Effects of Intermediate-Term Grazing Rest on the Vegetation Characteristics of Steppe Rangelands

The effects of grazing rest on rangelands are different in different climates and knowledge of these effects is necessary to apply correct management. For this purpose, this study was carried out on the percent vegetation cover (PVC) and forage production (FP) of range species at the Nir Range Research Station in Yazd province as a model of steppe rangelands of Iran. In the study area, different grazing intensities were applied until the end of the grazing season of 2006 and from then on, the whole area was under exclusion. PVC and FP were measured in each of the experimental plots once in May 2007 and again seven years later in May 2014. The results of vegetation data analysis in 2007 showed that the heavy grazing intensity applied in the past caused the reduced PVC and FP of two desirable species i.e. Salsola rigida and Stipa barbata as well as increased PVC and FP of Launaea acanthodes and increased forage production of Scariola orientalis as undesirable species. The results of vegetation data analysis in 2014 showed that the lowest PVC and FP of S.rigida was recorded in the experimental plots under heavy grazing intensity. In other experimental plots, there was no significant difference in PVC and FP of this species (p>0.05). There was no significant difference between PVC and FP of other species and total species in different experimental plots (p>0.05). Thus, during the 7-year rest period, although the negative effect of grazing on S.barbata is resolved, it remains on S.rigida and the resulting degradation is not completely compensated during this period and needs more time. Therefore, S.barbata showed better resistance to grazing as compared with S.rigida. According to the results, if steppe rangelands are grazed heavily in the short-term, intermediate-term grazing rest could improve the vegetation to the previous state.