• A Dynamic Approach to Grazing Management Terminology

      Scarnecchia, D. L.; Kothmann, M. M. (Society for Range Management, 1982-03-01)
      Expressions such as stocking density, stocking rate, grazing pressure, herbage allowance, grazing intensity and stocking pressure have long been used to describe animal-pasture systems. These expressions describe relationships among the basic variables of animal demand, forage quantity, pasture area, and grazing duration. Our objective was to develop a dynamic, mathematical framework of expressions summarizing all of the meaningful relationships among these variables. The resulting expressions have dimensional validity, and are useful in describing dynamic animal-pasture systems. The expressions should also prove useful in future efforts to model these systems.
    • Cattle Diets in the Blue Mountains of Oregon II. Forests

      Holechek, J. L.; Vavra, M.; Skovlin, J.; Krueger, W. C. (Society for Range Management, 1982-03-01)
      Esophageally fistulated cows were used on forested range in northeastern Oregon to collect diet samples which were then analyzed by the microhistological technique. Grasses, forbs, and shrubs averaged 61, 16, and 23% of the diet, respectively. Composition of diets differed among years and with seasonal advance. Idaho fescue and elk sedge were the most important forage species consumed. Forbs were used heavily in the early part of the grazing season before maturation. Browse comprised as much as 47% of the diet when green grass was unavailable. Cattle were opportunistic grazers and did not limit their selection to grass species. On forested ranges cattle diets varied among grazing periods within each year as well as among years.
    • Changes in the Yield of Forage Following the Use of Herbicides to Control Aspen Poplar

      Bowes, G. G. (Society for Range Management, 1982-03-01)
      Yields of forage were measured 3 to 5 years after the use of 2,4-D, 2,4-D + 2,4,5-T, and picloram + 2,4-D applied at brush control rates. The yield of bromegrass and alfalfa on the herbicide treated areas was either reduced or remained unchanged. This occurred because alfalfa can not tolerate the high herbicide rates required for brush control. On an area which never received a herbicide treatment, alfalfa was unable to compete with invading aspen poplar and prickly rose. Ranchers should use herbicides to prevent secondary succession from grasslands to the aspen poplar vegetation type which has a low amount of forage available for cattle. Arguments are presented for including alfalfa in a seeding program when a mixture of 2,4-D + picloram is used for brush control but not when a mixture of 2,4-D + 2,4,5-T is used.
    • Concentration of Monoterpenoids in the Rumen Ingesta of Wild Mule Deer

      Cluff, L. K.; Welch, B. L.; Pederson, J. C.; Brotherson, J. D. (Society for Range Management, 1982-03-01)
      Forage from a sagebrush-dominated winter range and rumen ingesta from mule deer wintering on this range were analyzed for monoterpenoids. The average monoterpenoid level of the rumen ingesta was 0.3%, compared with an average of 1.64% expected from the proportion of monoterpenoid-containing plants in the diet. This 80% reduction between the monoterpenoid level from the rumen compared to the level expected from the ingested forage was highly significant (p<.01). The exact method in which the monoterpenoids are lost from the ingesta was not determined, but evidence from other studies suggests that monoterpenoids may be lost from ingested forage as early as the mastication process. The amount of monoterpenoids found in the rumen ingesta at the time of sampling does not appear to be high enough to interfere with microbial activity. This loss of monoterpenoids may explain the conflict between in vitro evidence that big sagebrush monoterpenoids inhibit rumen microorganisms and digestive trials which show that big sagebrush is a highly digestible winter forage.
    • Cow-Calf Response to Stocking Rates, Grazing Systems, and Winter Supplementation at the Texas Experimental Ranch

