Quinquennial (half-decadal) carbon and nutrient dynamics in temperate forests: Implications for carbon sequestration in a high carbon dioxide world

Lead Research Organisation: University of Birmingham
Department Name: Sch of Geography, Earth & Env Sciences


Having more carbon dioxide (CO2) in the atmosphere has increased rates of photosynthesis, promoting greater tree growth and carbon storage in forests. This process is called 'CO2 fertilisation' and results in 2-3 billion tonnes of carbon being removed from the atmosphere each year, which is 25-30% of the carbon put into the atmosphere by human activity annually. CO2 fertilisation, thus, greatly reduces rates of global warming.

The fight against climate change relies on CO2 fertilisation continuing into the future; the Paris climate agreement emphasises that global efforts are required to limit the amount of carbon we release to that which trees, soil, and oceans can absorb naturally. Increased carbon storage in mature forests, due to CO2 fertilisation, is considered to be the most important reason for the current carbon uptake. But, looking forward, it is highly uncertain whether such high rates of uptake will continue, because the production of plant biomass also requires the uptake of nutrients from soils. The availability of key nutrients (especially nitrogen and phosphorus) may severely limit the ability of trees in mature forests to continue to grow more rapidly.

Studying mature forests is particularly important when determining whether nutrient availability may limit future carbon uptake by land ecosystems. Firstly, as discussed above, mature forests are likely the most important absorbers of carbon on land; secondly, nutrient availability is generally low in mature forests because the roots of mature trees may have already fully explored their soils in their search for key nutrients. If mature forests are unable to access more nutrients in the future and maintain their carbon uptake, then this would have major implications for our society. It would mean that we would have to reduce our carbon dioxide emissions by a greater extent, and more rapidly than currently expected, if we are to avoid the most serious consequences of climate change.

Temperate forests currently absorb almost as much carbon as the emissions from all EU nations. While tropical rainforests are, of course, important, mature temperate forests are calculated to be fourfold more efficient at absorbing carbon, and so merit special attention. To be able predict how mature temperate forests will respond in the future, it is critical that we determine whether greater carbon dioxide concentrations in the atmosphere will allow mature trees in temperate forest to:

1) take up more nutrients from soils, and/or,
2) increase the efficiency with which they use available nutrients to produce new plant tissue.

Manipulating CO2 for whole stands of mature forest is challenging and expensive, and until now there has been no experiment that would have allowed us to address the uncertainties discussed above. All this has changed with the establishment of a new experimental facility in mature oak forest in central England. Leveraging a £15m philanthropic gift and an equivalent University of Birmingham investment, a whole-ecosystem free-air carbon dioxide enrichment (FACE) experiment has been set-up, which is successfully forest patches to CO2 concentrations more than one third higher than current levels. In the FACE ecosystem, the canopy trees are at least 160 years old and the site has been forested for the last 400 years.

QUINTUS aims to carry out the detailed measurements of nutrient cycling (more than 20,000 analyses) that are required to answer the two key processes outlined above and, thus, determine how a mature temperate forest responds to rising atmospheric CO2. This new experimental understanding will then be used to develop and test the next generation of the computer models which are used to predict future rates of climate change. QUINTUS will deliver a foundational change in our understanding of future C uptake in temperate forests, and in mature forests generally. Such an advance is urgently required and has major societal relevance.

Planned Impact

QUINTUS aims to clarify the role of nutrient availability on carbon sequestration by temperate forests in a changing atmosphere. This is science with profound societal impact; results contribute an essential evidence base informing the models used to predict future climate. The consortium has global reach in its partnership, and will have global reach because the terrestrial carbon cycle (and thus climate change) is a pressing concern to global communities of research users, policy-makers, climate-sensitive industrial sectors, and people.

BIFoR FACE is already a powerhouse of stakeholder engagement, having hosted an average of 3 events per fortnight throughout 2017 and 2018 at all levels from government to citizen.
Who might benefit? Potential socio-economic beneficiaries include: (i) the UK Met Office and other Earth-system modelling agencies; (ii) UK government departments of Business, Energy & Industrial Strategy (BEIS) and Environment, Food & Rural Affairs (Defra); (iii) the Intergovernmental Panel on Climate Change (IPCC) and other national and international policy-makers; (iv) forest authorities; (v) NGOs and concerned citizens. We have well-proven conduits to each of these stakeholders.

How might they benefit? We will interact with each impact constituency in the way best suited to each of them, to ensure reflexive development of change in practice.

1. UK Met Office and other Earth-system modelling agencies: The new process understanding and observational constraints in temperate forests under high CO2 will improve land surface models. We will work directly on the UK community land surface model, JULES. The improved JULES model, ready to be incorporated into the next generation UK Met Office Earth System Model, will contribute to IPCC assessments beyond the current cycle. Impact in this sphere is most effectively delivered through research co-production with the Met Office (Hemming, Wiltshire), cascading outwards through the Met Office's and Co-I Sitch's involvement in the annual Global Carbon Budget of the Global Carbon Project.

2. BEIS & Defra: we will provide the evidence to underpin future assessments of the natural capital of mature UK forests. By studying the throughput of macronutrients, water, and energy through the BIFoR FACE site, we will improve the evidence base for assessment of the regulating ecosystem services (including climate regulation) provided by UK deciduous woodlands. Impact in this sphere will be delivered by governmental advice channels including the West Midlands Forestry and Woodlands Advisory Group, of which the PI is a member.

