We investigated the effects of several tree species on dehydrogenase and urease activities in soils derived from two different parent materials (glaciofluvial sand and loess) in forested areas in southern Poland. We hypothesized that coniferous forests (pine, spruce) alter the soil cation exchange capacity (CEC) and decrease soil pH and, therefore, might decrease soil enzyme activities compared with broadleaf species growing on similar soils. Eight paired plots (12 · 12 m) were established on glaciofluvial sand in pine (Pinus sylvestris) + oak (Quercus robur) and spruce (Picea abies) + pine stands, as well as on loess-derived soils: beech (Fagus sylvatica) + pine and hornbeam (Carpinus betulus) + pine stands. Each plot was a 4 · 4 m grid with 16 sampling points. In soil samples pH, soil texture, and organic carbon, nitrogen, base cation contents, dehydrogenase and urease activities were determined. On both parent materials, the soil pH was lower under coniferous species than under broadleaf species. The acidifying effect of tree species on sandy soil was in the order of spruce = pine > oak, while that on loess was pine > beech > hornbeam. Hornbeam and oak increased the soil pH and stimulated enzyme activity in the soil. The content of fine fraction enhanced potential enzyme activities in soils, thus the loess soils had greater dehydrogenase and urease activity. The results suggest that pine stores more soil organic C in association with silt increasing the pool of stabilized soil organic C.

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Forestry works using chainsaws result in up to 7 million liters of various mineral oils being soaked annually into forest soils. These substances, containing a complex mixture of polycyclic aromatic hydrocarbons (PAHs), are highly toxic. The aim of the study was to determine the effect of oil contamination with PAHs on the physical and biological properties of forest soils. The study area was located in southern Poland in the Miechów forest district. The experiment was conducted on four treatment blocks with various amounts of oil addition. The study included the determination of PAH content, dehydrogenase and urease activity, and biomass of earthworms. Physical properties were determined using the dryer method and Kopecky rings of 250 cm3 volume. The results obtained confirmed the hypothesis that oil contamination with PAHs modified the physical properties of forest soils and oil had a negative impact on enzyme activity in soil. Enzyme activity in the studied soils was negatively correlated with PAH content. Earthworm population density reflected the contamination level of oil-contaminated soils.

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Abstract. the aim of this study was to assess the effects of different types of land use (forest, tillage and pasture) on soil properties, especially enzyme activity. Our investigation was carried out on 53 research plots with 11 plots in broadleaved forest stands, 12 plots in mixed broadleaved stands, 10 plots in mixed coniferous stands, 9 plots on tillage and 11 plots on pasture. the soil samples were collected from a depth of 0-15 cm after removing the organic horizon. Contents of organic carbon and nitrogen, pH and soil texture were investigated. Furthermore, dehydrogenase and urease activity were determined. Significant differences in the enzyme activity between forest and agricultural soils were observed, thus demonstrating that enzyme activity is influenced by the organic matter content of the soil. the highest enzyme activity was recorded in the forest soil within broadleaved stands, whilst the lowest activity was found in tillage soil, because tillage soil contained significantly less organic matter. High enzymatic activity of pasture soils is the combined result of vegetation type and the lack of plowing.