Tree rings as an indicator of atmospheric pollutant deposition to subalpine spruce forests in the Sudetes (Southern Poland)

Abstract

In spite of their moderate altitude (1000–1600ma.s.l.), the Western Sudety Mountains belong to areas with the most efficient fog precipitation in Europe. Intense industrial activity in the area of windward western foothills caused an exceptional intensification of atmospheric pollutant deposition via precipitation and fog to take place since the 1950s. In the second half of the 1970s a massive spruce forest dieback began affecting around 42% of coniferous forest in the Polish part of the Sudety Mountains. As the result of emission abatement in the region, gradual improvement of forest health status has been observed in the last decade. In October 2010 there were 70 dendrochronological samples collected from Norway spruce (Picea abies) stems at 7 different locations using an increment borer. It was documented for six sites that lowest annual growth rates took place between the early eighties and the early nineties which coincides with the highest pollutant deposition rates. Only one site representing the lowest parts of leeward slope showed gradual decrease of tree rings as a result of increasing tree age rather than due to an increase in ecological stress conditions. Tree ring widths were then compared with spatial distribution of fog frequency in the Western Sudety Mountains. The achieved results document a strongly negative dependence of tree ring widths on fog deposition rates. Spruce forest ecosystems have an ability to respond quickly to both negative and positive stimuli, related to increasing and decreasing environmental contamination.