• Impact of Feral Herbivores on Mamane Forests of Mauna Kea, Hawaii: Bark Stripping and Diameter Class Structure Sophora chrysophylla

      Scowcroft, P. G.; Sakai, H. F. (Society for Range Management, 1983-07-01)
      Management of feral and Mouflon sheep and feral goats within the Mauna Kea Forest Reserve/Game Management area has been criticized as inadequate to prevent the adverse environmental impact which these introduced herbivores have on native components of the scrub forest ecosystem. This study determined the intensity of bark stripping of mamane (Sophora chrysophylla), a small endemic leguminous tree, by these animals and assessed the impact of their browsing on the size class structure of mamane stands. In all but one of the 4 areas sampled, a high proportion of mamane trees bore bark stripping wounds. Differences in the amount of stripping between elevations in a given area, and between areas, were attributed to differences in browsing pressure, which in turn was dependent on the frequency of human disturbance and the behavioral traits of the herbivores. Tree size class distributions revealed that browsing has suppressed mamane reproduction in some areas. Suppression appeared to be the greatest in the most heavily browsed areas.
    • Impact of grazing on soil nutrients in a Pampean grassland

      Lavado, R. S.; Sierra, J. O.; Hashimoto, P. N. (Society for Range Management, 1996-09-01)
      Cattle exclusion induced dramatic changes in the plant community and modifications in nutrient cycling in grazed native grasslands of the Flooding Pampa (Argentina). The study was carried out to analyze the effect of grazing on the status and spatial variability of soil organic matter, nitrogen and phosphorus. Sampling was performed in the late summer and early spring. Geostatistical methods were used to study the spatial dependence of these soil properties. Organic carbon (OC) and total nitrogen (TN) showed spatial structure only in the ungrazed area with a similar range of dependence (39 m and 36 m respectively). The occurrence of litter in this area lead to a large and spatially homogeneous C input to the soil, which would be the key factor of the spatial structure of organic carbon and total nitrogen. Mineral nitrogen content 1(NO3(-1)-N + (NH4+)-N] was higher in the ungrazed area on both sampling dates. The mineral N content showed a large short-range variability (nugget variation) independent of grazing history. A significant decrease in the extractable P (Bray & Kurtz #1) in the grazed area was found. The extractable P exhibited spatial structure only in the ungrazed area. However, its spatial pattern was different from those of organic carbon and total nitrogen: the range of dependence was higher (57 m) and the spatial structure exhibited a great irregularity. The differences between C, N, and P variability were possibly related to their dynamics in the soil. No evidence of effects of animal excrete on nutrient content or spatial variability was found.
    • Impact of Incremental Surface Soil Depths on Infiltration Rates, Potential Sediment Losses, and Chemical Water Quality

      Lyons, S. M.; Gifford, G. F. (Society for Range Management, 1980-05-01)
      A study was conducted between October 1974 and August 1976 to measure the effects of incremented surface soil depths on infiltration rates, potential sediment production, and chemical quality of runoff water. The treatments were incremental removals of 7.6-cm soil layers to a depth of 30.5 cm on two pinyon-juniper sites in Utah. Hydrologic parameters were measured at each 7.6-cm incremental soil depth using a Rocky Mountain infiltrometer. With one exception, no significant differences occurred in infiltration rates among treatment depths during either 1975 or 1976 at either the Blanding (southeastern Utah) or Milford (southwestern Utah) site. A significant change in infiltration capacities was noted between the 1975 and 1976 field seasons when data from both treatment depths and study sites were pooled. There were no significant differences in potential sediment production between sites or among treatment depths at a site. In terms of chemical water quality, a significant change in phosphorus content of runoff waters was observed at the Blanding site between the 1975 and 1976 field seasons. Significant differences in potassium concentrations were found between sites and among soil depths. Nitrate concentrations were very low in runoff waters from all soil depths at both sites.
    • Impact of Incremental Surface Soil Depths on Plant Production, Transpiration Ratios, and Nitrogen Mineralization Rates

