• Impacts of rotational grazing on mixed prairie soils and vegetation

      Dormaar, J. F.; Adams, B. W.; Willms, W. D. (Society for Range Management, 1997-11-01)
      In this study the impact of a rotation grazing system on the soil and vegetation of a Stipa-Bouteloua-Agropyron community in the mixed prairie ecoregion was compared with the ungrazed treatment in exclosures. At a low stocking rate, grazing had no effect on the vegetation but did alter soil quality. Grazing pressure was so light in the rotational grazing treatment that recovery of productivity, as measured by standing crop and litter, was not significantly different from the ungrazed treatment. Conversely, the species distribution was unchanged but was indicative of a lower seral state for this mixed prairie. The effect of grazing on this community was indirect, possibly by altering the microenvironment. The relationships observed among forage production, soil chemistry, and species composition raise questions on the importance of any one variable expressing range condition on the mixed prairie.
    • Implications of rising atmospheric carbon dioxide concentration for rangelands

      Polley, H. W. (Society for Range Management, 1997-11-01)
      Extensive rangelands and other vegetation types that we know today formed while atmospheric carbon dioxide (CO2) concentration was low (50 to 75% of today's concentration). Fossil fuel burning and deforestation and other land use changes during the last 200 years have increased CO2 concentration by about 30%, to the present 360 parts per million (ppm). Atmospheric CO2 will continue to rise during the next century, possibly to concentrations that are unprecedented for the last several million years. Much of the potential importance of CO2 concentration to vegetation derives from its influence on plant carbon balance and water relations. Plants grow by assimilating CO2 that diffuses into leaves through stomatal pores. Inevitably associated with CO2 uptake is transpirational loss of water vapor through stomata. Transpiration rates usually decline as CO2 increases, while, in many plants, photosynthesis and growth increase. These"primary" responses to CO2 can lead to a multitude of changes at the plant and ecosystem levels, ranging from alteration of the chemical composition of plant tissues to changes in ecosystem function and the species composition of plant communities. The direct physiological responses of plants to CO2 and expression of these responses at higher scales differ among species and growing condition. Growth response to CO2 is usually highest in rapidly-growing plants that quickly export the carbohydrates formed in leaves and use them for storage or new growth and allocate a high proportion of fixed carbon to produce leaves. Growth is also more responsive to CO2 in plants with the C3 (most woody plants and 'cool-season' grasses) than C4 photosynthetic pathway (most 'warm-season' grasses). These and other differences among species could lead to changes in the composition of rangeland vegetation, but generalizations are difficult. On many rangelands, species abundances are determined more by morphological and phenological attributes that influence plant access to essential resources like nitrogen and light and reaction to fire, grazing, and other disturbances than by physiological traits that are sensitive to CO2 concentration. Species composition probably will be most responsive to CO2 on moderately water-limited and disturbed rangelands where multiple positive effects of CO2 on plant water relations can be expressed and competition for light is minimized. Greatest initial changes in species composition likely will occur on C3/C4 grasslands and at the transition between grasslands and woodlands. Plant production should also increase on water-limited rangelands, but CO2 may have little influence on production when nutrient elements like nitrogen are severely limiting.
    • Observations of Lupinus sulphureus-induced "crooked calf disease"

