Soil-forming processes and properties of soils developed from fluvic materials in the headwater river valleys of Middle Pomerania, north Poland: A case study of the Kamienna stream

Abstract

This study was aimed at characterizing the soil-forming processes and certain properties of soils that have developed from alluvial sediments in the valley of the Kamienna stream, which represents a headwater stream valley deeply incised into the glacial and fluvioglacial deposits of Middle Pomerania, north Poland. Seven soil profiles distributed, along the stream, were described, sampled, and analyzed using standard procedures. The parent materials of the soils showed stratification and were characterized by a sandy texture with considerable admixtures of gravel in some horizons. A textural measures indicated their accumulation in a highly dynamic fluvial environment. The soils showed broad spatial heterogeneity, highlighting the importance of local-scale factors in their formation. The accumulation of soil organic matter (SOM) and gleying from groundwater were identified as major soil-forming processes, which was reflected in soil reference groups distinguished - Eutric Gleyic Fluvisols, Fluvic Gleyic Mollic Umbrisols, Fluvic Gleyic Phaeozems, and Fluvic Phaeozems. The soils were characterized by deep A horizons and high SOM contents. The stratification of these horizons can indicate the partially allochthonous origin of this component, with the headwater bogs in the upper and middle courses of the stream potentially its source. Additionally, the soils were rich in nitrogen, but poor in total P, K, Ca, Mg, Fe, and Al. The generally low contribution of free Fe oxides to the soils indicated poorly advanced weathering, whereas the predominance of amorphous forms of Fe over crystalline could be the effect of high moisture and the SOM content. The soils were also characterized by a low cation exchange capacity, that varied depending on the SOM and clay contents. The soils were generally acidic, with pH values fluctuating around 5.0-7.0, in most cases, although the predominance of acidic over basic ions was not apparent in the sorption complex.