• Drought and grazing III: Root dynamics and germinable seed bank

      Hild, A. L.; Karl, M. G.; Haferkamp, M. R.; Heitschmidt, R. K. (Society for Range Management, 2001-05-01)
      Drought and herbivory frequently influence North American rangelands. While these influences may temporarily reduce vegetative cover, their mutual influence on the available seedbanks which might occupy new safe sites is unclear. We examine effects of drought and grazing upon pre- and post-drought plant root distribution and germinable seed bank to determine 1) if the response of root distributions to drought depends upon grazing use and 2) if the presence of germinable seeds is altered significantly by drought and grazing. Using twelve, 5 X 10 m non-weighing lysimeters with an automated rainout shelter, we documented root intercepts in situ using a minirhizotron from 1993-1996. Seed bank samples were incubated in a greenhouse to determine seedling emergence. Roots were fewer in shallow soil layers in grazed plots than ungrazed plots by the end of the study, irrespective of drought. Roots in deeper (Bw horizon) soil layers were fewer during drought, but were not influenced by grazing. Seed bank composition results suggest that perennial grasses were a small portion of the seed bank. Cool-season annual grass seeds accumulated after drought. Without drought, forb seed banks increased with grazing. Thus while shallow roots may decrease during drought, in the year following drought grazing may decrease aboveground net primary production, and allow large accumulations of cool-season annual grass seed in a northern mixed grass prairie.
    • Drought and grazing: I. Effects on quantity of forage produced

      Heitschmidt, R. K.; Haferkamp, M. R.; Karl, M. G.; Hild, A. L. (Society for Range Management, 1999-09-01)
      This research addresses the hypothesis that grazing intensity during and following drought can dramatically alter community level, post-drought recovery patterns. Research was conducted during the 1993 through 1996 growing seasons at the Fort Keogh Livestock and Range Research Laboratory located near Miles City, Mont. Study plots were twelve, 5 × 10-m non-weighing lysimeters constructed in 1992 on a gently sloping (4%) clayey range site. An automated rainout shelter was constructed to control the amount of precipitation received on 6 lysimeters during the 1992 growing season. We conclude from study results that the independent and combined effects of the imposed late spring to early fall drought and associated grazing treatments were minimal relative to soil water dynamics and aboveground net primary production although both grazing treatments reduced herbage standing crops. We attribute the absence of a strong response to the drought to its timing (i.e., late growing season) in that most herbage production in these cool-season dominated grasslands is completed by early summer. Thus, annual production processes in these grasslands avoided the major impacts of the drought. The results do not provide convincing evidence, however, that would lead us to completely reject our original hypothesis. Rather, they simply provide evidence that these grasslands are well adapted to surviving late growing season drought with or without intensive grazing by ungulates.
    • Drought and grazing: II. Effects on runoff and water quality

      Emmerich, W. E.; Heitschmidt, R. K. (Society for Range Management, 2002-05-01)
      Understanding the interacting effects of drought and grazing on runoff, erosion, and nutrient transport is essential for improved rangeland management. Research was conducted at the Fort Keogh Livestock and Range Research Laboratory located near Miles City, Mont. using 12, non-weighing lysimeters for 3 years. During years 1 and 3, no drought treatment was imposed. For year 2, one half of the lysimeters were covered to implement a drought treatment. The 3 grazing treatments were ungrazed, grazed during but not after drought, and grazed during and after drought. Runoff, sediment yield, and an array of nutrients in the runoff water were measured from the lysimeters. First year base line data with no grazing or drought treatments applied indicated no significant differences among lysimeters. Below normal precipitation occurred during year 2, resulting in no runoff from the drought treatment and negated the "non-drought" control. This prevented a direct assessment of the interaction among the drought and grazing treatments for this year. The drought treatment did produce significant reductions in water, sediment, and nutrient yield. No grazing impact was observed during year 2. The third year with more normal precipitation, there was a trend toward increased runoff, sediment, and nutrient yield from the second year drought treatment lysimeters. In the third year, both grazing treatments showed significantly greater runoff, sediment, and nutrient yield than the ungrazed treatment. Runoff and sediment yield tended to increase from the combination of drought and grazing treatments. The observed increases in runoff and sediment and reduced water quality from the drought and grazing treatments were measured against controls and when compared to the natural variability and water quality standards, they were concluded to be minimal.
    • 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, 2002-03-01)
      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%). 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.
    • 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.
    • Drought and Low Cattle Prices: Hardship for New Mexico Ranchers

      Holechek, Jerry L. (Society for Range Management, 1996-02-01)
    • Drought and Phosphorous Affect Growth of Annual Forage Legumes

      Wilson, A. M.; McKell, C. M.; Williams, W. A. (Society for Range Management, 1968-09-01)
      Three annual forage legumes, apparently differing in their drought resistance in the field, were grown in controlled environments to better understand mechanisms of their drought resistance and to determine relationships between phosphorus nutrition and drought. Phosphorus fertilization stimulated growth of the annual legumes and decreased water use (ml/g dry weight of top growth). Relative top growth and phosphorus uptake of Spanish clover tended to confirm observations of its drought resistance in the field. Water use was higher in Spanish clover than in subterranean clover and therefore does not appear to contribute to its drought resistance. This study provides information that will be helpful in future research on the morphological and physiological traits that contribute to drought resistance in these and other range plants.
    • Drought and Recovery in the Upper Sonoran Desert

