• Vegetation Response to Piñon and Juniper Tree Shredding∗

      Bybee, J.; Roundy, B.A.; Young, K.R.; Hulet, A.; Roundy, D.B.; Crook, L.; Aanderud, Z.; Eggett, D.L.; Cline, N.L. (Society for Range Management, 2016)
      Piñon (Pinus spp.) and juniper (Juniperus spp.) expansion and infilling in sagebrush (Artemisia L.) steppe communities can lead to high-severity fire and annual weed dominance. To determine vegetation response to fuel reduction by tree mastication (shredding) or seeding and then shredding, we measured cover for shrub and herbaceous functional groups on shredded and adjacent untreated areas on 44 sites in Utah. We used mixed model analysis of covariance to determine significant differences among ecological site type (expansion and tree climax) and treatments across a range of pretreatment tree cover as the covariate. Although expansion and tree climax sites differed in cover values for some functional groups, decreasing understory cover with increasing tree cover and increased understory cover with tree reduction was similar for both ecological site types. Shrub cover decreased by 50% when tree cover exceeded 20%. Shredding trees at ≤ 20% cover maintained a mixed shrub (18.6% cover)-perennial herbaceous (17.6% cover) community. Perennial herbaceous cover decreased by 50% when tree cover exceeded 40% but exceeded untreated cover by 11% (20.1% cover) when trees were shredded at 15-90% tree cover. Cheatgrass (Bromus tectorum L.) cover also increased after tree shredding or seeding and then shredding but was much less dominant (< 10% cover) where perennial herbaceous cover exceeded 42%. Sites with high cheatgrass cover on untreated plots had high cheatgrass cover on shredded and seeded-shredded plots. Seeding and then shredding decreased cheatgrass cover compared with shredding alone when implemented at tree cover ≥ 50%. Vegetation responses to shredding on expansion sites were generally similar to those for tree cutting treatments in the SageSTEP study. Shredding or seeding and then shredding should facilitate wildfire suppression, increase resistance to weed dominance, and lead toward greater resilience to disturbance by increasing perennial herbaceous cover. © 2016 The Society for Range Management. Published by Elsevier Inc. All rights reserved.
    • Seed Production and Seedling Fitness are Uncoupled from Maternal Plant Productivity in Three Aridland Bunchgrasses

      Drenovsky, R.E.; Thornhill, M.L.; Knestrick, M.A.; Dlugos, D.M.; Svejcar, T.J.; James, J.J. (Society for Range Management, 2016)
      Maintaining self-sustaining populations of desired plants is fundamental to rangeland management, and understanding the relationships among plant growth, seed production, and seedling recruitment is critical to these efforts. Our objective was to evaluate how changes in maternal plant soil resource environment influences maternal plant biomass and seed production and seedling fitness in three widespread perennial bunchgrass species (Elymus elymoides [Raf.] Sezey, bottlebrush squirreltail; Festuca idahoensis Elmer, Idaho fescue; and Pseudoroegneria spicata [Pursh] A. Löve, bluebunch wheatgrass). We supplied water and nutrients to adult plants growing in the field and measured their productivity and fecundity. Then, in the laboratory, growth chamber, and field we assessed effects of the maternal water and nutrient additions on offspring performance. Across the three study species, vegetative traits were more plastic than reproductive traits, with resource addition measurably increasing plant growth but not seed production. Germination was high in both the laboratory and field across treatments, although seeds from irrigated maternal plants tended to have higher field germination. Seedling relative growth rate, leaf mass ratio, and relative root elongation rate (RRER) were highly variable, although RRER tended to be higher in seedlings derived from irrigated maternal plants. In the field, seedling survivorship was low across all species, but survivorship doubled in seedlings produced by P. spicata plants that received additional water through the growing season. Overall, our results suggest that biomass production and fecundity responses to nutrients are decoupled in the species and environment tested but maternal effects can have significant, although variable, impacts in some grassland species. As a result, biomass responses to natural and anthropogenic changes in resource availability may not be strong predictors of how altered resource supply may ultimately influence plant community dynamics in aridland systems. © 2016 The Society for Range Management. Published by Elsevier Inc. All rights reserved.
    • Livestock Use has Mixed Effects on Slender Orcutt Grass in Northeastern California Vernal Pools

