Microbial carbon turnover in beech forest soils at different stages of acidification

Abstract

Microbial carbon turnover was investigated in six beech forest soils (0–10 cm). The soils were sampled in the Göttinger Wald area (Germany) and had developed under identical environments (climate, topography, vegetation) but from different parent materials. The pH-H 2O of the soils was in the range between 4.8 and 8.3. The content of soil organic C was positively related to factors indicating soil acidification and decreased from 96.6 mg C g −1 dry wt in the soil with the highest amount of exchangeable Ca to 31.3mg C g −1 dry wt in the soil with the lowest amount of exchangeable Ca. The size of the microbial C pool varied between 0.70 and 1.52 mg C g −1 soil, the metabolic quotient qCO 2 varied between 1.4 and 2.4 mg CO 2-C g −1 biomass C h −1. Exchangeable Ca was positively correlated to the biomass of the micronora and to the microbial incorporation of C from freshly fallen litter. In contrast, exchangeable Ca was negatively correlated to the C biomass:C org ratio, to C mineralization rate, to qCO 2 and to the specific death rate ( qD). It was concluded that the small but metabolically-active microflora in the more acid soils has a reduced ability to incorporate C from freshly fallen litter into the subsurface C cycle and may thus partly be responsible for the low content of organic C in these soils.