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GLOBAL BIOGEOCHEMICAL CYCLES,
VOL. 16, NO. 4,
1135,
doi:10.1029/2001GB001823,
2002
A multiisotope C and N modeling analysis of soil organic matter turnover and transport as a function of soil depth in a California
annual grassland soil chronosequence
W. T. Baisden
Ecosystem Sciences Division, Department of ESPM,
University of California, Berkeley,
Berkeley,
California,
USA
R. Amundson
Ecosystem Sciences Division, Department of ESPM,
University of California, Berkeley,
Berkeley,
California,
USA
D. L. Brenner
Ecosystem Sciences Division, Department of ESPM,
University of California, Berkeley,
Berkeley,
California,
USA
A. C. Cook
Center for Accelerator Mass Spectrometry,
Lawrence Livermore National Laboratory,
Livermore,
California,
USA
C. Kendall
United States Geological Survey,
Menlo Park,
California,
USA
J. W. Harden
United States Geological Survey,
Menlo Park,
California,
USA
Abstract
We examine soil organic matter (SOM) turnover and transport using C and N isotopes in soil profiles sampled circa 1949, 1978,
and 1998 (a period spanning pulse thermonuclear 14C enrichment of the atmosphere) along a 3-million-year annual grassland soil chronosequence. Temporal differences in soil
Δ14C profiles indicate that inputs of recently living organic matter (OM) occur primarily in the upper 20–30 cm but suggest that
OM inputs can occur below the primary rooting zone. A three-pool SOM model with downward transport captures most observed
variation in Δ14C, percentages of C and N, δ13C, and δ15N, supporting the commonly accepted concept of three distinct SOM pools. The model suggests that the importance of the decadal
SOM pool in N dynamics is greatest in young and old soils. Altered hydrology and possibly low pH and/or P dynamics in highly
developed old soils cause changes in soil C and N turnover and transport of importance for soil biogeochemistry models.
Published 20
December
2002.
Index Terms: 1615 Global Change: Biogeochemical processes (4805); 1694 Global Change: Instruments and techniques; 1803 Hydrology: Anthropogenic effects; 9350 Information Related to Geographic Region: North America.
Read Full Article (file size: 1457749 bytes) Cited by
Citation: Baisden, W. T., R. Amundson, D. L. Brenner, A. C. Cook, C. Kendall, and J. W. Harden
(2002),
A multiisotope C and N modeling analysis of soil organic matter turnover and transport as a function of soil depth in a California
annual grassland soil chronosequence,
Global Biogeochem. Cycles,
16(4),
1135,
doi:10.1029/2001GB001823.
Copyright 2002 by the American Geophysical Union.
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