      Merriam, K.E.; Gosejohan, M.C.; Weisberg, P.J.; Bovee, K.M. (Society for Range Management, 2016)
      Land managers often face the dilemma of balancing livestock use with conservation of sensitive species and ecosystems. For example, most of the remaining vernal pools in California are grazed by livestock. Vernal pools are seasonal wetlands that support many rare and endemic species, such as slender Orcutt grass (Orcuttia tenuis Hitchc.). Although studies in other areas of California have demonstrated that livestock use may benefit some vernal pool specialist species, grazing has been considered a threat to slender Orcutt grass in northeastern California. We evaluated the effects of livestock use on slender Orcutt grass using a replicated, paired design across a range of environmental conditions and grazing management regimes. Frequency, density, cover, reproductive potential, and height of slender Orcutt grass was compared in plots where livestock had been excluded with plots where grazing occurred. We found that livestock do not directly graze slender Orcutt grass, so the effects of livestock use on this species are indirect. These indirect effects are complex, including both positive, neutral, and negative effects. Year had the largest effect on slender Orcutt grass, probably as a result of variation in annual precipitation patterns. Livestock use had no effect in some years; in other years slender Orcutt grass was twice as abundant in unfenced than in fenced plots. Litter cover was also lower in unfenced plots in these years, suggesting that livestock use may benefit slender Orcutt grass in some years by reducing litter accumulation. Conversely, livestock use negatively affected slender Orcutt grass in pastures where livestock hoofprint cover was high, including pastures that were grazed early in the season. By considering patterns of annual variation in environmental factors such as precipitation, site conditions, and season of grazing, land managers can balance the needs of sensitive vernal pool species with maintaining livestock utilization on public lands. © 2016 The Society for Range Management. Published by Elsevier Inc. All rights reserved.
    • Impacts of Imazapyr and Triclopyr Soil Residues on the Growth of Several Restoration Species

      Douglass, C.H.; Nissen, S.J.; Meiman, P.J.; Kniss, A.R. (Society for Range Management, 2016)
      Herbicides are frequently used in natural systems to control invasive plants, but nontarget impacts from persistent soil residues can result in unintended ecosystem effects. Imazapyr and triclopyr are herbicides that are widely used in noncrop areas such as rangelands to manage perennial weeds, especially woody species such as tamarisk (saltcedar). Due to widespread environmental and anthropogenic changes in the American southwest, tamarisk, which is commonly thought to co-occur only with riparian plants, is increasingly being found in communities of upland rangeland species. Using an in vitro study combined with high-performance liquid chromatography (HPLC) analyses, imazapyr and triclopyr degradation rates were determined in six Colorado soils. In addition, the relative sensitivity of desirable species to the two herbicides was determined in a field dose response study. Exponential decay models estimated that triclopyr degradation (half-lives of 5-16 days) was 20 times more rapid than imazapyr degradation (half-lives of 82-268 days). All species tested were sensitive to imazapyr residues, but the degree of sensitivity was strongly dependent on soil properties. Sensitive species (alkali sacaton and western wheatgrass) were tolerant of imazapyr residues in some soils 20-23 months after applications. Relatively insensitive species (slender wheatgrass) were tolerant of imazapyr residues in the same soils 10 months after applications. American licorice was sensitive to triclopyr residues up to 89 days after applications, and several grasses (including sideoats grama) showed minor sensitivity. Our study indicates that there is an interaction between the spatial variability in herbicide degradation driven by edaphic properties and the sensitivity of plants to a herbicide, which could be exploited by management practitioners to aid in site rehabilitation. Specifically, managers could stagger planting of species temporally on the basis of their sensitivity to herbicide residues or could target areas of treated sites for planting that are known to have soil types facilitating relatively rapid herbicide degradation. © 2016 The Society for Range Management. Published by Elsevier Inc. All rights reserved.
    • Evidence-Targeted Grazing Benefits to Invaded Rangelands Can Increase over Extended Time Frames

      Rinella, M.J.; Bellows, S.E. (Society for Range Management, 2016)
      Targeted grazing uses livestock to address woody plant encroachment, flammable biomass accumulations, exotic weed invasions, and other management issues. In principle, a feature distinguishing targeted grazing from production-orientated grazing is stocking regimes (i.e., rates, timings, and durations) are chosen to encourage heavy defoliation of unwanted plants at sensitive growth stages. In practice, there are limited data available to guide stocking regime choices. Those data that do exist derive mostly from short-term studies, so the long-term effects of targeted grazing most concerning to managers remain highly uncertain. In a previous study, we imposed clipping treatments to identify defoliation levels and timings effective against the invader leafy spurge (Euphorbia esula L.). Most treatments simulated defoliation by sheep, the animal most commonly used for leafy spurge grazing, though a baseline treatment simulated defoliation by cattle, an animal tending to avoid leafy spurge. The two most effective treatments, which gave similar responses through the end of the previous study, defoliated leafy spurge and other species either before or during leafy spurge flowering. One goal of the current study was to determine if these responses remained similar or diverged over 5 additional treatment years. The other goal was to determine if differences between simulated sheep and cattle grazing treatments increased over time. In the current study, it became increasingly clear that defoliation before flowering was most damaging to leafy spurge, even though defoliation during flowering removed greater leafy spurge biomass. Compared with simulated cattle grazing, simulated sheep grazing before flowering reduced leafy spurge biomass production 74% (52%, 86%) [mean (95% confidence interval)] and increased resident species (mostly grasses) biomass production 40% (14%, 74%) by study's end. Leafy spurge biomass differences between treatments increased gradually over the study period, suggesting long-term research is needed to accurately compare targeted grazing treatments. © 2016 The Society for Range Management. Published by Elsevier Inc. All rights reserved.
    • Corrigendum to Greater Sage-Grouse and Range Management: Insights from a 25-year Case Study in Utah and Wyoming (Rangeland Ecology & Management (2015) 68 (375-382))

