• Variability of Miserotoxin Concentration in Timber Milkvetch

      Majak, W.; McLean, A. (Society for Range Management, 1975-09-01)
      The variability in miserotoxin concentration of 120 individual timber milkvetch plants was determined in the bud, flower, and pod stages of growth on rough fescue grassland, parkland, and Douglasfir zone locations. Although a broad dispersion in miserotoxin levels was evident within each sampling unit of ten plants, the grassland samples exhibited the greatest toxicity with an exceptional level (10.17 +/- 1.13%) occurring during the bud stage. The bud stage of the parkland samples yielded intermediate concentrations (5.22 +/- 1.18%) while forest plants contained lower miserotoxin levels (4.08 +/- 0.95% to 2.49 +/- 0.47%). A decline in miserotoxin levels occurred during the bud-to-pod interval at the grassland and parkland sites, but significant differences were not apparent between the progressive stages of growth at the forest locations. The timber milkvetch toxicity patterns based on the variability of individual plants confirmed previously described trends derived from composite sampling.
    • Variability of near-surface soil temperature on sagebrush rangeland

      Pierson, F. B.; Wight, J. R. (Society for Range Management, 1991-09-01)
      Models used to simulate plant growth and insect development on rangelands often assume that soil temperature is homogeneous over the entire area of interest. This simplifying assumption is made because few data are available on the magnitude and structure of the spatial variability of soil temperature within rangeland communities. The influence of sagebrush on the spatial variability and diurnal fluctuations of near-surface soil temperature was examined within a sagebrush-grass plant community. Hourly soil temperatures were measured at 1-, 5-, and 10-cm depths at 30-cm intervals along a 12.3-m north-south transect over a 6-day period in March, 1989. Both classical and geostatistical techniques were used to quantify and model the magnitude and structure of the spatial and temporal variability. Maximum soil temperatures at the 1-cm depth varied from 7 to 23 degrees C under sagebrush and bare interspace, respectively. Periodic spatial patterns in soil temperature were found for all measured depths with a wavelength of periodicity approximately equal to the separation distance between sagebrush plants along the transect. Diurnal variability in near surface soil temperature was much greater in interspace areas compared to under sagebrush plants. The amplitude of diurnal variability in soil temperature at the 1-cm depth under sagebrush was similar to the amplitude of the diurnal variability at the 10-cm depth within the interspaces.
    • Variability within a native stand of blue grama

      McGinnies, W. J.; Laycock, W. A.; Tsuchiya, T.; Yonker, C. M.; Edmunds, D. A. (Society for Range Management, 1988-09-01)
      Considerable variability and patchiness have been observed within sites of native range dominated by blue grama [Bouteloua gracilis (H.B.K.) Griffiths] range at the Central Plains Experimental Range, Weld County, Colorado. Patches containing tall plants of blue grama with many seedstalks were interspersed with patches of short plants with few seedstalks. Differences in plant height were not entirely related to soil properties. Relative differences in plant height among plants collected in the field were maintained when these plants were grown in a greenhouse environment. "Dry spots" (usually 2 to 4 m in diameter) that contain dark-colored, wilted plants have also been observed during dry, hot weather. We found several differences in soil properties that could be responsible for the dry spots. All differences in soil properties were within the range for the soil series of the experimental site, an Ascalon fine sandy loam (Aridic Argiustoll). Sixty-two plants of blue grama were collected based on their variability from a single pasture, increased vegetatively in the greenhouse, and transplanted into a spaced-plant nursery. In the third growing season following transplanting, mean values for measurements on replicated clones ranged from 202 to 719 reproductive culms per ramet, 25 to 46 cm height of reproductive culms, 17 to 24 cm basal diameter, 39 to 93 grams dry matter per ramet, and from 11 June to 20 July for first anthesis. Somatic chromosome numbers were determined for 60 plants and 55 were tetraploids (4x = 40), 3 were pentaploids (5x = 50), and 2 were hexaploids (6x = 60). We concluded that the observed variability and patchiness apparently result from a combination of both genetic and edaphic factors.
    • Variable Germination Response to Temperature for Different Sources of Winterfat Seed

      Moyer, J. L.; Lang, R. L. (Society for Range Management, 1976-07-01)
      Superior sources of winterfat seed for range revegetation should be sought, but a clearer concept of what constitutes a "superior" type is necessary. Laboratory germination temperature response of seed collected from three sources was determined. Some positive reactions to 5 degrees C prechilling were observed 13-16 weeks after collection. When the same seedlots were subjected to constant temperatures of 5 degrees C, 10 degrees C, and 20 degrees C, seed from plants originating at the lower elevations (Simla, Colorado and Pine Bluffs, Wyoming) germinated best at the lower temperatures, unlike seed collected from a Laramie, Wyoming source. Kinetic studies of germination verified that rates varied among the seedlots, but were not associated with differences during any particular stage of germination. Different temperature responses between seedlots could have practical implications regarding stand establishment.
    • Variation and Names in the Poa secunda Complex

