Interactive effects of grazing and drought on desert rangelands of Tunisia

Abstract

Arid rangelands worldwide regularly confront drought and overgrazing. Land degradation is mostly apparent in desert rangelands, where drought events are important and grazing influences and intrinsic vegetation change act intermittently. The objectives of this study were to determine the effects of grazing and drought stress on diversity, species richness and primary production in desert rangeland of southern Tunisia. This assessment was conducted in March 2008 (wet year) and March 2009 (dry year) both on grazed and ungrazed sites. Diversity, species richness and biomass production exhibited bigger variation between years than among sites within two years. Although protection from grazing could slightly increase rangeland production in favorable years, the additive effects of heavy grazing and drought could result in restoration failure. This study suggests that climatic variations, particularly droughts, control major trends in plant species composition, diversity and biomass. Under grazing, plants of desert regions are able to respond very rapidly to small drought. The latter is the most debilitating risk in desert areas.