Microbial Biomass

The acid soil at the Solling site has the lowest microbial biomass, the lowest Cmic-to-Corg ratio and the highest qCO2 value in all mineral soil layers of the three beech forest soils. High soil acidity, low bioturbation and sparse ground vegetation at the Solling site affected these parameters.
Total microbial biomass was about 45% lower at the acid Solling site than at the base-rich Go¨ttinger Wald and Zierenberg sites. About two-thirds of the total microbial biomass was present in the surface organic layer at Solling site whereas more than two-thirds were present in the base-rich mineral soils of the Go¨ttinger Wald and Zierenberg sites.
The luxuriant herb layer increased the substrate availability for micro-organisms (high Cmic-to-Corg ratio) in all mineral soil layers at the Go¨ttinger Wald and Zierenberg sites by increasing earthworm activity. Low Cmic-to-Corg ratios
indicated a low substrate availability in the acid mineral soil layers and the strong decrease from L to the F/H layers suggested a rapid stabilisation of the remaining litter in the F layer.
The fraction of fungal respiration decreased with increasing pH from a basaltdominated soil (87% at pH(KCl) of 4.1) to a lime-dominated soil (55% at pH (KCl) of 6.4) along an acidity gradient at Zierenberg site.