Effects of 2-decade livestock exclusion on vegetation changes in steppic rangelands of Yazd province

Study over vegetation on grazed and ungrazed rangelands is significant for range managemen, this the effects of 2-decade exclusion on vegetation of steppic rangelands in Nir range research station were studied. Three 7.5-hectare experimental plots were selected inside and outside of the exclosure. Exclosure site had not been grazed from 1986 to 2004. The adjacent site was continuously grazed at the same time. Cover estimated on quadrates and forage yield were measured by clipping and weighting method. Data were analyzed by t-test method. Results showed that cover, density and yield of Salsola rigida and Stipa barbata increased significantly inside exclosure (p<0.01), but it was not significantly different in Artemisia sieberi (p>0.05).Cover, density and yield of Scariola orientalis, Launaea acanthodes and Noaea mucronatawere greater in grazed area, but only the yield of first species, density of second species and cover and density of third species were significantly high (p<0.05). Two-decade protection from grazing showed that vegetation trend is very slow in arid rangelands.