Now showing items 9226-9245 of 20709

    • I Did It—For Range Sake!

      Linhart, Brandi (Society for Range Management, 1988-12-01)
    • I Feel Guilty! Studying isn't supposed to be such fun.

      Carle, Becky; School of Home Economics (College of Agriculture, University of Arizona (Tucson, AZ), 1969)
    • I Know the Cattle: A Poem for Joyce

      Bump, Katie (Society for Range Management, 1989-12-01)
    • I'll Farm Where Salome Danced

      Nolan, Wilson E.; Department of Agronomy (College of Agriculture, University of Arizona (Tucson, AZ), 1969)
    • I'm Not Satisfied With the Journal…!

      Schultz, A. M. (Society for Range Management, 1958-05-01)
    • I-Xe measurements of CAIs and chondrules from the CV3 chondrites Mokoia and Vigarano

      Whitby, J. A.; Russell, S. S.; Turner, G.; Gilmour, J. D. (The Meteoritical Society, 2004-01-01)
      I-Xe analyses were carried out for chondrules and refractory inclusions from the two CV3 carbonaceous chondrites Mokoia and Vigarano (representing the oxidized and reduced subgroups, respectively). Although some degree of disturbance to the I-Xe system is evident in all of the samples, evidence is preserved of aqueous alteration of CAIs in Mokoia 1 Myr later than the I-Xe age of the Shallowater standard and of the alteration of a chondrule (V3) from Vigarano ~0.7 Myr later than Shallowater. Other chondrules in Mokoia and Vigarano experienced disturbance of the I-Xe system millions of years later and, in the case of one Vigarano chondrule (VS1), complete resetting of the I-Xe system after decay of essentially all 129I, corresponding to an age more than 80 Myr after Shallowater. Our interpretation is that accretion and processing to form the Mokoia and Vigarano parent bodies must have continued for at least 4 Myr and 80 Myr, respectively. The late age of a chondrule that shows no evidence for any aqueous alteration or significant thermal processing after its formation leads us to postulate the existence of an energetic chondrule-forming mechanism at a time when nebular processes are not expected to be important.
    • Iberlin Brothers Fight Low Profits and Predators as Sheep Market Rises

      Slocum, Kenneth G. (Society for Range Management, 1979-04-01)
    • Ibitira: A basaltic achondrite from a distinct parent asteroid and implications for the Dawn mission

      Mittlefehldt, D. W. (The Meteoritical Society, 2005-01-01)
      I have done a detailed petrologic study of Ibitira, a meteorite that has been classified as a basaltic eucrite since 1957. The mean Fe/Mn ratio of pyroxenes in Ibitira with <10 mole% wollastonite component is 36.4 +/- 0.4; this value is well resolved from those of similar pyroxenes in five basaltic eucrites studied for comparison, which range from 31.2 to 32.2. Data for the latter five eucrites completely overlap. Ibitira pyroxenes have lower Fe/Mg than the basaltic eucrite pyroxenes; thus, the higher Fe/Mn ratio does not reflect a simple difference in oxidation state. Ibitira also has an oxygen isotopic composition, alkali element contents, and a Ti/Hf ratio that distinguish it from basaltic eucrites. These differences support derivation from a distinct parent asteroid. Thus, Ibitira is the first recognized representative of the fifth known asteroidal basaltic crust, the others being the HED, mesosiderite, angrite, and NWA 011 parent asteroids. 4 Vesta is generally assumed to be the HED parent asteroid. The Dawn mission will orbit 4 Vesta and will perform detailed mapping and mineralogical, compositional, and geophysical studies of the asteroid. Ibitira is only subtly different from eucritic basalts. A challenge for the Dawn mission will be to distinguish different basalt types on the surface and to attempt to determine whether 4 Vesta is indeed the HED parent asteroid.
    • ICARDA's Rangeland Ecology and Management Research Strategy for Nontropical Dry Areas

      Louhaichi, Mounir (Society for Range Management, 2011-08-01)
    • Ice dynamics of the Allan Hills meteorite concentration sites revealed by satellite aperture radar interferometry

      Coren, F.; Delisle, G.; Sterzai, P. (The Meteoritical Society, 2003-01-01)
      The ice flow conditions of a 100 x 100 km area of Victoria Land, Antarctica were analyzed with the synthetic aperture radar (SAR) technique. The area includes a number of meteorite concentration sites, in particular the Allan Hills ice fields. Regional ice flow velocities around the Mid- western and Near-western ice fields and the Allan Hills main ice field are shown to be less than or equal to 2.5 m yr-1. These sites are located on a horseshoe-shaped area that bounds an area characterized by higher ice flow velocities of up to 5 m yr-1. Meteorite find locations on the Elephant Moraine are located in this "high ice flow" area. The SAR derived digital elevation model (DEM) shows atypical low surface slopes for Antarctic conditions, which are the cause for the slow ice movements. Numerous ice rises in the area are interpreted to cap sub-ice obstacles, which were formed by tectonic processes in the past. The ice rises are considered to represent temporary features, which develop only during warm stages when the regional ice stand is lowered. Ice depressions, which develop in warm stages on the lee side of ice rises, may act as the sites of temporary build-up of meteorite concentrations, which turn inoperative during cold stages when the regional ice level rises and the ice rises disappear. Based on a simplified ice flow model, we argue that the regional ice flow in cold stages is reduced by a factor of at least 3.
    • Ice-Core Dating of the Pleistocene/Holocene Boundary Applied to a Calibration of the 14C Time Scale