3. IPCC and other national and international policy-makers: policy-makers require evidence quantifying the land carbon response to elevated CO2 in order to assess climate mitigation costs and pathways to sustainable living. Impact in this sphere will be delivered through expert involvement in international scientific bodies (Met Office partner provides several co-authors to the next IPCC AR6 WG1 report) and through government channels (item (2), above).

4. Forestry authorities: Forestry authorities will benefit from the new understandings on the nutrient factors in sustainable forest management. Impact in this sphere will be delivered through broader BIFoR knowledge exchange workshops, to which we will contribute during the project. All BIFoR projects come together each January to share outputs with stakeholders. See also our letter of support from one of the UK's largest and most innovative forest estates (Norbury LoS).

5. Citizens, particularly young people: the BIFoR-FACE facility is already being used as a flagship for STEM education on climate change issues through our strong links to the Royal Geographical Society and Royal Society of Biology. QUINTUS outreach will focus on the interaction of nutrient and carbon cycles, and be made available to stakeholder websites, e.g. www.schoolscience.co.uk.
Description It is still very early in this project, but our results, building on those produced by earlier projects, are providing a consistent and coherent picture of the effects of enhanced CO2 on the dynamics and ecology of a mature deciduous temperate forest. We have disseminated these early findings to non-academic stakeholders through a wide range of webinars and through participation in stakeholder bodies such as the Forest and Woodlands Advisory Committee (West Midlands).
First Year Of Impact 2020
Sector Agriculture, Food and Drink,Education,Environment
Impact Types Policy & public services

Description Chair, Defra Trees and Woodlands Scientific Advisory Group to the England Tree Planting Programme (TaW-SAG)
Geographic Reach National 
Policy Influence Type Participation in a advisory committee
Description Evidence submitted to EFRA Committee consultation on England Tree Strategy
Geographic Reach National 
Policy Influence Type Gave evidence to a government review
URL https://committees.parliament.uk/work/595/tree-planting-and-woodlands/
Title Root boxes with double face windows 
Description We designed a root box for installation in soils for accessing roots from time to time for exudates collection and nutrient update preferences studies. 
Type Of Material Technology assay or reagent 
Year Produced 2020 
Provided To Others? No  
Impact An advanced root box design with two sided Perspex window for direct access to roots from trees test and works fine. A method paper will be published on this. 
Title BIFoR FACE environmental monitoring data 
Type Of Material Database/Collection of data 
Year Produced 2020 
Provided To Others? Yes  
URL http://edata.bham.ac.uk/564/
Description Metabolomics analysis at Universitat Jaume I, Spain 
Organisation Jaume I University
Country Spain 
Sector Academic/University 
PI Contribution Prof Victoria Pastor at Universitat Jaume I, is our new collaborator, who is not only assisting in metabolomics analysis but in the interpretation of data as well. The analysis and data interpretation is a substantial contribution to the project.
Collaborator Contribution Support in metabolomics analysis and data interpretation. Will provide training to the PDRA on post in metabolomics data interpretation.
Impact Sample analysis Data interpretation support
Start Year 2020
Description BBC Radio4 Open Country 
Form Of Engagement Activity A broadcast e.g. TV/radio/film/podcast (other than news/press)
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact BBC Radio 4 Open Country interview on urban green space: "Birmingham, tree city of the world", first aired 24th April 2020.
Year(s) Of Engagement Activity 2020
URL https://www.bbc.co.uk/programmes/m000hghz
Description BBC1 News Shukman FACE visit 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact BBC One News item on trees and the global carbon cycle by David Shukman, BBC Science Editor, 14th March 2020, supported by online material.
Year(s) Of Engagement Activity 2020
URL https://www.bbc.co.uk/news/science-environment-51633560
Description BGS (online seminar) 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Schools
Results and Impact An Introduction to BIFoR FACE: Invited webinar to West Midlands branch of British Geographical Association, joint with Jerry Pritchard.
Year(s) Of Engagement Activity 2020
Description Drunken Xmas Trees 
Form Of Engagement Activity A magazine, newsletter or online publication
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Policymakers/politicians
Results and Impact Birmingham Perspective, 16th December 2020: Thirsty and Drunken Xmas Trees. A light-hearted online essay introducing the effects of permafrost thaw on boreal forests to a general audience.
Year(s) Of Engagement Activity 2020
URL https://www.birmingham.ac.uk/research/perspective/drunken-christmas-trees.aspx
Description ICF webinar 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Professional Practitioners
Results and Impact Sci-fi forest: propelling an English Oak woodland into 2050. Invited webinar, Institute of Chartered Foresters, 11 June 2020.
Year(s) Of Engagement Activity 2020
URL https://www.charteredforesters.org/event/icf-members-hour-sci-fi-forest-propelling-an-english-oak-wo...
Description Landscape Learn 
Form Of Engagement Activity A magazine, newsletter or online publication
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Professional Practitioners
Results and Impact ARMK interviewed by landscape architect Jo Gibbons in "Conversations on Urban Forestry", Landscape Learn, 2019.
Year(s) Of Engagement Activity 2019
URL https://www.landscapefirst.it/rubriche/book-reviews/we-are-forest-conversation-on-urban-forestry/?fb...