Microbial respiration per unit microbial biomass depends on litter layer carbon-to-nitrogen ratio

Abstract

Abstract. 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 data set on microbial respiration per unit microbial biomass C -termed the metabolic quotient (qCO 2 ) -was compiled from literature data. It was found that qCO 2 in the soil litter layers was positively correlated with the litter C : N ratio and was negatively correlated with the litter nitrogen (N) concentration. The positive relation between qCO 2 and the 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. The reasons for the observed relationship between qCO 2 and the litter layer C : N ratio could be microbial N mining, overflow respiration or the inhibition of oxidative enzymes at high N concentrations. In conclusion, the results show that qCO 2 increases with the litter layer C : N ratio. Thus, the findings indicate that atmospheric N deposition, leading to decreased litter C : N ratios, might decrease microbial respiration in soils.

Effects of agricultural practices on soil and microbial biomass carbon, nitrogen and phosphorus content: a preliminary case study

“…The C : N ratio of OF1 soil was low, which may be due to the amendment with alfalfa green manure. The low C : N ratio of green alfalfa (13 : 1; USDA, 2011) probably resulted in the microbial consumption of carbon leaving a temporary N surplus in the soil (USDA, 2011;Spohn, 2015). OF3 and CF soils also showed low C : N ratios, probably related to the non-amendment with organic matter in both fields.…”

Influence of Poultry Litter and Poultry Litter Biochar on Soil Microbial Respiration and Nitrifying Bacteria Activity

“…3). According to Spohn [47], reduced respiration activity of soil microorganisms may result from not only lower amount of biomass, but also reduced value of C:N ratio in soil. …”

“…Soil microorganisms play a key role in many processes which are essential for the environment as well as ecological functions of soil [47]. The appropriate condition of groups of soil microorganisms and, therefore, their adequate quantity, activity and diversity, are a prerequisite for the proper functioning of terrestrial ecosystems [3,47].…”

“…It is especially crucial if a solid product of thermal conversion of biomass, i.e. biochar, is applied to soil [2,34,47].…”

“…They are sensitive indicators to monitor biochemical processes in soil [47,50]. Most studies published so far recognised the importance of soil microorganisms in the conversion and storage of carbon, as well as in the maximisation of the potential benefits of biochar applied to the soil to stimulate its biological activity and increase the retention of nutrients introduced with fertilisers [4,24].…”