      Lyons, S. M.; Gifford, G. F. (Society for Range Management, 1980-05-01)
      From October 1974 to August 1976, a study was conducted to measure how incremental surface soil depths from the pinyon-juniper type affected plant production, plant transpiration rates, and nitrate nitrogen mineralization rates. The treatments were incremental removals of 7.6-cm soil layers to a depth of 30.5 cm. Plant production and transpiration ratios (or water use efficiencies) were measured in greenhouse studies using Agropyron desertorum grown in specified incremental 7.6-cm soil layers taken from five study sites throughout Utah. Significant decreases in plant production and increases in transpiration ratios were measured for all sites at incremental depths beyond 7.6-cm. These changes in plant production and transpiration ratios were linearly related to the nitrate nitrogen content of the soils (as determined when the soils were collected for use in the greenhouse). Nitrate mineralization rates were measured for two 6-week periods under field conditions at two sites for each of the 7.6-cm incremental soil layers. Nitrate nitrogen mineralization was linearly correlated with the organic carbon content of the soil. Decreased mineralization rates as measured in the field at both sites were reflected in the significant increases in plant water requirements and decreases in production that were measured in greenhouse studies.
    • Impact of Intensity and Season of Grazing on Carbohydrate Reserves of Perennial Ryegrass

      El Hassan, B.; Krueger, W. C. (Society for Range Management, 1980-05-01)
      Carbohydrate reserves of perennial ryegrass declined during winter and early spring and began replenishment during seed formation. The primary reserve accumulation in roots occurred during fall growth, while crowns replenished about half of their reserves from seed formation to fall and the balance during fall. Total nonstructural carbohydrate (TNC) reserves in roots were highest following a relatively wet year when compared to an average year but carbohydrate reserves were found to be more concentrated in the average year. Biomass of storage organs had a greater effect than concentration of carbohydrates on TNC reserves. Complete protection of perennial ryegrass from grazing did not induce greater accumulation of carbohydrate reserves when compared to any season of grazing treatment and they were sometimes significantly lower than for grazed treatments. No advantage from deferment of grazing in spring, summer, or fall could be determined based on carbohydrate reserves as along as stocking intensity did not exceed one ewe per 650 kg of herbage production per year. At stocking rates above this, deferment during part of the growing season should be beneficial.
    • Impact of Land Subdivision and Sedentarization on Wildlife in Kenya’s Southern Rangelands

      Groom, Rosemary J.; Western, David (Society for Range Management, 2013-01-01)
      Subdivision and sedentarization of pastoral communities is accelerating rapidly across the African rangelands, posing a severe threat to wildlife populations, but few studies have looked quantitatively at the ecological impact of sedentarization. Here we look at the impact of sedentarization on wildlife by comparing ecologically matched subdivided and unsubdivided Maasai pastoral lands (ranches) in semiarid southern Kenya. We found no significant difference in livestock densities on the two ranches but there was a significantly higher wildlife density on the unsubdivided ranch, in both dry and wet seasons. Nonetheless, the unsubdivided ranch still had a higher percentage of grass biomass and ground cover and lower grazing pressure than the subdivided ranch. Distribution of homesteads (bomas) was mostly random on the subdivided ranch, with little area unaffected by human settlement. On the contrary, the unsubdivided ranch had a highly clumped boma distribution pattern, resulting in much of the land being relatively far from permanent human settlement. We show that the regular distribution and permanence of settlements following subdivision and sedentarization greatly reduces wildlife populations both through direct displacement and a reduction of forage. Relative to mobile pastoralism on open rangelands, sedentarization leads to reduced seasonal movements of livestock, lowered grass biomass, and slower grass recovery after very dry periods. This study points to the need to maintain mobile, large-scale herd movements to avoid the heavy impact on grasslands associated with sedentarization of pastoral settlement and herds.
    • Impact of leafy spurge on post-Conservation Reserve Program land

