• Mesquite control increases grass density and reduces soil loss in southern Arizona

      Martin, S. C.; Morton, H. L. (Society for Range Management, 1993-03-01)
      In 1974 we selected 8 pairs of gully headcuts on the Santa Rita Experimental Range. Mesquite (Prosopis velutina Woot.) on the watershed of 1 headcut of each pair was killed with diesel oil. Densities of perennial grasses and shrubs, shrub cover, surface erosion, headcut advance, and gully depth were recorded at 3-year intervals, 1974-1986. Four of the watershed pairs were in pastures grazed yearlong: 4 were in Santa Rita rotations. Each grazing schedule included 2 watershed pairs that were about 200 m higher in elevation than the other 2. In 1974, before mesquite was killed, perennial grass densities were low with little difference between assigned conditions. By 1977 perennial grass density was greater where mesquite was killed than on untreated watersheds and was greater at upper elevations. Lehmann lovegrass (Eragrostis Lehmanniana Nees.) made up almost all of the grass density increase at the upper elevation. Native perennial grasses, which were largely replaced by Lehmann lovegrass at the upper elevation, accounted for almost all of the gain at the lower elevation. Lower density (P less than or equal to 0.05) on low elevation rotation grazed watersheds in 1986 was the result of summer drouth in 1985 and 1986 that coincided with March-October grazing in 1986. Soil loss (mm) during each 3-year period was lower at headcut-soil surface grids where mesquite was dead. Advances in headcuts and changes in gully depth showed similar trends. On the 4 pairs of watersheds that were equipped to measure runoff, there was more total runoff per millimeter of rainfall where mesquite was alive than where mesquite was killed.
    • Multiple use management of California's hardwood rangelands

      Standiford, R. B.; Howitt, R. E. (Society for Range Management, 1993-03-01)
      The importance of evaluating multiple resource values on rangelands is demonstrated in this study of California's 3.0 million hectares of oak-covered (Quercus spp.) hardwood rangelands. Production functions are derived for oak tree growth on rangelands for stands with at least 50% of the total tree cover in blue oak (Quercus douglasii Hook. & Arn.) based on oak volume per acre and site index. Forage production is estimated based on oak cover, weather variables, growing period, and site factors from data reported in the literature. Hunting revenue and cost functions are derived from a survey of commercial hunting clubs, and are based on oak cover, hunter success variables, hunter demographics, advertising, livestock density, and club size. The interrelationship of these resource values is shown in output from an optimal control model that incorporates these production functions. Oak trees are gradually cleared for situations where cattle are the only economic product, whereas a residual tree canopy is maintained for cases where firewood and hunting enterprises are considered. In addition, cattle stocking is higher and net profitability is lower for the cattle only management scenario when compared with a multiple use management scenario. The development of these multiple use production functions allows the full range of resource management options to be considered.
    • President’s Address: Expanding Partnerships and Continuing Successes

      Artz, J. L. (Society for Range Management, 1993-03-01)
    • Seasonal height-weight dynamics of western wheatgrass

      Mitchell, J. E.; Elderkin, R.; Lewis, J. K. (Society for Range Management, 1993-03-01)
      Vertical biomass distributions for western wheatgrass (Agropyron smithii Rydb.) from 3 locations in western South Dakota were evaluated to determine effects of location, date, topographic position, past grazing history (vigor), and phenological development. A linear, quadratic regression was used for model development and testing, and analysis was by general linear hypothesis testing. All factors except topographic position were significant; however, only phenological development was useful in a general model for estimating utilization from the percentage of height remaining. This factor was best expressed in 3 leaf-classes of 2-4, 5-6, and 7-10 leaves per tiller. Thus, height-weight relationships can be improved as a biomass predictor if separate regressions are used for these 3 phenological classes.
    • Shortgrass range vegetation and steer growth response to intensive-early stocking

      Olson, K. C.; Brethour, J. R.; Launchbaugh, J. L. (Society for Range Management, 1993-03-01)
      A 9-year grazing trial was conducted to compare shortgrass vegetation and steer responses under intensive-early stocking (IES) at 2 stocking rates to season-long stocking (SLS). The stocking rates were (1) equal to SLS, with twice as many steers used for the first half of the SLS grazing season (2X-IES), and (2) greater than SLS. with 3 times as many steers used for the same period (3X-IES). The hypothesis tested was that SLS and 2X-IES would be similar and sustainable in terms of productivity and vegetation composition, whereas 3X-IES would be different and not sustainable. The 3 treatments were assigned to 6 pastures in a randomized-complete block. Grazing was initiated on or near 1 May each year and continued until about 15 July for IES and about 1 October for SLS. Steers were weighted at initiation of grazing and in mid-July, and SLS steers were weighed in October. Vegetation data were collected in July and October in each pasture from 10 randomly located plots. Species composition of grasses was estimated, and grasses and forbs were clipped separately to determine biomass availability. Steer total gain and average daily gain (ADG) under SLS and 2X-IES were equal (P>0.10) during the early season, but 3X-IES gain and ADG were less (P<0.05). Total-season gain was greater under SLS (P<0.05 than either IES treatment, but total- season ADG was equal to that under 2X-IES. Steer production per ha was equal under SLS and 2X-IES, but greater under 3X-IES (P<0.05). Western wheatgrass [Pascopyrum smithii (Rydb.) Löve] and buffalograss (Buchloe dactyloides (Nutt.) Engelm.) composition did not change over time under SLS and 2X-IES, but decreased and increased, respectively, under 3X-IES (P<0.05). Blue grama (Bouteloua gracilis (HBK.) Lag. ex Steud.) and annual grasses displayed initial composition differences (P<0.10) among grazing treatments, but not differential composition shifts over time (P>0.10). Grass and total biomass availability were reduced (P<0.10) over time by 3X-IES. The hypothesis was supported: SLS and 2X-IES were equal in terms of both livestock performance and vegetation responses, but livestock performance and biomass availability were reduced and vegetation composition changed under 3X-IES. Thus, 3X-IES was not sustainable. While SLS and 2X-IES appear biologically equal, using them simultaneously on separate land areas may reduce market variability risk by marketing twice per year.
    • Soil-water and vegetation dynamics through 20 years after big sagebrush control

      Sturges, D. L. (Society for Range Management, 1993-03-01)
      Soil water withdrawal and vegetation characteristics of mountain big sagebrush (Artemisia tridentala ssp. vaseyana Rydb. Beetie) areas sprayed with 2,4-D (2,4-Dichlorophenoxyacetic acid) were measured for 20 years after treatment. Herbaceous productivity more than doubled in the first 3 years after spraying and was still twice as great as untreated vegetation 10 to 17 years after treatment. Sagebrush removal reduced seasonal water depletion 9% to a 1.8-m soil depth, equal to 2.4 cm of water. The entire difference was realized from soil 0.9-1.8 m deep. Depletion from the surface 0.9 m of soil under grass-dominated vegetation slightly exceeded depletion under sagebrush-dominated vegetation. Mathematical relationships were developed that predict the percent reduction in seasonal water depletion in relation to time since sagebrush control for soil depths of 0.0-1.8 m, 0.0-0.9 m, and 0.9-1.8 m. Mountain big sagebrush was a minor vegetation constituent on treated areas 20 years after spraying. Sagebrush density increased from 2,100 to 4,400 plant/ha between 10 and 20 years after spraying while herbaceous production ranged between 28 and 52 kg/ha. Both density and canopy cover of sagebrush on untreated areas declined significantly over the study because of the actions of a snowmold fungus.
    • 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.
    • 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.
    • 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.
    • 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.
    • 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.