Evolutionary rise of deep-rooting forests and enhanced chemical weathering: Quantitative investigations into the current paradigm

Lead Research Organisation: University of Sheffield
Department Name: Animal and Plant Sciences

Abstract

The co-evolution and geographical spread of trees and deep-rooting systems is widely proposed to represent the 'Devonian engine' of global change that drove the weathering of soil minerals and biogeochemical cycling of elements to exert a major influence on the Earth's atmospheric CO2 history. If correct, this paradigm suggests the evolutionary appearance of forested ecosystems through the Devonian (418-360 Myr ago) constitutes the single most important biotic feedback on the geochemical carbon cycle to emerge during the entire 540 Myr duration of the Phanaerozoic. Crucially, no link has yet been established between the evolutionary advance of trees and their geochemical impacts on palaeosols. Direct evidence that one has affected the other is still awaited, largely because of the lack of cross-disciplinary investigations to date.

Our proposal addresses this high level 'earth system science' challenge. The overarching objective is to provide a mechanistic understanding of how the evolutionary rise of deep-rotting forests intensified weathering and pedogenesis that constitute the primary biotic feedbacks on the long-term C-cycle. Our central hypothesis is that the evolutionary advance of trees left geochemical effects detectable in palaeosols as forested ecosystems increased the quantity and depth of chemical energy transported into the soil through roots, mycorrhizal fungi and litter. This intensified soil acidification, increased the strength of isotopic and elemental enrichment in surface soil horizons, enhanced the weathering of Ca-Si and Ca-P minerals, and the formation of pedogenic clays, leading to long-term sequestration of atmospheric CO2 through the formation of marine carbonates with the liberated terrestrial Ca.

We will investigate this research hypothesis by obtaining and analysing well-preserved palaeosol profiles from a time sequence of localities in the eastern North America through the critical Silurian-Devonian interval that represents Earth's transition to a forested planet. These palaeosol sequences will then be subjected to targeted geochemical, clay mineralogical and palaeontological analyses. This will allow, for the first time, the rooting structures of mixed and monospecific Mid-Devonian forests to be directly linked to palaeosol weathering profiles obtained by drilling replicate unweathered profiles. Weathering by these forests will be compared with the 'control case' - weathering by pre-forest, early vascular land plants with diminutive/shallow rooting systems from Silurian and lower Devonian localities. These sites afford us the previously unexploited ability to characterize the evolution of plant-root-soil relationships during the critical Silurian-Devonian interval, whilst at the same time controlling for the effects of palaeogeography and provenance on palaeosol development. Applying geochemical analyses targeted at elements and isotopes that are strongly concentrated by trees at the surface of contemporary soils, and which show major changes in abundance through mineral weathering under forests, provides a powerful new strategy to resolve and reconstruct the intensity and depth of weathering and pedogenesis at different stages in the evolution of forested ecosystems.

The project is tightly focused on "improving current knowledge of the interaction between the evolution of life and the Earth", which represents one of the three high level challenges within NERC's Earth System Science Theme.

Planned Impact

Our proposed research project addresses this long-standing 'big science' question. We anticipate that our focused multidisciplinary project will, therefore, be the subject of considerable interest not only to a broad spectrum of the scientific community but also to the 'next generation' of researchers in Schools and Universities. Engaging younger generations is especially important as the Earth sciences receive very limited coverage in schools.

Deliverables.
The main deliverables of our project are open-access public archives of data and fossil plant/palaeosol materials, underpinned by methodological and data standards. These are likely to have impacts in both the academic and industrial sectors. A further major deliverable will be significant outreach activities aimed at inspiring and attracting young people into interdisciplinary scientific careers by showing how such activities shed new light on Earth's dynamic history.

