Dendrochronological analysis of the growth and growth-climate relationships of conifers in the region of alkaline dust deposition

Relationships between climate and radial growth of Oxalis-Myrtillus-site type Norway spruce and Scots pine stands under different cement dust loads were investigated. Dendrochronological methods were used. Long-term alkaline (pH 13.2-12.7) dust pollution emitted over 40 years from a cement plant was the reason of alkalisation (pH 7.8-8.1) and high concentrations of K, Ca and Mg in soil of affected territories. Two study sites, Kunda and Malla (2.5 and 5.0 km E from the emission source), were influenced by the dust emissions of the cement plant. Two other study sites, Eru (38 km W) and Revoja (34 km W), were situated on a relatively unpolluted area and served as control sites. The relationships between the radial growth and climate were almost similar on the control and dust-polluted sites. The climatic variables that had a significant effect on the radial growth of Norway spruce at both control and polluted sites were the temperature and precipitation of summer months of the current and preceding years. Specific to the Scots pine stands growing under dust pollution was a significant positive impact of the current spring temperature on the radial growth. A positive effect of precipitation during winter months on the radial growth was found at all sites. A significant negative effect of cement dust on the radial growth of Scots pine stands during the period of large amounts of dust emission (1966-1991) was detected. The effect of cement dust emissions on the radial growth of Norway spruce stands was also negative but weak. The decrease in the dust emissions since 1992 improved the growth conditions at pine stand sites.