Project highlights

  • Part of a multi-institutional experimental forest research network, thus offering diverse training opportunities and internships in national and international (Laurentian University, Canada) institutions.
  • Pioneering the effects of atmospheric nitrogen deposition for soil carbon storage and greenhouse gas emission from forest soils under land use and climate change.
  • Blending of cutting-edge isotope, molecular microbiology, carbon fractionation and greenhouse gas flux technologies for developing and informing sustainable forest management



Conservation of forest ecosystems support a range of vital functions including providing habitat to wildlife, regulation of water resources and capturing atmospheric carbon dioxide (CO2) for long-term storage in soils and in biomass.  Forests capture about 1/3rd of the CO2 emitted into air due to human activities globally and afforestation is increasingly being recognised as a crucial natural option for mitigating against climate change. The ability of forests to store carbon (C)  in soil on a long-term basis depends on the quality/quantify of C produced by forests, which in turn is influenced by the prevailing environments of the forests.

Deposition of agriculturally-derived atmospheric nitrogen pollutants, including reactive nitrogen (ammonia and nitrogen oxides), can also impact nearby forest fragments. As forests are effective scavengers of atmospheric pollutants, this deposition of reactive nitrogen is higher at the edges of fragments than in the interior. Whilst reactive nitrogen deposition enhances forest growth, it also causes an increase in the emission of a potent greenhouse gas-nitrous oxide, with negative implications for global warming.

Recent research has shown that reactive N deposition increases the loss of soil C through enhanced decomposition by soil microbes. Both losses of carbon and enhanced soil nitrous oxide emissions can be highest at the edges of forests. However, these processes are less known in more nitrogen saturated forests. Therefore, the aim of this research is to investigate the impacts of reactive nitrogen deposition on forest soil carbon quality, decomposition rates, microbial community functions and greenhouse gas emission. This will be explored across a gradient of nitrogen deposition intensity, moving from the edges into the interior of forests, located in agricultural landscapes. The work will be undertaken in Britain including an internship at Forest Research and isotopic training at CEH in UK and microbiology experimentation at Laurentian University, Canada to achieve the objectives.

The key expected outcome will be to develop a new understanding of the levels/thresholds of deposition that alters important forest functions. The new knowledge we will make recommendations as to the size and shape of forests in agricultural landscapes for enhancing environmental quality functions of forests.

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 Sami Ullah, University of Birmingham





  • Dr Liz Hamilton, University of Birmingham
  • Dr Elena Vanguelova, Forest Research UK as a Case Partner
  • Prof Niall McNamara, UK Centre for Ecology & Hydrology
  • Dr Mike Morecroft, Natural England
  • Prof. Nate Basiliko, Laurentian University, Canada

How to apply


This research will be undertaken at the experimental forest of the Birmingham Institute of Forest Research (BiFOR), Alice Holt and Thetford experimental forests, and in the forest of Bowland at Gisburn in the UK. These forests represent a gradient of nitrogen deposition to explore forest soil responses to pollution from edge to interior. Stable isotopes of nitrogen and carbon will be used in the laboratory to elucidate the impact of reactive nitrogen levels on key processes underlying C decomposition and greenhouse gas emission, while physical and chemical fractionation of organic carbon and top mineral soil will be used to characterize the quality of soil carbon and its vulnerability to microbial decomposition. DNA-based microbial community fingerprinting will characterize potential changes in fungal and bacterial functional guilds and broader biodiversity at Laurentian University (Canada). In-situ forest soil GHG emissions will be characterised using GHG chambers in combination with gas chromatography and IRGA analysis methods.


Training and skills

The student will benefit from supervision and access to resources across three UK research institutes who are already collaborating on related GHG research in forestry.  The student will based at the University of Birmingham where a range of transferable skills training are available. Specific environmental analytical training will be provided in the operation of instruments including gas chromatography (Birmingham), laser spectroscopy (UK CEH-Lancaster) and cutting-edge molecular ecology and bioinformatics (Laurentian U, Canada). The student will attend the Birmingham University soil analysis practical module, led by S. Ullah. A placement at Forest Research at the Alice Holt Experimental station in year 1 of the project will enable contextualisation of the research plan within the UK forest management and policy needs. In addition, interactions with project members and international partners will enable knowledge exchange and lasting linkages.

