|Spohn, M: Microbial respiration per unit microbial biomass depends on soil litter carbon-to-nitrogen ratio, Biogeosciences, 12, 817-823 (2015), doi:10.5194/bg-12-817-2015|
Soil microbial respiration is a central process in the terrestrial carbon (C) cycle. In this study I tested the effect of the carbon-to-nitrogen (C:N) ratio of soil litter layers on microbial respiration in absolute terms and per unit microbial biomass C. For this purpose, a global dataset on microbial respiration per unit microbial biomass C–termed the metabolic quotient (qCO2) – was compiled form literature data. It was found that the qCO2 in the soil litter layers was positively correlated with the litter C:N ratio and negatively related with the litter nitrogen (N) concentration. The positive relation between qCO2 and litter C:N ratio resulted from an increase in respiration with the C:N ratio in combination with no significant effect of the litter C:N ratio on the soil microbial biomass C concentration. The results suggest that soil microorganisms respire more C both in absolute terms and per unit microbial biomass C when decomposing N-poor substrate. Thus, the findings indicate that atmospheric N deposition, leading to decreased litter C:N ratios, might decrease microbial respiration in soils.