      Hirsch, S. A.; Leitch, J. A. (Society for Range Management, 1998-11-01)
      Leafy spurge (Euphorbia esula L.), a noxious weed infests some of the 1.2 million hectares of Conservation Reserve Program (CRP) land in North Dakota. Once established a leafy spurge monoculture will reduce expected CRP benefits and impact returns to some post-CRP land uses. The study estimated statewide direct economic impacts of about 351,000 on post-CRP land maintained in vegetative cover, 1.118 million on post-CRP grazing land, and negligible (assumed 0) on post-CRP cropland, for a total of 1.469 million. Total annual direct and secondary economic impacts to North Dakota's economy were estimated to be 4.665 million, which would support about 57 jobs.
    • Impact of locoweed poisoning on grazing steer weight gains

      Ralphs, M. H.; Graham, D.; Duff, G.; Stegelmeier, B. L.; James, L. F. (Society for Range Management, 2000-01-01)
      Emaciation is one of the clinical signs of locoweed poisoning but few studies have documented impacts of locoweed poisoning on weight gains. Stocker steers (British X Continental cross, 200-210 kg) were grazed on locoweed-infested, short-grass prairie in 1996 and 1997 in northeast New Mexico. Each year, half the steers were averted to locoweed to allow them to graze locoweed-infested pastures without eating locoweed. They did not graze locoweed and steadily gained weight (0.50 kg/day in 1996 and 0.71 kg/day in 1997). The other group of steers were allowed to graze locoweed under natural grazing conditions and became intoxicated. Weight gains were not affected for the first 3 weeks, but thereafter the steers lost weight in both years. In 1996, non-averted steers consumed locoweed for a season average of 20% of bites. They were severely intoxicated and did not begin gaining weight for 50 days after they stopped eating locoweed. Steers in the 1997 trial consumed less locoweed (11% of bites) than those in 1996 and they recovered more rapidly. Seasonal weight gains were 21 to 30 kg less for locoed steers than control steers in 1996 and 1997, respectively. Locoweed poisoning will cause weight loss, and severely intoxicated cattle require a lengthy recover period after they cease grazing locoweed before weight gains resume. Stocker cattle should not be placed on locoweed-infested rangelands until green grass is abundant and locoweed begins to mature.
    • Impact of Native Grasses and Cheatgrass (Bromus tectorum) on Great Basin Forb Seedling Growth

      Parkinson, Hilary; Zabinski, Cathy; Shaw, Nancy (Society for Range Management, 2013-03-01)
      Re-establishing native communities that resist exotic weed invasion and provide diverse habitat for wildlife are high priorities for restoration in sagebrush ecosystems. Native forbs are an important component of healthy rangelands in this system, but they are rarely included in seedings. Understanding competitive interactions between forb and grass seedlings is required to devise seeding strategies that can enhance establishment of diverse native species assemblages in degraded sagebrush communities. We conducted a greenhouse experiment to examine seedling biomass and relative growth rate of common native forb species when grown alone or in the presence of a native bunchgrass or an exotic annual grass. Forb species included bigseed biscuitroot (Lomatium macrocarpum [Nutt. ex Torr. A. Gray] J.M. Coult. Rose), sulphur-flower buckwheat (Eriogonum umbellatum Torr.), hoary aster (Machaeranthera canescens [Pursh] Gray), royal penstemon (Penstemon speciosus Douglas ex Lindl.), and Munro’s globemallow (Sphaeralcea munroana [Douglas ex Lindl.] Spach ex Gray); and neighboring grass species included bottlebrush squirreltail (Elymus elymoides [Raf.] Swezey), Sandberg bluegrass (Poa secunda J. Presl); and cheatgrass (Bromus tectorum L.). Forbs and grasses were harvested after 6, 9, or 12 wk of growth for biomass determination and calculation of relative growth rates (RGR) of forbs. Neither bunchgrass reduced biomass of any forb. RGR was reduced for royal penstemon when grown with either native grass and for Munro’s globemallow when grown with bottlebrush squirreltail. Although only assessed qualitatively, forbs with vertically oriented root morphologies exhibited no reduction in RGR when grown with native grasses, compared to forbs with dense lateral branching, similar to the root morphology of native grasses. Biomass of forbs was reduced by 50% to 91% and RGR by 37% to 80% when grown with cheatgrass. Understanding native forb interactions with native grasses and cheatgrass will aid land managers in selecting effective seed mixes and making better use of costly seed.
    • Impact of plant toxins on fetal and neonatal development: A review

