Steppe Communities in the Foothills of the Colorado Front Range and their Relative Productivities

Vegetation species composition and net primary productivity were measured in four steppe communities at the eastern base of the Front Range in 1967. Existing shoot biomass was measured by total harvests in Andropogon gerardii-Poa pratensis, Stipa comataBouteloua gracilis, Stipa robusta-Agropyron smithii, and Stipa neomexicana communities. Early season biomass was greatest in the last community. Total biomass was greatest in the Andropogon and Stipa robusta communities, both of these being early and late season producers. Maximum production averaging 5.2 g/m2-day occurred during a 33-day early summer period in the Stipa robusta community. Midsummer productivity was highest in the Andropogon community where an average of 4.3 g/m2-day was measured from late June to mid-August. These values were generally much higher than rates previously reported in the foothills region and eastern Colorado, perhaps because of the high seasonal rainfall and excellent condition of the four communities.