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Evaluating the effects of terrestrial ecosystems, climate and carbon dioxide on weathering over geological time: a global-scale process-based approach
Lyla L. Taylor, Steve A. Banwart, Paul J. Valdes, Jonathan R. Leake and David J. Beerling
Philosophical Transactions: Biological Sciences
Vol. 367, No. 1588, Atmospheric CO 2 and the evolution of photosynthetic eukaryotes: from enzymes to ecosystems (19 February 2012), pp. 565-582
Published by: Royal Society
Stable URL: http://www.jstor.org/stable/23076385
Page Count: 18
You can always find the topics here!Topics: Weathering processes, Biological weathering, Climate models, Basalt, Global climate models, Silicates, Vegetation, Paleoclimatology, Minerals, Watersheds
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Global weathering of calcium and magnesium silicate rocks provides the long-term sink for atmospheric carbon dioxide (CO 2 ) on a timescale of millions of years by causing precipitation of calcium carbonates on the seafloor. Catchment-scale field studies consistently indicate that vegetation increases silicate rock weathering, but incorporating the effects of trees and fungal symbionts into geochemical carbon cycle models has relied upon simple empirical scaling functions. Here, we describe the development and application of a process-based approach to deriving quantitative estimates of weathering by plant roots, associated symbiotic mycorrhizal fungi and climate. Our approach accounts for the influence of terrestrial primary productivity via nutrient uptake on soil chemistry and mineral weathering, driven by simulations using a dynamic global vegetation model coupled to an ocean—atmosphere general circulation model of the Earth's climate. The strategy is successfully validated against observations of weathering in watersheds around the world, indicating that it may have some utility when extrapolated into the past. When applied to a suite of six global simulations from 215 to 50 Ma, we find significantly larger effects over the past 220 Myr relative to the present day. Vegetation and mycorrhizal fungi enhanced climate-driven weathering by a factor of up to 2. Overall, we demonstrate a more realistic process-based treatment of plant fungal—geosphere interactions at the global scale, which constitutes a first step towards developing 'next-generation' geochemical models.
Philosophical Transactions: Biological Sciences © 2012 Royal Society