CARBON’S KEEPERS: THE NATURE AND ROLE OF AGGREGATES AND MICROBIAL COMMUNTIES IN A DEEP FERRIHYDRITIC ANDISOL

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dc.contributor.advisorNguyen, Nhu H.
dc.contributor.authorFullmer, Christian
dc.contributor.departmentTropical Plant and Soil Sciences
dc.date.accessioned2024-07-02T23:41:14Z
dc.date.issued2024
dc.description.degreeM.S.
dc.embargo.liftdate2026-06-24
dc.identifier.urihttps://hdl.handle.net/10125/108320
dc.subjectSoil sciences
dc.subjectMicrobiology
dc.titleCARBON’S KEEPERS: THE NATURE AND ROLE OF AGGREGATES AND MICROBIAL COMMUNTIES IN A DEEP FERRIHYDRITIC ANDISOL
dc.typeThesis
dcterms.abstractOver half of global terrestrial soil organic carbon is found in soils below 30 cm and carbon dynamics change with depth, but the mechanisms that determine the changing dynamics of soil carbon across depth are poorly understood. Microbes are responsible for the turnover of carbon from soil to the atmosphere and aggregates are known to slow this turnover. However, aggregates and their related microbial communities are seldom studied at depth, especially in volcanic-ash soils, or Andisols. These soils, rich in poorly and non-crystalline minerals (PNCM), can contain exceptional amounts of organic matter (holding 5% of earth's soil organic matter). As such, developing a greater understanding of the factors controlling carbon dynamics in these soils is important to conserve soil organic matter as greenhouse gasses accumulate in the atmosphere. In this study, I sampled a ferrihydritic Andisol across a depth gradient, and performed physicochemical and biological measurements across an aggregate size gradient to characterize the factors that contribute to aggregate and carbon stability. I showed that ferrihydritic Andisols contain strong aggregates across every depth, but that the predominant binding agent in these strongest aggregates changes from organic matter in the topsoil to minerals in the subsoils. I propose that this is at least in part due to PNCM and organo-metal complexes acting as aggregate binding agents, leading to the enhanced physical occlusion of organic matter in subsoils. As a result, the strongest aggregates in the topsoil are more susceptible to oxidation and turnover than aggregates in the deep soil. In addition, microbial diversity does not increase with increasing specific surface area of smaller aggregates, bringing into question the current hypothesis that surface area contributes to microbial diversity. I discussed these findings in the context of the mechanistic understanding of aggregate theory in soils, and more specifically, Andisols. The mechanisms whereby poorly and non-crystalline minerals increase the persistence of carbon adds to the conceptual advances needed to improve our understanding of the mechanisms of carbon dynamics.
dcterms.extent139 pages
dcterms.languageen
dcterms.publisherUniversity of Hawai'i at Manoa
dcterms.rightsAll UHM dissertations and theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission from the copyright owner.
dcterms.typeText
local.identifier.alturihttp://dissertations.umi.com/hawii:12115

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