• Viewpoint: Replication, randomization, and statistics in range research

      Wester, D. B. (Society for Range Management, 1992-05-01)
      Appropriate application of significance tests in statistical analyses requires an explicit statement of hypothesis; a clear definition of the population(s) about which inferences are to be made; and a model, a sampling strategy, an analysis, and an interpretation that are consistent with these considerations. In particular, experimental design and analyses must recognize appropriate replication and random selection of experimental units from target population(s). This paper discusses some aspects of these issues in range science research. Textbook examples and examples from range science applications are discussed in parallel in an attempt to clarify issues of randomization and replication in statistical applications.
    • Training lambs to be weed eaters: Studies with leafy spurge

      Walker, J. W.; Hemenway, K. G.; Hatfield, P. G.; Glimp, H. A. (Society for Range Management, 1992-05-01)
      The objective of the study was to determine if exposure of young lambs to leafy spurge (Euphorbia esula L.) would increase the consumption of this plant. Orphan lambs were exposed to leafy spurge from birth to 11 weeks of age as a water soluble extract mixed with milk replacer and as freshly harvested plants. Ewe-reared lambs were exposed to leafy spurge by grazing them on a leafy spurge-infested pasture. Study 1 investigated the consumption of vegetative and flowering leafy spurge paired with arrowleaf balsam root (Balsamorhiza sagittata (Pursh) Nutt.) by orphan lambs during a 30-min feeding period. Experienced lambs consumed a higher percentage leafy spurge than naive lambs (P<0.03). The interaction of leafy spurge phenophase and previous experience (P<0.02) showed that experienced lambs preferred leafy spurge regardless of phenophase (70% of intake) and naive lambs only preferred leafy spurge when it was vegetative. Study 2 investigated the preference for leafy spurge on pastures with high or low leafy spurge biomass. Experienced compared to naive lambs had a higher percentage of bites (P<0.001) and preferred leafy spurge in the high spurge biomass pasture, but not in low biomass pastures. Naive lambs avoided leafy spurge in both pastures. Study 3 was a pasture trial that investigated spurge consumption by orphan and ewe-reared lambs. Percent bites and time spent grazing leafy spurge were not affected (P>0.23) by previous exposure, but daily herbage removal was greater (P<0.09) in pastures grazed by experienced compared to naive lambs (876 vs. 685 g/lamb, respectively). Experienced ewe-reared lambs had a higher rate of biting on leafy spurge (P<0.06) than naive or orphan Lambs. These studies indicate that previous experience will be an important factor affecting the use of sheep as a biological control agent for leafy spurge.
    • The effect of polyacrylamide on grass emergence in southcentral New Mexico

      Rubio, H. O.; Wood, M. K.; Cardenas, M.; Buchanan, B. A. (Society for Range Management, 1992-05-01)
      Seeding rangeland is a challenge for rangeland scientists, especially on those soils with tendency to crusting. Although some information is available on how soil conditioners affect emergence of certain comestible crops, little is known about the effect of synthetic organic matter on grass emergence. We examined the effect of polyacrylamide, a soil conditioner, on seedling emergence of blue panicgrass (Panicum antidotale Retz.), King Ranch bluestem (Bothriochloa ischaemum [L.] Keng), sideoats grama (Bouteloua curtipendula [Michx.] Torr.), plains bristlegrass (Setaria macrostachya H.B.K.), and 'salado' alkali sacaton (Sporobolus airoides [Torr.] Torr.) under field conditions. Emergence of blue panicgrass and sideoats grama was increased with polyacrylamide applications, even at the lowest concentration (10 kg ha-1) during summer 1987. No emergence response to polyacrylamide applications was found for King Ranch bluestem, and plains bristlegrass did not emerge in any experimental plots during summer 1987. During summer 1988, blue panicgrass and sideoats grama emergence was again increased with polyacrylamide applications. Emergence of 'salado' alkali sacaton and King Ranch bluestem was unaffected by polyacrylamide applications. Soil conditioners may be a feasible alternative for seeding some rangeland in areas where crusting is a problem.
    • Technical Note: Automatic sorting of free-ranging cattle

      Anderson, D. M.; Rouda, R. R.; Murray, L. W.; Pieper, R. D. (Society for Range Management, 1992-05-01)
      An automated system to weigh and sort free-ranging cattle was adapted to administer cottonseed pellets (41% crude protein) to free-ranging cattle. The frequency with which animals drank water determined the interval between supplemental feedings. The automatic spacing of individual animals was the weakest link in the chain of events leading to the sorting of cattle into groups to administer treatments. Periodically during the study, free-standing water was available due to above-average precipitation. This resulted in an inconsistent supplementation schedule because animals did not have to return through the maze to drink water. Single herd management eliminated potential pasture-treatment confounding but accentuated individual animal behavior, which resulted in a range of supplement intakes and drinking water patterns.
    • Stand density index as a predictor of forage production in northern Arizona pine forests

