• Perspectives and processes in revegetation of arid and semiarid rangelands

      Call, C. A.; Roundy, B. A. (Society for Range Management, 1991-11-01)
      Range revegetation research has been dominated by empirical studies that provide some information about what works or does not work under a given set of conditions, but tell us little or nothing about the underlying ecological processes. Research has emphasized the establishment of vigorous exotic grasses on specific sites rather than the establishment of persistent, biologically diverse plant communities. A more mechanistic research approach is needed to better understand factors governing germination, seedling establishment, and plant community development in natural and synthetic systems to guide revegetation toward biological diversity. This paper evaluates selected aspects of the present knowledge of revegetation science on arid and semiarid lands, and attempts to identify areas for future research direction. Specific concepts and aspects of succession and plant community development, such as seedbed ecology, temporal and spatial patterns of resource availability and use, species life history traits, and species interactions are important areas of research. Continuous measurement of detailed environmental and biological data at the appropriate scale (down to the size of small seeds) will allow development of mechanistic models which can be used to predict plant establishment and community development for different environmental conditions.
    • Plant-animal interactions affecting plant establishment and persistence on revegetated rangeland

      Archer, S.; Pyke, D. A. (Society for Range Management, 1991-11-01)
      The role of ungulate grazing in shaping rangeland ecosystems is well known relative to other important plant-animal interactions such as pollination, seed dispersal, granivory, and belowground herbivory. Successful rangeland revegetation may be enhanced by strategies that favor certain groups of animals and discourage others. Many perennial forbs and shrubs require animals for successful pollination, reproduction, and subsequent maintenance of species on a site; however, pollination biology of many rangeland plants and pollinator abundances at potential revegetation sites are largely unknown. Granivory may be significant in some locations and planning and design of revegetation areas may be improved by implementing principles of seed escape mechanisms, such as predator satiation, seed escape in space (low perimeter-to-area ratio for revegetation site), and seed escape in time (synchronous or staggered timing for nearby revegetation sites). Seedling establishment may be associated with invertebrate population levels which need to be considered in future revegetation projects. Timing and site preparation are important in limiting belowground herbivory. Animals can serve as dispersal agents of seeds. Livestock dosed with desirable seeds can disperse them in their dung across the landscape, thereby creating patches of desirable plants. If revegetation sites will be grazed by livestock, then managers should choose plant species that tolerate rather than avoid grazing and should apply adequate management to establish and maintain plant populations. Seeds inoculated with mutualistic species such as mycorrhizae, nitrogen-fixing bacteria, or actinomycetes may enhance establishment, productivity, and nutrient quality of rangeland species while increasing rates of succession.
    • Plant-plant interactions affecting plant establishment and persistence on revegetated rangeland

      Pyke, D. A.; Archer, S. (Society for Range Management, 1991-11-01)
      Restoration and revegetation of rangeland ecosystems is based on knowledge of abiotic and biotic interactions that affect plant establishment. Once plants become autotrophic, interactions within and between plant species may occur and then interactions may range from antagonistic to mutualistic. This full range of potential interactions needs to be considered to ensure successful revegetation. At the intraspecific level, we propose the development and use of density-yield diagrams for rangeland species. These diagrams would be based on the self-thinning principle, that aboveground biomass is related to plant density and to the dynamic process of density-dependent mortality. The proposed approach would be used to determine optimum seeding rates, and to predict future biomass of revegetated rangeland. At the interspecific level, competitive relationships of species used to reseed rangelands need to be identified to enhance the probability that species will coexist and thereby facilitate greater species diversity on the site. A diversity of species and growth forms may provide a more stable cover and productivity than a monoculture on sites characterized by environmental variability while potentially enhancing nutrient status for the site.
    • Spatial components of plant-herbivore interactions in pastoral, ranching, and native ungulate ecosystems

