• Cheatgrass competition and establishment of desert needlegrass seedlings

      Rafferty, D. L.; Young, J. A. (Society for Range Management, 2002-01-01)
      Desert needlegrass (Achnatherum speciosum [Trin. Rupr.] Barkworth) is potentially a valuable native species for use in restoration seedings in the more arid portions of the Great Basin. Seedlings of desert needlegrass were grown in a greenhouse with 5 different densities of cheatgrass (Bromus tectorum L.). The densities of cheatgrass used in the greenhouse experiments were derived from sampling populations in the field where desert needlegrass is adapted and seedling recruitment is desired. Cheatgrass is known to close sites to the establishment of seedlings of perennial grasses through competition for moisture. The response variable was height of desert needlegrass shoots. Height measurements were taken weekly for 12 weeks following seedling emergence. During the first 5 weeks following emergence there were no significant (P less than or equal to 0.05) differences in the height of desert needlegrass seedlings among treatments. From week 5 through week 12, there was a highly significant (P less than or equal to 0.001) difference in the height of desert needlegrass shoots between the control and all levels of cheatgrass density. Reducing the density of cheatgrass seedlings in the greenhouse to the equivalent of 25% of the density present in the field still did not allow the establishment of the perennial grass seedlings. Even though desert needlegrass is adapted for natural establishment in the drier portions of the central Great Basin, some form of cheatgrass control is required for the perennial grass seedling establishment if cheatgrass is present. Cheatgrass control has to be more than a reduction in density, it has to be near complete control of the annual grass.
    • Classifying federal public land grazing permittees

      Gentner, B. J.; Tanaka, J. A. (Society for Range Management, 2002-01-01)
      This study identifies the characteristics and attitudes of public land ranchers. Data from a random survey of 2,000 U.S. Forest Service and Bureau of Land Management grazing permittees (53.5% response rate) were cluster analyzed and 8 distinct groups of ranchers were identified. Each cluster differed with respect to why they were in ranching and how they would respond to public land policy changes related to grazing fees, grazing reductions, and changes in grazing season. Profit motivation for being in ranching was found to be a relatively low objective for all 8 types of ranchers.
    • Does ruminal retention time affect leafy spurge seed of varying maturity?

      Olson, B. E.; Wallander, R. T. (Society for Range Management, 2002-01-01)
      Grazers ingest seeds of invasive forbs and may contribute to their spread by depositing viable seeds in uninfested areas. Some mature seed pass through the gastrointestinal (GI) tract of ruminants, but grazers consume flowerheads of invasive species from anthesis to dehiscence. We collected seed from the Eurasian leafy spurge (Euphorbia esula L.) at 3 stages of maturity (soft dough, hard dough, mature). With seed collected from these different stages, our objectives were to determine effects of 1) rate of passage through the GI tract of sheep on leafy spurge seed recovery, germinability and viability, 2) residence time in sheep rumen on seed germinability and viability, and 3) acid pepsin digestion, simulating the lower GI tract, on seed germinability and viability after different residence times in the rumen. More seed from the later stages of maturity were recovered in the manure. The greatest number of seed recovered only represented 3.9% of the number of ingested seed. Few seeds were recovered after day 4. Soft dough seed in manure would not germinate and was not viable, whereas hard dough and mature seed collected from manure during the first 4 day were viable. Pepsin had a slight effect on the number of mature seed recovered, but eliminated viability of recovered seed. Viability of non-pepsin treated seed from the hard dough and mature stages declined with greater residence time in the rumen. Thus, managers should be aware that livestock ingesting hard dough as well as mature seed may be dispersing viable weed seed.
    • Drought and grazing: IV. Blue grama and western wheatgrass

