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  Journal of Range Management, Volume 46, Number 5 (September 1993)

  Society for Range Management, 1993-09-01
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  Journal of Range Management, Volume 46, Number 6 (November 1993)

  Society for Range Management, 1993-11-01
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  Journal of Range Management, Volume 46, Number 3 (May 1993)

  Society for Range Management, 1993-05-01
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  Journal of Range Management, Volume 46, Number 4 (July 1993)

  Society for Range Management, 1993-07-01
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  Journal of Range Management, Volume 46, Number 1 (January 1993)

  Society for Range Management, 1993-01-01
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  Journal of Range Management, Volume 46, Number 2 (March 1993)

  Society for Range Management, 1993-03-01
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  White-tailed deer and cattle diets at La Michilia, Durango, Mexico

  Gallina, S. (Society for Range Management, 1993-11-01)

  Fecal analysis was used to determine the relationships between white-tailed deer (Odocoileus virginianus couesi [Coues and Yarrow]) and cattle diets (Beef Master, Hereford and criollo), in Durango, Mexico. Deer preferred shrub and tree species (85% of the diet), whereas cattle preferred grasses (61%). Although diets varied seasonally, as did forage availability and quality, the same selective forage pattern was maintained throughout the year. There was a significant difference in the use of different plant groups between the 2 herbivores. The diet overlap index (50.51%) suggested competition during the wet season, but forage was abundant (628 kg/ha dry weight biomass compared with 380 kg/ha in the dry season), thus reducing potential conflicts. Deer and cattle can simultaneously forage in this ares without detriment to either species. The vegetation can maintain a stable composition under higher utilization levels when used by 2 herbivores with different forage patterns than when used by only 1 herbivore.
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  Water quality effects on stability and phytotoxicity of picloram and clopyralid

  Whisenant, S. G.; Bovey, R. W. (Society for Range Management, 1993-05-01)

  Water quality effects on stability of picloram (4-amino-3,5,6-trichloro-2-pyridinecarboxylic acid) and clopyralid (3,6-dichloro-2-pyridinecarboxylic acid) were evaluated by determining their concentrations in spray mixtures 0, 48, and 168 hours after mixing. Gas chromatography was used to evaluate picloram and clopyralid concentrations in spray solutions mixed with different water sources or buffered water solutions. At 168 hours picloram concentrations in water from La Copita and Midland, Texas, were 11 and 12% lower than at 0-hour and 5 and 6% lower than picloram concentrations in distilled water at 168 hours. Water quality effects on phytotoxicity to honey mesquite (Prosopis glandulosa) were evaluated at 0 and 168 hours after mixing the spray solution. Water quality had no effect on clopyralid phytotoxicity to honey mesquite at either 0 or 168 hours after mixing. Phytotoxicity to honey mesquite was reduced 42% when picloram mixtures were used 168 hours after mixing with water from La Copita. This indicates the potential for reduced phytotoxicity from picloram when prepared spray solutions are not used for 7 days.
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  Viewpoint: Trend assessment by similarity—a demonstration

  Ratliff, R. D. (Society for Range Management, 1993-03-01)

  Methodology for assessing trend in range condition is still evolving. This paper demonstrates use of Dice's community similarity coefficient, 2a/(2a + b + c), with communities present at 3 times and a notional community as a goal. Coefficients range from 0 (indicating a complete lack of similarity) to 1 (indicating complete similarity). Similarity is classed as low (0 - 0.25), moderate (0.26 - 0.50), high (0.51 - 0.75), or full (0.76 - 1). Study of time-goal coefficent graphs is suggested for deciding whether trend is up, down, or static. Defining goals and lack of statistical tests are major limitations. The goal concept and use of data standardization are discussed.
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  Viewpoint: Selection for improved drought response in cool-season grasses

  Johnson, D. A.; Asay, K. H. (Society for Range Management, 1993-05-01)

