Date of Award:

5-1-2015

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Plants, Soils, and Climate

Advisor/Chair:

Earl Creech

Abstract

Gardner saltbush ecosystems are increasingly being invaded by halogeton, a competitive annual weed that increases soil surface salinity and reduces plant biodiversity. This study was established on the Flaming Gorge National Recreation Area, in the Ashley National Forest near Manila, UT to evaluate the ability of forage kochia, Russian wildrye, tall wheatgrass, Indian ricegrass and Gardner saltbush, in monocultures and binary mixtures with Gardner saltbush, to establish and compete in ecosystems dominated by halogeton. A dormant seeding, with and without prior disking, was conducted to determine the ability of plant materials to establish. A spaced-plant evaluation was used to determine the competitive ability of fully established plants by measuring halogeton densities at four 10 cm intervals (10-20, 20-30, 30-40, and 40-50 cm) distal from transplants. Gardner saltbush, tall wheatgrass, and Indian ricegrass did not establish or persist beyond the first year in either study. Conversely, Russian wildrye and forage kochia established and persisted, with Russian wildrye establishment higher (P ≤ 0.05) in the disked treatment (4.5 and 1.7 plants m-2, respectively) and no-till favoring (P ≤ 0.05) forage kochia establishment (2.0 and 0.8 plants m-2, respectively). Spaced-plants of these species reduced halogeton by 52% relative to the control. Furthermore, by the second year of evaluation, the competitive ability of Russian wildrye and forage kochia had extended to 50 cm distal from transplant. Transplant survival and halogeton frequency were highly correlated (r = -0.67, P = 0.0001), indicating the important of persistence. These results suggest that Russian wildrye and forage kochia can establish, persist, and compete with halogeton, thereby providing an opportunity for reclamation of halogeton-invaded areas. Conversely, direct restoration to Gardner saltbush and Indian ricegrass does not appear likely

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