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IZVORNI I ZNANSTVENI ČLANCI – ORIGINAL SCIENTIFIC PAPERS Šumarski list br. 11–12, CXXXIII (2009), 569-576 UDK 630* 243 (001) PHOTOSYNTHETIC RESPONSE OFYOUNG BEECH (Fagus Sylvatica L.) ON RESEARCH PLOTS IN DIFFERENT LIGHT CONDITIONS FOTOSINTETSKI ODZIV MLADIH STABALABUKVE (Fagus sylvatica L.) NA ODABRANIM PLOHAMAU RAZLIČITIM SVJETLOSNIM UVJETIMA 12 Matjaž ČATER , Primož SIMONČIČ ABSTRACT: In view of evident changes in the reaction of European beech (Fagus sylvaticaL.) to environmental changes, five plots with young trees of the same age were established and studied on natural beech sites. Beech trees were equally distributed along the light gradient and were divided according to light conditions. The parameter used for evaluation of light conditions was the indirect site factor (ISF) obtained by the WinScanopy analysis. Three groups of canopy – light conditions were defined: stand conditions (ISF<20), edge (20 describing dependence between intercellular CO2concentration in leaves and assimilation rate (A-Ci) were measured under the same fixed parameters (temperature, flow and CO2concentration, humidity, and light intensity) with Li-6400, to compare responses between different light categories and different plots within comparable light conditions. Differences between canopy, edge and open area responses were confirmed with high significance on all plots as well as between studied forest complexes. On plots from Kočevje region, young beech indicated more shade tolerance, the response to increased light intensity and different CO2concentration was greater than the response of young beech on Pohorje plots within the same light intensities. Responses of trees on plots in managed and virgin forest were also different: young beech response in virgin forest plot was more shade-tolerant, compared to response of young beech from plots in managed forest. Key words: Beech, photosynthesis, light, CO, response 2 INTRODUCTION – Uvod The more frequent and intensive pressures to which cies predominate; in particular natural beech forests forests are exposed are connected with an increasing (Fagus sylvatica L.) (Kutnar 2003). The quality of number of extreme events and consequently higher existing and future beech forests is closely connected risk-rates of forest management decisions, especially on with our understanding of tree-response to different marginaland extreme sites.The importance of autocht-light conditions, especially in an environment of reduhonous tree species in preserving dynamic equilibrium ced light intensity under a mature canopy and in younger and stability in forest ecosystems is frequently emphasi-development stages. Such knowledge leads to correct zed (Zerbe 2002, Hannahet al. 1995, Stanturf and well-tuned spatial and temporal silvicultural measuandMadsen2002). In Slovenia, where forests cover res, which may vary among different silvicultural syover 60 % of the country, sites of mixed broadleaf spe-stems. It is also directed at sustainable development and a better future quality of forests (Kazda 1997). Solar 1 Dr. Matjaž Čater radiation, temperatures and precipitation which inf 2 Dr. Primož Simončič luence the distribution of plants are getting in times of Slovenian Forestry Institute,Večna pot 2, 1000 Ljubljana, matjaz.cater@gozdis.si intensive climatic extremes and climatic changes a new |