      Moore, M. M.; Deiter, D. A. (Society for Range Management, 1992-05-01)
      Ponderosa pine (Pinus ponderosa Laws.) overstory-forage understory relationships were studied on the Kaibab Plateau of northern Arizona to evaluate how well forage (graminoid, forb, and current year shrub) production could be predicted by stand density index (SDI). Linear and nonlinear equations were used. Stand density index, a relative measure of stand density, was a useful predictor of understory production for a variety of stand structures and ages. The linear and nonlinear equations produced coefficient of determinations of 0.76 and 0.72, and standard error of the estimates of 5.08 kg ha-1 and 5.51 kg ha-1, respectively.
    • Response of Central Plains tallgrass prairies to fire, fertilizer, and atrazine

      Masters, R. A.; Vogel, K. P.; Mitchell, R. B. (Society for Range Management, 1992-05-01)
      Tallgrass prairies are an important forage resource in the eastern Central Great Plains. The effect of spring burning, fertilization, and atrazine [6-chloro-N-ethyl-N'-(1-methylethyl)-1,3,5-triazine-2,4-diamine] on standing crop of selected herbaceous species and categories of vegetation was determined in 6 tallgrass prairie environments located near Lincoln and Virginia, Neb., from 1987 through 1989 and 1 site near Bloomfield, Neb., in 1987. The grasslands were in good to excellent condition at the time these studies were conducted. Portions of each site were burned in mid-to late spring, atrazine was applied at a rate of 2.2 kg a.iha-1 in late April to early May, and fertilizer was applied in mid-May. Despite below-normal precipitation at 6 of the 7 sites, burning combined with fertilization improved warm-season grass standing crop by 50 to 127% in 5 of the 7 grassland environments studied. This reflected the positive response of the dominant warm-season grasses, big bluestem (Andropogon gerardii Vitman var. gerardii Vitman) and indiangrass [Sorghastrum nutans (L.) Nash], to burning or fertilization. Atrazine increased warm-season grass standing crop at only the site near Bloomfield. Kentucky bluegrass (Poa pratensis L.) and annual bromes (Bromus spp.) were more susceptible to atrazine than smooth brome (Bromus inermis Leyss.). Forb standing crop was significantly reduced by atrazine alone or by burning followed by atrazine application in 4 of the 7 prairie environments. Burning combined with fertilizer application improved warm-season grass standing crop in good to excellent condition grasslands and obviated the need to use atrazine.
    • Pyrrolizidine alkaloid content of houndstongue (Cynoglossum officinale L.)

      Pfister, J. A.; Molyneux, R. J.; Baker, D. C. (Society for Range Management, 1992-05-01)
      Houndstongue (Cynoglossum officinale L.) is a biennial weed infesting pasture, hayfields, and disturbed areas throughout North America. Houndstongue contains pyrrolizidine alkaloids (PAs) that are hepatotoxic. First and second year's growth of houndstongue were harvested from emergence to maturity. Nuclear magnetic resonance was used to determine the levels of total PAs, free base, and N-oxide forms of the alkaloids in leaves, stems, buds, flowers, and pods. PA levels generally were highest (1.5 to 2.0% dry weight) in immature plant tissue, with a gradual decline during maturation. Most plant parts contained greater quantities of the N-oxide form of PAs (60-90%) compared to the free base form. Leaves and pods of mature houndstongue contained sufficient PAs to be potentially toxic if ingested by livestock.
    • Protein supplementation of steers grazing tobosa-grass in spring and summer

