• Using multivariate techniques to quantitatively estimate ecological stages in a mixed grass prairie

      Uresk, D. W. (Society for Range Management, 1990-07-01)
      Cluster analysis followed by stepwise discriminant analysis was used to delineate ecological stages on a mixed grass prairie in western South Dakota. Forty-seven variables were analyzed for 48 sites ranging from potential vegetatlon to early seral stages. A cover-frequency index for western wheatgrass (Agropyron smithii), blue grama (Bouteloua gracilis), and buffalograss (Buchloe dactyloides) was the most valuable in identifying 4 different (P<0.0001) ecological stages. Ecological stage classification was estimated to be 95% accurate. The methods presented are quantitative, precise, easy, time-efficient, and meet the goals of resource managers with a minimum of bias.
    • Soil surface characteristics and emergence of big sagebrush seedlings

      Young, J. A.; Evans, R. A.; Palmquist, D. (Society for Range Management, 1990-07-01)
      The emergence of big sagebrush (Artemisia tridentata) seedlings from 5 gardens where both the seed source and the soils were reciprocated was investigated over a 5-year period in western Nevada. The sites where the study was conducted were located at the arid extremes for mountain (A. tridentata subsp. vareyana) and basin big sagebrush (A. tridentata subsp. tridentata) in the trans-Sierra Nevada area. Soils, sites, and seed sources differed significantly (P=0.01) in seedling emergence. The driest site, where it was difficult to obtain seedling emergence even on a year of above average precipitation, had a soil surface that was very conducive to the germination of seeds of big sagebrush when the seedbed was moved to garden locations with greater environmental potential. Seedbed quality differed markedly among sites with soil derived from decomposing granite versus metavolcanic sources. Big sagebrush seeds were buried in soils derived from granite through a winnowing action. Seeds from a non-granitic soil site were also adapted, apparently through size and shape, to this winnowing self-burial. The dominant microenvironmental factors contributing to seedling emergence tended to be site and seed source specific. Microtopography in the fall, when seeds were dispersed, and seasonal precipitation were dominant factors controlling the emergence of big sagebrush seedlings.
    • Soil and vegetation responses to sewage sludge on a degraded semiarid broom snakeweed/blue grama plant community

      Fresquez, P. R.; Francis, R. E.; Dennis, G. L. (Society for Range Management, 1990-07-01)
      Three rates of dried sewage sludge (22.5, 45.0, and 90.0 Mg (megagrams) ha-1), were applied to a degraded semiarid grassland site on the Upper Rio Puerto Watershed in west-central New Mexico. Various soil and plant parameters were determined over 4 growing seasons. Most soil macronutrients, such as nitrogen (N), phosphorus (P), and potassium (K), and micronutrients, such as copper (Cu), iron (Fe), manganese (Mn), and zinc (Zn), increased linearly with increasing sludge amendment rates. Heavy metals (cadium (Cd) and lead (Pb)) did not change as a result of sludge amendment in the first 3 growing seasons. However, concentrations of soil Cu, Mn, and Cd were just above maximum acceptable standards in the heaviest sludge treatment after 4 growing seasons. Plant density, specks richness, and diversity all decreased with increasing sludge rates. However, total plant foliar cover and herbaceous yields increased significantly with the application of sludge. Blue grama (Bouteloua gracilis (H.B.K.) Lag.) cover and yields, in particular, increased 2 to 3 fold over the control as a result of sludge amendment, whereas broom snakeweed (Gutierrezia sarothrae (Pursh) Britt. + Rusby) density decreased over 4 growing seasons. The most favorable soil and vegetation results were from the 22.5 and the 45 Mg ha-1 sludge application rate.
    • Silicon uptake and distribution in agropyron smithii as related to grazing history and defoliation

