This study is focused on the evaluation of the values of the diversity indices of semi-natural dry calcareous grasslands of the Festuco-Brometea class in the area of Devínska Kobyla National Nature Reserve 50 years after abandonment of traditional management (grazing and mowing). The values of the species richness, the Shannon–Wiener index of diversity, the Simpson index, and Pielou’s measure of species evenness in the communities in the old and recent data, and the values of the environmental variables based on the Ellenberg indicator values of species were analyzed. For most of these analyses, we used Kruskal–Wallis in R 3.5.1. Compared to the past, we have recorded a significant lower values of the species richness, biodiversity, and species evenness in some communities. In some communities, no significant changes were recorded. Only in one community—Poo badensis-Festucetum pallentis, the higher values of Shannon–Wiener index was recorded compared to the past. The analysis of the Ellenberg indicator values revealed a statistically significant higher Ellenberg indicator values for moisture and nutrients and lower values for light in more recent period compared to the old period. The recorded results could be caused by the changes in the management after the year 1965, after abandonment of grazing and the gradual overgrowing by woody species took place in the area. The frequency of occurrence of some woody species (e.g., Populus alba, P. nigra, and Robinia pseudoacacia) in some communities increased compared to the past.
