Shifts in the altitudinal distribution of alien and native synanthropic plants along roadsides over a 40-year period

Disturbed areas alongside roads shape unique vegetation communities dominated by synanthropic native and alien plant species, facilitated by roads serving as corridors for dispersal, penetration, and integration of synanthropic plants into new areas. We collected presence/absence data for individual species along roads in the Orlické Mountains, Czech Republic, in three time periods during 1970–2010. The distribution of species was mapped using a 1-square-kilometer grid. Analyzing 107 plant species (44 native, 63 alien), we found archaeophyte species favor lower elevations (foothills), while neophytes thrive at higher elevations. Over 40 years, neophyte frequency significantly rose at lower elevations, contrasting the decline at higher elevations, with no marked change in archaeophyte frequency. Native species decline notably at 400–500 m elevations. Some thermophilous native synanthropic species and alien archaeophytes spread from foothills to higher elevations, while some psychrophilic higher-elevation species shift upwards, diminishing at lower elevations. We emphasize human disturbance and global warming as pivotal factors influencing the altitudinal distribution shift in both native and alien plant species.