Stages of soil development in the coastal zone of a disappearing lake—a case study from central Poland
Abstract Purpose The aim of this study was to estimate the impact of lake disappearance, groundwater table fluctuations, and some aspects of human pressure on stages of soil cover development in the catchment of Lake Rakutowskie. Materials and methods Research was conducted in soil chronosequence composed of eight soil profiles located in 785-m-long transect. Soils were sampled every 10 cm. Physical and chemical properties were determined with the use of disturbed and undisturbed samples. Radiocarbon dates were obtained for the bottom part of peat in each soil profile. The mineral composition of selected soil samples was determined using the X-ray diffraction (XRD) method. Additionally, the hydrological conditions were continuously monitored from July 27, 2013 to September 23, 2014. Results and discussion An increased rate of shallow lakes overgrowth and final disappearance is a commonly observed process in the European lowlands. This paper presents and discusses the influence of changes in the range of the Lake Rakutowskie wetlands complex (central Poland) and water level fluctuations on soil cover transformation in the immediate vicinity of the lake. Five major phases of soil cover development (from Subaquatic Histosols (Limnic) to Hypereutric Regosol (Drainic, Humic)) were hypothetically reconstructed based on detailed studies of soil physical and chemical properties, mineral composition, water level fluctuations, and radiocarbon dating. The degree of peat decomposition in the studied profiles increased with the distance from the contemporary lake surface. Along with the progressive dehydration and mineralization of organic soils, their physical and chemical properties deteriorated, which is visible, e.g., in soil structure, and mineral and chemical composition (especially TOC and TN). Obtained radiocarbon ages of selected samples indicate that the oldest peat layers developed about 5856 cal BCE (6970 ± 70 14C BP), while the youngest were deposited about 1074 cal CE (980 ± 40 14C BP)–1573 cal CE (300 ± 35 14C BP). Hydrological studies indicate a progressive process of lake disappearance. Conclusions The process of soil cover transforming of the studied area takes place relatively quick, mainly recently due to the influence of human activity. Based on these results, it can be predicted that the lake will most likely disappear in a relatively short time, and the soil cover will be entirely in the fifth phase (P5) of evolution.
