Exploring seasonal climate variability in East African trees: High-resolution oxygen and carbon isotope records of cellulose of Vitex payos from Chyulu Hills, Kenya
Unrestricted A nearly continuous, annually resolved record of cellulosic δ¹⁸O and δ¹³C is presented for the East African tree Vitex payos for the recent through the late 19th century. The isotope data of individual rings is cross-calibrated against atmospheric variables during the late 20th century...
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Language: | English |
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University of Southern California Digital Library (USC.DL)
2015
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Online Access: | https://dx.doi.org/10.25549/usctheses-m3630 https://digitallibrary.usc.edu/asset-management/2A3BF1FPNPNP |
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ftdatacite:10.25549/usctheses-m3630 |
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record_format |
openpolar |
institution |
Open Polar |
collection |
DataCite Metadata Store (German National Library of Science and Technology) |
op_collection_id |
ftdatacite |
language |
English |
topic |
Geological Sciences isotope dendroclimatology paleoclimatology dendrochronology isotope geochemistry Vitex payos |
spellingShingle |
Geological Sciences isotope dendroclimatology paleoclimatology dendrochronology isotope geochemistry Vitex payos Horan, Patrick Devin Exploring seasonal climate variability in East African trees: High-resolution oxygen and carbon isotope records of cellulose of Vitex payos from Chyulu Hills, Kenya |
topic_facet |
Geological Sciences isotope dendroclimatology paleoclimatology dendrochronology isotope geochemistry Vitex payos |
description |
Unrestricted A nearly continuous, annually resolved record of cellulosic δ¹⁸O and δ¹³C is presented for the East African tree Vitex payos for the recent through the late 19th century. The isotope data of individual rings is cross-calibrated against atmospheric variables during the late 20th century to ascertain how and when during the year cellulose obtains its δ¹⁸O and δ¹³C value in response to environmental conditions at the tree site. During the late 20th century the δ¹⁸O and δ¹³C obtained from alpha cellulose from annual rings of V. payos correlates strongly with precipitation amount and with relative humidity, with depleted (enriched) δ¹⁸O and depleted (enriched) δ¹³C values associated with increased (reduced) precipitation and relative humidity. The strongest correlations are found between cellulose δ¹⁸O and the amount of precipitation and the relative humidity during December-February, although temperature contributes to the observed isotopic variance as well. Relative humidity in December-February appears to have the strongest correlation to annual cellulosic δ¹³C values. The results of this cross-correlation study are used to develop a preliminary seasonal growth model for V. payos that reflects variations in precipitation amount and relative humidity during the December-February growing season.; During the late 20th century the East Africa continent and the western Indian Ocean basin experienced anomalously wet conditions in summer (December-February) when sea surface temperatures (SSTs) were anomalously warm in the western Indian Ocean and zonal winds were anomalously strong in association with positive phases of the Indian Ocean Dipole (IOD) and/or El Nino Southern Oscillation (ENSO). Using the correlation between cellulosic isotopic values and hydroclimate variability over East Africa and Indian Ocean SSTs during the late 20th century a preliminary climate reconstruction is proposed for the pre-20th century from V. payos δ¹⁸O and δ¹³C. The isotopic record of V. payos indicates the late 19th century was anomalously wet over East Africa when compared to the late 20th century, consistent with lake level changes and ice core isotopic data. Climate model simulations indicate the wetter pre-20th century climate was a response to enhanced warming in the western Indian Ocean basin, generating a low pressure center and easterly surface winds that brought moisture to East Africa. The annually resolved isotopic data from V. payos suggest much of the observed and modeled hydroclimate variability at multidecadal to century scales is a response to SST anomalies in the western Indian Ocean.; The results of the present study should help guide future phenological studies of V. payos and other Vitex species in equatorial East Africa. Importantly, stable isotope data obtained from individual growth rings suggests that the annual production of cellulose in V. payos occurs during a short seasonal period from January to February, information that could not be inferred directly from tree ring width data alone. Further improvements in sampling tree rings at intra-annual resolution and in-situ monitoring of weather/climate variables, including isotopic variability of moisture would be necessary in order to fully utilize cellulosic δ¹⁸O as a climate proxy, with the potential for becoming a continent-wide hydrologic monitoring network, the first of its kind from Africa. The isotopic database for V. payos is among the few available terrestrial climate records provides estimates of how hydrologic budgets varied over East Africa during the past several centuries. |
format |
Dataset |
author |
Horan, Patrick Devin |
author_facet |
Horan, Patrick Devin |
author_sort |
Horan, Patrick Devin |
title |
Exploring seasonal climate variability in East African trees: High-resolution oxygen and carbon isotope records of cellulose of Vitex payos from Chyulu Hills, Kenya |