      Panter, K. E.; Keeler, R. F.; James, L. F.; Bunch, T. D. (Society for Range Management, 1992-01-01)
      Many poisonous plants grazed by livestock on ranges and pastures in the western USA are fetotoxic causing fetrl malformations, embryonic or fetal death, abortion, or early parturition. Decreased incidence of plant-induced livestock malformations may be accomplished through grazing management strategies. To develop these strategies one must understand some basic principles of toxicology and teratology such as susceptible livestock species, type of compound and concentration in the plant and its disposition in the animal, dose response, and the susceptible gestational period. Much of this information is known for certain plants; however, additional information will enhance our ability to control livestock losses from these plants. Certain criteria may be established to maximize grazing management methods to minimize teratogenic effects of poisonous plants. When the suspect plant grows in a restricted habitat, poses a hazard only at certain growth stages or when the susceptible period of pregnancy is relatively short, minor adjustments in management methods can be considerably successful in reducing incidence of malformations and subsequent financial loss.
    • Impact of poisonous plant on the livestock industry

      James, L. F.; Nielsen, D. B.; Panter, K. E. (Society for Range Management, 1992-01-01)
      Livestock poisoning by plants is one of the serious causes of economic loss to the livestock industry. Losses can be classified as either direct or indirect. Direct losses include deaths, weight loss, abortions, lengthened calving intervals, decreased efficiency and other effects on the animals. Losses from death and some reproductive losses in the 17 western states are estimated at 340,000,000. In addition to these are the indirect losses such as fencing, herding, supplemental feeding, medical costs, management alterations, and loss of forage which are associated with efforts to prevent or minimize poisoning of livestock by plants. Nearly all plant communities include poisonous plants, thus, most grazing animals are exposed to intoxication. However, the presence of these plants does not cause poisoning. Poisoning is usually associated with management errors, lack of forage due to range conditions, drought, and other events that would cause Livestock to consume vegetation normally unacceptable. Often a sequence of events, such as storm, frost, cold, and other occurrences can influence an animal to where it will eat too much of a toxic plant too fast.
    • Impact of prescribed burning on vegetation and bird abundance at Matagorda Island, Texas

      Van’t Hul, J. T; Lutz, R. S.; Mathews, N. E. (Society for Range Management, 1997-07-01)
      We measured the impact of prescribed summer and winter burns on vegetation characteristics and spring abundance of birds in a Spartina/Paspalum grassland at Matagorda Island National Wildlife Refuge and State Natural Area, Texas, 1993-94. We burned 8 (4 summer burn, 4 winter burn), 122-ha plots. We estimated bird abundance by surveying once a week from March through May at 12-16 fixed-radius point count stations in each plot. We measured forb and grass foliar cover, litter depth, visual obstruction, and woody and residual stem density at each point count station 6-10 months after burning and 18-22 months after burning and found few differences in vegetation between summer and winter burns. Litter depth, visual obstruction, and woody stem density values were greater on control plots 6 to 10 months post-burn. By 18 to 22 months post-burn, only litter depth and visual obstruction remained higher on control plots than on either burn treatment. At 6 to 10 months after burning, wrens were more abundant on control plots and sparrows were more abundant on the burned plots. By 18 to 22 months post-burn, wren abundance had increased on the burned plots, but was still highest on control plots. Sparrow abundance remained highest on burned plots 18-22 months after burning. Precipitation was higher in 1993 than 1994; we believe blackbirds responded more to annual precipitation differences than to burning treatment. In this coastal island grassland, wren abundance was highest on unburned plots and sparrow abundance was highest on burned plots. We suggest that land managers could burn at > 2 year intervals in this grassland without negatively impacting most resident bird species.
    • Impact of Presowing Seed Treatments, Temperature and Seed Coats on Germination of Velvet Bundleflower

