Ozone exposure-response relationships for biomass and root/shoot ratio of beech (Fagus sylvatica), ash (Fraxinus excelsior), Norway spruce (Picea abies) and Scots pine (Pinus sylvestris)

Current-year seedlings of beech, ash, Norway spruce and Scots pine were exp osed during one growing season to different, but moderate, ozone (O-3) scen arios representative for Switzerland (50, 85, 100% ambient, 50% ambient +30 nl l(-1)) in open-top chambers (OTCs) and to ambient O-3 concentrations in the field. Biomass significantly decreased with increasing O-3 dose in all species except for spruce. Losses of 25.5% (ash), 17.4% (beech), 9.9% (Sco ts pine) were found per 10 mu l l(-1) h accumulated O-3 exposure over a thr eshold concentration of 40 nl l(-1) during daylight hours (AOT40). Ratios o f root/shoot biomass (RSR) also significantly decreased with increasing AOT 40 levels in beech and ash, but not in Norway spruce and Scots pine. The da ta show that the deciduous species beech and ash were more susceptible to O -3 with respect to RSR and biomass than the coniferous species Norway spruc e and Scots pine. (C) 2000 Elsevier Science Ltd. All rights reserved.