The herbicide imazapic is registered for use on rangelands and provides effective short-term control of certain invasive annual grasses. However, details about optimal application rates for downy brome and susceptibility of simultaneously seeded species are lacking. Thus, we investigated downy brome and seeded species responses to variable rates of imazapic (0, 35, 70, 105, and 140 g ai/ha) in two plant communities (salt desert shrub and Wyoming big sagebrush). In autumn 2003, plots were treated with imazapic and seeded with one of five perennial plant materials (Siberian wheatgrass [‘Vavilov’ and the experimental source Kazak]; prostrate kochia [‘Immigrant’ and the experimental source 6X], and Russian wildrye [‘Bozoisky II’]). Downy brome cover and seeded species establishment were evaluated in spring 2004 and 2006. Downy brome cover in 2004 decreased with increasing imazapic rate at both sites, although more so at the Wyoming big sagebrush site. In 2006, no difference in downy brome cover existed among herbicide rates at the Wyoming big sagebrush site. At the salt desert shrub site, the high rate of imazapic reduced downy brome cover by about 25% compared to untreated plots. ‘Vavilov’ Siberian wheatgrass was the only seeded species with lower downy brome cover in 2006 than 2004. Seeded species establishment increased with imazapic rate in the salt desert shrub community, but in the Wyoming big sagebrush community it peaked at intermediate rates and declined at higher rates. Variation in downy brome control and seeded species establishment might have been associated with differences in precipitation, soil organic matter, and disturbance history between sites. Overall, imazapic was useful for helping establish desirable perennial species, but unless downy brome is reduced below a critical threshold, favorable precipitation can return sites to pretreatment levels within two years.
The choice of plant materials is an important component of revegetation following disturbance. To determine the utility and effectiveness of various perennial grass species for revegetation on varied landscapes, a meta analysis was used to evaluate the stand establishment and persistence of 18 perennial cool-season grass species in 34 field studies in the Intermountain and Great Plains regions of the United States under monoculture conditions. Combined across the 34 studies, stand establishment values ranged from 79% to 43% and stand persistence values ranged from 70% to 0%. Intermediate wheatgrass (Thinopyrum intermedium [Host] Barkworth & D. R. Dewey), tall wheatgrass (Thinopyrum ponticum [Podp.] Z.-W. Liu & R.-C. Wang), crested wheatgrass (Agropyron spp.), Siberian wheatgrass (Agropyron fragile [Roth] P. Candargy), and meadow brome (Bromus riparius Rehmann) possessed the highest stand establishment (! 69%). There were no significant differences among the 12 species with the largest stand persistence values. Basin wildrye (Leymus cinereus (Scribn. & Merr.)Á. Löve), Altai wildrye (Leymus angustus [Trin.] Pilg.), slender wheatgrass (Elymus trachycaulus [Link] Gould ex Shinners), squirreltail (Elymus spp.), and Indian ricegrass (Achnatherum hymenoides [Roem. & Schult.] Barkworth) possessed lower stand persistence ( 32%) than the majority of the other species, and Indian ricegrass (0%) possessed the lowest stand persistence of any of the species.Correlations between environmental conditions and stand establishment and persistence showed mean annual study precipitation to have the most consistent, although moderate effect (r¼~0.40) for establishment and persistence. This relationship was shown by the relatively poor stand establishment and persistence of most species at sites receiving less than 310 mm of annual precipitation. These results will be a tool for land managers to make decisions concerning the importance of stand establishment, stand persistence, and annual precipitation for revegetation projects on disturbed sites.
The objective of the Conservation Reserve Program (CRP) is to convert erodible cropland to perennial vegetation. Under severe drought, CRP land is frequently utilized for grazing; thus, there is a need to better understand trends in forage nutritional quality in species used in CRP plantings. This study evaluated 13 cool-season irrigated and dryland grasses from May to August and regrowth from September to November in northern Utah during 2004 and 2005 for crude protein (CP), neutral detergent fiber digestibility (NDFD), in vitro true digestibility (IVTD), and neutral detergent fiber (NDF) values. Species, sampling date, year, and sampling date × species interaction had a significant (P < 0.05) effect on CP, NDFD, IVTD, and NDF values. From May to August, there was a strong linear decline in CP, NDFD, and IVTD values. Mean CP values ranged from 68 to 251 g kg −1 in all species examined. Orchardgrass, smooth bromegrass, RS-hybrid, and crested wheatgrass had CP, NDFD, and IVTD values similar to orchardgrass and timothy, but less than perennial ryegrass. Crested wheatgrass had NDF values similar to timothy, but less than orchardgrass. Crested wheatgrass and smooth bromegrass had the greatest nutritional quality and were often similar to orchardgrass, tall fescue, and timothy. Résumé : Le Conservation Reserve Program (CRP) a pour but de transformer des terres arables sujettes à l'érosion en plantations persistantes. Quand survient une grave sécheresse, on recourt souvent aux terres du CRP pour la paissance. Par conséquent, il est important de mieux connaître la qualité nutritive du fourrage en regard des espèces plantées sur les terres du CRP, et les tendances qui s'y rapportent. Les auteurs ont évalué 13 graminées de saison fraîche et de terrain aride entre le mois de mai et le mois d'août, ainsi que leur repousse de septembre à novembre dans le nord de l'Utah, en 2004 et 2005, en vue d'en établir la concentration de protéines brutes (PB), la digestibilité des fibres au détergent neutre (DFDN), la digestibilité in vitro véritable (DIVV) et la teneur en fibres au détergent neutre (FDN). L'espèce, la date de l'échantillonnage, l'année et l'interaction entre la date d'échantillonnage et l'espèce ont une incidence significative (P < 0,05) sur les PB, la DFDN, la DIVV et la concentration de FDN. De mai à août, on remarque une forte baisse linéaire des valeurs PB, DFDN et DIVV. En moyenne, la concentration de PB varie de 68 à 251 g par kg, pour toutes les espèces examinées. Le dactyle pelotonné, le brome inerme, l'agropyre rhizomateux gazonnant hybride et l'agropyre à crête avaient des valeurs similaires à celles du dactyle pelotonné et de la fléole pour les PB, la DFDN et la DIVV, mais ces valeurs étaient inférieures à celles de l'ivraie vivace. La teneur en FDN de l'agropyre à crête est similaire à celle de la fléole. Toutefois, elle était plus faible que celle du dactyle pelotonné. L'agropyre à crête et le brome inerme sont les graminées les plus nourrissantes, et leur qualité équivaut souvent à celle du dactyle peloto...
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