      Hammer, Claus U.; Clausen, Henrik B.; Tauber, Henrik (American Journal of Science, 1986-01-01)
      Seasonal variations in 18O content, in acidity, and in dust content have been used to count annual layers in the Dye 3 deep ice core back to the Late Glacial. In this way the Pleistocene/Holocene boundary has been absolutely dated to 8770 BC with an estimated error limit of +/- 150 years. If compared to the conventional 14C age of the same boundary a value of Delta-14C = 53 +/- 13 per mil is obtained. This Delta-14C value suggests that 14C levels during the Late Glacial were not substantially higher than during the Postglacial.
    • Idaho Rangeland Resource Commission: Commitment to Rangeland Education

      Hyde, Gretchen; Crane, Kelly (Society for Range Management, 2011-08-01)
    • Idaho State Parks: Discovering the Undiscovered America

      Just, Rick (Society for Range Management, 1986-10-01)
    • Ideal Free Distributions of Mobile Pastoralists in Multiple Seasonal Grazing Areas

      Moritz, M.; Hamilton, I. M.; Scholte, P.; Chen, Y. -J. (Society for Range Management, 2014-11)
      The pastoral system in the Far North Region of Cameroon is best described as an open system in which mobile pastoralists have open access to common-pool grazing resources. We hypothesized that there is a self-organizing management system of open access to common-pool grazing resources and predicted that we would find an Ideal Free Distribution (IFD) of mobile pastoralists within seasonal grazing areas. In this paper we used mobility data and remote sensing data from two seasonal grazing areas at the end of the dry season in three consecutive years to evaluate that hypothesis. We found evidence of an IFD in the two seasonal grazing areas of the Logone Floodplain and the Lake Maga area. These findings offer further support for our hypothesis that there is a complex adaptive system in which pastoralists distribute themselves effectively over available grazing resources. © 2014 Society for Range Management
    • The Ideal Home

      College of Agriculture, University of Arizona (Tucson, AZ), 1926-10
    • Identification and Creation of Optimum Habitat Conditions for Livestock

      Bailey, Derek W. (Society for Range Management, 2005-03-01)
      Optimum habitat condition is a concept typically used for wildlife rather than livestock. The definition for optimal livestock habitat will vary with management objectives. Abiotic factors, such as topography, water availability, and thermal cover, affect animal performance and uniformity of grazing. Livestock usually prefer gentle slopes and avoid traveling long horizontal and vertical distances to water. Shade and nearby water are used for thermoregulation when temperatures are high, and topographic relief and woody vegetation can be used for thermal cover during cooler temperatures. Biotic factors, such as forage quality and quantity, influence spatial grazing preferences and affect animal performance. Livestock prefer areas with higher forage quality and quantity. Uniformity of grazing may be greater in homogeneous vegetation, but animal performance may be greater in heterogeneous vegetation, especially at lower stocking rates. Livestock grazing patterns have been predicted using multiple regression and other models, but their success has typically been limited to a specific site. Managers can improve livestock habitat conditions by changing abiotic attributes of the pastures, such as developing water, building structures for thermal cover, and changing biotic attributes of the pasture through burning, fertilizing, varying stocking rates, and manipulating grazing systems. Managers can also choose animals that are more adapted to specific rangeland conditions. Practices such as strategic supplementation and herding can modify livestock behavioral patterns to use more of the available habitat. The spatial and temporal variability of rangeland requires multiple management practices to optimize use of livestock habitat.  
    • Identification and Taxonomy of Tamarix (Tamaricaceae) in New Mexico

      Allred, Kelly W.; Range Science Herbarium, Department of Animal & Range Sciences, New Mexico State University (University of Arizona (Tucson, AZ), 2002-12)
      The identity and distribution of Tamarix in New Mexico is reviewed, with keys and distribution maps. Four species are found in the state: T. aphylla, T. chinensis (including T. ramosissima), T. gallica, and T. parviflora.
    • Identification of mercurian volcanism: Resolution effects and implications for MESSENGER

      Milkovich, S. M.; Head, J. W.; Wilson, L. (The Meteoritical Society, 2002-01-01)
      The possibility of volcanism on Mercury has been a topic of discussion since Mariner 10 returned images of half the planet's surface showing widespread plains material. These plains could be volcanic or lobate crater ejecta. An assessment of the mechanics of the ascent and eruption of magma shows that it is possible to have widespread volcanism, no volcanism on the surface whatsoever, or some range in between. It is difficult to distinguish between a lava flow and lobate crater ejecta based on morphology and morphometry. No definite volcanic features have been identified on Mercury. However, known lunar volcanic features cannot be identified in images with similar resolutions and viewing geometries as the Mariner 10 dataset. Examination of high resolution, low sun angle Mariner 10 images reveals several features which are interpreted to be flow fronts; it is unclear if these are volcanic flows or ejecta flows. This analysis implies that a clear assessment of volcanism on Mercury must wait for better data. MESSENGER will take images with viewing geometries and resolutions appropriate for the identification of such features.