The effect of stand age on biodiversity in the stands of Populus tremula, a keystone tree species in boreal forests, has been insufficiently studied, although this knowledge is crucial for maintaining biodiversity in managed forests. We studied the assemblages of vascular plants, bryophytes and lichens from a chronosequence of aspen stands (n = 20) with an age from 8 to 131 years, aiming to identify the main patterns in species richness and composition. Altogether, 72 vascular plant species were found in the field layer and 17 species in the shrub layer. The total numbers of bryophyte and lichen species were 92 and 104, respectively. Overall, 2 vascular plant, 12 bryophyte and 9 lichen species were the taxa with a high conservation value. Sixteen lichens were regarded as managementsensitive or focal species based on earlier studies, and 10 vascular plant species were hemeraphobic (severely disturbed by human activities). The effect of stand age on average species richness estimates depended on the studied species groups. Stand age had a negative effect on the average number of vascular plants, field layer species, apophytic vascular plants and epixylic lichens and a positive effect on the number of lichens, the number of epiphytic bryophytes and lichens and on bryophytes and lichens with a high conservation value. The compositional patterns of vascular plants, bryophytes and lichens strongly correlated with stand age. In addition, stand characteristics, soil properties and light conditions influenced the assemblages, although the direct effects were variable for different groups. The largest differences could be observed in vascular plant, bryophyte and lichen communities between young and old stands; for lichens, also mature and old stands differed significantly. Our results indicate that more than 60 years are required for the recovery of some species groups after clearcutting. At the same time, other species groups were either not negatively affected by clear-cutting or showed a higher richness in younger stands. Therefore, we conclude that the management of aspen stands should involve the combination of different management regimes on the landscape scale (variation from short to long rotations in different stands, maintaining retention trees and ceasing of clear-cutting in some stands). Our results also show that as second-storey Tilia cordata played an important role in maintaining biodiversity in the studied stands, this tree species needs to be preserved in forests where lime trees naturally grow as co-dominants. Keywords: European aspen; Vascular plants; Bryophytes; Lichens; Tilia cordata; Clear-cutting.