Effects of ambient ozone on seedlings of Fagus sylvatica L. and Picea abies (L.) Karst

Abstract

SUMMARYThe effect of unfiitered versus filtered air was tested on tree seedlings at different sites with prevailing ozone pollution, at different altitudes. Growth and biomass data from different experiments were evaluated in relation to ozone dose above 40 nl T^ during the exposure time. In beech {Fagus sylvatica L.), biomass was significantly correlated with ozone dose whereas shoot length was not. There was no change in shoot/root ratio but there were more significant reductions in fine root biomass than in shoot biomass. The effect of ozone was cumulative within the duration of the experiments, i.e. from a few months to three years. A cumulative dose of 7 //I T' h > 40 nl 1"' per growing season, calculated for 24 h day"', corresponded to a 10% biomass reduction within three years. Seedlings grown in unfiitered air also exhibited much more severe symptoms of frost injury following a cold winter with rapid temperature change. Laboratory experiments suggest that winter desiccation may have played a more important role than low temperatures, but that medium frost temperatures may cause more latent injuries in seedlings exposed to ambient air. Water loss of detached leaves from unfiitered air was significantly higher later in the season. Both increased chlorosis and premature leaf fall were observed in the beech seedlings grown in unfiitered air, but in different years. The biomass of spruce \Picea abies (L.) Karst.] showed a tendency towards a reduction, but this was not significant within the dose range tested. Three years of fumigation, however, caused increased chlorosis also in the spruce seedlings. Tests with low temperatures suggest that the vitality of the spruce seedlings during winter may also be impaired by the ambient air pollution.

Responses to ozone in 12 provenances of European beech (Fagus sylvatica): genotypic variation and chamber effects on photosynthesis and dry‐matter partitioning

“…This confirms most previous results on trees growing in ozonepolluted air (Taylor & Ferris, 1996). Three previous studies have dealt with ozone-reduced biomass increments in roots of well watered beech seedlings, all of which found reductions in root biomass from 12 to 34% at realistic exposure levels (Taylor & Davies 1990 ;Davidson et al 1992 ;Braun & Flu$ ckiger, 1995). We believe that the 25% reduction in root d. wt of the provenances used in the present study would have been statistically significant (P l 0.06) had it not been for the natural variation in size within the provenances.…”

“…As for other tree seedlings, beech responds to O $ by reduced photosynthesis (Mikkelsen, 1995 ;Lippert et al, 1996 ;Zeuthen et al, 1997) and growth (Davidson et al, 1992 ;Braun & Flu$ ckiger, 1995 ;Krause & Ho$ kel, 1995). Experiments with beech were used to determine critical levels for ozone effects on forest tree growth (Ka$ renlampi & Ska$ rby, 1996).…”

Impacts of ozone on forests: a European perspective

“…Commonly, growth reductions or premature senescence are reported within one exposure season (birch, Matyssek et al (1992, Pa$ a$ kko$ nen, Holopainen & Ka$ renlampi (1995 a, 1997 a), Pa$ a$ kko$ nen et al (1995 b, 1996) ; American aspen (Populus tremuloides), Keller (1988) ; hybrid poplar (Populus euramericana), Matyssek et al (1993), Mooi (1980)). European beech is also O $ -sensitive, and growth reductions and premature senescence have been detected in several recent studies (Ku$ ppers et al, 1994 ;Pearson & Mansfield, 1994 ;Braun & Flu$ ckiger, 1995 ;Krause & Ho$ ckel, 1995 ;Steingro$ ver et al, 1995 ;Mikkelsen & Jorgensen, 1996 ;Mortensen, Bastrup-Birk & Ro-Poulsen, 1996). Amongst the most widely planted conifers, Sitka spruce (Picea sitchensis) showed reduced growth after two 13-wk seasons of O $ exposure and this negative effect was still detectable in the third year, in which there was no O $ exposure .…”

“…Amongst the most widely planted conifers, Sitka spruce (Picea sitchensis) showed reduced growth after two 13-wk seasons of O $ exposure and this negative effect was still detectable in the third year, in which there was no O $ exposure . Experiments with Norway spruce (Picea abies ) seedlings, by contrast, showed no significant effects on growth following several seasons of O $ exposure, although indications of decrease were found in both cases (Braun & Flu$ ckiger, 1995 ;Ska$ rby et al, 1995). These results of Wellburn et al (1997) indicate that trees, unlike annual crops, show carry-over effects on growth and suggest that it is most likely that observed effects in trees reflect cumulative processes developed over several growing seasons.…”

“…Biomass data from three different OTC studies using European beech have thus been used for the estimation and determination of a critical level of O $ for all forest trees (Ku$ ppers et al, 1994 ;Braun & Flu$ ckiger, 1995 ;Steingro$ ver, Dueck & Van der Eerden, 1995). The critical level for beech was defined as an AOT40 of 10 nl l −" h accumulated over a 6-month growing season and calculated for daylight hours only.…”