• Broom snakeweed control and seed damage after herbicide applications

      McDaniel, K. C.; Wood, B. L.; Murray, L. (Society for Range Management, 2002-11-01)
      Broom snakeweed (Gutierrezia sarothrae [Pursh] Britt. Rusby) is a major weed problem in the southwestern U.S. because it is toxic to livestock and suppresses forage productivity. In this study, broom snakeweed control, seed production and viability were determined after broadcast spraying in 1997 and 1998 with metsulfuron ({2-[[[[(4-methoxy-6-methyl-1,3,5-triazin-2-yl) amino]carbonyl]amino]sulfonyl]benzoic acid}; 0.03 kg a.iha-1) and picloram ((4-amino-3, 4, 6-trichloro-2-pyridine-carboxylic acid); 0.28 kg a.iha-1). In 1997, plants were sprayed every 2 weeks beginning 1 October when snakeweed was in mid-flower and seed fill and continued until 15 December when seeds were being dispersed. Broom snakeweed control was not different by spray date and averaged 98% with picloram and 77% with metsulfuron. Only plants sprayed on 1 October 1997 with either herbicide had significantly less seed viability than nonsprayed plants, but seed production was not different. In 1998, herbicide applications were repeated at 2 week intervals for 6 weeks beginning on 1 September when snakeweed was in early-flower and seed development. Broom snakeweed control with picloram (average 88%) was consistently high across all spray dates, whereas, control with metsulfuron (average 25%) was always poor. Both herbicides reduced seed production by an average of 99, 95, and 38% when applied on 1 and 15 September 1998 and 1 October 1998, respectively, but seed production was not different among sprayed and nonsprayed plants after these dates. In the spring of 1999, broom snakeweed seedlings were common in all areas previously sprayed in 1997, but few seedlings established in plots sprayed in 1998. In the spring of 2001, the number of newly emerged broom snakeweed seedlings observed in nonsprayed and herbicide-treated areas was the same, irrespective of spray year, herbicide type or date applied. Data indicate that herbicide applications made at flower when seed is in early fill can provide satisfactory plant control and lower seed production. Spraying after seed has reached physiological maturity does not affect seed production or viability. In this study, results were inconclusive for determining if timed herbicide applications in autumn can be used to minimize later broom snakeweed establishment.
    • Grazing intensity impacts on pasture carbon and nitrogen flow

      Baron, V. S.; Mapfumo, E.; Dick, A. C.; Naeth, M. A.; Okine, E. K.; Chanasyk, D. S. (Society for Range Management, 2002-11-01)
      There is little information on the impact of grazing intensity on productivity and sustainability of intensively managed pastures in the humid, short-season parkland of the Canadian prairies. Our hypothesis was that above-ground productivity of dry matter, carbon, nitrogen, and in vitro digestible organic matter would be reduced proportionately with increasing grazing intensity. The study was conducted on a Typic Haplustoll at Lacombe, Alberta. Paddocks of meadow bromegrass (Bromus riparius Rhem.), replicated 4 times, were subjected to heavy, medium and light grazing intensities. Measurements and analyses were carried out for 3 years. Yields of dry matter, carbon, nitrogen, and in vitro digestible organic matter before and after grazing were determined and seasonal pools of above ground production, disappearance and residual were calculated. Concentrations of acid and neutral detergent fiber and lignin were also determined before and after grazing. Increasing grazing intensity tended to increase nitrogen and decrease fiber concentrations for available and residual forage. Heavy and medium grazing intensities produced 83 and 90% as much above ground dry matter and 87 and 90% above ground carbon as the light intensity. All disappearance pools were similar among grazing intensities except in vitro digestible organic matter, where heavy was 116% of light. Heavy grazing reduced the contribution of vegetative dry matter, in vitro digestible organic matter, carbon and nitrogen to the residual to 41, 50, 36, and 52% of that for light grazing. Adding estimated fecal-carbon to the residual significantly increased total residual carbon. Estimated fecal-carbon represented 68, 51, and 42% of all carbon inputs to litter for heavy, medium and light grazing, respectively. Grazing intensity did not affect estimated pools of excreted nitrogen, but increased estimated precent of nitrogen excreted as urine.
    • Hydrologic response of diverse western rangelands

