• A Relationship Between Competition and Sex Ratio of Shadscale

      Freeman, D. C.; Harper, K. T. (Society for Range Management, 1980-05-01)
      The sex ratio of shadscale populations within and outside grazing exclosures show significant departures from random expectations. Males are over represented within the ungrazed exclosures, while females are more prevalent in the grazed pastures. These unequal sex ratios could be the result of three factors: differences in genetic composition, differential grazing pressure on males and differences in water stress. Due to the increased plant cover within the ungrazed exclosures, we believe that plants inhabiting these sites are under greater water stress. Moreoever, it appears that females either tolerate water stress less well than males or change sex when stressed.
    • Aboveground Biomass Dynamics of Blue Grama in a Shortgrass Steppe and Evaluation of a Method for Separating Live and Dead

      Lauenroth, W. K.; Dodd, J. L.; Dickinson, C. E. (Society for Range Management, 1980-05-01)
      The relationship between live and dead biomass of blue grama and acetone extractable pigments was determined to assess its utility in predicting live and dead proportions of a mixed sample. We found the technique to be useful and recommend its use when exact separation is not required. Biomass dynamics of blue grama do not usually fit a parabolic model. Much of the variability in live biomass of blue grama can be explained by rainfall pattern during the growing season.
    • Accuracy of Roughage Intake Estimations as Determined by a Chromic Oxide-In Vitro Digestibility Technique

      Rosiere, R. E.; Galyean, M. L.; Wallace, J. D. (Society for Range Management, 1980-05-01)
      Intakes of roughage rations by two-year-old cows and heifers were estimated by a chromic oxide dilution technique and compared against actual measured levels of intake. Intake was overestimated 2.9 percent in cows and 28.6 percent in heifers. Linear regression was used to increase accuracy of intake estimates by developing equations to predict actual intake from values obtained by the indicator dilution approach. A system for using this approach under range conditions was suggested. It was shown that non-adjusted intake estimates were not absolute values and the assumption that estimated intake values are relative and adequate for comparison is valid only when ruminants consume similar diets.
    • Black-tailed Jackrabbit Diet and Density on Rangeland and Near Agricultural Crops

      Fagerstone, K. A.; LaVoie, G. K.; Griffith, R. E. (Society for Range Management, 1980-05-01)
      Black-tailed jackrabbit diets and densities were compared between rangeland and cultivated areas in southern Idaho to determine how heavily jackrabbits rely on crops for spring and summer food. Jackrabbit densities were significantly higher near cultivated crops than on the isolated rangeland. Where barley and crested wheatgrass plants were available to jackrabbits, they were preferred foods and made up a large part of the spring and summer diet. As potato plants were not a highly preferred food, crop, damage by jackrabbits could probably be reduced by planting potatoes in a buffer strip between rangeland and preferred grain crops. Plant phenology was a major factor in determining food preferences of jackrabbits collected on rangeland. In the spring, 85% of rangeland diet consisted of grass. However, in early summer, grasses and forbs were eaten in equal amounts and by late summer, 71% of the diet was comprised of forbs and shrubs.
    • Broadcast Burning of Sagebrush in the Winter

      Neuenschwander, L. F. (Society for Range Management, 1980-05-01)
      Sagebrush-grass vegetation occupies about 5.5 million hectares of Idaho rangelands. Rangeland productivity has decreased as presettlement sagebrush densities have increased. Prescribed burning of such rangeland has proven to be an efficient and economic tool to reclaim sagebrush- dominated areas, but firing techniques and weather prescriptions for fire use have not been developed. Feasibility of winter burning with snow or ice on the surface of the soil was tested with the following restrictions: (1) sagebrush was dense, with a canopy cover about 50%, and (2) distance between plants cannot exceed 50% of their average height. With these restrictions, fire carried through sagebrush canopies when effective wind speed was above 8 km/hr (5 mph) and winter ignition index was Y1 was greater than or equal to 29. Under the above prescription, only small areas burned. Winter burning might be impractical in most areas because of imposed stand limitations and the low number of days with proper burning conditions. However, winter broadcast burning is possible, inexpensive, and completely safe when snow or ice is present, and requires no fire control preparation or mop-up.
    • Classification and Ordination of Seral Plant Communities

