Date of Award:

2015

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Wildland Resources

Advisor/Chair:

Juan Villalba

Abstract

A large portion of the historical steppe and shrub-steppe habitats in eastern Washington have been altered through biotic and abiotic processes resulting in the annual grass medusahead (Taeniatherum caput-medusae (L.) Nevski) becoming a large component of the altered vegetation. Experiments were conducted to determine whether: 1) protein supplementation would help increase utilization of medusahead by cattle, 2) native and introduced grass cultivars could establish in the region, and 3) mechanical disturbance would aid in establishing Vavilov II Siberian wheatgrass (Agropyron fragile [Roth] P. Candargy) and Immigrant forage kochia (Bassia prostrata [L.] A.J. Scott). Cattle grazing medusahead-infested rangeland for 10-d periods during summer months increased consumption of medusahead due to a reduction in the quality of forage alternatives. Cattle supplemented with a protein concentrate increased consumption of medusahead during d 6 to 10 of the grazing periods resulting in a reduction of medusahead abundance over time. Introduced grass cultivars; Vavilov II, Hycrest IIcrested wheatgrass (Agropyron cristatum [L.] Gaertn.), and Bozoisky II Russian wildrye (Psathyrostachys juncea [Fisch.] Nevski), and a native grass mix; Sherman big bluegrass (Poa secunda J. Presl), Secar Snake River wheatgrass (Elymus wawawaiensis J. Carlson & Barkworth), Bannock Thickspike wheatgrass (Elymus lanceolatus [Scribn. & J.G. Sm.] Gould), and Recovery Western wheatgrass (Pascopyrum smithii [Rydb.] Á. Löve) were planted at three locations. Sherman big bluegrass was the only native species that established with 47 % initial establishment and persistence increasing to 65 % over the course of the study. Hycrest II had 64 % stand establishment but persistence decreased to 48 % and Vavilov II had 57 % initial establishment and decreased to 50 %. Sherman Big bluegrass had greater biomass production in May however, the later maturing Hycrest II and Vavilov II had similar biomass production to Sherman Big bluegrass in July. Bozoisky II had poor stand establishment and decreased over the course of the study. Mechanical disturbance from disking in the fall was successful in establishing Vavilov II and Immigrant forage kochia. In conclusion, cattle can be used to reduce medusahead abundance in rangelands and revegetation with Vavilov II, Hycrest II and Sherman big bluegrass was successful. Mechanical disturbance was successful in aiding in establishment of Vavilov II and Immigrant forage kochia.

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