The paper presents results of a 3-year-long study (2012-2014) into the nitrogen and phosphorus bioaccumulation in 22 plant species associated with mid-forest headwater streams and in 10 plant species associated with peatbogs in the valley of the Kamienna Creek, a left bank tributary of the Słupia River, northern Poland. Plants were sampled in May, July and September of each year from three locations along the streams and three locations within the peatbogs. Every month stream water and ground water were sampled in the same locations using 30 cm piezometers. The content of nitrogen and phosphorus was determined in the  plant and water samples. In the plant samples, total nitrogen was assessed with the Kjedahl method and phosphorus was determined with the molybdenum method. Concentrations of NH4+, NO2-, NO3- and PO43- in ground water samples were determined using ion chromatography. Stream and ground water contained low concentrations of mineral forms of these elements, which is associated with the strongly limited influence of anthropogenic factors and almost complete afforestation of the creek’s catchment. Despite this, the supply of plants with nitrogen and phosphorus was sufficient, which is confirmed by the concentrations of these elements in plants. However, peatbog plants accumulated the elements more intensively. The highest accumulation of nitrogen and phosphorus was found in the shoots of Urtica dioica. Among the stream plants, Brachythecium rivulare and Carex remota accumulated the least nitrogen. The average N:P ratio in plants, which was

23.2.2018