• Abundances of coplanted native bunchgrasses and crested wheatgrass after 13 years

      Nafus, A. M.; Svejcar, T. J.; Ganskopp, D. C.; Davies, K. W. (Society for Range Management, 2015-03)
      Crested wheatgrass (Agropyron cristatum [L] Gaertm) has been seeded on more than 5 million hectares in western North America because it establishes more readily than native bunchgrasses. Currently, there is substantial interest in reestablishing native species in sagebrush steppe, but efforts to reintroduce native grasses into crested wheatgrass stands have been largely unsuccessful, and little is known about the long-term dynamics of crested wheatgrass/native species mixes. We examined the abundance of crested wheatgrass and seven native sagebrush steppe bunchgrasses planted concurrently at equal low densities in nongrazed and unburned plots. Thirteen years post establishment, crested wheatgrass was the dominant bunchgrass, with a 10-fold increase in density. Idaho fescue (Festuca idahoensis Elmer), Thurber's needlegrass (Achnatherum thurberianum (Piper) Barkworth), basin wildrye (Leymus cinereus [Scribn. & Merr.] A. Löve), and Sandberg bluegrass (Poa secunda J. Presl) maintained their low planting density, whereas bluebunch wheatgrass (Pseudoroegneria spicata [Pursh] A. Löve), needle-and-thread (Hesperostipa comata [Trin. & Rupr.] Barkworth), and squirreltail (Elymus elymoides [Raf.] Swezey) densities declined. Our results suggest that densities of native bunchgrasses planted with crested wheatgrass are unlikely to increase and that some species may only persist at low levels. The high recruitment of crested wheatgrass suggests that coplanting of some native bunchgrasses may be a viable way of avoiding crested wheatgrass monocultures when this species is necessary for rehabilitation or restoration. © 2015 Society for Range Management. Published by Elsevier Inc. All rights reserved.
    • Can Imazapic and Seeding Be Applied Simultaneously to Rehabilitate Medusahead-Invaded Rangeland? Single vs. Multiple Entry

      Davies, K. W.; Madsen, M. D.; Nafus, A. M.; Boyd, C. S.; Johnson, D. D. (Society for Range Management, 2014-11)
      It has recently been proposed that the cost of rehabilitating medusahead (Taeniatherum caput-medusae [L.] Nevski)–invaded rangelands may be reduced by concurrently seeding desired vegetation and applying the preemergent herbicide imazapic. However, the efficacy of this “single-entry” approach has been inconsistent, and it has not been compared to the multiple-entry approach where seeding is delayed 1 yr to decrease herbicide damage to nontarget seeded species. We evaluated single- and multiple-entry approaches in medusahead-invaded rangelands in southeastern Oregon with seeding for both approaches occurring in October 2011. Before seeding and applying herbicide, all plots were burned to improve medusahead control with imazapic and prepare the seedbed for drill seeding–introduced perennial bunchgrasses. Both approaches effectively controlled medusahead during the 2 yr postseeding. However, almost no seeded bunchgrasses established with the single-entry treatment (< 0.5 individals · m-2), probably as a result of nontarget herbicide mortality. Perennial grass cover and density in the single-entry treatment did not differ from the untreated control. In contrast, the multiple-entry treatment had on average 6.5 seeded bunchgrasses · m-2 in the second year postseeding. Perennial grass (seeded and nonseed species) cover was eight times greater in the multiple-entry compared to the single-entry treatment by the second year postseeding. These results suggest that the multiple-entry approach has altered the community from annual-dominated to perennial grass–dominated, but the single-entry approach will likely be reinvaded and dominated medusahead without additional treatments because of a lack of perennial vegetation. © 2014 Society for Range Management
    • Success of Seeding Native Compared with Introduced Perennial Vegetation for Revegetating Medusahead-Invaded Sagebrush Rangeland

      Davies, K. W.; Boyd, C. S.; Johnson, D. D.; Nafus, A. M.; Madsen, M. D. (Society for Range Management, 2015-05)
      Millions of hectares of Wyoming big sagebrush (Artemisia tridentata Nutt. subsp. wyomingensis Beetle & Young) rangeland have been invaded by medusahead (Taeniatherum caput-medusae [L.] Nevski), an exotic annual grass that degrades wildlife habitat, reduces forage production, and decreases biodiversity. Revegetation of medusahead-invaded sagebrush plant communities is necessary to restore ecosystem services. Disagreement, however, exists over whether to seed native or introduced perennial species to revegetate communities after controlling medusahead. Though native species generally do not establish as well as introduced species, interference from co-seeded introduced species has often been attributed to the limited success of natives. The potential for seeding natives to revegetate communities after medusahead control is relatively unknown because they have been largely co-seeded with introduced species. We compared the results of seeding native and introduced perennial species after controlling medusahead with prescribed burning followed with an imazapic herbicide application at five sites. Perennial bunchgrass cover and density were 5- and 10-fold greater in areas seeded with introduced compared with native species 3 years post seeding. Furthermore, exotic annual grass cover and density were less in areas seeded with introduced compared with native species. Seeded introduced and native shrubs largely failed to establish. High perennial bunchgrass density (15 individuals · m-2) in areas seeded with introduced species in the third year post seeding suggests that the succession trajectory of these communities has shifted to becoming perennial dominated. Average perennial bunchgrass density of 1.5 individuals · m-2 with seeding native species will likely not limit medusahead and appears to already be converting back to exotic annual grass-dominated communities. These results suggest that seeding introduced compared with native species after medusahead control will likely be more successful. Our results also imply that if natives are selected to seed after medusahead control, additional resources may be necessary to recontrol medusahead and repeatedly sow native species. © 2015, Elsevier Inc. All rights reserved.
    • Vegetation Response to Mowing Dense Mountain Big Sagebrush Stands

