Comparison of N2O and CH4 fluxes from Pannonian natural ecosystems

Static chamber measurements of nitrous oxide (N2O) and methane (CH4) fluxes were made from five characteristic vegetation types, representing three different natural ecosystems (grasslands, deciduous forest and wetlands) in the Pannonian basin, Hungary. The main objective of the study was to determine the drivers of average seasonal, annual and interannual N2O and CH4 fluxes in these different ecosystems to enable more accurate predictions of responses to future climatic conditions. Investigations into the response of net N2O and CH4 emission rates to soil temperature and soil water content were carried out over a 2-year period. Both N2O and CH4 fluxes covered a wide range. Yearly average N2O emissions ranged from 4.38 mg N m(-2) year(-1) for wetland poplar forest to 242 mg N m(-2) year(-1) for mountain oak forest. Yearly average soil fluxes of CH4 varied from oxidation, -106 mg CH4 m(-2) year(-1), for loess grassland to an emission of 129 mg CH4 m(-2) year(-1) for a wetland Glyceria stand. Multiple regression analyses showed that N2O fluxes from the Pannonian grasslands and oak forest were more dependent than CH4 fluxes on the key soil variables water content and temperature. The largest seasonal mean N2O emission, 319 mg N m(-2) year(-1), from a mountain oak forest, was observed in summer, and the largest seasonal mean CH4 emission, equivalent to an annual rate of 423 mg CH4 m(-2) year(-1), from a wetland Glycerin stand, was found in the spring of the wet year.