      Pierson, F. B.; Spaeth, K. E.; Weltz, M. A.; Carlson, D. H. (Society for Range Management, 2002-11-01)
      There are several generalizations or assumptions concerning rangeland hydrology and erosion relationships found in the literature and in the management arena. These generalizations have found their way into rangeland models, where modelers have assumed that diverse rangeland types can be lumped or averaged together in some way to develop one algorithm or equation to describe a process or relationship across the entire spectrum of rangeland types. These assumptions and modeling approaches based on the universal concept may not be appropriate for diverse rangeland types. This paper presents a comprehensive data set of vegetation, soils, hydrology, and erosion relationships of diverse western rangelands, and utilizes the data to assess the validity of the various assumptions/generalizations for rangelands. The data set emphasizes the difficulty in understanding hydrologic responses on semiarid rangelands, where the relationship between plant/soil characteristics and infiltration/erosion is not well established. When all sites were pooled together, infiltration and sediment production were not correlated with any measured vegetation or soil characteristic. A myriad group of factors determine infiltration and erosion, and is dependent on rangeland type and site conditions. The infiltration and erosion responses and correlation/regression analyses presented highlight the risk of using generalized assumptions about rangeland hydrologic response and emphasize the need to change the current modeling approach. Universal algorithms to represent the response of all rangeland types, such as the pooled multiple regression equations presented, will not provide sufficient accuracy for prediction or assessment of management. We need to develop a rationale to organize rangeland types/vegetation states according to similarities in relationships and responses. These functional rangeland units would assist in the development of more accurate predictive equations to enhance model performance and management of rangelands.
    • Influence of grazing on channel morphology of intermittent streams

      George, M. R.; Larsen, R. E.; McDougald, N. K.; Tate, K. W.; Gerlach, J. D.; Fulgham, K. O. (Society for Range Management, 2002-11-01)
      Alteration of stream channel morphology by cattle and associated streambank erosion is a concern on rangeland watersheds. The objective of this study was to determine changes in stream channel morphology in response to 5 grazing treatments applied to 0.4 ha pastures and replicated on 3 intermittent streams at the San Joaquin Experimental Range in the central Sierra Nevada foothills of California. Baseline stream channel morphology parameters were determined along 10 transects in each pasture in June 1994. Seasonal grazing treatments (no grazing, wet season moderate, wet season concentrated, dry season moderate, and dry season concentrated) were repeated annually over 4 years beginning in July 1994. Stream channel morphology parameters were measured annually from 1995-1998. When stream morphological responses were averaged across years, there were no detectable effects of grazing on the parameters measured. Year effects and their interaction with grazing were significant, primarily for stream morphological parameters that included channel depth in their measurement or calculation. Channel depth increased significantly in the ungrazed controls, but did not change due to any grazing treatment. These results indicate that grazing had little effect on the morphology of these bedrock limited, intermittent stream channels.
    • Polyethylene glycol affects goats' feeding behavior in a tannin-rich environment

      Landau, S. Y.; Perevolotsky, A.; Kababya, D.; Silanikove, N.; Nitzan, R.; Baram, H.; Provenza, F. D. (Society for Range Management, 2002-11-01)
      High concentrations of condensed tannins in browse impair brush clearing by goats. We studied the effect of polyethylene glycol (PEG, MW 4000), a polymer that binds condensed tannins, on the feeding behavior of Damascus goats (Capra hircas) on a range dominated by tannin-rich lentisk (Pistacia lentiscus L.). This was done with or without a nutritious alternative to browse (alfalfa hay) available at pasture. In phase 1, no hay was provided to goats; in phase 2, hay was distributed daily in the field. In both phases, 6 goats had free access to PEG while at pasture, while 6 goats that grazed separately on another paddock did not. All goats received each night an allowance of concentrate (400 g day-1 of 40% ground corn grain, 40% ground barley, 17% soybean meal and 3% of a mineral-vitamin premix, and contained as fed 16% crude protein (CP) and 2.66 Mcal kg-1 of Metabolizable Energy). The 2 groups of goats alternated daily between paddocks. Goats supplemented with PEG spent more time browsing lentisk than goats in the control group (73 and 41%, respectively, P < 0.0001). Goats in the control group spent more time foraging on dry grasses than their PEG-fed counterparts (28 and 12%, respectively, P < 0.0001). Goats from the PEG group gained body weight at a higher rate than controls. The daily intake of PEG was 450 g, with an intake rate of 1.2 g sec-1. Supplemental alfalfa hay substituted partly for dry grasses in goats' diets, but did not modify the percent of time goats in either treatment spent browsing lentisk. Our data suggest that PEG has the potential to increase intake of tannin-rich species, even where alternative fodder of better nutritional quality is present. However, self-feeding of PEG may not be the best way to provide PEG because goats may ingest more PEG than needed to annul the aversive effects of tannins on food intake.
    • Predicting plant community response to picloram