      Cid, M. S.; Detling, J. K.; Whicker, A. D.; Brizuela, M. A. (Society for Range Management, 1990-07-01)
      A controlled environment experiment was performed on plants from 2 Agropyron smithii Rydb. (western wheatgass) populations to determine how defoliation at 1-week intervals and graxing history affected total silicon accumulation in shoots, and how Si was distributed within the plant. Plants were collected from a heavily grazed, 10-year-old prairie dog colony and an ungrazed, 40-year-old exciosure at Wind Cave National Park, South Dakota. After 18 weeks, the total amount of Si accumulated in shoots was similar in plants from both populations, regardless of whether or not the plants were clipped. However, the Si concentration in shoots was greater in nondefoliated than defoliated plants of both populations because of Si dilution resulting from greater shoot production in defoliated pIants. In both populations, roots and leaf blades had the highest Si concentrations, rhizomes had the lowest concentrations, and sheaths, crowns, and belowground stems had intermediate concentration.
    • Seed abscission and retention in Indian ricegrass

      Whalley, R. D. B.; Jones, T. A.; Nielson, D. C.; Mueller, R. J. (Society for Range Management, 1990-07-01)
      Each spikelet of Indian ricegrass [Orysopsis hymenoides (Ram. and Schult.) Ricker] consists of a floret enclosed in a pair of glumes. As each seed matures, (1) the glumes open, (2) the lemma hairs reflex outward, and (3) the abscission layer across the rachilla fractures. This study concerned the relationship of these 3 processes to seed shattering. PI 478833 (Yellowstone Co., Mont.), had a more acute angle between the opened glumes (glume pair angle) and lower seed weight, both of which may contribute to seed retention, than ‘Paloma’ (Pueblo Co., Colo.). In Paloma and PI 478833, glume pair angle was not greater with a noret in the spikelet than without, thus the intluence of lemma hairs on opening the glumes is probably minimal. The abscission (separation) layer between the floret and rachilla of Paloma consists primarily of cells with cellulosic walls, is 1 to 2 cells thick, and lies diagonally across the rachilla. The abscission layer is distal to several layers of sclerenchyma cells with heavily lignified walls (protective layer). The abscission layer is well developed before anthesis, and it is unlikely that any genotypes lack this layer. Since lemma hairs are not related to seed retention and the abscission layer is well developed long before abscission, selection for acute glume pair angle at seed maturity may improve seed retention in Indian ricegrass, increasing harvestable seed yield.
    • Relationships between pasture forage components and fecal chemical composition

      Karn, J. F.; Hofmann, L. (Society for Range Management, 1990-07-01)
      A major problem in evaluating nutritional quality of the grazing animal’s diet is collecting forage representative of that being grazed. We compared the chemical composition of simulated diet (SD) and mower clipped (MC) forage samples to each other and to fecal chemical composition data. Forage from crested wheatgrass [Agropyron desertorum (Fischer ex. Link) Schuhes], western wheatgrass [Puscopyrum smititii(Rydb.) A. Love], smooth bromegrass (Bromus inermis Leyssor), Russian wildrye [Psuthyrostachys juncea (Fisher) Nevskil, and native range pastures was collected every 2 weeks beginning 14 June and continuing through 20 September 1983. Fresh fecal samples from grazing steers were obtained 2 days following forage collections. Variability among individuals hand clipping forage to simulate a grazing animal’s diet was less than the variability between mower strips for in vitro digestible organic matter (IVDOM), calcium (Ca), and magnesium (Mg). Correlation coeffkients between SD and MC residuals were low. Coefficients between SD and fecal residuals were higher for acid detergent fiber (ADF), IVDOM, Ca, and phosphorus (P) than coefficients for the same variables obtained with MC and fecal data. The highest coefficients using residual data were achieved with fecal Ca and SD ADF, cellulose, Ca, and Mg r = -0.84, -0.81, 0.84, and 0.81, respectively. Interactions Involving pastures and sample dates were significant for the same effects for P, ADF, cellulose, and IVDOM for SD and fecal data. Data suggest that some fecal components, primarily Ca, may be useful in predicting the diet quality of grazing cattle, but these relationships need further examination.
    • Phenological patterns and adaptations in an Artemisia/Agropyron plant community

