• Female-biased herbivory in fourwing saltbush browsed by cattle

      Cibils, A. F.; Swift, D. M.; Hart, R. H. (Society for Range Management, 2003-01-01)
      Female fourwing saltbush (Atriplex canescens Pursh [Nutt.]) shrubs are more abundant in exclosures than in adjacent grazed pastures at our research site on the shortgrass steppe in Colorado. We hypothesized that female shrubs at this site were being browsed more heavily by cattle than were male shrubs. We conducted a series of 2-year experiments (1997 and 1998) with cattle to measure levels of cattle utilization of male and female shrubs. Overall, utilization of marked leaders was 43.5% in January, 19.7% in April, and 33.4% in September. Percent utilization of marked leaders was consistently and significantly higher on female shrubs both in January (females: 46.5%, males: 40.2%), and September (females: 36.9%, males: 29.9%). In April, differences in utilization of shrub sexes were not significant (females: 20.3%, males: 19.2%). The female-bias in cattle herbivory increased significantly with increasing overall utilization of shrubs. Gender-biased herbivory may have promoted higher mortality among female shrubs, leading to the sex ratio alteration previously observed at this site.
    • In vivo digestibility of kleingrass from fecal nitrogen excretion

      Ferri, C. M.; Stritzler, N. P.; Brizuela, M. A.; Petruzzi, H. J. (Society for Range Management, 2003-01-01)
      It was proposed that the digestibility of organic matter (OMD) can be estimated from the relationship between total fecal nitrogen (TFN, as a % of organic matter intake (OMI) and fecal nitrogen concentration (FNc) through the equation: OMD = 1 - TFN/FNc. Two assumptions are critical to this equation, total fecal nitrogen (as a % of OMI) is a constant and does not change within a range of diet crude protein and fecal nitrogen concentration is proportional to digestibility of organic matter. The objective of this study was to test if total fecal nitrogen (as a % if OMI) remains constant over 3 feeding levels, and if fecal nitrogen concentration decreases with decreasing organic matter digestibility of maturing forages. Total fecal nitrogen did not change (P = 0.94) with feeding level, but increased (P < 0.05) with evaluation period. The fecal nitrogen concentration correlated (r = 0.60, P < 0.001) to digestibility of organic matter. The results show that digestibility of organic matter cannot be estimated from total fecal nitrogen, unless time of year is considered.
    • Lessons in developing successful invasive weed control programs

      Anderson, G. L.; Delfosse, E. S.; Spencer, N. R.; Prosser, C. W.; Richard, R. D. (Society for Range Management, 2003-01-01)
      The development of successful regional or national invasive weed control programs is often hampered by the way the problem is approached. Typically weed control programs are developed and evaluated solely from the perspective of the biological sciences. While this is appropriate from a local or landscape perspective, it will probably not produce the desired results when addressing widespread well-established infestations that impact large regions. The "Ecological Area-wide Management (TEAM) of Leafy Spurge" program was the first U.S. Department of Agriculture (USDA), Agricultural Research Service (ARS) area wide invasive weed program. The 5-year program, funded by the ARS and conducted cooperatively with the USDA Animal and Plant Health Inspection Service, focused on the control of leafy spurge (Euphorbia esula L.) in North Dakota and South Dakota, Montana and Wyoming. Now in its final year (2001), the TEAM Leafy Spurge program has made significant progress in controlling leafy spurge, increasing public awareness of the problem and demonstrating the effectiveness of biologically-based integrated pest management. While this is a significant accomplishment, the lessons learned over the course of the project clearly demonstrate that the success of regional weed control programs depends on more than a persistent, marked reduction in the pest population. Effective regional weed control programs need to focus not only on biological issues, but also on the ecological, scientific, economic, social and legal factors that influence the effectiveness of the program. Therefore, the implementation and subsequent evaluation of a weed control program must include all the principal factors that will ultimately determine success and sustainability. This manuscript outlines the history of leafy spurge on the North American continent, the situation currently facing weed managers, and an evaluation of the TEAM Leafy Spurge program's success for each factor listed above. The final analysis indicates that successful biologically-based leafy spurge control is on the horizon, especially when weed managers understand the number of problem areas that must be addressed to achieve a sustained reduction of a weed population. The amount of time it will take to be realized depends on our commitment to solving the problem and our willingness to work together as a cohesive team.
    • Prescribed fire effects on erosion parameters in a perennial grassland