      Haferkamp, M. R.; Kissock, D. C.; Webster, R. D. (Society for Range Management, 1984-03-01)
      Seeds with both smooth and rough, apparently scarified, seed coats occur in harvested samples of velvet bundleflower (Desmanthus velutinus Scheele.). To determine the degree of scarification, germination responses of rough and smooth seeds were investigated at 4 night/day temperature regimes, 5/15 degrees C, 10/20 degrees C, 15/25 degrees C, and 20/30 degrees C with a 12-hour photoperiod during the high temperature and with 3 seed treatments, cutting, acid scarification and hot water soak. Rough seed coats appear to be caused by peeling of the cuticular layer on the seed surface. Moisture was imbibed more rapidly by smooth seeds, and total germination of smooth seeds was 31% without treatment, 4 times greater than rough seed germination. Treatments increased germination of smooth seeds two- to four- fold and rough seeds over 10-fold. After treatment, rough seeds germinated significantly (P<.05) better than smooth seeds at all temperature regimes except 5/15 degrees C. Cut and scarified seeds generally germinated more rapidly than water-treated seeds, but total germination was similar for all treatments at warmer temperatures. Germination was only 31% at 5/15 degrees C.
    • Impact of Range Goats on Infiltration Rates in Southwestern Utah

      Gifford, G. F.; Provenza, F. D.; Malechek, J. C. (Society for Range Management, 1983-03-01)
      Three levels of goat browsing on a blackbrush site in southwestern Utah had no significant impact on infiltration rates. The probable reason for these results was the presence of a vesicular soil crust, which is unstable when wet and therefore masks any browsing impacts.
    • Impact of Small Mammal on the Vegetation of Reclaimed Land in the Northern Great Plains

      Hingtgen, T. M.; Clark, W. R. (Society for Range Management, 1984-09-01)
    • Impact of SO2 Exposure on the Response of Agropyron smithii to Defoliation

      Lauenroth, W. K.; Detling, J. K.; Milchunas, D. G.; Dodd, J. L. (Society for Range Management, 1985-01-01)
      Agropyron smithii populations exposed to 3 controlled SO2 concentrations were defoliated either once or twice during the growing season at a light and a heavy intensity. The intensity and frequency of defoliation were most influential in determining growth and tillering responses. Defoliating twice, at either intensity, had a large negative impact on plant growth whereas compensatory growth occurred after defoliating once at either intensity. Sulfur dioxide alone had no significant effect on biomass or the number of tillers, even though sulfur accumulated approximately in proportion to exposure concentration. Sulfur dioxide exposure with the additional influence of defoliation affected both the regrowth of A. smithii in terms of biomass and tiller numbers and forage sulfur concentration. Decreased plant growth in response to SO2 plus defoliation was dependent on defoliation frequency, whereas the effect of SO2 plus defoliation on plant sulfur concentration was positive and negative and depended on a complex interaction of SO2 concentration and defoliation frequency and intensity. The results are discussed in relation to the short- and long-term compensatory growth potential of a system simultaneously exposed to grazing and air pollution and the potential effect on consumers.
    • Impact of Stocking Rate and Rainfall on Sheep Performance in a Desert Steppe

      WangHan, Zhongwu; Jiao, Shuying; Han, Guodong; Zhao, Mengli; Willms, Walter D.; Hao, Xiying; Wang, Jian’an; Din, Haijun; Havstad, Kris M. (Society for Range Management, 2011-05-01)
      Livestock performance is a critical indicator of grassland production systems and is influenced strongly by precipitation and stocking rates. However, these relationships require further investigation in the arid Desert Steppe region of northeastern China. We employed a randomized complete block design with three replications and four grazing treatments (nongrazed exclosure [Control]), lightly grazed [LG], moderately grazed [MG], and heavily grazed [HG]) by sheep in a continuously grazed system (June to November), to test the effect of stocking rate on sheep performance. The planned stocking rates were 0, 0.15, 0.30, and 0.45 sheep ha-1 mo-1, for the control, LG, MG, and HG treatments, respectively. However, actual stocking rates were calculated for each paddock in each year based on a 50-kg sheep equivalent (SE). Annual net primary production (ANPP) was determined at peak standing crop in August 2004 to 2008. Live weight gain was determined for the summer and fall periods, as well as the total grazing period, in each year. ANPP decreased with increasing stocking rate, and daily live weight gain per head decreased linearly with increasing stocking rates over the total grazing period but in a quadratic manner over the summer period with a plateau at the lower rates. Maximum sheep production per unit area over the total grazing season occurred at about 2 SE ha-1 for about a 5-mo grazing period, but individual gains per sheep were predicted to decline after about 1 SE ha-1 presumably because of forage limitations. However, in order to achieve stable annual production, we recommend that the Desert Steppe be grazed at about 0.77 SE ha-1 for a 5-mo period (0.15 SE ha-1 mo-1). This estimate is based on published grazing strategies that consider an average ANPP with a recommended utilization rate of 30%.
    • Impact of Various Range Improvement Practices on Watershed Protection Cover and Annual Production Within the Colorado River Basin

