: One of the problems of rangelands in Iran is early grazing by rural and tribal community livestocks. Regeneration and sustenance of some of important range species are threatened by improper entering date. Non structural carbohydrate reserves are considered to be very crucial for regrowth and vigor of range plants after defoliation and for beginning of growing period. Bromus tomentellus is one of the important and wide spread species in Iran . This species is palatable therefore is intensively utilized by all species of livestocks specialy in early growth stage. This study was conducted during growing season of year 2005 in Shahid Hamzavi research station Hanna, Semirom, Isfahan province. Non structural carbohydrate reserves change of this species was investigated in two range sites with heavy grazing and proper grazing histories. Phenological stages selected for sampling were: early growth stage (3-4 leaves), Panicle emergence and seed ripening. Shoot (stem base) and root samples were collected from six random plants in phonological stages in each site. According to AOAC, Sheffer-somogy(1940) method, total non structural carbohydrates levels were determined. Results indicated that in seed ripening stage in proper grazing site TNC was 2.23 mg/g and significantly (p 0.01) higher than in heavy grazing site (1.25 mg/g). Roots contained significantly (p 0.01) higher levels of TNC than shoots. TNC levels were lowest in early growth stage and highest in panicle emergence stage. This results emphasized the degrading effects of early grazing and panicle emergence to be the proper time for beginning of grazing period. Key words : Non structural carbohydrate reserves, TNC, TAC, Bromus tomentellus, Phenological stages, Grazing.
