American Geophysical Union Become an AGU Member
Subscribe to AGU Journals		 AGU Home AGU Publications

Read Full Article (file size: 1457749 bytes)    Cited by

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.