The spatial pattern and microsites requirements of Abies alba natural regeneration in the Karkonosze Mountains

Progeny of four adult silver firs, which were an admixture in Norway spruce (Picea abies) stand was, analyzed. The study was done in lower mountain zone of the Karkonosze (Giant Mts.) National Park (SW Poland). The seedlings occurred in two clumps related to the position of adult trees, whereas spatial pattern of the seedlings inside each clump was random. The seedlings were spaced mainly in distances 5–25 from the nearest adult tree. The maximal distance was up to 50 m. Most seedlings were established in accordance with main wind directions. Also, in these directions seedlings were more distant from adult trees than in other directions. The seedlings grew in better light environment (12% of PPFD) than average (9,6% PPFD). This effect was statistically significant. The height increment of the seedlings was low and was not correlated with light conditions. Similarly, there was not any correlation between the apical dominance ratio and light. The lack of this correspondence we attributed to browsing. The silver fir seedlings were significantly underrepresented in patches of Vaccinium myrtillus, on raw needles, under crown of adult trees and in concave micro-relief form. The underrepresentation in the places covered by canopy and in patches of bilberry we related to the indirect effect of continuous browsing, which leads to higher seedlings mortality in more shaded places and sites of stronger competition between forest floor vegetation and silver fir seedlings.