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Purple threeawn (Aristida purpurea) is a native perennial grass which causes grazing problems in the Western United States. This species is catalogued as undesirable to cattle production because it is low quality coupled with low palatability forage. Fire is one of the management tools that have been used to control it on infested grasslands. The objective of this study was to determine the response of total nonstructural carbohydrates (TNC) reserves of the purple threeawn plants to defoliations types during three phenological stages. This research was conducted in the Texas Tech University, Native Rangeland, Lubbock, TX. During the 2010 growing season 90 purple threeawn plants were randomly selected based on plant size in vegetative, reproductive and post-reproductive stages. In each phenological stage ten plants were clipped, ten more burned and tenwere used as control. Clipping treatments consisted in simulating 90% utilization while burning consisted of applying fire individually. TNC samples were collected from basal crowns 30 and 45 days after treatment application. TNC concentration determinations were performed in the laboratory. Samples were prepared using the acid hydrolysis process then TNC concentration was measured spectrophotometrically at 612 nm. TNC concentrations of control plants were significantly (P<0.05) different from the reproductive stage to early dormancy; this pattern was characterized by a steady increase across phenological stages. Defoliation treatments affected significantly (P<0.05) the TNC reserves of purple threeawn plants during each phenological stage. TNC reserves of planst treated in vegetative and reproductive stages behaved similarly, with higher concentration at the first collection, decreasing by the second one. On the other hand plants treated in post-reproductive stages showed an increase in TNC concentration from the first to the second collection date. Our results showed that threeawn presents a lower TNC concentration in relation to other grasses, and also seems to still be storing carbohydrates even during early dormant stage in late November.