      Dahlgren, D.K.; Larsen, R.T.; Danvir, R.; Wilson, G.; Thacker, E.T.; Black, T.A.; Naugle, D.E.; Connelly, J.W.; Messmer, T.A. (Society for Range Management, 2016)
    • Effects of Using Winter Grazing as a Fuel Treatment on Wyoming Big Sagebrush Plant Communities

      Davies, K.W.; Nafus, A.M.; Boyd, C.S.; Hulet, A.; Bates, J.D. (Society for Range Management, 2016)
      More frequent wildfires and incidences of mega-fires have increased the pressure for fuel treatments in sagebrush (Artemisia) communities. Winter grazing has been one of many fuel treatments proposed for Wyoming big sagebrush (A. tridentata Nutt. subsp. wyomingensis Beetle and A. Young) communities. Though fire risk and severity can be reduced with winter grazing, its impact on vegetation characteristics of Wyoming big sagebrush plant communities is largely unknown. We evaluate the effect of winter grazing at utilization levels between 40% and 60% at five sites in southeastern Oregon. Winter grazing was applied for 5-6 yr before measurements. The winter-grazed and ungrazed treatments generally had similar vegetation characteristics; however, a few characteristics differed. The consumption of prior years' growth resulted in less large perennial bunchgrass, perennial forb, and total herbaceous cover and standing crop and litter biomass. Large perennial bunchgrass and perennial forb density and biomass and exotic annual grass and annual forb cover, density, and biomass did not differ between treatments, suggesting that winter grazing is not negatively impacting resilience and resistance of these communities. Shrub cover was also similar between treatments. These results imply that winter grazing can be applied to reduce fine fuels in Wyoming big sagebrush communities without adversely affecting the native plant community. Winter grazing should, however, be strategically applied because the reduction in perennial grass and perennial forb cover with the consumption of prior years' growth may negatively impact the habitat value for wildlife species that use herbaceous vegetation for concealment. © 2016 The Society for Range Management. Published by Elsevier Inc. All rights reserved.
    • Effects of Intermediate-Term Grazing Rest on Sagebrush Communities with Depleted Understories: Evidence of a Threshold

      Davies, K.W.; Bates, J.D.; Boyd, C.S. (Society for Range Management, 2016)
      Millions of hectares of sagebrush (Artemisia L.) plant communities have been degraded by past improper management, resulting in dense sagebrush stands with depleted herbaceous understories. Rest from grazing is often applied to promote recovery. However, the effect of intermediate-term (5-10 years) rest from grazing in sagebrush communities with depleted herbaceous understories and dense sagebrush is relatively unknown. We compared well-managed, moderate grazing (grazed) with intermediate-term (5 and 6 years) rest (ungrazed) at five sites in southeastern Oregon. Sites were Wyoming big sagebrush (Artemisia tridentata Nutt. subsp. wyomingensis Beetle & Young) communities with dense sagebrush and depleted herbaceous understories. Perennial herbaceous cover was greater in ungrazed compared with grazed areas, but this was expected because herbivory removes foliar vegetation tissue (i.e., cover). Density of herbaceous vegetation, diversity, and species richness did not differ between ungrazed and grazed areas. Similarly, bare ground, litter, and biological soil crust cover did not differ between treatments. These results suggest that intermediate-term rest is unlikely to elicit recovery of the understory compared with moderate grazing in these communities. The results of this study also suggest that degraded Wyoming big sagebrush communities likely have crossed a threshold that may be difficult to reverse. © 2016 The Society for Range Management. Published by Elsevier Inc. All rights reserved.
    • Compensatory Photosynthesis, Water-Use Efficiency, and Biomass Allocation of Defoliated Exotic and Native Bunchgrass Seedlings