      Pitts, J. S.; McCollum, F. T.; Britton, C. M. (Society for Range Management, 1992-05-01)
      A 3-year study evaluated weight gain, blood urea nitrogen (BUN), and fecal nitrogen (FN) of beef steers fed 0.00, 0.34, or 0.68 kg/hd/day of cottonseed meal (41% CP) while grazing mesquite (Prosopis glandulosa var. glandulosa Torr.)/tobosagrass (Hilaria mutica [Buckl.] Benth.) range between April and July. Mixed breed beef steers (avg wt 230 kg) were allocated to three 6-pasture grazing cells and group-fed prorated amounts of supplement 3 days a week. Individual weights were recorded every 21 days. Crude protein in clipped forage samples remained above 7.0% except in July, 1985 (6.5%). Gain response varied among periods within year but the primary effects occurred in the first 40 to 60 days of grazing. In 1985, daily gains over 92 days were 0.38, 0.44, and 0.67 kg/hd/day for the 0.00, 0.34, and 0.68 kg supplement groups, respectively. In 1986 and 1987, daily gains during 85-day trials were 0.65, 0.66, and 0.71 kg/hd/day and 0.98, 1.08, and 1.07 kg/hd/day, respectively. Blood and feces were collected from 10 steers in each treatment group on each weigh date during the first 2 years. The 0.68 kg/hd/day supplement maintained higher (P<0.05) BUN and FN than the control group but response to 0.34 kg supplement was inconsistent. Performance and BUN data suggested that protein concentrate was not the appropriate supplement for steers grazing tobosagrass in the spring and summer.
    • Pine needle effects on in vivo and in vitro digestibility of crested wheatgrass

      Adams, D. C.; Pfister, J. A.; Short, R. E.; Cates, R. G.; Knapp, B. W.; Wiedmeier, R. D. (Society for Range Management, 1992-05-01)
      In vitro and in vivo digestion trials with lambs were conducted to determine effects of ponderosa pine needles (PN; Pinus ponderosa Laws.) on digestibility of crested wheatgrass (CW; Agropyron desertorum [Link] Schultes) hay. Pine needles contained shikimic acid (15-28 mg/g) and several monomeric phenolics (p-hydroxy benzoid acid, caffeic acid, p-coumaric acid, ferulic acid) and flavonoids. Tannin concentration exceeded assay limits (>10%) and terpenes were not found, probably due to the drying procedure. In the in vitro trial, needles were mixed with CW in 10% increments from 0% to 100%. In the in vivo trial, PN were fed to lambs as follows: (1) 0%, (2) 12.5%, (3) 25%, and (4) 50%, with the remainder of the diet as CW. In vitro organic matter digestibility (IVOMD) was regressed on level of PN in the substrate. As the proportion of PN increased, IVOMD declined cubicly (P<0.01). The IVOMD values ranged from 54% for 100% CW to 24% for 100% PN. In vivo digestibility of organic matter, neutral detergent fiber and acid detergent fiber declined linearly (P<0.01) as PN were increased from 0% to 50% of the diet. Apparent crude protein digestibility and N retention by lambs declined cubicly (P = 0.02 and P<0.01, respectively) and urinary N increased cubicly (P<0.01) as dietary PN increased from 0% to 50%. We concluded that PN reduce in vitro and in vivo nutrient digestibility, reduced N retention by lambs, and effects were detectable even at low levels.
    • Laboratory germination responses of 3 love-grasses to temperature in relation to seedbed temperature

      Roundy, B. A.; Young, J. A.; Sumrall, L. B.; Livingston, M. (Society for Range Management, 1992-05-01)
      Laboratory tests are often conducted to determine seed germination responses to temperatures for seedbed ecology interpretations and revegetation seeding rate calculations. To determine the utility of laboratory germination tests for indicating seedbank germinability of lovegrasses we measured seedbed temperatures and soil water on 2 semidesert grassland sites in the Southwest. We also tested germination of Lehmann lovegrass (Eragrostis lehmanniana Nees), 'Cochise' lovegrass (E. lehmanniana Nees X E. trichophora Coss & Dur.), and plains lovegrass (E. intermedia Hitch.) seed collections associated with natural or artificial revegetation studies on these 2 sites in relation to an array of constant and alternating temperatures. Germination responses to different temperatures varied with the year and source of collection and seed age and differed compared to those reported in the literature. Lehmann and Cochise lovegrass had high germination at temperature alternations similar to wet seedbed temperature extremes in December (0,2/15 degrees C) and these species and plains lovegrass were germinable at moderate temperature alternations representative of wet seedbeds in April (10/30 degrees C). Ability to germinate in laboratory tests at these temperatures is not necessarily indicative of germinability in the field for Lehmann lovegrass, which has been observed to germinate in April, not December, in wet seedbeds. All species had maximum or near maximum germination at a temperature alternation of 20/40 degrees C, which is similar to wet seedbed temperature extremes during the summer rainy period when these species usually emerge. Because of the variability in germinability of different seed collections of lovegrass over time, specific collections should be tested at specific ages relevant to seedbed ecology and revegetation studies or projects. Laboratory germination tests which mimic actual wet seedbed temperature curves might be more predictive of seedbed germinability than the usual tests which expose the seeds to abrupt temperature alternations.
    • Interactions of grazing and plant protection on basin big sagebrush (Artemisia tridentata ssp. tridentata) seedling survival

