Now showing items 3429-3448 of 20719

    • Calculating Foraging Area Using Global Navigation Satellite System (GNSS) Technology

      Anderson, Dean M. (Society for Range Management, 2014-12-01)
      On the Ground • Optimum forage utilization on animal-dominated landscapes can only occur when stocking rate (SR) and stocking density (SD) are considered and managed simultaneously. • Landscapes with foraging animals contain vegetation ranging from unused to over-used even under a proper SR. • The global navigation satellite system (GNSS) technology has catapulted our understanding of spatial–temporal management of free-ranging livestock into a 24/7 opportunity. • Location-specific data will improve management of stocked landscapes, both ecologically and economically. • GNSS data from instrumented animals provides an opportunity to understand when and where a landscape is used to improve animal distribution. • A proper SR and management of animal distribution (i.e., SD) will facilitate adaptive management of animal dominated landscapes.
    • Calculating Grazing Intensity for Maximum Profit on Ponderosa Pine Range in Northern Arizona

      Pearson, H. A. (Society for Range Management, 1973-07-01)
      The profit formula is based on forage production, digestibility and utilization, animal weight and daily gain, costs per animal day, and beef prices. Rangeland producing 500-1,000 lb forage per acre would produce maximum profit with moderate utilization.
    • Calculating Sediment Compaction for Radiocarbon Dating of Intertidal Sediments

      Bird, M. I.; Fifield, L. K.; Chua, S.; Goh, B. (Department of Geosciences, The University of Arizona, 2004-01-01)
      This study estimates the maximum and minimum degrees of autocompaction for radiocarbon-dated Holocene mangrove sediments in Singapore, in order to correct apparent sediment accretion rates for the effects of sediment compression due to autocompaction. Relationships developed for a suite of modern (surface) sediment samples between bulk density, particle-size distribution, and organic matter content were used to estimate the initial (uncompacted) bulk density of buried and variably compressed Holocene sediments, based on the grain-size distribution and organic matter content of the sediment. The difference between measured (compacted) and initial (uncompacted) bulk density of each buried sediment interval can be interpreted as the amount of length shortening experienced by each interval since burial. This allows the elevation of samples selected for 14C dating to be corrected for the effects of autocompaction of the underlying sediment sequence, so that accurate estimates of vertical sediment accretion rates can be calculated. The 3 Holocene mangrove sequences analyzed and dated for this study ranged in age from 2000 to 8500 cal BP. The effects of autocompaction are significant, even in comparatively thin sequences, with subsidence of up to 56 cm calculated for carbon-dated samples presently 2 m above incompressible basement. The vertical sediment accretion rates for these mangrove sequences ranged from 0.99 to 6.84 mm/yr and carbon sequestration rates ranged from 0.9 to 1.7 t/ha/yr, all within the range observed for comparable Holocene and modern mangrove sediments elsewhere.
    • Calculating Yearlong Carrying Capacity: An Algebraic Approach

      Workman, J. P.; MacPherson, D. W. (Society for Range Management, 1973-07-01)
      Estimates of yearlong carrying capacity obtained by three different techniques are compared in terms of accuracy as measured by actual carrying capacity of a northern Utah cattle ranch. A new "algebraic" approach appears superior to two established techniques currently in use.
    • Calculation of Past Dead Carbon Proportion and Variability by the Comparison of AMS 14C and TIMS U/Th Ages on Two Holocene Stalagmites

      Genty, Dominique; Massault, Marc; Gilmour, Mabs; Baker, Andy; Verheyden, Sophie; Keppens, Eddy (Department of Geosciences, The University of Arizona, 1999-01-01)
      Twenty-two radiocarbon activity measurements were made by accelerator mass spectrometry (AMS) on 2 Holocene stalagmites from Belgium (Han-stm lb) and from southwest France (Vil-stm lb). Sixteen thermal ionization mass spectrometric (TIMS) U/Th measurements were performed parallel to AMS analyses. The past dead carbon proportion (dcp) due to limestone dissolution and old soil organic matter (SOM) degradation is calculated with U/Th ages, measured calcite 14C activity and atmospheric 14C activity from the dendrochronological calibration curves. Results show that the dcp is different for the 2 stalagmites: between 10,800 and 4780 yr from present dcp = 17.5% (sigma = 2.4; n = 10) for Han-stm lb and dcp = 9.4% (sigma = 1.6; n = 6) between 3070 and 520 yr for Vil-stmlb. Despite a broad stability of the dcp during the time ranges covered by each sample, a slight dcp increase of about 5.0% is observed in the Han-stmlb sample between 8500 and 5200 yr. This change is synchronous with a calcite delta-13C increase, which could be due to variation in limestone dissolution processes possibly linked with a vegetation change. The dcp and delta-13C of the 2 studied samples are compared with 5 other modern stalagmites from Europe. Results show that several factors intervene, among them: the vegetation type, and the soil saturation leading to variable dissolution process systems (open/closed). The good correlation (R2 = 0.98) between the U/Th ages and the calibrated 14C ages corrected with a constant dcp validates the 14C method. However, the dcp error leads to large 14C age errors (i.e. 250-500 yr for the period studied), which is an obstacle for both a high-resolution chronology and the improvement of the 14C calibration curves, at least for the Holocene.
    • Calendar Age of Lisakovsky Timbers Attributed to Andronovo Community of Bronze Age in Eurasia