      Heitschmidt, R. K.; Kothmann, M. M.; Rawlins, W. J. (Society for Range Management, 1982-03-01)
      Cow-calf performance from 1960 through 1978 was contrasted between three grazing treatments at the Texas Experimental Ranch. Grazing treatments were yearlong continuous stocked at annual rates averaging 5.1 and 7.6 ha/cow and a 4-pasture, 3-herd deferred rotation system stocked at an annual rate averaging 7.2 ha/cow. Averaged across three weighing periods, cows in the deferred rotation treatment averaged 447 kg while weight of cows in the heavily and moderately stocked continuous treatments averaged 427 and 438 kg, respectively. Calf weaning weights averaged 204, 212, and 217 kg for the heavy continuous, moderate continuous, and Merrill rotation treatments, respectively. Production-/cow averaged 182, 189, and 202 kg while production/ha averaged 35.9, 25.2, and 27.8 kg, respectively, for the heavy continuous, moderate continuous, and deferred rotation treatments. Cows fed winter supplement were significantly heavier in early spring and summer than nonsupplemented cows with no significant differences in weights by late summer. Supplemented cows weaned calves averaging 214 kg as compared to 208 kg for calves weaned from nonsupplemented cows. Winter supplementation significantly increased production in the heavily stocked treatment but not in either of the moderately stocked treatments. Numerous statistically significant interactions accompanied the significant main effects, and the biological significance of each was examined.
    • Brownseed Paspalum Response to Season of Burning

      Scifres, C. J.; Duncan, K. W. (Society for Range Management, 1982-03-01)
      Season of burning as related to plant phenology, maximum temperatures achieved, and soil water content rather than duration of heat exposure (5, 15 or 30 seconds) apparently regulated fire-induced mortality of brownseed paspalum. Burning or top removal by clipping to ground line during the summer caused greatest mortality of brownseed paspalum and reduced herbage volume of surviving plants, whereas burning in early or mid-spring resulted in favorable growth responses. Fall burning was less damaging than summer burning but caused greater mortality of brownseed paspalum than did burning in the spring. Regrowth of brownseed paspalum after spring burning was equivalent to that following top removal by clipping during the same season. However, responses to summer or fall burning indicated that heat-induced damage (and/or perhaps subsequent winter kill following fall burns) occurred in addition to the effects of simple top removal.
    • Destructive and Potentially Destructive Insects of Snakeweed in Western Texas and Eastern New Mexico and a Dioristic Model of Their Biotic Interactions

      Wangberg, J. K. (Society for Range Management, 1982-03-01)
      The relationships of the principal destructive and potentially destructive insects associated with Xanthocephalum microcephalum (DC) Shinners (threadleaf snakeweed) and Xanthocephalum sarothrae (Pursh) Shinners (broom snakeweed) have been identified and depicted with a dioristic model. Every region of the host plant is utilized by insects in one or more of the following feeding categories: defoliators, fluid feeders, borers, and gall-formers. Roots, stems, leaves, flowers, and fruit each have their own complement of insect associates. A system analysis reveals a complex picture of insect-host plant interactions as well as potential insect-insect interactions. The roles that these insects play in the natural biological control of threadleaf and broom snakeweed are poorly understood but the general information portrayed in the model of their interactions will help future workers to determine the most productive avenues of research.
    • Grass Response Following Thinning of Broom Snakeweed

      McDaniel, K. C.; Pieper, R. D.; Donart, G. B. (Society for Range Management, 1982-03-01)
      Complete removal of broom snakeweed resulted in perennial grass production 833% of that on untreated rangeland after one growing season, and 712% and 300% the second and third year, on a pasture heavily grazed and in poor range condition. On a moderately grazed pasture in good range condition, grass standing crop increased 42% the first year, 81% the second, and 25% the third compared to untreated rangeland. Perennial grass production on the heavily grazed pasture was far below that on the moderately grazed pasture at the start of the study (40 vs 454 kg/ha). After 3 years, with complete broom snakeweed removal and no grazing, perennial grass production was comparable on the pastures once heavily and moderately grazed (1014 vs 939 kg/ha, respectively).
    • Factors Influencing Bitterweed Seed Germination