      Owens, M. K.; Norton, B. E. (Society for Range Management, 1992-05-01)
      The impact of grazing animals and plant protection on shrub seedling establishment was studied in 2 separate experiments. A total of 3,665 seedlings were monitored for survival during a sheep grazing trial in 1994, and 5,755 seedlings were monitored during a cattle grazing trial in 1986. Approximately 1/2 of the seedlings were located under the canopy of mature plants and 1/2 were located in the interspaces between plants. The presence of domestic livestock and the seedling location affected both the overall survival at the end of the growing season and the pattern of survival during the growing season. The interaction between these independent variables resulted in the highest survival (0.11) for sheltered seedlings in the grazed pastures and the lowest survival (0.009) for unprotected seedlings in the grazed pastures. Seedlings in the ungrazed pastures had survival rates intermediate between these 2 rates. The pattern of seedling survival was similar in both experiments. Seedlings in the grazed pastures experienced high mortality during the actual grazing event and immediately after grazing. Seedlings which were unsheltered experienced the lowest survival due to trampling. Survival rates late in the summer were not affected by grazing but were dependent on receiving precipitation during this normally dry period of the year. The interaction between grazing and seedling location may partially explain the aggregated distribution of Artemisia found in many communities. This aggregation should affect interspecific competition and may play a role in later stages of plant succession within these shrub-dominated communities.
    • Growth dynamics of crowns of eastern red-cedar at 3 locations in Oklahoma

      Engle, D. M.; Kulbeth, J. D. (Society for Range Management, 1992-05-01)
      Eastern redcedar (Juniperus virginiana L.) trees from a location in western, central, and eastern Oklahoma were aged by tree ring analysis to assess the relationship of tree age to tree height and crown area. The relationship of tree age to crown size differed with location. Trees in the oldest age class, 28 to 29 years, ranged in height from 6.2 m on the western Oklahoma location to 8.3 m on the eastern Oklahoma location. The oldest trees at all locations were still actively growing. Height growth rate of the oldest class of trees averaged 0.5 to 0.6 m yr-1 on the western and eastern study locations, respectively. Eastern redcedar reached 2.0 m in height at about 8 years of age on the eastern Oklahoma location. Trees reached 2.0 m in height in 10 to 14 years at the other locations. This suggests that burning intervals should be more frequent on the eastern Oklahoma location than on the central and western Oklahoma locations. Crown area as a function of tree age was not as similar as tree height among the 3 locations. Not only did the relationship differ among locations, but it differed also between 2 central Oklahoma range sites. Crown area of 28-year-old trees ranged from only 15 m2 on the central Oklahoma Loamy Prairie to 40 m2 at the eastern Oklahoma location. These data suggest that the smaller crown area of trees at the central Oklahoma location may be a result of an influence other than environment, such as an introduction of plants of a different race with an inherent columnar growth habit. The reduction in forage production associated with eastern redcedar and the efficacy of prescribed burning for controlling eastern redcedar would change more rapidly as trees age on the eastern Oklahoma location than on the other locations.
    • Fecal NIRS equations for predicting diet quality of free-ranging cattle

      Lyons, R. K.; Stuth, J. W. (Society for Range Management, 1992-05-01)
      The usefulness of near infrared reflectance spectroscopy (NIRS) for predicting diet quality of free-ranging cattle through fecal analysis was examined. Diet samples were obtained with esophageal fistulated steers; subsequently, study areas were grazed with nonfistulated lactating and dry cows to provide fecal samples representing differing forage diet quality. Diet samples, which were analyzed by conventional laboratory procedures for in vivo corrected digestible organic matter (DOM) and crude protein (CP), provided dependent variable reference data while fecal sample spectra provided independent variable data for development of NIRS predictive equations by stepwise regression. Equations were developed from a data set at one location with subsequent equation development using expanded data ranges obtained by adding samples from a second location. Standard errors of calibration (SEC) and validation (SEV) for the DOM equation developed from the expanded data range were 1.66 and 1.65, respectively; these values were nearly equivalent to the laboratory standard error (SEL) of 1.68. SEC and SEV for the CP equation developed from the expanded data range were 0.89 and 0.93, respectively, compared to the 0.44 SEL. Coefficients of determination for DOM and CP equations were 0.80 and 0.92, respectively. These statistical parameters developed from fecal spectra to predict forage diet quality are equal to or better than statistics reported in the literature for NIRS equations developed using forage spectra. Furthermore, equation standard errors were within acceptable limits for NIRS calibrations. No effects of physiological stage of animals on calibration were noted in this study. Results are interpreted to indicate that prediction of diet DOM and CP of free-ranging herbivores can be accomplished with NIRS fecal analysis to a degree of precision equivalent to conventional laboratory diet analyses.
    • Factors affecting Utah ranch prices

