• Control of threadleaf rubber rabbitbrush with herbicides

      Whisenant, S. G. (Society for Range Management, 1988-11-01)
      Foliar sprays of 2,4-D [(2,4-dichlorophenoxy)acetic acid]), picloram (4-amino-3,5,6-trichloro-2-pyridinecarboxylic acid), dicamba (3,6-dichloro-2-methoxy benzoic acid), or clopyralid (3,6-dichloro-2-pyridinecarboxylic acid) were applied in 30 or 150 L of total spray solution ha-1 to threadleaf rubber rabbitbrush [Chrysothamnus nauseosus ssp. consimilis (Greene) Hall & Clem] in Garfield County, Utah. Additional herbicide treatments were applied in 150 L ha-1 in Sevier County, Utah. Herbicides were less effective when applied in 30 L ha-1 than when applied in 150 L of total spray solution ha-1. Mortality was 74 to 87% following applications of 4.4 kg a.e. (acid equivalent) 2,4-D ha-1. Dicamba applied at 3.3 kg ha-1 resulted in 70 to 87% mortality, and picloram applied at 0.8 kg ha-1 resulted in 56 to 79% mortality. The greatest mortalities (84 to 97%) occurred on areas treated with 2.2 kg clopyralid ha-1. Mortality of threadleaf rubber rabbitbrush increased an average of 28, 17, 33, and 27% following applications of 2,4-D, dicamba, picloram, and clopyralid respectively, by using 150 L spray volume. Greatest increases were at the lowest herbicide rates. Applying herbicides in greater amounts of carrier (water) significantly increased both mortality and canopy reduction of threadleaf rubber rabbitbrush for at least 39 months.
    • 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.
    • Species diversity and diversity profiles: concept, measurement, and application to timber and range management

      Lewis, C. E.; Swindel, B. F.; Tanner, G. W. (Society for Range Management, 1988-11-01)
      The concepts and use of several diversity assessments are presented and applied to a practical situation. Burning, mechanical methods of site preparation, and cattle grazing are common disturbances in forests of the South. Their influence on plant diversity indices are examined in a longleaf-slash pine forest of north Florida. Species richness, Shannon's index, and Simpson's index showed increases in diversity shortly following burning and site preparation and a trend toward pre-treatment conditions after 6 years. Deferred-rotation grazing systems had no influence. Comparative diversity profiles showed similar trends but were more informative by providing both qualitative and quantitative information. These techniques are useful for assessing community responses to management practices, that is, they are effective methods for understanding the impacts of forest management and range management practices on plant community structure and succession.
    • Stability of African pastoral ecosystems: Alternate paradigms and implications for development

      Ellis, J. E.; Swift, D. M. (Society for Range Management, 1988-11-01)
      African pastoral ecosystems have been studied with the assumptions that these ecosystems are potentially stable (equilibrial) systems which become destabilized by overstocking and overgrazing. Development policy in these regions has focused on internal alterations of system structure, with the goals of restoring equilibrium and increasing productivity. Nine years of ecosystem-level research in northern Kenya presents a view of pastoral ecosystems that are non-equilibrial but persistent, with system dynamics affected more by abiotic than biotic controls. Development practices that fail to recognize these dynamics may result in increased deprivation and failure. Pastoral ecosystems may be better supported by development policies that build on and facilitate the traditional pastoral strategies rather than constrain them.