Drivers of silver fir regeneration success: Interactions between site conditions, game browsing and close-to-nature forest management

Silver fir (Abies alba Mill.) is an ecologically and silviculturally important tree species in Central European forests due to its high production potential and increasing relevance under ongoing climate change. Therefore, its regeneration and promotion are of key importance for both ecosystem functioning and sustainable forest management. This study evaluates the potential of natural (four localities) and artificial (ten localities) regeneration of silver fir under close-to-nature silviculture across two natural forest areas (Křivoklátsko and Český kras; Brdská vrchovina) at altitudes of 362-570 m a.s.l. in Czechia. The objective was to assess the growth potential of fir regeneration across six contrasting site type categories on 62 research plots: acidic (3K, 4K), nutrient-rich (3B), loamy (3H), nutrient-medium (3S), gleyed nutrient-medium (4O) and gleyed acidic (4P) categories; and to quantify game browsing damage. The highest natural regeneration density was recorded on 4O sites, reaching on average 182 800 pcs.ha-1, while the lowest density was observed on 4P (25 600 pcs.ha-1). Compared to the overstory composition, regeneration layers showed a marked increase in the proportion of silver fir. In contrast, the highest annual height increment of natural regeneration was found on 4P (10.6 cm), significantly exceeding that on 3S (2.1 cm). Browsing damage ranged from 11.0% (3S) to 19.2% (4O). In terms of artificial regeneration, the highest annual height increment was recorded at site type 3H (38.4 cm), whereas the lowest was observed at site type 3B (15.2 cm). Our results show that fir regeneration is mainly driven by site conditions and ungulate browsing, providing a basis for targeted silvicultural and game management to support its long-term persistence.