      Davies, K. W.; Bates, J. D.; Nafus, A. M. (Society for Range Management, 2012-05-01)
      A decrease in fire frequency and past grazing practices has led to dense mountain big sagebrush (Artemisia tridentata Nutt. subsp. vaseyana [Rydb.] Beetle) stands with reduced herbaceous understories. To reverse this trend, sagebrush-reducing treatments often are applied with the goal of increasing herbaceous vegetation. Mechanical mowing is a sagebrush-reducing treatment that commonly is applied; however, information detailing vegetation responses to mowing treatments generally are lacking. Specifically, information is needed to determine whether projected increases in perennial grasses and forbs are realized and how exotic annual grasses respond to mowing treatments. To answer these questions, we evaluated vegetation responses to mowing treatments in mountain big sagebrush plant communities at eight sites. Mowing was implemented in the fall of 2007 and vegetation characteristics were measured for 3 yr post-treatment. In the first growing season post-treatment, there were few vegetation differences between the mowed treatment and untreated control (P>0.05), other than sagebrush cover being reduced from 28% to 3% with mowing (P<0.001). By the second growing season post-treatment, perennial grass, annual forb, and total herbaceous vegetation were generally greater in the mowed than control treatment (P<0.05). Total herbaceous vegetation production was increased 1.7-fold and 1.5-fold with mowing in the second and third growing seasons, respectively (P<0.001). However, not all plant functional groups increased with mowing. Perennial forbs and exotic annual grasses did not respond to the mowing treatment (P>0.05). These results suggest that the abundance of sagebrush might not be the factor limiting some herbaceous plant functional groups, or they respond slowly to sagebrush-removing disturbances. However, this study suggests that mowing can be used to increase herbaceous vegetation and decrease sagebrush in some mountain big sagebrush plant communities without promoting exotic annual grass invasion./Una disminución en la frecuencia del fuego y anteriores practicas de pastoreo han llevado a la formación de montículos densos de artemisa de la montan ̃a (Artemisia tridentata Nutt. subsp. Vaseyana [Rydb.] Beetle) y la reducción del estrato herbáceo. Para revertir esta tendencia, con frecuencia se aplican tratamientos para reducir la artemisa y aumentar la vegetación herbácea. La remoción mecánica de la artemisa es el tratamiento comúnmente usado, sin embargo, no hay información detallada de la respuesta de la vegetación al chapoleo. Específicamente, se necesita información para determinar sí aumentos proyectados en pastos perennes y hierbas se posibles y como pastos exótico anuales responden al tratamiento de chapoleo. Para responder esta preguntas, evaluamos la respuesta de la vegetación al tratamiento de chapoleo in comunidades de plantas de gran artemisa de montaña en ocho sitios. El chapoleo fue implementado en el otoño de 2007 y las características de la vegetación fueron medida tres años post-tratamiento. En la primera e ́poca de crecimiento de post-tratamiento hubo pocas diferencias en la vegetación entre el tratamiento de chapoleo y el control (P>0.05). La cobertura de artemisa se redujo de 28% a 3% con el chapoleo (P<0.001). Para la segunda época de crecimiento post-tratamiento los pastos perennes, hierbas anuales y el total de la vegetación herbácea fueron generalmente mayores en el tratamiento de chapoleo que en el control (P<0.05). El total de la producción de la vegetación herbácea aumento 1.7 a 1.5 veces con el tratamiento de chapoleo en la segunda y tercer e ́poca decrecimiento respectivamente (P<0.001). Sin embargo, no todos los grupos funcionales de plantas aumentaron con el chapoleo. Las hierbas perennes y pastos exóticos anuales no respondieron al tratamiento de chapoleo (P>0.05). Estos resultados sugieren que la abundancia de artemisa puede no ser el factor limitante de algunos grupos funcionales de plantas herbaceas o que ellas responden lentamente al disturbio de la remoción de la artemisa. Sin embargo, este estudio sugiere que el chapoleo puede ser usado para aumentar la vegetación herbácea y disminuir la artemisa en algunas comunidades de plantas de gran artemisa de montaña sin promover la invasión de pastos anuales exóticos.