Floodplain soils at the Elbe river, Germany, and their diverse microbial biomass

Abstract

Two long-term submerged Eutric Gleysols (GLe) and two short-time flooded Eutric Fluvisols (FLe) at the Elbe River (Germany) with high organic carbon contents (C_org between 4.9 and 11.6%) were selected to evaluate dehydrogenase activity (DHA), soil microbial carbon (C_mic), C_mic/C_org ratio, and phospholipid fatty acids (PLFA) to characterize and discriminate these soils with microbial parameters. DHA, C_mic and PLFA-biomass as well as C_mic/C_org ratios are considerable lower in GLe's than in FLe's what seem to be an unspecific response of aerobic soil microorganisms on the long flooding period and the resulting short time for development after last flooding. C_mic/C_org ratios are low in comparison to terrestrial soils. PLFA profiles were dominated by saturated fatty acids (FA). Principal component analyses (PCA) with the identified FAs revealed a clear discrimination among the four floodplain soils. In GLe's, all groups of PLFA, inclusive monounsaturated FA, are lowest and in FLe's highest. Polyunsaturated FA fungi biomarker (18:2ω6,9c) was very low in GLe1 and could not be detected in GLe2. The environmental conditions which microorganisms are exposed seem to be disadvantageous for fungi in these long submerged soils.

Keywords:

• phospholipid fatty acids (PLFA)
• dehydrogenase activity (DHA)
• soil microbial carbon (C_mic)
• C_mic/C_org ratio
• wetland soils

Acknowledgements

The authors acknowledge Mrs A. Gurenowitz for laboratory assistance, Dr R. Böhnke for providing the dataset of water levels at the sites and the anonymous reviewers.