      Pitt, M. D.; Wikeem, B. M. (Society for Range Management, 1990-07-01)
      The phenology of 75 plant species belonging to an Artemesia tridentata Nutt./Agropyron spicutum (Pursh.) Scribn. & Smith plant community in southern British Columbia was recorded in 1978 and 1979. Plant species were classified witbin 4 phenological groups that are hypothesized to reflect adaptation to spatial and temporal distribution of soil moisture. Summer Mature taxa (36 species, including 20 perennial forbs and 10 annual grasses and forbs) initiate growth early, fIower rapidly, and mature before or soon after summer drought began. Favorable moisture conditions in the fall may produce some regrowth. Summer Quiescent taxa (27 species, including 8 of 9 perennial grasses) also initiate growth early in spring, develop fairly rapidly, but flower later than Summer Mature taxa, becoming only semidormant during summer drought. Significant regrowth often occurs in response to fall moisture. Protracted Growth taxa (4 species) display delayed spring growth, followed by fall flowering. These deeply rooted shrubs continue to grow and develop slowly throughout the frost-free period. Eight, generally shallowly rooted forbs were classified as Spring Ephemerals that initiate development very early in spring, flower and terminate growth before summer drought, and rarely resprout in fall. These 4 phenological groups provide flushes in botanical composition, forage production, and nutrient availability that should be reflected witbin grazing management and rangeland inventory programs.
    • Nonstructural carbohydrates and spring regrowth of two cool-season grasses: Interaction of drought and clipping

      Busso, C. A.; Richards, J. H.; Chatterton, N. J. (Society for Range Management, 1990-07-01)
      The role that accumulated carbohydrates play in plant regrowth has been discussed for over 60 years. However, few quantitative studies have been published on the importance of carbohydrates for regrowth in early spring after plants have been exposed to periods of either drought or drought plus defoliation. We examined the relationship between total nonstructural carbohydrate (TNC) concentrations and pools (biomass X concentration) and spring regrowth for crested wheatgrass [Agropyron desertorum Fisch. ex Link) Schult.] and bluebunch wheatgrass [Pseudoroegneria spicata (Pursh) A. Love ssp. Spicata; Syn. A. spicatum (Pursh) Scribn. and Smith] with and without clipping under drought, natural, and irrigated conditions. In spring 1985 and early spring 1986, after 1 or 2 years of clipping, crown and root TNC concentrations an IT NC pools per tiller were generally similar for clipped and unclipped plants of both species. Nonstructural carbohydrate concentrations in crowns and roots did not relate to rate or total production of dark regrowth in mid-spring 1985 and early spring 1986. In early spring 1986 following 2 years of repeated treatments, crown and root TNC pools were on average 7 times higher under drought, in both clipped and unclipped plants, than they were under the higher moisture-level treatments for both species. The large pools of TNC in drought-treated plants appeared to enhance the production of dark regrowth when meristematic limitations on growing tillers did not exist in early spring. These results suggest that plants exposed to prolonged periods of drought or drought plus defoliation may have rapid initial regrowth upon alleviation of these stresses because high amounts of TNC may have accumulated in their storage organs during stress. In addition, the results suggest that high TNC availability facilitates growth only when meristematic activity is high.
    • Mycorrhizal influences on big bluestem rhizome regrowth and clipping tolerance

