CRITICAL LEVELS OF O-3 FOR WOOD PRODUCTION OF EUROPEAN BEECH (FAGUS-SYLVATICA L)

During recent decades, ozone (O-3) has gained much attention as a poss ible contributor to forest decline. Attempts have been made to set cri tical levels for O-3 in order to protect vegetation. Damage to vegetat ion seems to depend on the pattern of exposure. Episodic peaks followe d by periods with low concentrations are more phytotoxic than exposure s with generally elevated concentrations but without peaks. The presen t experiment aims to examine whether O-3 affects the wood production o f beech seedlings. The seedlings were exposed to three different air p ollution regimes: charcoal-filtered ambient air (CF), non-filtered amb ient air (NF), and NF + 30nl (1-)1(-1) O-3 8 hours day(1) during summe r periods (NFO). Basal stem diameter was measured regularly during thr ee growing seasons. The relative diameter increase was significantly r educed with increased O-3 concentration. AOT40 is calculated for all t reatments and evaluated in relation to the relative diameter growth.