• A "grass-roots" effort for the future

      Gordon, Kindra (Society for Range Management, 2003-04-01)
    • A "mesosiderite" rock from northern Siberia, Russia: Not a meteorite

      Treiman, A. H.; Lindstrom, D. J.; Schwandt, C. S.; Franchi, I. A.; Morgan, M. L. (The Meteoritical Society, 2002-12-01)
      A possible mesosiderite meteorite was found in the area of the Putorana Plateau, Noril'sk district, Siberia, Russia. Although this rock resembles a mesosiderite in its hand-sample aspect and in having Ni-bearing iron metal, it is not a meteorite. This inference is based on the lack of a fusion crust, the lack of cosmogenic nuclides, oxygen with terrestrial isotope ratios, and several mineral chemical criteria. Most likely, the rock is from the iron-metal-bearing basalts of the Siberian Trap basalt sequence, which are mined for their base and platinum-group metals. Mesosiderite imposters like this may be recognized by (1) the presence of Cu metal in hand sample or as microscopic blebs in the low-Ni metal (kamacite), (2) the absence ofhigh-Ni metal (taenite), and (3) the presence of iron carbide (cohenite) enclosing the kamacite. Even if these macroscopic tests are inconclusive, isotopic and mineral chemical tests will also distinguish rocks like this from mesosiderites.
    • A 14C Calibration with AMS from 3500 to 3000 BC, Derived from a New High-Elevation Stone-Pine Tree-Ring Chronology

      Dellinger, Franz; Kutschera, Walter; Nicolussi, Kurt; Schießling, Peter; Steier, Peter; Wild, Eva Maria (Department of Geosciences, The University of Arizona, 2004-01-01)
      High-precision radiocarbon accelerator mass spectrometry (AMS) measurements of a new high-altitude stone-pine tree-ring chronology from the European Alps were performed for a 500-yr stretch in the second half of the 4th millennium BC. A 14C calibration curve with a typical 1-sigma uncertainty of about 20 14C yr was achieved. Although the general agreement of our data set with INTCAL98 is very good (confirming once more that INTCAL98 is also proper for calibration of samples of extraordinary sites), we found small deviations of 17 +/5 14C yr, indicating possible seasonal effects of the delayed growing season at high altitude.
    • A 14C Electronic Measurement System with a Microcomputer

      Walanus, Adam (American Journal of Science, 1986-01-01)
      Even though the reliability of equipment has improved, the quality of measurement should still be checked. This task may be performed by a microcomputer with the physicist's intervention only when an error in measurement is detected.
    • A 23-Year Retrospective Blind Check of Accuracy of the Copenhagen Radiocarbon Dating System

      Rasmussen, Kaare L.; Tauber, Henrik; Bonde, Niels; Christensen, Kjeld; Theodórsson, Páll (Department of Geosciences, The University of Arizona, 1999-01-01)
      A 23-yr record of the measuring accuracy of the Copenhagen radiocarbon dating laboratory has retrospectively been provided through a true blind test. A total of 92 samples of oak from old tree trunks were dated in the period 1971 to 1993 and their dendrochronological age determined independently. The 14C activity of the dendrochronological samples measured in the Copenhagen radiocarbon laboratory was compared to the activity of the tree rings of the same age measured by Stuiver and Pearson (1993) for calibration purposes. The average difference was found to be 54 +/72 14C yr. The results further indicate that the actual standard deviation is only 7% higher than that quoted by the laboratory. The investigation has shown a long-term stability of laboratory accuracy with no systematic laboratory variations either with respect to sample age or to the time of measurement from 1971 to 1993.
    • A 3-Year Evaluation of Taste Aversion Coyote Control in Saskatchewan

      Gustavson, C. R.; Jowsey, J. R.; Milligan, D. N. (Society for Range Management, 1982-01-01)
      Taste aversion programs using lithium chloride (LiCl) in sheep baits and carcasses have been applied in Washington to one sheep herd for 2 years; applications have been made in California and in Saskatchewan on 46 herds over 3 years. Ten of these 46 herds were available for statistical analysis, indicating a significant reduction in the percent of sheep lost to coyotes. All applications have suggested reduced sheep losses to coyotes (Canis latrans). This method of predation control may cost less than traditional techniques, save sheep, and should allow coyotes to carry out positive functions in the ecosystem.
    • A 30,000-Year Pollen and Radiocarbon Record from Highland Sumatra as Evidence for Climatic Change

