• 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.
    • Plant responses to pine management and deferred-rotation grazing in north Florida

      Lewis, C. E.; Tanner, G. W.; Terry, W. S. (Society for Range Management, 1988-11-01)
      Responses of herbaceous and woody plants to combinations of 4 pine management and 4 grazing management systems were tested on a wet-flatwoods site in the pine-wiregrass vegetation type of north Florida. Frequency of occurrence of herbaceous species and foliar cover of woody species were determined in natural stands of 50-year-old slash and longleaf pine (Pinus elliottii Engelm. and P. palustris Mill.) and compared to similar forest sites that were harvested and site prepared by double-chopping and not replanted with slash pine, or replanted to 1,112 trees/ha in single- and double-row configurations. In addition, these sites were ungrazed or grazed using 3 deferred-rotation systems. Prescribed burning in the natural stands increased occurrence of most herbs and stimulated new species to occur, but had little effect on woody plant composition. However, harvesting of pines and double-chopping resulted in the occurrence of many new herbaceous species and increased occurrence of most initially present. Pineland threeawn (Aristida stricta Michx.), the major herb, initially decreased in occurrence with intensive site disturbance. Six years after disturbance, most herbaceous species were declining in occurrence. Grazing or growth of replanted pines had little influence on occurrence of herbaceous species. Both burning and mechanical disturbances initially reduced foliar ground cover of most woody species; however, few species were eliminated from the community. Most woody species were recovering within 6 yr from treatment, but succession was somewhat slower on mechanically treated areas. Survival and growth of planted pines were not affected by grazing, nor did planting configuration affect pine growth.
    • Season of cutting affects biomass production by coppicing browse species of the Brazilian caatinga

      Hardesty, L. H.; Box, T. W.; Malechek, J. C. (Society for Range Management, 1988-11-01)
      This paper reports the effect of season of cutting on coppice biomass production by 5 tree species common in the semiarid caatinga woodlands of northeast Brazil. Trees were cut early and late in the wet and dry seasons and coppice biomass production was monitored for 2 growing seasons after cutting. No mortality occurred as a result of cutting in any season. The effect of season of cutting on subsequent coppice production was most pronounced in the first year but differences persisted into the second year. Production by trees cut late in the wet season lagged behind that of trees cut at any other time. This was true for all species except marmeliero (Croton hemiargyreus Muell. Arg.) during both years. Pau branco (Auxemma oncocalyx Taub.) production was maximized by cutting late in the dry season. Jurema preta (Mimosa acutistipula Benth.) and catingueira (Caesalpinia pyramidalis Tul.) production was maximized by cutting early in the dry season. The season of cutting does not affect marmeliero stem production. Except for the late wet season, no treatment significantly affected sabiá Mimosa caesalpinifolia production. Stem biomass production is affected more by season of cut than is leaf biomass production. The different patterns of response among these species could be the basis of a selective cutting scheme to achieve objectives such as browse and wood production.
    • 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.
    • 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.