Characterisation and Stability of the Organic Matter of the Plaggic Anthrosols from Central Europe, Northwest and North Russia.
Olga Kalinina1, Oleg Chertov1, Marina Nadporozhskaya1, and Luise Giani2. (1) St.Petersburg State Univ, Oranienbaum Road 2, St.Petersburg, Russia, (2) Carl von Ossietzky Univ, Carl von Ossietzky Strasse, Oldenburg, 26111, Germany
The study focuses on the characterisation and stability of organic matter of Plaggic Anthrosols. Three Plaggic Anthrosols from Northwest Europe (Oldenburg), Northwest Russia (St. Petersburg) and North Russia (Arkhangelsk) have been investigated comparatively. The Plaggic Anthrosols of this study are humus-rich with 17.1-26.8 g kg-1 total organic carbon (TOC) or 3.4-5.3% soil organic matter (SOM) in the plaggic epipedons. The mean C/N ratio of the Oldenburg Plaggic Anthrosol was 21, that of St. Petersburg 17 and of Archangelsk 13, indicating a long-term use of heather sods in Oldenburg and the use of N-rich bog peat in Russia, respectively. Different SOM qualities are also shown by the C/N ratios in the grain size fractions and IR spectra, showing the occurrence of keto- and carboxyl groups only for the Oldenburg soil and amides for the Russian ones, exclusively. The HCl-resistant OC, representing the non-active OC fraction, was relatively high, amounting to 49.3-75.1% of TOC (61.5% in mean) in the plaggic epipedons. Because of large amounts of pyrogenic C significantly larger amounts of the non-active OC fraction were found in the St. Petersburg soil. The H2O2-resistant OC, representing the charcoal, was 3.5-21.0% of TOC. The HF-soluble OC, representing the mineral-bound C fraction, was 7.0-50.5% of TOC, lowest amounts, even below detection limit, was found in the St. Petersburg soil. The investigation of OC in the grain size fractions resulted in highest OC concentrations in the fine silt and clay size separates; Decreased OC concentrations in the sequence Oldenburg, Arkhangelsk, St. Petersburg are related to decreased duration of the plaggen fertilisation management in the same sequence. The OC contents of the heavy fraction (>2 g cm-3) was frequently about 40% of TOC, consisting of large amounts of polysaccharides. Neither the IR spectra nor the investigated OC fractions show a changing pattern with increasing depths of the plaggic epipedons. Although the Plaggic Anthrosols show differences in some OC fractions and OM qualities, they have high proportions of very stable constituents, presumably caused by the long-term plaggen fertilisation management.