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

Resumo

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 (EM_surf) 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, C_mic; 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 EM_surf 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 EM_surf; 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 C_mic 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 EM_surf and C_mic, BR (0–10 cm) were found (r = 0.56 and 0.74, respectively). The seasonal average EM_surf for different land uses was controlled mainly (78%) by soil BR (linear regression). Therefore, the EM_surf from Chernozems of different land uses during the growing season might be predicted on the basis of BR measurements (0–10 cm).