Colonization and expansion of grassland species after abandonment of dirt roads in the Mongolian steppe

Off-road vehicles cause long-lasting damage to soils and vegetation, especially under extreme conditions such as those in arid regions. Most research on natural vegetation recovery after dirt-road abandonment has only investigated vegetation in the tracks and not that adjacent to the tracks. We investigated plant expansion into adjacent grassland after its colonization of abandoned tracks in the Mongolian steppe. We surveyed the vegetation around two roads: one abandoned for >4 years and another still in use near the abandoned road. Aboveground biomass and ground cover of each species in and beside the tracks were measured. The dirt roads had sustained relatively low vehicle traffic, so the disturbance of grassland productivity was limited. Vegetation cover and aboveground biomass had almost recovered 4 years after road abandonment. However, a low-palatability clonal herb, Artemisia adamsii, increased in abundance by producing many shoots in and around the abandoned tracks, thereby decreasing the quality of pasture. Our results show that vegetation recovery in tracks of the abandoned road can affect surrounding vegetation through the colonization and expansion of clonal species. Thus, to evaluate natural vegetation recovery after dirt-road abandonment, changes in vegetation not only within but also around abandoned tracks should be investigated.