Beneficiaries and specific users of this research.
Beneficiaries of the research will include a cross-disciplinary range of scientists from the international academic community, government funded research agencies, and stakeholders. These groups include geochemists, plant physiologists, mycologists, palaeontologists, Earth system modellers, and palaeoceanographers. Our new findings will benefit those sectors involved in the deep-time modelling of geochemical cycles, atmospheric composition and climate. Modellers will benefit from the first quantitative estimates of plant weathering during this critical period to better constrain our understanding of Earth's CO2 history. This diverse array of scientists will benefit from the provision of new data in a field that is traditionally been based on theoretical research rather than driven by empirical research findings.

Impacts will be achieved through :

(1) Dedicated Website. (2) Outreach activities in schools. (3) Outreach activities to the general public and (4) Outreach activities to graduate students in
i) Summer School. ii) MSc course. (5) Industry forum. We will demonstrate the potential applications of our data and materials archives to those involved in the hydrocarbon exploration and development industry.

See Pathways to Impact Plan.
 
Description Part of the project has involved drilling rock cores from a recently discovered site in New York state that has preserved the 'footprint' of one of the Earth's oldest fossil forests but is rapidly deteriorating following exposure by quarrying. The first set of drilled cores sampled in 2012 revealed that this site provided unprecedented opportunities to study how the evolution of trees impacted soil development in the Devonian. The trial cores revealed remarkable preservation of root traces in the palaeosol down to depths of 1.6 m providing a unique opportunity to link the geochemistry of the palaeosol to well-characterized (mapped) fossil forest plant communities. We were able to detect differences in rooting depths of the different tree types present at this exceptional site, allowing the effect of tree type and root depth on pedogenesis to be investigated for the first time in the Devonian era. We received permission from the Town Council to undertake a second set of of drill cores from the site, and we drilled a total of 21 cores each of approximately 1.8-3.0m depth. All the cores have been carefully photographed, logged and their detailed features recorded in diagrams drawn to scale, and a suite of elements analyzed at different depths through the fossil forest soil profile to determine the effects of roots on weathering. One of the cores taken from the edge of the site where the capping layer is intact passed through a fossil fish preserved in the sediments that flooded and gave such good preservation of the site. The research is revealing how the evolution of trees with different rooting forms affected the development of soils. A key finding being that the types of clays that develop are influenced by the trees and that the early trees over 380 million years ago develop soil properties similar to those seen today in forests
Exploitation Route Our findings on the extent to which minerals are altered by the evolution of early trees and their root-mineral interactions in soils have important implications for understanding how the evolution of trees has affected global biogeochemical cycles, and resultant potential feed-backs on atmospheric CO2 concentrations and global climate in the past.
Sectors Environment,Culture, Heritage, Museums and Collections

 
Description The findings from this research, in combination with other NERC, Leverhulme Trust and ERC grants we have had to study the effect of plants and mycorrhizas on mineral weathering and feedbacks in relation to impacts on the geochemical carbon cycle provided essential underpinning evidence and track record of research that led to the award in 2016 of the £10M Leverhulme Centre For Climate Change Mitigation, led by Prof Beerling FRS, at the University of Sheffield. This 10 year research centre, which was launched in the autumn of 2016, has a global reach. Its research into enhanced mineral weathering to help reduce atmospheric CO2 concentrations and reduce ocean acidification, employs experiments with collaborators in the USA, Borneo, Australia and the UK testing effects of rock-dust additions to maize, sorghum, sugar cane, soybean, oil palm and tropical forest plantation crops. The new research also encompasses 'responsible research and innovation' dealing with public perceptions, risk, and ethics. The scale of this research activity applied to address climate change, its high profile in the media and its potential to feed into national and international policies regarding climate engineering solutions to greenhouse gas emissions are major spin-offs arising from this NERC funded proposal that looked back in time to better understand how plant evolution has changed Earth surface processes and global biogeochemical cycles- the strengthening evidence from our work of the power of plants and their mycorrhizal fungal partners and associated soil microorganisms to accelerate mineral weathering has helped to deliver a globally important policy-relevant major research centre coordinating international action to understand the risks and benefits of deploying enhanced weathering as geoengineering tool to reduce climate change, sea level rise and ocean acidification.
First Year Of Impact 2016
Sector Agriculture, Food and Drink,Environment
Impact Types Societal

