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| Titel |
The oxygen isotopic composition of phytolith assemblages from tropical rainforest soil tops (Queensland, Australia): validation of a new paleoenvironmental tool |
| VerfasserIn |
A. Alexandre, J. Crespin, F. Sylvestre, C. Sonzogni, D. W. Hilbert |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1814-9324
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| Digitales Dokument |
URL |
| Erschienen |
In: Climate of the Past ; 8, no. 1 ; Nr. 8, no. 1 (2012-02-22), S.307-324 |
| Datensatznummer |
250005375
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| Publikation (Nr.) |
 copernicus.org/cp-8-307-2012.pdf |
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| Zusammenfassung |
| Phytoliths are micrometric particles of amorphous silica that form inside or
between the cells of higher plant tissues throughout the life of a plant.
With plant decay, phytoliths are either incorporated into soils or exported
to sediments via regional watersheds. Phytolith morphological assemblages
are increasingly used as proxy of grassland diversity and tree cover density
in inter-tropical areas. Here, we investigate whether, along altitudinal
gradients in northeast Queensland (Australia), changes in the δ18O
signature of soil top phytolith assemblages reflect changes in mean annual
temperature (MAT) and in the oxygen isotopic composition of precipitation
(δ18Oprecipitation), as predicted by equilibrium
temperature coefficients previously published for silica. Oxygen isotopic
analyses were performed on 16 phytolith samples, after controlled isotopic
exchange (CIE), using the IR Laser-Heating Fluorination Technique. Long-term
mean annual precipitation (MAP) and MAT values at the sampled sites were
calculated by the ANUCLIM software. δ18Oprecipitation
estimates were calculated using the Bowen and Wilkinson (2002) model,
slightly modified. An empirical temperature-dependant relationship was obtained:
δ18Owood phytolith-precipitation
(‰ vs. VSMOW) = −0.4 (±0.2) t (°C) + 46 (±3)
(R2 = 0.4, p < 0.05; n = 12).
Despite the various unknowns introduced when estimating δ18Oprecipitation
values and the large uncertainties on δ18Owood phytolith
values, the temperature coefficient (−0.4 ± 0.2‰ °C−1)
is in the range of values previously obtained for natural
quartz, fresh and sedimentary diatoms and harvested grass phytoliths (from
−0.2 to −0.5‰ °C−1). The consistency supports the reliability of
δ18Owood phytolith signatures for recording relative changes in
mean annual δ18Osoil water values (which are assumed to be
equivalent to the weighted annual δ18O precipitation values
in rainforests environments) and MAT, provided these changes were several
‰ and/or several °C in magnitude. |
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