• A comparison of two furrow opener-depth control assemblies for seeding forage grasses

      Lawrence, T.; Dyck, F. B. (Society for Range Management, 1990-01-01)
      Seed from 45 strains of grass were sown with 2 drills fitted with different furrow openers and depth control devices. Standard (34-cm diameter) double disk openers (Kirchman (Lilliston Melroe)) fitted with depth control bands 2 cm wide and 5 cm smaller in diameter than the disk were used to seed 1 trial at a seeding depth of 2.5 cm. This seeding was compared to forage crop stands obtained from a drill fitted with an experimental opener using 2 disks of unequal diameter, the larger (38 cm diameter) running vertical and the smaller (28 cm diameter) angled at 7 degrees. The center for mounting the small disk is 5 cm below and 2.5 cm behind the large disk, thus the bottoms of the disks are on the same horizontal plane. Seeding depths of 2.5 cm and 6.25 cm were accomplished by an adjustable rubber-tired depth gauge wheel assembled beside the large disk. At the 2.5 cm depth of seeding, the large-small disk opener assembly resulted in superior forage establishment compared to that obtained with the standard double disk assembly. Comparing either opener-depth control assembly set to seed at 2.5 cm depth with the large-small disk assembly set to seed at 6.25 cm depth confirmed the value of shallow seeding of forage crops to overcome establishment problems.
    • Clipping and long-term grazing effects on biomass and carbohydrate reserves of Indian ricegrass

      Orodho, A. B.; Trlica, M. J. (Society for Range Management, 1990-01-01)
      Long-term heavy grazing had little effect on root and crown biomass of Indian ricegrass (Oryzopsis hymenoides [Roem. and Schult.] Ricker), nor did it significantly affect the total nonstructural carbohydrate (TNC) reserve levels or the seasonal cycle of reserves in this grass. Fifty years of protection from livestock use had not resulted in ecotypic differentiation in Indian ricegrass for these variables. Clipping reduced crown biomass more than root biomass and removal of 90% of the aboveground biomass resulted in more than a 50% reduction in crown biomass and reserve carbohydrate pool. Two commercial strains of Indian ricegrass ('Nezpar' and 'Paloma') were compared with native Chaco Canyon strains in a uniform garden study. The Nezpar strain was superior to Paloma and the Chaco Canyon strains in production of crown biomass and TNC reserves at the more mesic garden site. The native strains from the more arid Chaco Canyon site were superior to both cultivated strains in production of roots. The native Chaco Canyon strains were little affected by clipping and have promising genetic potential for tolerance of drought and heavy grazing.
    • Comparative photosynthetic responses of big bluestem to clipping versus grazing

      Wallace, L. L. (Society for Range Management, 1990-01-01)
      The gas exchange responses of big bluestem (Andropogon gerardii) were followed after defoliation by either cattle grazing or clipping and compared with the response of nondefoliated (control) plants. Grazed plants had significantly higher rates of photosynthesis than either clipped or control plants. The photosynthesis/transpiration ratio as well as stomatal sensitivity to humidity indicate that leaves of grazed plants may have developed in a higher light and lower moisture environment than that of their clipped counterparts. Although the experimental design could not preclude any indirect effects of animal activity (saliva, waste products, or trampling) on the grazed plants, the microenvironmental differences caused by grazing may be crucial in determining the responses of grasses to clipping versus grazing.
    • Comparison of actual and predicted blue oak age structures

      McClaran, M. P.; Bartolome, J. W. (Society for Range Management, 1990-01-01)
      There is increasing interest in understanding the role of management on the current lack of blue oak (Quercus douglasii H. & A.) recruitment on California foothill rangelands. Age structure analysis has been suggested to relate when and how much recruitment occurred under past management as an indication of current management effects on recruitment. Previous estimates of blue oak age structure were based on unquantified correlations between age and diameter. Using regression analysis we found that diameter at breast height (DBH) accounted for 42-71% of the variation in tree age at 2 sites. Actual age structures were significantly different than age structures predicted from all regression equations at both sites. We suggest that the use of age structures to infer the role of management on blue oak population dynamics requires direct age measurement.
    • Comparison of the copper and molybdenum status of yearling steers grazing reclaimed mined-land and native range

