The tussock grasslands of Festuca humilior (Nees & Meyen) and Calamagrostis vicunarum (Weddell) have a significant extension in the Central Andes and are considered a recognized vegetation association for its ecological-economic value. The objective of this research was to estimate the cumulative impact of the level of use of the key grasses F. humilior and C. vicunarum on height, vigor and weight of the plant. The study was carried out in a humid grassland of regular condition located 4 186 masl in the Puna ecoregion. The variables evaluated were: plant height, basal and canopy diameter and plant weight. The experiment lasted two years during which individual plants of each species were cut every four months. The vigor was estimated from the volume (cm3) and the weight of the plant (gMS/plant) from the regression of the weight and the volume of the plant. Height (cm) was the length ...