• Grazing effects on germinable seeds on the fescue prairie

      Willms, W. D.; Quinton, D. A. (Society for Range Management, 1995-09-01)
      The germinable seed bank in a grassland affects the succession of degraded range and the recolonization of disturbed sites, and must be understood to predict potential responses to management. The germinable seed bank on the fescue prairie was characterized and its relationship to grazing, season, and depth of burial determined. The study was conducted in the fescue prairie of southwestern Alberta in livestock exclosures and on paddocks that, since 1949, have been stocked at fixed rates to achieve light, moderate, or heavy grazing pressures. Surface debris was sampled in fall and spring, and soil was sampled to a depth of 6 cm in spring. The samples were spread on vermiculite in trays and the seeds allowed to germinate over a 90-day period. In fall, total surface seed numbers m(-2) increased from 1,785 to 7,783 from the ungrazed to heavily grazed site, and most of the differences were accounted for by whitlow-grass (Draba spp.) and Kentucky bluegrass (Poa pratensis L.). These species also contributed most to differences between fall and spring on the grazed sites. Total seed numbers were similar (1,790 vs 1,803) in spring and fall on ungrazed sites. The species composition of the seed bank did not change with depth. In the soil, the annual forb pygmyflower (Androsace septentrionalis L.) was the most common seed but was not detected in a vegetation survey. Soil disturbance in the fescue prairie is more likely to lead to a seral community dominated by annual forbs, than a rough fescue (Festuca campestris Rydb.) dominated grassland.
    • Interference between cheatgrass and yellow starthistle at 3 soil depths

      Sheley, R. L.; Larson, L. L. (Society for Range Management, 1995-09-01)
      Cheatgrass (Bromus tectorum L.) and yellow starthistle (Centaurea solstitialis L.) have invaded over 250 thousand hectares throughout the Pacific Northwest. Future management of rangelands dominated by these species will require an understanding of the plant-plant interactions which contribute to the regulation of community dynamics and the establishment of desirable plants. Addition series experiments, with total stand densities ranging from 20-20,000 plants m(-2), were used to quantify the interference between cheatgrass and yellow starthistle in unrestricted soil depths on 12-day intervals throughout the growing season and in soil depths restricted to 0.2- and 0.5-m. Intraspecific interference was nearly twice as important as interspecific interference when plants were grown in unrestricted soil. Resource partitioning by cheatgrass and yellow starthistle was associated with rooting depth. When restricted to a 0.5-m depth, resource partitioning did not occur and intra- and interspecific interference were similar for both species. Restriction to a 0.2-m depth resulted in cheatgrass density being twice as important as yellow starthistle density for predicting yellow starthistle shoot weight. Yellow starthistle density was not important for predicting cheatgrass shoot weight. Cheatgrass appeared to have a competitive advantage over yellow starthistle in shallow soils, but the rooting depth and seed production capacity of yellow starthistle was greater than cheatgrass in deep soil.
    • Long term change in vegetation following herbicide control of larkspur

      Ralphs, M. H. (Society for Range Management, 1995-09-01)
      Larkspur (Delphinium spp.) control can reduce cattle deaths on mountain rangelands, but vegetation cover must be maintained to protect watersheds from erosion. The objective of this study was to evaluate the long term impact of herbicides on larkspur control and cover of associated species. Duncecap larkspur (Delphinium occidentale S. Watts) near Oakley Ida., and tall larkspur (D. barbeyi Huth) near Manti Utah, were the target species. Picloram (4-amino-3,5,6-trichloro-2-pyridinecarboxylic acid) was applied at 1.1, 2.2, and 4.5 kg ae/ha; glyphosate (N-(phosphonomethyl)glycine) was applied at 0.06, 1.1, and 2.2 kg ai/ha; and metsulfuron (1-[[[[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)amine]carbonyl ]amino]sulfonyl]benzoic acid) was applied at 0.035, 0.07, and 0.14 kg ai/ha. Picloram at 2.2 kg/ha maintained long-term control of both larkspur species (> 80%) when applied in the vegetative, bud, and flower growth stages. Total grass cover was higher on picloram plots than other treatments. Forb cover declined and bare ground was greater in picloram plots than other treatments at Manti. Metsulfuron controlled duncecap larkspur when applied in the vegetative stage. However, long-term control of tall larkspur at Manti declined as new tall larkspur seedlings established. Glyphosate controlled both larkspurs when applied in the vegetative and bud stages, but it allowed undesirable annual and rhizomatous forbs and shrubs to increase by the end of the study. Grass cover was lower on glyphosate plots than on other treatments. Bare ground was higher on glyphosate plots than other treatments at Oakley, but was intermediate at Manti.
    • Nitrogen and phosphorus effects on blue grama and buffalograss interactions

