• Caatinga vegetation dynamics under various grazing intensities by steers in the semi-arid Northeast, Brazil

      de Albuquerque, S. G. (Society for Range Management, 1999-05-01)
      The effects of cattle grazing were evaluated on range dynamics of the Caatinga which is a deciduous dry woodland, covering most of the semi-arid Brazilian Northeast. Three stocking rates (SR) were studied (heavy, 1 steer 6.7 ha(-1); moderate 1 steer 10 ha(-1); light, 1 steer 13.3 ha(-1)), in addition to an ungrazed exclosure (zero stocking). In the first phase (1978-81) each stocking rate was tested under continuous and deferred grazing. In the second phase (1981-84), deferred grazing was eliminated, so that pastures became replications of continuous grazing. Six steers per pasture were used, and pasture size was used to vary stocking rate. There was no effect of stocking rate or grazing system period on the frequency of the herbaceous species. They were, however, influenced by rainfall in the period, and could be divided into 3 groups. Sixteen species increased with increasing rainfall during the last months of the rainy season, and reached the highest frequency in 1984. Eleven species also increased with increasing rainfall but reached the highest frequency in 1983. Rainfall had no effect on the frequency of 2 important species. Herissantia crispa (L.) Briz. and Selaginella convoluta Spring. Death rate of 5 shrubs (Lippia microphylla Cham., Croton rhamnifolius (Kunth em.) Mull. Arg. Calliandra depauperata Benth. Cordia leucocephala Moric., and Bauhinia cheilantha (Bong.) Steud.) decreased with decreasing stocking rate, 11.7, 9.3, 7.7. and 4.5%, respectively on heavy, moderate, light, and zero stocking. Death rates were higher in easily broken shrub species. L. microphylla and C. leucocephala. Stocking rate also influenced the height growth rate of the tagged shrubs, being respectively -2.7 and 9.8% for heavy and zero stocking. Mean density of shrubs and trees, determined by the Point-Centered Quarter Method, was respectively 21,109, and 447 plants ha(-1) in 1982, and 13,230 and 401 plants in 1984; the main cause of the high shrub death (37.3%) was probably the 1982 drought. Density was not affected by stocking rate. Considering the 7 experimental areas separately, there was no regression between 1982 and 1984 shrub densities. There was, however, regression between 1982 density and the difference between 1982 and 1984 densities.
    • Cattle use affects forage quality in a montane riparian ecosystem

      Phillips, R. L.; Trlica, M. J.; Leininger, W. C.; Clary, W. P. (Society for Range Management, 1999-05-01)
      Forage nitrogen (N) and phosphorous (P) concentrations and in-vitro dry-matter digestibility (IVDMD) were measured in 2 important riparian species the year following short-term, high-intensity cattle grazing treatments in a montane riparian ecosystem in northcentral Colorado. Current year's growth of water sedge (Carex aquatilus Wahlenb.) and planeleaf willow (Salix planifolia Pursh.) was collected monthly from May to September 1996. The effects of grazing and season of grazing in 1995 on forage quality the following growing season was determined. Season of grazing (i.e., late-spring, early-summer, late-summer, and fall) the previous year did not differentially affect forage quality in either species. However, grazing by cattle the previous year did increase forage quality of water sedge as compared with plants that were not previously grazed. Grazed water sedge plants had higher concentrations of N and P and greater IVDMD than ungrazed controls. Nitrogen and P concentrations of browsed planeleaf willow were not different from controls, but current year's growth collected in the fall from previously browsed plants was 11% more digestible than current year's growth from non-browsed willow. The 2 species responded uniquely to cattle use, which suggested that these 2 life forms differ in response to herbivory. This study supported the hypothesis that grazing by cattle would improve forage quality in a riparian ecosystem, although results varied with life form.
    • Defoliation time and intensity of wall barley in the Mediterranean rangeland

