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Investigating Devonian trees as geo-engineers of past climates: linking palaeosols to palaeobotany and experimental geobiology

Investigating Devonian trees as geo-engineers of past climates: linking palaeosols to palaeobotany and experimental geobiology
Investigating Devonian trees as geo-engineers of past climates: linking palaeosols to palaeobotany and experimental geobiology
We present the rationale for a cross-disciplinary investigation addressing the ‘Devonian plant hypothesis’ which proposes that the evolutionary appearance of trees with deep, complex rooting systems represents one of the major biotic feedbacks on geochemical carbon cycling during the Phanerozoic. According to this hypothesis, trees have dramatically enhanced mineral weathering driving an increased flux of Ca2+ to the oceans and, ultimately, a 90% decline in atmospheric CO2 levels through the Palaeozoic. Furthermore, experimental studies indicate a key role for arbuscular mycorrhizal fungi in soil–plant processes and especially in unlocking the limiting nutrient phosphorus in soil via Ca-phosphate dissolution mineral weathering. This suggests co-evolution of roots and symbiotic fungi since the Early Devonian could well have triggered positive feedbacks on weathering rates whereby root–fungal P release supports higher biomass forested ecosystems. Long-standing areas of uncertainty in this paradigm include the following: (1) limited fossil record documenting the origin and timeline of the evolution of tree-sized plants through the Devonian; and (2) the effects of the evolutionary advance of trees and their in situ rooting structures on palaeosol geochemistry. We are addressing these issues by integrating palaeobotanical studies with geochemical and mineralogical analyses of palaeosol sequences at selected sites across eastern North America with a particular focus on drill cores from Middle Devonian forests in Greene County, New York State.
devonian plant hypothesis, devonian trees, arbuscular mycorrhiza, mineral weathering, climate change, land plant evolution
0031-0239
787-801
Morris, Jennifer L.
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Leake, Jonathan R.
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Stein, William E.
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Berry, Christopher M.
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Marshall, John E.A.
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Wellman, Charles H.
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Milton, J. Andrew
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Hillier, Stephen
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Mannolini, Frank
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Quirk, Joe
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Beerling, David J.
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Morris, Jennifer L.
5c9404dc-b6f1-4c7e-a13c-50c4c4f322de
Leake, Jonathan R.
dc0d8e92-8016-4519-9440-917f699fd2b6
Stein, William E.
26e1caeb-94c9-4c44-9822-c9bc22bb4e8c
Berry, Christopher M.
5d08651a-8782-47da-8d5c-010806586ef9
Marshall, John E.A.
cba178e3-91aa-49a2-b2ce-4b8d9d870b06
Wellman, Charles H.
508e1b0c-bb06-4723-bd7c-bd889fa83791
Milton, J. Andrew
9e183221-d0d4-4ddb-aeba-0fdde9d31230
Hillier, Stephen
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Mannolini, Frank
cddae877-2b91-4cea-b0ee-e2b7177c412c
Quirk, Joe
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Beerling, David J.
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Morris, Jennifer L., Leake, Jonathan R., Stein, William E., Berry, Christopher M., Marshall, John E.A., Wellman, Charles H., Milton, J. Andrew, Hillier, Stephen, Mannolini, Frank, Quirk, Joe and Beerling, David J. (2015) Investigating Devonian trees as geo-engineers of past climates: linking palaeosols to palaeobotany and experimental geobiology. Palaeontology, 58 (5), 787-801. (doi:10.1111/pala.12185).

Record type: Article

Abstract

We present the rationale for a cross-disciplinary investigation addressing the ‘Devonian plant hypothesis’ which proposes that the evolutionary appearance of trees with deep, complex rooting systems represents one of the major biotic feedbacks on geochemical carbon cycling during the Phanerozoic. According to this hypothesis, trees have dramatically enhanced mineral weathering driving an increased flux of Ca2+ to the oceans and, ultimately, a 90% decline in atmospheric CO2 levels through the Palaeozoic. Furthermore, experimental studies indicate a key role for arbuscular mycorrhizal fungi in soil–plant processes and especially in unlocking the limiting nutrient phosphorus in soil via Ca-phosphate dissolution mineral weathering. This suggests co-evolution of roots and symbiotic fungi since the Early Devonian could well have triggered positive feedbacks on weathering rates whereby root–fungal P release supports higher biomass forested ecosystems. Long-standing areas of uncertainty in this paradigm include the following: (1) limited fossil record documenting the origin and timeline of the evolution of tree-sized plants through the Devonian; and (2) the effects of the evolutionary advance of trees and their in situ rooting structures on palaeosol geochemistry. We are addressing these issues by integrating palaeobotanical studies with geochemical and mineralogical analyses of palaeosol sequences at selected sites across eastern North America with a particular focus on drill cores from Middle Devonian forests in Greene County, New York State.

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Accepted/In Press date: 4 June 2015
e-pub ahead of print date: 14 July 2015
Published date: September 2015
Keywords: devonian plant hypothesis, devonian trees, arbuscular mycorrhiza, mineral weathering, climate change, land plant evolution
Organisations: Geochemistry, Paleooceanography & Palaeoclimate

Identifiers

Local EPrints ID: 379474
URI: http://eprints.soton.ac.uk/id/eprint/379474
ISSN: 0031-0239
PURE UUID: 132e4c5b-f2f7-4ebd-9dd6-b24b6e86e71d
ORCID for John E.A. Marshall: ORCID iD orcid.org/0000-0002-9242-3646

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Date deposited: 21 Jul 2015 14:07
Last modified: 19 Nov 2019 02:04

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