      Eneboe, E. J.; Sowell, B. F.; Heitschmidt, R. K.; Karl, M. G.; Haferkamp, M. R. (Society for Range Management, 2002-01-01)
      An understanding of the impacts of grazing during and following drought on rangeland ecosystems is critical for developing effective drought management strategies. This study was designed to examine the effects of drought and grazing on blue grama [Bouteloua gracilis (H.B.K) Lag. ex Griffiths] and western wheatgrass [Pascopyrum smithii Rydb. (Love)] tiller growth dynamics. Research was conducted from 1993 to 1996 at the Fort Keogh Livestock and Range Research Laboratory located near Miles City, Mont. An automated rainout shelter was used during 1994 to impose a severe late spring to early fall (May to October) drought on 6 of twelve, 5- x 10-m non-weighing lysimeters. Twice replicated grazing treatments were: 1) grazed both the year of (1994) and the year after (1995) drought; 2) grazed the year of and rested the year after drought; and 3) no grazing either year. Drought had minimal impact on tiller relative growth rates of plants grazed twice, although it reduced (P less than or equal to 0.01) rates of axillary tiller emergence for blue grama (79%) and western wheatgrass (91%), respectively. Defoliation periodically increased relative growth rates (P less than or equal to 0.05) and tiller emergence (P less than or equal to 0.01) of both species. Neither drought nor grazing affected tiller densities or tiller replacement rates of either species nor did they affect productivity of blue grama. Drought, however, reduced (P less than or equal to 0.01) productivity of western wheatgrass 50% in 1994 whereas grazing reduced productivity (P less than or equal to 0.01) by 46% in 1994 and 69% in 1995. Moderate stocking levels (40-50% utilization) during and after drought did not adversely affect the sustainability of these dominant native grasses.
    • Effects of nitrogen availability on the growth of native grasses exotic weeds

      Lowe, P. N.; Lauenroth, W. K.; Burke, I. C. (Society for Range Management, 2002-01-01)
      Many studies have shown that high nitrogen availability encourages the community dominance of exotic, weedy species. Other researchers have attempted to reduce existing exotic species infestations by reducing soil nitrogen availability. We tested the hypothesis that exotic weeds and native species differ in their response to nitrogen availability, predicting that the exotics would have a much more positive response than the natives at high nitrogen levels but that natives would better tolerate low nitrogen levels. To test this hypothesis, we conducted a greenhouse experiment investigating the aboveground biomass, belowground biomass, height, and aboveground tissue nitrogen concentration response of 2 North American native plant species, blue grama (Bouteloua gracilis H.B.K. Lag.) and western wheatgrass (Pascopyrum smithii (Rybd.) A. Love), and 4 exotic species, cheatgrass (Bromus tectorum L.), leafy spurge (Euphorbia esula L.), Canada thistle (Cirsium arvense L.), and Russian knapweed (Centaurea repens L.), to 5 levels of nitrogen availability, 0 g N/m2, 1 g N/m2, 4 g N/m2, 7g N/m2, and 10 g N/m2. We grew single individuals of each species from seed in 3 liter pots in the greenhouse for 75 days. The exotics and natives did differ in their response to nitrogen availability, but not in the predicted manner. The exotics did not have a more positive response to nitrogen availability than the native species, and the species with the poorest response was an exotic. There were no differences between the exotic and native species at any level of nitrogen availability in root:shoot ratios, total biomass, or percent leaf tissue nitrogen, but the native species as a group gained more height than the exotics at every level of nitrogen availability. Our data do not show a generalizable relationship between exotic or native plant groups and growth response to nitrogen.
    • Effects of top-soil drying on saltcedar photosynthesis and stomatal conductance

