• Germination Characteristics of Helianthus maximilianai Schrad. and Simsia calva (Engelm. and Gray) Gray

      Owens, D. W.; Call, C. A. (Society for Range Management, 1985-07-01)
      Germination characteristics of Maximilian sunflower (Helianthus maximiliana Schrad.) and awnless bushsunflower {Simsia calva Engelm. & Gray) Gray were evaluated at water potentials of 0, -.25, -0.50, -0.75, and -1.0 MPa under alternating temperature regimes of 10/20, 15/25, and 20/30 degrees C in controlled environmental chambers. Cumulative germination was greatest for both species at water potentials of 0 and -0.25 MPa in the 15/25 degrees C temperature regime. Germination total and rate were depressed for both species in the 10/20 degrees C regime. The 20/30 degrees regime depressed total germination but increased germination rate. The adverse effects of more negative water potentials (-0.75 and -1.0 MPa) were more pronounced at low temperatures for awnless bushsunflower and high temperatures for Maximilian sunflower.
    • Growth and Development of Pinegrass in Interior British Columbia

      Stout, D. G.; Brooke, B. (Society for Range Management, 1985-07-01)
      Pinegrass (Calamagrostis rubescens Buckl.) is an important source of forage on forested and clearcut ranges in interior British Columbia. The vegetative growth and development of this infrequently flowering grass was documented. This information is required to improve our understanding of pinegrass grazing resistance and in turn, of its grazing management. Numbers of tillers m-2 and number of leaves per tiller were counted at intervals during the growing seasons of 1978 and 1979. Leaf blade area was measured at intervals during 1978 and 1979. Tiller height was recorded during 1978, 1979, and 1982, while shoot weight was recorded at intervals during 1982. Pinegrass had up to 4 leaves per tiller, but on average only 3.2 leaves were present by the time growth ceased in July. Total leaf blade area was reached in July, and is largely comprised of 2 leaves. Total leaf blade area (y) was predicted from tiller height (x):y = 0.39375 + 0.051604x + 0.00419223x^2 (R2=0.97). A large proportion of leaf blade area was dead by the end of July. Tiller weight reached a maximum in July; it increased during May to July owing to an increase in number of leaves, leaf area, and specific weight of leaves. Growth analysis indicated that net assimilation rate (NAR), and relative growth rate (RGR) were high in mid-May and then gradually decreased to zero in July. NAR and RGR of pinegrass appeared typical for C3 plants.
    • Growth Parameter Differences between Populations of Blue Grama

      Samuel, M. J. (Society for Range Management, 1985-07-01)
      Samples of blue grama were obtained from disturbed and undisturbed areas of native rangeland in southeast Wyoming. Assumed 'slow-spread' populations were selected along a 50-year-old plowline from blue grama sod which had spread only a few centimeters into the plowed area. Assumed 'fast-spread' populations were selected from large plants within the plowed area. Control populations were selected at random from the undisturbed native range. Plants from 15 populations were grown in a dryland, uniform garden where basal spread was measured to determine if there were differences in rate of spread between populations of blue grama. Herbage production, plant height, and phenology were also compared. By the end of the second and fourth seasons of growth in the uniform garden, the fast-spread populations had spread 21 and 20% more than the slow-spread populations. The random populations were 17 and 11% larger than the slow-spread populations during the same year. The fast-spread and random populations were not different.
    • Influence of Canopy Characteristics of One-seed Juniper on Understory Grasses

      Schott, M. R.; Pieper, R. D. (Society for Range Management, 1985-07-01)
      Studies were conducted in the Sacramento Mountains, New Mexico, to determine the influence of juniper (Juniperus monosperma [Engelm.] Sarg.) canopy on understory vegetation. The basal area of grass species was estimated at 6 locations beneath the canopies of 50 one-seed junipers. Other parameters measured were litter depth, canopy height, canopy cover, canopy closure, tree height, trunk diameter, north-south crown diameter, and east-west crown diameter. Locations adjacent to the trunk had the greatest juniper canopy cover and litter depths, and the lowest height to canopy. Locations at the end of the canopy had the least crown cover and litter depths, and the greatest height to canopy. All but one of the grass species had greater basal areas at the edge locations and the least at the interior locations beneath juniper canopies. Pinyon ricegrass (Piptochaetium fimbriatum [H.B.K.] Hitch.) was the exception; it was never found at the exterior locations. Regression models indicated that shading influenced the basal areas of most grass species. Litter depth was negatively correlated with grass basal cover in only 4 models and positively correlated in 1. Basal area of pinyon ricegrass was positively correlated with trunk diameter, a reflection of tree age, indicating that the grass requires time to become established. Also, basal area of pinyon ricegrass was positively correlated with canopy cover, indicating that this species requires the modified microenvironment afforded by shading.
    • Magnification and Shrub Stemmy Material Influences on Fecal Analysis Accuracy

