The harvest method was employed to study primary production in two plant communities, one of which had been continuously grazed for about 70 years while the other had been protected from grazing for a period of 11 years. Exclosures were constructed around both study areas to protect them from livestock grazing during the 2 years of the study. There was 45% more top growth in the protected area but only 68% as much root mass; consequently, average annual net production was at least 12% greater in the grazed area. Irrigation with 9 cm water increased top—growth yield 41.4%. Although over 30 species of plants were present in each community, two species contributed over half of the annual production in both areas. In the protected community 65% and in the grazed community 80% of the plant mass was underground. Proportion of plant mass underground ranged from 55% to over 98% in individual plants excavated whole. Following harvesting of the tops, dry weight of the roots decreased 1.6% during the first week, 22.1% during the first month, and 31.3% during the first 8 months. To measure seasonal trends in productivity, six plots, each 1 m2in area, were harvested every week during two growing seasons. Artemisia tridentata, the principal shrub present, seemed to be most productive during the fall and early spring while Stipa comata, the principal grass, was most productive during late spring and early summer.