      Mounsif, M.; Wan, C.; Sosebee, R. E. (Society for Range Management, 2002-01-01)
      Phreatophytes are trees and shrubs with deep roots tapping the water tables. As such they are presumed to be able to tolerate a water deficit in the top soil. Growth of some phreatophytes is decoupled from environmental factors such as incident precipitation. This study examined the effects of surface soil drying on gas exchange and stomatal conductance of a riparian phreatophyte Tamarix gallica L. (saltcedar) during 2 consecutive growing seasons in which summer precipitation varied substantially. Daily average gas exchange (A) was 13.5 micromol m(-2) sec(-1) in June and 13.4 micromol m(-2) sec(-1) in September, 1991 when surface soil was wet as compared to the same periods of 1990 in which very little rain occurred (6.44 and 8.08 micromol m(-2) sec(-1), respectively, P < 0.0001). Stomatal conductance (g) or maximal conductance showed a similar trend of photosynthesis. Both average gas exchange and stomatal conductance were correlated with water content in the upper portion of the soil (r = 0.83 to 0.88 for A, P < 0.05 and r = 0.65 to 0.70 for g, P < 0.05) in 1990 (a dry year). The variations in gas exchange or stomatac conductance of saltcedar were mainly caused by water availability in the upper soil layers, not by depth to the water table (0.65 vs 2.74 m). The responses of gas exchange and stomatal conductance to surface soil drying in the phreatophyte saltcedar were similar to that of several crop species [lupin (Lupinus cosentinii Guss. cv. Eregulla), wheat (Triticum aestivum L. cv. Cadensa) and sunflower (Helianthus annuus L.)]. Our data suggest that upon soil re-wetting, when water availability to shallow lateral roots increased, the entire root system of saltcedar was actively involved in water uptake, leading to higher stomatal conductance and photosynthesis.
    • Grazing impacts on litter and roots: Perennial versus annual grasses

      Mapfumo, E.; Naeth, M. A.; Baron, V. S.; Dick, A. C.; Chanasyk, D. S. (Society for Range Management, 2002-01-01)
      Soil carbon (C) and nitrogen (N) storage in grasslands is a function of litter and root mass production. Research on how annual grasses compare with perennials for above ground and below ground mass production, and contributions to the soil C pool under pasture management is scarce. The objective of this research was to evaluate grazing intensity effects on litter and root mass, C and N pools of perennial grasses, smooth bromegrass (Bromus inermis L.) and meadow bromegrass (Bromus riparius Rhem.), and the annual grass, winter triticale (X Triticosecale Wittmack). Litter mass and C pool for the perennial grasses were greater than those for triticale. Litter C and N pools generally decreased with increased grazing intensity. Root mass was greater for the perennial grasses than for triticale at all grazing intensities. Meadow bromegrass generally produced more root mass than smooth bromegrass. Root C and N pools for triticale were 31 and 27%, respectively, of that for the perennial grasses. Estimated total C contribution (roots and litter) to the resistant soil organic C pool was 1.5 times greater for light compared to heavy grazing. Total C (litter + root) contribution for perennial grasses was 2.7 times greater than that for triticale. Perennial grasses provided a larger litter base and root system that promote greater storage of C in the soil compared with triticale.
    • Intake and digestive kinetics of leaf and stem fractions

      Lamb, J. B.; Adams, D. C.; Klopfenstein, T. J.; Grant, R. J.; Sims, P. L.; White, L. M.; Waller, S. S. (Society for Range Management, 2002-01-01)
      Ruminally fistulated steers were used in a 4 x 4 Latin square to test effects of immature (vegetative) and mature (post reproductive) leaf and stem fractions from subirrigated meadow hay on organic matter intake (OMI), organic matter digestibility (OMD), and digestive kinetics. Hay was harvested 1 June (immature) and 1 October (mature), chopped into 3- to 5-cm lengths, then separated into leaf and stem fractions using a modified Clipper Cleaner Model Super 69D. Steers were provided ad libitum access to fractions and supplemented with urea so that diets were iso-nitrogenous. Particulate passage was determined using Yb labeled large hay particles [greater than or equal to 1.7-mm screen] and Er labeled small particles [< 1.7-mm and greater than or equal to 0.212-mm screen]. Samples were collected from the rumen, omasum, feces, and un-masticated diets for particle size determination. Particle size was determined using wet sieving techniques. Voluntary OMI of immature fractions (15.4 g kg(-1) BW) was greater (P < 0.05) than mature fractions (12.5 g kg(-1) BW). Within maturity OMI and OMD of leaves and stems were similar. Immature fractions had greater (P < 0.05) OMD (63.2%) than mature fractions (55.7%). Large and small particle passage rates were faster (P < 0.05) for immature fractions [3.2% hour(-1) (large) and 4.3% hour(-1) (small)] than mature [(2.3% hour(-1) (large) and 2.9% hour(-1) (small)]. Critical particle size for ruminal escape was less than or equal to 1.18 mm for both leaves and stems regardless of maturity. Differences in OMI and OMD between immature and mature fractions were explained by changes in structural components of the cell wall that made particles more resistant to mechanical and microbial breakdown.
    • Intermediate wheatgrass and Russian wildrye responses to defoliation and moisture

