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dc.contributor.advisorCole, Julia Een_US
dc.contributor.authorBrooks-English, Nathanael Talman
dc.creatorBrooks-English, Nathanael Talmanen_US
dc.date.accessioned2011-12-06T13:45:27Z
dc.date.available2011-12-06T13:45:27Z
dc.date.issued2008en_US
dc.identifier.urihttp://hdl.handle.net/10150/195268
dc.description.abstractThere are relatively few annually resolved climate proxies in arid and semi-arid regions. Columnar cactuses are common in these regions and the stable isotopes of carbon and oxygen in durable spines record variations in rainfall, humidity and ecophysiology as they grow in series along the sides of cactuses. Despite their spines, columnar cactuses provide important ecosystem resources and services in drought prone areas, however, the impact that long-term climate variability and infrequent storms (El Niño or tropical storms) have on the ecology and ecophysiology of columnar cactus is less clear. Stable isotopes in trees and corals serve as useful proxies of climate and ecophysiological information, but for cactus we lack the most rudimentary information about the isotopic systems and their links to the environment. Here, we present an isotopic framework that begins with developing semi-empirical mechanistic models of δ¹³C, δ¹⁸O and δ²H variation in saguaro cactuses that link physical and physiological fractionation factors in stem water and spines to rainfall and humidity. We also review a novel method for determining the age of spines, an important step in developing useful chronologies of isotopic variation in spines. The mechanistic models combined with local climate records enhance our understanding of isotopic variation in daily and annually dated spine δ¹³C and δ¹⁸O records and explain the statistical association of δ¹³C and δ¹⁸O in spines with rainfall, vapor pressure deficit, and El Niño enhanced winter rains. While there are still some challenges to overcome, we expect that isotopic spine series will be used as climate proxies to answer questions regarding regional climate variability or to enhance current models of past and future climates. Likewise, ecophysiologists can use the isotopic spine series in conjunction with gas exchange or carbohydrate studies to look at reproductive or biological responses to changing environments.
dc.language.isoENen_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.subjectCactusen_US
dc.subjectCarbonen_US
dc.subjectClimateen_US
dc.subjectColumnaren_US
dc.subjectIsotopesen_US
dc.subjectOxygenen_US
dc.titleStable Isotopes in the Spines of Columnar Cactus: a New Proxy for Climate and Ecophysiological Researchen_US
dc.typetexten_US
dc.typeElectronic Dissertationen_US
dc.identifier.oclc752259914en_US
thesis.degree.grantorUniversity of Arizonaen_US
thesis.degree.leveldoctoralen_US
dc.contributor.committeememberDettman, David Len_US
dc.contributor.committeememberWilliams, David Gen_US
dc.contributor.committeememberLeavitt, Stevenen_US
dc.contributor.committeememberOverpeck, Jonathan Ten_US
dc.identifier.proquest10093en_US
thesis.degree.disciplineGeosciencesen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.namePh.D.en_US
refterms.dateFOA2018-08-14T23:57:00Z
html.description.abstractThere are relatively few annually resolved climate proxies in arid and semi-arid regions. Columnar cactuses are common in these regions and the stable isotopes of carbon and oxygen in durable spines record variations in rainfall, humidity and ecophysiology as they grow in series along the sides of cactuses. Despite their spines, columnar cactuses provide important ecosystem resources and services in drought prone areas, however, the impact that long-term climate variability and infrequent storms (El Niño or tropical storms) have on the ecology and ecophysiology of columnar cactus is less clear. Stable isotopes in trees and corals serve as useful proxies of climate and ecophysiological information, but for cactus we lack the most rudimentary information about the isotopic systems and their links to the environment. Here, we present an isotopic framework that begins with developing semi-empirical mechanistic models of δ¹³C, δ¹⁸O and δ²H variation in saguaro cactuses that link physical and physiological fractionation factors in stem water and spines to rainfall and humidity. We also review a novel method for determining the age of spines, an important step in developing useful chronologies of isotopic variation in spines. The mechanistic models combined with local climate records enhance our understanding of isotopic variation in daily and annually dated spine δ¹³C and δ¹⁸O records and explain the statistical association of δ¹³C and δ¹⁸O in spines with rainfall, vapor pressure deficit, and El Niño enhanced winter rains. While there are still some challenges to overcome, we expect that isotopic spine series will be used as climate proxies to answer questions regarding regional climate variability or to enhance current models of past and future climates. Likewise, ecophysiologists can use the isotopic spine series in conjunction with gas exchange or carbohydrate studies to look at reproductive or biological responses to changing environments.


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