      Robinett, Dan (Society for Range Management, 1992-08-01)
    • Drought Consequences for Cow-Calf Production in Wyoming: 2011—2014

      Scasta, John D.; Windh, Jessica L.; Smith, Travis; Baumgartner, Bob (Society for Range Management, 2015-12-01)
      On the Ground • Drought reduces forage quantity and carrying capacity, but reductions in cow-calf performance measured by calf average daily gain (ADG) and weaning weight (WW) are less understood. • From 2011 to 2014, a period with very dry and very wet years, we assessed an adjusted 210 day WW and ADG for a total of 869 calves on two University of Wyoming ranches. • We found WW was up to 99 pounds (lb) lower, and ADG was up to 0.47 lb lower between the driest and wettest years. • For each one inch reduction in precipitation, WW are predicted to be 7 lb to 14 lb lower, ADG is expected to be 0.03 lb to 0.07 lb lower, and dollar per head values 12 to 27 lower, depending on calf sex and ranch location. • If drought occurs, or continues to escalate in frequency and severity, WW reductions, ADG reductions, and value per head reductions should be expected and documented for strategic planning and/or compensation programs.
    • Drought Effects on Adventitious Root Development in Blue Grama Seedlings

      Briske, D. D.; Wilson, A. M. (Society for Range Management, 1980-09-01)
      Crowns of blue grama (Bouteloua gracilis) seedlings of three ages were exposed to drought treatments for 2 days, in constant humidity environments, and were then planted in moist soil for a 10-day growth test at 25° C. Percentage survival of crowns decreased with a decrease in water potential during the temporary drought treatment and with a decrease in crown age at time of treatment. The percentage survival rates of 21-, 28-, and 35-day-old crowns treated at -180 bars were 5, 54, and 83, respectively. Crowns exposed to the 2-day drought treatment subsequently produced shorter adventitious roots than untreated crowns. Thus, a drought-induced inhibition of adventitious root growth may reduce the probability of successful seedling establishment.
    • Drought Effects on Diet and Weight Gains of Yearling Heifers in Northeastern Oregon

      Holechek, J. L.; Vavra, M. (Society for Range Management, 1983-03-01)
      Daily weight gains and diets of cattle were evaluated during a year with average precipitation and in a drought year on mountain range in northeastern Oregon. Forage intake was evaluated only in the drought year. Esophageally fistulated heifers were used to sample diet quality and botanical composition. Botanical composition of cattle diets was different (P<.05) in the late spring and early summer between years. When green grass and forbs were not available, browse was heavily utilized. Livestock weight gains and forage intake in the latter part of the grazing season were reduced (P<.05) during the drought year. This is attributed to depletion of browse, primarily common snowberry (Symphoricarpos albus). Diet crude protein and neutral detergent fiber concentrations were significantly (P<.05) correlated with average daily gains. When ruminants are consuming diets with more than one forage class, neutral detergent fiber and composition and yield of volatile fatty acids may more accurately evaluate the energy status of the diet than digestibility. Supplementation of crude protein could potentially improve average daily gains during drought years if browse was unavailable. Ranges with a high component of forbs and shrubs will ameliorate the negative effects of drought on average daily gains.
    • Drought Effects on the Ranching Industry in Southeastern Colorado

      Miller, Mary M. (Society for Range Management, 2005-04-01)
    • Drought in New Mexico: Prospects and Management

      Holechek, Jerry L. (Society for Range Management, 1996-12-01)
    • Drought Influences Control of Parasitic Flies of Cattle on Pastures Managed with Patch-Burn Grazing

      Scasta, J. D.; Engle, D. M.; Talley, J. L.; Weir, J. R.; Fuhlendorf, S. D.; Debinski, D. M. (Society for Range Management, 2015-05)
      We compared the influence of patch-burn grazing to traditional range management practices on abundance of the most economically injurious fly parasites of cattle. Horn flies (Haematobia irritans), face flies (Musca autumnalis), stable flies (Stomoxys calcitrans), and horse flies (Tabanus spp.) were assessed at study locations in Oklahoma and Iowa, USA, in 2012 and 2013. Experiments at both locations were spatially replicated three times on rangeland grazed by mature Angus cows. Grazing was year-long in Oklahoma and seasonal in Iowa from May to September. One-third of patch-burn pastures were burned annually, and traditionally managed pastures were burned completely in 2012 but not at all in 2013. Because of significant location effects, we analyzed locations separately with a mixed effects model. Horn flies and face flies were below economic thresholds with patch-burn grazing but at or above economic thresholds in unburned pastures in Iowa. Pastures in Iowa that were burned in their entirety had fewer horn flies but did not have fewer face flies when compared with no burning. There was no difference among treatments in horn fly or face fly abundance in Oklahoma pastures. Stable flies on both treatments at both locations never exceeded the economic threshold regardless of treatment. Minimizing hay feeding coupled with regular fire could maintain low stable fly infestations. Horse flies at both locations and face flies in Oklahoma were in such low abundance that treatment differences were difficult to detect or explain. The lack of a treatment effect in Oklahoma and variable year effects are the result of a drought year followed by a wet year, reducing the strength of feedbacks driving grazing behavior on pastures burned with patchy fires. Patch-burning or periodically burning entire pastures in mesic grasslands is a viable cultural method for managing some parasitic flies when drought is not a constraint. © 2015 Society for Range Management. Published by Elsevier Inc. All rights reserved.
    • Drought Management—The Australian Way