      El-Shatnawi, M. K. J.; Ghosheh, H. Z.; Shannag, H. K.; Ereifej, K. I. (Society for Range Management, 1999-05-01)
      Wall barley (Hordeum murinum L.) is the dominant species in northeastern rangeland of Jordan that decreases under grazing. We investigated the responses of wall barley to clipping time and height during 2 growing seasons in the semiarid rangeland of Jordan. A natural stand was utilized to conduct the experiments that were arranged in a randomized complete block design during 1994/95 and 1995/1996 growing season. Treatments were combinations of clipping heights (5 or 10 cm above soil surface) and plant growth stages (tillering, jointing, or booting), in addition to unclipped check. Results showed that clipping to 5 and 10 cm stubble height at tillering produced 1,167 and 1,349 kg ha(-1) dry matter, respectively, compared to 1,122 kg ha(-1) for unclipped check. Clipping to 5 and 10 cm stubble height reduced shoot weight by 28 and 21% at jointing stage and 52 and 38% at booting stage. Defoliation during tillering stage did not impact plant height of regrowth nor seed yield. Weed biomass were higher when plant defoliation was delayed to the jointing and booting stages. Therefore, it is recommended to defoliate wall barley early at tillering stage but before plants reach jointing or reproductive stages.
    • Diet selection of mountain lions in southeastern Arizona

      Cunningham, S. C.; Gustavson, C. R.; Ballard, W. B. (Society for Range Management, 1999-05-01)
      Prey selection by mountain lions (Puma concolor) in the Aravaipa-Klondyke area in southeastern Arizona was studied from February 1991 to September 1993. Overall diet as determined from frequency of occurrence in 370 scats was 48% deer (Odocoileus virginianus cousi and O. hemionus combined), 34% cattle, 17% javelina (Tayassu tajacu), 6% rabbit (Sylvilagus spp. and Lepus californicus combined), 4% rodent, and 2% desert bighorn sheep (Ovis canadensis mexicanus). With respect to biomass consumed, cattle composed 44%, deer 40%, javelina 10.9%, rabbits 2.9%, and rodents 0.02%. Based on mean weights of prey consumed, the proportion of individuals killed and eaten changed to rabbits 52.7%, deer 16.3%, rodents 12%. javelina 10%, cattle 8%, and desert bighorn sheep 0.5%. Mountain lions selected deer less frequently than their availability would suggest, selected calves slightly more than their availability, and javelina as expected. We speculated that lions selected calves because they were more vulnerable to predation than deer.
    • Evidence of cell deterioration in winterfat seeds during refrigerated storage

      Booth, D. T.; Agustrina, R.; Abernethy, R. H. (Society for Range Management, 1999-05-01)
      Effective storage of wildland seeds helps alleviate supply shortages and mitigates variable production associated with annual weather patterns. The storage environment is critical for seeds like winterfat [Eurotia lanata (Pursh) Moq.] that rapidly lose viability under ambient conditions. Defining seed response to storage conditions is basic to effective seed storage programs. We used electron micrographs of freshly collected, and of stored winterfat seeds, with vigor tests to compare seedling vigor and to relate seed performance to seed cell biology as influence by; (a) seed age under known storage conditions, and (b) imbibition temperatures. We found that imbibition temperatures had little influence on the vigor of fresh seeds but significantly influenced aged seeds. Mitochondrial deterioration was evident in winterfat seeds stored 5-6 years at 5 degrees C, and in fresh, but incompletely hydrated seeds held at 20 degrees C. We recommend seeds be held at -18 degrees C or colder for long-term storage and that field seedings be done during the cold season to reduce the chance that incompletely hydrated seeds will be exposed to warm temperatures.
    • Grazing steer fecal output dynamics on south Texas shrubland

