with coefficients of variation of 50 to 1400%. Emissions either showed a spatial trend or were spatially dependent with ranges of spatial dependence of 50 to >200 m. However, spatial dependence of emissions showed differences b etween sites and short-term temporal variability. Variograms of emissi ons and soil processes, which are partly biological in nature and have a high degree of inherent variability, should be interpreted with car e.