Will more productive Arctic ecosystems sequester less soil carbon? A key role for priming in the rhizosphere ('PRIME-TIME')

Lead Research Organisation: Heriot-Watt University
Department Name: Sch of Energy, Geosci, Infrast & Society

Abstract

High latitudes are warming faster than other regions, and thus serve as critical arenas for climate change studies. Furthermore, they play a pivotally important role in the functioning of the Earth system, storing significant amounts of carbon (C) in soil organic matter (SOM). There is major uncertainty over the vulnerability of these C stores to both climate and land-use change. Previous research has focussed on the direct effects of warming on plant growth and/or SOM dynamics in isolation, but there is increasing evidence that plant-soil interactions complicate these relationships dramatically. Plants not only control litter inputs (both quality and quantity), but may also influence rates of decomposition if the amount of C allocated to the 'rhizosphere' (defined as the area of soil in the vicinity of plant roots in which the chemistry and microbiology is influenced by their growth, respiration, and nutrient exchange) is positively related to microbial activity and the breakdown of older more recalcitrant organic matter. This process is referred to as rhizosphere 'priming', and despite suggestions that it may be critical in determining ecosystem C storage, it remains extremely poorly understood, especially in natural and semi-natural ecosystems.

Changes in the distribution of particular communities, which are already taking place due to climate change and landscape management, may have unexpected impacts on C storage. Work carried out by our research team in the Swedish sub-Arctic suggests that transformations from unproductive heathland ecosystems into more productive deciduous forests could result in counterintuitive net LOSSES of C from soils. Such responses are inadequately simulated by C-cycle models which do not take into account plant-soil interactions in the rhizosphere. Rather, most simulations predict C storage will increase substantially if productivity increases at high-latitudes.

This proposal will determine the impacts of shifts in plant (and associated mycorrhizal) functional composition on the dynamics of SOM. Specifically we will investigate the consequences of a shift from tundra heath to tall shrub communities and deciduous woodland in the Swedish Arctic. We will use a combination of novel experimental approaches, in both the field and the lab, to quantify and understand the role of rhizosphere priming effects (RPEs) for SOM dynamics. In the field in Swedish Lapland we will manipulate the rhizosphere across the mountain birch forest-tundra heath ecotone using experiments ('girdling'; removal of bark, including phloem tissues) to reduce phloem transport of organic C to the roots. We will combine this with manipulating rhizosphere processes using 'in-growth' cores (which selectively prevent fine root and/or fungal hyphal (filament) access) to determine the contributions of roots, mycorrhizal fungi and heterotrophic (soil decomposer) metabolism. We will deploy state of the art microbial molecular analyses to assess the impact of the treatments on fungal community structure (specifically targeting key mycorrhizal fungal groups), and novel C-isotope approaches to quantify RPEs.

The project outputs have the potential to improve significantly regional and global modelling of climate-biogeochemical interactions, with a particular focus on the indirect effects of shifting plant communities. The project has relevance for the pan-Arctic 'shrubification', as well as for UK upland ecosystems being managed for 're-wilding.'

Planned Impact

This is a 'Discovery Science' proposal, addressing a fundamental aspect of the terrestrial C cycle. As such, it has important implications in global change science, for ecosystem management, and for broader society.

The specific beneficiaries of the research include:
- The global change biology and climate sciences research communities (refer to 'Academic Beneficiaries' for specific information on 'how'), and the national and international environmental policy communities. Through tackling the secondary 'cascading' effects of land-use, or climate driven shifts in plant community composition on ecosystem processes and properties, the project aims to quantify and understand a neglected aspect of global change science. The project will link with international research programmes/research networks such as IGBP iLEAPS (Integrated Land Ecosystem-Atmosphere Processes Study) and AIMES (Analysis, Integration and Modeling of the Earth System), and ITEX (the International Tundra Experiment);