      McCartney, Duane (Society for Range Management, 2000-06-01)
    • Drought Mitigation for Grazing Operations: Matching the Animal to the Environment

      Scasta, John Derek; Lalman, David L.; Henderson, Leticia (Society for Range Management, 2016-12-01)
      On the Ground • With expected increases in drought frequency and severity, long-term drought management strategies that focus on cattle selection and natural resource management are essential. • The livestock industry in general unintentionally tends to select for cattle that do not perform to their maximum potential in limited-resource environments. We discuss the implications of cattle selection based on characteristics such as genetic potential, cow size, and hide color. • In a hypothetical model, we found that because forage requirements for smaller cows are lower than forage requirements for larger cows, using a herd of smaller cows produces a larger total calf crop if cow size and milk do not lead to greater calf production. • Because grazed forage remains the least expensive source of nutrients to maintain the cow herd, matching cow size and milk production potential to forage resources to optimize forage utilization and reproductive efficiency should be considered a rangeland drought mitigation strategy. • Contemporary strategies such as using EPDs and selection indexes to manage maternal traits such as mature weight and maintenance energy requirements can be integrated with conventional drought mitigation strategies that focus on resource quality management.
    • Drought Resistance of Blue Grama as Affected by Atrazine and N Fertilizer

      Hyder, D. N.; Houston, W. R.; Burwell, J. B. (Society for Range Management, 1976-05-01)
      Two consecutive summer droughts in north central Colorado caused considerable thinning of blue grama (Bouteloua gracilis) stands, and N fertilizer accentuated the drought effects. However, atrazine, with or without N fertilizer, prevented serious thinning of stands. Consequently, investigations were initiated to test the hypotheses that atrazine created greater resistance to, or tolerance of, drying in crown tissues. Both hypotheses were rejected. It remains to be determined whether the combined effects of weed control, slower transpiration, and changes in root distribution by atrazine treatment may reduce water consumption and, thus, protect blue grama from drought.
    • Drought Tolerance of Seminal Lateral Root Apices in Crested Wheatgrass and Russian Wildrye

      Hassanyar, A. S.; Wilson, A. M. (Society for Range Management, 1978-07-01)
      Germinating seed of crested wheatgrass (Agropyron desertorum) and Russian wildrye (Elymus junceus) were exposed to temporary drought, and the capacity for development of seminal lateral roots was then determined under conditions of favorable soil moisture. After a temporary drought of -370, -910, and -1580 bars, 75, 58, and 24% of the crested wheatgrass seedlings and 69, 20, and 6% of the Russian wildrye seedlings developed seminal lateral roots, respectively. Because actively growing seminal primary roots may be killed by temporary drought and because germinating seed and young seedlings lack the capacity for development of adventitious roots, the growth and survival of seedlings often may depend on the development of seminal lateral roots.
    • Drought, No Fear!

      Moldenhauer, Lori (Society for Range Management, 1998-12-01)
    • Droughts and Wildfires in Western U.S. Rangelands

      Scasta, John Derek; Weir, John R.; Stambaugh, Michael C. (Society for Range Management, 2016-12-01)
      On the Ground • Because fire activity fluctuates with short- and long-term term weather and climate trends, understanding trends relative to climate forecasts is critical to mitigating the loss of life and property and rapid vegetation state changes. • Through the analysis of charcoal and trees scars, historical droughts and fire patterns can be quantified retrospectively for hundreds of years. This evidence suggests that generally fire was most frequent during warm-dry periods as opposed to cool-moist periods. However, arid regions may see an increase of fire activity with an increase of moisture due to inherent fuel load limitations. • Using federal wildfire and weather data from 2002 to 2015 for New Mexico, Nevada, Oklahoma, and Wyoming, we demonstrate that the worst wildfire activity occurred after average or above average precipitation years followed by drought in Oklahoma and Wyoming. Nevada wildfire activity was correlated with precipitation the preceding year, and New Mexico wildfire activity was not correlated with annual precipitation or preceding year precipitation. • The effects of future drought on fire intensity and severity are projected to be highly variable because they are both a function of fuel load. However, the potential for very large wildfires is predicted to increase; fire weather is expected to create hotter and drier conditions that start earlier and last longer; and the relative changes may be most noticeable in cooler regions that are of higher latitude and elevation.