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Production of n-alkyl lipids in living plants and implications for the geologic past

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dc.contributor.author Diefendorf, Aaron F. en
dc.contributor.author Freeman, Katherine H. en
dc.contributor.author Wing, Scott L. en
dc.contributor.author Graham, Heather V. en
dc.date.accessioned 2011-12-20T14:37:34Z
dc.date.available 2011-12-20T14:37:34Z
dc.date.issued 2011
dc.identifier.citation Diefendorf, Aaron F., Freeman, Katherine H., Wing, Scott L., and Graham, Heather V. 2011. "<a href="https://repository.si.edu/handle/10088/17510">Production of n-alkyl lipids in living plants and implications for the geologic past</a>." <em>Geochimica et Cosmochimica Acta</em>. 75 (23):7472&ndash;7485. <a href="https://doi.org/10.1016/j.gca.2011.09.028">https://doi.org/10.1016/j.gca.2011.09.028</a> en
dc.identifier.issn 0016-7037
dc.identifier.uri http://hdl.handle.net/10088/17510
dc.description.abstract Leaf waxes (i.e. n-alkyl lipids or n-alkanes) are land-plant biomarkers widely used to reconstruct changes in climate and the carbon isotopic composition of the atmosphere. There is little information available, however, on how the production of leaf waxes by different kinds of plants might influence the abundance and isotopic composition of n-alkanes in sedimentary archives. This lack of information increases uncertainty in interpreting n-alkyl lipid abundance and 13C signals in ancient settings. We provide here n-alkyl abundance distributions and carbon isotope fractionation data for deciduous and evergreen angiosperm and gymnosperm leaves from 46 tree species, representing 24 families. n-Alkane abundances are significantly higher in angiosperms than gymnosperms; many of the gymnosperm species investigated did not produce any n-alkanes. On average, deciduous angiosperms produce 200 times more n-alkanes than deciduous gymnosperms. Although differences between angiosperms and gymnosperms dominate the variance in n-alkane abundance, leaf life-span is also important, with higher n-alkane abundances in longer-lived leaves. n-Alkanol abundances covary with n-alkanes, but n-alkanoic acids have similar abundances across all plant groups. Isotopic fractionation between leaf tissue and individual alkanes (εlipid) varies by as much as 10‰ among different chain lengths. Overall, εlipid values are slightly larger (-4.5‰) for angiosperm than for gymnosperm (-2.5‰) n-alkanes. Angiosperms commonly express slightly higher Î"leaf (photosynthetic discrimination) relative to gymnosperms under similar growth conditions. As a result, angiosperm n-alkanes are expected to be generally 3 to 5‰ more depleted in 13C relative to gymnosperm alkanes for the same locality. Differences in n-alkane production indicate the biomarker record will largely (but not exclusively) reflect angiosperms if both groups were present, and also that evergreen plants will likely be overrepresented compared with deciduous ones. We apply our modern lipid abundance patterns and εlipid results to constrain the magnitude of the carbon isotope excursion (CIE) at the onset of the Paleocene-Eocene Thermal Maximum (55.8 Ma). When Bighorn Basin (WY) sediment n-alkanes are interpreted in context of floral changes and modern n-alkane production estimates for angiosperms and gymnosperms, the CIE is greater in magnitude (-5.6‰) by ∼1‰ compared to previous estimates that do not take into account n-alkane production. en
dc.relation.ispartof Geochimica et Cosmochimica Acta en
dc.title Production of n-alkyl lipids in living plants and implications for the geologic past en
dc.type Journal Article en
dc.identifier.srbnumber 108156
dc.identifier.doi 10.1016/j.gca.2011.09.028
rft.jtitle Geochimica et Cosmochimica Acta
rft.volume 75
rft.issue 23
rft.spage 7472
rft.epage 7485
dc.description.SIUnit NH-Paleobiology en
dc.description.SIUnit NMNH en
dc.citation.spage 7472
dc.citation.epage 7485

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