- Statutory agencies concerned with C management, provision of ecosystem services, rural land-use, conservation and landscape, catchment hydrology and flood risk. Although, for robust scientific reasons (see 'Case for Support'), we have chosen to base our field research in northern Scandinavia, the processes being addressed have both pan-Arctic as well as UK relevance. In Sweden we will make contact with Naturvårdsverket (The Swedish Environment Protection Agency) to discuss our work and its implications. In the UK, upland management, in particular, has the potential to benefit from the work (e.g. Scottish Environment Protection Agency & Scottish Natural Heritage, and the equivalent devolved agencies in England, Wales and Northern Ireland; Joint Nature Conservation Committee; Forestry Commission (FC); Deer Commission for Scotland; National Park authorities). Our group has research links with the FC and Forest Research and we will ensure that we establish contact with the Scottish Goverment/Forestry Commission Scotland's Woodland Expansion Advisory Group (WEAG; http://www.forestry.gov.uk/weag);

- NGOs and charities concerned with landscape, conservation, tourism and access (e.g. John Muir Trust; National Trust for Scotland (NTS); Moorland Forum; Scottish Native Woods; Woodland Trust; Scottish Wildlife Trust; RSPB; Game and Wildlife Conservation Trust; Ramblers Scotland). Through several of these organisations there are strong links with the general public;

- Reindeer herding communities, and the commercial private sector: Within the specific context of northern Fennoscandia, and more broadly across northern Russia, our work has relevance for reindeer herding communities. Both in Scandinavia and the UK there are also potential links to the power generators (renewables sector; wind/hydro) and water companies, as well as commercial forestry;

- Broader society: There is huge public interest in the wildlands of the North, including the UK, while those living and working in these areas are aware of the on-going and changing land-use demands, potential conflicts, and the challenges of earning a viable living. It is important that society has a robust science base upon which to develop rational policies for upland land-use, and that the ecosystem services provided in these areas can be sustainably managed. Furthermore, through their effects on biodiversity and landscape quality, 're-wilding' and forest regeneration will have significant implications for quality of life, health and aesthetic value. This is relevant both for the local population and businesses reliant upon the uplands, as well as for visitors (from the UK and overseas) and recreational users of these areas.

The 'Pathways to Impact' describes what will be done during and after the project to increase the likelihood of the research reaching the identified beneficiaries and maximise the likelihood of the identified benefits being achieved.

Publications

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Related Projects

Project Reference Relationship Related To Start End Award Value
NE/P002722/1 01/12/2016 30/06/2017 £540,263
NE/P002722/2 Transfer NE/P002722/1 01/07/2017 01/09/2020 £466,333
 
Description Increasingly productive ecosystems in the Arctic, associated with global warming, may not mean that these systems remove (sequester) more carbon from the atmosphere than previously (as has often been assumed in modelling studies). Building on our NERC-funded work in Northwest Territories (NE/K000284/2), Canada, the 'PRIME-TIME' project is now investigating the process of 'rhizosphere priming' (whereby the presence of plant roots with specific types of symbiotic associations with fungi, accelerates the decomposition of soil organic matter in order to release nutrients in plant-available forms), in detail, through intensive fieldwork and experimentation based in Swedish Lapland.

We have completed two field seasons, so far, in this project, and all of the work-packages are proceeding as planned. A compelling set of early results from PRIME-TIME shows the major role of tree and shrub cover for soil metabolic processes (respiration) which rapidly return carbon dioxide to the atmosphere. Measurements of the radiocarbon content of this respired carbon dioxide from research plots which have undergone an experimental reduction in the delivery of recently-photosynthesized carbon dioxide to the root systems, as well as 'control' (un-manipulated plots) demonstrate the importance of this very rapid cycling of carbon in these systems, but also provide a tantalizing indication that rhizosphere priming may be occurring. Our ongoing experiments, process measurements and analyses will provide a clearer indication of what is happening in these widespread ecosystems, in a region which is undergoing rapid environmental change. We are in the process of writing-up our first two seasons of data for submission to a leading international journal.
Exploitation Route In particular we are looking to see our data (i) produce a step-change in our understanding of rhizosphere priming processes (RPEs) and their significance for ecosystem processes and element cycling, leading to publication in top international journals, and (ii) feed through to improved modelling of the C cycle in land surface models. Our team includes Mat Williams, who is leading on modelling, and this work is underway. The potential significance of these processes, as well as the uncertainties surrounding them, have also been highlighted recently by Guenet et al. (2018) (http://onlinelibrary.wiley.com/doi/10.1111/gcb.14069/full). Through our broader links to government agencies and NGOs, as well as to international fora, such as the International Arctic Science Committee (IASC) we believe our results have the potential to influence land-management policy.
Sectors Agriculture, Food and Drink,Communities and Social Services/Policy,Education,Energy,Environment,Leisure Activities, including Sports, Recreation and Tourism,Government, Democracy and Justice,Culture, Heritage, Museums and Collections