      Kellogg, E. A. (Society for Range Management, 1985-11-01)
      The members of the Poa secunda complex were studied using transplant experiments, morphological studies of population samples, and various numerical taxonomic techniques including principal components analysis and discriminant analysis. The complex is shown to comprise 2 species: Poa curtifolia, a serpentine endemic from central Washington, and P. secunda, a widespread polymorphic rangegrass. Other forms may be recognizable locally, but do not represent separate evolutionary lines. If range managers need names for these local forms, the names should be informal English names rather than Latin binomials.
    • Variation in Defecation Rates of Pronghorns Relative to Habitat and Activity Level

      Irby, L. R. (Society for Range Management, 1981-07-01)
      During June through September, 1977, pronghorn antelope (Antilocapra americana) were observed in the National Bison Range, Moiese, Montana, to determine if defecation rates were constant in different habitat types and at different levels of activity. Individuals and groups that were active 50% or more of observation periods were found to have defecation rates approximately 10 times greater than groups or individuals that were active less than 50% of observation periods. Habitat type was much less tightly related to defecation frequency than was activity level.
    • Variation in Pinehill Bluestem, a Southern Ecotype of the Andropogon scoparius Complex

      Grelen, H. E. (Society for Range Management, 1974-07-01)
      Pinehill bluestem is the most common variant of the little bluestem (Andropogon scoparius) complex in pine forests of north and central Louisiana and east Texas. It is also frequent in adjacent portions of Oklahoma and Arkansas. It differs from other inland forms of little bluestem primarily in its unreduced pedicellate spikelets, which are equal in size to the sessile spikelets. Because of vegetative similarity between pinehill bluestem and associated forms of A. scoparius, separation of varieties for purposes of forage management is not recommended.
    • Variation in Timing of Planting Influences Bluebunch Wheatgrass Demography in an Arid System

      Boyd, Chad S.; James, Jeremy J. (Society for Range Management, 2013-03-01)
      Establishing perennial grasses from seed in postdisturbance Wyoming big sagebrush (Artemesia tridentata subsp. wyomingensis Welsh) communities is often unsuccessful, due in part to a lack of knowledge of the seedling ecology of perennial grasses. We examined the influence of planting timing on germination and seedling demography of bluebunch wheatgrass (Pseudoroegneria spicata [Pursh] A. Love) in the northern Great Basin. In 2008 (year 1) and 2009 (year 2) we planted seeds monthly, September- December, in 1-m2 plots (500 seeds per plot) using a randomized block design with five replications. Germination timing was indexed using seed bags placed adjacent to 1-m2 plots and retrieved at 2-wk intervals in fall and 1 mo intervals in spring. Seedlings were marked in March-June of the year following planting; seedlings alive in July were considered initially established. Planting in September and October had up to 80% germination prior to winter, whereas December plantings germinated mainly in spring and at reduced rates (15-35%). Seeds planted in September and October emerged approximately a month earlier than November-December plantings. The percentage of germinated seeds that emerged was highest for September-October plantings but the percentage of emergent seeds surviving to the end of the first growing season was highest for later plantings. Final seedling density was lowest for November planting in year 1 and highest for September and October planting in year 2. Our data indicate that timing of and performance at critical stages of seedling development were affected by planting month. We suggest that it may be possible to use emerging technologies (e.g., seed coatings or germplasm manipulations) to produce variable chronologies of seedling development with single plantings and allow managers to exploit multiple temporal windows of opportunity for seedling establishment.
    • Variation in Utilization of Big Sagebrush Accessions by Wintering Sheep

      Welch, B. L.; McArthur, E. D.; Rodriguez, R. L. (Society for Range Management, 1987-03-01)
      We observed the effects of accessions of big sagebrush (Artemisia tridentata) on big sagebrush utilization by wintering domestic sheep. The sheep had continuous access to high quality alfalfa hay and were fed 0.28 kg of rolled barley per head per day. Utilization was expressed as a percent of the current year's vegetative growth consumed by the sheep and also as grams of dry matter eaten per stem. Utilization of accessions varied from 0 to 98% over 3 sites and from 0 to 7.112 g of dry matter per stem. The sheep tended to remove significant (60 to 70%) amounts of current growth from the more preferred accessions before removing even small (15%) amounts of less preferred accessions. If this is typical grazing behavior, preferred big sagebrush plants may be lost in areas subject to repeated grazing.
    • Variation in Winter Levels of Crude Protein among Artemisia tridentata Subspecies Grown in a Uniform Garden

