Soil CO2 Emission, Microbial Biomass, and Basal Respiration of Chernozems under Different Land Uses

The relationships between the soil CO2 emission and microbial properties have been studied in Haplic Chernozem of steppe, forest (oak), bare fallow of the reserve area and in Urbic Technosols of Kursk city. The CO2 emission was monthly measured (May–October) from the soil surface (EMsurf) and two subsoil layers at the depths of 10 and 20 cm (EM10, EM20), and the soil temperature and water content were simultaneously recorded. Overall, 360 soil samples have been taken from the layers 0–10, 10–20, and 20–30 cm for determining the microbial properties (microbial biomass carbon, Cmic; basal respiration, BR). Soil chemical properties (the organic C content, total C, N, P, K, and Ca; and pH) have been measured in the samples taken in July. The EMsurf of steppe averaged 24 g СО2/(m2 day), which was 1.6, 1.5 and 6 times higher than that of forest, urban, and fallow soils, respectively. In the forest, EM10 and EM20 were two times higher than reference EMsurf; they were similar in the fallow and urban soils; and they were by 34% lower in the steppe soil. The soil CO2 emission of studied ecosystems depended weakly on soil temperature and water content during the growing season. The Cmic and BR (0–10 cm) of undisturbed ecosystems (steppe, forest) were higher by, on average, 3–5 and 2–4 times, respectively, than those of disturbed (fallow, urban) ecosystems. The positive correlations between EMsurf and Cmic, BR (0–10 cm) were found (r = 0.56 and 0.74, respectively). The seasonal average EMsurf for different land uses was controlled mainly (78%) by soil BR (linear regression). Therefore, the EMsurf from Chernozems of different land uses during the growing season might be predicted on the basis of BR measurements (0–10 cm).