Biochemical and structural characteristics of Scots pine (Pinus sylvestris L.) in an alkaline environment

Investigations in a 75-85-year-old Scots pine stand were performed on a territory influenced over 40 years by alkaline dust pollution (pH 12.3-12.7) emitted from a cement plant. Sample plots were located at distances of 2, 3, and 5 km E of the emission source and a control sample plot was selected on an unpolluted territory 38 km W of it. We studied soil properties and the anatomical structure, mineral nutrition, and pigments in Scots pine needles. The alkaline dust pollution has affected the biogeochemical cycling in the forest ecosystem, increasing the pH and total Ca, K, Fe, Mn, and Mg and decreasing N, C, organic matter, and C/N compared to the unpolluted soils. Alkalization and changes in the nutrient composition of soil had caused serious disbalances in nutrient availability and in the mineral composition of trees. Deficiency in foliar N and Mn and excess of K, Ca, and Fe contents had caused a decrease in the average chlorophyll concentrations. Carotenoids seemed to be more tolerant both to changes in soil and needle nutrient composition. The Chl a/Chl b ratio in needles was found to have declined. With the alkalization of the environment the total area of the needle cross-section, needle thickness, and mesophyll area had also decreased compared with control. Differences in the anatomical characteristics of needles between the polluted and unpolluted areas were significant in the oldest needles. The decrease of mesophyll was associated with the content of chlorophylls and correlated with N concentrations in needles.