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Feb 19, 2024 330 likes •483 views

Trees and forests as geo-engineers of past and future global climates David Beerling University of Sheffield (d.j.beerling@sheffield.ac.uk) The (bio)geochemical carbon cycle CO 2 (g) Return of CO 2 to the atmosphere CO 2 (aq) Weathering

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Trees and forests as geo-engineers of past and future global climates

David Beerling University of Sheffield (d.j.beerling@sheffield.ac.uk)

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Return of CO2to the atmosphere burial of CaCO3 Weathering CO2 + CaSiO3  CaCO3 + SiO2 Metamorphism with decarbonation, e.g.: CaCO3+SiO2->CaSiO3+CO2

The (bio)geochemical carbon cycle

CO2 (aq) CO2 (g)

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Fossil forests of Gilboa (385-million-years-old)

Winifred Goldring (1888-1971)

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One of the largest rooting systems Close-up of root ‘trace’/ mould

Archaeopteridalean progymnosperms? (Stein and Berry).

Root type 1

Reconstruction of Archaeopteris (Late Devonian); Beck, 1962 ~10m max ‘Trunk’ diameter = 31cm Minimum lateral extent of rooting = ~7m

Images: Jenny Morris

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Eospermatopteris ‘root mound’ at Cairo

Root type 2

Reconstruction: Eospermatopteris, base of Watteiza; Stein et al., 2007

Cladoxylopsids (Stein and Berry)

~8m Sandstone cast of Eospermatopteris base; Gilboa

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Drilling campaigns (2012, 2013) summary

Total 14 cores drilled to depths of >1.5m

6 cores beneath Archaeopterid stumps ( ) 7 cores beneath cladoxylopsid stumps ( ) 1 ‘control’ on surface without roots

Images/data: Jenny Morris

Palaeo-Vertisols with slicken-sided slip planes. Climate clues: Sub-tropical, with seasonal precipitation

Root trace horizons map to tree size

Original map by Stein, Berry et al. (in prep).

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Functional differences in tree rooting depths and soil mineral interactions

Cladoxylopsid Archaeopterid

0.0 0.5 1.0 1.5 2.0 15 25 35 45 55

Max. rooting depth (m)

Cladoxylopsid trees

Max. trunk base diameter (cm)

Archaeopteridalean trees

Images/data: Jenny Morris

3cm

Drab-halo of 385 Myr-old rootlets

50 100 150 200 250 500 1000 1500 2000 2500 3000 3500 4000 4500 5 10 15 20 25 30

Counts (solid lines) Counts (dashed lines) Transect mm

Micro-XRF transect across a drab-haloed root trace

Fe P Ca Al K

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Artificially enhanced terrestrial weathering as a geoengineering Carbon Dioxide Removal strategy?

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Global annual CO2 emissions and the magnitude of the task

Puny natural weathering C-sink 

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260ppm

Enhanced weathering lowers RCP4.5 and RCP8.5 atmospheric CO2 trajectories (Bern Carbon Cycle model)

CMIP5 RCP4.5 simulations (medium-level mitigation)

Pre-industrial value

Taylor et al. (in prep) 100ppm CMIP5 RCP8.5 simulations (business-as-usual)

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Could we save reef-building corals?

<ocean pH reduces saturation of mineral forms of calcium carbonate, including aragonite (a) which corals precipitation to build their skeletons.

RCP8.5 today (Ricke et al. (2012) Env. Res. Lett. 8, 034003).

Today coral reefs exist where a>3.5 Taylor et al. (in prep)

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