      Kedzie-Webb, S. A.; Sheley, R. L.; Borkowski, J. J. (Society for Range Management, 2002-11-01)
      Effective rangeland weed programs require the ability to predict plant community responses to management. Our objective was to develop regression equations to predict the plant community after control with picloram using the pre-treatment plant community. Five transects were established from dense spotted knapweed (Centaurea maculosa Lam.) in the center of each patch to an area of low or no spotted knapweed occurrence on the outside of the patch. Transects ended in areas dominated by Idaho fescue (Festuca idahoensis Elmer). Twenty permanent plots (20 x 50 cm, spacing along the transect ranged from 1/2 to 2 m) were placed along this gradient. Pre-treatment density and cover of all species were sampled in each plot. Biomass of all species was harvested in plots adjacent to the transect. Picloram (4-amino-3,5,6-trichloropicolinic acid) was applied along each transect at a rate of 0.28 kg a.iha-1 in October 1996 to each plot. Density, cover, and biomass of all species were re-sampled in August 1998. Regression models were fit using perennial grasses, Idaho fescue, forbs, species richness, and species diversity after treatment as predicted variables. All predicted variables were indigenous species. Regressor variables used were site, transect, and spotted knapweed, a spotted knapweed quadratic component, indigenous perennial grasses, Idaho fescue, indigenous forbs, species richness, and species diversity sampled in the first year (1996) prior to treatment. The best predictive models for assessing post-management indigenous perennial grass, Idaho fescue, and species richness were based on density. The best models predicting post-management forbs and species diversity were based on cover and biomass, respectively. In 4 out of the 5 models, for a given post-management parameter, an important predictor in the model was its pre-management regressor variable. Additionally, pre-management spotted knapweed was a relatively unimportant preditar in most models. The model predicting species diversity based on density (pre-treatment) predicted an increase in species diveristy 2 years after management. This study indicated that it may be feasible to use pre-management spotted knapweed was a relatively unimportant predictor in most models. The model predicting species diversity based on density (pre-treatment) predicted an increase in species diversity 2 years after management. This study indicated that it may be feasible to use pre-management plant community data to predict post-management plant community response for spotted knapweed-infested rangeland using picloram.
    • Rangeland health attributes and indicators for qualitative assessment

      Pyke, D. A.; Herrick, J. E.; Shaver, P.; Pellant, M. (Society for Range Management, 2002-11-01)
      Panels of experts from the Society for Range Management and the National Research Council proposed that status of rangeland ecosystems could be ascertained by evaluating an ecological site's potential to conserve soil resources and by a series of indicators for ecosystem processes and site stability. Using these recommendations as a starting point, we developed a rapid, qualitative method for assessing a moment-in-time status of rangelands. Evaluators rate 17 indicators to assess 3 ecosystem attributes (soil and site stability, hydrologic function, and biotic integrity) for a given location. Indicators include rills, water flow patterns, pedestals and terracettes, bare ground, gullies, wind scour and depositional areas, litter movement, soil resistance to erosion, soil surface loss or degradation, plant composition relative to infiltration, soil compaction, plant functional/structural groups, plant mortality, litter amount, annual production, invasive plants, and reproductive capability. In this paper, we detail the development and evolution of the technique and introduce a modified ecological reference worksheet that documents the expected presence and amount of each indicator on the ecological site. In addition, we review the intended applications for this technique and clarify the differences between assessment and monitoring that lead us to recommend this technique be used for moment-in-time assessments and not be used for temporal monitoring of rangeland status. Lastly, we propose a mechanism for adapting and modifying this technique to reflect improvements in understanding of ecosystem processes. We support the need for quantitative measures for monitoring rangeland health and propose some measures that we believe may address some of the 17 indicators.
    • Research observation: Desert bighorn sheep diets in northwestern Sonora, Mexico