      Hessary, I. K.; Gifford, G. F. (Society for Range Management, 1979-03-01)
      During 1976 a study of annual production and cover (litter + rock + vegetation) on various range improvement practices was conducted in Utah, Colorado, New Mexico, and Arizona. The range improvement practices studied included gully plugs, contour furrowing, pitting, pinyon-juniper chaining, and various sagebrush control treatments. Results from studies of annual production on treated vs untreated sites indicated that: (a) about 33% of the contour furrowed sites had significant increases in annual production. Best responses were found on loam and clay loam soils, while soils of sandy loam or clay texture indicated a poor response to treatment. Soils classified as typical ustifluvents and ustollic haplargids were most favorable in terms of increased production; (b) annual production on pinyon-juniper chainings was significantly increased across a variety of soil types (growth of trees excluded). The greatest increases in production were measured on sites with loam soils classified as typic haplustolls; (c) neither of the two pitting treatments on a clay and a sandy clay loam site indicated increased annual production; (d) less than 50% of the various sagebrush treatments indicated increased annual production. There appears to be a general trend for best responses on loam soils, though significant decreases in production were also indicated on this type of soil; (e) plowing was the least successful sagebrush treatment studied. Best cover responses on the various range improvement practices were found on contour furrowing treatments on sandy clay loam and loam textured soils and on typic torriorthent or ustic torriorthent soil types. Though significant cover increases due to chaining of pinyon and juniper were noted on 57% of the treatments, on a variety of soil textures and soil types, the increases were uniformly small (tree cover included) and no clear pattern emerged with either soil texture or soil type. Only about 20% of the various sagebrush treatments showed significant increases in cover; 10% indicated decreased cover, and there was no impact on cover on the remaining 70% of the treatments. Pitting treatments in this study had no impact on cover. Age of contour furrow treatments made little difference as to whether there was a significant increase or decrease in either production or cover. Cover data from pinyon-juniper chainings indicate either that significant increases in cover (if they occur) are slightly more dramatic on more recent teatments, or that treatments approximately 11 years old represent conditions most ideal for enhanced cover. The former interpretation is probably more nearly correct. Production data suggests that pinyon-juniper sites chained since 1964 are not as favorable in terms of increased production as those chained prior to 1964. Age of sagebrush treatment had no impact on significant changes in cover; however, a general trend indicated that production increases are slightly higher for more recent sagebrush ripping and sagebrush chaining treatments than for older ones.
    • Impact of Wildfire on Three Perennial Grasses in South-Central Washington

      Uresk, D. W.; Cline, J. F.; Rickard, W. H. (Society for Range Management, 1976-07-01)
      In a south-central Washington sagebrush-bluebunch wheatgrass community, bluebunch wheatgrass responded to burning by increased vegetative and reproductive performance. Burning decreased the vegetative and reproductive vigor of Cusick bluegrass and Thurber needlegrass.
    • Impact on Associated Vegetation of Controlling Tall Larkspur

      Cronin, E. H. (Society for Range Management, 1976-05-01)
      Herbicide treatments that effectively control tall larkspur also convert the tall-forb community to a grass-dominated community. The composition of the grass community is determined more by the grazing system imposed on the treated area than by the herbicide treatments. Early grazing reduces mountain brome and increases letterman needlegrass. With protection from grazing, the converted grass community can produce abundant high-quality forage and watershed cover superior to that of the former larkspur-dominated tall-forb community.