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Carbon Isotope Dynamics in Some Tropical Soils

Published online by Cambridge University Press:  18 July 2016

Peter Becker-Heidmann  and
H-W Scharpenseel
Peter Becker-Heidmann
Affiliation:
Institut für Bodenkunde, Universität Hamburg Federal Republic of Germany
H-W Scharpenseel
Affiliation:
Institut für Bodenkunde, Universität Hamburg Federal Republic of Germany
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Abstract

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We determined δ13C and D14C in some agricultural soil profiles of the tropics: Ustalf from the semi-arid tropics (India), a Udult, an Aquoll and an Aquept from the humid tropics (Philippines). We used a thin-layer sampling, resulting in high-resolution depth-distribution patterns of natural 13C and 14C content of organic carbon. Regular plowing or puddling leads to uniform isotope concentrations in the topsoil. Decomposition of organic matter raises the δ13C value, and vertical translocation raises the δ13C value with depth. The change of cultivation from pulses (C3-type metabolism of photosynthesis) to sorghum (C4) results in a decrease of δ13C with depth in the topsoil. Where the clay content in the subsoil is high, δ13C remains constant, due to fixation of organic carbon to clay minerals, and D14C decreases with depth. Below the clay-enriched zone, δ13C declines and D14C rises again, due to a chromatographic-like effect. At some horizon boundaries, inhomogeneities in texture delay percolation locally, thus preventing sorption and causing peak values of D14C.

Type
II. Carbon Cycle in the Environment
Information
Radiocarbon , Volume 31 , Issue 3: June 20-25, 1988 Dubrovnik, Yugoslavia , 1989 , pp. 672 - 679
Copyright
Copyright © The American Journal of Science 

References

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