Abstract
The aim of the study was to assess the condition of forest soils in central and northern Poland in 2007–2017. The study areas were located in eight forest districts, namely, Białowieża, Chojnów, Łąck, Gdańsk, Krotoszyn, Krucz, Strzałowo and Suwałki. In 2007 and 2017, soil samples were taken from the organic layer (O) and five mineral layers (M): 0–5, 5–10, 10–20, 20–40 and 40–80 cm deep. Physicochemical analyses of the soil were carried out on the appropriately prepared samples (i.e., drying, sieving, grinding), that is, granulometric composition, pHCaCl2 in a solution of 0.01 mol CaCl2·dm-3, organic carbon content (TOC), total nitrogen content (TN), exchangeable acidity (Hw) and the content of basic and acidic cations in a solution of 0.1 M barium chloride at pH 8.1. In addition, the sum of cations (SBC), the cation exchange capacity (CEC), the saturation of the basic complex (BS%) and the sum of basic cations (SBC : Al) were determined. The soils analysed were characterised by an extreme and strong acid reaction (pHCaCl2: 2.75–4.60). Regardless of time, the highest TOC content in the closed layer was found in the Krotoszyn forest area under the Quercus robur L. on the Stagnosol soil and the lowest in the Strzałowo forest area under the Pinus sylvestris L. stands on the Halpc Luvisol soil. The TOC content in the mineral layers was low regardless of the location and year of investigation and was similar in the analysed soils.
Most of the forest soils analysed were poor sites and soils from sands with low alkaline cation content (SBC<5.0), sorption capacity (CEC) and saturation of the alkali-sorption complex (BS < 20%).