EFFECT OF PROTECTION ON PLANT COMMUNITY DYNAMICS IN THE MEDITERRANEAN ARID ZONE OF SOUTHERN TUNISIA: A CASE STUDY FROM BOU HEDMA NATIONAL PARK

Ecosystems protected from heavy grazing impacts, such as national parks and refuges, are generally considered to sustain higher plant species diversity and better ecosystem composition and structure compared to heavily grazed areas. To evaluate the impact of livestock grazing, we sampled vegetation characteristics from two areas having different grazing intensity levels. The first site has high protection from grazing and is located inside the Bou Hedma National Park in Southern Tunisia. The second site has a low protection from grazing and is situated within an open area located immediately outside the park boundary where human populations and their livestock have unrestricted access to ecosystem resources. Total plant cover, density, perennial species cover and their contribution were compared between the two grazing level sites. Results show that considerable positive effects occur in the areas protected from grazing. As compared to the overgrazed (open) sites. Several species known for their high palatability, such as Cenchrus ciliaris L., Salvia aegyptiaca L., Echiochilon fruticosum Desf. and Helianthemum sessiliflorum Desf., are more abundant inside the park than outside. These results are very important for managers to apply this technique as a tool for increasing the resilience of arid ecosystems, qualified very vulnerable to climate change. Copyright (c) 2011 John Wiley & Sons, Ltd.