      Maloney, B. K.; McCormac, F. G. (Department of Geosciences, The University of Arizona, 1995-01-01)
      We examine the pollen analytical and 14C sequences from two Sumatra highland sites, Pea Bullok (2 degrees 15'N, 99 degrees 02'E) and Danau di-Atas (1 degree 04'S, 100 degrees 46'E). The pollen diagrams do not correlate particularly well, possibly because two of the samples from Danau di-Atas analyzed by radioactive decay counting earlier should be infinite. Other complications are differences in the type of site, local topography, pollen sums used and difficulty in distinguishing between pollen taxa from local and regional vegetation. The older material from Pea Bullok was AMS dated.
    • A 36Cl Profile in Greenland Ice from AD 1265 to 1865

      Conard, N. J.; Gove, H. E.; Elmore, David (Department of Geosciences, The University of Arizona, 1989-01-01)
      We have measured the concentration of 36Cl in 67 samples from the upper portion of the Camp Century ice core. The profile extends from AD 1265 to 1865 and covers the times of the Wolf (AD 1282-1342), Spoerer (AD 1416-1534) and Maunder (AD 1645-1715) minima in sunspot number. Although the profile exhibits much short-term variation, a smoothed plot of the data shows a strong peak in 36Cl concentration over the time of the Maunder Minimum. The deeper part of the core suggests increased deposition of 36Cl over the periods of the Wolf and Spoerer minima. The time resolution of the profile is inadequate for testing for an 11-year periodicity in our data. The data augment evidence from 10Be and 14C studies which indicate solar modulation of radioisotope production. Since, however, much of the short-term variation of 36Cl seems to be independent of solar activity, other factors must affect the deposition of 36Cl in ice. These variations could be due in part to mechanisms affecting the transport of 36Cl in the atmosphere. Based on our data from Camp Century, we calculate an average input of 36Cl of 24 atoms/m2 sec.
    • A 40,000-Year Varve Chronology from Lake Suigetsu, Japan: Extension of the 14C Calibration Curve

      Kitagawa, Hiroyuki; van der Plicht, Johannes (Department of Geosciences, The University of Arizona, 1998-01-01)
      A sequence of annually laminated sediments is a potential tool for calibrating the radiocarbon time scale beyond the range of the absolute tree-ring calibration (11 ka). We performed accelerator mass spectrometric (AMS) 14C measurements on >250 terrestrial macrofossil samples from a 40,000-yr varve sequence from Lake Suigetsu, Japan. The results yield the first calibration curve for the total range of the 14C dating method.
    • A 40-year record of tree establishment following chaining and prescribed fire treatments in singleleaf pinyon (Pinus monophylla) and Utah juniper (Juniperus osteosperma) woodlands

      Bristow, N. A.; Weisberg, P. J.; Tausch, R. J. (Society for Range Management, 2014-07)
      Chaining and prescribed fire treatments have been widely applied throughout pinyon-juniper woodlands of the western United States in an effort to reduce tree cover and stimulate understory growth. Our objective was to quantify effects of treatment on woodland recovery rate and structure and the relative dominance of the two major tree species in our Great Basin study area, singleleaf pinyon (Pinus monophylla Torr. & Frém.) and Utah juniper (Juniperus osteosperma [Torr.] Little). We resampled plots after a 40-yr interval to evaluate species-specific differences in tree survivorship and establishment from posttreatment age structures. Tree age data were collected in 2008 within four chained sites in eastern Nevada, treated in 1958, 1962, 1968, and 1969 and originally sampled in 1971. The same data were collected at five prescribed burn sites treated in 1975 and originally sampled in 1976. All chained sites had greater juniper survival than pinyon survival immediately following treatment. Chained sites with higher tree survival also had the greatest amount of new tree establishment. During the interval between treatment and the 2008 sampling, approximately four more trees per hectare per year established following chaining than following fire. Postfire tree establishment only occurred for the initial 15 yr and was dominated by juniper. Establishment after chaining was dominated by juniper for the first 15 yr but by pinyon for 15-40 yr following treatment. Results support an earlier successional role for juniper than for pinyon, which is more dependent upon favorable microsites and facilitation from nurse shrubs. Repeated chaining at short intervals, or prescribed burning at infrequent intervals, will likely favor juniper dominance. Chaining at infrequent intervals (> 20-40 yr) will likely result in regained dominance of pinyon. Chaining treatments can be rapidly recolonized by trees and have the potential to create or amplify landscape-level shifts in tree species composition. © 2014 The Society for Range Management.
    • A 435-year-long European black pine (Pinus nigra) chronology for the central-western Balkan region