title_short |
Exploring seasonal climate variability in East African trees: High-resolution oxygen and carbon isotope records of cellulose of Vitex payos from Chyulu Hills, Kenya |
title_full |
Exploring seasonal climate variability in East African trees: High-resolution oxygen and carbon isotope records of cellulose of Vitex payos from Chyulu Hills, Kenya |
title_fullStr |
Exploring seasonal climate variability in East African trees: High-resolution oxygen and carbon isotope records of cellulose of Vitex payos from Chyulu Hills, Kenya |
title_full_unstemmed |
Exploring seasonal climate variability in East African trees: High-resolution oxygen and carbon isotope records of cellulose of Vitex payos from Chyulu Hills, Kenya |
title_sort |
exploring seasonal climate variability in east african trees: high-resolution oxygen and carbon isotope records of cellulose of vitex payos from chyulu hills, kenya |
publisher |
University of Southern California Digital Library (USC.DL) |
publishDate |
2015 |
url |
https://dx.doi.org/10.25549/usctheses-m3630 https://digitallibrary.usc.edu/asset-management/2A3BF1FPNPNP |
geographic |
Indian |
geographic_facet |
Indian |
genre |
ice core |
genre_facet |
ice core |
op_doi |
https://doi.org/10.25549/usctheses-m3630 |
_version_ |
1766029844033830912 |
spelling |
ftdatacite:10.25549/usctheses-m3630 2023-05-15T16:39:30+02:00 Exploring seasonal climate variability in East African trees: High-resolution oxygen and carbon isotope records of cellulose of Vitex payos from Chyulu Hills, Kenya Horan, Patrick Devin 2015 https://dx.doi.org/10.25549/usctheses-m3630 https://digitallibrary.usc.edu/asset-management/2A3BF1FPNPNP en eng University of Southern California Digital Library (USC.DL) Geological Sciences isotope dendroclimatology paleoclimatology dendrochronology isotope geochemistry Vitex payos Dataset dataset 2015 ftdatacite https://doi.org/10.25549/usctheses-m3630 2022-02-09T12:42:57Z Unrestricted A nearly continuous, annually resolved record of cellulosic δ¹⁸O and δ¹³C is presented for the East African tree Vitex payos for the recent through the late 19th century. The isotope data of individual rings is cross-calibrated against atmospheric variables during the late 20th century to ascertain how and when during the year cellulose obtains its δ¹⁸O and δ¹³C value in response to environmental conditions at the tree site. During the late 20th century the δ¹⁸O and δ¹³C obtained from alpha cellulose from annual rings of V. payos correlates strongly with precipitation amount and with relative humidity, with depleted (enriched) δ¹⁸O and depleted (enriched) δ¹³C values associated with increased (reduced) precipitation and relative humidity. The strongest correlations are found between cellulose δ¹⁸O and the amount of precipitation and the relative humidity during December-February, although temperature contributes to the observed isotopic variance as well. Relative humidity in December-February appears to have the strongest correlation to annual cellulosic δ¹³C values. The results of this cross-correlation study are used to develop a preliminary seasonal growth model for V. payos that reflects variations in precipitation amount and relative humidity during the December-February growing season.; During the late 20th century the East Africa continent and the western Indian Ocean basin experienced anomalously wet conditions in summer (December-February) when sea surface temperatures (SSTs) were anomalously warm in the western Indian Ocean and zonal winds were anomalously strong in association with positive phases of the Indian Ocean Dipole (IOD) and/or El Nino Southern Oscillation (ENSO). Using the correlation between cellulosic isotopic values and hydroclimate variability over East Africa and Indian Ocean SSTs during the late 20th century a preliminary climate reconstruction is proposed for the pre-20th century from V. payos δ¹⁸O and δ¹³C. The isotopic record of V. payos indicates the late 19th century was anomalously wet over East Africa when compared to the late 20th century, consistent with lake level changes and ice core isotopic data. Climate model simulations indicate the wetter pre-20th century climate was a response to enhanced warming in the western Indian Ocean basin, generating a low pressure center and easterly surface winds that brought moisture to East Africa. The annually resolved isotopic data from V. payos suggest much of the observed and modeled hydroclimate variability at multidecadal to century scales is a response to SST anomalies in the western Indian Ocean.; The results of the present study should help guide future phenological studies of V. payos and other Vitex species in equatorial East Africa. Importantly, stable isotope data obtained from individual growth rings suggests that the annual production of cellulose in V. payos occurs during a short seasonal period from January to February, information that could not be inferred directly from tree ring width data alone. Further improvements in sampling tree rings at intra-annual resolution and in-situ monitoring of weather/climate variables, including isotopic variability of moisture would be necessary in order to fully utilize cellulosic δ¹⁸O as a climate proxy, with the potential for becoming a continent-wide hydrologic monitoring network, the first of its kind from Africa. The isotopic database for V. payos is among the few available terrestrial climate records provides estimates of how hydrologic budgets varied over East Africa during the past several centuries. Dataset ice core DataCite Metadata Store (German National Library of Science and Technology) Indian |