      Stuth, J. W.; Lyons, R. K. (Society for Range Management, 1999-05-01)
      Combined with other information, fecal output appears to have potential use in models to predict forage intake. Better understanding of fecal output dynamics relative to forage availability could improve model estimates of animal performance. Field trials were conducted during 4 different periods to investigate the relationship between 1) declining forage mass or forage component availability and beef steer fecal output and between 2) browse consumption and available forage mass. Fecal output was estimated using the rare-earth marker ytterbium. Initial fecal output as a percentage of body weight was greatest in March (1.24%) and least in August (0.96%). Regression slopes were negatively correlated (-0.73) with initial forage mass. As indicated by regression slopes, fecal output declined most rapidly in March (slope = 0.57) and slowest in August (slope = 0.13). Expression of available forage mass as either daily grass allowance or daily grass leaf allowance, both as g dry matter/kg live weight, produced similar regression equation statistics. Development of regressions for individual pastures within trials did, however, improve equation statistics in all trials except August. Browse consumption was < 10% until daily grass allowance fell below 50 g/kg live weight then increased to between 53 and 64% below 25 g/kg live weight, but was not adequate to maintain fecal output. Apparent seasonal differences in fecal output suggest lower forage intake (29%) in August compared to March. Fecal output was not affected by daily grass allowance above 100 g. Fecal output declined to below 0.6% of body weight below 100 g daily grass allowance. Data are interpreted to suggest that different fecal output curves and/or adjustment factors may be needed to account for season and initial forage mass.
    • Imbibition temperature affects winterfat (Eurotia lanata (Pursh) Moq.) seed hydration and cold-hardiness response

      Bai, Y.; Booth, D. T.; Romo, J. T. (Society for Range Management, 1999-05-01)
      Winterfat (Eurotia lanata (Pursh) Moq.) diaspores harvested from 1 Canadian and 2 USA sites were imbibed at 0, 5, 10, and 20 degrees C. It was hypothesized that imbibition temperature affects seed hydration which is related to cold-hardiness of winterfat. Weight gain was measured at 8-hour intervals until full hydration, and embryo water content was determined. Water content of fully hydrated seeds differed among collections and lower imbibition temperatures were always associated with greater seed water content. Differences in water content of seeds imbibed at different temperatures was related to cold-hardiness. When water content of embryos was measured, differences among imbibition temperatures existed, but were reduced. Differences in seed water content among imbibition temperatures were mainly due to endosperm other than the embryo because the embryo hydrated faster than other seed parts. Suggestions were made for modeling seed water relations based on this study.
    • Is supplementation justified to compensate pastoral calves for milk restriction?

      Coppock, D. L.; Sovani, S. (Society for Range Management, 1999-05-01)
      Competition for milk between calves and pastoral herders may reduce weaning weights, retard growth, and delay puberty in cattle. Calf supplementation could over-ride such effects and improve pastoral economies. To examine these issues in semiarid Ethiopia, 266 Boran calves (Bos indicus) were used in a 2 X 3 plus 1 factorial design contrasting graded levels of supplemental alfalfa hay (i.e., Medicago sativa L. with mean intakes of 0, 344, and 557 g head(-1) day(-1) on a DM basis) and supplemental water (i.e., with mean intakes of 0 and 3.8 liters head(-1) day(-1)). The trial was repeated for animals born in 2 consecutive years. Treatments occurred over a background of simulated traditional management in which calves had limited access to grazing and water and were allowed to suckle about two-thirds of their dams' daily milk yield. Traditionally managed controls received no supplements while other (positive) controls received no supplements but had greater access to milk. After 10 months of treatment calves were weaned and monitored. Supplementation with the high level of hay plus water markedly enhanced (P < 0.01) all productive features of calves at weaning compared to traditionally managed controls, and was an effective substitute for milk forgone in both years. Despite high variability in milk intake, access to supplements, and weaned body size as calves, all male cattle converged in liveweight and other productive features by 3.5 years of age, largely due to compensatory growth of traditionally managed controls. Heifers also converged in various attributes at maturity, but those which had received hay plus extra water as calves still conceived 2.6 to 4.3 months earlier (P < 0.05) than traditionally managed controls. We concluded that supplementation with hay and water can indeed compensate a young calf for typical levels of milk restriction here. Carry-over effects, however, were insufficient to justify large investments in supplementation considering the high inherent risks of production and traditions of marketing mature animals.
    • Late-summer forage on prairie sandreed dominated rangeland after spring defoliation

