• Competition between cheatgrass and two native species after fire: Implications from observations and measurements of root distribution

      Melgoza, G.; Nowak, R. S. (Society for Range Management, 1991-01-01)
      During 1987 and 1988, a study was conducted in northern Nevada to examine root growth of cheatgrass (Bromus tectorum L.) and 2 native species, needle-and-thread grass (Stipa comata Trin. & Rupr.) and rabbitbrush (Chrysothamnus viscidiflorus (Hook.) NW.), after fire. Profile wall maps were used to determine the distribution of roots in the soil profile for the 2 native species. Root morphology differed between the 2 species: needle-and-thread grass had a flabelliform root system, whereas rabbitbrush had a main tap root with 2-4 major lateral roots. Although total root biomass differed between the species, more than half the root biomass was in the top 0.2 m of soil for both needle-and-thread grass and rabbitbrush. Measurements of root length density were used to evaluate the interaction between root systems of cheatgrass and the native species. Root production of plots with only the native species was not significantly different from that of plots with both the native species and cheatgrass for the first 2 years after fire. Furthermore, root production of plots in a recently burned area was also not significantly different from that in an area burned 12 years prior to our study. Thus, root systems of these species rapidly occupied the belowground space and competed for soil resources after fire, and the presence of cheatgrass partially reduced the root systems of the native species.
    • Cutting frequency and cutting height effects on rough fescue and parry oat grass yields

      Willms, W. D. (Society for Range Management, 1991-01-01)
      A study was made in the Rough Fescue Grasslands of southwestern Alberta to determine the yield response of rough fescue (Festuca scabrella var campestris Rydb.) and Parry oat grass (Danthonia parryi Scribn.) to 5 cutting frequencies and 3 heights over a 1-year period. The same plants were cut either 1, 2, 4, 8, or 16 times over a 16-week period beginning in mid-May, at 16-, 8-, 4-, 2-, or 1-week intervals, respectively, and at heights of either 5, 10, or 15 cm above ground level. Yield response to cutting treatments differed significantly from the flrst to the third treatment year. In the first year, rough fescue and Parry oat grass produced most forage when cut at a height of 5 cm with 1, 2, or 4 cuts. By the third year, rough fescue produced the greatest yields with a single cut after 16 weeks and Parry oat grass produced the greatest yields when cut at 10 or 15 cm at 1-week intervals. The data confirm the high sensitivity of rough fescue to grazing while the plant is growing and suggest that the greatest benefit from the Rough Fescue Grasslands may be derived by grazing in fall or winter. Summer grazing favors Parry oatgrass, which is more tolerant than rough fescue, but forage production on the grassland is reduced.
    • Some effects of precipitation patterns on mesa dropseed phenology

      Gibbens, R. P. (Society for Range Management, 1991-01-01)
      Phenology of mesa dropseed [Sporobolus flexuosus (Thurb.) Rydb.] was studied from 1979 to 1987 on the Jornada Experimental Range in southern New Mexico. Growing season (March through November) precipitation ranged from 99 to 308 mm during the 8-year period. Foliage height and number of leaves were recorded weekly for individually marked culms on 20 plants. New culms usually appeared during the first week in March and green leaf tissue often persisted until the end of November. Correlation analyses of accumulated weekly height increments and accumulated weekly precipitation showed that growth was highly dependent upon rainfall (r = 0.81 to 0.97). Leaf formation was also correlated with rainfall (r = 0.79 to 0.98). Even in relatively wet years tbere were 1 or 2 periods of no growth. In drier years, no growth periods totaled as much as 87 days. Periods of rapid growth occurred only after rainfall events > 13 mm. The first exsertion of seed heads occurred as early as the last week of July and as iate as the second week of October. The temporal plasticity of mesa dropseed phenology indicates that it is well adapted to the arid environment.
    • Substrate relations for rillscale [Atriplex suckleyi] on bentonite mine spoil

      Voorhees, M. E.; Uresk, D. W.; Trlica, M. J. (Society for Range Management, 1991-01-01)
      Rillscale (Atriplex suckleyi), the dominant native invader of bentonite mine spoil in northern Wyoming, is apparently uniquely adapted to this extremely harsh plant growth substrate. The objective of this study was to determine which chemical properties of spoil influence growth of rillscale. Plant production, foliar and spoil chemistry on spoils were treated as a factorial arrangement of treatments, each of 3 spoil amendments (gypsum, fertilizer, sawdust). Regression analyses with analysis of covariance and factorial analysis of variance model were used to control for effects of amendments on plant production. Calcium and nitrogen were growth-limiting nutrients for this plant. The species was very sensitive to an increase in the level of spoil molybdenum and in the ratio of copper to molybdenum, but was very tolerant of high levels of soluble sodium. Rillscale acted as a molybdenum accumulator.