      Coughenour, M. B. (Society for Range Management, 1991-11-01)
      The spatial component of herbivory remains enigmatic although it is a central aspect of domestic and native ungulate ecosystems. The effects of ungulate movement on plants have not been clearly established in either range or wildlife management. While livestock movement systems have been implemented to cope with increases in livestock density, restrictions on movement, and overgrazing, a large number of studies have disputed the effectiveness of different livestock movement patterns. Traditional pastoralism, particularly nomadism, has been perceived as irrational and even destructive, but many studies have documented features of traditional pastoral land use that would promote sustainability. Disruptions of wild ungulate movements have been blamed for wildlife overgrazing and population declines, but actual patterns and mechanisms of disrupted movement and population responses have been poorly documented. Models that integrate plant growth, ungulate movement, and foraging are suggested as a way to improve analyses of spatial plant-herbivore systems. Models must give due attention to nonforage constraints on herbivore distribution, such as topography. Models should assess the significance of movement as a means of coping with local climatic variation (patchy rainfall). Models that distribute an aggregate population over a landscape in relation to the distribution of habitat features deemphasize aspects of ungulate movements and population responses that inevitably cause nonideal distributions, particularly in natural ecosystems. Individual based models describe movement and foraging processes more accurately, but these models are difficult to apply over large areas. Both top-down and bottom-up approaches to spatial herbivory are needed. To model plant responses to movement, it is important to account for small scale phenomena such as tiller defoliation patterns, patch grazing, and grazing lawns as well as large scale patterns such as rotation and migration. Herbivory patterns at these different scales are interrelated.
    • Sward and steer variables affecting feasibility of electronic intake measurement of grazers

      Forwood, J. R.; Da Silva, A. M. B.; Paterson, J. A. (Society for Range Management, 1991-11-01)
      Forage intake is perhaps the most critical parameter in understanding performance of ruminants on pasture. The Thermal Conductivity Cannula (TCC) is an animal-carried device that measures forage intake without disturbing normal grazing patterns by counting the number of boli swallowed over time. To evaluate its accuracy, studies of the effects of animal size, forage availability, quality, and species differences were conducted. In a grazing study, bolus weights of heavy (533 kg) and light (360 kg) esophageally fistulated steers were monitored on 2 different grazing systems [tall fescue (Festuca arundinacea Shreb) + red clover (Trifolium sp.) season-long vs. tall fescue + red clover in spring and fall and bit bluestem (Andropogon gerardi Vit; cv. Kaw) in summer]. Boli weight differences between steer weights indicated that TCC intake estimation will require calibration for steer weight or use of uniform steers. Boli weights of heavy steers varied (P < 0.05) within (9.0 to 19.4 g) and among (19.4 to 30.2 g) forage species. That did not occur with light steers (average = 6.25). Analysis of data on a metabolic weight basis indicated that size of the oral cavity and the 'critical mass' needed to stimulate swallowing may be a factor as well as weight. Sward characteristics and quality parameters were poorly correlated with bolus weight. An indoor study using 3 steer weights (heavy-546 kg, medium-486 kg, and light-220 kg) fed orchardgrass (100%), alfalfa (100%), and orchardgrass X alfalfa hay (50/50) indicated that heavier steers always produced heavier boli but that the weight differences between steers had to be greater than 86 kg to be significantly different. Light steers produced most consistent boli weights over all feeds.
    • Technical Note: Surgical establishment of esophageal fistulae in suckling calves

      Adams, D. C.; Short, R. E.; Pfister, J. A.; Peterson, K. R.; Hudson, D. B. (Society for Range Management, 1991-11-01)
      Esophageal fistulae were established in five 34-day-old suckling calves by a modified surgical procedure used previously for sheep and goats. After skin incision, the esophagus was exposed by separating the brachiocephalicus and sternocephalicus muscles. A cannula was inserted into the esophagus after a longitudinal incision was made into the lumen of the esophagus. Sutures were not used in the esophagus. The calves recovered quickly with moderate post-operative swelling. We concluded that the surgical procedure was satisfactory and that diets were collected readily and without fistulae shrinkage.
    • The grass seedling: When is it established?

