• Influence of density on intermediate wheatgrass and spotted knapweed interference

      Velagala, R. P.; Sheley, R. L.; Jacobs, J. S. (Society for Range Management, 1997-09-01)
      Establishing competitive plants is essential for restoring spotted knapweed infested grasslands. Revegetation attempts typically fail becanse of weed competition during the initial stages of establishment. We hypothesized that competitive interactions can be shifted from spotted knapweed to intermediate wheatgrass by increasing wheatgrass seedling density over 1,000 plants m-2. Spotted knapweed and intermediate wheatgrass were grown in addition series mixtures to assess their interference at low (0 to 1,000 plants m-2) versus high (1,000 to 10,000 plants m-2) densities. In the spring of 1995, 7 densities (0, 100, 500, 1,000, 3,000, 6,000, and 10,000 plants m-2) of each species were seeded in a factorial arrangement (49 density combinations) in a randomized-complete-block design and replicated 3 times at 2 sites in Montana. Plants were grown in pots (2,250 mm2 X 380 mm deep) for 60 days before harvesting. Regressions predicting shoot weight, root weight, total weight, leaf area, and root length were calculated using 1) low knapweed:low wheatgrass, 2) low knapweed:high wheatgrass, 3) high knapweed:low wheatgrass, and 4) high knapweed:high wheatgrass densities. Regression coefficients indicated intraspecific interference was most important in predicting intermediate wheatgrass weight at both sites. At the wet site (457 mm, annually), interspecific interference only occurred at high spotted knapweed densities. At the dry site (305 mm, annually), interspecific interference occurred at low densities. Increasing intermediate wheatgrass from low to high densities removed the effect of spotted knapweed on intermediate wheatgrass where interspecific interference occurred.
    • Influence of nitrogen on antelope bitterbrush seedling establishment

      Young, J. A.; Clements, C. D.; Blank, R. R. (Society for Range Management, 1997-09-01)
      Nitrogen enrichment, immobilization, or inhibition of nitrification were used to investigate the influence of available nitrogen on the seedling recruitment of antelope bitterbrush (Purshia tridentata [Pursh] DC) and annual grass competition. The influence of nitrogen enrichment on antelope bitterbrush seedling recruitment depended on the form of nitrogen applied. Ammonium sulfate applications markedly enhanced growth of herbaceous annuals resulting in the loss of all antelope bitterbrush seedlings the first growing season. Enrichment with calcium nitrate marginally enhanced growth of herbaceous annuals and enhanced the growth of antelope bitterbrush seedlings. Immobilization of nitrogen with carbon (sucrose) applications suppressed the growth of herbaceous annuals and produced large, vigorous antelope bitterbrush seedlings. Similar results were obtained by inhibiting nitrification with applications of nitrapyrin or combining nitrapyrin and carbon applications.
    • Long-term soil nitrogen and vegetation change on sandhill rangeland

      Berg, W. A.; Bradford, J. A.; Sims, P. L. (Society for Range Management, 1997-09-01)
      The effect of livestock grazing on organic and N in rangeland soils is not well defined. In this study on sandy rangeland in western Oklahoma, we sampled 8 pastures moderately grazed by cattle and 8 adjacent exclosure ungrazed by livestock for 50 years. The sagebrush was largely controlled by herbicide in the study areas. The C and N concentrations in the surface 5 cm of soil, total herbage production, and total N uptake by were similar (P > 0.05) in grazed and nongrazed area. Carbon and N concentrations in soils sampled to a constant mass to a depth of 5 cm or less were not (P > 0.05) different from concentrations determined on soil sampled to a constant depth of 5 cm. When calculated on a content basis, grazing increased (P < 0.001) the bulk density (1.35 g cm-3) compared to nongrazed pastures (1.19 g cm-3) and had a significant (P < 0.01) effect on C and N in the surface 5 cm of soil. Litter and total N in liter were greater (P < 0.01) on nongrazed areas. Little bluestem (Schizachyrium scoparium (Michx.) Nash) and sand bluestem (Andropogon hallii Hack.) produced more herbage and had greater frequency on nongrazed areas, whereas blue grama [Bouteloua gracilis (H.B.K.) Lag. ex Griffiths], sand dropseed [Sporobulus cryptandrus (Torr.)Gray], and western ragweed (Ambrosia psilostachya DC.) increased in frequency on grazed areas. Thus, 50 years of moderate grazing by cattle had no measurable effect on C and N concentrations in the surface 5 cm of the sandy soil or on total N uptake by plants compared with nonograzed areas; however, significant differences occurred in species composition which may alter mechanisms of C and N balance.
    • Protein quality of cottontail rabbit forages following rangeland disturbance

      Pietz, D. G.; Lochmiller, R. L.; Leslie, D. M.; Engle, D. M. (Society for Range Management, 1997-09-01)
      Seasonal changes in the botanical composition of diets and protein quality of forages consumed by cottontail rabbits (Sylvilagus floridanus) were monitored on disturbed and undisturbed upland hardwood forest-tallgrass prairies in central Oklahoma. Our primary objective was to evaluate the seasonal dynamics of levels of selected amino acid nutrients in forages required for maintenance, growth, or reproduction, and explore bow these changes respond to habitat disturbance resulting from the use of herbicides and fire. Microhistological analyses of stomach digesta indiccated that summer diets were dominated by Panicum oligosanthes Schultes, Croton spp. and Sporobolus asper (Michx.) Kunth; winter diets were dominated by Bromus spp., P. oligosanthes, and Antennaria spp. Differences in the botanical composition and quality of diets between disturbed and undisturbed habitats were of little biological significance. Changes in the concentration of essential amino acids due to plant maturity were minimal in both summer and winter. Estimated levels of nitrogen and essential amino acids in reconstructed diets (based on food habits) appeared to be low, especially for the sulfur-containing amino acids (methionine + cystine) in summer.
    • Stocking rate risk for pasture-fed steers under weather uncertainty