      Hetrick, B. A. D.; Wilson, G. W. T.; Owensby, C. E. (Society for Range Management, 1990-07-01)
      Mycorrhizal symbiosis is critical to growth of many warm-season prairie grass seedlings, but its effect on regrowth of rhizomes has not been determined. As forage species, the effect of grazing on the symbiosis is also important. when the impact of mycorrhizae on regrowth of Andropogon gerardii Vit. rhizomes was assessed, A. gerardii rhizomes collected from the field and grown with mycorrhizal inoculum produced larger plants than rhizomes grown in the absence of the symbiont. The effect of the symbiosis on clipping (simulated grazing) tolerance was quantified by growing A. gerardii in steamed or nonsterile prairie soil, with or without mycorrhizal fungus inoculation. Plants were clipped and a portion of the plants harvested at 6, 12, 18, 24, and 30 weeks after planting. As an additional control, Benomyl fungicide was applied to plants to inhibit the symbiosis. Mycorrhizal clipped plants were larger than nonmycorrhizal clipped plants, but the difference diminished with successive clippings. Mycorrhizal root colonization also decreased in response to repeated clipping. Maximum shoot and root biomass of mycorrhizal plants was produced at 12 and 18 weeks, respectiveIy. Fungicide-treated plants did not grow appreciably after the fit clipping. Thus, mycorrhizae improved clipping tolerance, but with repeated intensive clipping, significant changes in root/shoot ratio occurred and eventually mycorrhizal root colonization and growth benefit were lost.
    • Methods of administering ytterbium for estimation of fecal output

      Hatfield, P. G.; Clanton, D. C.; Sanson, D. W.; Eskridge, K. M. (Society for Range Management, 1990-07-01)
      Three experiments were conducted with grazing and penned animals to evaluate the accuracy and precision of different methods of administering ytterbium (Yb) as a marker to estimate fecal output. A paired t test was used to evaluate differences between marker estimates of fecal output and fecal output measured by total collection. Marker administration methods within an experiment were compared in a one-way analysis of variance using the absolute percentage deviation of the marker estimates from total collection. In Experiment 1, wethers were confined in metabolism crates and orally administered either a pulse dose or a once daily dose. Both methods overestimated fecal output (7.3% for the once daily and 11.2% for the pulse dose method); however, the once daily dose was more precise (SE = .78%) than the pulse dose (SE = 2.17%). In Experiment 2, a crossover design with steers grazing dormant bromegrass pasture was employed to compare estimates of fecal output by pulse dosing and once daily dosing of Yb via rumen cannula. Although both methods underestimated fecal output (4.0% for the once daily and 11.5% for the pulse dose), once daily dosing was more precise (SE = 2.36%) than pulse dosing (SE = 3.64%). In Experiment 3, an intraruminal constant release Yb bolus was compared with daily feeding of Yb-labeled supplement using grazing and pen fed steers. The constant release bolus overestimated fecal output 13.8% on pasture and 41.3% in the pen study. Standard errors for the constant release bolus were 4.02% (pasture) and 4.76% (pen). Although use of Yb in a labeled supplement did not provide an accurate estimate of fecal output (80.1 and 106.0% of total collection on pasture and in pen, respectively), it had a lower SE than the constant release bolus method during both the pasture and pen studies. Once daily dosing was more precise than a pulse dose for estimating fecal output in Experiments 1 and 2. The constant release bolus used in Experiment 3 does not appear to be suitable for estimating fecal output of grazing cattle.
    • Lehmann lovegrass in southeastern Arizona: Biomass production and disappearance

      Cox, J. R.; Ruyle, G. B.; Roundy, B. A. (Society for Range Management, 1990-07-01)
      Lehmann lovegrass (Eragrostis lehmanniana Nees), a perennial bunchgrass from southern Africa, has recently replaced native grasses on 200,000 ha in southeastern Arizona. Hence the need to determine annual fluctuations in live and dead biomass in wet and dry years. This information is necessary if we wish to determine (1) potential plant productivity changes on Arizona rangelands after the Lehmann lovegrass invasion, and (2) how the presence of Lehmann lovegrass has affected animal utilization and grazing management. Live biomass was present throughout the year but August peaks were almost 2,000 kg/ha in 1 wet summer, 1,430 kg/ha in 2 normal summers, and 960 kg/ha in 1 dry summer. Recent-dead approached zero in August when live peaked, and slowly accumulated in fall and winter. Old-dead peaked before the summer rains when temperature peaked and rapidly disappeared following snow accumulations in winter. Litter was highly variable among sampling areas, plots, and sampling dates but amounts usually peaked before the summer rains and decreased in winter and spring. Lehmann lovegrass annually produces 3 to 4 times more green forage than native grasses, but cattle prefer native grasses more than Lehmann lovegrass.
    • High-performance short-duration and repeated-seasonal grazing systems: Effect on diets and performance of calves and lambs

