Ionic deposition and chemistry of soil solutions in a forested study area in the Chojnów Forest District in the years 2004-2007

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The study was carried out in the years 2004-2007 in a permanent observation plot established in a pine tree stand growing in a mixed fresh coniferous forest habitat of the Chojnow Forest District. Analyses pertained to the deposition of mineral compounds delivered to soil with bulk precipitation in the open field and throughfall and to chemical compositions of soil solution at a depth of 25 cm and 50 cm. pH, electrical conductivity and concentrations of Ca, Mg, Cl, NO₃, SO₄, Na, K, Fe, Mn, NH₄, PO₄, Zn, Cd, Cu, and Pb were analysed in precipitation and in soil solution samples.Total load of ions under the canopy of pine trees ranged between 47 and 61 kg·ha⁻¹·year⁻¹. Acidifying ions (N + S + Cl) contributed in 51% to the total ionic load (in molc·ha⁻¹·year⁻¹) while base ions (Ca + Mg + Na + K) in only 36%. Respective percentage contribution in bulk precipitation was 69% and 19%.No relationship was found between the chemical composition of soil solutions (at both depths) and the chemical composition of precipitation waters. Analysed soil solutions were acidic (average pH at the depth of 25 cm and 50 cm was 4.3 and 4.4, respectively) and the molar ratio of the sum of base cations (Ca, Mg, and K) to Al in the majority of examined samples from the upper soil layer, was much lower than 1. This is the evidence of low buffering capacities of analysed soil in relation to acidifying loads and indicates a potential threat for the pine stand stability.