      Karn, J. F.; Hofmann, L. (Society for Range Management, 1990-01-01)
      Spoil material replaced after strip mining for lignite coal may differ from the original top soil with respect to concentrations of copper (Cu) and molybdenum (Mo), consequently levels of these elements may be affected in plants grown on this soil. The objective of the study was to compare the Cu and Mo status of yearling steers grazing mined-land and native range forage to determine whether mined-land grazed steers were more prone to molybdenosis and/or Cu deficiency. Vegetation samples were collected from both mined-land and native range pastures. Copper was marginal and Mo was slightly high, for beef cattle, in forage obtained from both study sites. Blood serum and liver biopsy samples were taken from yearling steers at the initiation and termination of grazing on reclaimed mined-land and native range in 1978, 1979, 1982, and 1983. For the 4 years, there was no significant difference between forage sources with respect to Cu and Mo levels in the liver or Mo levels in the serum. However, serum Cu was slightly (P<.10) lower in steers grazing on mined-land. Liver Cu levels were marginal in steers grazing on either mined-land or native range. Initial liver Mo levels were slightly above normal but did not increase to levels expected if animals were consuming a diet excessively high in Mo. No symptoms of Cu deficiency or molybdenosis were observed during the course of the study. However, marginal serum, liver and forage Cu levels measured suggest that central North Dakota ranchers should be alert to the possibility of a Cu deficiency, whether cattle are grazing reclaimed mined-land or native range.
    • Control of honey mesquite with herbicides: influence of plant height

      Jacoby, P. W.; Meadors, C. H.; Ansley, R. J. (Society for Range Management, 1990-01-01)
      Stands of honey mesquite (Prosopis glandulosa var. glandulosa) were treated with aerially applied herbicides at 16 locations in western and northwestern Texas over an 8-year period to determine influence of plant height on herbicide efficacy. Plant height was not found to significantly (P<0.05) influence effectiveness of a particular herbicide, but taller plants were found consistently to be more resistant. No basis was found for delaying control of honey mesquite with herbicides until plants reach a particular height.
    • Control of honey mesquite with herbicides: influence of stem number

      Jacoby, P. W.; Ansley, R. J.; Meadors, C. H.; Cuomo, C. J. (Society for Range Management, 1990-01-01)
      Following aerial application of herbicides, stands of honey mesquite (Prosopis glandulosa var. glandulosa) were evaluated to determine the influence of individual plant stem number on herbicide efficacy. A highly significant (P<0.01) relationship was found between stem number and plant mortality, with herbicide resistance increasing sharply in plants with greatest numbers of stems. This relationship was consistent among all herbicides and plant heights, which suggests that stem number may be useful in selecting the type of control method employed on specific sites.
    • Creosotebush control and forage production in the Chihuahuan and Sonoran deserts

      Morton, H. L.; Ibarra-F, F. A.; Martin-R, M. H.; Cox, J. R. (Society for Range Management, 1990-01-01)
      Creosotebush (Larrea tridentata [Sesse & Moc. ex DC.] Cov) and other shrubs have spread into semidesert grasslands of the southwestern United States and northern Mexico; and as creosotebush increases, perennial grasses decrease. This study evaluated 3 rates of tebuthiuron and 4 mechanical treatments in 1981 and 1982 for creosotebush control at 4 locations, 3 in Chihuahua, Mexico, and 1 in Arizona, U.S.A., and compared forage production after treatment with untreated checks. Creosotebush mortalities averaged across locations and years were 75, 87, 93, 3, 33, 68, and 68% for the 0.5, 1.0, and 1.5 kg ai/ha tebuthiuron (N-(5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl]-N,N′-dimethylurea), land imprinting, 2-way railing, disk plowing, and disk plowing with contour furrowing treatments, respectively. Forage production averaged across locations and years was 529, 524, 606, 303, 344, 290, 330, and 302 kg/ha for the 0.5, 1.0, and 1.5 kg ai/ha tebuthiuron, land imprinting, 2-way railing, disk plowing, disk plowing with furrowing, and untreated check treatments, respectively. Precipitation was below long-term means at all Chihuahuan locations in 1983, and forage production was significantly greater on most treated plots where brush was controlled than on untreated checks. At the Arizona location precipitation was above the long-term mean in 1983 and all plots treated in 1981, except the disk plowing and disk plowing with furrowing which destroyed perennial grasses, produced significantly more grass forage than the untreated checks. Precipitation was above the long-term means at all locations in 1984 and about half of the plots treated with tebuthiuron produced significantly more forage than the untreated checks but not any mechanically treated plots. When treatments reduced shrub density and remnants of native forage grasses were present, forage production increased in both wet and dry years.
    • Distribution of nitrogen fractions in grazed and ungrazed fescue grassland Ah horizons

