Humus forms in forests of the northern German lowlands were investigated on the basis of morphological, soil chemical and microbiological characteristics. Existing classifications for humus forms in temperate forest ecosystems were reviewed and compared, and the historical development of the German classification was compiled. Morphological aspects of humus forms in intensively managed forests are presented. A soil moisture index is suggested which has been harmonized between the site mapping systems of the lowlands, and which provides a systematic approach to enter the classification of humus forms. The study then analyzed the chemical data of the German large-scale soil inventory with respect to humus forms, and additionally investigated a representative subset of soil inventory points for microbiological activity. Decomposition types were derived and compared to humus forms and soil chemical data. The leveling effects of pollutant deposition on the soil chemical condition in central European forest ecosystems were confirmed. These effects do not correspond to the range of humus forms and microbiological activity types that were found. It can be concluded that the commonly used chemical indicators for the soil condition (C/N, base saturation and pH) do not sufficiently reflect the nutrient and productivity status of forest soils.