• Defoliation of Thurber needlegrass: herbage and root responses

      Ganskopp, D. (Society for Range Management, 1988-11-01)
      Thurber needlegrass (Stipa thurberiana Piper) is an important component of both forested and shrub-steppe communities of the Pacific Northwest and Great Basin regions, and little is known of its tolerance to defoliation. A study was conducted on the Squaw Butte Experimental Range to determine the response of containerized Thurber needlegrass to single defoliations (2.5-cm stubble) throughout the growing season. Dates of treatment spanned vegetative through quiescent stages of phenology. Response variables included: summer regrowth, number of reproductive stems, fall growth, and subsequent spring herbage production, change in basal area, and root mass. Vigor of Thurber needlegrass was reduced most by defoliation during the early-boot stage of development. Impacts were successively less severe from vegetative, late-boot, and anthesis treatments, respectively. Cumulative herbage production the year of treatment was reduced from 38 to 64% by defoliation at the early-boot stage. The same treatment reduced subsequent spring growth by 46 to 51% and root mass the next spring by 34 to 45%. Treatment effects were somewhat reduced when temperature and moisture regimes allowed substantial regrowth after defoliation. Defoliation during or after anthesis had little effect on plant response. Managers should be aware that a single defoliation, particularly during the boot stage, can significantly reduce subsequent herbage production and root mass and possibly lower the competitive ability of Thurber needlegrass.
    • Effects of dormant-season herbage removal on Flint Hills rangeland

      Auen, L. M.; Owensby, C. E. (Society for Range Management, 1988-11-01)
      Stocking rate effects on intensive-early stocked Kansas Flint Hills range were studied from 1982 through 1987. Rates were 2X, 2.5X, and 3X normal season-long stocking rates for 200-225 kg steers. Study design was a randomized complete block with 2 replicates. Grass and forb standing crop (kg/ha) were estimated at the time of livestock removal (mid July) and again in early October. Plant basal cover and composition were taken in early June the year prior to the study and annually thereafter. Overall growing season precipitation during the study period was below normal, with late-summer precipitation much below normal in the second and third years of the study. Grass standing crop (GSC) in mid July decreased with increased stocking rate, but by early October GSC was similar under the 2.5X and 3X stocking rates, but continued to be lower than that under the 2X rate. There was no consistent response in mid July forb standing crop (FSC) with respect to stocking rate. In early October, FSC was either not affected by stocking rate (1983, 1986, and 1987) or was greater under the highest stocking rate (1982, 1984, and 1985). The major changes in botanical composition and basal cover were a reduction in Indiangrass (Sorghastrum nutans Nash) and an increase in Kentucky bluegrass (Poa pratensis L.) as stocking rate increased. Botanical composition of big bluestem (Andropogon gerardii Vitman) increased under the 2X rate but did not change under the higher rates. Individual steer gains were similar under the different stocking rates, but livestock breed appeared to affect magnitude of the gain. Since individual gains did not differ, gains per ha were substantially increased by the higher stocking rates.
    • Stability of grazed patches on rough fescue grasslands

      Willms, W. D.; Dormaar, J. F.; Schaalje, G. B. (Society for Range Management, 1988-11-01)
      Continuous stocking usually leads to the formation of grazed patches. However, the effect of patches on the grassland community is related to their stability. Therefore, we studied the spatial stability of grazed patches on Rough Fescue Grasslands by mapping forage removal classes on 10 sites over a 4-year period, testing stability using the Kappa index (K), and characterizing the soils and vegetation of overgrazed and undergrazed patches. Spatial stability of grazed patches between consecutive years was good (K is greater than or equal to 0.26) on sites experiencing low grazing pressure. However, on sites having high grazing pressure, spatial stability was less consistent between consecutive years (0>K is lesser than or equal to 0.45) and low over a 4-year period (K is lesser than or equal to 0.10). Overgrazed patches were dominated by grazing-resistant seral species, but undergrazed patches were dominated by climax species. Rough fescue (Festuca scabrella) and Parry oat grass (Danthonia parryi) plants were 50% shorter, and forage production was about 35% less, on overgrazed than on undergrazed patches. Soil organic matter, carbohydrates, and depth of Ah horizon were significantly greater on undergrazed patches but urease activity, NO3-N, NH4, and available phosphorus were greater on overgrazed patches. Overgrazed and undergrazed patches were stable in the long term, although patch boundaries fluctuated.
    • Stocking rate effects on intensive-early stocked Flint Hills bluestem range

      Owensby, C. E.; Cochran, R.; Smith, E. F. (Society for Range Management, 1988-11-01)