Molic and Umbric Horizons of Alluvial Sandy Soils of River Valleys in SW Poland

Abstract

The sandy soils of river valleys in Poland and other European countries were subjected to the transformation since the seventeenth century following hydrotechnical engineering works. Regulation of river channels and expansion of drainage infrastructure were intended to protect residential areas from flooding, increase agricultural land, and improve inland navigation. It reduced natural alluvial sedimentation and led to the degradation or disappearance of natural muds, swamps, and bogs habitats. It led to disappearance of shelterbelts and herbaceous vegetation and a decline in landscape diversity and biodiversity. Floodplains are anthropogenically altered and endangered ecosystems in Europe. The lowering of the groundwater table causes the increase of the soil biological activity and intensification of the soil-forming processes, and it leads to the gradual disappearance of the original stratification of sediments (fluvial materials) and the development of horizons. Mollic or umbric horizons are regularly found in river valleys. The purpose of this study was to verify anthropogenic influence on the formation of deep organic matter-rich horizons in sandy soils. It was found that the original organic swamp-alluvial or marsh-alluvial soils, with histic horizons, periodically flooded or located in former oxbow lakes, gradually changed into mineral soils with thick, black, and structured mollic or umbric horizons with an abrupt boundary to subsoil horizons with anthric properties. Although drainage caused a decrease in organic matter content, SOC concentrations remain high despite the sandy texture. These soils are suitable for hay or pasture meadows, for arable land, or as forested areas.