Carbon dioxide emission and soil microbial respiration activity of Chernozems under anthropogenic transformation of terrestrial ecosystems

The total soil CO 2 emission (EM) and portion of microbial respiration were measured ( in situ ; May, June, July 2015) in Chernozems typical of virgin steppe, oak forest, bare fallow and urban ecosystems (Kursk region, Russia). In soil samples (upper 10 cm layer), the soil microbial biomass carbon (C mic ), basal respiration (BR) and fungi-to-bacteria ratio were determined and the specific microbial respiration (BR / C mic = q CO 2 ) was calculated. The EM was varied from 2.0 (fallow) to 23.2 (steppe) g СО 2 m -2 d -1 . The portion of microbial respiration in EM was reached in average 83, 51 and 60% for forest, steppe and urban, respectively. The soil C mic and BR were decreased along a gradient of ecosystems transformation (by 4 and 2 times less, respectively), while the q CO 2 of urban soil was higher (in average by 42%) compared to steppe, forest and fallow. In urban soil the C mic portion in soil С org and С fungi -to-С org ratio were by 2.6 and 2.4 times less than those for steppe. The relationship between microbial respiration and BR values in Chernozems of various ecosystems was significant (R 2 = 0.57).