The effect of Rangifer tarandus grazing on species composition in plant communities

The fact that large herbivores, such as Rangifer tarandus, play a part in shaping its environment through grazing and trampling of the ground is widely acknowledged today, as well as that these factors have the potential of affecting regional patterns and even global climate. This study investigated whether a considerable increase in grazing by R. tarandus for 25 years resulted in any measurable effects on the diversity of plant species in tundra vegetation. We evaluated if any differences in species composition could be found, based on differences in grazing pressure and productivity of the soil. The effect of difference in grazing pressure was studied through analysis of vegetation at 30 sites, each site comparing two different classes of grazing pressure separated by a fence, and pellets from R. tarandus were counted along transects. We did not find any evidence that the difference in grazing pressure affected the species composition on either side of the fence, depending on the site. The lack of difference in plant species composition may be explained by insufficient differences in abundance of R. tarandus, insufficient time passed since the change in grazing pressure, or varying grazing seasons at the sites on either side of the fence