• Litter Reduction by Prescribed Burning Can Extend Downy Brome Control

      Kessler, K. C.; Nissen, S. J.; Meiman, P. J.; Beck, K. G. (Society for Range Management, 2015-07)
      Downy brome (Bromus tectorum L.) is a highly successful invasive species primarily because it fills an open niche in native plant communities. It also produces large amounts of litter over time. We hypothesized that removing accumulated litter with a prescribed burn before applying herbicides would improve herbicide efficacy, extending the duration of control. In January 2012, two downy brome-infested sites were burned. In March 2012, postemergent applications of glyphosate, imazapic, and tebuthiuron were made in a split-plot design. Above-ground biomass was collected at 6, 18, and 27 months after treatment (MAT) to evaluate treatment effects. In nonburned areas, all herbicide treatments were similar to the control 27 MAT; however, burning combined with imazapic or tebuthiuron reduced downy brome biomass 27 MAT by 81% ± 4.6 SE and 84% ± 19.3 SE, respectively. Remnant species responded positively to burning and herbicide treatments. Native cool-season grass biomass increased after burning whereas native warm-season grass biomass increased following tebuthiuron treatments. The impact of litter on imazapic and tebuthiuron availability was also evaluated. Herbicide interception increased in a linear relationship with increasing litter. For every 50 g · m-2 increase in litter there was a 7% increase in the amount of herbicide intercepted, meaning that 75% of the applied herbicide was intercepted by 360 g · m-2 of litter. A simulated rainfall event of 5 mm, 7 days after application, removed a significant amount of herbicide. This indicates that in sites with surface litter, timely precipitation could be critical for herbicide efficacy; however, when burning was used to remove litter and was followed by herbicides with residual soil activity, downy brome control was extended. Due to downy brome's relatively short seed viability in the soil, extending herbicide efficacy to several years could help to reduce the soil seed bank. © 2015 Society for Range Management. Published by Elsevier Inc. All rights reserved.
    • Long-Term Trade-Offs among Herbage Growth, Animal Production, and Supplementary Feeding in Heavily Grazed Mediterranean Grassland

      Henkin, Z.; Ungar, E. D.; Perevolotsky, A.; Gutman, M.; Yehuda, Y.; Dolev, A.; Landau, S. Y.; Sternberg, M.; Seligman, N. G. (Society for Range Management, 2015-07)
      A 17-yr grazing trial was conducted in the eastern Galilee of Israel to quantify trade-offs among the responses of pasture and livestock productivity, duration of grazing, amount of supplementary feed, and profitability to higher stocking density during the growing season of a Mediterranean grassland. Treatments included two stocking densities and two grazing protocols. The stocking densities throughout the grazing period were 0.55 animal unit (AU)·ha-1, which is common in this region, and 1.1 AU·ha-1, which is considered high. The grazing protocols were continuous grazing throughout the grazing season and split-paddock grazing in which the herd grazed one subpaddock from the onset of grazing until the pasture was depleted, after which the herd was moved to the second ungrazed subpaddock. Under both protocols, heavier stocking density reduced standing biomass of the whole paddock at the end of the growing season by 43% and grazing duration during the subsequent dry season by 38% but increased the daily consumption of supplementary feed and the weaned live-weight production per unit area. Under continuous grazing the high stocking density of 1.1 AU·ha-1 was maintained throughout the grazing season for 17 consecutive yr with no detectable effect on productivity of the pasture, typical to the resilience of Mediterranean grasslands that have been grazed for thousands of years. The lower pasture biomass production was compensated by higher weaned calf production. At the current local prices, the heavier stocking density was close to the economically optimal stocking density for the pasture in the region. It is concluded that on Mediterranean grassland intensive use of the pasture with high stocking density during the growing season can be economically feasible in those cases where the feed requirement of the herd can be maintained throughout the growing season. © 2015 Society for Range Management. Published by Elsevier Inc. All rights reserved.
    • Restoration of Native Plants is Reduced by Rodent-Caused Soil Disturbance and Seed Removal

      Gurney, C. M.; Prugh, L. R.; Brashares, J. S. (Society for Range Management, 2015-07)
      Granivory and soil disturbance are two modes by which burrowing rodents may limit the success of native plant restoration in rangelands. This guild of animals has prolific effects on plant community composition and structure, yet surprisingly little research has quantified the impact of rodents on plant restoration efforts. In this study, we examined the effects of seed removal and soil disturbance by the giant kangaroo rat (Dipodomys ingens) on native plant restoration in a California rangeland. Using experimental exclosures and stratifying restoration plots on and off rodent-disturbed soil, we assessed the individual and combined effects of seed removal and soil disturbance on seedling establishment of four native plant species. Across all species, biotic soil disturbance by kangaroo rats reduced seedling establishment by 19.5% (range = 1-43%), whereas seed removal reduced seedling establishment by only 6.7% (range = 4-12%). Rates of seed removal across species weakly paralleled kangaroo rat dietary preferences. These results indicate the indirect effects of burrowing rodents such as kangaroo rats on native seedling establishment via changes in soil properties may rival or exceed the direct effects of seed removal. © 2015 Society for Range Management. Published by Elsevier Inc. All rights reserved.
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      Society for Range Management, 2015-07
    • Stocking Rates and Vegetation Structure, Heterogeneity, and Community in a Northern Mixed-Grass Prairie

      Lwiwski, T. C.; Koper, N.; Henderson, D. C. (Society for Range Management, 2015-07)
      Currently, livestock management in the North American Great Plains aims for even use of forage, which creates a homogenous landscape. Reintroducing heterogeneity, defined here as the variation in vegetation structure and composition, to native North American rangelands is imperative to maintaining grassland biodiversity, and using a variety of cattle stocking rates on the landscape could accomplish this. We assessed effects of stocking rates on northern mixed-grass prairie vegetation structure, structural heterogeneity, and plant species diversity. The study took place in Grasslands National Park in Saskatchewan, Canada, using nine pastures (∼300 ha) that were grazed at a range of stocking rates from very low to very high for this region. Three of these pastures were ungrazed controls. We used generalized linear mixed models to describe effects of stocking rate on vegetation over 4 years, following the reintroduction of livestock grazing to this landscape after 15 years without grazing. We used a Mantel test to determine whether plant communities changed with varying stocking rates and over time. Effects of grazing on many response variables were cumulative and changed over time. Species richness in uplands increased with stocking rate and time, but richness decreased with stocking rate in lowlands. Heterogeneity generally increased with stocking rate and time in upland but not lowland habitats. While natural annual variability influenced many variables, the cumulative effects of grazing were still apparent. A variety of stocking rates could be used to maximize structural heterogeneity and provide a diversity of habitat structure at the landscape scale. © 2015 Society for Range Management. Published by Elsevier Inc. All rights reserved.