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| Titel |
High potential for weathering and climate effects of non-vascular vegetation in the Late Ordovician |
| VerfasserIn |
Philipp Porada, Tim Lenton, Alexandre Pohl, Bettina Weber, Luke Mander, Yannick Donnadieu, Christian Beer, Ulrich Pöschl, Axel Kleidon |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250148562
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| Publikation (Nr.) |
 EGU/EGU2017-12827.pdf |
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| Zusammenfassung |
| Early non-vascular vegetation in the Late Ordovician may have strongly increased chemical
weathering rates of surface rocks at the global scale. This could have led to a drawdown of
atmospheric CO2 and, consequently, a decrease in global temperature and an interval of
glaciations. Under current climatic conditions, usually field or laboratory experiments are
used to quantify enhancement of chemical weathering rates by non-vascular vegetation.
However, these experiments are constrained to a small spatial scale and a limited number of
species. This complicates the extrapolation to the global scale, even more so for the
geological past, where physiological properties of non-vascular vegetation may have differed
from current species.
Here we present a spatially explicit modelling approach to simulate large-scale chemical
weathering by non-vascular vegetation in the Late Ordovician. For this purpose, we use a
process-based model of lichens and bryophytes, since these organisms are probably the
closest living analogue to Late Ordovician vegetation. The model explicitly represents
multiple physiological strategies, which enables the simulated vegetation to adapt to
Ordovician climatic conditions. We estimate productivity of Ordovician vegetation with the
model, and relate it to chemical weathering by assuming that the organisms dissolve rocks to
extract phosphorus for the production of new biomass. Thereby we account for limits on
weathering due to reduced supply of unweathered rock material in shallow regions, as well
as decreased transport capacity of runoff for dissolved weathered material in dry
areas.
We simulate a potential global weathering flux of 2.8 km3 (rock) per year, which we
define as volume of primary minerals affected by chemical transformation. Our estimate is
around 3 times larger than today’s global chemical weathering flux. Furthermore, chemical
weathering rates simulated by our model are highly sensitive to atmospheric CO2
concentration, which implies a strong negative feedback between weathering by non-vascular
vegetation and Ordovician climate. |
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