      Panyushkina, Irina P.; Mills, Barbara J.; Usmanova, Emma R.; Cheng, Li (Department of Geosciences, The University of Arizona, 2008-01-01)
      We measured radiocarbon ages of 22 decadal replications and 1 bulk group from 5 tree-ring specimens using acid-base-acid pretreatment and accelerator mass spectrometry (AMS). The study has the goal of refining the precision and resolution of a segment of the conventional Bronze Age chronology in the Eurasian steppe attributed to the multicultural community known as Andronovo. The archaeological timbers were gathered from 3 cemeteries at the Lisakovsky cluster of sites in Kazakhstan, where there is a prominent Andronovo occurrence that appears to show evidence of overlapping Alakul and Fedorovo cultures in the southern margin of the Eurasian steppe. The new set of Andronovo calendar dates derived from 14C wiggles and a composite floating tree-ring chronology places the cultural overlap from 1780 to 1660 cal BC. Results indicate older ages of artifacts from the Lisakovsky site than were previously determined by the typological chronology, shifting them from the Late Bronze Age to also include the transition between the Middle and Late Bronze Age. The chronological order of the Lisakovsky cemeteries provides strong evidence of contemporaneity of the Alakul and Fedorovo cultures in the Tobol River Valley for a portion of the 120-yr period of occupation. We discuss an application of the dated Alakul-Fedorovo overlap to the relationship and origin of different groups of the Andronovo community in the Ural region. Our results demonstrate the substantial power that tree rings from Bronze Age timbers provide for developing a precise and highly resolved calendar chronology of prehistoric human occupation in the Eurasian steppe during the 2nd millennium BC.
    • Calf and Lamb Feeding Experiments at U. of A. Farm

      Stanley, E. B. (College of Agriculture, University of Arizona (Tucson, AZ), 1926-12)
    • Calf Feeding Test Explained to Stockmen

      Stanley, E. B.; University of Arizona (College of Agriculture, University of Arizona (Tucson, AZ), 1926-05)
    • CalibETH: An Interactive Computer Program for the Calibration of Radiocarbon Dates

      Niklaus, Thomas R.; Bonani, Georges; Simonius, Markus; Suter, Martin; Wölfli, Willy (Department of Geosciences, The University of Arizona, 1992-01-01)
      A computer program for convenient calibration of radiocarbon dates has been developed. The program has a simple user interface, which includes pull-down menus, windows and mouse support. All important information, such as calibration curves, probability density function and results, in text form, are displayed on the screen and easily can be rearranged by the user. Two versions of CalibETH, one for an IBM-PC and one for the Macintosh, are available. CalibETH runs under the graphics interface, GEM, from Digital Research, on an IBM PC.
    • Calibrated 14C Ages of Jomon Sites, NE Japan, and Their Significance

      Omoto, K.; Takeishi, K.; Nishida, S.; Fukui, J. (Department of Geosciences, The University of Arizona, 2010-01-01)
      The traditional archaeological chronology in the Japanese Islands during the Jomon period was essentially based on the relative age given to cord-impressed patterns marked on pottery, as well as the shape of the pottery and the thickness of the cultural layers that were excavated. We aimed to correlate the classical archaeological chronology with calibrated radiocarbon dates, to posit a new chronology for the Jomon period in northeastern Japan. We calibrated 80 accelerator mass spectrometry (AMS) 14C dates from NE Japan and reconstructed a chronological timetable for Hokkaido and the Tohoku District. We collected 43 samples from 5 shellmounds and 2 archaeological sites on Hokkaido Island and 4 shellmounds in the Tohoku District in order to determine the calibrated age of their sites. R values used on Hokkaido Island and the Tohoku District were between 282 and -158 yr and between 0 and -40 yr, respectively. The large R value for the eastern part of Hokkaido Island indicates the influence of the Oyashio Current, while an anomalous R value was obtained from northern Hokkaido Island. These figures show larger apparent R values than those from southwest Japan (Nakamura et al. 2007). The calibrated Jomon period in the investigated area was from 2000 to 200 yr younger than the previous chronology. Calibrated 14C ages of the shellmounds investigated ranged between ~6000 and 3000 yr, correlating to the Early Jomon and Final Jomon periods as indicated by the former archaeological chronology of Honshu Island.
    • Calibrated 14C Dates in Central Europe - Same as Elsewhere?

