• 14C Dating and Soil Organic Matter Dynamics in Arctic and Subarctic Ecosystems

      Cherkinsky, A. E. (Department of Geosciences, The University of Arizona, 1996-01-01)
      The carbon content, pH and 14C concentration of humic acids were determined for three soil series of Arctic and Subarctic ecosystems. The measured 14C ages were interpreted in the light of an equilibrium model of humus formation and of mineralization processes in recent soils, and the coefficient of renovation, Kr, was calculated for humic acids. The comparison of Kr for series formed under different climatic conditions suggested that global warming could accelerate decomposition of soil organic matter and possibly increase productivity of ecosystems of the Arctic region.
    • 14C Dating of an Israelite Biblical Site at Kuntillet Ajrud (Horvat Teman): Correction, Extension and Improved Age Estimate

      Carmi, Israel; Segal, Dror (Department of Geosciences, The University of Arizona, 1996-01-01)
    • 14C Laboratories

      Department of Geosciences, The University of Arizona, 1996-01-01
    • 14C Measurements of Soil Organic Matter, Soil CO2 and Dissolved Organic Carbon (1987-1992)

      Tegen, Ina; Dörr, Helmut (Department of Geosciences, The University of Arizona, 1996-01-01)
      For several undisturbed sites in Germany, 14C data are reported for soil organic matter (SOM) (4 sites), soil CO2 (10 sites) and dissolved organic carbon (DOC) (1 site). With the assumption of a fast degradable component (lifetime ca. 1 yr) and a slow degradable component (lifetime ca. 100 yr), a range between 0.6 and 1.6 mm yr-1 has been determined for the downward migration rates of soil organic carbon at the sampling sites from the soil 14C data. The soil CO2 measurements show that in deciduous forests the fast degradable component is ca. 60% and the slow degradable component is ca. 40% of the SOM. In coniferous forests this ratio is reversed. The 14C results for DOC could not be explained with the assumption of a first-order decay process. The removal of soil organic carbon by DOC is of minor importance for the estimation of carbon budgets for the investigated site.
    • 16th International Radiocarbon Conference

      Department of Geosciences, The University of Arizona, 1996-01-01
    • 1996 Price List

      Department of Geosciences, The University of Arizona, 1996-01-01
    • 1997 Price List

      Department of Geosciences, The University of Arizona, 1996-01-01
    • 1997 Price List

      Department of Geosciences, The University of Arizona, 1996-01-01
    • 3rd International Symposium

      Department of Geosciences, The University of Arizona, 1996-01-01
    • Abstracts of the 7th International AMS Conference

      Department of Geosciences, The University of Arizona, 1996-01-01
    • Acknowledgments

      Department of Geosciences, The University of Arizona, 1996-01-01
    • An Archaeological and Paleontological Chronology for Daisy Cave (CA-SMI-261), San Miguel Island, California

      Erlandson, Jon M.; Kennett, Douglas J.; Ingram, B. Lynn; Guthrie, Daniel A.; Morris, Don P.; Tveskov, Mark A.; West, G. James; Walker, Phillip L. (Department of Geosciences, The University of Arizona, 1996-01-01)
      We provide detailed contextual information on 25 14C dates for unusually well-preserved archaeological and paleontological remains from Daisy Cave. Paleontological materials, including faunal and floral remains, have been recovered from deposits spanning roughly the past 16,000 yr, while archaeological materials date back to ca. 10,500 BP. Multidisciplinary investigations at the site provide a detailed record of environmental and cultural changes on San Miguel Island during this time period. This record includes evidence for the local or regional extinction of a number of animal species, as well as some of the earliest evidence for the human use of boats and other maritime activities in the Americas. Data from Daisy Cave contribute to a growing body of evidence that Paleoindians had adapted to a wide variety of New World environments prior to 10,000 BP. Analysis of shell-charcoal pairs, along with isotopic analysis of associated marine shells, supports the general validity of marine shell dating, but also provides evidence for temporal fluctuations in the reservoir effect within the Santa Barbara Channel region.
    • Associate Editors

      Department of Geosciences, The University of Arizona, 1996-01-01
    • Associate Editors

      Department of Geosciences, The University of Arizona, 1996-01-01
    • Athol Rafter, 1913-1996

      Sparks, Rodger (Department of Geosciences, The University of Arizona, 1996-01-01)
    • Author Index Volume 38, Nos. 2 and 3, 1996

      Department of Geosciences, The University of Arizona, 1996-01-01
    • Book Review: Learning from Things: Method and Theory of Material Culture Studies, W. David Kingery (Ed.)

      Skibo, James M. (Department of Geosciences, The University of Arizona, 1996-01-01)
    • Comparison of Fractionation Methods for Soil Organic Matter 14C Analysis

      Trumbore, Susan E.; Zheng, Shuhui (Department of Geosciences, The University of Arizona, 1996-01-01)
      14C measurements provide a useful test for determining the degree to which chemical and physical fractionation of soil organic matter (SOM) are successful in separating labile and refractory organic matter components. Results from AMS measurements of fractionated SOM made as part of several projects are summarized here, together with suggestions for standardization of fractionation procedures. Although no single fractionation method will unequivocally separate SOM into components cycling on annual, decadal and millennial time scales, a combination of physical (density separation or sieving) and chemical separation methods (combined acid and base hydrolysis) provides useful constraints for models of soil carbon dynamics in several soil types.
    • Estimation of Slow- and Fast-Cycling Soil Organic Carbon Pools from 6N HCl Hydrolysis

      Leavitt, S. W.; Follett, R. F.; Paul, E. A. (Department of Geosciences, The University of Arizona, 1996-01-01)
      Acid hydrolysis is used to fractionate the soil organic carbon pool into relatively slowand fast-cycling compartments on soils from Arizona, the Great Plains states and Michigan collected for carbon isotope tracer studies related to soil carbon sequestration, for studies of shifts in C3/C4 vegetation, and for "pre-bomb" soil-carbon inventories. Prior to hydrolysis, soil samples are first treated with cold 0.5-1N HCl to remove soil carbonates if necessary. Samples are then dispersed in a concentrated NaCI solution (p is roughly equal to 1.2 g cm-3) and floated plant fragments are skimmed off the surface. After rinsing and drying, all remaining recognizable plant fragments are picked from the soil under 20x magnification. Plant-free soils, and hot, 6N HCl acid-hydrolysis residue and hydrolyzate fractions are analyzed for carbon content, delta-13C and 14C age, and the carbon distribution is verified within 1-2% by stable-carbon isotope mass balance. On average, the recalcitrant residue fraction is 1800 yr older and 2.6 per mil more 13C-depleted than total soil organic carbon. A test of hydrolysis with fresh plant fragments produced as much as 71-76% in the acid-hydrolysis residue pool. Thus, if plant fragments are not largely removed prior to hydrolysis, the residue fraction may date much younger than it actually is.
    • From the Editor

      Long, Austin (Department of Geosciences, The University of Arizona, 1996-01-01)