Vertical gradients of mineral elements in Pinus sylvestris crown in alkalised soil

Abstract

Alkalisation of soil has been assumed to be the principal cause of changes in vertical gradients of nutrients in Pinus sylvestris crown. The long-term influence of alkaline dust pollution (pHH2O 12.3-12.6) emitted from a cement plant on the element composition of soil and needles of Scots pine in different canopy layers was studied. In the polluted area, the pH of soils was >7, and high amounts of Ca, K and Mg were measured in the upper layers of soil (0-30 cm), while the mobility and solubility of some contaminants have decreased, nutrition processes have become complicated, and imbalance of mineral composition of trees was revealed. Reduced N and increased K, Ca and Mg concentrations in needles were observed in the heavily polluted area. Vertical gradients of elements and their ratios in canopies varied depending on the alkalisation level of soil. Needles on the upper-crown shoots had higher concentrations of N, C, Ca and Mg and lower concentrations of P and K compared to the lower layer of the crown. In the unpolluted area, higher concentrations of N, P, K and Ca were found in lower-crown needles and of C and Mg in needles at the top of the canopy. The P/N ratio below 0.125 indicated P deficiency in pines. The ratios N/Ca, N/Mg and N/K had significantly decreased, while the ratios Ca/Mg, K/Mg and K/Ca had a tendency to increase in heavily polluted sample plots. Magnitude of changes of element ratios indicates on the disbalances of availability and translocation of nutrients in the crown of trees.