More than a quarter of recent anthropogenic CO2 emissions are absorbed by the forests. This is primarily attributed to enhanced plant growth as a result of elevated atmospheric carbon dioxide concentration (eCO2). Without forest carbon uptake, atmospheric CO2 concentration would be much higher now.

However, there is emerging evidence from 1st generation Free-air carbon dioxide enrichment (FACE) experiments (on immature trees) showed that nitrogen availability limit carbon uptake in forests. Whether nitrogen availability will limit carbon uptake in a mature forest remains unknown. But if confirmed, C uptake by terrestrial ecosystems in the future may be much less than we expected, adding tens of ppmv (15 – 150 ppmv) to the predicted 21st-century atmospheric CO2 concentration. If so, a major reduction in allowable emissions of CO2 would be required to achieve the challenging < 2oC target agreed at the UN COP21, which has profound policy and social implications.

The Birmingham Forest Research Institute’s FACE is the only 2nd-generation FACE in a temperate forest in the world. It offers a unmatchable opportunity to examine whether the availability of nitrogen may limit temperate forest carbon uptake or whether the temperate forest ecosystems are resilient to nitrogen shortage by exchanging carbon with microbiomes for N. 

Aim and objectives: The aim of this project is to determine the role of nitrogen availability in carbon cycle in a temperate forest under elevated CO2. The specific objectives are:

To determine whether BIFoR-FACE woodland is nitrogen limited

To determine the nitrogen availability in soils and N2O emissions from the control and fumigated rings at BIFoR-FACE site.

To examine how nitrogen availability affects the soil respiration and carbon storage at BIFoR-FACE woodland.

BIFoR-FACE facility


Atmospheric deposition, soil and soil water, soil availble nutrients (using memberances), leaves, and roots will be collected regularly from BIFoR-FACE site. Samples will be analysed for N species and soil N2O flux will be measured continously to understand the N cycling processes in the control and fumigated rings.

Instruments: Picarro N2O analyser for automatic N2O flux measurements; Shimadzu TOC and TON analyser; Skalar nutrient auto-analyser.

On-going work within the research group: soil respiration is routinely monitored using Li-Cor 8100; Atmospheric deposition and soil available nutrient samples are being taken on a monthly basis.

Training and Skills

CENTA students are required to complete 45 days training throughout their PhD including a 10 day placement. In the first year, students will be trained as a single cohort on environmental science, research methods and core skills. Throughout the PhD, training will progress from core skills sets to master classes specific to the student's projects and themes.

The students will be integrated into the science team of BIFoR, including 6 existing PhD students, science and technical team. Full training on BIFoR-FACE facility access, core methods for the project will be provided from the supervisory team. The planned measurements will provide a strong grounding in carbon and N nutrient cycling research, generate high-impact publications and a strong PhD thesis. Training at sister FACE experiments (AmazonFACE/EucFACE) will also be arranged.


Year 1: Training on soil, soil water, and plant sampling, nitrogen analysis, and literature review; general training via CENTA; N addition experiment in adjacent woodland to determine the nutrient status of the BIFoR-FACE site; soil N2O flux measurement; routine measurement of soil in-situ available N (using soil membrane); soil and water sample analysis;

Year 2: Monitoring of tree growth in N fertilisation plots in woodland adjacent to BIFoR-FACE site; continuous soil, soil water, and plant sampling and N analysis; continuous N2O flux measurement; initial data analysis.

Year 3: Continuous monitoring of tree growth in N fertilisation plots in woodland adjacent to BIFoR-FACE site; N analysis; analysis of N and N2O data against soil respiration; manuscript drafting

Year 4: Thesis write up and manuscript publishing.

Partners and collaboration (including CASE)

Dr. Iain Hartley from Exeter is leading to the belowground processes in AMAZONFACE, a sister facility in the tropical forests. His involvement will enable a harmonised approach between AmazonFACE and BIFoR-FACE and ensures a bigger impact on the results from this PhD studentship. Dr. Liz Hamilton has initiated the soil water and nutrient baseline measurement at BIFoR-FACE sites so has extensive experience in microbial soil nutrient analysis.  

Further Details

Contact Dr. Zongbo Shi, z.shi@bham.ac.uk for more details.