Project highlights

  • Opportunity to investigate how trees will use water in the future using unique forest experimental facility
  • Opportunity to use a wide variety of field and analytical tools (including isotopes) cutting across forestry and water science disciplines
  • Wide scope of international collaboration and research opportunities


The earth’s atmosphere is changing, with increasing CO2 concentrations changing the way the planet looks through its impact on vegetation. The earth is getting greener in some places (refs), and trees all over the earth appear to be changing the way they use water (refs). These changes will impact forests and water resources globally, but until now we have not had a way to test how trees will actually respond to higher CO2 in the future. This project will help fill this important gap by using a globally unique experimental facility that is artificially enhancing the CO2 concentrations of an old growth oak forest in central UK (BIFoR FACE).

In terms of changes to tree water use, this may decrease because stomata will open less frequently, or alternatively the canopy leaf area may increase (‘CO2 fertilization effect’), creating higher overall transpiration rates. These questions over “how much” are important, but there is also the critical, and as yet overlooked, question of “which” water is being taken up and used by trees. This project will utilise δ2H and δ18O stable isotopes as a method to trace the water being used by trees over the growing season at the BIFoR CO2 enrichment experiment (FACE) to gain the first mechanistic insights into which water the forest of the future will use.

This work will have important implications that will directly inform how we think about forests and catchments of the future. Forest regeneration efforts are expanding globally and are widely recognised as providing many beneficial ecosystem services, but how resilient these forests of the future will be with changing water and climate dynamics is highly uncertain. This project will provide critical insights into how they might respond to water stress, how we might think about their planting and management. Finally, this work will also inform catchment water management by examining whether how the results might apply at larger scales, specifically how the water being used by trees in turn changes the water available for soils and rivers and hence the supply of water resources downstream. These forest and water resource implications will be worked on directly with project partners and collaborators in the Environment Agency, as well as other partners in the forestry sector and the UK Met Offce, allowing the student to also translate research into policy practice.

CENTA Flagship

This is a CENTA Flagship Project

Case funding

This project is suitable for CASE funding


University of Birmingham


  • Climate and Environmental Sustainability
  • Organisms and Ecosystems


Project investigator

  • Dr Joshua Larsen (University of Birmingham)




  • Prof. Stefan Krause (University of Birmingham, UK)
  • Prof. Jeff McDonnell (University of Saskatchewan, Canada)
  • Dr Glenn Watts (Environment Agency, UK)
  • Prof Melanie Leng (British Geological Survey)
  • Dr Debbie Hemming (UK Met Office)
  • Dr Scott Allen (University of Nevada, Reno, USA)
  • Prof. Youri Rothfuss (Forschungszentrum Jülich, Germany)

How to apply


The student will use water and vegetation monitoring and sampling techniques to determine changes in water use and ecophysiology at the BIFOR experimental forest facility in collaboration with other researchers. Water samples from rain, soil, and vegetation will be analysed for stable water isotopes over the growing season at the facility. Importantly, the student will be able to compare which water is used by trees at different times under controlled (ambient CO2) and elevated CO2 conditions, providing a robust measure of changing water use and source patters due to climate change. This may also include the use of gas chromatography so that processes rates can be examined.

Training and skills

This project will offer unique training at the interface of physical and biological sciences, including ecophysiology, forestry, biogeochemical cycling, and water transport between soils, trees, and the atmosphere. In addition, it will provide unique training in geochemical tracers such as stable isotopes of water (δ2H and δ18O), and how these can be used to infer both water source and transport dynamics. The project will involve extensive training in field, laboratory, and statistical / mathematical data analysis. The student will also work within a large experimental forestry site (BIFoR), gaining exposure to large scale experimental work, and forestry research. Finally, the student will work closely with partners, especially the Environment Agency, to learn how research can be translated into policy practice.

Partners and collaboration

This project offers extensive training and collaborative opportunities across University and government research institutions. The Environment Agency will provide additional CASE funding support to the student on this project, with co-supervision of the project from Dr Glenn Watts. Further support and training will be available from the vegetation – atmosphere interaction team at the UK Met Office, led by Dr Debbie Hemming. The project also offers the opportunity for extensive international collaboration and learning, especially from the University of Saskatchewan with co-supervisor Jeff McDonnell, and the large water security research groups working there. Further international collaboration is available from Dr Scott Allen, at the University of Nevada, Reno (USA) and Prof Youri Rothfuss at the Jülich agricultural research centre in Germany. In addition, the student will have the opportunity to work with Prof Melanie Leng, who runs the stable isotope component of National Environmental Isotope Facility, based at the British Geological Survey (BGS) near Nottingham. Further international research interactions and networking may also be possible via the recently funded EU COST action (collaborative science network) on water stable isotopes in the critical zone (WATSON).

Further details

For more information on the project, please do not hesitate to contact Josh Larsen

More information on the Birmingham CO2 enrichment experiment can be found here:

More information on the National Environment Isotope Facility at BGS can be found here:

Applications need to be submitted via the University of Birmingham postgraduate portal,, by midnight 11.01.2021. Please first check whether the primary supervisor is within Geography, Earth and Environmental Sciences, or in Biosciences, and click on the corresponding PhD program on the application page.

This application should include

  • a brief cover letter, CV, and the contact details for at least two referees
  • a CENTA application form
  • the supervisor and title of the project you are applying for under the Research Information section of the application form.

Referee’s will be invited to submit their references once you submit your application, but we strongly encourage applicants to ensure referees are aware of your submission and expecting a reference request from us. Students are also encouraged to visit and explore the additional information available on the CENTA website.


This is a CENTA Flagship Project

These have been selected because the project meets specific characteristics such as CASE support, collaboration with our CENTA high-level end-users, diversity of the supervisory team, career development of the supervisory team, collaboration with one of our Research Centre Partners (BGS, CEH, NCEO, NCAS) or student co-designed project. These characteristics are a CENTA priority. Studentships associated with Flagship projects will be provided exactly the same level of support as all other studentships.

Possible timeline

Year 1

Establish monitoring and sampling setup and program for plant-water dynamics and stable isotopes.

Year 2

Begin data analysis and work closely with international collaborators to investigate the water use dynamics being revealed. Continue field monitoring and sampling.

Year 3

Possibility for overseas travel to work with international collaborators on finalising results. Work closely with project partners in the UK (Environment Agency) to summarise policy implications and ways forward for the future of forest and catchment management

Further reading

Allen, S. T., Kirchner, J. W., Braun, S., Siegwolf, R. T. W., and Goldsmith, G. R.: Seasonal origins of soil water used by trees, Hydrol. Earth Syst. Sci. Discuss.,, in review, 2018.

Evaristo, J., S. Jasechko, and J.J. McDonnell. 2015. Global separation of plant transpiration from groundwater and streamflow, Nature doi: 10.1038/nature14983.

Web page—author as an organisation:

More information on the Birmingham CO2 enrichment experiment can be found here:


The work needed to undertake in this PhD are unlikely to be significantly impacted by any restrictions from the COVID-19 pandemic. Although this project has a fieldwork component, it can be completed under COVID restrictions. Full risk assessments and safety procedures have been implemented for working at the BIFoR site. On-site technicians are also trained to take the measurements if needed. Likewise, the laboratory side of the project can be undertaken with appropriate safety protocols.