The influence of elevated CO2 on growth parameters of various provenances of European beech (Fagus sylvatica L.) at different irradiance

In a greenhouse experiment one year old seedlings of seven provenances of b eech (Fagus sylvatica L.) were grown under controlled conditions at two CO2 levels (350 ppm and 650 ppm) and different light intensities (2%, 17% and 100% relative irradiance). The response of the plants eo the various treatm ents was investigated by means of the leaf development during the growing s eason. At the end of the vegetation period leaf area and leaf dry weight pe r single leaf and per plant were measured. At the beginning of the growing period the provenances differed significant ly in height and at the end of the vegetation period also in the mean leaf number, leaf area and leaf dry weight per plant. The area per single leaf i s - in contrast to leaf dry weight and the specific leaf area - similar amo ng all seven provenances. The light has an effect on all measured leaf para meters. In full light the leaf development started very early. Leaf number, leaf area, and leaf dry weight per single leaf and per plant decrease and specific leaf area increases under low light conditions. In the treatment " elevated CO2 environment and full irradiance" leaf number, leaf area and le af dry weight per single leaf and per plant increased too. At reduced irrad iance a higher CO2 content does not influence the measured leaf parameters. The results show already at this early stage that the climatic factors infl uencing plant growth and elevated CO2 interact strongly. For an overall vie w of the plants' reaction to growth conditions, investigations of the gas e xchange of the leaves and anatomical and morphological studies will be adde d.