      Richard, C. E.; Redente, E. F. (Society for Range Management, 1995-09-01)
      Soil water availability and soil texture appear to influence the relative distribution of blue grama [Bouteloua gracilis (H.B.K.) Lag.] and buffalograss [Buchloe dactyloides (Nutt.) Engelman]. However, nutrient gradients may affect competitive interactions where the species occur together and may influence revegetation efforts in abandoned croplands. A greenhouse experiment was conducted to test whether competition between species was prevalent under relatively nutrient-rich vs. nutrient-poor conditions. Blue grama and buffalograss plants were grown in intra- and interspecific pairs under 4 nutrient regimes representing combinations of low and high availabilities of nitrogen (N) and phosphorus (P). Interspecific competition was evident only with high N and P availability. Blue grama exhibited greater aboveground biomass, increased tiller production and higher N and P contents when grown in mixture, compared to monocultures. This was accompanied with a reduction in tiller production and belowground P content in buffalograss grown in mixture. Stolon production in buffalograss was prevalent only with high P. Blue grama had greater biomass than buffalograss regardless of nutrient treatment. Blue grama appears to be more competitive than buffalograss with high nutrient availability and more stress tolerant with low fertility.
    • Nitrogen fertilizer use efficiency in steer gain on old world bluestem

      Berg, W. A.; Sims, P. L. (Society for Range Management, 1995-09-01)
      Old World bluestem (Bothriochloa ischaemum L.) is the major grass being planted for improved pastures on marginal farmland in western Oklahoma and adjacent areas in Texas. The farmland is often deficient in plant available N as a result of up to 100 years of cultivation and erosion. This study determined N fertilizer use efficiency on steer gain when grazing Old World bluestem in northwestern Oklahoma where average annual precipitation is 575 mm yr(-1). The study was conducted over 4 summer grazing seasons on Pratt soils (sandy, mixed thermic Psammentic Haplusalfs). Nitrogen rates of 0, 34, 68, and 102 kg N ha(-1) yr(-1) were applied to paddocks in a randomized complete block design with 4 blocks. Steer gain averaged 220 kg ha(-1) yr (-1) and 3.3 kg per kg N applied at the 34 kg N ha(-1) yr(-1) rate. Steer gain ranged from 2.3 to 4.3 kg yr(-1) per kg of N applied at the rate of 34 kg N ha(-1) yr(1). About an additional kg of steer gain per kg N applied was realized for the second 34 kg N ha(-1) yr(-1) increment from 34 to 68 kg N ha(-1)yr(-1). Gain was negligible from the third 34 kg N ha(-1) yr(-1) increment from 68 to 102 kg N ha(-1)yr(-1). Early summer grazing of N-fertilized Old World bluestem has high stocker production potential.
    • Seed size distribution, germination, and emergence of 6 switchgrass cultivars

