Properties of peat and other organic soils from temperate European climates: Part I – Physical and chemical characteristics

• A large and consistent dataset on peat and other organic soils was characterised. • Field-assessed and laboratory-measured properties revealed clear dependencies. • Fen peat exhibited lower soil organic carbon contents than bog peat. • Bulk densities of organic soils varied by a factor of ∼54. The chemical and physical properties of peat and other organic soils are key factors controlling hydrological and biogeochemical processes. These properties are highly variable and depend on the botanical composition of the peat-forming species, the degree of decomposition, and secondary pedogenetic processes. Despite their importance, existing studies often lack comprehensive, horizon-specific information, particularly for drained peatlands. This study characterizes key soil properties – bulk density, porosity, soil organic carbon (SOC) content, nitrogen (N) content, C:N ratio, SOC density, and N density – across different substrates (fen, bog, organo-mineral, and gyttja) and horizons described and measured with consistent methods. The dataset comprises samples from 160 peatland sites, including drained, rewetted, and near-natural conditions, providing an open-access resource for modelling and mapping efforts. Analyses revealed strong relationships between field-assessed and laboratory-measured properties. Bulk densities ranged from 0.021 to 1.132 g cm −3 , increasing with the degree of decomposition. On average, bog peats showed the highest SOC contents. The highest SOC densities were found in amorphous peat (0.234 g cm −3 ), while organo-mineral substrates showed values similar to fen peat, highlighting the importance of considering SOC densities of the whole profile instead of contents when estimating the potential of carbon release from organic soils. The results highlight, that organic soils are highly diverse, with bulk densities varying by a factor of approximately 54, or by a factor of 45 when organo-mineral and gyttja substrates are excluded.