      Reece, P. E.; Holman, T. L.; Moore, K. J. (Society for Range Management, 1999-05-01)
      The potential of using spring defoliation to improve late-summer nutritive value of prairie sandreed [Calamovilfa longifolia (Hook.) Scribn.] on rangeland was studied with a factorial array of replicated 1-year treatments that included clipping plots at ground level or at a 5 or 10 cm height on 1 April, 26 April, 20 May, or 14 June. Vegetative tillers accounted for 83% of prairie sandreed herbage on unclipped control plots. After spring treatments, late-summer crude protein content (CP) in vegetative tillers of prairie sandreed ranged from 5.0 to 7.9% and in vitro dry matter digestibility (IVDMD) ranged from 45 to 52% compared to 5.0% CP and 45% IVDMD for unclipped plots. Reductions in mean weight of prairie sandreed vegetative tillers after April and May treatments were offset by 20 to 30% increases in tiller density. Treatments that increased tiller density had little or no effect on forage nutritive value when applied more than 90 days before herbage was sampled. Nutritive value of prairie sandreed and total yield from all species in mid-September were unchanged after April treatments. After sandreed tillers began to emerge in early May, late-summer nutritive value improved as clipping was delayed and degree of defoliation increased during May and June, however, yield was inversely related to nutritive value. While mid-September nutritive value of prairie sandreed was comparable to mid-summer values after June treatments, clipping reduced projected, late-summer stocking rates by 58 to 100% compared to control. It may be possible to improve mid-September forage nutritive value with moderate stocking rates in June with less reduction of total late-summer herbage because of selective herbivory. Measurable increases in prairie sandreed yield after complete defoliation of associated species in late April indicated prairie sandreed populations might be increased by concentrating cattle in selected pastures during late April.
    • Plant responses to defoliation and resource supplementation in the Pryor Mountains

      Fahnestock, J. T.; Detling, J. K. (Society for Range Management, 1999-05-01)
      Field studies were conducted in 2 types of grasslands in the Pryor Mountain Wild Horse Range of northern Wyoming and southern Montana to examine plant biomass production and nitrogen responses to the separate and combined effects of graminoid defoliation and increased environmental resource (water or nutrients) supply. Short-term plant responses were monitored over 2 years which differed substantially in growing season precipitation. In the arid, low elevation grassland, total grass biomass was significantly lower in the dry year than the wet year in all treatments. Defoliation of the grasses did not reduce their aboveground biomass production in the wet year, but severely reduced it in the dry year, primarily because of a decrease in tiller density. Mass of remaining individual tillers increased with clipping in the dry year, and nitrogen concentrations of the grasses increased with clipping in both years. Irrigation alone increased total belowground biomass compared to the other treatments, but did not increase the aboveground biomass production of any plant functional group. Clipping plus irrigation resulted in greater total aboveground biomass production and higher nitrogen concentrations of the grasses than control or irrigated treatments. Clipping graminoids in the more mesic montane grassland did not decrease their biomass production in either year, but did increase their nitrogen concentrations and increase the collective aboveground biomass production of the other plant functional groups. Fertilization and fertilization plus clipping significantly increased total aboveground biomass production in both years, and total belowground biomass was greatest in fertilized plots.
    • Rangeland cover component quantification using broad (TM) and narrow-band (1.4 NM) spectrometry

      Bork, E. W.; West, N. E.; Price, K. P.; Walker, J. W. (Society for Range Management, 1999-05-01)
      Calibrated predictive relationships obtained from simple and multiple regression of thematic mapper or broad-band (BB) and 1.4 nm interval or narrow-band (NB) spectral data were evaluated for quantifying 11 rangeland components (including total vegetation, forb, grass, shrub, litter, and bare soil) and distinguishing among 6 long-term grazing treatments of sagebrush steppe. In general, all 4 data types predicted similar values for each rangeland cover component. Multiple regression models usually had little advantage over simple regression models for predicting cover, particularly for abundant cover components, although this trend was inconsistent among components. Consequently, simple predictive models are recommended for quantifying rangeland indicator components using remotely-sensed data. The use of NB spectral data resulted in lower standard errors of prediction (SEP), although these reductions were inconsistent among rangeland components. Although both data types distinguished among grazing treatments with major plant compositional differences (P < 0.00) using a multivariate analysis of variance (MANOVA), only the NB data distinguished between grazing treatments with minor ecological differences (P < 0.01). These results suggest that in a practical context, NB data are advantageous for quantifying rangeland cover components and distinguishing among grazing treatments under the condition of our study.
    • Season-long grazing of seeded cool-season pastures in the Northern Great Plains

