Since the mid-19th century, Pinus nigra plantations have played a key role in the restoration of degraded European landscapes. Nowadays, these plantations are aging and prone to natural disturbances, insect infestations, and diseases. For their successful gradual conversion, knowledge of optimal gap spatiotemporal dynamics is crucial. We studied herb and natural regeneration patterns along with site factors on 477 subplots within 44 plots distributed over four stand types: closed stand (14% diffuse light), open stand (21%), gap edge (23%), and gap (57%). Despite the abundant Quercus petraea, Q. cerris, and Q. pubescens mast year, no one-year seedlings were recorded, which is likely due to the summer drought. Short seedlings (h < 20 cm) of Quercus sp., Fraxinus ornus and Ostrya carpinifolia were more successful within closed stands. Short Quercus seedlings were positively associated with soil depth and negatively associated with soil nutrients, distance to seed trees, and Sesleria autumnalis coverage. Taller Quercus seedlings required more light than both of its strongest competitors and were positively related to humid soils and less rocky sites. Ungulate overbrowsing significantly impeded natural regeneration. The results indicate a satisfactory Quercus density for conversion and the importance of advanced regeneration, which should be gradually, but persistently, released by progressively widening gaps.

Close-to-nature silviculture, based on natural regeneration, provides a suitable framework for the use of wildlings (naturally regenerated seedlings), enabling their direct collection and transplantation. Wildlings are a promising tool for small-scale forestry, difficult terrain, post-disturbance restoration and assisted range expansion, although their establishment success remains insufficiently understood under varying site and physiological conditions. This study evaluated survival and temporal dynamics of vitality of wildlings of Norway spruce, silver fir, and European beech planted in six experimental forest gaps in a temperate Alpine forest (Pohorje Mountains, Slovenia). A total of 162 wildlings were monitored across 12 repeated assessments between 2018 and 2025, combining data on survival, vitality, morphology and environmental conditions. Survival differed strongly among species, with Norway spruce showing the highest survival (59.3%), followed by European beech (50.0%), while silver fir showed markedly lower survival (20.4%). Initial vitality emerged as the primary determinant of survival, whereas the influence of morphological traits was species-specific. Longitudinal analyses revealed contrasting vitality trajectories among species. Norway spruce exhibited a gradual decline consistent with cumulative stress effects, silver fir showed a strongly non-linear, threshold-like decline, and European beech demonstrated improving vitality over time, indicating progressive acclimation to local conditions. Structural traits such as crown development and root collar diameter were important predictors in Norway spruce, growth performance was dominant predictor in silver fir, and crown-related traits were most important in European beech. Models based on truncated trajectories improved model fit while maintaining consistent results, supporting the robustness of these patterns. The results indicate that early establishment acts as a critical filtering stage and suggest that differences in initial wildling quality, phenological status at planting, and biotic stress may contribute to variation in survival among species. In particular, the low survival of silver fir may partly reflect phenological differences associated with elevational transfer. These findings suggest that successful application of wildlings in assisted range expansion and climate-adaptive forest management requires not only appropriate species selection but also careful consideration of seedling quality, planting phenology, and microsite conditions.