Micromorphological Interpretation of Natural and Anthropogenic Evolution of Soils in Bykovo Lacustrine-Alluvial Section of the Moskva River Floodplain

Soils of Bykovo lacustrine-like floodplain section have a complicated landuse history: alternation of meadows, suburban farming, cropland with partial land leveling and local drainage, now – 10 years-old layland. The effects of these events along with manifestations of fluvial pedogenesis were studied in thin sections. Well-known micromorphological features of alluvial soils have been confirmed, specific properties related to the position of soils in lacustrine-alluvial landscape have been revealed. Fluvial fabric elements are rather mitigated, since flooding of this section was weak and irregular; topsoils are similar in natural and post-arable soils and have no traces of agrogenic degradation. The layland regime contributes to soil regradation: higher pedality and pedofauna activity were recorded. Artificial drainage is recognized in thin sections by changes in iron (hydr)oxide pedofeatures vs. the natural gley soils, namely, iron segregations and nodules in the former soils (Fluvic Mollic Gleysols), and iron coatings, zones of complete bleaching alternating with strong impregnations in the latter. Soil on the terrace outlier was identified as a truncated texturally differentiated soil, which upper part was removed during leveling, then a new layer was placed on BT (argic) horizon: (Terric Anthrosol (Loamic, Gleyic, over buried Retisol)). Filled layers may contain blocky subangular peds of BT horizon, partially assimilated in the soil mass. These peds serve as micromorphological markers for reconstructing soil history owing to their easily recognizable particular properties: blocky subangular microstructure, speckled b-fabric, clay (hypo)coatings.