Tim L. Springer

Competition and facilitation between a native and a domestic herbivore: trade-offs between forage quantity and quality

Potential competition between native and domestic herbivores is a major consideration influencing the management and conservation of native herbivores in rangeland ecosystems. In grasslands of the North American Great Plains, black-tailed prairie dogs (Cynomys ludovicianus) are widely viewed as competitors with cattle but are also important for biodiversity conservation due to their role in creating habitat for other native species. We examined spatiotemporal variation in prairie dog effects on growing-season forage quality and quantity using measurements from three colony complexes in Colorado and South Dakota and from a previous study of a fourth complex in Montana. At two complexes experiencing below-average precipitation, forage availability both on and off colonies was so low (12-54 g/m2) that daily forage intake rates of cattle were likely constrained by instantaneous intake rates and daily foraging time. Under these dry conditions, prairie dogs (1) substantially reduced forage availability, thus further limiting cattle daily intake rates, and (2) had either no or a small positive effect on forage digestibility. Under such conditions, prairie dogs are likely to compete with cattle in direct proportion to their abundance. For two complexes experiencing above-average precipitation, forage quantity on and off colonies (77-208 g/m2) was sufficient for daily forage intake of cattle to be limited by digestion rather than instantaneous forage intake. At one complex where prairie dogs enhanced forage digestibility and [N] while having no effect on forage quantity, prairie dogs are predicted to facilitate cattle mass gains regardless of prairie dog abundance. At the second complex where prairie dogs enhanced digestibility and [N] but reduced forage quantity, effects on cattle can vary from competition to facilitation depending on prairie dog abundance. Our findings show that the high spatiotemporal variation in vegetation dynamics characteristic of semiarid grasslands is paralleled by variability in the magnitude of competition between native and domestic grazers. Competitive interactions evident during dry periods may be partially or wholly offset by facilitation during periods when forage digestibility is enhanced and forage quantity does not limit the daily intake rate of cattle.

Chemical Control of Sand Sagebrush: Implications for Lesser Prairie-Chicken Habitat

Abstract Traditional management of sand sagebrush (Artemisia filifolia) rangelands has emphasized sagebrush control to increase forage for livestock. Since the 1950s shrub removal has been primarily achieved with herbicides. Concerns over declining lesser prairie-chicken (Tympanuchus pallidicinctus; LPC) populations have led to increased scrutiny over the use of herbicides to control shrubs. The objective of our research was to describe changes to LPC habitat qualities following chemical control of sand sagebrush in northwest Oklahoma. Study pastures ranged in size from 10 to 21 ha. Five pastures were sprayed with 2,4-dichlorophenoxyacetic acid (2,4-D) in 2003 (RECENT), five were sprayed with 2,4-D in 1984 (OLD), and four received no treatment (SAGE). We measured habitat structure (sagebrush cover, sagebrush density, visual obstruction [VO], and basal grass cover), and dietary resources (forb density, forb richness, and grasshopper density) in all pastures from 2003 to 2006. OLD and RECENT pastures had less sagebrush (cover and density) and VO than SAGE pastures. OLD pastures produced more annual forbs than either SAGE or RECENT pastures. SAGE pastures had more perennial forbs than RECENT pastures. Herbicide application reduced protective cover while providing no increase in forb abundance in RECENT pastures. Our results indicated that it may take several years to realize increases in annual forbs following application of 2,4-D. However, loss of protective cover may persist for multiple years (20+ yr), and removal of sagebrush did not increase forb richness or grasshopper abundance. Thus, 2,4-D may have limited use as a habitat management tool because it takes numerous years to reap the benefit of increased forb abundance while reducing habitat structure in the long term. Resumen El manejo tradicional de pastizales de artemisa (Artemisia filifolia) ha enfatizado el control de artemisa para aumentar el forraje para el ganado. Desde los 1950s la remoción de arbustivas ha sido lograda principalmente con herbicidas. La preocupación por la disminución de las poblaciones de gallinas de pradera (Tympanuchus pallidicinctus; LPC) ha llevado a aumentar la vigilancia sobre el uso de herbicidas para el control de arbustivas. El objetivo de nuestra investigación fue describir los cambios en la calidad del hábitat de LPC después de controles químicos de Artemisia filifolia en el noroeste de Oklahoma. Los potreros en estudio variaron en tamaño de 10 a 21 ha. Cinco potreros fueron asperjados con 2,4-acido diclorofenoxiacético (2,4-D) en 2003 (RECIENTE), otros cinco fueron asperjados con 2,4-D en 1984 (VIEJO) y cuatro no recibieron tratamiento (ARTEMISA). Medimos la estructura del hábitat (cobertura y densidad de artemisa, obstrucción visual [OV] y cobertura basal de pastos) y fuentes de dieta (densidad y riqueza de hierbas y densidad de chapulines) en todos los potreros de 2003 a 2006. Potreros VIEJO Y RECIENTE tuvieron menos artemisa (cobertura y densidad) y OV que los potreros ARTEMISA. Los porteros VIEJO produjeron más hierbas anuales los porteros ARTEMISA Y RECIENTE. Los potreros ARTEMISA tuvieron más hierbas perennes que los potreros RECIENTE. La aplicación de herbicida reduce la cubierta protectora mientras que no aumenta la abundancia de hierbas en los potreros RECIENTE. Nuestros resultados indican que puede tomar varios años el lograr incrementar las hierbas anuales después de la aplicación de 2,4-D. Sin embargo, la pérdida de cubierta protectora podrá mantenerse por múltiples años (20+ años) y el remover la artemisa no aumenta la riqueza de hierbas y abundancia de chapulines. Entonces, 2,4-D podrá tener uso limitado como herramienta de manejo de hábitat porque toma muchos años obtener el beneficio de aumentar la abundancia de hierbas mientras que se reduce la estructura del hábitat en el largo plazo.