      Tarango, L. A.; Krausman, P. R.; Valdez, R.; Kattnig, R. M. (Society for Range Management, 2002-11-01)
      We used microhistological analyses of fresh fecal pellets to determine seasonal diets of desert bighorn sheep (Ovis canadensis mexicana Merriam 1901) in northwestern Sonora, Mexico from April 1997 to December 1998. We identified 41 plant species (22 browse, 10 forbs, 5 grasses, and 4 succulents) in diets of bighorn sheep. We found no differences between diets of males and females, and diet diversity between sexes was similar (P 0.05). Diet included: browse (45.7%), forbs (32.0%), succulents (17.8%), and grasses (4.5%). The consumption of succulents was higher during spring, decreased during summer, increased in autumn, and decreased in winter. Consumption of forbs was higher during winter and summer. Globemallow (Sphaeralceae spp.), desert agaves (Agave spp.), range ratany (Krameria parvifolia Benth.), buck-wheatbrush (Eriogonum spp.), foothill palo verde (Cercidium microphyllum [Torrey] Rose Johnst.), Engelmann prickly pear (Opuntia engelmanii Salm-Dyck), desert ironwood (Olneya tesota A. Gray), and elephant tree (Bursera microphylla A. Gray) were consumed throughout the study. As biologists identify potential release sites for restoration of bighorn sheep in Mexico, studies of diet composition will provide managers with information for successful translocations.
    • Selected factors affecting seedling recruitment of dalmatian toadflax

      Grieshop, M. J.; Nowierski, R. M. (Society for Range Management, 2002-11-01)
      Seedling recruitment of Dalmatian toadflax, (Linaria genistifolia ssp. dalmatica (L.) Maire and Petitmengin (Scrophulariaceae)), was examined in a 2-year field study in Montana using overseeding and plant/insect exclusion methods, to determine whether it was more limited by seed availability or interspecific plant competition. Overseeding test plots with toadflax seed had no effect on seedling recruitment. Exclusion of plant competition (via herbicide application and pruning) significantly increased total, and cumulative seedling recruitment of Dalmatian toadflax on the last sampling date in 3 of 4, and 2 of 4 cases examined, respectively. Insect exclusion (via insecticide application) significantly increased total seedling recruitment of Dalmatian toadflax on the last sampling date in only 1 of 4 cases examined, and had no effect on cumulative seedling recruitment of Dalmatian toadflax on the last sampling date. We conclude that seedling recruitment in Dalmatian toadflax was more strongly influenced by plant competition than herbivory in our study. Hence, microsite limitation (i.e., competition for "safe sites for germination") rather than seed limitation appears to play a more important role in toadflax seedling recruitment. In light of this, current biological control agents that impact seed production will likely have minimal capabilities of influencing toadflax density. Thus, a premium should be placed on establishing biological control agents that are able to cause significant damage to the stem and root system of Dalmatian toadflax, and in maintaining a healthy plant community that, through interspecific competition, will negatively affect toadflax seedling recruitment.
    • Stocking rate and cow-calf production on sand sagebrush rangeland

      Gillen, R. L.; Sims, P. L. (Society for Range Management, 2002-11-01)
      Stocking rate is generally considered to be the most important management factor in sustainable grazing of Great Plains grasslands over management periods of 10 to 20 years or longer. Most studies to determine optimum stocking rates have compared only 2 or 3 discrete stocking rates. Our objective was to determine cow, calf, and economic performance on sand sagebrush (Artemisia filifolia Torr.) rangeland as a continuous function of stocking rate. Replicated stocking rates of 0.11, 0.15, and 0.22 head ha-1 were studied over an 8-year period. Cow weight declined as stocking rate increased in drought years but was not affected by stocking rate in wetter years. Weaning percentage was not affected by stocking rate but variation within treatment groups was high. Calf birth weight and weaning weight both declined as stocking rate increased. Comparing 0.11 and 0.22 head ha-1, calf production cow-1 declined from 206 to 144 kg cow-1 as stocking rate increased but calf production ha-1 increased from 22.6 to 31.7 kg calf ha-1. Net returns were maximized at 7.87 ha-1 year-1 at a stocking rate of 0.172 head ha-1, well within the range of experimental treatments. Net returns were within 5% of maximum between stocking rates of 0.156 and 0.183 head ha-1. The variability of all responses increased as stocking rate increased. Simulation indicated that improved livestock prices and increased animal productivity shifted the economic optimum stocking rate to higher levels, which would put more pressure on the conservation ethic of land managers.
    • The relationship between climate and Rothrock sagebrush colonization patterns