      Welch, B. L.; McArthur, E. D. (Society for Range Management, 1979-11-01)
      We discovered that the midwinter crude protein content of Artemisia tridentata is under genetic control. Our study demonstrated that some accessions of A. tridentata, grown under uniform conditions, contained significantly higher levels of crude protein than others. Subspecies tridentata contained significantly higher levels of crude protein than subspecies vaseyana and wyomingensis. However, the accessions that contained the highest levels of crude protein have been reported to be least palatable to mule deer. A superior strain of A. tridentata can be developed by combining the high protein-yielding accessions with accessions that are higher in palatability. The new strain could supply more protein for mule deer on winter ranges.
    • Variation of BLM employee attitudes toward environmental conditions on rangelands

      Richards, R. T.; Huntsinger, L. (Society for Range Management, 1994-09-01)
      Using survey data collected as part of a comprehensive reevaluation of the Vale Rangeland Rehabilitation Project in eastern Oregon, this exploratory study examined variation in attitudes of Bureau of Land Management (BLM) employees toward rangeland environmental conditions. Almost one-half of the BLM employees surveyed believed the loss of streamside vegetation (48%) and streambank erosion (42%) were widespread problems on Vale rangelands. Approximately a quarter of the respondents believed rangeland soil loss (24%) and overgrazing (26%) were problems, while only a tenth believed water pollution (10%) was a problem on many or most areas. A composite scale of these attitude toward environmental conditions on rangelands was developed and assessed. The composite scale was regressed on respondents' regional affiliation, length of service, and ideological attitudes towards government role in natural resource management. In contrast to findings from studies for USFS employees, attitudes toward range environmental conditions were not determined by regional affiliation or length of service (P > 0.05). Rather, BLM employee attitudes toward range environmental conditions were found to vary by the interaction of length of service in the agency and attitude toward government's role in regulating water quality (P < 0.05) and managing livestock grazing (P < 0.01). As length of service increases, core beliefs, professional norms, or client constituencies may not polarize employee attitudes but rather moderate them over time. The accumulation of environmental knowledge may also tend to influence environmental attitudes so that ideological attitudes may have a weaker effect as time passes and expertise expands.
    • Variation of Esophageal Fistula Samples Between Animals and Days on Tropical Grasslands

      Torell, D. T.; Bredon, R. M.; Marshall, B. (Society for Range Management, 1967-09-01)
      Forage collected by esophageal-fistulated cattle varies in chemical composition between days and animals. The number of samples needed for a given degree of accuracy was determined. Silica content of fistula steer feces was significantly different from feces from the non-fistulated steer. There were no significant differences in crude protein, crude fiber, and ether extract.
    • Variation of Monoterpenoid Content among Subspecies and Accessions of Artemisia tridentata Grown in a Uniform Garden

      Welch, B. L.; McArthur, E. D. (Society for Range Management, 1981-09-01)
      We discovered that the midwinter monoterpenoid (volatile or essential oils) content of A. tridentata is under genetic control. We base this conclusion on the results of our study which demonstrated that some accessions of A. tridentata, grown under uniform conditions, contained significantly higher levels of monoterpenoids than others. The relationship between monoterpenoids, digestion, and palatability has not yet been conclusively demonstrated. If monoterpenoids interfere with digestion or have a negative impact on palatability, breeding and selection schemes can be developed to capitalize on the significant variation that exists among accessions of A. tridentata. Superior strains of A. tridentata could then be developed for use on mule deer winter ranges.
    • Variations in nutritional quality and biomass production of semiarid grasslands

      Corona, M. E. P.; de Aldana, B. R. V.; Criado, B. G.; Ciudad, A. G. (Society for Range Management, 1998-09-01)
      The effect of the growing season and topographic zone on biomass production, protein content, cell content (CC), lignin, cellulose, hemicellulose, digestibility (DMD), and mineral element concentrations (P, K, Ca, Mg, Na, Mn, Fe, Cu, Zn) were studied in herbage samples collected from semiarid grasslands in Central Western Spain. Protein and mineral contents decreased as the growing season progressed whereas fibre properties tended to increase. Topographic gradient significantly affected peak biomass production, fibre properties, protein and mineral contents. Stepwise multiple regression showed that the prediction of biomass production on these areas was related to cellulose, Na, Fe, and Mg contents in the grassland community whereas fibre properties were mainly predicted by Ca, Na, and Cu. Principal component analysis indicated that the temporal evolution (component II) of the organic variables determined pasture quality whereas most of the variation in mineral content was related to the topographical gradient (component I). Some organic and inorganic parameters may cause deficiencies in cattle grazing en the upper and middle zones, mostly at the end of the growing season. The data suggest that information about the temporal and spatial variations of the production and nutritional quality of semiarid grassland is necessary for making correct management.
    • Variations in Physiological Metabolites and Chlorophyll in Sexual Phenotypes of 'Rincon' Fourwing Saltbush