Effects of sand sagebrush control in southern mixed-grass prairie rangeland on cattle performance and economic return1

ABSTRACT To evaluate the effects of sand sagebrush (Artemisia filifolia Torr.) control in native rangelands on cattle performance, 15 pastures (10 to 21 ha each) were selected in northwest Oklahoma. Eleven pastures had been sprayed with 2,4-dichlorophenoxyacetic acid in 1984 or 2003 to establish differences in sagebrush cover. The pastures were categorized into 3 sagebrush cover levels: 1) high (27 ± 2.7% cover, n = 4), 2) medium (10 ± 2.7% cover, n = 6), and 3) low (5 ± 2.7% cover, n = 5). From 2003 to 2008, steers (BW = 202 ± 6.1 kg) were stocked annually in late January and grazed until mid-August. The high, medium, and low pastures were stocked at 47, 69, and 69 animal-unit-d/ha, respectively. Cattle were supplemented with oilseed-based cubes (41% CP) from January through April at a rate of 0.68 kg/ steer daily. From January to April, ADG did not differ (P = 0.96) among treatments, but from April to August steers grazing the high pastures gained BW faster (P

Preference of Pen-Reared Northern Bobwhite Among Native Plant Seeds of the Sand Sagebrush-Mixed Prairie

Abstract Adult northern bobwhites (Colinus virginianus) are largely granivorous, primarily eating seeds produced from grasses and forbs. Our objective was to determine northern bobwhite preference among seeds of 45 plant species associated with sand sagebrush (Artemisia filifolia)–mixed prairie. A preference existed among the 45 plant species by weight of seed consumed and percentage of seed in diet (P ≤ 0.05) and on the basis of a cluster analysis of these variables. Five species were categorized into most preferred for food. These included, in order of preference: switchgrass (Panicum virgatum), Rocky Mountain bee plant (Peritoma serrulata), annual sunflower (Helianthus annuus), sand lovegrass (Eragrostis trichodes), and false sunflower (Heliopsis helianthoides). Thirteen plants were categorized into intermediately preferred for food, and 27 species were categorized into least preferred for food. The sand sagebrush–mixed prairie community supports a broad range of plants and animals. Improving rangeland conditions by employing conservative grazing management, especially during drought, or by planting a greater variety of native grasses, sunflowers, shrubs, forbs, and legumes, when reestablishing marginal crop lands, would improve the habitat and diet quality for northern bobwhite and other wildlife species.

Apparent Seed Digestibility and Germination of Seeds After Passage Through the Digestive System of Northern Bobwhite (Colinus virginianus)

Abstract Limited information is available regarding the digestibility or germination of seeds after passage through the digestive system of northern bobwhites (Colinus virginianus), especially of plants associated with the sand sagebrush (Artemisia filifolia)–mixed prairie community. Thus, our objectives were to determine the apparent digestibility of seeds of 45 plant species associated with the sand sagebrush–mixed prairie community and the germination of seeds before and after passage through the digestion system of bobwhites. Seeds of 12 of 45 species fed to bobwhites were found to pass through the digestive system intact. The apparent seed digestion pattern of the 12 plant species with incomplete digestion of seeds was legumes > forbs > grasses > shrubs. At the end of a 7-d germination period, the digestion of seeds by bobwhites reduced seed germination of alkali sacaton (Sporobolus airoides), black-eyed Susan (Rudbeckia hirta), and western yarrow (Achillea millefolium var. occidentalis) but increased the germination of white prairie clover (Dalea candida) seeds (P ≤ 0.05). However, the germination percentage of predigestion seeds of white prairie clover exceeded that of postdigestion seeds (P < 0.05) by the end of a 21-d germination period. Averaged across species, the 21-d seed germination of postdigestion seeds was lower than predigestion seeds (P < 0.05). Viable seeds found in feces are disseminated by quail onto the landscape. Plant species that have been lost from overgrazing or the application of herbicides might be reintroduced onto landscapes through dissemination by bobwhites via food plots, feeding stations, or both if the seeds are deposited onto a suitable germination substrate with suitable seed germination conditions.