• Atrazine dissipation and off-plot movement in a Nebraska sandhills subirrigated meadow

      Brejda, J. J.; Shea, P. J.; Moser, L. E.; Waller, S. S. (Society for Range Management, 1988-09-01)
      Atrazine [6-chloro-N-ethyl-N′-(1-methylethyl)-1,3,5-triazine-2,4-diamine] can be used to modify species composition of naturally subirrigated Sandhills meadows. The potential for ground water contamination exists as the water table depth ranges from 0 to 3 m. Atrazine was applied at 2.2 and 3.4 kg ha-1 in May 1984, August 1984, or May 1985 to a Gannett fine sandy loam (Typic Haplaquoll, coarse-loamy, mixed, mesic) in a Nebraska Sandhills subirrigated meadow. Residues of atrazine applied in 1984 and 1985 carried over into 1985 and 1986, respectively. Herbicide dissipation and off-plot movement were monitored in 1985 by sampling soil at 0 to 5 cm and 5 to 15 cm depths within and outside the experimental areas. Atrazine dissipation initially approached zero-order kinetics after May 1985 application, but generally followed first-order kinetics during the entire 320-day sampling period. Atrazine half-life in the entire 0 to 15 cm sampling zone was 46 +/- 7 days. Herbicide concentrations at the 5 to 15 cm sampling depth did not exceed levels measured at 5 days after application. Low and highly variable atrazine concentrations detected in some of the untreated plots and in some off-plot soil samples indicated minimal lateral movement of the herbicide.
    • Comparative chemical composition of armed saltbush and fourwing saltbush

      Garza, A.; Fulbright, T. E. (Society for Range Management, 1988-09-01)
      Armed saltbush [Atriplex acanthocarpa (Torr.) Wats.] and fourwing saltbush [A. canescens (Pursh) Nutt.] are browsed by livestock and white-tailed deer (Odocoileus virginianus Raf.). The objective of this study was to compare the chemical composition of these 2 shrubs growing together in south Texas. Leaves and stems from the outer 5 cm of current year's growth of each species were randomly collected from each of 5 stands in November 1985 and February, May, and August 1986. Samples were analyzed for crude protein (CP), calcium, potassium (K), magnesium (Mg), sodium (Na), phosphorus (P), and in vitro organic matter digestibility (IVOMD). Height and standing crop were also determined. Crude protein of armed saltbush leaves ranged from 32% in February to 19% in August. Fourwing saltbush leaf CP ranged from 24% in February to 12% in August. Armed saltbush leaves and stems generally had greater P concentrations than fourwing saltbush. Calcium, K, and Mg concentrations and leaf IVOMD of the 2 species were similar. Fourwing saltbush had lower Na concentrations and greater leaf standing crop than armed saltbush. Laboratory-determined values suggest that both species may provide nutritious browse for cattle and deer on saline rangeland.
    • Dehydration effects on seedling development of four range species

      Bassiri, M.; Wilson, A. M.; Grami, B. (Society for Range Management, 1988-09-01)
      The effects of temporary drought periods of semiarid regions were simulated by dehydration of germinating seeds of crested wheatgrass (Agropyron desertorum), Russian wildrye (Elymus junceus), alfalfa (Medicago sativa), and cicer milkvetch (Astragalus cicer) in 8 constant humidity environments, ranging from -10 to -220 MPa for 4 days. Combined effects of root excision and temporary dehydration at -22 to -160 MPa were also studied. Subsequent growth of seedlings was evaluated in growth performance tests under favorable soil moisture conditions. When the initial roots were killed by dehydration, survival of grasses depended on the development of seminal lateral root(s) from the scutellar nodes, and survival of legumes depended on development of a new meristem at the distal end or along the side of hypocotyl-root axis. The effect of dehydration was more drastic on the legumes than on the grasses, particularly at more severe conditions. While temporary dehydration of -59 MPa had little effect on grasses, it reduced the percent emergence of the legumes by about 70%. In the -220 MPa treatment, emergence percentages of crested wheatgrass, Russian wildrye, alfalfa, and cicer milkvetch were 59, 35, 6, and 1, respectively, and percentages of rooted seedlings were 58, 12, 3, and 1, respectively. Under combined effects of excision and dehydration at -160 MPa, emergence percentages of the 4 species were 50, 34, 14, and 0, respectively, and their root lengths decreased by 37, 42, 44, and 100%, respectively. Within species variation in tolerance of dehydration suggested opportunities to select and breed for this characteristic.
    • Economic comparison of aerial and ground ignition for rangeland prescribed fires

