• Impact of cultivation legacies on rehabilitation seedings and native species re-establishment in great basin shrublands

      Morris, L. R.; Monaco, T. A.; Sheley, R. L. (Society for Range Management, 2014-05)
      Little is known about how cultivation legacies affect the outcome of rehabilitation seedings in the Great Basin, even though both frequently co-occur on the same lands. Similarly, there is little known about how these legacies affect native species re-establishment into these seedings. We examined these legacy effects by comparing areas historically cultivated and seeded to adjacent areas that were seeded but never cultivated, for density of seeded crested wheatgrass (Agropyron cristatum [L.] Gaertn.) and native perennial grasses, vegetation cover, and ground cover. At half of the sites, historically cultivated areas had lower crested wheatgrass density (P<0.05), and only one site had a higher density of crested wheatgrass (P<0.05). Likewise, the native shrub Wyoming big sagebrush (Artemisia tridentata Nutt. subsp. wyomingensis Beetle & Young) had lower cover (P<0.05) in historically cultivated areas at half the sites. Sandberg bluegrass (Poa secunda J. Presl.) density was consistently lower in historically cultivated areas relative to those seeded-only. At sites where black greasewood (Sarcobatus vermiculatus [Hook.] Torr.) and bottlebrush squirreltail (Elymus elymoides [Raf.] Swezey) were encountered, there was either no difference or a higher density and cover within historically cultivated areas (P<0.05). Likewise, cover of exotic forbs, especially halogeton (Halogeton glomeratus [M. Bieb.] C. A. Mey.), was either not different or higher in historically cultivated areas (P<0.05). Bare ground was greater in historically cultivated areas at three sites (P<0.05). These results suggest that cultivation legacies can affect seeding success and re-establishment of native vegetation, and therefore should not be overlooked when selecting research sites or planning land treatments that include seeding and or management to achieve greater native species diversity.
    • Large-scale downy brome treatments alter plant-soil relationships and promote perennial grasses in salt desert shrublands

      Hirsch-Schantz, M. C.; Monaco, T. A.; Call, C. A.; Sheley, R. L. (Society for Range Management, 2014-05)
      Because invasive annual grasses can strongly influence soil resource availability and disturbance regimes to favor their own persistence, there is a great need to understand the interrelationships among invasive plant abundance, resource availability, and desirable species prominence. These interrelationships were studied in two salt desert sites where the local abundance of downy brome (Bromus tectorum L.) varied spatially and increased more than 12-fold over a 3-yr period. We measured downy brome percentage cover, resource availability, and soil chemical and physical properties within 112 plots per site and found significant negative associations between downy brome abundance and both soil water content (P&lt;0.05; r=-0.27 to -0.49) and nitrate accumulation (P&lt;0.05; r=-0.34 to -0.45), which corroborated with the direction and strength of multivariate factor loadings assessed with principal component analysis. We then applied factorial combinations of prescribed burning and preemergence herbicide at management-relevant scales (i.e., 6 to 46 ha) as well as biomass removal to smaller plots (12.25 m2) at both sites to determine their impact on downy brome, soil resources, and resident plant species. Burning and herbicide applications, especially when combined, significantly reduced downy brome cover (P=0.069 to 0.015), which in turn increased soil nitrate accumulation and water content in the spring. Furthermore, for one shrubland site that was seeded 6 yr previously, the combination of burning and herbicide treatments significantly increased perennial grass percentage cover in the 2 yr posttreatment (P&lt;0.05). Results not only demonstrate the strong relationships between downy brome abundance, soil resources, and residence species for impoverished salt desert shrub ecosystems, but also suggest that restoration and management efforts must include tactics that facilitate resource use by the residual plant community or establish a greater abundance of species capable of high resource acquisition in the spring.