Grazing by wild red deer maintains characteristic vegetation of semi-natural open habitats: Evidence from a three-year exclusion experiment

Questions Conservation management of semi-natural open habitats today has to compensate for the decline of traditional practices of agricultural land use. Can wild and free-ranging ungulates, such as red deer, contribute to the preservation of characteristic open habitat plant communities? Location Grafenwohr military training area, Germany. Methods We set up a grazing exclusion experiment in grasslands (lowland hay meadows) and heathlands (European dry heaths) and monitored structural vegetation characteristics (sward height, bare soil, biomass contribution ofCalluna vulgaris, litter height, woody species individuals) in open and fenced plots within a three-year study period. We compared plant species richness, diversity and community composition before and after the experimental period. Results In grasslands, plant species diversity was significantly reduced in fenced compared to open plots and in both habitat types, plant community composition responded to the exclusion of red deer. When fences prevented red deer grazing, increasing height of sward and litter in both habitat types as well as reduced cover of bare soil and increasing number of woody plant individuals in heathlands indicated beginning succession. In annually mown grasslands, where the regrowth provides attractive forage for red deer, the differences between open and fenced plots were most pronounced. Conclusions Overall, our results indicate that the conservation value of the studied open habitat types started to decrease after red deer exclusion. Grazing by wild red deer can hence provide benefits to vegetation structure and diversity and could therefore enrich the set of tools available for the conservation management of semi-natural open vegetation types.