      Ries, R. E.; Svejcar, T. J. (Society for Range Management, 1991-11-01)
      Adventitious roots of sufficient length and diameter must develop to assure that the photosynthetic surfaces receive sufficient water and nutrients before grass seedlings can be considered established. We evaluated development of crested wheatgrass [Agropyron desertorum (Fisch. ex Link) Schult.] and blue grama [Bouteloua gracilis (H.B.K.) Lag.] seedlings in the field to decide when they were established. Blue grams and crested wheatgrass seedlings, under the environmental conditions of this study, were considered established 21 days after emergence. At this time, crested wheatgrass seedlings had 4 leaves, 2 adventitious roots penetrating to a depth of at least 80 mm into the soil, and 1 tiller per plant. Blue grama seedlings had about 6 leaves, 2 adventitious roots penetrating to a depth of at least 100 mm into the soil, and 2 tillers per plant. Most seedlings that reached this stage by the end of the first growing season overwintered and survived the following growing season and provided adequate stands for both species.
    • Use of ornamental lilac and honeysuckle phenophases as indicators of rangeland grasshopper development

      Kemp, W. P.; Berry, J. S.; Caprio, J. M. (Society for Range Management, 1991-11-01)
      Comparisons were made between phenological phase dates of 2 common ornamental shrubs, purple common lilac (Syringa vulgaris L.) and Zabeli honeysuckle (Lonicera krolkowii Stapf, var. Zabelii (Rehd. Rehder)), and rangeland grasshopper (composite of 6 common species) development for 3 years at 9 sites throughout Montana. Results indicated that spring hatch (75% instar 1) occurred about 10 days after the begin bloom phase of purple common lilac. Peak occurrence of grasshoppers for instar 2 coincided, on average, with the end bloom phase of Zabeli honeysuckle, whereas peak instar 3 occurred about 10 days later. On average, peak instar 4 preceded the first red berry phase of Zabeli honeysuckle by about 8 days, and 75% adult stage occurred about 14 days after red berries first appeared. Our results provide rangeland managers and ranchers with a simple method for the improved timing of assessment and control of rangeland grasshoppers.
    • Utilization of larkspur by sheep

      Ralphs, M. H.; Bowns, J. E.; Manners, G. D. (Society for Range Management, 1991-11-01)
      Sheep are more resistent to larkspur (Delphinium spp.) poisoning than are cattle, and may be used as a biological tool to graze larkspur prior to cattle turn-in to reduce the risk of cattle poisoning. Sheep utilization of 3 species of larkspur was measured at 3 phenological growth states (vegetative, bud, and flower) at 5 locations. Utilization of waxy larkspur (D. glaucescens Wats), varied among years at Ruby, Mont. Use of duncecap larkspur (D. occidentals. Wats) at Oakley, Ida., was uniformly higher in all 3 growth stages due to closed herding practices. Use of tall larkspur (D. barbeyi Huth) increased as it matured. Trailing sheep through larkspur patches, or bedding them in patches greatly increased trampling of larkspur stalks and utilization of heads and leaves.
    • Wyoming big sagebrush control with metsulfuron and 2,4-D in northern New Mexico

      McDaniel, K. C.; Anderson, D. L.; Balliette, J. F. (Society for Range Management, 1991-11-01)
      Field experiments conducted between 1982 to 1988 compared 2,4-D [(2,4-dichlorophenoxy)acetic acid] and metsulfuron [2-[[[[(4-methoxy-6-methyl-1,3,5-triazin-2-yl) amino)carbonyl]amino]sulfonyl]benzoic acid) for control of Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis Beetle and Young) in northern New Mexico. Precipitation was near or above normal during years of herbicide applications. Broadcast sprays of 2,4-D at 2.2 kg/ha were most efficacious during rapid shoot elongation, but mortality averaged less than 38% from treatments applied over 4 separate years. Wyoming big sagebrush shoot growth was greatest in April and May compared to other months, but growth was highly variable among shrubs and probably reduced effectiveness of 2,4-D sprays. The optimum application timing for metsulfuron was during the late-flower growth and fruiting stages. Fall-applied metsulfuron at 0.035 kg/ha provided 65% Wyoming big sagebrush mortality compared to 27% when spring-applied. When metsulfuron was fall-applied at 0.07 kg/ha or higher, control averaged 88% following 3 annual applications. Combining metsulfuron at .0175 kg/ha plus 2,4-D at 1.1 kg/ha was comparable to or more effective than either herbicide applied alone in spring or fall. Total standing crop of grasses increased by nearly 300% after 1 or 2 growing seasons when Wyoming big sagebrush canopy cover was reduced by at least 75% following herbicide treatments.