Effect of Industrial Airborne Pollution on the Chemical Composition of Pine Needle Litterfall at the Northern Distribution Limit of Pine Forests

摘要

This paper examines the chemical composition of Scots pine litterfall in north taiga pine forests in background conditions and under the impact of emissions from the Severonikel copper-nickel industrial complex. In forests exposed to industrial airborne pollution, the content of fertilizer elements (Ca, Mg, Mn, and Zn) in coniferous litterfall decreases, while the content of heavy metals (Ni and Cu) and values of stoichiometric C/P and N/P ratios increase. This indicates that the quality of plant material to be decomposed by soil biota declines. In background conditions, intrabiogeocoenotic differences in the chemical composition of coniferous litterfall are manifested in a higher content of K and P (supplied with crown and trunk waters) under tree crowns; in intercrown spaces, concentrations of Fe, Zn, Ni, and Cu are higher due to background airborne pollution. In defoliating forests, coniferous litterfall under tree crowns contains more Ca, Mg, K, Mn, P, N, and S due to the intensive leaching of fertilizer elements from tree crowns by acidic precipitation and, as in the case of sulfur, due to its inflow with acidic precipitation. The elevated content of N, P, and K in coniferous litterfall of defoliating forests can be determined by high concentrations of these mobile elements in living needles falling off ahead of normal phenological terms. In background conditions, seasonal variability of the chemical composition of coniferous litterfall in defoliating forests is manifested in high Ca and Mn concentrations in needles due to their accumulation there by the end of the warm season. In sparse technogenic forests, Mg and K accumulate in coniferous litterfall by the end of the growing season, which indicates a disturbance of retranslocation processes under the impact of pollution. In all studied pine forests, the content of Fe and Zn in litterfall significantly decreases by the end of the warm season; in forests exposed to airborne pollution, the content of Ni and Cu decreases as well. This can be explained by their antagonism with Mn and leaching from needles by acidic precipitation during the warm season.