      Freundlich, J. C.; Schmidt, Burghart (American Journal of Science, 1983-01-01)
      14C dating results derived from an absolutely-dated 471-year tree-ring sequence from central European oak show a trend towards somewhat older dates than those for bristlecone pine tree rings of the same age, but similar to those for Egyptian historical samples. Differences visible between these trend lines are not relevant considering the standard errors proposed by Clark (1975).
    • Calibrating fecal NIRS equations for predicting botanical composition of diets

      Walker, J. W.; McCoy, S. D.; Launchbaugh, K. L.; Fraker, M. J.; Powell, J. (Society for Range Management, 2002-07-01)
      The objectives of this study were to investigate the use of near infrared spectroscopy (NIRS) of fecal samples for predicting the percentage of mountain big sagebrush (Artemisia tridentata Nutt. ssp. vaseyana (Rydb) Beetle) in sheep diets and to quantify the limitations of using NIRS of fecal samples to predict diet composition. Fecal material from a sheep feeding trial with known levels of sagebrush and several background forages was used to develop fecal NIRS calibration equations validated with fecal material from 2 other sheep feeding trials with known levels of sagebrush in the diets. The 1996 calibration trial varied the level of sagebrush, alfalfa, and grass hay in the diets. The 1998 trial compared frozen to air-dried sagebrush. The Wyoming trial was a metabolism study using frozen sagebrush. Trials used different levels of sagebrush varying from 0 to 30% of the diet in increments of 4 to 10 percentage points. Internal validation of the 1996 trial with a subset of the samples not used for calibration showed that when predicted samples are from the same population as the calibration samples, this procedure can accurately predict percent sagebrush (R2 = 0.96, SEP = 1.6). However, when predicted samples were from a different population than calibration samples, accuracy was much less, but precision was not affected greatly. Low accuracy was caused by a compression of the range of data in the predicted values compared to the reference values, and the predicted sagebrush levels in the diet should be considered to represent an interval scale of measurement. Modified partial least squares regression resulted in better calibration than stepwise regression, and calibration data sets with only high, low, and no sagebrush resulted in calibrations almost as good as data sets with several intermediate levels of sagebrush. High values of the H statistic were related to low precision but did not affect the accuracy of predictions. We believe the interval scale of measurement will contain sufficient information for the purpose of addressing many questions on rangelands.
    • Calibrating New Zealand Radiocarbon Dates of Marine Shells

      McFadgen, B. G.; Manning, M. R. (Department of Geosciences, The University of Arizona, 1990-01-01)
      Radiocarbon activity of 11 modern marine shell samples from the New Zealand region is enhanced compared with the surface layers of the average world ocean. The measured enhancement, Delta-R, is equivalent to -31 +/13 years. On this basis, the Institute of Nuclear Sciences will now use a value of -30 years in reporting calibrated ages for marine shell samples.
    • Calibrating the Scales of Justice: Balancing Fundamental Freedoms in United States and Canada [Note]

      Nunez, Rene (The University of Arizona James E. Rogers College of Law (Tucson, AZ), 1997)
    • Calibration 1993

      Department of Geosciences, The University of Arizona, 1993-01-01
    • Calibration 1993

      Department of Geosciences, The University of Arizona, 1994-01-01
    • Calibration 1993

      Department of Geosciences, The University of Arizona, 1994-01-01
    • Calibration 1993

      Department of Geosciences, The University of Arizona, 1995-01-01
    • Calibration Commentary

      Blockley, S. P. E.; Housley, R. A. (Department of Geosciences, The University of Arizona, 2009-01-01)
      Radiocarbon is by far and away the most widely used dating tool in the Late Quaternary. Hundreds of key papers rely on the method to provide absolute and relative chronological information on important topics, including the late evolution of our own species (e.g. Higham et al. 2006a) and the timing and nature of abrupt climatic changes during the last glaciation (Lowe et al. 2001). Calibration of 14C determinations is an essential part of the dating process, and the implications of calibration can lead to significant differences in the interpretation of important processes (Blockley et al. 2006). Any development that enhances the accuracy, precision, or time coverage of the calibration curves is therefore to be welcomed. Since the early 1980s, there has been periodic publication of carefully vetted data in the form of internationally recognized consensus calibration curves that have allowed 14C users to convert their raw 14C determinations into calendar ages (Klein et al. 1982; Stuiver and Reimer 1986, 1993; Stuiver et al. 1998; Reimer et al. 2004). In the beginning, the basis on which this was done was easy to understand, 14C measurements were made on tree rings and the absolute calendar age came from counting annual growth rings. Although not without its complexities, the terrestrial tree-ring approach remains the most certain method and is at the heart of calibration process in the period 0-12.4 cal kyr. However, for periods beyond the limit of the tree-ring sequences the situation was significantly more problematic, and at times, even controversial.
    • Calibration Curve for Short-Lived Samples, 1900-3900 BC

      Vogel, J. C.; van der Plicht, Johannes (Department of Geosciences, The University of Arizona, 1993-01-01)