      Aiken, G. E.; Springer, T. L. (Society for Range Management, 1995-09-01)
      Switchgrass (Panicum virgatum L.) has potential as a forage and biomass crop, but difficult establishment has limited its use. Germination and emergence were studied for 6 cultivars of switchgrass ('Alamo', 'Blackwell', 'Cave-in-Rock', 'Kanlow', 'Pathfinder', and 'Trailblazer'). Germination studies were conducted to determine the effect of light on germination and coleoptile length, and to determine the effect of seed size (40, 50, 60, 70, and 80 degrees air valve settings for a South Dakota seed blower) on germination. A greenhouse study was also conducted to examine the effect of seed size, planting depth, (5, 10, and 20 mm), and soil type (sand and 2 silt loams) on emergence. Germination of unsized seed increased linearly as duration in the germination chamber increased from 7 to 21 days for all cultivars. Although presence of light did not affect germination, coleoptile length under continuous darkness averaged 4.1 cm and was greater than the 1.0 cm measured for those with daily light exposure of 16 hours. Both germination and emergence increased nonlinearly as seed size increased. For both silt-loam soils, emergence was low and not affected by planting depth. A nonlinear decline in emergence with increased planting depth was detected in sand 7 days after planting, but not after 14 and 21 days. Results of the study indicate that seed size and soil texture had a greater effect on emergence than did planting depth down to a depth of 20 mm.
    • Shrub preference and utilization by big game on New Mexico reclaimed mine land

      Wood, M. K.; Buchanan, B. A.; Skeet, W. (Society for Range Management, 1995-09-01)
      Mined lands are reclaimed so the land can be used for other purposes after mining. At the La Plata Mine in New Mexico, post-mining land uses include livestock grazing and providing wildlife habitat. The objective of this research was to evaluate use of seeded and volunteer shrubs by mule deer (Odocoileus hemionus) and elk (Cervus canadensis) during the first opportune season, which occurred 7 years following reclamation. Twelve species of shrubs (10 planted and 2 volunteer) were found on 4 different topdressing treatments. Five branches of shrubs for each species were marked and lengths measured prior to and following the winter wildlife grazing season to determine amount of use. Greatest use by both deer and elk was on curlleaf mountain mahogany (Cercocarpus ledifolius Nutt.), followed in decreasing order by fourwing saltbush (Atriplex canescens [Pursh] Nutt.), rubber rabbitbrush (Chrysothamnus nauseosus [Pall.] Britton), common winterfat (Ceratoides lanata [Pursh] Moq.), shadscale (A triplex confertifolia [Torr. and Frem.] Wats.), antelope bit terbrush (Pursia tridentata [Pursh] DC.), big sagebrush (Artemisia tridentata Nutt.), skunk bush sumac (Rhus trilobata Nutt.), Utah juniper (Juniperus osteosperma [Torr.]Little), fringed sagebrush (Artemisia frigida Willd.), service berry (Amelanchier alnifolia Nutt.), and pinyon pine (Pinus edulis Engelm.). The greatest shrub utilization was on the Jocity topdressing treatment, which is the name of the soil series from which the topdressing was obtained. The Jocity soil series was found on a flood plain site dominated by greasewood (Sarcobatus vermiculatus [Hook.] Torr.). Other shrub utilization, in decreasing order of use, was on topdressing that was a mixture of Jocity and Atrac topdressing, spoil topdressing, and Atrac topdressing, which is a soil series found on an upland site dominated by big sagebrush.
    • Soil carbon and nitrogen of Northern Great Plains grasslands as influenced by long-term grazing

