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| Titel |
Si cycling in a forest biogeosystem – the importance of transient state biogenic Si pools |
| VerfasserIn |
M. Sommer, H. Jochheim, A. Höhn, J. Breuer, Z. Zagorski, J. Busse, D. Barkusky, K. Meier, D. Puppe, M. Wanner, D. Kaczorek |
| 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 ; 10, no. 7 ; Nr. 10, no. 7 (2013-07-24), S.4991-5007 |
| Datensatznummer |
250018357
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| Publikation (Nr.) |
 copernicus.org/bg-10-4991-2013.pdf |
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| Zusammenfassung |
| The relevance of biological Si cycling for dissolved silica (DSi) export from
terrestrial biogeosystems is still in debate. Even in systems showing a high
content of weatherable minerals, like Cambisols on volcanic tuff, biogenic Si
(BSi) might contribute > 50% to DSi (Gerard et al., 2008). However,
the number of biogeosystem studies is rather limited for generalized
conclusions. To cover one end of controlling factors on DSi, i.e., weatherable
minerals content, we studied a forested site with absolute quartz dominance
(> 95%). Here we hypothesise minimal effects of chemical weathering
of silicates on DSi. During a four year observation period
(05/2007–04/2011),
we quantified (i) internal and external Si fluxes of a temperate-humid
biogeosystem (beech, 120 yr) by BIOME-BGC (version ZALF), (ii) related Si
budgets, and (iii) Si pools in soil and beech, chemically as well as by
SEM-EDX. For the first time two compartments of biogenic Si in soils were
analysed, i.e., phytogenic and zoogenic Si pool (testate amoebae). We quantified
an average Si plant uptake of 35 kg Si ha−1 yr−1 – most of
which is recycled to the soil by litterfall – and calculated an annual
biosilicification from idiosomic testate amoebae of 17 kg Si ha−1.
The comparatively high DSi concentrations (6 mg L−1) and DSi exports
(12 kg Si ha−1 yr−1) could not be explained by chemical
weathering of feldspars or quartz dissolution. Instead, dissolution of a
relictic, phytogenic Si pool seems to be the main process for the DSi
observed. We identified canopy closure accompanied by a disappearance of
grasses as well as the selective extraction of pine trees 30 yr ago as the
most probable control for the phenomena observed. From our results we
concluded the biogeosystem to be in a transient state in terms of Si cycling. |
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