Soil CO2 emission, microbial biomass, and microbial respiration of woody and grassy areas in Moscow (Russia)

Purpose Urbanization significantly changes the carbon balance of the terrestrial ecosystem, an important component of which is soil CO2 emission. One of the main sources of soil CO2 emission is microbial decomposition of soil organic matter. In this regard, we hypothesized a relationship between soil CO2 emission and soil microbial properties (biomass, respiratory activity) in Moscow megapolis areas. Materials and methods Soil CO2 emission was measured monthly (May-October) from the surface (or soil respiration, R-S) and after the sequential removal of the two top 10-cm soil layers at woody (forest park, public garden) and grassy (grassland, arable) areas. Soil temperature (ST) and soil water content were recorded in 0-10-, 10-20-, and 20-30-cm layers, from which samples were taken to measure microbial biomass carbon (C-mic) and basal (microbial) respiration (BR). Results and discussion R-S ranged from 0.3 to 14.7 mu mol CO2 m(-2)s(-1), with average values of 1.0, 5.4, 7.5, and 8.8 mu mol CO2 m(-2)s(-1) for arable, forest park, public garden, and grassland, respectively. Removing the topsoil layer in woody areas resulted in higher CO2 release to the atmosphere than in grassy ones. Topsoil C-mic was on average 110, 331, 517, and 549 mu g C g(-1) and BR was 0.42, 0.87, 0.47, and 0.92 mu g C-CO2 g(-1)h(-1) for arable, forest park, public garden, and grassland, respectively. Subsoil C-mic and BR were 1.5-3 times and 30-62% lower than in topsoil. R-S in woody areas was more strongly dependent on ST than in grassy areas. Strong positive correlation between R-S and topsoil C-mic and C-org (R-2 = 0.98-0.99) was found. Conclusions The R-S of different Moscow's areas might be predicted on the base of soil C-mic or C-org experimental data.