EN
The aim of the study was to specify the direction and dynamics of changes occurring in forest soils in the area affected by Zakłady Azotowe 'Puławy' S.A. (nitriogen plant) on the basis of the activity of soil enzymes catalysing the key processes in the conversion of organic matter. The study involved examining the rhizosphere and non−rhizosphere soils in the monitoring plots, which consisted of Scots pine plantations mixed with birch and oak trees located within a medium forest damage zone (9, 15 and 17 km north−east from the plant) in the Puławy Forest District (eastern Poland). The research work was carried out in the years 2009−2013. Dehydrogenase, acid phosphatase, urease, and protease were determined along with selected chemical soil properties (pH and organic carbon content). The activity of studied enzymes and organic carbon content in the analysed soils significantly increased with increasing distance from the nitrogen plant. It was significantly higher inside than outside the rhizosphere. The observed biological activity of soils in the rhizosphere indicated that it formed a buffering system for environmental stressors, including those reaching the soils affected by industrial emissions. The soil of natural forest ecosystems with significantly higher organic carbon content than the remaining studied soils was characterised by the highest activity of all the enzymes observed during the monitoring period. The experimental plots were shown to have the highest activity of the analysed enzymes and the highest organic carbon content in the soil under the pine stands, and the lowest in the soil under the oak stands. The stability of the biochemical processes occurring in the selected experimental plots during the 5−year monitoring period and the clear tendency for the increasing activity of the analysed enzymes and organic carbon content over the study years indicate that the introduction of populations of pine mixed with birch and oak along the lines of the prevailing wind directions may improve the chemical and ecological state of forest soils in the area affected by the activity of the nitrogen source.