      Whisenant, S. G.; Ueckert, D. N. (Society for Range Management, 1982-03-01)
      Bitterweed seed germination exceeded 90% at constant temperatures between 20 degrees and 25 degrees C and more than 65% between 15 degrees and 30 degrees C in a controlled environment chamber. Seeds germinated equally well in light and dark conditions. Germination percentages of seeds in aqueous media with a pH range of 5 to 9 were significantly different, but the range of germination (91 to 97%) probably is not sufficient to affect distribution. However, a decrease in water availability significantly decreased bitterweed seed germination. Viability of bitterweed seed did not change significantly after 39 months dry storage at room temperature, but was significantly reduced at 47 months.
    • Food Resource Partitioning by Sympatric Ungulates on Great Basin Rangeland

      Hanley, T. A.; Hanley, K. A. (Society for Range Management, 1982-03-01)
      The usefulness of a conceptual framework for understanding food selection by ungulates, based on four morphological parameters (body size, type of digestive system, rumino-reticular volume to body weight ratio, and mouth size), was tested by applying discriminant analysis to 194 monthly diet determinations based on microhistological fecal analysis for five sympatric species of ungulates in northeastern California and northwestern Nevada. In each season, the group means were located in the hypothesized order along the axis described by the first discriminant function: feral horse, domestic cow, domestic sheep, pronghorn, mule deer. Horse and cow diets consisted primarily of grasses. Pronghorn and mule deer diets consisted primarily of browse. Sheep diets were intermediate. Four browses (Artemisia spp., Cercocarpus ledifolius, Purshia tridentata, and Juniperus occidentalis) were selected as the most useful species for discriminating between animal species. The data and analyses support the hypothesized food selection framework.
    • Fluoride in Thermal Spring Water and in Plants of Nevada and Its Relationship to Fluorosis in Animals

      Kubota, J.; Naphan, E. A.; Oberly, G. H. (Society for Range Management, 1982-03-01)
      Fluoride concentrations in water from selected thermal springs and in plants were determined to evaluate their role as sources of F- for grazing animals in Nevada. The F- concentration in water varied with thermal spring sources and ranged from about 2 to 17 ppm. F- concentration in plants ranged from about 0.1 to over 220 ppm, depending upon species of plants and the soil on which the plants were grown. The F- concentration in plants from any given thermal spring location was not uniformly high, but together with F- concentration of the water, appears to contribute to possible cases of fluorosis in cattle. Although small area-wise the spring waters and the area they flow over are important to grazing animals, because they provide drinking water and have lush forage.
    • Foliage Mortality of Mountain Big Sagebrush in Southwestern Idaho during the Winter of 1976-77

      Hanson, C. L.; Johnson, C. W.; Wight, J. R. (Society for Range Management, 1982-03-01)
      Mountain big sagebrush (Artemisia tridentata subsp. vaseyana) in southwest Idaho suffered extensive overwinter foliage mortality during 1976-77 where the normally deep snow cover was lacking. Mortality was 75 to 100% in areas where snow usually covers dense stands of sagebrush; however, winterkill was slight in areas of usually shallow snow cover. Winter-induced physiologic drought caused by frozen soils, low soil water content, and above average air temperature was the apparent cause of sagebrush foliage mortality.
    • In Vitro Digestion—Sources of Within- and Between-Trial Variability

      Milchunas, D. G.; Baker, D. L. (Society for Range Management, 1982-03-01)
      Procedures for, and conditions during, inoculum collection and preparation, digestion, and residue recovery stages of the in vitro digestion technique were investigated to determine sources of within- and between-trial variability in digestion coefficients for forages of different chemical composition. Digestion coefficients differed significantly among inoculum preparation times of 1, 2, and 4 hours and for a decline in rumen fluid temperature to 29° in transport. These differences were not uniform across forage species and did not correlate with forage digestibility. Digestion coefficients differed significantly among inoculums prepared from fibrous deer rumen fluids that were strained only, strained and layered, and blended in a Waring blender and filtered through glass wool but did not differ between strained-layered and blended filtered inoculums of non-fibrous rumen fluid from a fistulated cow. Forage in vitro digestion in the absence of microbial activity (by solubility alone) indicated that forages having more soluble components were least affected by inoculums of different microbial activities, suggesting that between-trial differences be adjusted by a solubility, rather than a digestibility, factor. Inoculum nitrogen concentration did not correspond to between-trial differences in forage digestibility. Size of test tube, but not centrifugation versus filtration method of residue preparation, significantly affected digestion coefficients. However, because the standard large tube size cannot be centrifuged, the two methods of residue recovery would not be comparable unless the products of digestion were transferred from large tubes to centrifuge tubes. The end products of digestion must be stored under refrigeration if filtering proceeds for extended periods of time.
    • Responses of Crested Wheatgrass and Russian Wildrye to Water Stress and Defoliation