      Hamerlynck, E.P.; Smith, B.S.; Sheley, R.L.; Svejcar, T.J. (Society for Range Management, 2016)
      Compensatory increases in net photosynthetic assimilation rates (Anet) following herbivory are well documented in adult rangeland grasses but have not been quantified in bunchgrass seedlings, which may be more sensitive to tissue loss than established plants. To address this, we twice removed 30% and 70% leaf area of seedlings of crested wheatgrass (Agropyron cristatum [L.] Gaertn., var. Hycrest II) and the native bluebunch wheatgrass (Psuedoroegnaria spicata [Pursh] Á. Love, var Anatone) and compared Anet and aboveground and belowground growth of these to unclipped control plants. Compensatory Anet occurred only after the second clipping, roughly 1 month after the first, and was similar in magnitude and duration between species and treatments, ca. 26% higher than control plant Anet for 2 weeks following clipping. Despite similar compensatory Anet between species, increases in Anet were more proportional with increased stomatal conductance to water vapor (gs) in crested wheatgrass. This resulted in higher intrinsic water use efficiency (WUEi = Anet/gs) integrated across the postclipping recovery period compared with WUEi of bluebunch seedlings, which declined with clipping. Differences in WUEi were attributable to differences in root-to-shoot ratios and root tissue quality (specific root mass; g dry mass · m-2 root area), which were lower in crested wheatgrass. We concluded that compensatory photosynthesis is an important component of seedling herbivory tolerance, and that observed differences in post-herbivory WUEi could help improve management strategies by informing seedling selection criteria to help develop methods aimed at minimizing impacts of herbivory during the seedling stage. © 2016 The Society for Range Management. Published by Elsevier Inc. All rights reserved.
    • Characterizing the Response of Piñon-Juniper Woodlands to Mechanical Restoration Using High-Resolution Satellite Imagery

      Meddens, A.J.H.; Hicke, J.A.; Jacobs, B.F. (Society for Range Management, 2016)
      In northern New Mexico, complex interactions among climate, land use, and the associated reduction of surface fire in forest and savanna communities facilitated the expansion of piñon-juniper woodlands. Because increasing tree cover can outcompete herbaceous vegetation (e.g., forbs and grasses), woodland expansion resulted in reduced herbaceous cover and increased soil exposure, leading to increased runoff and erosion. To improve hydrologic function in these degraded woodlands, an overstory thinning and slash-mulch treatment was applied to more than 1 000 hectares within Bandelier National Monument (New Mexico, United States) between 2007 and 2010. Our objective was to develop a remote sensing strategy to quantify land-cover changes following mechanical treatment of piñon-juniper woodlands. In this study, we 1) established a simple and repeatable method for assessing treatment effectiveness using high-resolution satellite imagery, 2) quantified vegetation response at six times since treatment (from 0.5 to 3.5 years), and 3) delineated areas of degraded woodland before and after treatment. We classified a 2006 QuickBird satellite image (before treatment) and a 2011 WorldView image (after treatment) to map tree cover, herbaceous cover, bare soil, and shadow with average overall accuracies of 95.0% and 94.7% for the 2006 and 2011 images, respectively. Following treatment, average tree cover, bare soil, and bare soil patch size decreased 9%, 4%, and 18%, respectively, while herbaceous cover increased 14%. Overall, the total amount of woodland area classified as degraded decreased by 34% post treatment. By comparison, control areas remained relatively unchanged across the same time period. Our results demonstrate the utility and promise of highresolution satellite imagery to inform rapid and objective assessments of landscape-scale restoration treatments. © 2016 The Society for Range Management. Published by Elsevier Inc. All rights reserved.
    • A Potential New Herbicide for Invasive Annual Grass Control on Rangeland

      Sebastian, D.J.; Sebastian, J.R.; Nissen, S.J.; Beck, K.G. (Society for Range Management, 2016)
      Downy brome (Bromus tectorum L.), a winter annual grass, is considered one of the most invasive non-native rangeland species in the United States. Although glyphosate, imazapic, and rimsulfuron are herbicides commonly recommended to control invasive, annual grasses, their performance is inconsistent and they can injure desirable perennial grasses. Indaziflam is a recently registered cellulose biosynthesis inhibiting herbicide, providing broad-spectrum control of annual grass and broadleaf weeds. Indaziflam is labeled for winter annual grass control in citrus, grape, and tree nut crops and could represent a new mode of action for selective winter annual grass control on rangeland. Three field experiments were conducted to compare indaziflam with imazapic, rimsulfuron, and glyphosate, three herbicides commonly used for downy brome control. Multiple herbicide application timings were evaluated. At all three sites, glyphosate and rimsulfuron provided less downy brome control than indaziflam 1 year after treatment (YAT). Percent downy brome control with imazapic decreased significantly 2 YAT (45-64%) and 3 YAT (10-32%). Across all sites and application timings, indaziflam provided the greatest downy brome control 2 YAT (89-100%) and 3 YAT (83-100%). Indaziflam did not significantly reduce species richness. This study demonstrates that indaziflam can provide extended downy brome control compared with currently used herbicides. © 2016 The Society for Range Management. Published by Elsevier Inc. All rights reserved.