      Tiedemann, A. R.; McArthur, E. D.; Freeman, D. C. (Society for Range Management, 1987-03-01)
      An experiment was conducted to determine if concentrations of chlorophyll and basic metabolites (total organic nitrogen (TN), total phosphorus (TP), and total nonstructural carbohydrates (TNC)) were an indication of the physiological vigor of the 3 sexual phenotypes of fourwing saltbush (Atriplex canescens (Pursh) Nutt.). Our basic hypothesis was that males, females, and plants capable of male and female sex expression (sexually labile) were equally vigorous as was manifested in chlorophyll and metabolite levels. In June, concentrations of chlorophyll a, b, and total chlorophyll in the male phenotype were greater than in either the female or the labile phenotypes. There were no differences among phenotypes for the other dates. Male plants had the highest levels of metabolites (TN, TP, and TNC) when any differences among sexual phenotypes were significant. There were basically no differences in metabolite concentration between the female and labile sexual phenotypes. Results indicate that part of the hypothesis should be rejected-that male, female, and sexually labile plants are equally vigorous based on concentrations of chlorophyll and metabolites. Part of the hypothesis, however, can be accepted-that females and labile plants are comparable in physiological vigor. Levels of all 3 metabolites showed striking trends among sample dates, which indicated that fourwing saltbush has the capability of rebuilding its levels of metabolites in the spring at the physiologically costly time of flowering. This may be related to the photosynthetic efficiency associated with its C-4 photosynthetic pathway.
    • Variations in soil moisture content in a rangeland catchment

      Salve, R.; Allen-Diaz, B. (Society for Range Management, 2001-01-01)
      Soil water studies for California rangelands have focussed on near-surface hydrologic processes, limiting our understanding of spatial-temporal dynamics of the water regime below the root zone. Soil moisture content and potential were monitored for 16 months in 12 locations in an annual grass dominated 20 ha catchment. The data collected were analyzed by ANOVA to determine significant spatial and temporal differences in soil moisture. Further analysis identified variables that influenced the amount of moisture present at a particular subsurface location. It was determined that there were significant differences in the amount of soil moisture present along the vertical profile of each site and between sites. Soil texture, type of vegetation cover, and elevation were the significant variables that influenced the soil moisture status.
    • Vegetal Change in the Absence of Livestock Grazing, Mountain Brush Zone, Utah

      Austin, D. D.; Urness, P. J.; Riggs, R. A. (Society for Range Management, 1986-11-01)
      Canopy cover of vegetation dominated by Gambel oak was determined in 1983 in adjacent canyons characterized by different grazing histories. Results were compared with data collected in 1935, and the methods replicated those used in the earlier study. Vegetal changes since 1935 in Red Butte Canyon where livestock grazing had been excluded since 1905 were small compared with those of Emigration Canyon where heavy grazing continued into the 1930's, but was gradually phased out and discontinued in 1957. Large differences in vegetal cover between the 2 canyons reported in 1935 were mostly eliminated by 1983.
    • Vegetal recovery following wildfire in seeded and unseeded sagebrush steppe

      Ratzlaff, T. D.; Anderson, J. E. (Society for Range Management, 1995-09-01)
      Following an August wildfire, sagebrush (Artemisia L.)/grass benchlands adjacent to Pocatello, Ida., were seeded with a mixture of exotic wheatgrasses and forbs by rangeland drill in November 1987. The effects of seeding on vegetation development in the immediate postfire years were evaluated by comparing plant density, vegetal cover, species composition, species diversity, and standing crop in seeded areas to that in unseeded control plots in 1988 and 1989. We also examined cover of bare ground, litter, and growth form between treatments and between sampling periods. Twenty paired 10-m transects were established in seeded and unseeded areas on each of 3 plots on the burned benches. Plant density, vegetal cover, and species diversity were lower in the seeded areas than in the unseeded areas in 1988 and 1989. Species composition, species richness, and standing crop were similar between treatments. Establishment of seeded species was poor, probably as a result of drought conditions in 1987 and 1988. Most plants observed in seeded and unseeded areas in the spring of 1988 sprouted from established perennials. Even though the first postfire season was a drought year, plant cover in the unseeded areas (18.3%) approached that estimated by a U.S. interagency task force as needed to stabilize soils on that site. In the following year, which had average precipitation, plant cover in both treatments exceeded the task force's estimate of prefire cover. Because the indigenous plant species recovered rapidly, seeding of this burn was unnecessary to establish plant cover and counterproductive in terms of erosion potential. These results serve to emphasize that objective criteria should be established for evaluating the necessity of postfire seeding.