Relation between photosynthetic photon flux density [PPFD] and growth of silver fir [Abies alba Mill.] seedlings in a forest stand dominated by spruce [Picea abies [L.] H.Karst.] in the Sudety Mts [SW Poland]

The relations between Photosynthetic photon flux density (PPFD) and both the number of silver fir (Abies alba) seedlings per unit area and their height growth were investigated. The study was carried out in the Sudety Mts (SW Poland, 50º28’N, 16º19’E), in a forest stand dominated by spruce (Picea abies), growing on site of mixed broad-leaved mountain forest. This site type is very commonly colonized by silver fir in this part of Europe. The number of fir seedlings per unit area decreased with growing PPFD values, whereas seedling height increased. Our results suggest that greater access of sunlight, at least within the recorded PPFD range (0−40% of full irradiation) improves the growth conditions of fir seedlings but at the same time the spread of grasses (mainly Deschampsia flexuosa) inhibits the rooting and development of new seedlings. Thus regenerative felling should be conducted in forest stands in these places where fir seedlings are numerous.