The effects of ambient and elevated ozone levels on growth and photosynthes
is of beech (Fagus sylvatica) were studied by exposing seedlings in open-to
p chambers for one growing season to three treatments: charcoal-filtered (C
F), non-filtered (NF) and non-filtered air with addition of ozone (30 ppb o
zone) on clear days for 8-10 h d(-1)(NF+). Ambient levels were relatively r
ow and accumulated to an AOT40 (accumulated exposure over a threshold of 40
ppb) of 4055 ppb h (for the period 23 Apr-30 Sept). The NF+ chambers recei
ved an AOT40 of 8880 ppb h. Throughout the growing season we measured growt
h and photosynthetic properties. The treatments did not cause strong effect
s: measurements of gas exchange (light-saturated assimilation rate, CO2 and
light-response curves) and chlorophyll fluorescence showed slight and most
ly non-significant reductions of several parameters. No significant differe
nces were found for growth, though in the NF+ treatment (AOT40 8880 ppb h)
the relative growth rate for diameter increment was at times reduced by 12%
compared with the control treatment.