Interaction of Management and Spontaneous Succession Suppresses the Impact of Harmful Native Dominant Species in a 20-Year-Long Experiment

Our study focused on the compositional changes of Pannonian semi-natural dry grasslands. The preservation of these valuable habitats requires regular management. Our mowing experiment aimed to study the suppression of the native dominant Calamagrostis epigejos L. Roth in mid-successional grasslands. Mowing was applied twice a year in eight permanent plots. The vegetation was sampled annually from 2001 to 2021. The impacts of mowing were tested using repeated–measures analysis of variance (ANOVA). After 10 years, the cover of C. epigejos in the mown plots decreased significantly, from an initial average cover of 56.6 to 5.6%. In 20 years, it declined to 1.3%. Surprisingly, in the control plots, it decreased also from 63.7 to 6.9%. Species richness was affected by mowing: significant differences between mown and control plots were detected from the eighth year of our experiment. However, species richness steadily increased in both treatment types from 15 to 36 in the mown plots and 18 to 25 in the control plots, indicating a combined effect of vegetation succession and treatment. Our results suggest that long-term in situ experiments and comprehensive botanical studies are necessary to provide a basis for multi-objective management and reliable utilization of grasslands.