      Mohammad, N.; Dwyer, D. D.; Busby, F. E. (Society for Range Management, 1982-03-01)
      Crested wheatgrass (Agropyron desertorum, Fisch Schult) and Russian wildrye (Elymus junceus, Fisch) plants were subjected to three levels of water stress (13, 2.6, and 1.8% soil moisture), in interaction with 4 defoliation levels (0, 40, 60, and 80% defoliation). Plants were clipped biweekly using the height-weight ratio method to determine the assigned defoliation level and leaf water potential $(\Psi _{1})$ was measured by pressure bomb. Following the final clipping at ground level a 40-day recovery period was allowed while maintaining plants at field capacity (13% soil moisture). Leaf water potential measurements showed significant differences between species, among three water stress levels, and within four defoliation levels. Water stress and defoliation levels significantly affected foliage yield, root biomass, and plant recovery. Heavy defoliation (80%) resulted in a 100% death loss for both species at wilting point (1.8% soil moisture). Light defoliated (40% at field capacity) produced more total dry matter than undefoliated plants maintained at field capacity or wilting point. Maximum root biomass was found in undefoliated plants of crested wheatgrass grown at field capacity. Significant differences in root production were also found among water stress and defoliation treatments. No plant recovery occurred among plants maintained at wilting point and defoliated at 80%. However, plants defoliated at 40 and 60% under 13 and 2.6% soil moisture exhibited considerable regrowth. In general crested wheatgrass out-yielded Russian wildrye in every treatment and was more resistant to defoliation and water stress.
    • Sample Preparation Techniques for Microhistological Analysis

      Holechek, J. L. (Society for Range Management, 1982-03-01)
      A study was conducted to determine the influence of sample preparation procedures on the ratio of identifiable to nonidentifiable fragments in diet samples analyzed by microhistological analysis. The number of identifiable fragments on slides was significantly higher when samples were soaked in either bleach or sodium hydroxide in conjunction with use of Hertwig's clearing solution compared to the control, which involved the use of only Hertwig's clearing solution. The percentages by weight of grasses, forbs, and shrubs in two prepared diet samples were more accurately estimated when either sodium hydroxide or bleach was applied in comparison with the control. However, some plant species or plant parts may be destroyed by bleach or sodium hydroxide. Therefore, diet materials should also be examined through standard procedures before the decision is made to apply one of these treatments.
    • Vegetative Response to Clearcutting and Chopping in a North Florida Flatwoods Forest

      Moore, W. H.; Swindel, B. F.; Terry, W. S. (Society for Range Management, 1982-03-01)
      Selected naturally regenerated flatwoods forests were clearcut and chopped in preparing a large, long-term study of the effects of several multiple-use management practices on forest vegetation and wildlife. Early effects of clearcutting and chopping on understory vegetation are reported here. Clearcutting and chopping reduced woody understory coverage from 66 to 18% of surface area. Common gallberry and saw-palmetto were reduced by 75 and 89%, respectively. Herbaceous species frequency was increased: Panicums by over 3,000%; bluestems by 173%; grasslikes by over 2,000%; and forbs by 308%. Graphical analyses show an increase in herbaceous species diversity as a result of mechanical site disturbance. Comparing these graphs with those reported on the effects of prescribed burning suggests that the collective vegetative response to mechanical site disturbance is qualitatively similar to the response to fire. Quantitatively the response to mechanical disturbance is more pronounced.
    • Infiltration and Sediment Production on a Deep Hardland Range Site in North Central Texas

