Ozone phytotoxicity in the Western Carpathian Mountains in Slovakia

In this work, the response of temperate coniferous forests to ozone air pollution (O-3) in the mountain environment of the High Tatra Mts. (Western Carpathians) was analyzed. The modelling of stomatal O-3 flux is a complex method for the estimation of phytotoxicity of O-3 pollution to forest vegetation. Stomatal flux-based critical levels (CLef) for effects of O-3 on radial growth take into account the varying influences of O-3 concentration, meteorological variables, soil properties, and phenology. The application of the model DO3 SE (Deposition of Ozone for Stomatal Exchange) at five experimental plots with altitudes varying from 810 to 1,778 m a.s.l. along vertical and spatial profile in the High Tatra Mts. revealed the high phytotoxic potential of O-3 on spruce forests during the growing season 2014. The accumulated stomatal O-3 flux above a threshold of Y (1 nmol m(-2) s(-1)), i.e. POD1 (Phytotoxic Ozone Dose) ranged from 13.6 mmol m(-2) at the Kolove pleso site (1,570 m a.s.l.) to 16.2 mmol m(-2) at Skalnate Pleso site (1,778 m a.s.l.). CLef for POD1 (8 mmol m(-2)) recommended for the protection of spruce forests were exceeded at all experimental plots from early July. Similarly, AOT40 index suggests vulnerability of mountain forests to O-3 pollution. AOT40 values increased with altitude and reached values varying from 6.2 ppm h in Stara Lesna (810 m a.s.l.) to 10.7 ppm h at Skalnate Pleso close to the timber line (1,778 m a.s.l.). Concentration-based critical level (CLec) of 5,000 ppb h was exceeded from June to August and was different for each experimental site.