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| Titel |
Possible source of ancient carbon in phytolith concentrates from harvested grasses |
| VerfasserIn |
G. M. Santos, A. Alexandre, J. R. Southon, K. K. Treseder, R. Corbineau, P. E. Reyerson |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 9, no. 5 ; Nr. 9, no. 5 (2012-05-29), S.1873-1884 |
| Datensatznummer |
250007034
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| Publikation (Nr.) |
 copernicus.org/bg-9-1873-2012.pdf |
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| Zusammenfassung |
| Plants absorb and transport silicon (Si) from soil, and precipitation of Si
within the living plants results in micrometric amorphous biosilica
particles known as phytoliths. During phytolith formation, a small amount of
carbon (<2%) can become occluded in the silica structure (phytC) and
therefore protected from degradation by the environment after plant tissue
decomposition. Since the major C source within plants is from atmospheric
carbon dioxide (CO2) via photosynthesis, the current understanding is
that the radiocarbon (14C) content of phytC should reflect the 14C
content of atmospheric CO2 at the time the plant is growing. This
assumption was recently challenged by 14C data from phytoliths
extracted from living grasses that yielded ages of several thousand years (2–8 kyr BP;
in radiocarbon years "Before Present" (BP), "Present" being
defined as 1950). Because plants can take up small amounts of C of varying
ages from soils (e.g., during nutrient acquisition), we hypothesized that
this transported C within the plant tissue could be attached to or even
embedded in phytoliths. In this work, we explore this hypothesis by
reviewing previously published data on biosilica mineralization and plant
nutrient acquisition as well as by evaluating the efficiency of phytolith
extraction protocols from scanning electron microscope (SEM) images and
energy dispersive spectrometer (EDS) analyses from harvested grasses
phytolith concentrates. We show that current extraction protocols are
inefficient since they do not entirely remove recalcitrant forms of C from
plant tissue. Consequently, material previously measured as "phytC" may
contain at least some fraction of soil-derived C (likely radiocarbon-old)
taken up by roots. We also suggest a novel interpretation for at least some
of the phytC – which enters via the root pathway during nutrient acquisition –
that may help to explain the old ages previously obtained from phytolith
concentrates. |
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