Project Highlights:

  • Opportunity to make major new insights into how forests control greenhouse gas emissions.
  • Extensive overseas field work potential to tackle a major global forest biogeochemistry and ecology question.
  • Access to and training in leading edge instruments and methods through world leading forest research institute.

Forest are well known for their globally important role in the carbon cycle. Despite this many questions remain, especially with lesser known but highly important trace gas emissions (methane and nitrous oxide) which play a critical role in forest carbon and nutrient cycling. After CO2, methane (CH4) and nitrous oxide (N2O) are the most important greenhouse gases in the atmosphere. Recent world leading research by the supervisory team has shown tree stems to be one of the most important emission pathways for these greenhouse gases from forests (Pangala et al 2017; Welch et al 2019) yet trees remain understudied components of the CH4 and N2O cycles.

While we know trace gasses can be transported through and emitted from tree stems, the spatial variability can be extremely high, between forests, between trees and across stems. For example, trace gas exchanges varying both up the tree stem and radially around it. Ecological, biogeochemical and physical variables such as bark roughness, orientation, bark moisture, cryptogamic covers, the interior pockets of rot in the stem and other morphological interior features likely control this variability. But these controls are not understood. This is essential information if we are to understand how trees exchange climate relevant gases under a range of conditions – but notably in response to infections which can devastate whole forests. Tree death will alter both local soil biogeochemistry and the inner architecture of standing trees, promoting higher trace gas emissions. This could also happen in response to fire, flood or drought.

You will employ novel techniques including sonic and x-ray tomography to peer into living and dead tree stems to view these previously hidden controls. Further, you will use the latest field portable analytical equipment to directly observe and analyse CO2 and trace gas exchange in forests within Canada, Switzerland and the BIFoR FACE site in the UK where trees are exposed to elevated CO2 concentrations. The assembled supervisory team within the Birmingham Institute of Forest Research (BIFoR) and Forest Research has access to the full range of forests and techniques (e.g. Fig 1) to enable each of these questions to be investigated.

Tree stems being sampled in Peru and the UK for methane emissions in real-time using laser-based trace gas analysers.


You will use the latest laser-based analysers to measure CO2 and trace gas exchange in the field. This will include the use of gas chromatography so that processes rates can be examined. Experiments will be performed to test the influence of different variables (mentioned above) over CO2 and trace gas flux in both controlled and field conditions. The new method of sonic tomography will be applied to understand how the internal architecture of the trees influences surface fluxes observed. This will be coupled with internal sampling to measure internal trace gas concentrations and process rates. The opportunity exists to also investigate the tree stem/root trace gas continuum as part of the Finnish MetNet project where x-ray tomography will be employed. Collectively, these methods will lead to the development of both conceptual and numerical models that will explain the heterogeneity in trace gas fluxes observed in response to a range of variables.

Training and Skills

Training will be provided in tree stem greenhouse gas flux measurements, working at the BIFoR FACE experiment. Further training will be provided in experimental approaches in ecosystem science, tomography, data analysis and presentation skills. You will be exposed to a wide range of highly employable skills in ecosystem research and will gain further kills development from partners at European and Canadian institutions.


Year 1: Develop chambers, gain training in their deployment, complete review of the literature and commence studies at UK sites

Year 2: Continue measurements in local sites, organise and complete measurement campaigns in Canada and Switzerland. Give a poster presentation at a UK conference or workshop.

Year 3: Complete analyses and data analysis, write-up thesis, submit paper(s) and give a talk at an international conference.

Partners and collaboration (including CASE)

Partners include Dr Ari Laurén, Associate Professor in Ecosystem Modelling at the School of Forest Sciences, Faculty of Science and Forestry, University of Eastern Finland. Dr Lauren is the Principal investigator of the MetNet project devised to investigate how tree roots facilitate the exchange of methane from the soil to the atmosphere. The CASE partner, Dr Sirwan Yamulki (Forest Research) will support access to extensive and well-instrumented forest research infrastructure and provide expertise in a range of forest GHG measurement techniques.

Further Details

This project has been selected as a CENTA Flagship project. This is based on the projects fulfilment of specific characteristics e.g., NERC 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 a potential applicant co-development of the project.