 
Description Co-Investigator - Björn Lindahl 
Organisation Swedish University of Agricultural Sciences
Country Sweden 
Sector Academic/University 
PI Contribution This is a close collaboration on the research project, which brings in world-leading expertise from Björn Lindahl (and his team) on soil microbial ecology and community structure. The project Postdoctoral Research Fellow (Dr Thomas Parker) will work with Björn and team at Uppsala for several weeks each year, and benefit from access to their lab facilities and expertise. We provide Björn and team with access to our experiments and samples, as well as our expertise in ecosystem processes and biogeochemistry.
Collaborator Contribution This is a close collaboration on the research project, which brings in world-leading expertise from Björn Lindahl (and his team) on soil microbial ecology and community structure. The project Postdoctoral Research Fellow (Dr Thomas Parker) will work with Björn and team at Uppsala for several weeks each year, and benefit from access to their lab facilities and expertise. We provide Björn and team with access to our experiments and samples, as well as our expertise in ecosystem processes and biogeochemistry.
Impact The project is underway, but it is too early to list outputs at this stage.
Start Year 2016
 
Description Collaboration with Dr Matthias Siewert - Umeå University 
Organisation Umea University
Country Sweden 
Sector Academic/University 
PI Contribution Dr Siewert (Department of Ecology and Environmental Science, Umeå University; https://www.researchgate.net/profile/Matthias_Siewert) is an expert in remote sensing, and he is working on spatial and temporal variations in vegetation dynamics in the area of our field study. Through our experiments, and his acquisition of 'drone' (UAV) imagery, we are able to add value to our respective work.
Collaborator Contribution Specifically, for us, Dr Siewert is using drone imagery in order for us to detect treatment effects on vegetation canopy characteristics (spectral properties). He is involved in the preparation of our first manuscript.
Impact We are currently at the final stages of manuscript preparation involving his work.
Start Year 2017
 
Description NERC 'HYDRA' Partnerships - Iain Hartley 
Organisation University of Exeter
Department Department of Geography
Country United Kingdom 
Sector Academic/University 
PI Contribution This collaboration was made possible through UK DECC funding (via NERC), to Hartley, but with a salary contribution to Wookey. The project concerns quantifying and understandning methane fluxes in landscapes undergoing rapid transition, and my role has been to work with the project PDRA (Mark Cooper) at the Trail Valley research site in Northwest Territories, Canada.
Collaborator Contribution Through PDRA Cooper, Iain Hartley has extended our methane concentration and flux measurements at Trail Valley Creek to the landscape scale. This will also strengthen the links with partner Oliver Sonnentag.
Impact A related outcome is: Hartley IP, Hill TC, Wade TJ, Clement RJ, Moncrieff JB, Prieto-Blanco A, Disney MI, Huntley B, Williams M, Howden NJK, Wookey PA, Baxter R (2015) Quantifying landscape-level methane fluxes in subarctic Finland using a multiscale approach. Global Change Biology, 21, 3712-3725.
Start Year 2013
 