      Volesky, J. D.; Lewis, J. K.; Butterfield, C. H. (Society for Range Management, 1990-07-01)
      Diet composition, performance, and production of calves and lambs grazing in combination were contrasted between a repeated-seasonal (RSG) (May-Sept.) and a 16-subunit, 1-herd high-performance short-duration grazing (HPSDG) system during 1983 and 1984. Animal numbers were adjusted with put-and-take sets of livestock to attain planned forage use levels for each cycle in HPSDG and comparable end-of-season use levels in both treatments. Diet quality, as estimated from fecal nitrogen (N), was better (P<0.05) for the RSG livestock especially during the first 2 grazing periods. Similarity indices of lamb and calf diet composition indicated compatibility of the lamb and calf mix in both grazing systems treatments. Calves primarily selected western wheatgrass (Agropyron smithii Rydb.) and annual grasses and lambs selected buffalograss (Buchloe dactyloides [Nutt.] Engelm.) and blue grama (Bouteloua gracilis [H.B.K.] Lag. Ex Griffiths). Average daily gain (ADG) of RSG calves was greater in both 1983 and 1984 (0.52 and 0.68 kg/d) compared to HSPDG calves (0.39 and 0.62 kg/d, P<0.05). RSG lamb ADG (72.6 g/d) was greater in 1983 compared to HPSDG (45.4 g/d, P<0.05). Attained stocking rates were 35 and 25% higher in HPSDG during 1983 and 1984, respectively. Gain/ha, however, was greater for the HPSDG calves and combined livestock (calves + lambs) only during 1984 (P<0.05).
    • Grazing and plant growth interactions in a semiarid Festuca pallescens grassland (Patagonia)

      Bertiller, M. B.; Defose, G. E. (Society for Range Management, 1990-07-01)
      The effects of grazing on relative (g g-1 d-1) and absolute (g m-2 d-1) aboveground net primary productivity and senescence of coirón blanco (Festuca pallescens (St. Yves) Parodi) were investigated in northwestern Patagonia. Aboveground net primary productivity under ungrazed and grazed conditions was estimated by means of a simulation model fitted to biomass data. Relative and absolute aboveground net primary productivity was greater for grazed than ungrazed plants during the early growing season while the inverse occurred during the late growing season (reproductive period). Grazing reduced the relative and absolute aboveground senescence during the late growing season. Relative and absolute effective primary productivity, expressed as the difference between the corresponding primary productivity and senescence, were greater for grazed than ungrazed plants. This increase is in accordance with the grazing optimization hypothesis. However, the increase was not of sufficient magnitude to compensate for losses of green biomass caused by grazing. Results imply that current grazing intensities in this region reduce aboveground productivity of coirón blanco. It follows that a reduction in stocking rates would be necessary to increase aboveground primary productivity.
    • Epicuticular wax in honey mesquite: seasonal accumulation and intraspecific variation

      Jacoby, P. W.; Ansley, R. J.; Meadors, C. H.; Huffman, A. H. (Society for Range Management, 1990-07-01)
      Epicuticular wax on the leaves of honey mesquite (Prosopis glandulosa) increased rapidly from May to July and stabilized or decreased by late summer. Pattern of accumulation best fit a second order polynomial regression equation using day of year as the independent variable. Considerable variation in wax accumulation was found among individual trees within populations and appeared to be consistent from year to year. Wax generally increased from about 0.35 g m-2 to more than 1.00 g m-2 during the growing season. A difference in maximum wax accumulation was detected between the 2 years of study and was attributed to differing environmental conditions. These findings may partially explain resistance of honey mesquite to folk-applied herbicides.
    • Effect of long-term, year-long grazing at moderate and heavy rates of stocking on diet selection and forage intake dynamics

