• Growth Regulator Herbicides Prevent Invasive Annual Grass Seed Production Under Field Conditions

      Rinella, Matthew J.; Masters, Robert A.; Bellows, Susan E. (Society for Range Management, 2010-07-01)
      Growth regulator herbicides, such as 2,4-D, dicamba, picloram, and aminopyralid, are commonly used to control broadleaf weeds in rangelands, noncroplands, and cereal crops. If applied to cereals at late growth stages, while the grasses are developing reproductive parts, the herbicides often reduce cereal seed production. We are researching methods for using this injury response to control invasive annual grasses in rangelands by depleting their short-lived seed banks. In a previous greenhouse study, we found picloram and dicamba reduced seed production of the invasive annual grass Japanese brome (Bromus japonicus Thunb.) by nearly 100%. However, this promising greenhouse finding needs to be corroborated in the field before growth regulators can be confidently recommended for invasive annual grass control. This research note describes a study conducted in eastern Montana suggesting growth regulators may provide excellent control of invasive annual grasses. Specifically, we found typical use rates of aminopyralid and picloram reduced Japanese brome seed production by more than 95% (based on sample means) when applied at three different plant growth stages. This promising result contributes to the accumulating body of evidence suggesting growth regulators may control invasive annual grasses. 
    • Hydrologic Response to Mechanical Shredding in a Juniper Woodland

      Cline, Nathan L.; Roundy, Bruce A.; Pierson, Fredrick B.; Kormos, Patrick; Williams, C. Jason (Society for Range Management, 2010-07-01)
      We investigated soil compaction and hydrologic responses from mechanically shredding Utah juniper (Juniperus ostesperma [Torr.] Little) to control fuels in a sagebrush/bunchgrass plant community (Artemisia nova A. Nelson, Artemisia tridentata Nutt. subsp. wyomingensis Beetle Young/Pseudoroegneria spicata [Pursh] A. Löve, Poa secunda J. Presl) on a gravelly loam soil with a 15% slope in the Onaqui Mountains of Utah. Rain simulations were applied on 0.5-m2 runoff plots at 64 mm h-1 (dry run: soil initially dry) and 102 mm h-1 (wet run: soil initially wet). Runoff and sediment were collected from runoff plots placed in five blocks, each containing four microsites (juniper mound, shrub mound, vegetation-free or bare interspace, and grass interspace) with undisturbed or tracked treatments for each microsite type and a residue-covered treatment for grass and bare interspace microsites. Soil penetration resistance was measured at the hill slope scale, and canopy and ground cover were measured at the hill slope and runoff plot scale. Although shredding trees at a density of 453 trees ha-1 reduced perennial foliar cover by 20.5%, shredded tree residue covered 40% of the ground surface and reduced non-foliar-covered bare ground and rock by 17%. Tire tracks from the shredding operation covered 15% of the hill slope and increased penetration resistance. For the wet run, infiltration rates of grass interspaces were significantly decreased (39.8 vs. 66.1 mm h-1) by tire tracks, but infiltration rates on juniper mounds and bare interspaces were unchanged. Bare interspace plots covered with residue had significantly higher infiltration rates (81.9 vs. 26.7 mm h-1) and lower sediment yields (38.6 vs. 313 g m-2) than those without residue. Because hydrologic responses to treatments are site- and scale-dependent, determination of shredding effects on other sites and at hill slope or larger scales will best guide management actions. 
    • Lesser Prairie-Chicken Hen and Brood Habitat Use on Sand Shinnery Oak

      Bell, Luke A.; Fuhlendorf, Samuel D.; Patten, Michael A.; Wolfe, Donald H.; Sherrod, Steve K. (Society for Range Management, 2010-07-01)
      The structural attributes of shrubland communities may provide thermal refugia and protective cover necessary for wild animals to survive. During the summers of 2002 and 2003, we evaluated the thermal environment for lesser prairie-chicken (Tympanuchus pallidicinctus Ridgway) broods in southeast New Mexico across a complex landscape that included grazed sand shinnery oak (Quercus havardii Rydb.), ungrazed sand shinnery oak treated with tebuthiuron, sand dunes, cropland, and Conservation Reserve Program native grass plantings. Based on data from 257 brood locations and 53 random locations, lesser prairie-chicken broods selected locations based on sand shinnery oak dominance, with taller plant heights and more over-head cover, when temperatures exceeded 26.4 degreesC than what was randomly available. Prairie chickens selected areas not treated with herbicide and these sites were often selected at a fine spatial scale. These data support other studies suggesting that there may be no justification of shrub control for lesser prairie-chicken conservation within the sand shinnery oak communities. 
    • Limitations to Postfire Seedling Establishment: The Role of Seeding Technology, Water Availability, and Invasive Plant Abundance

      James, Jeremy J.; Svejcar, Tony (Society for Range Management, 2010-07-01)
      Seeding rangeland following wildfire is a central tool managers use to stabilize soils and inhibit the spread of invasive plants. Rates of successful seeding on arid rangeland, however, are low. The objective of this study was to determine the degree to which water availability, invasive plant abundance, and seeding technology influence postfire seedling establishment. Across four fire complexes, whole plots were either seeded using a rangeland drill, seeded by hand where seeds could be placed at an exact depth, or left as unseeded controls. Irrigation and weeding treatments were applied to subplots within whole plots in an incomplete factorial design. In three of the four fires, seeding method was the single factor limiting establishment with seedling density over sevenfold higher in the hand-seeded compared to the drill-seeded treatments. In contrast to our hypotheses, water and weeding had no positive effect on seedling establishment in any of the four fires; however, background weed density was relatively low. The native community recovered at all sites with minimal bunchgrass mortality. These results strongly suggest a need for a decision framework that evaluates postfire seeding needs relative to natural recovery. Based on these initial results, it appears modest improvements in seeding technology may yield substantial increases in seeding success. 
    • Plant Community and Target Species Affect Responses to Restoration Strategies

