Effects of air pollution and climate change on forests of the Tatra Mountains, Central Europe.

Synergistic effects of air pollution, extreme weather conditions and biotic agents related to global climate change have caused serious deterioration of forest condition in the Tatra National Park since early 1990s. Atmospheric deposition of sulfate (SO42−), nitrate (NO3−) and acidity (H+) are above the established critical load limits for forests. In addition, ambient ozone (O3) concentrations are also elevated mainly due to a long-range transport of polluted air masses. Ambient O3 concentrations have been monitored since 1992 with active UV monitors and passive samplers showing significant differences along the elevational gradient. High O3 values in spring indicate a potential for O3 stratospheric intrusion into troposphere. Ozone AOT40 index for protection of natural forest vegetation (10,000 ppbh) is commonly exceeded in the middle of vegetation period. Acidic impact may explain about 10–30% of a dieback observed in naturally oligotrophic Norway spruce (Picea abies) ecosystems probably due to acidification of soils leading to Al3+ mobilization limiting growth of fine roots. This may cause weakened resistance of trees to wind throws frequently observed in the foothills of the Tatra Mountains. Seventy year-long observations of meteorological conditions provide a unique opportunity for comparing current status of the Tatra forests within a context of long-term trends. Extremely high spring and summer temperatures, low precipitation and relative humidity observed during last decade are new factors disturbing ecological stability of natural and man-made forests. Warm and dry vegetation periods favor frequent bark beetle (Ips typographus) outbreaks affecting large areas of the Tatra forests. [ABSTRACT FROM AUTHOR]