Test and application of a vegetation-based CO2 and CH4 flux estimate from three ombrogenic and topogenic peatlands in Southern Germany

Abstract: A stabilisation and restoration of peatlands is seen as a sustainable strategie for climate change mitigation. To find the most suitable target areas, greenhouse gas fluxes have to be quantified. A vegetation-based flux estimate is seen as cost-effective alternative to avoid time consuming and expensive flux measurements. The present study aims to define current obstacles and limitations to a vegetation-based flux estimate and define a possible scope for vegetation-based flux estimates in Baden-Württemberg. A case study was performed in three ombrogenic and topogenic mires in Southern Germany using the tools Greenhouse Gas Emission Site Type (GEST) for non-forest sites and IPCC’s ‘Good Practise Guidance for Land Use, Land Use Change and Forestry’(GPG-LULUCF) for forest sites. The study was limited to carbon dioxide (CO2) and methane (CH4) fluxes, shown as CO2 equivalents (CO2e). Based on 115 vegetation relevés, three vegetation classification systems on non-forest sites ‘vegetation forms’, ‘phytosociological plant communities’ and ‘Biotope types of Baden-Württemberg’ were compared to test if they can replace each other in a flux estimate. Calculation parameters for forest-sites were chosen for the study area. A greenhouse gas balance was established for the study area. The reviewed vegetation classification systems showed inconsistent overlaps. Hence, the vegetation classification systems were considered to be not completely compatible. As descripition of vegetation forms was considered to be insufficient for Southern Germany, an application of vegetation-based CO2 and CH4 flux estimates was considered to be difficult in Baden-Württemberg. Mean CO2 and CH4 emissions of 9,7 t CO2e ha-1 yr-1 were estimated in the study area. Emissions from forested peat were smaller than from mire and from grassland on peat. However, the selection of parameters for GPG-LULUCF and associated inaccuracies influenced the estimate. Footpaths and roads, watercourses and lakes, pastures, cropland and clearcut were not considered and N2O emissions were excluded from the estimate. Considering these limitations of the estimate, vegetation-based carbon estimates should be verified and refined before a statewide application.