      Dormaaar, J. F.; Smoliak, S.; Willms, W. D. (Society for Range Management, 1990-01-01)
      Grazing affects the plant ecology and adds excreta, thereby influencing soil N relationships. Consequently, total N, mineralizable N, exchangeable N, hydrolyzable N, and urease activity were assessed at the Agriculture Canada Research Substation, Stavely, Alberta, in the Ah horizons on rough fescue (Festuca scabrella Torr.) grasslands stocked at either light (0.8 ha/AUM) or very heavy (0.2 ha/AUM) fixed rates for 38 years and in exclosures located within each field for an equal period of time. Even though total N expressed as t/ha per Ah horizon remained the same, changes in various N fractions were nevertheless evident. Grazing resulted in more NH4 +/- N and NO3-N in both fields at the time of sampling and each was greater at the higher stocking rate. Although soil N was less mineralizable, it was more acid-hydrolyzable at the higher stocking rate. Urease activity also increased. The effect on soil N characteristics of increased excreta loads is complex and still not well understood.
    • Ecology of curlleaf mahogany in western and central Nevada: community and population structure

      Schultz, B. W.; Tueller, P. T.; Tausch, R. J. (Society for Range Management, 1990-01-01)
      Curlleaf mahogany is an important browse species for mule deer in the mountain brush zone of the Intermountain West. Past research on increasing browse availability of curlleaf mahogany has been inconclusive. This appeared to be directly related to limited understanding of community and population structure and dynamics. To obtain information on the community and population structure of curlleaf mahogany we sampled 25, 30 × 30-m macroplots in western and central Nevada. Data on mahogany density, maturity class structure, size, ages, and population growth rates were obtained. Understory cover and composition and percent rock, bare ground, and litter were also recorded. Mahogany density in central Nevada was one-half that in western Nevada, but mahogany cover and total cover were significantly (P lesser than or equal to 0.05) greater. Maturity class distribution in central Nevada was heavily skewed towards large mature mahogany, suggesting an older population dominated by fewer large individuals. This dominance resulted in significantly (P lesser than or equal to 0.05) lower population and relative growth rates and the necessity of canopy gaps for the survival of young mahogany. Range improvement of mature mahogany stands dominated by large individuals will require the removal of the mature and over mature individuals so that young forage producing plants are released from intraspecific competition.
    • Effects of continuous grazing on habitat and density of ground-foraging birds in south Texas

      Baker, D. L.; Guthery, F. S. (Society for Range Management, 1990-01-01)
      We analyzed the response of the key habitat features and ground-foraging birds to 2 intensities of continuous grazing on sandy loam and clay soils in the Texas Coastal Bend during 1984-1985. Heavy continuous grazing increased the dispersion but not necessarily the availability of bare ground in comparison with moderate continuous grazing. Responses of habitat features (structure of ground cover, key food plants) depended on soil type. Seasonal densities of eastern meadowlarks (Sturnella magna) were higher on clay than on sandy loam soils and higher under moderate than under heavy grazing. Mourning doves (Zenaida macroura) were more abundant on sandy loams than on clays and more abundant under heavy than under moderate grazing. Northern bobwhite (Colinus virginianus) abundance was uniformly low, regardless of grazing intensity and soil type.
    • Effects of manual application method on application time, thoroughness, and tebuthiuron outlays