      Holechek, J. L.; Valdez, R. (Society for Range Management, 1985-07-01)
      When 100X and 200X microscope magnification levels were used singly and interchangeably in microhistological analysis, magnification level had no effect (P<.05) on diet botanical composition of 60% grass and 60% forb diets containing 6 forage species fed to mule deer. However, large differences occurred between magnification levels for individual plant species in a 60% shrub diet containing the same forage species. The use of the 100X and 200X magnification levels interchangeably was slightly more accurate than exclusive use of either magnification level for the high grass and high shrub diets. For fecal analysis our study shows 100X and 200X microscope magnification levels can be used singly or interchangeably with little influence on accuracy. Use of the 100X magnification level to scan fields for potentially identifiable fragments followed by switching to 200X magnification for better resolution of fragments difficult to discern can slightly improve both speed and accuracy. Fourwing saltbush, which had a high proportion of stemmy material relative to leaves, was severely underestimated in the feces of all 3 diets. Our data indicate fecal analysis has limited value as an estimator of diets of herbivores, such as mule deer, that consume significant but variable quantities of stemmy material from shrubs.
    • Ranch Resource Differences Affecting Profitability of Crested Wheatgrass as a Spring Forage Source

      Spielman, K. A.; Shane, R. L. (Society for Range Management, 1985-07-01)
      A representative cow-calf ranch operation in Elko County, Nev., was modeled using a linear programming procedure to determine effects of selected ranch resource differences on profitability of seeding crested wheatgrass. Net present value (NPV) results suggest seeding crested wheatgrass as a spring forage can be a profitable investment if there are associated increases in calf weaning weights of 9.07 kg and increases in calving rates of 5 percentage points. Amount of meadow hayland, deeded range, and BLM forage available to the representative ranch were increased and decreased 50%. NPV's of the crested wheatgrass investment are greater for ranches with excess meadow hay and excess deeded range. NPV's are lower for ranches with limiting resources of meadow hayland, deeded range, and BLM forage.
    • Response of Vegetation of the Northern Great Plains to Precipitation Amount and Grazing Intensity

      Olson, K. C.; White, R. S.; Sindelar, B. W. (Society for Range Management, 1985-07-01)
      Changes in basal cover of vegetation were predicted in response to variation in precipitation and grazing intensity. Multiple regression analysis was used with basal cover as a dependent variable and precipitation parameters as independent variables to develop predictive equations. Predicted cover values were used to develop three dimensional response surfaces which describe individual species responses to fluctuating precipitation and different grazing intensities. Results indicate that each species reacts to precipitation regimes and grazing pressure in a unique manner. Continual changes in basal cover can be expected in the plant community as the precipitation regime changes. Moderate grazing intensity, approximately 0.92 ha (2.3 acres) per AUM, appears to be most conducive for maintaining vegetative cover that is desirable for livestock production. However, stocking rate changes need to be anticipated and planned to coincide with available forage because of large fluctuations in cover due to varying precipitation.
    • Soil and Vegetation Relationships in a Central Plains Saltgrass Meadow

      Bowman, R. A.; Mueller, D. M.; McGinnies, W. J. (Society for Range Management, 1985-07-01)
      A field study was conducted in a saltgrass (Distichlis stricta) meadow at the Central Plains Experimental Range to investigate relationships between soil types, salinity, sodicity, fertility, and vegetation ground cover and species composition. Three line transects that included 48 soil cores and their adjacent vegetation cover were sampled. Soils data indicated relatively good homogeneity between transect 1 and 3 with transect 2 exhibiting the poorest soil physical characteristics because of shallow A horizon and high sodium. Species composition averaged across transects reflected in general the following magnitude of ground cover distribution over the 1979-1983 seasons: blue grama (Bouteloua gracilis) > alkali sacaton (Sporobolus airoides) > saltgrass > western wheatgrass (Agropyron smithii). Species nutrient concentration data showed western wheatgrass with the highest concentration of N and K, alkali sacaton highest in P, Ca, Mg, and Na. Saltgrass was assimilating primary NaCl and alkali sacaton NA2SO4. Blue grama showed low Na and Cl concentrations, which suggested a superficial rooting pattern above the saline horizons. Plant-soil correlations for all transects are discussed.
    • Some Responses of Riparian Soils to Grazing Management in Northeastern Oregon