      Huschle, G.; Hironaka, M. (Society for Range Management, 1980-05-01)
      A conceptual model of secondary succession was tested with data from disturbed vegetation in the Agropyron/Poa habitat type using a combination of classification and ordination techniques. Individual stands were classified into communities by an agglomerative method. Results of the Bray-Curtis polar ordination using three endpoint selection methods supported the validity of the model. The model is visualized as a solid cone in which all of the plant communities included in a habitat type are positioned relative to their degree of disturbance, inferring their probably secondary successional pattern within habitat types.
    • Correlation of Environmental Factors with Nitrate Concentration in Meadow Plants

      Gomm, F. B. (Society for Range Management, 1980-05-01)
      Earlier studies of meadow forages in eastern Oregon have shown that fertilizer-N increased yields and N concentration. How much of the increased N was NO3- N or how variations in environmental factors affected the accumulation of NO3 in meadow plants is not known. Plots of native meadow were fertilized on March 31 with ammonium sulfate to provide nitrogen levels of 0, 110, 220, 440 kg/ha. Changes in air temperature; soil temperature at the 0-, 5-, 10-, 20-, and 50-cm depths; luminous flux at canopy level, at 20 cm above ground, and at ground level; solar radiation over vegetation; and soil moisture content were monitored through the growing season. These data were statistically correlated with concentrations of NO3- N extracted from plant tissue. Herbage yields at the end of the growing season increased from 4,275 kg/ha without fertilizer to 9,782 kg/ha with 440 kg N/ha. Total-N concentration was highest (3.33%) on May 5 in herbage fertilized with 440 kg N/ha. As plants matured, concentration of total-N decreased by August 29 to 1.15% in plants receiving the 440 kg/ha rate and to 0.72% in unfertilized plants and was higher in the leaves than in the stems. Conversely, concentration of NO3- N were lowest (10-70 ppm) early in the season. Late in the growing season the NO3- N level was lowest in the leaves and highest (1,060 ppm) in the stems. Correlation analyses indicated that soil-moisture content was the most significant environmental factor correlated with accumulations of NO3- N, except for soil fertility as measured by increased fertilization rate. Luminous flux at ground level and air temperature were also contributing factors.
    • Cyanogenic Glycoside Levels in Saskatoon Serviceberry

      Majak, W.; Quinton, D. A.; Broersma, K. (Society for Range Management, 1980-05-01)
      The concentration of prunasin, the cyanogenic glycoside in Saskatoon serviceberry, was determined in leaves and twigs over a 12-month period. Eight shrubs were monitored, three of which were located in the ponderosa pine zone and the remainder in the Douglasfir zone. Qualitative tests indicated that the cyanide potential of serviceberry persisted continuously at all the experimental sites in both leaves and twigs. Quantitative analyses showed that prunasin levels in twigs were substantially higher in current year's growth as compared to previous year's growth. The highest prunasin levels were obtained in new growth of leaves and twigs following initiation and and this potentially hazardous period for browsers is described. Shrubs yielded lower prunasin levels when they were associated with ground water indicator species.
    • Establishment of Barbwire Russian Thistle in Desert Environments

      Evans, R. A.; Young, J. A. (Society for Range Management, 1980-05-01)
      Barbwire Russian thistle dominated a degraded plant community in the Carson Desert of northwestern Nevada and completely excluded Russian thistle in the course of the study. In seeding trials barbwire Russian thistle became established at low levels under arid conditions of the desert while Russian thistle failed to become established. Under semiarid conditions, seedling establishment of Russian thistle was five time greater than that of barbwire Russian thistle. Adaptations of barbwire Russian thistle that apparently favor seedling establishment under arid desert environments include earlier maturation and seed dispersal, seed dispersal beneath the parent plant, and less specific afterripening requirements than Russian thistle. These adaptations would permit germination and seedling establishment in the relatively wet periods of late winter and early spring in this arid ecosystem.
    • Frequency and Extent of Defoliation of Herbaceous Plants by Sheep in a Foothill Range Community in Northern Utah

      Hodgkinson, K. C. (Society for Range Management, 1980-05-01)
      Defoliation of individual plants by sheep grazing a shrub-steppe community in the foothill ranges of northern Utah was examined during a spring grazing. Five sites (each approx. 120 m2) within the paddock were monitored, and populations of one or more species (Aster chilensis, Wyethia amplexicaulis, Lupinus sericeus, Poa secunda, and Koeleria cristata) within these sites were examined daily for defoliation over a 25-day period. Grazing started at different times at each site, but once grazing started each site was visited daily. The proportion of the population of A. chilensis shoots that were grazed each day varied but was highest (about 30%) several days after grazing commenced at each site. Extent of defoliation of highly palatable species did not differ over time but did increase for W. amplexicaulis (forb of low palatability) at the end of the grazing period.
    • Grass, Trees, and Cattle on Clearcut-Logged Areas