      Rasmussen, G. A.; McPherson, G. R.; Wright, H. A. (Society for Range Management, 1988-09-01)
      Average ignition costs per ha for aerial and ground ignited prescribed burns in redberry juniper (Juniperus pinchotii)-mixed grass communities were compared to determine the feasibility of using aerial ignition on rangelands. Aerial ignition techniques had greater total costs than ground ignition because of higher fixed costs. However, if greater than 4,000 ha could be burned, as a single or multiple unit, aerial ignition costs are $1.36/ha less than estimated ground ignition costs.
    • Effects of burning on germinability of Lehmann lovegrass

      Ruyle, G. B.; Roundy, B. A.; Cox, J. R. (Society for Range Management, 1988-09-01)
      Lehmann lovegrass (Eragostis lehmanniana Nees) may be viewed as either an undesirable exotic invader or an important ground cover and forage plant on southwestern rangelands, depending on management goals. Successional responses to management practices intended to control or enhance this grass are highly dependent on the processes of natural revegetation. The effect of seasonal burning on germinability of Lehmann lovegrass in the seedbank was investigated on the Santa Rita Experimental Range in southern Arizona. Samples of surface soil were taken for bioassay immediately after burning in February, June, July, and November for 2 years. Nearly 40% more seedlings emerged from bioassay samples taken from burned than unburned plots. The increase in germinability of Lehmann lovegrass seeds associated with fire may be one of several factors important in its observed ability to re-establish after mature plants are killed by burning.
    • Effects of prescribed fire on Chamaespartium tridentatum ((L.)P. Gibbs) in Pinus pinaster (Aiton) forests

      Rego, F. C.; Bunting, S. C.; Barreira, M. G. (Society for Range Management, 1988-09-01)
      Prescribed burning in Pinus pinaster forests was evaluated in terms of the effects on Chamaespartium tridentatum. Postfire forage quantity and quality were studied. Total biomass production, current year's shoot production, and nutritive value were studied in relation to time since fire. Chamaespartium, a vigorous resprouter, achieved 50% of its preburn biomass level in 2 years. Current year's shoot production reached a maximum 3 to 4 years after fire. Nutritive value of Chamaespartium was briefly enhanced by burning but returned to preburn levels. Seasonal variations of forage quality were very important with lower values in summer or fall. Short-lived increases in protein, cellulose, and hemi-cellulose contents after fire in Chamaespartium shoots returned to preburn levels in 4 years. This supported the traditional fire frequency in the shrublands of 3 to 7 in order to maintain forage quality and productivity.
    • Estimation of phytomass for ungrazed crested wheatgrass plants using allometric equations

      Johnson, P. S.; Johnson, C. L.; West, N. E. (Society for Range Management, 1988-09-01)
      The allometric relationship between plant volume and phytomass of crested wheatgrass was studied for the 1981, 1983, and 1984 growing seasons in west-central Utah. Basal diameters, canopy diameters, and standing plant heights were measured for individual plants. Three models of volume (basal elliptical cylinder, canopy elliptical cylinder, and elliptical cone section) were tested as predictors of plant phytomass using nonlinear regression. Elliptical cone section produced the highest R2 and lowest SEE, but requires measurement of canopy diameters which may be subject to excessive measurement error. Basal elliptical cylinder produced R2 and SEE values nearly comparable to those of the elliptical cone section; moreover, this model does not require measurement of canopy diameters, making it the practical choice. Nonlinear regressions for plants by size class (small, medium and large) were produced using 1983 data. Predictive ability of size class-specific equations was compared to that of the equation for all size classes combined. When phytomass of only small or medium size class plants was predicted, the SEE of size class-specific equations was slightly lower than the SEE of the equation for all size classes combined. When phytomass of plants from all size classes was predicted, however, the equation for all size classes combined produced the lowest combined SEE for new data (i.e., data not used to generate the equation). There were substantial year-to-year differences between equations, which indicates the necessity of producing new equations each year.
    • Fire effects on tobosagrass and weeping lovegrass