      Hendrickson, J. R.; Berdahl, J. D. (Society for Range Management, 2002-01-01)
      Perennial forage grasses in the Northern Great Plains are often grazed under water-limiting conditions. The effects of defoliation and soil moisture dynamics on herbage yield, tiller recruitment and number of crown positions for 2 perennial forage grasses were evaluated in a greenhouse experiment at Mandan, N.D. Intermediate wheatgrass (Thinopyrum intermedium (Host) Barkw. D.R. Dewey] and Russian wildrye (Psathyrostachys juncea (Fisch.) Nevski] were grown at 75, 50, or 40% of field capacity and left as undefoliated controls or defoliated at 10-day intervals to an 8- or 4-cm stubble height. Cumulative herbage yield exhibited defoliation level by soil moisture (P = 0.0001) and species by defoliation (P = 0.007) interactions. Yield decreased with increasing defoliation intensity at 75 and 50% of field capacity, but at 40% of field capacity only the most intense defoliation level was significantly affected. Russian wildrye produced more herbage (1.97 g plant(-1)) than intermediate wheatgrass (1.36 g plant(-1)) under severe defoliation level. Increased defoliation intensity (P = 0.0001) but not water availability (P > 0.05) decreased tiller numbers. Pooled across all treatments, Russian wildrye produced 10 tillers per plant and intermediate wheatgrass produced 7 (P = 0.0001). This may partially explain Russian wildrye's greater grazing tolerance. The number of crown positions (potential axillary bud sites in the bottom 20mm of the plant) was similar between species suggesting that increased tiller numbers in Russian wildrye occurred because its axillary buds were more readily activated than intermediate wheatgrass. Moderate and severe defoliation reduced the number of crown positions on parent seedlings to only 62 and 50% of the number of crown positions of control seedlings, respectively. Water stress decreased (P = 0.004) number of crown positions at 40% of field capacity but only when crown positions of both parent and daughter tillers were pooled. In this experiment, defoliation had a greater effect than water stress. Moisture level mainly affected tiller size not numbers. The interaction between defoliation and water stress should be examined in field studies to foster improved management of these 2 grasses.
    • Quality of forage stockpiled in Wisconsin

      Hedtcke, J. L.; Undersander, D. J.; Casler, M. D.; Combs, D. K. (Society for Range Management, 2002-01-01)
      Stockpiling forage is a commonly used method to extend the grazing season in the southern U.S.A. However, there is little data on stockpiled forage in the upper Midwest. This study was conducted to determine the quality changes of 7 stockpiled cool-season grasses [early and late maturing orchardgrass, Dactylis glomerata L., quackgrass, Elytrigia repens (L.) Desv. Ex. Nevski, reed canarygrass, Phalaris arundinacea L., smooth bromegrass, Bromus inermis Leyss., tall fescue, Festuca arundinacea Schreb., and timothy Phleum pratense L.], with and without N fertilizer, in Wisconsin. Forage was sampled at 3 offseason dates at 3 sites. To determine if N improved forage quality, 4 N-fertilizer treatments were imposed: 0 or 67 kg N ha(-1) applied at start of stockpiling and 2 treatments totaling 168 kg N ha(-1) applied in the fall and spring. Over winter, crude protein (CP) decreased from 116 to 107 g kg(-1), neutral detergent fiber (NDF) increased from 594 to 667 g kg(-1), acid detergent fiber (ADF) increased from 367 to 435 g kg(-1), and in vitro organic matter digestibility (IVOMD) fell from 734 to 655 g kg(-1). Nitrogen fertilizer improved CP in most environments but generally did not affect IVOMD, NDF, or ADF. Smooth bromegrass and quackgrass ranked highest in CP concentration and tall fescue ranked lowest. Timothy and late-maturing orchardgrass ranked highest in IVOMD while quackgrass and reed canarygrass consistently ranked lowest. Quality of all stockpiled forage studied can maintain livestock such as beef cattle or dry dairy cows over winter if the forage is accessible and adequate animal stocking density is maintained.
    • Rangeland management under uncertainty: A conceptual approach