      McLean, A.; Clark, M. B. (Society for Range Management, 1980-05-01)
      Generally, the presence of domestic grass had little effect on germination or survival of conifers on clearcut-logged areas, except where the stand of grass became overly dense. In cases where inhibiting effects were apparent, the competition from native vegetation was of as much consequence as the competition from domestic grasses. Results of the study suggest that where numbers of cattle and period of grazing were adequately controlled, damage to lodgepole pine and spruce seedlings were negligible. Damage was a result of repeated trampling rather than browsing. Poor cattle management in some situations resulted in overutilization of forage and large numbers of lodgepole pine seedlings were killed or damaged. However, the number was often insignificant in relation to the mortality of seedlings from natural causes. In a grazing trial the 4-year average daily weight gains were 0.64 kg for calves and 0.13 kg for their dams. Using the average weight gains and stocking rates, the pastures returned 60 kg of beef/ha/yr.
    • Impact of Incremental Surface Soil Depths on Infiltration Rates, Potential Sediment Losses, and Chemical Water Quality

      Lyons, S. M.; Gifford, G. F. (Society for Range Management, 1980-05-01)
      A study was conducted between October 1974 and August 1976 to measure the effects of incremented surface soil depths on infiltration rates, potential sediment production, and chemical quality of runoff water. The treatments were incremental removals of 7.6-cm soil layers to a depth of 30.5 cm on two pinyon-juniper sites in Utah. Hydrologic parameters were measured at each 7.6-cm incremental soil depth using a Rocky Mountain infiltrometer. With one exception, no significant differences occurred in infiltration rates among treatment depths during either 1975 or 1976 at either the Blanding (southeastern Utah) or Milford (southwestern Utah) site. A significant change in infiltration capacities was noted between the 1975 and 1976 field seasons when data from both treatment depths and study sites were pooled. There were no significant differences in potential sediment production between sites or among treatment depths at a site. In terms of chemical water quality, a significant change in phosphorus content of runoff waters was observed at the Blanding site between the 1975 and 1976 field seasons. Significant differences in potassium concentrations were found between sites and among soil depths. Nitrate concentrations were very low in runoff waters from all soil depths at both sites.
    • Impact of Incremental Surface Soil Depths on Plant Production, Transpiration Ratios, and Nitrogen Mineralization Rates

      Lyons, S. M.; Gifford, G. F. (Society for Range Management, 1980-05-01)
      From October 1974 to August 1976, a study was conducted to measure how incremental surface soil depths from the pinyon-juniper type affected plant production, plant transpiration rates, and nitrate nitrogen mineralization rates. The treatments were incremental removals of 7.6-cm soil layers to a depth of 30.5 cm. Plant production and transpiration ratios (or water use efficiencies) were measured in greenhouse studies using Agropyron desertorum grown in specified incremental 7.6-cm soil layers taken from five study sites throughout Utah. Significant decreases in plant production and increases in transpiration ratios were measured for all sites at incremental depths beyond 7.6-cm. These changes in plant production and transpiration ratios were linearly related to the nitrate nitrogen content of the soils (as determined when the soils were collected for use in the greenhouse). Nitrate mineralization rates were measured for two 6-week periods under field conditions at two sites for each of the 7.6-cm incremental soil layers. Nitrate nitrogen mineralization was linearly correlated with the organic carbon content of the soil. Decreased mineralization rates as measured in the field at both sites were reflected in the significant increases in plant water requirements and decreases in production that were measured in greenhouse studies.
    • Impact of Intensity and Season of Grazing on Carbohydrate Reserves of Perennial Ryegrass

