The bachelor work is focussing on a research of thick, high and spatial diversity of natural populations of alder grey (Alnus incana (L.) MOENCH.) in an area of Laborec´s highlands with a help of indexes structure´s undergrowth. The research is running on four research´s areas, which are founded in different parts of explored orthographic whole, in localities of natural occurrence of alder grey. The work consists of three parts. In the first theoretical part, the morphological and general characteristic of genus Alnus and an issue of indexes of the undergrowth´s structure is in detail processed. The second part is aiming on the characteristic of investigated area and the third part of the work is consisting from a methodics and a processing of preliminary results of work.