The Effect of Stand Age on Throughfall Chemistry in Spruce Stands in the Potok Dupniański Catchment in the Silesian Beskid Mountains, Southern Poland

Abstract

The chemical composition of throughfall depends on the age of the Norway spruce (Picea abies Karst) stands and season of the year. The pH of throughfall decreased and the amount of hydrogen ion in throughfall deposited to the soil increased with increasing age of spruce stands, especially in the winter season. Concentrations of K⁺, H⁺, SO₄²⁻, Mn²⁺, and NH⁴⁺ in throughfall were higher than bulk precipitation for the whole year and K⁺, H⁺, and Mn²⁺ concentrations were higher in throughfall in winter and the growing season. This indicates that these ions were washed out or washed from the surface of needles and/or the bark, and that NO₃⁻, NH⁴⁺, Ca²⁺, Mg²⁺, Fe²⁺, and Zn²⁺ were absorbed in the canopy. The effect of high nitrogen deposition, above critical loads, and an increase in the amount of sulfur and in the sum of the strong acids (S-SO₄²⁻ and N-NO₃⁻) that reached the soil with throughfall may have implications for the vitality of spruce stands, especially in older age classes. The application of Principal Component Analysis (PCA) has led to identification of five factors responsible for the data structure (“mineral dust”, “acidic emissions”, “heavy metals-dust particles”, “ammonium [NH₄⁺]”, and “H⁺”). They explain more than 60% of the total variance system. The strong positive correlation between stand age class and ionic concentrations in throughfall occurs for all year and the winter period for ions within the following categories: “acidic emissions”, SO₄²⁻ + NO₃⁻; “heavy metals-dust particles”, Fe²⁺ + Mn²⁺ + Zn²⁺; “mineral dust”, Na⁺ + K⁺ + Ca⁺² + Mg²⁺; “NH₄⁺”; and “H⁺”. The strength of the relationship decreases in the growing period, probably due to processes occurring in the canopy (adsorption, leaching, etc.).