      Pinchak, W. E.; Canon, S. K.; Heitschmidt, R. K.; Dowher, S. L. (Society for Range Management, 1990-07-01)
      A 2-year experiment was conducted to determine the effect of 27 years of continuous grazing at moderate (7 ha/cow/yr) (MC) and heavy (5 ha/cow/yr) (HC) rates of stocking on seasonal diet selection and forage intake dynamics. Nine trials were conducted to determine differences between treatments in botanical composition and quality of diets and forage intake. Proportion of Texas wintergrass (Stipa leucothrica Trin. and Rupr.) in diets was greater (P<0.05) in the MC than HC treatment whereas amounts of warm-season short- and midgrasses were less. Differences between treatments in botanical composition of diets were related to differences in seasonal availability and live:dead tissue ratios of forages. However, such differences did not generally affect diet quality. Supplementation of HC cattle with 20% CP breeder cube either replaced forage organic matter intake (January 1986) or substituted for insufficient forage availability (February 1987). Supplementation never stimulated forage intake. Forage organic matter intake was restricted at forage standing crops below 700 kg/ha.
    • Differences in riparian vegetation structure between grazed areas and exclosures

      Schulz, T. T.; Leininger, W. C. (Society for Range Management, 1990-07-01)
      The valuable role that healthy riparian ecosystems play in regional diversity of plant and wildlife communities is just beginning to be recognized. Resource managers need to know how degraded riparian areas respond to changes in management, such as reduction and eliiination of grazing. Differences in vegetation structure were examined in a montane riparian zone in north-central Colorado after 30 years of cattle exclusion and continued, but reduced, grazing pressure. In order to assess the changes in the riparian community, canopy coverage, density, and standing crop of important riparian species were measured in 1985 and 1986. Total vascular vegetation, shrub, and graminoid canopy cover was greater (P greater than or equal to 0.05) in the exclosures as compared to grazed areas, while forb canopy cover was similar (P>0.05) between treatments. Exclosures had nearly 2 times the litter cover, while grazed areas had 4 times more bare ground. Willow canopy coverage was 8 l/2 times greater in protected areas than in grazed areas. Kentucky bluegrass (Poa pratensis L.) cover was 4 times greater in grazed areas than exclosures, while the cover of fowl bluegrass (Poa palustris L.) was 6 times greater in the protected sites. Canopy cover of other important riparian species, such as tufted hairgrass (Deschampsia caespitosa (L.) Beauv.), Nebraska sedge (Carex nebraskensis Dewey), and beaked sedge (C. rostrata Stokes), was similar (P>0.05) between treatments. Mean peak standing crop over the 2 years of the study ws 2,410 kg/ha in the exciosures and 1,217 kg/ha in caged plots within grazed areas. Cattle utilized approximately 65% of the current year’s growth of vegetation during the 1985 and 1986 grazing seasons.
    • Abundance, seed pod nutritional characteristics, and seed germination of leguminous trees in South Kordofan, Sudan

      Hashim, I. M. (Society for Range Management, 1990-07-01)
      Seed pods of leguminous trees are a potential source of livestock feed in Sudan. Abundance, seed pod nutritional characteristics, and seed germination of leguminous trees in south Kordofan were examined. In the study area, densities of all trees and leguminous trees were 99.8 and 24.0 trees/ha, respectively. Percentages of crude protein in seed pods, after seeds were removed, ranged from 0.1 to 27.2, in vitro dry matter digestibility from 28.1 to 59.8, in vitro organic matter digestibility from 23.3 to 59.9, and neutral-detergent fiber from 50.8 to 79.3 during the dry season. Seeds of sunut (Acacia nilotica) and girfaldud (Albisia anthelmintica) germinated only after soaking in a large volume of water; they may have contained chemical inhibitors that restricted germination. Undamaged seeds of other tree speciea required scarification with concentrated sulphuric acid for 5 to 150 minutes to give optimum germination in 2 to 9 days. Seeds damaged by Bruchid beetles failed to germinate if their embryos were eaten, but germination of damaged seeds whose embryos were not eaten was sometimes as high as that of the controls. Bores made by the Bruchids in seeds may have facilitated moisture inbibition.