      Roberts, F. H.; Britton, C. M.; Wester, D. B.; Clark, R. G. (Society for Range Management, 1988-09-01)
      Fireline intensity (kW/m) was measured on 61 plots of weeping lovegrass [Eragrostis curvula (Schrad.) Nees.] and tobosagrass [Hilaria mutica (Buckl.) Benth.] burned as headfires and backfires during late winters of 1982 and 1983 in western Texas. Relative humidity, air temperature, wind speed, soil moisture, soil temperature, and fuel moisture were measured at time of burning. Vegetation response was based on plant yield, plant height, and number of seed stalks. Plant responses were not correlated with fireline intensity or any of the environmental parameters measured. Although fireline intensity is an important fire behavior measurement, high fireline intensities did not cause a negative impact on either weeping lovegrass or tobosagrass. Therefore, range managers can conduct high intensity fires to damage or burn down shrubs and not damage these grasses.
    • Methods of ytterbium analysis for predicting fecal output and flow rate constants in cattle

      Coffey, K. P.; Pickett, E. E.; Paterson, J. A.; Hunt, C. W.; Miller, S. J. (Society for Range Management, 1988-09-01)
      Continuous or pulse doses of Yb-labeled feedstuffs with subsequent fecal sampling can be used to estimate digesta passage rates and fecal output in ruminants. However, the validity of such estimates is affected by mineral elements in fecal samples that interfere with atomic absorption analysis of Yb. A procedure was developed involving co-precipitation (CoP) of Yb with lanthanum (La) oxalate at pH 1.0 to separate Yb from interfering elements present in the fecal matrix. The procedure was tested for accuracy of Yb determination, repeatability, and for validity of predicting fecal output. Repetitive analysis of the same sample resulted in a coefficient of variation of 2.2% for the CoP technique. An experiment using 12 mature Angus cows offered 1 of 4 diets tested the accuracy of predicting fecal output using one- and two-compartment models. Cows were pulse-dosed with Yb-marked orchardgrass neutral detergent fiber, and fecal samples were collected from the rectum at 9, 12, 15, 18, 24, 32, 40, 48, 60, 72, 84, and 96 h after dosing. Ytterbium content of fecal samples was determined by neutron activation (NA) or atomic absorption spectrophotometry after slow oscillation of the fecal ash for 12 h in 3 M nitric and 3 M hydrochloric acid (acid leaching; AL) or CoP of Yb with La oxalate. For fecal Yb concentrations fit to the one-compartment model, the k0 parameter (scaling factor related to initial marker in the age-dependent compartment) was greater (P<.05) for CoP than for AL or NA. Likewise, calculated first appearance of marker (Tau) and the age-dependent rate constant (k1) were greater (P<.05) for CoP than for NA. For the two-compartment model, the initial marker concentration estimate (lambda0) was greater (P<.05) for CoP than for NA or AL, and Tau was less (P<.10) for NA than for CoP. Rate constant estimates (lambda1, lambda2) were not affected by method of analysis. For both models, fill and retention time estimates differed (P<.05) between CoP and NA. Fecal output estimated from both models was similar to actual fecal output for CoP, but the one-compartment model estimate of fecal output for AL and NA over-estimated (P<.05) actual fecal output. Likewise, the two-compartment model estimate of fecal output for NA was greater (P<.05) than actual fecal output. Co-precipitation of Yb with La oxalate appears to be a valid analytical procedure that may yield more accurate estimates of fecal output than other reported procedures.
    • Optimal stocking rate for cow-calf enterprises on native range and complementary improved pastures

