Chemical properties of soils and stream waters in the Kościeliska Valley

The Tatra Mts., the highest mountain range of the Carpathians, have been affected by large-scale forest disturbances in recent years. Windthrow, which occurred in the western part of the Tatra Mts. in 2013, was followed by a bark beetle outbreak. The aim of the study was to determine the response of inorganic N concentrations in soil and stream water to the natural succession of forest disturbances in three small catchments: forested (F), bark beetle (BB) and windthrow deforested (WD). The limited uptake of NO₃^- by trees in disturbed catchments resulted in significantly higher NO₃^- concentrations in the surface soil horizons of disturbed catchments, especially the in O horizon in the BB catchment compared to the F catchment. The limited uptake of NO₃^- in disturbed catchments is particularly evident in spring when the surface soil horizons are further enriched with NO₃^- from melting snow. High NO₃^- concentrations in stream water occur in the BB catchment, whereas low NO₃^- concentrations occur in the WD catchment. A key role in the high supply of NO₃^- to the stream in the BB catchment is played by the soil O horizon due to its high permeability and ability to flush out of NO₃^-. Nitrification does not seem to be an important process for the supply of NO₃-N to the soils. The soils do not differ in nitrification intensity either in spring or in autumn in all studied catchments. Furthermore, the results indicate that N immobilisation occurs in the soils during spring. High ammonification rate in the A soil horizons of both disturbed catchments is the key source of NH₄⁺ in stream water in autumn, whereas low ammonification rate reduces NH₄⁺ supply to streams in spring.