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Title: Carbon Sink Strength of Subsurface Horizons in Brazilian Oxisols

Interactions with pedogenic oxides are a known mechanism of soil organic matter (SOM) protection, but little is known about how the protective power of pedogenic oxides varies with soil depth in highly weathered tropical soils. To address this issue, we followed the decomposition of a double-labeled plant litter ( 13C/ 15N) in microcosm experiments using samples collected at four depths (0–10, 10–20, 20–40, and 60–100 cm) from six Brazilian Oxisols. These soils were selected to include a range of taxonomic subtypes, spanning wide variations in mineralogy and texture. After a 12-mo incubation, we quantified the proportion of isotopically-labeled SOM ( 13C/ 15N) within the mineral fraction <53 µm (i.e., clay+silt). We found that litter-C retention increased with depth, while the opposite occurred for litter-N. Correlations between isotopically-labeled SOM and short-range order (SRO) Al-/Fe-(hydr)oxides were insignificant in topsoil (0–10 cm), but increased with depth, reaching peak significance in the 20- to 40-cm interval (r = 0.64 and 0.58, for litter-C and -N, respectively). A similar trend was observed for crystalline Al-/Fe-(hydr)oxides, which were more strongly correlated with the retention of 13C than 15N. We posit that in subsoil, both SRO and crystalline Al-/Fe-(hydr)oxides are more readily involved in the neoformation ofmore » mineral-organic associations. Overall, litter-C is less efficiently transferred into the clay+silt fraction of C-rich topsoil relative to C-depleted subsoil horizons, which may represent a significant C sink for Oxisols.« less
Authors:
 [1] ;  [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [1]
  1. Univ. Federal de Viçosa Viçosa, Minas Gerais (Brazil)
  2. Celulose Nipo-Brasileira, Minas Gerais (Brazil)
  3. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  4. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  5. Oregon State Univ., Corvallis, OR (United States); Institut für Bodenlandschaftsforschung Leibnitz-Zentrum für Agrarlandschaftsforschung (ZALF), Munchenberg (Germany)
Publication Date:
Report Number(s):
LLNL-JRNL-738825
Journal ID: ISSN 0361-5995; 892035
Grant/Contract Number:
AC52-07NA27344; AC02-05CH11231
Type:
Accepted Manuscript
Journal Name:
Soil Science Society of America Journal
Additional Journal Information:
Journal Volume: 82; Journal Issue: 1; Journal ID: ISSN 0361-5995
Publisher:
Alliance of Crop, Soil, and Environmental Science Societies
Research Org:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org:
USDOE National Nuclear Security Administration (NNSA); USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES
OSTI Identifier:
1467802
Alternate Identifier(s):
OSTI ID: 1476589

Souza, Ivan F., Almeida, Luis F. J., Jesus, Guilherme L., Pett-Ridge, Jennifer, Nico, Peter S., Kleber, Markus, and Silva, Ivo R.. Carbon Sink Strength of Subsurface Horizons in Brazilian Oxisols. United States: N. p., Web. doi:10.2136/sssaj2017.05.0143.
Souza, Ivan F., Almeida, Luis F. J., Jesus, Guilherme L., Pett-Ridge, Jennifer, Nico, Peter S., Kleber, Markus, & Silva, Ivo R.. Carbon Sink Strength of Subsurface Horizons in Brazilian Oxisols. United States. doi:10.2136/sssaj2017.05.0143.
Souza, Ivan F., Almeida, Luis F. J., Jesus, Guilherme L., Pett-Ridge, Jennifer, Nico, Peter S., Kleber, Markus, and Silva, Ivo R.. 2018. "Carbon Sink Strength of Subsurface Horizons in Brazilian Oxisols". United States. doi:10.2136/sssaj2017.05.0143. https://www.osti.gov/servlets/purl/1467802.
@article{osti_1467802,
title = {Carbon Sink Strength of Subsurface Horizons in Brazilian Oxisols},
author = {Souza, Ivan F. and Almeida, Luis F. J. and Jesus, Guilherme L. and Pett-Ridge, Jennifer and Nico, Peter S. and Kleber, Markus and Silva, Ivo R.},
abstractNote = {Interactions with pedogenic oxides are a known mechanism of soil organic matter (SOM) protection, but little is known about how the protective power of pedogenic oxides varies with soil depth in highly weathered tropical soils. To address this issue, we followed the decomposition of a double-labeled plant litter (13C/15N) in microcosm experiments using samples collected at four depths (0–10, 10–20, 20–40, and 60–100 cm) from six Brazilian Oxisols. These soils were selected to include a range of taxonomic subtypes, spanning wide variations in mineralogy and texture. After a 12-mo incubation, we quantified the proportion of isotopically-labeled SOM (13C/15N) within the mineral fraction <53 µm (i.e., clay+silt). We found that litter-C retention increased with depth, while the opposite occurred for litter-N. Correlations between isotopically-labeled SOM and short-range order (SRO) Al-/Fe-(hydr)oxides were insignificant in topsoil (0–10 cm), but increased with depth, reaching peak significance in the 20- to 40-cm interval (r = 0.64 and 0.58, for litter-C and -N, respectively). A similar trend was observed for crystalline Al-/Fe-(hydr)oxides, which were more strongly correlated with the retention of 13C than 15N. We posit that in subsoil, both SRO and crystalline Al-/Fe-(hydr)oxides are more readily involved in the neoformation of mineral-organic associations. Overall, litter-C is less efficiently transferred into the clay+silt fraction of C-rich topsoil relative to C-depleted subsoil horizons, which may represent a significant C sink for Oxisols.},
doi = {10.2136/sssaj2017.05.0143},
journal = {Soil Science Society of America Journal},
number = 1,
volume = 82,
place = {United States},
year = {2018},
month = {1}
}