Response of Fagus sylvatica L. and Abies alba Mill. in different silvicultural systems of the high Dinaric karst

Among all silver fir forest types in Slovenia, most changes in forest composition are evident in Dinaric silver fir and beech forests, in which ageing and reduction of silver fir populations compared to European beech is evident. The situation has worsened due to a high browsing rate and environmental changes, causing a decline in abundance and a shift in silver fir's spatio-temporal distribution. The photosynthesis response to different light and CO2 (max. photosynthetic rate - A(max), compensation points - I-c, quantum yield - Phi), the morphological response in young beech and fir to shade, and the growth response of adult trees were compared on sites with a single selection method, group selection method and old growth, during three consecutive vegetation periods (2009, 2010 and 2011). Three plots were established on each site, each with comparable light conditions according to the indirect site factor - ISF (%) under mature shelter, forest edge and open light conditions. In the old growth forest, beech and fir were more shade-tolerant and had a greater reaction to different light levels or elevated CO2 concentrations, compared to managed forest sites. Fir and beech express more physiological and morphological shade-tolerant characteristics on sites with single selection treatment, and differences are also evident in the growth responses of the two species. To establish conditions under which fir would be able to compete with beech, longer regeneration periods should be applied, with a gradual opening of the mature canopy, similar to conditions in old growth. In our study, group selection treatment proved more effective under the present environmental conditions. (C) 2012 Elsevier B.V. All rights reserved.