      Pantner, K. E.; Gardner, D. R.; Gay, C. C.; James, L. F.; Mills, R.; Gay, J. M.; Baldwin, T. J. (Society for Range Management, 1997-11-01)
      Lupine-induced "crooked calf disease" occurred in a fall calving herd of cows in Northeastern Oregon. Sixty-seven calves from a herd of 131 cows (51%) were born with congenital skeletal malformations primarily of the front limbs, neck, or spine and a few had cleft palates. Because of the nature of the malformations, lupine was suspected, and investigation of the ranch and pastures where cows grazed revealed 2 species of lupine (Lupinus sulphureus; Douglas ex. Lindl. and Lupinus leucophyllus; Douglas ex. Hooker) and poison-hemlock (Conium maculatum). Poison-hemlock was not grazed and therefore eliminated as the teratogenic plant. Extensive grazing of the Lupinus sulphureus especially the seed pods was evident. Chemical analysis of the 2 lupine species demonstrated that L. sulphureus was likely the cause of the birth defects because it contained high levels of the quinolizidine alkaloid anagyrine, a known teratogen. Lupinus sulphureus is a yellow-flowered lupine and contained 1.84% anagyrine in the seed, whereas Lupinus leucophyllus, a purple flowered lupine, contained other quinolizidine alkaloids but no anagyrine. The seed pods of L. sulphureus were high in total alkaloids (42 mg/g of dry seed), of which 45% was anagyrine. After a review of breeding records, grazing patterns and growth stage of plants, it was determined cattle probably ingested L. sulphureus in the seed pod stage during critical fetal developmental periods of gestation. Epidemiologic studies suggested the critical gestational period included day 21 to day 100; 70% of the malformed calves were born to cows that were exposed to the plant during gestation days 60 to 80. The risk of deformities was markedly increased in fetuses exposed during this interval. A few malformations occurred in cows exposed to the lupine as early as gestation day 21 and as late as day 100. We conclude that L. sulphureus was the teratogenic species, and producers should prevent cows from grazing L. sulphureus during gestation days 40 to 100 and consider herbicide control of this lupine species.
    • Preference and behavior of cattle grazing 8 varieties of grasses

      Ganskopp, D.; Myers, B.; Lambert, S.; Cruz, R. (Society for Range Management, 1997-11-01)
      We compared the forage preferences of steers grazing among 8 varieties of grasses at 2 stages of phenology on the Northern Great Basin Experimental Range near Burns, Ore. Varieties included: 'Nordan' (Agropyron desertorum (Fischer ex Link)Schultes) and 'CD-II' (A. desertorum X A. cristatum (L.) Gaertner) crested wheatgrass; 'Magnar' and 'Trailhead' Basin wildryes (Leymus cinereus (Scribner &Merrill) A. Love); 'Goldar' bluebunch wheatgrass (Pseudoroegneria spicata (Pursh)A. Love); 'Bozoisky-Select' Russian wildrye (Psathyrostachys junceus (Fischer) Nevski); 'Bannock' thickspike wheatgrass (Elymus lanceotatus ssp. lanceolatus (Scribner &J.G. Smith) Gould), and 'Secar' Snake River wheatgrass (proposed nomenclature Elymus lanceolatus ssp. wawawaiensis (Scribner &J.G. Smith) Gould). Three esophageal-fistulated steers grazed each paddock, with 3 paddocks grazed at the boot stage of development, and 3 paddocks grazed after grasses entered quiescence. In boot-stage trials, steers were very selective and collectively harvested 53% of total bites from the preferred CD-II and Nordan. These crested wheatgrasses also ranked higher (P < 0.05) in bites visit and time/visit. Magnar, Trailhead, and Bozoisky-Select were avoided. When grasses were quiescent, steers were less selective; and CD-II, Nordan, Goldar, Bannock, and Bozoisky-Select were all equally acceptable. Magnar and Trailhead were again avoided. Steers consistently took more bites (p < 0.05) from preferred forages and regrazed preferred plants before any variety was depleted. Mean distance traveled between successive feeding stations was greater during bootstage trials (2.4 m) than at quiescence (1.4 m), suggesting steers searched among the nearest 48 neighboring plants in boot-stage trials and the nearest 24 neighbors during quiescence. Measures of grazing time per variety were strongly correlated (r > 0.95, P < 0.01) with total bites harvested from varieties and are probably adequate for ranking relative preferences of steers. By selectively grazing at both stages of phenology, cattle diets were higher in CP, P, and ADL than the standing crop. During boot-stage trials, diets were also higher in Ca and Mg than forage analyses would suggest. Except for phosphorus, the nutritive content of all varieties was satisfactory for lactating beef cattle at both stages of phenology. Given their proven ease of establishment, competitive ability, nutritional value, grazing tolerance, and high relative palatability, we suggest the crested wheatgrasses (CD-II and Nordan), are excellent candidates for reclaiming or establishment of pastures for beef production programs in the northern Great Basin.
    • Seeded versus containerized big sagebrush plants for seed-increase gardens