Partners and collaboration

This studentship benefits directly from access to the only global temperate forests Free Air Carbon Dioxide Enrichment (FACE) facility with extensive infrastructure (>£20million) ( and the Alice Holt forest at Forest Research( This studentship will benefit from the high experimental costs of these projects and facilities, which is beyond the funding capacity of any single PhD studentship. The involvement of CEH and Forest Research, UK and Laurentian University Canada offers significant values in terms of access to facilities. Access to Picarro analyser (>£170k) at CEH, an internship at Forest Research and microbiology training at Laurentian, will thus support this studentship.


Further details

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

  • Literature review and training in analytical instruments (chromatography, colorimetry, isotopes) and experimental design at Birmingham, Forest Research and UKCEH Lancaster. Introductory visits to the three experimental forests in England.
  • Placement (4 weeks) at Alice Holt, Forest Research to learn about forest management and policy development for sustainable forestry practices.
  • Research plan finalisation including statistical design, installation of chambers for GHG emission, setting up decomposition trial and publication of a literature review paper.

Year 2

  • Seasonal measurement of GHG fluxes from the experimental plots with associated relevant environmental characterisation of soils using in situ sensor technology.
  • Seasonal sampling of soils for soil carbon quality characterization.
  • Application of stable isotope tracers for quantifying relative decomposability of soil organic carbon and quantifying the sources of nitrous oxide production processes.
  • Data analysis and compilation of results for publication.


Year 3

  • Continuation of decomposition, GHG flux and carbon quality characterisation research in the field and analysis of 15N-N2O in samples using laser spectroscopy at UKCEH for source partitioning.
  • Collection of soil samples for incubation in the laboratory using 15N tracers to elucidate controls on microbial pathways of nitrous oxide production and to quantify N2 production due to denitrification across the reactive N deposition gradient.
  • Data analysis and completion of experimental work.
  • Thesis write up, defence and publications.
  • Wider involvement with supervisor linked project partners offering further opportunities for pooling data within a multidisciplinary data pool potentially feeding into large synthesis papers and methodologies.

Further reading

  1. Sgouridis, F, and  Ullah.2017. Soil greenhouse gas fluxes, environmental controls and the partitioning of N2O sources in UK natural and semi-natural land use types. Journal of Geophysical Research-Biogeosciences, doi: 10.1002/2017JG003783.
  2. Vanguelova, E. and R. M. Pitman. 2019. Nutrient and carbon cycling along nitrogen deposition gradients in broadleaf and conifer forest stands in the east of England. Forest Ecology and Management 447: 180-194.
  3. Le Quéré, C., et al. 2016. Global Carbon Budget 2016. Earth Syst. Sci. Data, 8, 605–649,
  4. Morrison Ross; Rowe Rebecca L.; Cooper Hollie M.; McNamara Niall P., 2019, Multi‐year carbon budget of a mature commercial short rotation coppice (SRC) willow plantation. Global Change Biology Bioenergy 11: 895-909
  5. Frey et al. 2014. Chronic nitrogen additions suppress decomposition, and sequester soil carbon in temperate forests. Biogeochemistry 121:305-316,  DOI 10.1007/s10533-014-0004-0
  6. Soucémarianadin et al. 2018. Environmental factors controlling soil organic carbon stability in French forest soils. Plant and Soil 426: 267-286
  7. Finn et al. 2015. Effect of added nitrogen on plant litter decomposition depends on initial soil carbon and nitrogen stoichiometry. Soil Biology and Biochemistry 91: 160-168


The proposed field work is mainly based at staffed forests sites in England (e.g. BIFoR-FACE and Alice Holt Forest site), where effective Health and Safety arrangement are in place for field work with lab prep support under COVID19 compliance requirements. These measures are updated thus making field and the associated lab work resilient. The planned lab components can be adopted to 1) accommodate potential alternative project options, and 2) even switch to the makeshift lab at BIFoR in case of campus lab closure. Arrangements have been agreed where substitution of the Canadian internship will be delivered through online training if travel in year 3  (2023) was not possible.