This study quantifies long-term changes in alpine plant communities of the Western Carpathians by resampling 117 historical relevés from the Western and Low Tatras after a 40–51-year interval. We analyzed species composition within seven vegetation classes spanning an altitudinal range of 1505–2184 m. Species were assigned an elevation econumber to assess vertical shifts at the community level using a cover-weighted elevation score. Relative frequency changes were also calculated for each species. We found a general increase in woody species, tall forbs, and grasses, accompanied by a decline in high-elevation specialists. These frequency changes were significantly correlated with elevation econumbers, confirming an expansion of species associated with lower altitudes. While upward migration signals were detected in six vegetation classes, one showed lower compositional turnover. Despite these differences, both the mean elevation score and species richness increased across all classes. A Generalized Additive Mixed Model identified changes in light availability and moisture as the strongest drivers of these upward shifts. Our findings suggest that current alpine vegetation dynamics are driven by biotic homogenization and the upward migration of competitive species, which is altering the unique character of these ecosystems.
Palaj et al. (Tue,) studied this question.