      Welch, B. L. (Society for Range Management, 1997-11-01)
      Seed production of big sagebrush (Artemisia tridentata Nutt.) plants established from containerized seedlings was compared to plants established by direct seeding. A garden of 'Hobble Creek' mountain big sagebrush (Artemisia tridentata ssp. vaseyana (Rydb.) Beetle) and a garden of Gordon Creek Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis Beetle &Young) were established in central Utah for this study. Each garden consisted of 10 rows of plants. Seed-derived plants were established on odd-numbered rows and container-derived plants in even-numbered rows. Seed-derived plants produce more seeds, larger top growth, deeper roots, lateral roots nearer the soil surface, and heavier root systems than container-derived plants. Seed-derived plants also produced large prominent tap roots; the containerized plants did not. Seed-derived plants had a zero death rate for the 4 study years. Death rates for containerized plants were 16% ('Hobble Creek') and 13% (Gordon Creek). To help meet seed demands, growers should establish seed-increase gardens with seed-derived plants. A cautionary note: It is unknown if the use of container-derived plants for adaptation trials might erroneously influence the results of such studies. However, the root development problems described in this study should cast some doubt.
    • Vegetation, cattle, and economic responses to grazing strategies and pressures

      Manley, W. A.; Hart, R. H.; Samuel, M. J.; Smith, M. A.; Waggoner, J. W.; Manley, J. T. (Society for Range Management, 1997-11-01)
      Rotation grazing strategies have been proposed to increase stocking capacity, improve animal gains, and improve forage production and range condition. We compared continuous or season-long, 4-pasture rotationally deferred, and 8-paddock time-controlled rotation grazing on mixed-grass rangeland near Cheyenne, Wyo. from 1982 through 1994. Stocking rates under light, moderate and heavy grazing averaged 21.6, 47.0, and 62.7 steer-day ha-1; grazing pressures were 11.0 to 90.1 steer-day Mg-1 of forage dry matter produced. We estimated above and below-ground biomass, botanical composition and basal cover. Bare ground and cover of warm-season grasses, forbs, and lichens were greater under heavy stocking; cover of litter, western wheatgrass, and total cool-season graminoids were greater under light stocking. Stocking rate and grazing strategy had no effect on above-ground biomass and little effect on below-ground biomass. Under heavy stocking, percent of above-ground biomass contributed by forbs increased, especially under time-controlled rotation grazing, and that of western wheatgrass decreased. Otherwise, effects of grazing strategy, level vs. slope, and north vs. south slope on vegetation were insignificant. Steer average daily gain decreased linearly as grazing pressure increased (r2 = 0.44); grazing strategies had no significant effect. When cattle prices are favorable, the stocking rates that are most profitable in the short run may be high enough to reduce range condition.
    • Wildlife numbers on late and mid seral Chihuahuan Desert rangelands

      Nelson, T.; Holechek, J. L.; Valdez, R.; Cardenas, M. (Society for Range Management, 1997-11-01)
      Seasonal wildlife observations were made along transects on 2 pastures in late seral and 2 pastures in mid seral condition in southcentral New Mexico in non-drought and drought years (1993, 1994). Remaining climax vegetation was about 64% and 57% on late seral pastures. About 37% and 32% of the climax vegetation remained on mid seral pastures. Total wildlife and total bird sightings/km2 during the study period were higher (P < 0.10) on the mid compared to late seral rangelands. The same number of wildlife species were seen on the late and mid seral pastures. Sightings of scaled quail (Callipepla squamata Vigors), mourning doves (Zenaida macroura Linnaeus), prong-horn (Antilocapra americana Ord), and desert cottontails (Sylvilagus auduboni Mearns) showed no differences (P> 0.10) between late and mid seral condition rangelands. Black-tailed jackrabbit (Lepus californicus J.A. Allen) numbers were higher (P