Old-growth versus selection forest management in mixed fir–beech forests: Insights from 70 years of monitoring in the Dinaric Mountains

Selection management has a long tradition in the Dinaric region, yet its long-term effects on the structural and compositional dynamics of mixed fir–beech forests remain insufficiently quantified. This study uses long-term permanent plot data to compare one unmanaged old-growth forest stand with two nearby stands that have been managed under a selection system for approximately 70 years. Low levels of ungulate browsing in the study area ensured that the observed stand dynamics primarily reflected silvicultural practices rather than herbivore impacts. The unmanaged stand maintained a stable uneven-aged diameter structure and sustained the dominance of silver fir in terms of basal area, while gradually shifting toward increased dominance of European beech. In contrast, the managed stands developed from simplified, unimodal diameter distributions into structurally differentiated distributions characteristic of uneven-aged mixed-species forests. Although harvesting reduced growing stock, cumulative stand increment exceeded removals throughout the study period, resulting in a net accumulation of biomass. Our findings indicate that long-term selection management was associated with structural diversification, sustained productivity, and a balanced species composition in forests with an old-growth legacy. Nevertheless, contemporary old-growth forests remain rare and irreplaceable ecological reference systems. The observed developmental trajectories further demonstrate that structural adjustment in uneven-aged mixed forests is a gradual process that may unfold over several decades, underscoring the importance of long-term monitoring for evaluating the sustainability and resilience of selection-managed forests.