      Frank, A. B.; Tanaka, D. L.; Hofmann, L.; Follett, R. F. (Society for Range Management, 1995-09-01)
      Three mixed prairie sites at Mandan, N.D. were grazed heavily (0.9 ha steer-1), moderately (2.6 ha steer-1), or left ungrazed (exclosure) since 1916. These sites provided treatments to study the effects of long-term grazing on soil organic carbon and nitrogen content and to relate changes in soil carbon and nitrogen to grazing induced changes in species composition. Blue grama [Bouteloua gracilis (H.B.K) Lag. ex Griffiths] accounted for the greatest change in species composition for both grazing treatment. Relative foliar cover of blue grama was 25% in 1916 and 86% in 1994 in the heavily grazed pasture and 15% in 1916 to 16% in 1994 in the moderately grazed pasture. Total soil nitrogen content was higher in the exclosure (1.44 kg N ha-1) than in either grazing treatment (0.92 and 1.07 kg N ha-1 for moderately and heavily grazed, respectively) to 107-cm depth. Soil organic carbon content avg 72, 6.4, and 7A kg m-2 to 30.4 cm soil depth and 14.1,11.7, and 14.0 kg m-2 to 106.7 cm soil depth for the exclosure, moderately grazed, and heavily grazed treatments, respectively. Compared to the exclosure the moderately grazed pasture contained 17% less soil carbon to the 106.7 cm depth. Heavy grazing did not reduce soil carbon when compared to the exclosure. Based on 13C analysis and soil organic carbon data to 15.2 cm depth, blue grama or other C4 species contributed 24% or 12 kg m-2 of the total carbon in the heavily grazed and 20% or 0.8 kg m-2 of the total carbon in the moderately grazed pastures during the 1916 to l99l time period. The increase in blue grama, a species with dense shallow root systems, in the heavily grazed pasture probably accounted for maintenance of soil carbon at levels equal to the exclosure. These results suggest that changes in species composition from a mixed prairie to predominantly blue grama compensated for soil carbon losses that may result from grazing native grasslands.
    • Use of degree-days in multiple-temperature experiments

      Romo, J. T.; Eddleman, L. E. (Society for Range Management, 1995-09-01)
      This research compared results from germination and growth when the experiment duration was chronologically set or based on degree-days. Seeds of smooth brome (Bromus inermis Leyss.), plains rough fescue (Festuca altaica Trin. subsp. hallii (Vasey) Harms), prairie coneflower (Ratibida columnifera (Nutt.) Woot. and Standl.), and silver sagebrush (Artemisia cana Pursh.) were germinated at 5, 10, 15, 20, and 25 degrees C for 28 days or 400 degree-days (Base temperature = 0 degrees C). Root and shoot weights of seedlings of these species were compared at 5, 10, 15, 20, 25 and 30 degrees C after growing them 20 days or 200 degree-days. With the exception of prairie coneflower, optimal temperatures for germination were 2 to 4 degrees C lower when incubated 400 degree-days compared to 28 days. Total germination for prairie coneflower was not significantly different (P = 0.454) at 28 days or 400 degree-days. Interacting effects of the duration of experiments and temperature significantly (P less than or equal to 0.001) influenced root and shoot weight of all species. Except for shoot weight of smooth brome, predicted optimum temperatures for root and shoot growth were 7 to 21 degrees C lower at 200 degree-days than 20 days. These experiments illustrate that results from germination and growth studies can vary substantially depending on whether chronological time or degree-days are used as the end point. Thus, ecological interpretations or management recommendations can be quite different. Degree-days may be more meaningful than chronological units for germination and growth studies because they integrate time and temperature. The use of degree-days as an end point for experiments rather than chronological time deserves further consideration by researchers.
    • 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.
    • Viewpoint: The state and transition model applied to the herbaceous layer of Argentina's calden forest

      Llorens, E. M. (Society for Range Management, 1995-09-01)
      The ecological trends in the vegetation of the caldén (Prosopis caldenia Burk.) forest of central Argentina have generally been explained with a model that assumed a unique equilibrium state or "climax." This model does not adequately explain the ecological changes that occur in the understory of the caldén forest. Recently, models that present different stable states of vegetation have been suggested. These vegetation states do not change unless relatively drastic management or climatic actions occur. Observations of vegetation changes, grazing regimes, and other aspects of management permitted the development of a basic scheme to explain changes in the herbaceous layer in the caldén forest, based on the state and transition model. Five stable states and 9 transitions are proposed to account for current herbaceous associations and their origins. This model seems to more accurately explain transitions between the different vegetation states in the area, some of which could not be readily explained by the "climax" model.