Leaving deadwood in the forest and the impact on the content of dissolved carbon, nitrogen and phosphorus in the forest soils

The aim of the study was to assess the losses of dissolved forms of DOC and selected nutrients, i.e. N-NO3, N-NH4 and P-PO4, as a result of their leaching into the soil under deadwood in selected forest reserves. The study was conducted in the following forest reserves of the Bialo- wieza Forest: Wladyslaw Szafer Landscape Reserve, Debowy Grad and Lipiny as well as outside these area in Koryciny Reserve. Soil samples were collected in the autumn of 2021 from litter (O) and mineral soils at a depth of 40 cm in several layers (0-5, 5-10, 10-2 and 20-40 cm). The pH in a soil solution of 0.01 CaCl2 center dot dm-3 (1:10) was measured potentiometrically and the total forms of P, K, Ca, Mg, Mn, Fe and Al were measured using ICP-OES. The water soluble forms of DOC, N-NO3, N-NH4 and P-PO4 (1:5) were determined colorimetrically. Studies have shown that leaving deadwood impairs the slow release of DOC, nitrogen and phosphorus into the soil solution due to the high cellulose content in woody plant tissue. The process of DOC uptake into the soil solution also depended on the amount of carbon (TOC) and nitrogen (Ntot) in the soil as well as the presence of ammonium (N-NH4) and phosphate (P-PO4) ions released during mineralisation of soil organic matter. It was shown that the dissolved forms of N-NO3, N-NH4 and P-PO4 can form stable complexes with Al and Fe. Further, it was shown that the content of DOC in soils can be an indicator of carbon fixation and its possible losses as well as changes in the forest soil environment.