Project highlights

  • Part of a multi-institutional experimental forest research network, thus offering diverse training opportunities and internships in key research institutions (Birmingham and Bangor Universities and UKCEH)
  • Pioneering work on the effects of nitrogen and phosphorus fertilization of mature forest for tree nutrition and climate change mitigation
  • Blended use of cutting-edge isotope and molecular microbiology methodologies to investigate root-microbe interactions and nutrient cycling for climate change mitigation
  • Novel analytical techniques and tools for in-field sensing of nutrients with a potential for continuous monitoring.


Afforestation is seen as a major contributor to meeting the Paris Agreement carbon (C) targets. However, the potential for C uptake, and thus the potential climate mitigation capacity of forests has been severely overestimated by global circulation models not accounting for nutrient limitation. Many nutrients, particularly nitrogen and phosphorus can constrain woodlands gross primary production (GPP). Understanding how nutrient availability and uptake is regulated by plant-soil-microbe feedbacks is paramount to accurately modelling the climate mitigation benefits of forest ecosystems in future climates. In temperate forests, beneficial mycorrhizal fungi and bacteria mediate plant interactions within the soil that include the mineralisation of soil organic matter and uptake of nutrients by trees released during the mineralization. Therefore, understanding the growth response of forests to soil N and P availability and the impact of fertilization is an important aspect of forest ecology required to support future forest management policy for climate mitigation.

This PhD project aims to improve our understanding of nutrient cycling and forest productivity by investigating how soil nutrient availability and root uptake preferences for different nutrient forms in response to N and P availability changes, and to unravel how symbiotic mycorrhizal fungi trade nutrients and carbohydrate with trees in supporting their growth. Predicting the response of forest ecosystems to climate change will only be possible when we fully understand the processes that govern nutrient availability.
Figure 1: Mature Temperate deciduous forest at BIFoR-FACE where N and P manipulation experiments are underway to form part of this PhD studentship. The green mesh in the picture is used for litter fall collection.


University of Birmingham


  • Climate and Environmental Sustainability
  • Organisms and Ecosystems


Project investigator

Prof. Sami Ullah, University of Birmingham ([email protected])


How to apply


This research will utilize a fully factorial (n=3) N and P nutrient addition experiment with a 160-year-old Quercus robur forest located at the Birmingham Institute of Forest Research (BIFoR), aligned with the 5-year NERC QUINTUS project, that will facilitate the investigation of N and P co-limitation and its constraints on forest productivity. Experimental work will include N and P mineralization rates as influenced by fertilization and the underlying soil-plant-microbe interactions, followed by the measurement of root uptake preferences for different nutrient forms as well as tree growth responses. In situ monitoring of nutrients will be carried out using assays in microfluidic devices and portable read-out instrumentation. Mycorrhizal fungi community structure and abundance will be evaluated to understand symbiotic trade-off between the species involved under scenarios of nutrient limitation and enrichment. The indices of these plant-microbe interactions and nutrient cycling will also involve laboratory work at Birmingham and Bangor Universities.

Training and skills

Students will be awarded CENTA2 Training Credits (CTCs) for participation in CENTA2-provided and ‘free choice’ external training. One CTC equates to 1⁄2 day session and students must accrue 100 CTCs across the three years of their PhD.

The student will benefit from supervision across three UK research institutes. The student will be based at the University of Birmingham where a range of analytical training is available. Specific analytical training will be provided in the operation of instruments nutrient analysis, isotope tracing for N and P (Birmingham and Bangor) and mycorrhizal community structure to determine functional groups and their relationship to soil nutrient status and tree growth responses (Bangor). Training and lab experiments at Bangor and UKCEH will open up new avenues for collaborative research training.  Equally, the student will spend time in the School of Chemistry at Birmingham to learn novel analytical methods, microfluidics, and instrumentation.