      Bauer, K. M.; Berlow, E. L.; D'Antonio, C. M. (Society for Range Management, 2002-11-01)
      In montane meadows of the southern Sierra Nevada mountains (Calif., USA), Rothrock sagebrush (Artemisia rothrockii G.) has expanded into sites once dominated by herbaceous species. We explored the relationship between climate and shrub establishment by estimating Rothrock sagebrush age distributions from growth rings. We compared these age distributions with annual records of spring snowpack and summer precipitation across 4 vegetation types that differed in water table depth, soil moisture, and vegetation cover. In the 2 vegetation types where the water table is consistently deeper than 1 m, Rothrock sagebrush stands were up to 40 years old and had relatively even age structures that showed no strong relationship to climate. In the 2 vegetation types with a shallow water table - but with contrasting soil moisture and herbaceous cover - the majority of shrubs colonized synchronously between 1984 and 1994, a relatively dry period that followed the wet 1982 to 1983 El Niño. These and other published data suggest that initial shrub colonization of new sites is facilitated by wet years, which may increase seed production, germination, and seedling survival. However, once sagebrush stands are established and local seed supply is abundant, its continued recruitment seems independent of climate.
    • Viewpoint: Improving range science through the appropriate use of statistics

      Gould, W. R.; Steiner, R. L. (Society for Range Management, 2002-11-01)
      We examined a stratified random sample of articles published over 3 decades of the Journal of Range Management to study the applications and changes in statistical methodology employed by range scientists. Our objectives were to characterize the philosophical nature of statistics use in range science and to identify strengths and weaknesses inherent in these approaches. In each article, we examined the research design efficacy and whether the statistical analysis was adeptly used to convey the relevant information. The majority of articles we examined were conducted appropriately. In general, we found more emphasis has been placed on statistical testing than effect size estimation in the last decade. On an average, 82 tests or means comparisons (s.e. = 20) were presented in each article during the 1990's. Articles that reported an effect size via a sample mean frequently did not report an associated standard error. Research designs lacked adequate descriptions in several cases, making it difficult to determine if the appropriate analysis was performed. Improper identification of the experimental or sampling unit and/or the interdependence of observations occurred in all decades. We recommend increased inferential use of confidence intervals and suggest that the practical significance (as opposed to statistical significance) of results be considered more often. Improvements in the 'science' of range science can be made by greater understanding and communication of statistical concepts through consultation with statisticians.
    • Viewpoint: The ecological value of shrub islands on disturbed sagebrush rangelands

      Longland, W. S.; Bateman, S. L. (Society for Range Management, 2002-11-01)
      Undisturbed plant communities dominated by shrubs or trees are often left isolated within landscapes otherwise devoid of woody vegetation following large-scale disturbances such as wildfires. We discuss potential ecological benefits associated with these terrestrial vegetation "islands", giving special attention to islands in disturbed shrub systems dominated by big sagebrush (Artemisia tridentata Nutt.). Shrub habitat islands provide important refugia for plant and animal species that are associates of shrubsf?rom those that generally require shrub cover to those that have evolved obligate symbioses with a particular shrub species. Even if islands are not able to support breeding populations, they may provide essential temporary habitat for maintaining a plant or animal metapopulation or for dispersing animals. Habitat islands are likely to enhance local biological diversity of plants and animals, because they harbor species that are lacking in disturbed areas, and because abrupt structural changes from disturbed to undisturbed vegetation provide a habitat mosaic that facilitates high levels of species turnover. A previous study confirmed that small mammal species richness in sagebrush islands is intermediate to the high species richness in undisturbed sagebrush "mainlands" and the low richness associated with burned sagebrush habitats. In re-analyzing some of the data from the latter study, we found that small mammal richness in sagebrush islands increases with time since the surrounding habitat burned. Finally, habitat islands provide more evenly dispersed seed sources for re-establishment of decimated vegetation within disturbed areas, and they may harbor animal species that provide seed dispersal services. Thus, they should accelerate vegetation recovery after disturbance. Managers, fire crews, and others who may influence how disturbance patterns affect habitat heterogeneity should be aware of these ecological benefits of habitat islands.