 
Description Leverhulme Centre for Climate Change Mitigation (LC3M)
Amount £10,000,000 (GBP)
Organisation The Leverhulme Trust 
Sector Academic/University
Country United Kingdom
Start 09/2016 
End 09/2026
 
Description Invited Seminar Swedish University of Agricultural Sciences Uppsal Sweden 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Invited Seminar at SLU entitled: Soil mineral weathering through mycorrhiza evolution- from liverworts to forests, pedogenesis to global biogeochemical cycles: tools to mitigate global warming? Through the seminar and associated meetings with local researchers at SLU I was introduced to the Swedish Programme for monitoring soil quality across 2000 sites per year, returning to each site every decade, which has now been conducted for over 30 years and is a role-model against which the dismal lack of commitment to national monitoring of soil quality by successive UK governments can be judged. Crucially, the well-developed Swedish soil sampling and archiving approach is a role-model that the UK needs to look very closely at post Brexit, and in relation to meeting greenhouse gas emissions targets. This information has already been communicated by me to a UK audience in my presentation at the Managing & Improving Soil Health Workshop run by The Knowledge Transfer Network, at which I gave the Invited opening plenary: Priorities for restoring soil health in arable farming. Sheffield. 14th March 2017.
Year(s) Of Engagement Activity 2017
 
Description Invited Seminar at The University of Nottingham. Rhizosphere Seminar Series. Evolution of plants and their mycorrhizospheres: from liverworts to forests, pedogenesis to global biogeochemical cycles 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Postgraduate students
Results and Impact Presented a talk that summarized our work on plant and mycorrhiza in relation to mineral weathering and global biogeochemistry, concluding with considerations of soil security and the threats to global soils. Raised awareness of soil insecurity and the need for more sustainable soil management in agriculture to deliver better soil quality and soil security. The presentation opened opportunities to discuss the limited teaching of soil science in undergraduate degree programmes and potential opportunities for research collaborations with staff at the University of Nottingham
Year(s) Of Engagement Activity 2016
 
Description Morris, J.L., Beerling, D.J,, Stein, W.E., Berry, C.M., Marshall, J.E.A., Wellman, C.H., Leake, J.R., 2014. Early forest soils from the Middle Devonian of New York State. Oral presentation, 9th European Palaeobotany and Palynology Conference, Padova, 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Other academic audiences (collaborators, peers etc.)
Results and Impact First international presentation of palaeosol rock cores drilled from a fossil forest in New York state- demonstrating rooting depth and pedogenic effects of trees in the Devonian era.

No notable impacts yet.
Year(s) Of Engagement Activity 2014
URL http://geo.geoscienze.unipd.it/eppc2014/Program_August-2014_2.pdf
 
Description Prof D.J. Beerling 2014. Seminar presentation to he Department of Earth Sciences, University of Bristol. 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Undergraduate students
Results and Impact Engaged both undergraduate and postgraduate students in discussion and reflections on the importance of plants in geological processes.

Unable to determine
Year(s) Of Engagement Activity 2014
 
Description Prof DJ Beerling: Closing KEYNOTE. Gordon Research Conferences, CO2 assimilation from genome to biome, New Hampshire. 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Other academic audiences (collaborators, peers etc.)
Results and Impact Closing keynote presentation demonstrating the long-term effects of plants and soil microorganisms in the geochemical carbon cycle

Not known
Year(s) Of Engagement Activity 2014
 
Description Soil Security Programme Royal Society Summer Science Exhibition stand "Soil: Our Buried Treasure" 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact The Soil Security stand had some hands-on demonstrations and I engaged members of the public in discussions on the importance of soil and how it functions- drawing directly on examples from our recent agricultural systems research. I Attended 3 half days and an evening Soiree for fellows of the Royal Society and distinguished guests and members of the press.
Year(s) Of Engagement Activity 2018