Title: Differences in soluble organic carbon chemistry in pore waters sampled from different pore size domains

Abstract

Spatial isolation of soil organic carbon (SOC) in different sized pores may be a mechanism by which otherwise labile carbon (C) could be protected in soils. When soil water content increases, the hydrologic connectivity of soil pores also increases, allowing greater transport of SOC and other resources from protected locations, to microbially colonized locations more favorable to decomposition. The heterogeneous distribution of specialized decomposers, C, and other resources throughout the soil indicates that the metabolism or persistence of soil C compounds is highly dependent on short-distance transport processes. The objective of this research was to characterize the complexity of C in pore waters held at weak and strong water tensions (effectively soil solution held behind coarse- and fine-pore throats, respectively) and evaluate the microbial decomposability of these pore waters. We saturated intact soil cores and extracted pore waters with increasing suction pressures to sequentially sample pore waters from increasingly fine pore domains. Ultrahigh resolution mass spectrometry of the SOC was used to profile the major biochemical classes (i.e., lipids, proteins, lignin, carbohydrates, and condensed aromatics) of compounds present in the pore waters; some of these samples were then used as substrates for growth of Cellvibrio japonicus (DSMZ 16018), Streptomyces cellulosaemore » (ATCC® 25439™), and Trichoderma reseei (QM6a) in 7 day incubations. The soluble C in finer pores was more complex than the soluble C in coarser pores, and the incubations revealed that the more complex C in these fine pores is not recalcitrant. The decomposition of this complex C led to greater losses of C through respiration than the simpler C from coarser pore waters. Our research suggests that soils that experience repeated cycles of drying and wetting may result in patterns of CO2 fluxes that are driven by i) the transport of C from protected pools into active, ii) the chemical quality of the potentially soluble C, and iii) the type of microorganisms most likely to metabolize this C.« less

Authors:

Bailey, V. L. ;

• Search DOE PAGES for author "Bailey, V. L."
• Search DOE PAGES for ORCID "0000-0002-2248-8890"

Smith, A. P.; Tfaily, M.; Fansler, S. J.; Bond-Lamberty, B.

• Search DOE PAGES for author "Bond-Lamberty, B."
• Search DOE PAGES for ORCID "0000-0001-9525-4633"

Publication Date:

Sat Apr 01 00:00:00 EDT 2017

Research Org.:

Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)

Sponsoring Org.:

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

Contributing Org.:

PNNL-Univ. of Maryland Joint Global Climate Change Research Inst., College Park, MD (United States)

OSTI Identifier:

1390383

Alternate Identifier(s):

OSTI ID: 1342226; OSTI ID: 1353307

Report Number(s):

PNNL-SA-118268
Journal ID: ISSN 0038-0717; S0038071716306447; PII: S0038071716306447

Grant/Contract Number:  

AC05-76RL01830

Resource Type:

Published Article

Journal Name:

Soil Biology and Biochemistry

Additional Journal Information:

Journal Name: Soil Biology and Biochemistry Journal Volume: 107 Journal Issue: C; Journal ID: ISSN 0038-0717

Publisher:

Elsevier

Country of Publication:

United Kingdom

Language:

English

Subject:

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Pore water; Carbon protection; Soil organic carbon; Soil structure; Decomposability; Environmental Molecular Sciences Laboratory