      Poljanšek, S.; Ballian, D.; Nagel, T.A.; Levanič, T. (Tree-Ring Society, 2012-01)
      We describe the development of the first black pine (Pinus nigra Arnold) regional chronology for the central-western Balkan area, Bosnia and Herzegovina (BiH), based on seven site chronologies from different parts of the country. Pointer-year analysis identified a common signal (possibly climate) in the site chronologies—at least five positive (1876, 1930, 1941, 1969) and nine negative pointer years (1874, 1880, 1891, 1931, 1943, 1963, 1971, 1987, 2000) are common to all seven study sites. Site chronologies were compared using statistical parameters and visual crossdating, from which we constructed a 435-year-long tree-ring width chronology for P. nigra for BiH and compared it with existing P. nigra chronologies from Montenegro, Greece, Albania, Austria (Vienna region), and France (Corsica). The resulting statistical and visual similarity indicated that the chronology has a strong regional signal and therefore can be included in the dendrochronological network for P. nigra for the Western Balkans.
    • A Balancing Act

      Frisina, Michael R.; Wambolt, Carl L.; Sowell, Bok; Knapp, Stephen J.; Sullivan, Mark; Johnson, Carolyn (Society for Range Management, 2001-06-01)
    • A Basis for Conservation Lease of Rangeland on the Edwards Plateau

      Huss, D. L. (Society for Range Management, 1955-09-01)
    • A Basis for Relative Growth Rate Differences Between Native and Invasive Forb Seedlings

      James, Jeremy J.; Drenovsky, Rebecca E. (Society for Range Management, 2007-07-01)
      The ability of invasive plants to achieve higher relative growth rates (RGR) than their native counterparts has been widely documented. However, the mechanisms allowing invasives to achieve higher RGR are poorly understood. The objective of this study was to determine the basis for RGR differences between native and invasive forbs that have widely invaded nutrient-poor soils of the Intermountain West. Six native and 6 invasive forbs were seeded in pots in a greenhouse, and 4 harvests were conducted over a 2-month period. These 4 harvests were used to calculate RGR and the components of RGR, net assimilation rate (rate of dry matter production per unit leaf area), leaf area ratio (LAR, leaf area per unit total plant mass), leaf mass ratio (the proportion of biomass allocated to leaves), and specific leaf area (SLA, leaf area per unit leaf biomass). Mean RGR of the 12 study species ranged between 0.04 and 0.15 g g-1 d-1 but was significantly higher for invasive forbs compared to native forbs (P = 0.036). The higher RGR achieved by invasive forbs was due mainly to a greater SLA and LAR. This indicates that invasive forbs achieved higher RGR than natives primarily by creating more leaf area per unit leaf mass, not by allocating more biomass to leaf tissue or by having a higher net rate of dry matter production. A high degree of variation in RGR, SLA, and LAR was observed in native forbs, suggesting that the ability to design weed-resistant plant communities may be improved by managing for specific functional traits as opposed to functional groups. 
    • A Batch Preparation Method for Graphite Targets with Low Background for AMS 14C Measurements

      Kitagawa, Hiroyuki; Masazawa, Toshiyuki; Nakamura, Toshio; Matsumoto, Eiji (Department of Geosciences, The University of Arizona, 1993-01-01)
      We have developed a method of graphitization from CO2 samples for accurate 14C measurements by accelerator mass spectrometry. Our batch method, using a sealed Vycor tube, reduces the risk of contamination during graphitization and makes it possible to prepare many samples in a short time (typically 20 samples per day).
    • A Bayesian Approach to the Estimation of Radiocarbon Calibration Curves: The IntCal09 Methodology