  Water limits the establishment, growth, and production of cool-season grasses on semiarid rangelands, and plant improvement programs for these areas must be capable of screening breeding lines for response to drought. Although many techniques to evaluate various morphological and physiological characteristics have been proposed, few have been used successfully in plant breeding programs. Consequently, a need exists to identify and develop rapid, reliable screening techniques that can assess integrated plant response to drought in large plant populations. Improved seedling emergence has been achieved in Russian wildrye [Psathyrostachys juncea (Fischer) Nevski] by selecting for emergence from a deep seeding depth and long coleoptiles. Water uptake by roots is critical, and screening for enhanced seedling root growth in cool-season grasses offers considerable promise. In spite of the important role that stomatal control has in regulating plant water loss, limited success has been achieved in incorporating desirable stomatal characteristics into improved grass cultivars. Although osmotic adjustment appears beneficial in some crop species, more research is needed before cool-season grasses should be selected based on osmotic adjustment. Selection for improved water-use efficiency in cool-season grasses based on carbon isotope discrimination is a promising approach. Successful incorporation of these various traits into improved cool-season grass cultivars necessitates close cooperation between breeders and physiologists.
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  Viewpoint: Plant community thresholds, multiple steady states, and multiple successional pathways: legacy of the Quaternary?

  Tausch, R. J.; Wigand, P. E.; Burkhardt, J. W. (Society for Range Management, 1993-09-01)

  The climate cycles of the 2 million years of the Quaternary were a major force in the evolution of plant response to change. Quaternary climate has been primarily glacial with interglacials such as the current Holocene a minor component. Plant species responded individually to climate changes and, consequently, species composition has continually changed. The legacy of Quaternary climate change is that plant communities are far less stable than they appear to be from our perspective. They are unique at each location, difficult to define, and communities that are relics from a previous environment can be sensitive to small or transient environmental changes. Plant communities are variable both in space and time. Many ecological principles and concepts, and ecosystem paradigms derived from them, require revision to incorporate this variation. The concepts of habitat type and condition and trend, for example, do not reflect dynamic vegetation response to changes in climate. Our knowledge is presently insufficient to adequately describe interactions between ecosystems changing climate, but the patterns of vegetation response to environmental changes of the past may provide important information on vegetation response to present and future climate change. The concepts of thresholds, multiple steady states, and multiple successional pathways are helpful in understanding the dynamic interrelationships between vegetation and environmental changes.
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  Viewpoint: "Invisible colleges" and citation clusters in stocking rate research

  Hart, R. H. (Society for Range Management, 1993-09-01)

  Research on the response of livestock gain to stocking rate tends to cluster into 5 "invisible colleges", represented by 5 citation networks which only occasionally intersect. Each college is built around a paradigm of the stocking rate-gain response as developed in 2 key papers sharing 1 or more authors. Researchers tend to cite the paradigm developed by authors in their field of research or in their geographic area. Therefore conficting pardigms have existed side-by-side for decades, an unusual occurrence in most fields of science. Research is needed to critically evaluate the empirical and conceptual soundness of these paradigms.
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  Utilization of globemallow (Sphaeralcea) taxa by sheep

  Rumbaugh, M. D.; Mayland, H. F.; Pendery, B. M.; Shewmaker, G. E. (Society for Range Management, 1993-03-01)

