The thesis is the continuation of the bachelor thesis and extends the research of the structural diversity of the natural populations of the grey alder (Alnus incana [L.] MOENCH.) in the area of „Spiš-šariš“ middle mountains with new areas. This is done by using structural indexes that determine the spatial and density occurrence of the individuals in the area. The research areas were created in Vyšný Slavkov, Vlčie, Livov, Livovská huta, Komárková chata, Lukov and Terňa. The thesis is divided into the theoretical part and into the results of the research. In the theoretical part, is briefly describes the morphology of the genus Alnus and the characteristics of the studied areas. The second part describes the methodology of data collection for the research and the results themselves. They point to the fact that the gray alder, despite the fact that the area with a wide ecological amlplitude and geographical distribution, creates as a sunny tree at all habitats where the thickness and the height are slightly differentiated, mostly homogeneous stands with high levels of level individuals, and the tendency to produce sprouts.