Fluoreszenzmikroskopisch bestimmte mikrobielle Biomasse und deren Beziehung zum Gesamtkohlenstoffgehalt und zur Dehydrogenaseaktivität in ausgewählten Bodenproben

Microbial biomass measured by fluorescence microscopy and its relation to total organic carbon and dehydrogenase activity in selected soil samples Techniques for direct observation of microbial biomass with epifluorescence microscopy, which have proved reliable in aquatic microbiology, were applied for investigation of soils. The procedure for measurement of microbial biomass consisted of ultrasound treatment, filtration with nuclepore-filters, registration of cell-size classes and separate counting of small bacteria. Microbial biomass of an arable A_p (Slu = silty loamy sand) was nearly twice as high with ultrasonication as with untreated samples. In 16 root-free samples removed from different mineral soils, bacterial biomass ranged from 0,22 to 7,50 mg C/g soil, surpassing fungal biomass in general by the factor 2 to 35. Up to 98% of the total organic carbon (C_org) in soil was present in microbial biomass. In uncultivated topsoils dehydrogenase activity was highly correlated with C_org and microbial biomass (n = 7, r_mult. = 0,972, α = 0,001).