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 Biogeochemical Cycles
By: , and 

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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.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title 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
Series title Global Biogeochemical Cycles
DOI 10.1029/2001GB001823
Volume 16
Issue 4
Year Published 2002
Language English
Publisher AGU
Contributing office(s) California Water Science Center
Description 26 p.
First page 82-1
Last page 82-26