• Impact of SO2 Exposure on the Response of Agropyron smithii to Defoliation

      Lauenroth, W. K.; Detling, J. K.; Milchunas, D. G.; Dodd, J. L. (Society for Range Management, 1985-01-01)
      Agropyron smithii populations exposed to 3 controlled SO2 concentrations were defoliated either once or twice during the growing season at a light and a heavy intensity. The intensity and frequency of defoliation were most influential in determining growth and tillering responses. Defoliating twice, at either intensity, had a large negative impact on plant growth whereas compensatory growth occurred after defoliating once at either intensity. Sulfur dioxide alone had no significant effect on biomass or the number of tillers, even though sulfur accumulated approximately in proportion to exposure concentration. Sulfur dioxide exposure with the additional influence of defoliation affected both the regrowth of A. smithii in terms of biomass and tiller numbers and forage sulfur concentration. Decreased plant growth in response to SO2 plus defoliation was dependent on defoliation frequency, whereas the effect of SO2 plus defoliation on plant sulfur concentration was positive and negative and depended on a complex interaction of SO2 concentration and defoliation frequency and intensity. The results are discussed in relation to the short- and long-term compensatory growth potential of a system simultaneously exposed to grazing and air pollution and the potential effect on consumers.
    • Mechanical renovation of shortgrass prairie for increased herbage production

      Griffith, L. W.; Schuman, G. E.; Rauzi, F.; Baumgartner, R. E. (Society for Range Management, 1985-01-01)
      A study to determine the effects of single ripping, double ripping, and contour furrowing treatments was conducted on shortgrass rangeland in southeastern Wyoming from 1979-1982. The mechanical treatments changed species composition and increased total forage production over the control. Western wheatgrass (Agropyron smithii Rydb.) exhibited increased production on the treated areas compared to the control. Blue grama [Bouteloua gracilis (H.B.K.) Lag. ex Griffiths] production was significantly lower on the double ripping (1981 and 1982) and the contour furrow (1981) treatments than on the control. Needle-and-thread (Stipa comata Trin. & Rupr.) exhibited an increasing trend on the single and double ripping treatment over the control treatment all 4 years. Forbs also showed his trend in 1979, 1980 and 1981 on all renovation treatments, however little difference in forb production was evident in 1982. Total production differences were the greatest in the first year of renovation (1979) and in 1980 when the annual precipitation was below the long-term average. Increased livestock carrying capacities would result in payback of the renovation costs in 4 years.
    • Proline Concentrations in Water Stressed Grasses

      Bokhari, U. G.; Trent, J. D. (Society for Range Management, 1985-01-01)
      This study was conducted to screen several warm- and cool-season grasses for their proline-accumulating ability under water stressed conditions in the growth chamber. Plants of Old World bluestems (Bothriochloa spp.), tall fescue (Festuca arundinacea), western wheatgrass (Agropyron smithii) and weeping lovegrass (Eragrostis curvula) were subjected to water stress conditions at the vegetative stage. Water stressed plants exhibited a significantly greater (P<.05) increase in proline concentration than the non-stressed and the stress relieved plants. There was also a significant difference (P<.01) in the proline-accumulating ability of various species. An interdependency was observed between leaf water potential and proline concentration in all the species under water-stressed conditions.
    • Vegetational Traits of Patch-grazed Rangeland in West-Central Kansas

      Ring, C. B.; Nicholson, R. A.; Launchbaugh, J. L. (Society for Range Management, 1985-01-01)
      Indices of vegetation abundance, composition, and grazing were monitored for the grazing seasons of 1980-81 at Hays, Kans., in 2 pastures. One pasture was moderately grazed with yearling steers season-long, while the other was triple-stocked for only the first half of the season. Some areas were grazed repeatedly throughout the grazing seasons, resulting in overgrazed patches, which increased in number as seasons progressed. By the end of each grazing period, more than 70% of each pasture was grazed, but only 23-56% of the areas consisted of overgrazed patches depending on the year and treatment. Grazing treatment also influenced whether the locations of patches remained the same from year to year. Species composition of overgrazed patches was different from the surrounding vegetation, but soil properties were not.