The aim of this study was to determine the optimum size for range management units in the Margha River Basin, Izeh regin. To achieve this propose, all effecting parameters on the size of range management units were determined using AHP method and by considering main range management plans in the region. Geographical information system was used to prepare different maps including slope, aspect and elevation maps. Also, In this research different ecological and socioeconomic aspects were considered. The ecological effects were investigated using all information obtained from different range management plans. Consumer costs were calculated using of questionnaire and also through information obtained from Statistical Center of Iran. Dependency to rangelands was determined using defining relative poverty line, agriculture and other sources of income. Results showed that these rangelands were in average condition and downward trend. In part 1 (without income and cost of agriculture and others): flock sheep optimum size for pure flock sheep, pure flock goat, and mixed flock were, 146, 186, and 168 animal units, respectively. Also, in part 2 (with all income and cost of animals, agriculture and others) results showed that flock sheep optimum size for pure flock sheep, pure flock goat, and mixed flock were, 140, 178, and 159 animal units, respectively. Comparison between range management plans and these results showed that the optimum size of flock animal and that of rangeland and the number of rancher were higher than the rangeland forage production and capacity. Also, in range management plans, the average size of rangeland units and also the average number of rancher were least of optimum size. Key word: Optimum size of utilization units, relative poverty line, sustainable utilization, Margha region, Khuzestan province.