      El Hassan, B.; Krueger, W. C. (Society for Range Management, 1980-05-01)
      Carbohydrate reserves of perennial ryegrass declined during winter and early spring and began replenishment during seed formation. The primary reserve accumulation in roots occurred during fall growth, while crowns replenished about half of their reserves from seed formation to fall and the balance during fall. Total nonstructural carbohydrate (TNC) reserves in roots were highest following a relatively wet year when compared to an average year but carbohydrate reserves were found to be more concentrated in the average year. Biomass of storage organs had a greater effect than concentration of carbohydrates on TNC reserves. Complete protection of perennial ryegrass from grazing did not induce greater accumulation of carbohydrate reserves when compared to any season of grazing treatment and they were sometimes significantly lower than for grazed treatments. No advantage from deferment of grazing in spring, summer, or fall could be determined based on carbohydrate reserves as along as stocking intensity did not exceed one ewe per 650 kg of herbage production per year. At stocking rates above this, deferment during part of the growing season should be beneficial.
    • Mineral Concentrations in True Mountain Mahogany and Utah Juniper, And In Associated Soils

      Brotherson, J. D.; Osayande, S. T. (Society for Range Management, 1980-05-01)
      Concentrations of minerals in soils and plants were measured in two communities. Zinc, copper, magnesium, phosphorus, and nitrogen showed significantly (p< 0.01) greater concentration in true mountain mahogany than in Utah juniper. Soils beneath plant canopies had significantly higher (p< 0.01) nitrogen than soils in open areas between plants. Concentrations of zinc, manganese, and phosphorus were significantly (p< 0.01) higher in the soils of the juniper community, while calcium and magnesium concentrations were significantly (p< 0.01) higher in the soils of the mountain mahogany community. True mountain mahogany showed copper concentration (x=28.9 ppm) high enough to approach toxic levels for some herbivores. Except for copper, mineral concentrations indicated good forage value for these two species.
    • Nitrogen Fixation (Acetylene Reduction) Associated with Rhizosheaths of Indian Ricegrass Used in Stabilization of the Slick Rock, Colorado Tailings Pile

      Wullstein, L. H. (Society for Range Management, 1980-05-01)
      Indian ricegrass sown on a sandy soil covering a uranium mine tailings exhibited associative nitrogen fixation (acetylene reduction). Acetylene reduction rates for whole plants varied from 2,100 to 19,500 nm/4 days. Nitrogen fixation was associated with the rhizosheaths. It is suggested that the reclamation of mine tailings in arid climates may be facilitated by stabilizing sandy textured coverings with rhizosheath-forming grasses.
    • Relationship of Distance Traveled with Diet and Weather for Hereford Heifers

      Ueckert, D. N.; Anderson, D. M.; Kothmann, M. M. (Society for Range Management, 1980-05-01)
      Distance traveled by Hereford heifers under continuous and high-intensity low-frequency (HILF) grazing was highly correlated with crude protein, digestible energy, forb content, and the ratio of grass leaf blade to stem plus leaf sheath obtained from diets collected via esophageal fistula. Observations confirmed that availability of palatable forbs was positively correlated with animal travel under HILF grazing management. Animal travel decreased under both management systems between July and December. Maximum diurnal temperatures and maximum diurnal water vapor, expressed as maximum mixing ratio, were significantly associated with travel under HILF grazing. Calculations indicated that the energy cost associated with horizontal travel for range cattle is greater than that allowed in the basal metabolism requirement set forth by the National Research Council.
    • Snow Trapping by Contour Furrows in Southeastern Montana

      Neff, E. L. (Society for Range Management, 1980-05-01)
      Contour furrows on fine-textured range sites in southeastern Montana caught an annual average of 22 mm more snow equivalent than nearby nonfurrowed areas. In addition, the furrows held snowmelt onsite in the spring and significantly reduced winter runoff in nearly half of the years of record. Except in years of much below normal winter precipitation, however, the winter runoff from furrowed areas was still more than adequate to fill well-designed stockponds.
    • Soil-Ingestion Rates of Steers Following Brush Management in Central Texas

      Kirby, D. R.; Suth, J. W. (Society for Range Management, 1980-05-01)
      Fecal soil concentrations and soil-ingestion rates were estimated for steers grazing pastures treated 1 year prior with herbicide or bulldozing and stacking. Mean fecal soil concentration was higher on mechanically treated, 16.6%, than those chemically treated, 12.5%, or untreated, 10.9%, under similar forage utilization levels (50%). With one exception, fecal soil concentration decreased over the study period on treated pastures. Fecal soil concentration was correlated with forb availability (r = 0.72) and percentage bare ground (r = 0.85) on treated pastures. At the forage utilization level of this study, no relationship between fecal soil concentration and stocking pressure was apparent.