      Hendrickson, John R.; Lund, Corie (Society for Range Management, 2010-07-01)
      Increases in Kentucky bluegrass and smooth bromegrass on northern Great Plains rangelands have the potential to negatively impact ecosystem function, lower plant diversity, and alter seasonal forage distribution, but control strategies are lacking in the region. A project was initiated on a heavily invaded 16-ha grassland that had not been grazed or hayed for at least 20 yr. Five restoration treatments and a control were initiated in 2003 on communities dominated by 1) smooth bromegrass (Bromus inermis Leyss.), 2) Kentucky bluegrass (Poa pratensis L.), 3) warm-season native grasses, 4) a mix of introduced species, and 5) smooth bromegrass and Kentucky bluegrass. Restoration treatments were 1) late-April burn, 2) late-April burn followed by imazapic at 511.62 mL ai ha-1, 3) imazapic only at the same rate, 4) mowing, 5) mowing followed by litter removal, and 6) control. We found that treatment responses were affected by target species, community category, and year. Generally, burning followed by the herbicide imazapic reduced Kentucky bluegrass in the species composition, but smooth brome was reduced by mowing followed by raking. Burning followed by imazapic reduced live grass biomass in all community categories except the native the year following treatment, but by the third year of the study live grass biomass was maintained across all treatments. In the third year of the study, responses of Kentucky bluegrass, other invasive species, and native grasses to restoration treatment differed depending on community. The use of burning plus imazapic was promising for control of Kentucky bluegrass but its use by producers may be limited by yield reductions in early years. Our data suggest management strategies should vary depending on whether the goal is to reduce one or several invaders, specific invader identity, and community type in which the invader is growing. We also found that the most effective strategy was an adaptive management approach, one where treatments are chosen in response to changes in community composition and depending on resource conditions. 
    • Seedling Interference and Niche Differentiation Between Crested Wheatgrass and Contrasting Native Great Basin Species

      Gunnell, Kevin L.; Monaco, Thomas A.; Call, Christopher; Ransom, Corey V. (Society for Range Management, 2010-07-01)
      Interference from crested wheatgrass (Agropyron cristatum [L.] Gaertn.) seedlings is considered a major obstacle to native species establishment in rangeland ecosystems; however, estimates of interference at variable seedling densities have not been defined fully. We conducted greenhouse experiments using an addition-series design to characterize interference between crested wheatgrass and four key native species. Crested wheatgrass strongly interfered with the aboveground growth of Wyoming big sagebrush (Artemisia tridentata Nutt. subsp. wyomingensis Beetle Young), rubber rabbitbrush (Ericameria nauseosa [Pall. ex Pursh] G. L. Nesom Baird subsp. consimilis [Greene] G. L. Nesom Baird), and to a lesser extent with bluebunch wheatgrass (Pseudoroegneria spicata [Pursh] A. Löve). Alternatively, bottlebrush squirreltail (Elymus elymoides [Raf.] Swezey subsp. californicus [J. G. Sm.] Barkworth) and crested wheatgrass had similar effects on each other’s growth, and interference ratios were near 1.0. Results indicate that the native grasses more readily establish in synchrony with crested wheatgrass than these native shrubs, but that once established, the native shrubs are more likely to coexist and persist with crested wheatgrass because of high niche differentiation (e.g., not limited by the same resource). Results also suggest that developing strategies to minimize interference from crested wheatgrass seedlings emerging from seed banks will enhance the establishment of native species seeded into crested wheatgrass-dominated communities. 
    • Vegetation Characteristics of Mountain and Wyoming Big Sagebrush Plant Communities in the Northern Great Basin

      Davies, Kirk W.; Bates, Jon D. (Society for Range Management, 2010-07-01)
      Dominant plant species are often used as indicators of site potential in forest and rangelands. However, subspecies of dominant vegetation often indicate different site characteristics and, therefore, may be more useful indicators of plant community potential and provide more precise information for management. Big sagebrush (Artemisia tridentata Nutt.) occurs across large expanses of the western United States. Common subspecies of big sagebrush have considerable variation in the types of sites they occupy, but information that quantifies differences in their vegetation characteristics is lacking. Consequently, wildlife and land management guidelines frequently do not differentiate between subspecies of big sagebrush. To quantify vegetation characteristics between two common subspecies of big sagebrush, we sampled 106 intact big sagebrush plant communities. Half of the sampled plant communities were Wyoming big sagebrush (A. tridentata subsp. wyomingensis [Beetle A. Young] S. L. Welsh) plant communities, and the other half were mountain big sagebrush (A. tridentata subsp. vaseyana [Rydb.] Beetle) plant communities. In general, mountain big sagebrush plant communities were more diverse and had greater vegetation cover, density, and biomass production than Wyoming big sagebrush plant communities. Sagebrush cover was, on average, 2.4-fold higher in mountain big sagebrush plant communities. Perennial forb density and cover were 3.8- and 5.6-fold greater in mountain compared to Wyoming big sagebrush plant communities. Total herbaceous biomass production was approximately twofold greater in mountain than Wyoming big sagebrush plant communities. The results of this study suggest that management guidelines for grazing, wildlife habitat, and other uses should recognize widespread subspecies as indicators of differences in site potentials.