      Heaton, T. J.; Blackwell, P. G.; Buck, C. E. (Department of Geosciences, The University of Arizona, 2009-01-01)
      This article presents a new approach to the construction of radiocarbon calibration curves. The Bayesian methodology was developed specifically to facilitate construction of the 2009 updates to the internationally agreed 14C calibration curves known as IntCal09 and Marine09. The curve estimation approach taken uses Markov chain Monte Carlo sampling, specifically a Metropolis-within-Gibbs sampler, which offers improved flexibility and reliability over the approaches used in the past. In particular, the method allows accurate modeling of calibration data with 14C determinations that arise from material deposited over several consecutive calendar years and that exhibit complex uncertainty structures on their calendar date estimates (arising from methods such as wiggle-matching and varve counting).
    • A Bayesian Approach to the Use of 14C Dates in the Estimation of the Age of Peat

      Christen, J. A.; Clymo, R. S.; Litton, C. D. (Department of Geosciences, The University of Arizona, 1995-01-01)
      Peatlands occupy a significant portion of the land surface of the Earth and form a large carbon store. Most peat-forming systems have two layers. The upper layer, the acrotelm, fixes carbon by photosynthesis, loses some of it by decay and passes the remainder on to the lower layer, the catotelm. In the catotelm, decay continues at a slower rate. Mathematical models of the growth of the catotelm have been proposed which relate the cumulative mass of peat above a particular depth to calendar age of the peat at that depth. We demonstrate how 14C dating and the Bayesian approach to data analysis can be used to make inferences about the relation between calendar age and cumulative mass, and to estimate the accumulation and decay rates.
    • A Bayesian Framework for Age Modeling of Radiocarbon-Dated Peat Deposits: Case Studies from the Netherlands

      Blaauw, Maarten; Bakker, Ronald; Christen, J. Andrés; Hall, Valerie A.; van der Plicht, Johannes (Department of Geosciences, The University of Arizona, 2007-01-01)
      Recently, Bayesian statistical software has been developed for age-depth modeling (wiggle-match dating) of sequences of densely spaced radiocarbon dates from peat cores. The method is described in non-statistical terms, and is compared with an alternative method of chronological ordering of 14C dates. Case studies include the dating of the start of agriculture in the northeastern part of the Netherlands, and of a possible Hekla-3 tephra layer in the same country. We discuss future enhancements in Bayesian age modeling.
    • A Bayesian Re-Assessment of the Earliest Radiocarbon Dates from Tiwanaku, Bolivia

      Marsh, Erik J. (Department of Geosciences, The University of Arizona, 2012-08-17)
      The development of sociopolitical complexity at Tiwanaku around AD 500 was one of the major episodes of social change in the history of the Lake Titicaca Basin. It was the result of poorly understood processes that took place at a series of ceremonial centers in the preceding centuries. The history of Tiwanaku during this time is especially unclear, because the only radiocarbon dates are from excavations whose details were never completely published. Despite this, there is consensus that Tiwanaku was founded around 300 BC. A re-evaluation of the archaeological context of each of these dates shows many of them to be unreliable. Two Bayesian models from independent excavations agree that Tiwanaku was in fact founded centuries later, most likely around AD 110 (50–170, 1σ). This has important implications for widely used monolith and ceramic sequences, as well as understanding the rise of Tiwanaku and other archaic states.
    • A Beam Profile Monitor for Rare Isotopes in Accelerator Mass Spectrometry: Preliminary Measurements

      Taccetti, F.; Carraresi, L.; Fedi, M. E.; Manetti, M.; Mariani, P.; Tobia, G.; Mandò, P. A. (Department of Geosciences, The University of Arizona, 2010-01-01)
      In accelerator systems, beam lines are generally equipped with diagnostic elements, such as Faraday cups and beam profile monitors (BPM), to optimize beam transport. These diagnostic elements, or at least commercial ones, are designed to only work with continuous beams, and their typical maximum sensitivity is about few tens of pA. Thus, in the case of diagnosis of rare isotope beams in accelerator mass spectrometry (AMS), Faraday cups and BPMs are not suitable on the high-energy side of the tandem accelerator, after energy-mass-charge analysis. For example, in 14C AMS, even for a modern sample, the expected counting rate is a few tens of Hz; in these conditions, a commercial BPM cannot be used. On the other hand, checking the shape and the position of the rare isotope beam hitting the detector can be important in order to better identify signals in the detector itself, thus also helping in reducing the measurement background. This paper presents a prototype BPM especially designed for low-intensity beams. The BPM is based on a multiwire proportional chamber characterized by 2 grids of anode wires, oriented perpendicular to each other in order to measure both the x and the y coordinates of the particle impact point. Details about the design and the electronics of the device are given, and the first test measurements are discussed.