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Variation in soil organic carbon across lowland tropical forest gradients: soil fertility and precipitation effects on soil carbon organic chemistry and age

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dc.contributor.authorBlackaby, Emily, author
dc.contributor.authorCusack, Daniela F., advisor
dc.contributor.authorBoot, Claudia M., committee member
dc.contributor.authorCotrufo, M. Francesca, committee member
dc.date.accessioned2023-01-21T01:24:21Z
dc.date.available2023-01-21T01:24:21Z
dc.date.issued2022
dc.description.abstractTropical forests hold large amounts of carbon (C) in both aboveground biomass and belowground soil organic carbon (SOC) stocks. Climate change is expected to alter tropical forests' precipitation with some forests already showing decreased rainfall. We analyzed SOC molecular composition and age in lowland tropical forests of Panama across fertility gradients, rainfall ranges, and soil order. We hypothesized that H1) rainforests with relatively greater rainfall store larger amounts of proteins (N-alkyl) and lipids (alkyl) in SOC because of greater microbial biomass and H2) subsurface SOC stocks in more strongly weathered, clay-rich soils are older (as indicated by radiocarbon) because of great sorption capacity. We found that overall, carbon decreased and became older with depth across all samples. Solid-state 13C NMR spectroscopy indicated that soil order and depth were significant predictors of C functional group abundances while phosphorus (P) was a significant predictor of alkyl, aromatic, and carboxyl C. Alkyl/O-Alkyl ratios increased with depth indicating increased degradation of the SOC. ∆14C values indicated older C with depth and varied significantly with soil order where Oxisols were the oldest and Mollisols the youngest. Soil N % and K % were significant predictors of younger soil C. Additionally, biomolecular composition of SOM from 0-10 cm was a significant predictor of ∆14C at 25-50 cm. We found that higher abundances of alkyl and O-alkyl C corresponded with younger C at depth and higher abundances of aromatic and phenolic C contained older C at depth.
dc.format.mediumborn digital
dc.format.mediummasters theses
dc.identifierBlackaby_colostate_0053N_17564.pdf
dc.identifier.urihttps://hdl.handle.net/10217/235983
dc.languageEnglish
dc.language.isoeng
dc.publisherColorado State University. Libraries
dc.relation.ispartof2020-
dc.rightsCopyright and other restrictions may apply. User is responsible for compliance with all applicable laws. For information about copyright law, please see https://libguides.colostate.edu/copyright.
dc.subjecttadiocarbon 14C
dc.subjecttropical forests
dc.subjectsoil organic carbon
dc.subject13C NMR
dc.titleVariation in soil organic carbon across lowland tropical forest gradients: soil fertility and precipitation effects on soil carbon organic chemistry and age
dc.typeText
dc.typeImage
dcterms.rights.dplaThis Item is protected by copyright and/or related rights (https://rightsstatements.org/vocab/InC/1.0/). You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s).
thesis.degree.disciplineEcosystem Science and Sustainability
thesis.degree.grantorColorado State University
thesis.degree.levelMasters
thesis.degree.nameMaster of Science (M.S.)

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