Effects of Harvest Intensity on Production of

With regard to retrogression trend of rangelands in central Zagross، many native plant species are expected to be increasingly on the verge of extinction. Therefore، for proper rangeland management the optimum harvest intensity of important plant species is an essential factor for rehabilitation and recovery of native rangeland species. This research was aimed to study the response of four range species to clipping intensity on yield and regrowth and to determine the appropriate harvesting intensity to increase the stability and survival of four range species. Astragalus caragana، Astragalus cyclophyllon، Astragalus podolobus and Medicago sativa were planted in the college of natural resources greenhouse in Isfahan University of Technology campus، during 2013 growing season. The experiment was conducted in a randomized complete block design with 3 levels: control، 60%، and 80% cuttings of plant stems at harvest times. Production of dry matter and stem heights were measured and evaluated. The results showed significant differences at α=1% among species، harvest intensity and interactions between species and harvest intensities. Based on these results، M. sativa and A. caragana are more tolerant to moderate and heavy grazing than two other species. Consequently، a harvesting intensity of 60% was recommended as the best allowable use of M. sativa and A. caragana. On the other hand، A. cyclophyllon and A. podolobus were more sensitive to harvest intensity. However، A. cyclophyllon and A. podolobus could not tolerate intensive grazing during the first growing season.