      Brock, J. H.; Blackburn, W. H.; Haas, R. H. (Society for Range Management, 1982-03-01)
      Greatest infiltration rate and lowest sediment production occurred in the honey mesquite canopy zone. Infiltration on shortgrass interspace areas was about one-half of the canopy zone rate. Terminal infiltration rates within the canopy zone and shortgrass interspace areas were affected little by brush control treatments. Infiltration rate improvement due to treatment occurred primarily in the midgrass interspace areas. Water-stable aggregates and the interaction of soil aggregate stability with the amount of bare ground were the dominant factors controlling infiltration. Sediment production on the shortgrass interspace was double that of the canopy zone or midgrass interspace areas. Low rate of sediment production on the midgrass interspace areas occurred on areas aerially sprayed or root plowed 3 years earlier. Sediment production was controlled primarily by an interaction of soil organic matter and amount of above-ground biomass or grass cover.
    • Level Benches for Forage Production in the Northern Plains

      Rauzi, F.; Landers, L. (Society for Range Management, 1982-03-01)
      Level benches 4- and 8-m-wide were constructed at the Wyoming Agriculture Research and Extension Center, Gillette, Wyoming 1970. Replicated benches and controls were seeded with Ladak alfalfa, Nordan crested wheatgrass, intermediate wheatgrass, and mixtures of Ladak alfalfa and crested and intermediate wheatgrass. Phosphorus (134 kg P2O5/ha) was applied to all benches and to the control. Ammonium nitrate was applied at 90 kg N/ha in May 1972 and 1977, and at 45 kg/ha in April 1974 to the benches and control, except those seeded to alfalfa alone. Snow trapped in the benches was not uniformly distributed because of the benches' northeast orientation. However, more soil water was available for plant use. The deep-rooted alfalfa was compatible with the shallow-rooted crested wheatgrass and seemed the best combination tested for forage production on level benches in northeast Wyoming. Construction of level benches is a practice that can ensure a dependable source of quality feed by trapping and holding snow for onsite use. Forage yields from the henches and the controls varied with years. During the 8 years (1970-1978) on the 4- and 8-m-wide benches, alfalfa yields averaged 3,420 and 3,813 kg/ha, respectively, and alfalfa and crested wheatgrass mixture averaged 3,560 and 3,855 kg/ha, respectively. Crested wheatgrass alone on 4- and 8-m-wide benches averaged 2,569 and 2,456 kg/ha, respectively, and on the 4- and 8-m-wide control averaged 2,382 and 2,786 kg/ha, respectively. Intermediate wheatgrass on the 4- and 8-m-wide benches averaged 2,329 and 3,425 kg/ha, respectively, and on the 4- and 8-m-wide controls averaged 2,565 and 3,262 kg/ha, respectively. Grass yields did not differ significantly when grasses were grown alone on the benches or on the control.
    • Potassium Content of Three Grass Species during Winter

      Hinnant, R. T.; Kothmann, M. M. (Society for Range Management, 1982-03-01)
      The potassium content of little bluestem (Schizachrium scoparium (Michx.) Nash), kleingrass (Panicum coloratum L.), and brownseed paspalum (Paspalum plicatulum Michx.) declined following plant senescence and frost. The potassium content of herbage of little bluestem and brownseed paspalum reached levels below the requirements of cattle by February during two winters. Kleingrass leaves retained green tissue the first winter yielding higher potassium levels. Little bluestem had reached senescence and had low levels of potassium by November. Herbage of the three species was also subjected to soaking treatments to simulate frost damage and quantify losses due to leaching. Potassium levels declined with soaking in freeze damaged herbage as time of exposure increased. Soaking treatments did not significantly affect the potassium content of fresh live herbage.