      Batabyal, A. A.; Godfrey, E. B. (Society for Range Management, 2002-01-01)
      A conceptual approach is commonly needed to provide guidance for developing new strategies concerning the use and management of renewable resources such as rangelands. The theoretical model constructed in this paper captures the essential aspects of dynamic and stochastic issues associated with the management of rangelands. We discuss the connections between the model and range policy. Specifically, we point out scenarios in which there is a limited role for policy. This is compared to scenarios when policy has a significant role to play in ensuring the sustainable use of rangelands. Finally, we suggest 2 ways in which our approach might be extended and used in a practical application.
    • Salinity affects development, growth, and photosynthesis in cheatgrass

      Rasmuson, K. E.; Anderson, J. E. (Society for Range Management, 2002-01-01)
      The effects of salt stress on growth and development of cheatgrass (Bromus tectorum L.) were investigated in 2 greenhouse studies. The first study assessed developmental and physiological responses of this grass to 4 salinity levels. Salinity stunted growth through reduced leaf initiation and expansion, and reduced photosynthetic rates. Reduction of photosynthetic rates appeared to be primarily due to stomatal limitation. Salinity also reduced carbon isotope discrimination, indicating long-term effects on conductance and carbon gain. Root growth was severely inhibited by high salinity, resulting in a shift in the root to shoot allocation pattern. The second study investigated growth patterns of cheatgrass in relation to intraspecific variation in salt tolerance using plants grown from seeds collected at non-saline and saline sites. Salinity reduced growth of plants from both environments. However, plants from the saline site accumulated leaf and root area at nearly twice the rate as those from the non-saline site, even in the control group. Because plants were grown in a common environment, growth differences between populations were genetically based. Thus, the potential for rapid growth may enable plants from the saline site to rely on shallow, less saline moisture reserves available early in the growing season.
    • Seasonal grazing affects soil physical properties of a montane riparian community

      Wheeler, M. A.; Trlica, M. J.; Frasier, G. W.; Reeder, J. D. (Society for Range Management, 2002-01-01)
      The effects of seasonal grazing treatments (early spring and late summer) on soil physical properties were studied in a montane riparian ecosystem in northern Colorado. Infiltration rates and bulk density were used as primary indicators of responses to a 1-time heavy grazing event on previously protected paddocks. Soil bulk density, porosity, gravimetric water content, organic carbon concentration and texture were measured at 0-5 cm, 5-10 cm, and 10-15 cm depths to determine how these parameters affected infiltration rates. Assessment of initial changes and subsequent recovery of the soil properties in response to the grazing treatments was conducted by measuring these parameters before each grazing event and at 4 time periods following the grazing event. Few differences between spring or late summer grazing periods on soil physical properties were found. A stepwise multiple regression model for infiltration rate based on soil physical properties yielded a low R2 (0.31), which indicated much unexplained variability in infiltration. However, infiltration rates declined significantly and bulk density increased at the 5-10 cm depth and 10-15 cm depth in grazed plots immediately following grazing, but the highly organic surface layer (0-5 cm) had no significant compaction. Infiltration rates and soil bulk densities returned to pre-disturbed values within 1 year after grazing events, suggesting full hydrologic recovery. This recovery may be related to frequent freeze-thaw events and high organic matter in soils.
    • Soil erosion as affected by shrub encroachment in northeastern Patagonia