Description NERC 'HYDRA' Partnerships - Mark Garnett 
Organisation Natural Environment Research Council
Department NERC Radiocarbon Facility (Environment)
Country United Kingdom 
Sector Academic/University 
PI Contribution Development and application of state-of-the-art 14C isotope approaches (at natural abundance levels) to global C cycle research.
Collaborator Contribution Development and application of state-of-the-art 14C isotope approaches (at natural abundance levels) to global C cycle research.
Impact Hartley IP, Garnett MH, Sommerkorn M, Hopkins DW, Fletcher BJ, Sloan VL, Phoenix GK, Wookey PA (2012) A potential loss of carbon associated with greater plant growth in the European Arctic. Nature Climate Change. DOI: 10.1038/NCLIMATE1575. Hartley IP, Garnett MH, Sommerkorn M, Hopkins DW, Wookey PA (2013). The age of CO2 released from soils in contrasting ecosystems during the arctic winter. Soil Biology and Biochemistry 63: 1-4.
Start Year 2013
 
Description NERC 'HYDRA' Partnerships - Mathew Williams 
Organisation University of Edinburgh
Country United Kingdom 
Sector Academic/University 
PI Contribution We are linking two NERC-funded projects (ours and 'CYCLOPS', coordinated by Mat Williams) to improve our understanding of processes by integrating experimental and observational data using ecosystem and biogeochemical models. This also involves Prof Pete Smith (Aberdeen) who is a direct participant in our broader project.
Collaborator Contribution Mutual expertise and data for modelling activities.
Impact Hartley IP, Hopkins DW, Garnett MH, Sommerkorn M, Wookey PA (2008) Soil microbial respiration in arctic soil does not acclimate to temperature. Ecology Letters 11:1092-1100. Garnett MH, Hartley IP, Hopkins DW, Sommerkorn M, Wookey PA (2009) A passive sampling method for radiocarbon analysis of soil respiration using molecular sieve. Soil Biology and Biochemistry 41:1450-1456. Hartley IP, Hopkins DW, Garnett MH, Sommerkorn M, Wookey PA (2009) No evidence for compensatory thermal adaptation of soil microbial respiration in the study of Bradford et al. (2008). Ecology Letters 12:E12-E14. Hartley IP, Hopkins DW, Sommerkorn M, Wookey PA (2010) The response of organic matter mineralisation to nutrient and substrate additions in sub-arctic soils. Soil Biology and Biochemistry 42:92-100. Hartley IP, Garnett MH, Sommerkorn M, Hopkins DW, Fletcher BJ, Sloan VL, Phoenix GK, Wookey PA (2012) A potential loss of carbon associated with greater plant growth in the European Arctic. Nature Climate Change. DOI: 10.1038/NCLIMATE1575. Hartley IP, Garnett MH, Sommerkorn M, Hopkins DW, Wookey PA (2013). The age of CO2 released from soils in contrasting ecosystems during the arctic winter. Soil Biology and Biochemistry 63: 1-4. Hartley IP, Hill TC, Wade TJ, Clement RJ, Moncrieff JB, Prieto-Blanco A, Disney MI, Huntley B, Williams M, Howden NJK, Wookey PA, Baxter R (2015) Quantifying landscape-level methane fluxes in subarctic Finland using a multiscale approach. Global Change Biology, 21, 3712-3725.
Start Year 2013
 
Description Partnership with Dr Lorna E Street (NERC IRF) 
Organisation University of Edinburgh
Country United Kingdom 
Sector Academic/University 
PI Contribution We are working directly in associate with Dr Street (i) on field-based experiments in Swedish Lapland (implementing experimental treatments, collecting and analysing samples), and (ii) on joint research manuscripts incorporating ecological modelling.
Collaborator Contribution Dr Street is leading on unique experiments on rhizosphere dynamics that we have established, and maintain, collaboratively.
Impact This work is on-going and too early to report outputs at this stage.
Start Year 2018
 
Description BES (British Ecological Society) Annual Meeting 2016 Presentation 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Presentation in session S33: Ecosystem Ecology & Function, Biogeochemical Cycles & Plant-Soil Interactions. Presentation title " Could 'shrubification' and forest expansion threaten soil carbon stocks in the Arctic?" Initiated substantial discussions subsequently, albeit with professional practitioners.
Year(s) Of Engagement Activity 2016
URL https://www.britishecologicalsociety.org/wp-content/uploads/2016/11/BES-Programme-2016-web.pdf
 
Description Conference presentation ar 'Polar2018', Davos, Switzerland, 21 June 2018 - "Will Rhizosphere ┬┤Priming┬┤ Limit Soil Carbon Sequestration in a Warmer Arctic?" 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact This was a conference presentation at Polar2018, Davos, Switzerland, 21 June 2018, co-authored by Philip A Wookey, Thomas C Parker, Karina E Clemmensen, Mark H Garnett, Iain P Hartley, David Johnson, Björn D Lindahl, Lorna E Street, Jens-Arne Subke & Mathew Williams .

