Effect of competition by cheatgrass on shoot growth of Idaho fescue.

Abstract

Ability to compete with alien weeds may be one factor enabling high-seral, native bunchgrasses to persist on degraded rangelands. This study examined the effect of competition from cheatgrass (Bromus tectorum L.) on shoot growth of Idaho fescue (Festuca idahoensis. Elmer). Four Idaho fescue collections were obtained from degraded rangelands, while the fifth was from a site in high ecological condition. Plants were established in pots in a greenhouse with 2 watering regimes, and ratios of Idaho fescue:cheatgrass of 1:0, 1:5, and 1:10. Plants were grown for 56 days. Increasing competition from cheatgrass depleted soil moisture and reduced growth of Idaho fescue. However, Idaho fescue produced greater tiller and leaf numbers than cheatgrass. Idaho fescue plants from the pristine population produced 0.57 g aboveground biomass while plants from the degraded sites produced 0.31 g. Aboveground biomass from the pristine population was reduced 35% and 56% at the 1:5 and 1:10 competition levels respectively, compared to the control (1:0 ratio). Aboveground biomass of plants from the degraded populations was similar to the control at the 1:5 level, and was reduced 32% at the 1:10 level. These results indicated that Idaho fescue from the degraded sites exhibits a different response to competition from cheatgrass than Idaho fescue from the pristine site. This information may prove useful in selecting ecotypes of Idaho fescue for range revegetation.