      Hart, R. H.; Waggoner, J. W.; Dunn, T. G.; Kaltenbach, C. C.; Adams, L. D. (Society for Range Management, 1988-09-01)
      Complementary pasture-native range systems are known to increase production per cow and per hectare of cow-calf enterprises, but the proper ratio of complementary pasture to range and the optimum stocking rate on each has not been established. From 1978-1985, crested wheatgrass [Agropyron desertorum (Fisch.) Schult.]-native range and meadow bromegrass (Bromus biebersteinii Roem. and Schult.)-alfalfa (Medicago sativa L.)-native range systems were grazed by cow-calf pairs and yearling heifers at a range of grazing pressures. Gains of all classes of cattle and conception rate of cows remained constant across a range of low grazing pressures, then declined linearly as grazing pressure increased. These response functions were used to calculate economically optimum pasture-to-range ratios and stocking rates at 1980-1984 average costs and prices. The optimum ratio of crested wheatgrass to range at estimated yields, costs and prices was 1:3.94 (0.66 ha of wheatgrass and 2.60 ha of range per animal unit), which returned $35.70/ha to land, labor, and management. Usual ratios of 1:8 to 1:12 were much less profitable. At optimum stocking rates, the brome-alfalfa-native range system returned only $3.38 more per hectare than the crested wheatgrass-native range system, not enough to pay additional cost of irrigation. Optimum ratios, stocking rates, and returns will vary with levels of forage production, production costs, and livestock prices.
    • Peer review of technical manuscripts

      Frasier, Gary W. (Society for Range Management, 1988-09-01)
    • Plant community development on petroleum drill sites in northwestern Wyoming

      Smith, P. W.; Depuit, E. J.; Richardson, B. Z. (Society for Range Management, 1988-09-01)
      Plant community and soil development were investigated on oil/gas drilling sites occupying both sagebrush and coniferous forest vegetation types in northwestern Wyoming. Sites ranged from 3 to 33 years in age since abandonment. Some sites were seeded at abandonment, while others revegetated naturally. Vegetation and soils were sampled and compared on disturbed and adjacent undisturbed sites. Both soils and vegetation were altered by drilling activities. Disturbed soils generally had higher bulk density and pH and lower organic matter content than undisturbed soils. All disturbed sites were vegetationally dissimilar to adjacent native sites. However, sagebrush disturbances were progressing toward undisturbed conditions more rapidly than coniferous forest disturbances. Seeding accelerated vegetation development, although at different rates between sagebrush and coniferous forest disturbances. Seeding and establishment of introduced grass species on disturbed sites did not prevent natural recolonization of native species.
    • Reader expectations: How important to meet?

      Fischbach, David A. (Society for Range Management, 1988-09-01)
    • Root excision and dehydration effects on water uptake in four range species

      Bassiri, M.; Wilson, A. M.; Grami, B. (Society for Range Management, 1988-09-01)
      Germinating seeds of crested wheatgrass (Agropyron desertorum), Russian wildrye (Elymus junceus), alfalfa (Medicago sativa), and cicer milkvetch (Astragalus cicer) were dehydrated for 4 days at -22 MPa, and/or their roots were excised, and used as treated materials. In an experiment in root growth boxes, where the seedlings depended for 60 days on the initial soil water supply, seminal primary and seminal lateral roots of grasses penetrated to the same depth. Both types of roots were similarly effective in taking up water, mainly from the upper 50 cm of the soil profile. In a sealed pot experiment under favorable moisture conditions, water uptake increased with seedling age up to 34 and 41 days for crested wheatgrass and Russian wildrye, respectively, and up to the end of the experiment (53 days) for the legume species. Leaf area of grasses was not affected by root excision alone, but it decreased due to the combined effects of root excision and temporary dehydration. Leaf area was generally proportional to water uptake within each species. In all 4 species, root excision and temporary dehydration did not affect transportation rates, while transportation rate decreased as a function of age. Transportation rates were higher in legumes than grasses and were higher in Russian wildrye than crested wheatgrass.
    • Simulation and management implications of feral horse grazing on Cumberland Island, Georgia

