Journal of Rangeland

This study was conducted to investigate the effects of livestock grazing and the invasion of Stachys byzantina as an increaser species on species composition, functional groups and species richness and diversity. The vegetation data were collected from critical area, key area and invaded grassland by S. byzantine in northern slopes of Alborz mountain range.  Results showed that the plant richness in these sites varies in some extent and 55 species were identified in critical areas, 85 in key areas and 67 in the invaded areas. Multivariate analysis showed that species composition in critical and invaded areas were different from that in the key areas. Palatable species such as Dactylis glomerata, Trifolium repens and Sanguisorba minor were more frequent in the invaded sites. The perennial species functional groups had ssignificantly lower cover percentage in critical areas ( p ˂ 0.05) compared to other sites.  Results indicated that forbs functional groups were more frequent in the invaded areas. Grass species were more frequent in the key areas. Although Simpson diversity index was higher in the invaded sites compared to other sites, there was no significant difference between the species richness of the studied sites. The infested grassland by S. byzanthina can be effectively restored as there are many palatable species in vegetation composition.