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

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 be accompanied by repeated cycles of increased CO 2 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:
ORCiD logo [1] ;  [1] ;  [2] ;  [1] ; ORCiD logo [3]
  1. Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Biological Sciences Division
  2. Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Environmental and Molecular Sciences Lab.
  3. PNNL-Univ. of Maryland Joint Global Climate Change Research Inst., College Park, MD (United States)
Publication Date:
Report Number(s):
PNNL-SA-118268
Journal ID: ISSN 0038-0717; PII: S0038071716306447
Grant/Contract Number:
AC05-76RL01830
Type:
Published Article
Journal Name:
Soil Biology and Biochemistry
Additional Journal Information:
Journal Volume: 107; Journal ID: ISSN 0038-0717
Publisher:
Elsevier
Research Org:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
Contributing Orgs:
PNNL-Univ. of Maryland Joint Global Climate Change Research Inst., College Park, MD (United States)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Pore water; Carbon protection; Soil organic carbon; Soil structure; Decomposability; Environmental Molecular Sciences Laboratory
OSTI Identifier:
1390383
Alternate Identifier(s):
OSTI ID: 1342226; OSTI ID: 1353307