Soil microbial biomass and gas-production activity (CO2) in Chernozems of different land use

The typical chernozems (Kursk region, Russia) in undisturbed (virgin and mowing steppe) and disturbed (pasture, black fallow, arable and including urban) ecosystems were studied. In each ecosystem and urban functional zone (recreational, residential and industrial) soil samples were collected in 3-5 randomly chosen locations from the depths 0-10, 10-50, 50-100 and 100-150 cm (total 124). In the collected samples soil microbial biomass (Cmic) was analyzed by substrate-induced respiration method and basal (microbial) respiration (BR) was measured. The ratio of BR / Cmic = qCO2 and portion of Cmic in soil organic carbon (Corg) were estimated. In the soils (0-10 cm) under black fallow, arable and urban ecosystems the Cmic content and Cmic / Corg ratio were almost two times less compared to undisturbed ecosystems. Reduction of Cmic, BR and Cmic / Corg and increase of qCO2 value down the chernozem's profile was reported. The Cmic stocks over the chernozem's profile were 2-4 times higher in undisturbed ecosystems than in disturbed ones. Topsoil 10 cm contributed to the major part of the total Cmic and BR over the profile (41-79%). The excess of CO2 production (BR) in urban soils was shown.