Partners and collaboration

This studentship benefits from access to the only global temperate forests Free Air Carbon Dioxide Enrichment (FACE) facility and infrastructure (>£20million) ( and the Forest Ecology and Biogoechemistry Laboratory Facilities at Bangor University and UKCEH-Bangor). 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 UKCEH and Bangor University offers significant values in terms of access to facilities. Access to mycorrhizal functionality characterization facilities at Bangor University (>£170k), and an internship at UKCEH will thus support this studentship.

Further details

Contact Prof. Sami Ullah at Birmingham University for further details: ([email protected]).

If you wish to apply to the project, applications should include:

  • A CV with the names of at least two referees (preferably three and who can comment on your academic abilities)
  • Submit your application and complete the host institution application process via: and go to Apply Now in the PhD Geography and Environmental Science (CENTA) section. Please quote CENTA23_B34 when completing the application form.

Applications to be received by the end of the day on Wednesday 11th January 2023. 

Additional information for international applicants

  • All international applicants must ensure they can fulfil the University of Birmingham’s international student entry requirements, which includes English language requirements.  For further information please visit
  • Please be aware that CENTA funding will only cover University fees at the level of support for Home-fee eligible students.  The University is only able to waive the difference on the international fee level for a maximum of two successful international applicants.

Possible timeline

Year 1

  • Literature review and training in analytical instruments (chromatography, colorimetry, isotopes), microfluidics, and experimental design at Birmingham, Bangor University and UKCEH-Bangor. Introductory visits to the BIFoR-FACE in England.
  • Training in the School of Chemistry (6 weeks) on microfluidic devices.
  • Placement (8 weeks) at Bangor University to learn about forest soil microbial and fungal ecology techniques and the use of radioisotopes in mesocosms.
  • Research plan finalisation including statistical design, installation of root boxes for root uptake preferences, setting up decomposition and nutrient availability trial and publication of a literature review paper.

Year 2

  • Monthly measurement of available nutrients in experimental plots, net N mineralization rates and mycorrhizal trade-offs with roots in terms of nutrient and carbon exchanges.
  • Develop colorimetric assays in microfluidic devices for detection of selected anions and cations.
  • Functional genetic markers for N and P uptake and mineralisation will be determined in rhizosphere soils.
  • Application of stable- and radioisotope tracers for quantifying relative availability of N and P in soils to roots under N & P addition treatments and how such changes affect root uptake preferences.
  • Tree NPP measurements (leaf, stem, root and hyphae) in mesoscosms and field trials.
  • Data analysis and compilation of results for publication.

Year 3

  • Continuation of nutrient mineralization, availability and root uptake preferences for different N forms.
  • Obtain and compare data obtained using well-established laboratory methods and microfluidic devices with portable read-out instrumentation.
  • Changes in root carbon allocation to mycorrhizae in response of nutrient availability (Bangor University) and changes in decomposition rates (University of Birmingham).
  • Data analysis and completion of experimental work.

Year 4:

  • 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


  • Vadeboncoeur, M.A. 2010. Meta-analysis of fertilization experiments indicates multiple limiting nutrients in northeastern deciduous forests. Canadian Journal of Forest Research 40(9): 1766–1780.
  • Treseder, K. 2004. A meta-analysis of mycorrhizal responses to nitrogen, phosphorus, and atmospheric CO2 in field studies. New Phytologist, doI:
  • A Gardner, Ds Ellsworth, Ky Crous, J Pritchard, Mackenzie Ar. 2021. Is photosynthetic enhancement sustained through three years of elevated CO2 exposure in 175-year old Quercus robur?, Tree Physiology,
  • Midgley, M. G. and Philips, R. P. 2016. Resource stoichiometry and the biogeochemical consequences of nitrogen deposition in a mixed deciduous forest. Ecology Vol. 97: 3369–3378, DoI;


The proposed field work is mainly based at staffed forests sites in England (e.g. BIFoR-FACE), 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.