      Parsch, L. D.; Popp, M. P.; Loewer, O. J. (Society for Range Management, 1997-09-01)
      A biophysical model, GRAZE, is used to simulate beef forage performance for stocker steers pastured on common bermudagrass. Eight alternative stocking rates, ranging from low to high grazing intensity, are simulated over 14 simulated over 14 "states of nature" using historical weather data. The impact of weather variability on animal weight gain and economic performance is assessed and empirical cumulative distributions of net returns are developed. The risk efficient stocking rate strategies are identified for alternative decision-maker risk using generalized stochastic dominance. Under improved pasture conditions in Arkansas, results show that (a) expected weight gain per head is largely independent of grazing intensity until a critical stocking rate (6 hd/ha) is attained; (b) the highest expected net return per hectare is achieved under a lower stocking rate rate (10 hd/ha) than one which results in highest expected weight gain per hectare (12 hd/ha); and, (c) an increase in the stocking rate is accompanied by greater production (weather) risk which is reflected in increased variance of weight gain and net returns as well as a higher frequency and magnitude of economic losses.
    • Toxic alkaloid concentration in tall larkspur species in the western U.S

      Ralphs, M. H.; Manners, G. D.; Pfister, J. A.; Gardner, D. R.; James, L. F. (Society for Range Management, 1997-09-01)
      Larkspur (Delphinium spp.) kills more cattle on mountain rangelands in the western U.S. than any other plant, disease or predator. The concentration of toxic alkaloids was measured in 4 larkspur species, at 10 locations, at 2-week intervals during the growing season. In addition, multi-year samples from previous studies were analyzed to determine year-to-year variation in toxic alkaloids. Mountain larkspur (D. glaucum Wats.) had the highest concentration of toxic alkaloids averaged over growth stages (1.01% of dry weight), tall, (D. barbeyi (L.) Huth) and waxy larkspur (D. glaucesens Rydb) were intermediate (0.65 and 0.49% respectively), and duncecap (D. occidentale S. Watts) was lowest (0.29%). Toxic alkaloid concentration generally declined as the plants matured. However, toxic alkaloids in tall larkspur at Yampa, Colo. increased slightly in the pod stage, and toxic alkaloids in waxy larkspur increased from the vegetative to the bud stage. Concentration of toxic alkaloids in tall and duncecap larkspur leaves were higher in plants growing in open sunlight than those shaded under aspen or conifer canopy. Toxic alkaloid concentration varied among individual plants (C.V. 20-60%). Knowledge of the toxic alkaloid concentration of larkspur populations can be used to predict the risk of larkspur poisoning.
    • Viewpoint: Implications of participatory democracy for public land planning

      Moote, M. A.; McClaran, M. P. (Society for Range Management, 1997-09-01)
      Non-traditional, collaborative public park approaches such as coordinated resource management have been proposed to improve the public participation process used in public land planning on rangelands. Either implicitly or explicitly, most advocates of such non-traditional approaches to public participation seem to embrace a participatory democracy model of governance. Whether or not this model for decision-making can practicably be implemented, given our current institution and leaal frameworks for public lands management, has not been closely examined. Criticisms of the traditional public participation process are catagorize into 5 main issues: efficacy; representation and access; information exchange and learning; continuity of participation; and decision-making authority. We use these categories to evaluate the feasibility of implementing participatory democracy-based decision-making in public lands planning. Although there is some statutory and regulatory authority for participatory democracy in public land planning, there are a number of logistical, legal, and even philosophical challenges to its application that warrant further consideration.
    • Viewpoint: On rangeland carrying capacity

      Roe, E. M. (Society for Range Management, 1997-09-01)
      A new typology shows that the notion of rangeland carrying capacity has considerable ambiguity even under conditions of high environmental certainty. When these environmental conditions are highly uncertain, rangeland carrying capacity must be reconceived as a Hahn equilibrium in order to be useful for rangeland development and management. A Hahn equilibrium is a state of affairs which does not cause decision-making agents to change the (meta-)-theories which they hold or the (meta-)-policies which they pursue in their decision-making.
    • Viewpoint: The black-tailed prairie dog—headed for extinction?

      Wuerthner, G. (Society for Range Management, 1997-09-01)
      The black-tailed prairie dog (Cynomys ludovicianus) is 1 of 5 western prairie dog species, and the only species found on the Great Plains. Some authorities believe the black-tailed prairie dog may have been the most numerous of mammalian herbivores found on the plains with some estimates placing their historic numbers as high as 5 billion. Due to a combination of factors including habitat destruction, hunting, plague, and poisoning programs, the black-tailed prairie dog may now be threatened with extinction across its entire range. In this paper, a tentative prairie dog conservation strategy consisting of core reserves, buffer areas, and corridors is proposed.