Title: Association with pedogenic iron and aluminum: effects on soil organic carbon storage and stability in four temperate forest soils

Abstract

Soil organic carbon (SOC) can be stabilized via association with iron (Fe) and aluminum (Al) minerals. Fe and Al can be strong predictors of SOC storage and turnover in soils with relatively high extractable metals content and moderately acidic to circumneutral pH. Here we test whether pedogenic Fe and Al influence SOC content and turnover in soils with low Fe and Al content and acidic pH. In soils from four sites spanning three soil orders, we quantified the amount of Fe and Al in operationally-defined poorly crystalline and organically-complexed phases using selective chemical dissolution applied to the soil fraction containing mineral-associated carbon. We evaluated the correlations of Fe and Al concentrations, mean annual precipitation (MAP), mean annual temperature (MAT), and pH with SOC content and14C-based turnover times. We found that poorly crystalline Fe and Al content predicted SOC turnover times (p < 0.0001) consistent with findings of previous studies, while organically-complexed Fe and Al content was a better predictor of SOC concentration (p < 0.0001). Greater site-level MAP (p < 0.0001) and colder site-level MAT (p < 0.0001) were correlated with longer SOC turnover times but were not correlated with SOC content. Our results suggest that poorly crystalline Fe and Al effectively slow the turnover of SOC inmore » these acidic soils, even when their combined content in the soil is less than 2% by mass. However, in the strongly acidic Spodosol, organo-metal complexes tended to be less stable resulting in a more actively cycling mineral-associated SOC pool.« less

Authors:

Porras, Rachel C. ^[1]; Hicks Pries, Caitlin E. ^[1]; McFarlane, Karis J. ^[2]; Hanson, Paul J. ^[3]; Torn, Margaret S. ^[1]

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+ Show Author Affiliations

1. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Climate and Ecosystem Sciences Division
2. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). Center for Accelerator Mass Spectroscopy
3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Climate Change SCience Inst. and Environmental Sciences Division

Publication Date:

Sat May 13 00:00:00 EDT 2017

Research Org.:

Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States); Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States); Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Biological and Environmental Research (BER)

OSTI Identifier:

1366910

Alternate Identifier(s):

OSTI ID: 1400180; OSTI ID: 1471031

Report Number(s):

LLNL-JRNL-708394
Journal ID: ISSN 0168-2563

Grant/Contract Number:  

AC52-07NA27344; AC05-00OR22725; AC02-05CH11231

Resource Type:

Accepted Manuscript

Journal Name:

Biogeochemistry

Additional Journal Information:

Journal Volume: 133; Journal Issue: 3; Journal ID: ISSN 0168-2563

Publisher:

Springer

Country of Publication:

United States

Language:

English

Subject:

54 ENVIRONMENTAL SCIENCES; 58 GEOSCIENCES; 14C; Soil carbon stabilization; Selective chemical dissolution; Soil fractionation; Soil organic carbon; Mineral-organic associations