  Globemallows (Sphaeralcea spp.) are well adapted to semiarid and arid environments. They are potentially useful as the forb component of seeding mixtures for rangeland improvement in the western states. However, the degree of acceptability of globemallow forage to livestock has not been well established. We tested 13 globemallow accessions representing 4 species and compared their utilization by sheep (Ovis aries) with that of crested wheatgrass [Agropyron cristatum (L.) Gaertn. X A. desertorum (Fisch.) Schult.] and alfalfa (Medicago sativa L.) during fall 1988 and 1989, and spring 1990 and 1991. Alfalfa consistently produced more forage per plant than wheatgrass or globemallows, and a greater portion of the alfalfa was eaten than of the other species. Sheep utilized wheatgrass more than globemallows in the fall, but the converse was true during spring pasturing. Over the 4 years, sheep ate similar proportions of wheatgrass and individual globemallows. The percentage of S. coccinea (Pursh) Rydb. forage consumed equaled that of crested wheatgrass or alfalfa in the fall but did not equal the percentage of alfalfa consumed in spring. However, S. coccinea produced much less total forage than the other species evaluated. Pre-grazing plant dry weight, dry matter content, and the occurrence of rust caused by Puccinea sherardiana Korn were negatively associated with globemallow utilization. Over-winter mortality of grazed globemallow exceeded that of ungrazed plants. Crested wheatgrass and alfalfa stands were not reduced by grazing. Globemallows are acceptable, but not highly preferred, forbs which can be seeded in environments where alfalfa and other more desirable species are not adapted.
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  Tobosa tiller defoliation patterns under rotational and continuous stocking

  Senock, R. S.; Anderson, D. M.; Murray, L. W.; Donart, G. B. (Society for Range Management, 1993-11-01)

  Continuous low animal density grazing of tobosa [Hilaria mutica (Buckl.) Benth.] in the northern Chihuahuan desert results in nonuniform forage utilization. Stocking smaller tobosa rangeland paddocks with high numbers of cattle for short periods of time may facilitate more uniform forage utilization. Two grazing periods in each of 2 consecutive years were monitored to investigate the frequency with which tobosa tillers were defoliated and the intensity of defoliation (change in height) in relation to grazing pressure under high-density seasonal rotational and low-density seasonal continuous grazing. Approximately 40% of tiller height, including leaves, was removed at each defoliation in the rotational treatment, while intensity of defoliation per grazing event remained consistent. In the continuous treatment, amount of tiller removed varied widely and was not consistent among the 4 periods. Percentage of tillers defoliated in the rotational treatment was always greater than 75%, and always less than 30% in the continuous treatment. The probability that a tiller would be grazed at least once in the rotational treatment was more than twice as great as in the continuous treatment. However, within the rotational treatment, the probability of multiple grazing events (greater than or equal to 2) on an individual tiller was less than the probability of a tiller being grazed just once. In general, high-density rotation grazing promoted more uniform. forage utilization of tobosa than low-density continuous grazing.
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  Thin layer measurement of soil bulk density

  Frasier, G. W.; Keiser, J. (Society for Range Management, 1993-01-01)

  Measurement of soil bulk densities is difficult if there are gravel, stones, or other materials present in the soil profile. A technique is offered for estimating the soil bulk density in thin layers (1.0 cm) in loose, nonuniform soils with low moisture levels. The technique consists of the removal of the soil in shallow layers. As each layer is removed, the hole is filled with a molten paraffin wax to obtain a casting of the excavated volume. Measured bulk densities values using this procedure compare well to results obtained with other techniques.
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  The use of conditional probability functions in range data analysis and simulation

  Lambert, D. K.; Harris, T. R. (Society for Range Management, 1993-03-01)

  Managers and range scientists are interested in the response of such variables as forage production and animal performance to various environmental and management factors. Due to the inability to control many of the factors affecting range systems, production responses should include distributional information in addition to their expected values. Recent developments in the estimation of conditional probability distribution functions provide the range scientist with a practical procedure to more fully characterize variable responses. The conditional probability distribution approach is applied to an analysis of forage production data from the literature. An illustration of the procedure in range decision analysis derives distributional information on animal performance and net return under several different steer stocking levels.
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  The life cycle of the range condition concept

  Joyce, L. A. (Society for Range Management, 1993-03-01)

