Photosynthetic activity of Fagus sylvatica L. and Quercus petraea (Matt) Liebl. in a mixed stand at Maljen mountain
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Estimation of the photosynthetic performance of co-existing tree species with pronounced differences in ecophysiological context (Aranda et al. 1996 Leuschner et al. 2001) could provide insight into their vitality and competitive abilities at a particular site. Gas exchange, composition of photosynthetic pigments, and the water status of beech (Fagus sylvatica L) and sessile oak (Quercus petraea (Matt) Liebl) were studied in the present work. The investigation was performed on Mt. Maljen (Western Serbia, near the town of Mionica) at an altitude of 950 m, in an ecotope within the confines of the mountain's beech forest belt. Codominant samplings [three of each species, 30-years old (n=6), 10-12 m high] were selected for the measurements, which were conducted on fully developed leaves from the outermost branches and from the innermost canopy. Photosynthetic measurements were performed using an LI-6200 closed photosynthesis system (LI-Cor. Inc, Lincoln, NE, USA), while irradiance was detected with a selenium cell mounted on the leaf chamber. Parameters of gas exchange are expressed on the basis of leaf area, using the AREAMETER software (Karadžić et al. 1999). Chlorophyll content was spectrophotometrically determined based on light absorption of the solution obtained after extraction with dMSO (Hiscox and Israelstam, 1979). The midday water saturation deficit was determined according to Turner (1981). For data analysis, we used the Statistic for Windows program package. The ANOVA one-way breakdown was applied to compare differences within (leaves inside vs. leaves outside the surface of the tree canopy) and between species for all investigated parameters at the 0.05 level of significance.