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| Titel |
Silicate Mineral Weathering Reponses to Increasing Atmospheric CO2, Plants and Climate Evolution |
| VerfasserIn |
S. A. Banwart, L. Taylor, J. Leake, D. Beerling |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250031627
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| Zusammenfassung |
| Mathematical modelling results of weathering processes in modern soils shed light on the
role of land plants in weathering processes. Application to catchments in the boreal
coniferous region of northern Europe demonstrates a stabilising biological feedback
mechanism between hypothesised increasing atmospheric CO2 levels and silicate mineral
weathering rates. The modelled feedback response agrees within a factor of 2 to that
calculated by a weathering feedback function of the type generally used in global
geochemical carbon cycle models of the Earth’s Phanerozoic atmospheric CO2 history.
Sensitivity analysis to model parameters indicate that the weathering feedback response is
particularly sensitive to soil structure; its porosity, depth and water content. This suggests that
the role of land plants to influence these soil characteristics are an important factor in the
feedback to atmospheric CO2 levels. The model yields a relatively low sensitivity of soil pH
to plant productivity. This is due to more rapid decomposition of dissolved organic carbon
(DOC) under warmer conditions. Because DOC fluxes strongly influence the soil water
proton balance and pH, this increased decomposition rate dampens the feedback
between productivity and weathering. The conceptual model of linkages between
biological, geochemical and hydrological processes is based on the influence of land
plants and their associated soil microbial populations to influence the dynamics of
nutrient elements in soil pore waters and the resulting impact of soil pore water
composition on silicate mineral weathering rates. The translation to the mathematical
description of these processes is through application of mass and flux balance from
first principles. Sources and sinks for elements are based on stoichiometric mass
balance equations that described coupled element transformations during biomass
production and decomposition, microbial decomposition of dissolved organic carbon and
element mass transfer from primary silicate minerals and formation of secondary
oxide and clay mineral phases. Rapid, reversible transformations are described by
thermodynamic mass action and slow, irreversible processes by kinetic mass action.
This process-modelling approach to quantify the biological weathering feedback to
atmospheric CO2 demonstrates the potential for a far-more mechanistic description
of weathering feedback in simulations of the global geochemical carbon cycle. |
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