  Recent concerns about range condition measures are not the first concerns about measuring the health of rangelands. To examine why change has not occurred in this area, this paper explores the historical development of the range condition concept in the context of the life cycle of a scientific theory. Dyksterhuis' contribution and significant impact on the concept of range condition reflects the close tie between an underlying ecological theory of the time, that grazing alters species composition in a predictable manner, and his field method which measured that change as the difference between the relative composition of the current and climax vegetation. The evolution of the range condition concept differs in significant ways from the evolution of scientific theories such as Clements' climax theory. These differences include the lack of an intellectual center for research on range condition and reflect the institutionalization of technology to measure range condition. Success of alternative models for range condition may require an underlying theory linked to a field method to successfully capture the consensus of the range community.
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  The constituent differential method for determining live and dead herbage

  Gillen, R. L.; Tate, K. W. (Society for Range Management, 1993-03-01)

  Determination of live and dead herbage fractions from mixed herbage samples requires hand separation or specialized laboratory procedures. The constituent differential method is designed to determine the relative proportion of live and dead components in a mixture based on the difference in dry matter concentration between the components. Our objective was to evaluate several characteristics of the constituent differential method under field conditions in tallgrass and mixed grass vegetation. Estimation of live standing crop by this method is most sensitive to the dry matter content of the total mixture and the dead component but becomes less sensitive as the difference between these variables increases. Time-of-day was not usually associated with dry matter content of the herbage components if sampling began after the herbage was thoroughly dry to the touch. Suggested sample sizes in large experimental units for estimating dry matter content are 40-50 samples for herbage mixtures, 10 samples for live herbage, and 5 samples for dead herbage. In 4 field trials the average value for percent live herbage determined by hand separation and the constituent differential method differed by 1.6 percentage units, which was nonsignificant P>0.10). The constituent differential method is a relatively rapid and accurate method for determining live and dead herbage fractions.
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  Technical Notes: Double sampling revisited

  Reich, R. M.; Bonham, C. D.; Remington, K. K. (Society for Range Management, 1993-01-01)

  The decision to use double sampling with a regression or ratio estimator is not a simple task. This study was conducted to determine whether a ratio or regression estimator should be used to estimate aboveground biomass of stands dominated by blue grama (Bouteloua gracilis (H.B.K.) Lag ex Steud.) in eastern Colorado. One hundred 0.25-m-1 circular plots were systematically located in a homogeneous stand of blue grama, and on each plot biomass was estimated visually and then clipped. Three methods (classical, jackknife, and bootstrap) of estimating the variance for double sampling with regression and ratio estimator were compared in a simulation study using sample sizes 10, 20, 30, 40, and 50 clipped plots. The ratio estimator consistently had smaller bias and should be used for estimating average clipped weight of blue grama. For n = 10 clipped plots, the jackknife variance estimator is recommended for constructing confidence intervals. For n greater than or equal to 20 clipped plots, the classical variance estimate should be used to obtain reliable estimates of the population variance and in estimating confidence intervals.
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  Technical Notes: Botanical components of annual Mediterranean grassland as determined by point-intercept and clipping methods

  Glatzle, A.; Mechel, A.; Va, M. E. (Society for Range Management, 1993-05-01)

  Three methods for determining proportions of botanical components, i.e., grasses, legumes, and forbs (nonleguminous dicots), of continuously grazed Mediterranean pastures were compared. Percentage contribution to dry matter yield was determined by sample clipping and separating into botanical components. Both percentage of sward and specific contribution were determined by the point-intercept method. These were defined by the relative contribution of 1 botanical component to the total number of counted intercepts between 200 pins inserted vertically into the sward and all botanical components. For specific contribution only the number of pins contacted by the various botanical components were considered, whereas for percentage of sward even multiple contacts between a pin and plant parts of a particular botanical component were taken into account. Percentage contribution was highly significantly correlated with percentage of sward (R = 0.92) and specific contribution (R = 0.93) running the analyses across all botanical components, although there was a significant trend to underestimate forbs and overestimate legumes by the point-intercept methods. It is concluded, however, that for most practical purposes determination of specific contribution, the least laborious method, should give satisfactory estimates of percentage contribution.

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