• Plant responses to gypsum amendment of sodic bentonite mine spoil

      Schuman, G. E.; Depuit, E. J.; Roadifer, K. M. (Society for Range Management, 1994-05-01)
      Abandoned bentonite mine spoils are extremely difficult to revegetate because of their high clay content, salinity, sodicity, low permeability, and the semiarid climate of the area where bentonite mining occurs. Recent research has led to the development of technology utilizing sawmill wastes (chips, bark, and sawdust) to enable the successful revegetation of these lands. The use of wood residue amendments increased water infiltration, leaching of soluble salts, and vegetation establishment; however, sodicity continued to be a problem and threatened to destroy the established vegetation. Surface application of gypsum was evaluated to determine its effectiveness in ameliorating the spoil sodicity and its effect on plant growth. In a 3-year field study, surficial gypsum amendment resulted in significant increases in perennial grass biomass (150%) and canopy cover (140%). These changes were not evident until the second or third year after gypsum amendment. Annual forb biomass did not respond to gypsum amendment; however, canopy cover did exhibit a significant increase in the second year at lower wood residue amendment rates. This research demonstrates that surface applied gypsum can be effective in ameliorating bentonite spoil sodicity when applied to established plant communities.
    • Predicting big sagebrush winter forage by subspecies and browse form class

      Wambolt, C. L.; Creamer, W. H.; Rossi, R. J. (Society for Range Management, 1994-05-01)
      Improved regression models were developed to predict winter forage production from big sagebrush (Artemisia tridentata Nutt.) through consideration of the subspecies variation among mountain big sagebrush (A.t. ssp. vaseyana [Rydb.] Beetle), Wyoming big sagebrush (A.t. ssp. wyomingensis Beetle and Young), and basin big sagebrush (A.t. ssp. tridentata). Changes in shrub morphology from browsing were also accommodated in our models. Colinearities among some variables used in previous studies were found and avoided in our models. Models used easily measured objective variables of which major axis and average cover of shrubs were most useful. Multivariable models without colinearities were evaluated on the basis of their R2a values which increased by an average of 10% to near 0.90, with taxa and browse form class included, compared to a model ignoring these differences.
    • Sites, mowing, 2,4-D, and seasons affect bitter-brush twig morphology

      Kituku, V. M.; Powell, J.; Olson, R. A. (Society for Range Management, 1994-05-01)
      Effects of site factors, mowing, 2,4-D, and seasons on antelope bitterbrush (Purshia tridentata Pursh.) twig length, basal and tip diameters, and weight were evaluated in southcentral Wyoming. Linear regression coefficients for twig length regressed on basal diameter were greater on productive sites than on less productive sites, greater on mowed areas than on sprayed or untreated areas, and greater in late fall because of leaves than in late winter. Twig elongation continued after data collection in early November. Twig length was more variable and more sensitive to different environmental conditions than twig basal diameter, tip diameter, or weight. Twig length accounted for 80-86% of the variation in twig weight. Sites, shrub management practices, and seasons do affect bitterbrush twig morphology, but habitat managers can use twig length-diameter-weight relations in this vegetation type to estimate utilization if the sampling is stratified along environmental gradients.
    • Sixty-one years of secondary succession on rangelands of the Wyoming high plains

      Samuel, M. J.; Hart, R. H. (Society for Range Management, 1994-05-01)
      The slow and uncertain rate of recovery of plant communities after severe disturbance is a major problem on rangelands. Earlier studies sketched the outline of secondary succession on mixed-grass prairie, but were based on 1 or 2 years of observation on different areas disturbed at different times in the past, or several years of observation of a single area. To provide a more complete picture of succession over decades, we began observations in 1977 on 4 areas disturbed from 1 to 51 years previously, and on undisturbed areas of the same 2 soil types with and without grazing. Observations continued for 11 years. Secondary succession proceeded through the usual stages: annual forbs, perennial forbs and annual grasses, short-lived perennial grasses, and long-lived grasses. Western wheatgrass [Pascopyrum smithii (Rydb.) A Love] was an exception because it appeared much earlier and in much greater abundance than other long-lived perennial grasses. Blue grama [Bouteloua gracilis (H.B.K.) Lag ex. Steud.) may be another exception; total recovery of this grass may require centuries. Time of appearance in succession seemed to be related to availability of propagules and ease of establishment; persistence of species was related to competitive ability. Abundance of many species fluctuated widely from year to year, but fluctuations did not appear to be related to precipitation. After 61 years, secondary succession had not returned plant communities to the climax state.