Ozone fumigation of norway spruce at timberline : Air Pollution and Forest Decline. 14th International Meeting for Specialists in Air Pollution Effects on Forest Ecosystems

1989

S. 550-552

3 Abb., 15 Lit. Ang.

Unselbständiges Werk

200034877

Twigs of a 60 year old Norway spruce (Picea abies (L.) Karst.) were encolsed in ranging period. CO2 gas exchange, stomatal conductance and chlorophyll flourescence of these twings were compared under defined conditions. In no case O3 caused a decrease in stomatal conductance. Low O3 doses rather seem to increase conductance at least temporarily. Net photosynthesis was not significtly influenced after a fumigation perid of 4 or 8 weeks. Also after 12 weeks background levels of O3 in ambient air (mean 65 ppb O3 in 1986, 64 ppb O3 in 1987) had not altered photosynthesis compared to O3, free controls. O3 concentrations higher than 100 ppb however led to a significant decline in not photosynthesis. As O3 concentrations in the experimental area at timberline near Innsbruck, Austria, often exceed 100 ppb even for extended periods in summer, negative effects on photosynthesis and tree growth are to be expected.