Forest ecosystems face challenges of climate change and the pressure of economic activity on biodiversity. As European policies turn into Green Deal, ecological forestry systems, which aim to increase or at least not reduce biodiversity while maintaining high forest productivity, are becoming particularly relevant. This study examines distribution regularities of the lower storeys of main tree species in fertile not wet habitats of forest communities composed of pioneer deciduous tree species, the understanding of which will allow the development of forestry systems that exploit the natural forest regeneration potential. We used stand-wise forest inventory data on Betula spp., Populus tremula, Alnus incana mature and overmatured stands. We analysed how lower storeys are distributed in the stands of different tree species according to soil conditions, the age, stocking level and mixture. We found that most of stands are not in the second story and understory, from which new stands can be formed. Betula forests have the greatest potential for regeneration, and Alnus incana forests have the lowest one. The most important species of the second story and understory is Picea abies, rarer Fraxinus excelsior and Tilia cordata, other species are more random. With an increasing forest mixture, the second story and understory are found more often. To reduce clear- cutting in the fertile forests of pioneer tree species in forestry, we need to focus on measures to allow the development of lower storeys of the major climax tree species.

Keywords: ecological forestry, forest succession, fertile forest site type, pioneer tree stands, temperate hemiboreal forests