      Bohn, C. C.; Buckhouse, J. C. (Society for Range Management, 1985-07-01)
      Infiltration, sediment production, penetrometer penetrability and bulk density were measured on control/treatment paired plots of several grazing schemes in a riparian zone of northeastern Oregon. Treatments were in effect over a period of 5 years. Rest-rotation favored the hydrologic parameters measured, while deferred rotation and season-long did little to enhance, and sometimes hindered, hydrologic expression. Late-season grazing in September demonstrated a positive hydrologic response, whereas late-season grazing in October was negative-probably due to the onset of fall rains and a change in soil moisture conditions.
    • Temperature and Water Stress Effects on Growth of Tropical Grasses

      Bade, D. H.; Conrad, B. E.; Holt, E. C. (Society for Range Management, 1985-07-01)
      Coastal bermudagrass (Cynodon dactylon (L.) Pers.) and Kleingrass "75" (Panicum coloratum L.) were grown under controlled environments to evaluate the effects of high growth temperatures and water stress on forage growth. Plants were grown under a controlled environment with 14/10 hour day/night temperatures of 30/20, 35/25, and 40/30 degrees C; 2 water regimes; and 3 stages or ages of regrowth at harvest. High growth temperatures significantly (P<0.05) increased dry matter yield and accelerated tiller number and the maturation rate of the plants. Significant (P<0.05) increases in leaf area, weight per tiller, and plant height were observed as growth temperatures were increased. Reduction of number of tillers per pot due to water stress reduced dry matter yields approximately 38%. The percent leaf was greater for the water-stressed plants than for the well-watered plants, but the leaf area per plant was less due to reduction of growth and delayed maturation. Dry matter yield of water-stressed plants grown under higher temperatures increased more than corresponding well-watered plants as a result of increased rate of stem elongation and leaf development. Though water-stressed plants were shorter and had less leaf area than well-watered plants, the relative increase in both height and leaf area at higher temperatures of stressed plants was greater than well-watered plants. Apparently supraoptimal temperature (40 degrees C) does not have a negative effect on yield in the presence or absence of moisture stress.
    • The Animal-Unit and Animal-Unit-Equivalent Concepts in Range Science

      Scarnecchia, D. L. (Society for Range Management, 1985-07-01)
      The terms animal-unit and animal-unit-equivalent have evolved as a means of expressing different kinds and classes of livestock in a common form. This paper discusses the evolution of the concepts, analyzes their conceptual boundaries, and discusses their use in the analysis of range livestock systems. Recent efforts to modify these concepts to develop livestock species substitution ratios for specific ranges are discussed. For greater usefulness in describing range livestock systems, animal-unit-equivalents should be calculated based only on animal-related factors. Also, the animal-unit-equivalent concept should not be redefined in the calculation of pasture-specific substitution ratios.
    • The Use of Supplement Blocks for Sheep Grazing Dry, Annual Pastures in California

      DePeters, E. J.; Dally, M. R.; Alwash, A. A.; Therkelsen-Tucker, P. (Society for Range Management, 1985-07-01)
      The objective of this study was to evaluate the use of supplement blocks on body weight change, blood parameters, and lambing performance of ewes grazing dry, annual grasses during the summer prior to and during breeding. Two experiments were conducted in successive years to compare performance of unsupplemented control (C) and supplemented (S) Targhee ewes. In the first season, yearling ewes were used while aged ewes (2 or 4 years) were used during the second season. During the first year (1980), supplemented ewes lost less body weight during the dry grazing season than C ewes. However, no lambing performance difference was found between C and S groups. During the second year (1981), supplemented ewes maintained their body weight over the summer while C ewes lost weight. In addition, lambing performance (multiple births) was higher for S than C ewes. Supplementation of ewes with blocks containing molasses, urea, protein, and minerals required little labor input. However, based on lambing performance, it is unlikely that supplementation would be economically profitable under the range conditions utilized in these trials.