Roadside flora in arid and semi-arid natural areas (Case study: Northern Khorasan province, Iran)

Roads have an important role in plants dispersal on different scales. Various plant species settle on roadsides, but some of them can enter the natural environments and threaten their biodiversity. Worldwide knowledge of roadside flora is necessary for local and global management of natural areas. Accordingly, the roadside flora of Northern Khorasan rangelands was studied along the 600 km of 12 paved roads. Base on a stratified random sampling design, 38 sites were sampled by 100 m² rectangular quadrats stablished on both roadsides. Totally, 330 plant taxa of 39 spermatophyte families were identified and their life-forms and chorology were determined through botanical resources. The results showed that therophytes and hemicryptothytes were the dominant life-forms of roadside vegetation. The native Irano-Turanian elements were the dominant chorotype of roadside habitats. Number of endemic taxa (3.6%) was notable in comparison with cosmopolitan (1.2%) and alien (0.6%) species. Agropyron desertorum (Fisch. ex Link) Schult. and Agropyron elongatum (Host) P. Beauv. were the only two introduced alien species in the studied roadsides. Some of the cosmopolitan and pluriregional species such as Triticum aestivum L. were cultivated plants, but most of them were common weeds. Native weeds like Hordeum glaucum Steud. and Alhagi persarum Boiss. & Buhse had the highest frequency on the studied roadsides. The present study, therefore, revealed that the roadside flora in natural areas could have a considerable stock of native and endemic species which would be suitable for the revegetation of roadsides and the disturbed natural areas around the roads.