Microstructure of humus horizons of gypsic soils from the Niecka Nidziańska area (South Poland)

Abstract

The microstructure of the humus horizons of gypsic soils belonging to lithic, mollic and cambic rendzic Leptosols [FAO/UNESCO, Soil Map of the World. ISRIC, Wageningen, 1997.] from the Niecka Nidziańska area (South Poland) was studied. Soil samples were collected from humus horizons of 24 profiles of soils which differed in many ways such as geomorphological position (on slopes with north or south exposure and on flat terrain); depth of profiles (shallow and deep soils) as well as land use (arable and covered by natural vegetation). The following properties were determined: pH, the level of organic carbon, the total nitrogen, clay content and CaCO 3 content. Thin sections were made of undisturbed soil samples. The investigated soils were characterized by considerable biological activity and abundance in humus with varied microstructures. Regarding microstructures, the investigated soils were divided into four groups. The first group consists of shallow rendzinas from the southern slopes, overgrown with feather-grass steppe with a fine-pelleted humicol microstructure formed mainly of isotropic aggregates of animal origin, mainly pellets of Oribatei and Collembola and less numerous of Enchytraeidae. The second group is formed by soils of the northern slopes covered by grass with sesleria, sedge and anemone with a coarse-pelleted humicol microstructure made up of fecal pellets of Collembola, Coleoptera larvae, Enchytraeidae and Diplopoda. Deep grassland soils rich in perennial dicotyledonous plants from the flat areas with a fine-pelleted mullicol microstructure show abundant effects of the activity of Lumbricidae, Enchytraeidae, Diplopoda, and larvae of Coleoptera and Diptera forming a very porous material which belongs to the third group. Medium deep and deep arable soils with a spongy mullicol microstructure that is of mixed organo-mineral colloidal complexes with visible grains of skeleton belong to the last group.