Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
2024421 | Soil Biology and Biochemistry | 2015 | 6 Pages |
â¢The qCO2 (respiration rate per unit microbial biomass) increased with soil C:N ratio in spruce soils.â¢The qCO2 increased with soil C:P ratio in beech, spruce, and mixed forest soils.â¢Microorganisms adjust the substrate to their nutritional demands in terms of C:N:P stoichiometry.
The ratio of carbon-to-nutrient in forest floors is usually much higher than the ratio of carbon-to-nutrient that soil microorganisms require for their nutrition. In order to understand how this mismatch affects carbon (C) cycling, we investigated the respiration rate per unit soil microbial biomass - the metabolic quotient (qCO2) - in relation to the soil carbon-to-nitrogen (C:N) and carbon-to-phosphorus (C:P) ratio in temperate forests. For this purpose, cores of beech, spruce, and mixed spruce-beech forest soils were cut into slices of 1Â cm from the litter layer down to 5Â cm in the mineral soil, and the relationship between the qCO2 and the soil C:N and the soil C:P ratio was analyzed. We found that the qCO2 was positively correlated with soil C:N ratio in spruce soils (RÂ =Â 0.72), and with the soil C:P ratio in beech (RÂ =Â 0.93), spruce (RÂ =Â 0.80) and mixed forest soils (RÂ =Â 0.96). We also observed a close correlation between the qCO2 and the soil C concentration in all three forest types. Yet, the qCO2 decreased less with depth than the C concentration in all three forest types, suggesting that the change in qCO2 is not only controlled by the soil C concentration. We conclude that microorganisms increase their respiration rate per unit biomass with increasing soil C:P ratio and C concentration, which adjusts the substrate to their nutritional demands in terms of stoichiometry.