      Van Pelt, N. S.; West, N. E. (Society for Range Management, 1990-01-01)
      Small-plot trials of effective herbicides for manual woody-weed treatments should be validated on large tracts where rapidity, thoroughness, and efficiency of application are integral to operational-scale recommendations. A 7.9 hectare woodland chaining in Utah, with 248 Juniperus osteosperma Torr. (Little) and Pinus monophylla Torr. & Frem. saplings per ha, was divided into nine 25-m by 350-m strips for timed tebuthiuron (N-[5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl]-N,N′-dimethylurea) manual application trials in fall 1986 and summer 1987. About 1 ha was treated per hour, and 6 to 15% of the trees were missed. Three application methods differed in total and aggregate time outlays, accuracy, and tediousness, but were highly similar in formulated tebuthiuron expenditures of 1.5 to 2.0 kg/ha (0.21 to 0.28 kg/ha tebuthiuron a.i.). Time expenditures were moderately predictable (r2=0.62) from treated tree density and mean tree height, whereas percent trees missed was unrelated to density or method. Placing herbicide particles at the stem base and basing dosages on stem height are preferable to dripline applications and crown-volume based dosage estimations.
    • Estimates of critical thermal environments for mule deer

      Parker, K. L.; Gillingham, M. P. (Society for Range Management, 1990-01-01)
      Mule deer (Odocoileus hemionus hemionus) can be thermally stressed under a wide range of ambient conditions. We developed a model that provides examples of the combinations of wind, solar radiation, and air temperature that may result in thermally critical environments for standing, full-fed adult mule deer during winter in snow-covered and snow-free, open habitats, and in meadows in summer. Critical thermal combinations of environmental variables are shown as 3-dimensional surfaces and tables. Animal size, age, pelage characteristics, and ground cover (height and albedo) further affect the energy costs for thermoregulation by mule deer. The need for habitat managers to consider the provision of thermal cover to reduce heat or cold stress in mule deer depends on the combinations of environmental variables in a particular habitat and geographic location. Implications, limitations, and management considerations of our estimates are discussed.
    • Herbage production of Mediterranean grassland under seasonal and yearlong grazing systems

      Gutman, M.; Seligman, N. G.; Noy-Meir, I. (Society for Range Management, 1990-01-01)
      Data from 2 consecutive grazing experiments conducted over 7 years on a Mediterranean type grassland were used to calculate forage consumption by herds of beef cattle maintained at different stocking rates and in different grazing systems. In the first experiment the animals were on the experimental range for 8 months of the year; in the second, grazing was yearlong. Total production of herbage mass was estimated from these data and from the residual litter in the paddocks at the end of the dry season. Production of dry herbage mass varied between 2,600 and 3,800 kg/ha, with a mean and SD of 3,060 +/- 300 kg/ha. While variation between years was relatively small but significant (P<.01), the effect of stocking rate or grazing system (seasonal, yearlong) was smaller and not significant. It is concluded that the attained level of herbage production of Mediterranean grassland on relatively shallow basaltic protogrumosols is not sensitive to total precipitation over a very wide range or to grazing system. It may be dependent on the availability of nutrients, especially nitrogen, and the seasonal distribution pattern of available soil moisture in a restricted rooting zone.
    • Herbage production-forest overstory relationships in two Arizona ponderosa pine forests

      Bojorquez Tapia, L. A.; Ffolliott, P. F.; Guertin, D. P. (Society for Range Management, 1990-01-01)
      Utilizing source data for annual herbage production which had been obtained through repeated measurements, though not necessarily taken in each year, in 2 Arizona ponderosa pine (Pinus ponderosa) forests from 1959 to 1980, 18 herbage production-forest overstory regression equations were developed and statistically analyzed. In addition to logarithmic and exponential transformations, a hyperbolic transformation met the specific acceptance criteria. Soils were stratified for some herbage components to improve sampling efficiencies. The regression equations presented are considered more useful for long-term planning purposes than for predicting the level of herbage production in a particular year.
    • Nitrogen accumulation and acetylene reduction activity of native lupines on disturbed mountain sites in Colorado