      Turner, M. G. (Society for Range Management, 1988-09-01)
      Cumberland Island National Seashore, Georgia, is inhabited by a population of feral horses that intensively graze the island's salt marshes. Based on 18 months of experimental grazing studies, a carbon flow simulation model was developed for a medium height Spartina alterniflora marsh and used to estimate an acceptable population size of feral horses. Five-year simulations indicated a threshold of 2,700 kg/ha aboveground Spartina biomass below which the system did not recover if intensive grazing continued. The difference between this threshold and annual peak biomass of ungrazed Spartina was used to estimate horse densities that would not cause marsh degradation. Results suggest the horse population should number between 49 and 73 horses if excessive damage to the salt marshes is to be prevented. Thus, the current population of 180 horses should be reduced.
    • The use of comparative yield and dry-weight-rank techniques for monitoring arid rangeland

      Friedel, M. H.; Chewings, V. H.; Bastin, G. N. (Society for Range Management, 1988-09-01)
      The comparative yield (CY) method for estimating pasture dry weight and the dry-weight-rank (DWR) method for determining species composition were applied in a variety of arid vegetation types by several operators. The methods were evaluated for their suitability in a range monitoring program, on the basis of consistency of estimates and the time taken. Four calibration regressions for the CY technique were compared initially and, of these, linear regression of untransformed data is recommended. Differences among operators' yield estimates were unacceptably large, and the procedure of standard selection and calibration was too slow. We suggest that photographic standards can reduce the time taken and improve precision. The DWR technique was recommended because operators achieved consistent estimates of species composition within 80 minutes, which we regarded as a reasonable time for a monitoring procedure. Weighted multipliers did not improve composition estimates. The technique was easy to use but initial training of operators was important. While fixed quadrats would probably reduce differences caused by spatial variability, time spent relocating quadrats could be excessive.
    • Toxicological investigations on Ruby Valley pointvetch

      Williams, M. C.; Molyneux, R. J. (Society for Range Management, 1988-09-01)
      Ruby Valley pointvetch (Oxytropis riparia Litv.), a native of the central Soviet Union, was inadvertently introduced into the United States during the early part of the 20th century. Ruby Valley pointvetch has long been established in southwestern Montana, is spreading into Wyoming and Idaho, and is being investigated for its potential as a forage plant. The plant was analyzed for aliphatic nitro compounds, soluble oxalates, nitrates, cyanide, and swainsonine. Swainsonine is found in 2 native Oxytropis species and causes the loco syndrome and congestive heart failure. The plant was tested for toxicity to 1-week-old chicks. Ruby Valley milkvetch tested negative for aliphatic nitro compounds, soluble oxalates, cyanide, and swainsonine. Nitrates were present at nontoxic levels. Leaves, stems, seeds, and pods were nontoxic when fed to chicks for 5 days at 1% of body weight as dried plant. Extracts of these plant parts fed in one dose at 10% of body weight (as dried plant) were likewise nontoxic.
    • Use of UV absorption for identifying subspecies of Artemisia tridentata

      Spomer, G. G.; Henderson, D. M. (Society for Range Management, 1988-09-01)
      Use of UV absorption spectra for identifying subspecies of Artemisia tridentata Nutt. was investigated by analyzing the relative optical densities of alcohol extracts from herbarium and fresh plant material at 240 nm, 250 nm, and 265 nm. In all but 1 comparison, mean relative optical densities were significantly different (p=0.95) between subspecies, but intraplant and intrasubspecies variation and overlap was found to be too large to permit use of UV absorbance alone for identifying individual specimens. These results held whether dry or fresh leaves were extracted, or whether methanol or ethanol was used as the extracting solvent.