Abstract

In this study, mineral nutrition and its relation to the vigour of Scots pines growing under the influence of sulphur, copper and nickel stress were investigated. This was done by analysing the nutrient status and needle damage of pines along a pollution transect extending from the proximity of a large S, Cu and Ni emitters on the Kola Peninsula to a background area in Finnish Lapland. Additionally, pine seedlings were exposed to Cu and Ni stress in order to gain more detailed information about the mechanisms behind metal stress.

The total sulphur concentrations of the youngest needles in the vicinity of the largest point source were about double compared to those in the reference area (< ;800 mg in kg of dry needles vs. > 1900 mg kg^-1). In the case of Cu and Ni, this difference was close to 100-fold (from 2-3 mg kg^-1 to over 250 mg kg^-1). While the elevated sulphur concentrations were not attributable to particle deposition, the particles on needle surfaces raised the total concentrations of Cu and Ni occasionally over 1.5-fold compared to the inside concentrations. The Mn and Zn concentrations showed a decreasing trend, whereas K and P slightly increased towards the Monchegorsk smelters. Enhanced needle senescence and tip necrosis were related to high total foliar levels of Cu, Ni and S and low levels of Zn and Mn. Stomatal chlorosis and other discolourations showed a distinct relation to high SO₂ levels in the air and also to high foliar concentrations of Ca, Fe, Si and Cl. Particles deposited on needle surfaces did not cause directly visible injuries in pines.

In seedlings, Cu and Ni were enriched in roots: the Ni concentration was up to 16-fold and the Cu concentration 6-fold compared to that added into the soil. While Cu was mostly retained in roots, Ni had much easier access to foliage. The effect of metal stress on other nutrients varied between nutrients, plant parts and metals added. Soil analyses from both the field study and the seedling experiment gave mostly a weak estimation about the plant availability of nutrients. Foliar nutrients remained above the deficiency limits in all studies and were hence not the primary cause for the decrease of pine vigour and the consequent growth retardation and forest decline.