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Textural, mineralogical and structural controls on soil organic carbon retention in the Brazilian Cerrados

Zinn, Yuri Lopes
http://rave.ohiolink.edu/etdc/view?acc_num=osu1131381122

Abstract Details

2005, Doctor of Philosophy, Ohio State University, Soil Science.
Soil organic carbon (SOC) retention results from climate, vegetation, drainage and management interactions, but also from texture, mineralogy and structure. In order to assess the controls that these three soil properties exert on SOC levels in the Brazilian Cerrado region, three native soils under similar climate and slope but of contrasting texture were sampled in triplicate to 1m depth. Soils were characterized by physical, chemical, mineralogical, wet sieving, and microscopic analyses, and SOC concentration was determined in bulk soils, particle size separates (clay, silt, sand) and water-stable aggregates (WSA). The basic assumption was that SOC particle size determines its retention mechanism: colloidal forms are sorbed to clays, and particulate organic matter (POM, >20ìm) occurs outside (free-POM) or inside aggregates (occluded-POM). These mechanisms are affected by soil texture, mineralogy and structure, which then control SOC retention. The three soils were classified as kaolinitic clayey, loamy and sandy Haplustox. Soil texture and depth strongly affected SOC concentrations, which were modeled (R2=0.92, n=126) based on clay+silt and depth. Soil specific surface area (SSA) was modeled as a function of clay, silt and SOC contents, but not depth. Thus, SOC increased with higher SSA and clay; but in a single soil profile SSA decreased in topsoil because of SOC-enhanced aggregation. SOC concentration in size separates was inversely related to the amount of that size fraction in soil (SOC dilution effect), but the clay-sized SOC pool could be modeled as a function of clay contents and depth. The bulk SOC and clay-sized SOC pool were better correlated with Fe-oxides in topsoil and amorphous Al oxides in the subsoil. Soil structure, as indicated by mean weight diameter (MWD) and percent of WSA>2 mm, was strongly correlated with clay+silt contents, but bulk SOC was poorly correlated structure, except for the 0-5 cm depth. Occluded-POM was strongly affected by soil texture, varying from ca. 25% of total POM in the sandy Haplustox, to ca. 50% in the clayey Haplustox. Because texture affects contents of Fe-Al oxides and POM occlusion, SOC retention in Cerrado soils is controlled, in decreasing order, by: 1) texture, 2) mineralogy, and 3) structure.
Rattan Lal (Advisor)
183 p.
Soil Organic Carbon; Texture; Mineralogy; Structure; Fauna; Brazil; Cerrado

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Citations

  • Zinn, Y. L. (2005). Textural, mineralogical and structural controls on soil organic carbon retention in the Brazilian Cerrados [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1131381122

    APA Style (7th edition)

  • Zinn, Yuri. Textural, mineralogical and structural controls on soil organic carbon retention in the Brazilian Cerrados. 2005. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1131381122.

    MLA Style (8th edition)

  • Zinn, Yuri. "Textural, mineralogical and structural controls on soil organic carbon retention in the Brazilian Cerrados." Doctoral dissertation, Ohio State University, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=osu1131381122

    Chicago Manual of Style (17th edition)

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This open access ETD is published by The Ohio State University and OhioLINK.