Introducing research on global change and ecosystem dynamics to an international audience.

Broadening understanding of global change impacts on ecosystem dynamics, and their feedback implications on climate.

This presentation, focused on what happens around plant roots in a changing Arctic, attracted a large audience (standing room only) interested in global change and the carbon cycle. Lively debate afterwards.
Year(s) Of Engagement Activity 2018
URL http://www.professionalabstracts.com/POLAR2018/iPlanner/#/presentation/575
 
Description Edinburhg International Science Festival - Meet the Polar Scientists 
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 An exhibition as part of the EISF presenting a range of Arctic research themes, aimed at all ages and including hands on activities and demonstrations. A team of 9 scientists were involved in delivering the event and meeting the public.

In total 1,627 visitors were admitted to Our Dynamic Earth across the two days. Dynamic Earth in-house audience engagement research suggests that around 60% of day entry visitors engage with the additional activities available, so we directly engaged with roughly 975 people over the event.

We received the following feedback from the ODE Science Engagement Officer:

"I just wanted to pass on a massive 'thank you' to you both and all of your amazing team who contributed to the Meet the Polar Scientist Programme at Dynamic Earth as part of the 2018 Edinburgh International Science Festival. This was a fantastic opportunity for us to work together to inspire and engage our audiences with Polar science, and broaden their horizons on the range of scientific research underway at Earth's Poles shaped by researchers right here in Edinburgh. As you know, one of the priorities for us as a science and discovery centre is to act as a platform for the research community to share their work and connect with public audiences, so thank you ever so much for supporting us on our mission to and engage and inspire everyone with an understanding of how the Earth works.

The activities you have developed and deliver are such a big hit with audiences of all ages and backgrounds and there was truly something for everyone to engage and connect with across the two days. I thought there was perfect pitching across all the experiences to ensure that content was accessible and delivered in the most appropriate format for visitors with different expectations from them, and that all your team were so warm, friendly and approachable in their interactions with audiences. Thank you so much for all of this."
Year(s) Of Engagement Activity 2018
 
Description Invited Public Lecture - University of Calgary, Arctic Institute of North America - "Biospheric feedbacks and the 'Arctic Amplification' of climate change" 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact This was an invited presentation as part of the Arctic Institute of North America's 'Arctic Speaker Series 2017-18'. Purpose; to engage with the public on key research topics relating to the Arctic.

Title: "Biospheric feedbacks and the 'Arctic Amplification' of climate change"

The talk resulted in a lively debate subsequently.
Year(s) Of Engagement Activity 2018
URL https://arctic.ucalgary.ca/arctic-speaker-series-2017-18
 
Description Public ('inaugural') lecture in connection with professorial appointment to the University of Stirling. 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Professorial inaugural lecture in connection with appointment, entitled "Biospheric feedbacks and the 'Arctic Amplification' of climate change."

The purpose of this is to 'profess' the discipline, and provide an accessible overview of a personal career contribution. The talk was delivered as one of the opening contributions to the University of Stirling's 2018 Research Week.
Year(s) Of Engagement Activity 2018
 
Description Public Talk 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Public/other audiences
Results and Impact Talk to the Cheshire Wildlife Trust on mycorrhizal fungi
Year(s) Of Engagement Activity 2018
 
Description Stirling Science Soc Presentation - "Arctic Terrestrial Ecology - Phil's Pictorial Guide" 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Undergraduate students
Results and Impact Invited presentation on my research career, and what inspired it.
Year(s) Of Engagement Activity 2019