G. Wieser et Wm. Havranek, EXPOSURE OF MATURE NORWAY SPRUCE TO OZONE IN TWIG-CHAMBERS - EFFECTS ON GAS-EXCHANGE, Proceedings of the Royal Society of Edinburgh. Section B: Biological sciences, 102, 1994, pp. 119-125
Little is known about ozone (O-3) effects on adult trees in the field,
where ecophysiological parameters control pollutant uptake. It was th
e goal of this study to examine how ambient and above ambient O-3 conc
entrations affect gas exchange of mature Norway spruce (Picea abies (L
.) Karst.). Therefore, twigs were enclosed in chambers and exposed to
different O-3 concentrations for one and two seasons over three years.
During winter periods twigs were maintained under ambient conditions.
Data from the shade crown of spruce trees at 1000 m a.s.l. are presen
ted. After one and two fumigation periods no clear treatment effects o
n gas exchange were observed in twigs fumigated with O-3 concentration
s ranging from zero up to ambient (A)+60 ppb. However, O-3 at 90 ppb r
educed photosynthesis and conductance. CO2 response curves indicated t
hat in A+90 twigs the efficiency of CO2 uptake was diminished. Observe
d losses in P-n of A+90 twigs were greater than reductions in conducta
nce indicating that stomatal closure alone did not limit CO2 uptake. W
e conclude that ambient and slightly above ambient O-3 concentrations
do not alter gas exchange of mature Norway spruce. Therefore, supposit
ions on O-3 damage on mature spruce trees should be critically questio
ned.