HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Amundson, R. G. Articles by Lund, L. J. Search for Related Content PubMed Articles by Amundson, R. G. Articles by Lund, L. J. Agricola Articles by Amundson, R. G. Articles by Lund, L. J.

The Stable Isotope Chemistry of a Native and Irrigated Typic Natrargid in the San Joaquin Valley of California¹

ABSTRACT

The stable C and O isotope chemistry of native and irrigated Typic Natrargids was examined in order to determine the relationship between the climate and vegetation and the ¹³C and ¹⁸O of the native pedogenic carbonates (CaCO₃) and the effect of irrigation on the CaCO₃ in the cultivated soils. The native soil had a sparse vegetative cover consisting of grasses and salt tolerant shrubs, especially Atriplex polycarpa (Torr.), S. Wats. The ¹³C of the CaCO₃ reflected the mixture of C3 and C4 vegetation and the ¹⁸O of the CaCO₃ suggested that it had formed from soil H₂O that had undergone extensive amounts of evaporation. At the time of sampling, alfalfa (Medicago sativa L.) was being grown on the irrigated soils. These soils had CO₂ partial pressures of up to 7 KPa, nearly 20 times that of the native soil. The ¹³C of the CaCO₃ in the irrigated soils was not significantly different than that of the native soils which was due, in part, to the relatively small isotopic difference between the newly formed CaCO₃ in the irrigated soil and much of that which occurred naturally. However, the ¹⁸O of CaCO₃ in the irrigated soils appeared to be shifted to more negative values than the ¹⁸O of the native CaCO₃. Based on the differences in the ¹⁸O of the CaCO₃ in the irrigated and native soils, it was semiquantitatively estimated that between 10 to 40% of the carbonate in the irrigated soils was newly formed or had dissolved and reprecipitated as a result of irrigation, increased biological activity, and the application of chemical amendments.

¹ Contribution from the Dep. of Soil and Environmental Sciences, Univ. of California, Riverside, CA 92521, and the Dep. of Plant and Soil Biology, 108 Hilgard Hall, Univ. of California, Berkeley, CA 94720.

² Former Graduate Research Assistant and Professor, Dep. of Soil and Environmental Sciences. Present address of the Senior author is Dep. of Plant and Soil Biology, 108 Hilgard Hall, Univ. of California, Berkeley, CA 94720.

Received for publication August 5, 1986.