Heterotrophic respiration and microbial functional diversity in a conventional cropland in Hungary

Soil respiration is one of the main carbon fluxes and is controlled by the activity of the heterotrophic microorganisms, in addition to environmental factors, and has a significant influence on soil carbon cycling. This study aimed to examine the temporal patterns of soil respiration under field conditions, especially regarding heterotrophic respiration (R_h), its contribution to soil CO₂ efflux, and its relationship to the microbial functional diversity in a conventionally managed cropland in Hungary. Field measurements were performed in soil-installed tubes (40 cm depth, 16 cm diameter, root exclusion) for measuring R_h  and total soil respiration (R_s) was also measured under natural field conditions during the vegetation period. Soil CO₂ fluxes were measured in the field by an automatic soil respiration system under various environmental conditions. Soil temperature and soil moisture were measured in close conjunction, and data processing was carried out along with statistical analyses using R. During the study period in 2025, we took soil samples and microbial functional activity was measured using the Biolog EcoPlates™ technique in order to gain further insights into carbon substrate utilization by the microorganisms.

Average R_s was 2.77 µmol CO₂ m⁻² s⁻¹, while average R_h amounted to 1.22 µmol CO₂ m⁻² s⁻¹. The contribution of heterotrophic respiration to total soil respiration (R_h/R_s) ranged from 0.16 to 1 depending on the phenological phase.