Clipping and Long-Term Grazing Effects on Biomass and Carbohydrate Reserves of Indian Ricegrass

Abstract

Long-term heavy grazing had little effect on root and crown biomass of Indian ricegrass (Oryzopsis hymenoides [Roem. and Schult.] Ricker), nor did it significantly affect the total nonstructural carbohydrate (TNC) reserve levels or the seasonal cycle of reserves in this grass. Fifty years of protection from livestock use had not resulted in ecotypic differentiation in Indian ricegrass for these variables. Clipping reduced crown biomass more than root biomass and removal of 90% of the aboveground biomass resulted in more than a 50% reduction in crown biomass and reserve carbohydrate pool. Two commercial strains of Indian ricegrass ('Nezpar' and 'Paloma) were compared with native Chaco Canyon strains in a uniform garden study. The Nezpar strain was superior to Paloma and the Chaco Canyon strains in production of crown biomass and TNC reserves at the more mesic garden site. The native strains from the more arid Chaco Canyon site were superior to both cultivated strains in production of roots. The native Chaco Canyon strains were little affected by clipping and have promising genetic potential for tolerance of drought and heavy grazing.