      Rowan, R. C.; Workman, J. P. (Society for Range Management, 1992-05-01)
      A total of 341 Utah rural land sales occurring between 1980 and 1987 were analyzed to identify and quantify the determinants of Utah rangeland and ranch prices. Two factors statistically influenced average sale price (/hectare and/or /AUM): number of hectares sold and whether buildings were included in the sale. Regression analysis incorporated statistically significant (P < 0.05) explanatory variables into a predictive equation that expressed total ranch sale price as a function of number of deeded AUMs, building value, year and month of sale, number of leased AUMs, distance to nearest town, recreation influence, and size of parcel sold. The regression model produced an adjusted R2 = 0.91. Value of buildings and number of deeded AUMs explained most of the variability in total ranch sale price.
    • Estimating herbage standing crop from rainfall data in Niger

      Wylie, B. K.; Pieper, R. D.; Southward, G. M. (Society for Range Management, 1992-05-01)
      To help local Niger government authorities and donor countries ameliorate conditions in the advent of drought, a rapid yet simple means to assess annual herbaceous production at the end of the rainy season is needed. Several rainfall variables were tested as estimators of herbaceous production using weighted and logarithmic transformation in regression analysis. A computer program was developed in Basic to generate rainfall parameters from daily rainfall data. Input parameters used to calculate the rainfall variables were varied to minimize the regression standard error of the estimates. Selected regression models were compared using 80% confidence levels for mean values for each rainfall treatment class using logarithmic and weighted regressions. The selected weighted model involved the number of moist days and consecutive dry days as independent variables. The selected logarithmic model used total rainfall as the only independent variable. These models were tested by comparing an independent data set with the 95% confidence intervals for observations. Selected models separated rangeland production classes of 200 kg ha-1 confidence limits for mean values. The logarithmic model could only do so when biomass levels were less than 800 ha-1. Thus, these models only have application for predicting herbage biomass within rather large classes.
    • Cultivated and native browse legumes as calf supplements in Ethiopia

      Coppock, D. L.; Reed, J. D. (Society for Range Management, 1992-05-01)
      Efficient use of roughages is important for calf management in the Boran pastoral system. Using local legumes as protein supplements may improve fiber utilization and thus be an appropriate intervention. Fruits (pods and seeds) of Acacia tortilis (Forsk.) Hayne subsp. spirocarpa (Hochst. ex A. Rich) Brenan, leaves of A. brevispica (Harms), and cowpea [Vigna unguiculata (L.) Walp] hay were compared with alfalfa (Medicago sativa L.) hay as protein supplements for calves using 2 approaches. Sheep fed native grass hay under confinement were used for a controlled evaluation in growth and metabolism trials. Calves grazing dry-season forage under simulated pastoral management provided in evaluation under field conditions. All supplements increased (P<0.05) nitrogen (N) intake, growth rate, and conversion of dry-matter intake into liveweight for sheep compared to unsupplemented animais. Calf growth and water intake were increased (P<0.05) relative to the control by ail supplements except cowpea hay. When statistically adjusted to a common level of N intake, N retention was similar (P>0.05) among all groups of supplemented sheep. Compared to alfalfa and cowpea diets, tanuinfferous Acacia diets had a negative effect (P<0.05) on true-N digestibility, but this was offset by their positive effect (P<0.05) on reducing loss of urinary N. The A. tortilis diet had a lower (P<0.05) true-N digestibflity than the A. brevispica diet, which was probably influenced by soluble phenolics in pods and seeds. On a nutritional basis these Acacia and cowpea materials art suitable for inclusion in improved feeding systems for Boran calves
    • Blue grama-buffalograss responses to grazing: A Weibull distribution

      Remington, K. K.; Bonham, C. D.; Reich, R. M. (Society for Range Management, 1992-05-01)
      Characterization of standing herbaceous biomass on rangeland is complicated by both temporal and spatial variability that results from patchiness in vegetation. These patches often cause nonuniform levels of grazing by livestock. Currently accepted methods for estimation of forage, and its utilization, assume a normal distribution. This assumption may not be appropriate if the frequency distribution of amount of biomass becomes skewed as grazing occurs. We evaluated the 3 parameter Weibull distribution as an alternative to the normal distribution in modeling the frequency distributions of plant height and biomass as a function of grazing intensity over time in a shortgrass steppe. Weibull distributions, estimated by probability weighted moments, fit all observed plant height and biomass data distributions at the alpha = 0.05 level of significance. In contrast, the normal distribution fit only 25% of the data sets.