      O'Dea, M. E.; Guertin, D. P. (Society for Range Management, 2003-01-01)
      A 2-year field experiment was undertaken to quantify the interacting effects of a late-spring prescribed burn and summer rainfall on seasonal runoff and erosion in a southern Arizona grassland. Six blocks with walled subplots (n = 24) were installed on a hillslope to measure changes to plant, soil, and hydrologic variables in response to treatments. Increased bulk density, erosion, and runoff volumes; and lowered plant cover and water intake rates were observed within the burned plots following the first summer season. In the second year, higher bulk density, runoff volumes, and erosion measures were again observed within the burned plots, as well as lower plant cover, aggregate stability, and water intake rates. The results of this study indicate that following late-spring burning, semi-desert grasslands are susceptible to greater summer runoff and erosion compared to unburned grasslands.
    • Understory species response to Utah juniper litter

      Horman, C. S.; Anderson, V. J. (Society for Range Management, 2003-01-01)
      A greenhouse study was conducted to determine the effects of litter leachate and litter depth of Utah juniper [Juniperus osteosperma (Torr.) Little] on seedling emergence and emergence rate of 8 common herbaceous understory species. Species tested were: ‘Secar’ bluebunch wheatgrass [Pseudoroegnaria spicata (Pursh) A. Love], bottlebrush squirreltail [Elymus elymoides (Raf.) Swezey], cheatgrass (Bromus tectorum L.), ‘Paiute’ orchardgrass (Dactylis glomerata L.), ‘Appar’ Lewis flax (Linum lewisii Pursh), ‘Delar’ small burnet (Sanguisorba minor Scop.), antelope bitterbrush [Purhsia tridentata (Pursh) DC.], and mountain big sagebrush [Artemisia tridentata spp. vaseyana (Rydb.) J. Boivin]. Three water treatments (distilled water, 1%, and 10% litter leachates) and 3 litter depths (0, 3, and 5 cm) were tested. Leachates decreased seedling emergence of orchardgrass and small burnet. Emergence rate was unaffected by leachate treatments. Seedling emergence of all species tested decreased significantly with increasing litter depth. Emergence rate was initially slower in pots with litter, but after 2 weeks no differences were found.
    • Vegetation of chained and non-chained seedlings after wildfire in Utah

      Ott, J. E.; McArthur, E. D.; Roundy, B. A. (Society for Range Management, 2003-01-01)
      After wildfires in 1996 in the sagebrush (Artemisia spp.) and pinyon-juniper (Pinus spp.–Juniperus spp.) zones of west-central Utah, the USDI-BLM attempted to reduce soil erosion and cheatgrass proliferation (Bromus tectorum L.) through rehabilitation treatments. We compared the vegetation of aerially seeded, chained treatments with aerially seeded but non-chained treatments for 3 years following seeding. Vegetation cover increased significantly in both treatments between the first and second year, concurrent with above-average precipitation. By the second year, seeded grasses, primarily crested wheatgrass [Agropyron cristatum (L.) Gaertn.] and intermediate wheatgrass [Elymus hispidus (Opiz) Meld. and Elymus elongatus (Host) Runem.], dominated the chained treatment while cheatgrass dominated the non-chained treatment. Seeded grass establishment in non-chained areas was highest beneath dead trees on steep northeast-facing slopes. The first year following the fires, frequency of most annual species and some native perennial species was higher in the non-chained than chained treatment. Native species richness and diversity declined in both treatments between the first and third year following the fires due to the loss of early-seral native annuals and probably because of climatic factors and competition from seeded grasses and cheatgrass. This study reaffirmed the utility of aerial seeding followed by chaining as a rehabilitation technique for rapid establishment of standard plant materials and suppression of cheatgrass, although the implications for soil protection were less clear. Maintenance of native biodiversity on public lands will require greater development and use of native plant materials for wildfire rehabilitation. Planning for future rehabilitation needs is important in light of continuing wildfire risks.