Soil organic carbon turnover is controlled by soil pore space O₂ concentration in brown forest soil

The stability of soil organic matter (SOM) is influenced by its chemical structure as well as by biological and environmental factors. However, the specific mechanisms by which pore space gaseous O₂/CO₂ concentrations affect SOM are not well understood.

The experimental design involved a 2 (Chinese photinia planted and bare land) × 2 (O₂ aeration levels) × 2 (CO₂ aeration levels) design compared to 2 non-aeration treatments, to investigate the impact of pore space O₂/CO₂ concentration on soil enzymes, soil organic carbon (SOC), light fraction organic carbon (LFOC), dissolved organic carbon (DOC) and microbial carbon (MBC).

The injection of 21% O₂ led to a significant increase in the activities of catalase, urease, saccharase, invertase, and polyphenol oxidase enzymes. Significant increases in the contents of SOC, LFOC, DOC, and MBC were observed when comparing the effects of injecting 21% O₂ into the soil with 15% O₂, with the differences between treatments on carbon turnover rate increasing over time. Additionally, vegetation treatments were observed to increase DOC, MBC, and SOC. Changes in pore space gaseous CO₂ concentration from 0.03% to 0.4% had no significant effect on soil microorganisms, soil enzymes, or SOC turnover.

This study demonstrates that higher concentrations of pore space gaseous O₂ stimulate the activity of soil microorganisms, affecting the carbon turnover rate and its stability. These findings provide important evidence of SOC responses to variations in pore space gaseous O₂.