      Karn, J. F.; Ries, R. E.; Hofmann, L. (Society for Range Management, 1999-05-01)
      In the semi-arid Northern Great Plains, seeded cool-season grasses are primarily recommended for spring and fall grazing because their nutritive quality is perceived as too low to support acceptable animal weight gains during mid-summer. This perception is caused in part by traditional use of high spring stocking rates, which leave little forage remaining for mid-summer use. A study was conducted near Mandan, N.D. to determine the effect of moderate (1.6 AUM ha(-1)) and heavy (2.4 AUM ha(-1)) stocking rates on weight gains of yearling Hereford steers grazing crested wheatgrass (Agropyron desertorum [Fisch. Ex Link] Schult.), western wheatgrass (Pascopyrum smithii [Rydb.] Love), smooth bromegrass (Bromus inermis Leyss.) and flat (class II and III) and rolling (class IV and VI) native rangelands. Studies were conducted over a 140-day grazing season during 3 summers from 1992-1994. Grazing was initiated in mid-May and terminated the last week of September or the first week of October each year. At the end of each grazing season forage samples were clipped inside and outside of cages randomly located in each pasture to estimate end of season standing crop and forage utilization. Animal activity data were collected for 9 days during August and September 1994. Steer weight gains were not different among crested wheatgrass, western wheatgrass, smooth bromegrass and flat native pastures, but weight gains of steers grazing rolling native pastures were lower (P < 0.05) than gains on other pastures. Weight gains per steer were 8% higher (P < 0.05) on moderately grazed pastures, but weight gains per hectare were 39% higher on heavy grazed pastures. Steers spent more (P < 0.05) time grazing on smooth bromegrass than western wheatgrass, crested wheatgrass, or flat native pastures and they also spent more (P < 0.05) time grazing on heavy than moderately grazed pastures. Seeded cool-season grasses produced season-long yearling steer weight gains comparable to flat native, and superior to rolling native pastures, even when grazed at a stocking rate that was 80% heavier than the rate recommended for native rangeland by the USDA-SCS (1984). These results suggest that seeded cool-season grasses can be successfully grazed season-long in the Northern Great Plains where environmental conditions and precipitation patterns are comparable to central North Dakota.
    • Stream channel and vegetation responses to late spring cattle grazing

      Clary, W. P. (Society for Range Management, 1999-05-01)
      A 10-year riparian grazing study was conducted on a cold, mountain meadow riparian system in central Idaho in response to cattle grazing-salmonid fisheries conflicts. Six pastures were established along Stanley Creek to study the effects on riparian habitat of no grazing, light grazing (20-25% utilization), and medium grazing (35-50%) during late June. Stream channels narrowed, stream width-depth ratios were reduced, and channel bottom embeddedness decreased under all 3 grazing treatments as the area responded to changes from heavier historic grazing use. Streambank stability increased and streamside willow communities (Salix spp. L.) increased in both height and cover under all 3 treatments. Plant species richness increased on both streamside and dry meadow areas during the years of grazing and moderate drought. The numbers of species receded to near original levels in the ungrazed and light grazed pastures in 1996, a wet post-grazing year, primarily due to a decrease in forb species. Streamside graminoid height growth was similar among treatments after 1 year of rest. Most measurements of streamside variables moved closer to those beneficial for salmonid fisheries when pastures were grazed to 10 cm of graminoid stubble height; virtually all measurements improved when pastures were grazed to 14 cm stubble height, or when pastures were not grazed. Many improvements were similar under all 3 treatments indicating these riparian habitats are compatible with light to medium late spring use by cattle.