      Kenny, S. T.; Cuany, R. L. (Society for Range Management, 1990-01-01)
      Lupines are pioneering plants in many disturbed mountain habitats in Colorado. The purpose of this work was to determine if Lupinus argenteus, L. caudatus, and L. alpestris could be useful revegetation plants in a reclamation program. Paired soil samples from 33 disturbed sites supporting native lupines were used to determine if lupines increased the nitrogen content of the soil. Soil samples collected 10 cm from lupine tap roots averaged 13.8 mg kg-1 more exchangeable ammonium and 2.7 mg kg-1 more nitrate than soil samples collected 3 m from lupine plants. Field measured acetylene reduction rates of detached lupine nodules averaged 10.0 micromol ethylene g-1 nodule dry weight h-1 for L. argenteus and 17.3 micromol ethylene g-1 nodule dry weight h-1 for L. alpestris. Soil adjacent to lupines had higher levels of inorganic nitrogen than soils 3 m from lupine plants and lupines had the ability for biological nitrogen fixation as shown by the acetylene reduction assay, suggesting that native lupines are potentially useful revegetation plants in a reclamation program.
    • Responses of endophyte-bearing and endophyte-free varieties of Lolium perenne L. to fungicide treatment and simulated herbivory

      Boerner, R. E. J.; Scherzer, A. J.; Sturgis, B. G. (Society for Range Management, 1990-01-01)
      The effects of the presence of fungal endophytes, treatment with a systemic fungicide, and simulated herbivory on growth and biomass allocation were investigated in 2 varieties of perennial ryegrass (Lolium perenne): 'Repell', an endophyte-bearing variety, and 'Pennfine', a low-endophyte variety. In the absence of herbivory or fungicide there were no significant differences in the growth or pattern of biomass allocation between varieties. Treatment with the systemic fungicide benomyl reduced growth of both varieties by approximately 50% and reduced root growth more than shoot growth; fungicide effects were similar in the 2 varieties. Simulated herbivory reduced root growth more in endophyte-bearing Repell plants than in endophyte-free Pennfine plants, and root:shoot ratios of Repell plants were significantly lower than those of Pennfine plants following either moderate or severe herbivory. Statistically significant interactions between fungicide treatment and simulated herbivory were frequent in Repell plants but absent in Pennfine plants, suggesting that the fungicide had both direct phytotoxic effects and indirect effects mediated through the loss of endophytes by the Repell plants. While the proximate cost to seedlings bearing endophyte seemed small, the presence of the endophytes altered the allocation pattern of biomass following herbivory in such a way as to increase the probability of mortality.
    • Seedbed ecology of winterfat: effects of mother-plant transpiration, wind stress, and nutrition on seedling vigor

      Booth, D. T. (Society for Range Management, 1990-01-01)
      The upward movement of absorbed salts within a plant is influenced by the transpiration stream. This study tested the hypothesis that transpiration by winterfat mother plants affects seedling vigor. Mature plants, growing in a greenhouse, were exposed to forced air and measurements were made on water loss from the plants, concentrations of Ca++, Mg++, Na+, and K+ in the diaspores, and on offspring growth parameters. The diaspores produced by the plants were germinated and grown under 2 identical temperature regimes, except that 1 regime included 1 hour of dark-period freezing stress. The forced-air treatment had no detectable effect on mother plants, including no significant (P less than or equal to 0.05) effect on water loss or on cation concentrations in the diaspore. However, it did significantly decrease offspring vigor. Analysis of the total test-plant population revealed significant, linear relationships between water loss and: diaspore yield, Ca++ and K+ concentrations in the diaspore, seedling dry weight, and seedling hypocotyl length. Linear relationships between seedling variables and covariables provided evidence that Ca++, K+ and Na+ influence seedling weight, moisture, and hypocotyl length. It is concluded that mother-plant transpiration, windstress, and nutrition affect offspring vigor.
    • Soil moisture patterns below mounds of harvester ants

      Laundré, J. W. (Society for Range Management, 1990-01-01)
      Harvester ants are a major component of western rangeland. Little is known about ants' role in soil water dynamics. Annual patterns of soil moisture under mounds of the harvester ant (Pogonomyrmex owyheei, Cole) were studied in southeastern Idaho. Soil moisture at 20-cm intervals to a depth of 100 cm was estimated monthly with a neutron probe. Between 60 and 100 cm, higher levels of moisture were found below mounds than in control areas. The amount of water added to the soil during spring recharge was greater in control areas at 20 cm but greater under ant mounds at depths below 60 cm. Under ant mounds, approximately 1.3 cm more water was added to the soil between 60 and 100 cm.