      Parizek, B.; Rostagno, C. M.; Sottini, R. (Society for Range Management, 2002-01-01)
      Soil erosion is the primary cause of irreversible loss of soil productivity on most rangelands. In northeastern Patagonia, the increase in soil erosion has been closely associated with the increase in shrub cover in the grass or shrub-grass steppes. We used rainfall simulation to compare infiltration and sediment production from patches of grass, shrub-grass, and shrub steppes of the Punta Ninfas range site. Bare soil and gravel covers were higher and litter cover was lower in the shrub steppe than in the shrub-grass and the grass steppes. In the shrub inter-spaces of the shrub steppe, bulk density was greater and macroporosity and soil organic matter were lower (P less than or equal to 0.05) than in the mounds beneath shrubs and in the grass and shrub-grass areas. Infiltration rate was 60 to 65% lower in the shrub steppe than in the grass and shrub-grass steppes, respectively. On the contrary, total sediment production and concentration were higher (P less than or equal to 0.05) in the shrub steppe as compared to the grass and the shrub-grass areas. Gravel cover was the variable that best predicted infiltration and sediment production. The organic matter content of the sediment, mostly litter, in the shrub and the shrub-grass steppes were similar and greater (P less than or equal to 0.05) than in the grass steppe. Runoff litter removal may represent one of the processes that drive the transition from shrub-grass to shrub steppes. High rates of sediment removal, mainly litter, from the shrub interspaces of the shrub steppe may limit the natural recovery of the soil physical and hydrological properties. These degraded patches fail to capture incident rainfall and restrict the possibilities for the recovery of perennial grasses favoring the dominance of shrubs.
    • Windrow grazing and baled-hay feeding strategies for wintering calves

      Volesky, J. D.; Adams, D. C.; Clark, R. T. (Society for Range Management, 2002-01-01)
      Management practices that lower livestock production costs are of interest to ranch enterprises. Windrow or swath grazing is a strategy where livestock directly graze windrow-stored forage, generally during a time when packaged hay or some other feed is provided. The objectives of this study were: 1) to quantify calf performance and forage intake and waste under windrow grazing (windrow) and bale-fed (bale) management strategies; 2) to quantify hay quality changes as affected by storage method and time; 3) to determine the effects of windrow coverage on subsequent meadow herbage yield and composition; and 4) to compare costs and returns associated with windrow and bale strategies. The forage source was wet meadow dominated by cool-season perennial species with alternating windrows baled and the remaining windrows left in place for direct grazing. Weaned steer calves were fed baled hay or grazed windrows during a November-January period each of 2 years. Windrow grazing calf gains were greater (P < 0.05) than bale-fed during the first year of the study but gains were similar during the second year. Greater weight gain for windrow calves during the first year was likely due to the presence of high quality regrowth that occurred after hay harvest. Diet samples collected from fistulated windrow animals in December contained 14.6% crude protein (CP) compared to 10.4% for hand-collected samples of windrows (P < 0.05). Crude protein content of windrow- and baled-stored forage was similar (10.6%, P > 0.05) during all sampling months (September-February). Crude protein content of standing (stockpiled) forage declined to 5.7% by February. Acid detergent fiber (ADF) and neutral detergent fiber (NDF) were similar between windrow and standing storage treatments during all months and higher than bales from November through February. Herbage yield was 20% less in the area directly covered by windrows the previous fall and winter compared to the control (P < 0.05). However, only about 9% of the total area of a pasture is affected by windrow-coverage when 1-m wide windrows are created 11 m apart, resulting in an overall herbage yield reduction of 1.5%. Total forage production costs for the bale-fed strategy were about 63 ha(-1) (37%) higher than windrow grazing due to baling and bale moving costs. Feed costs averaged 0.16 head(-1) day(-1) for windrow and 0.30 head(-1) day(-1) for the bale strategy. When production data were applied to market prices for the previous 7 years, the mean net return ha(-1) for windrow exceeded the net return for the bale strategy by about 93 and the net return for a strategy that directly sold the hay by 174.