Problemy diagnozy troficzności siedlisk leśnych na porolnych glebach aluwialnych

The morphology and properties of the post−arable soils that influence the trophic status of forest habitats on the Barycz river terraces (south−western Poland) were analyzed. The fieldwork included the characterization of the soil, tree layer, and the vegetation of the forest floor, as required for the forest habitat evaluation. In the collected soil samples, a set of physico−chemical analysis was carried out, that included: soil texture, bulk density, pH in KCl and water, total organic carbon, total nitrogen, hydrolytic acidity, base cations, and the content of plant−available phosphorus, potassium, and magnesium. Sandy post−arable soils in the Barycz valley have a thick, double− or triple−layered ploughed humus horizon, and the high stock of humified organic matter, nitrogen, and phosphorus, that emphasizes anthropogenic transformation of soils and differentiates them from the natural soils of river valleys. The diagnosis based on the soil trophic index (SIG) indicates generally lower trophic status (mesotrophic) as compared to the diagnoses based on forest floor vegetation and tree−stand (eutrophic status). The SIG model for the post−agrar moist valley habitats should be supplemented with the factors, which improve the apparent trophic status of sandy soils, including the thick humus horizon (post−ploughing) and shallow table of eutrophic ground water.