2025-B22 Changing seasons in a changing world: the role of phenology and physiology on carbon sequestration in temperate forests

Project highlights

Focus on physiology as essential for climate resilience of trees

Focus on phenology as essential for climate resilience of forest ecosystems

Foundational understanding of Nature-based Climate Solutions

Overview

The overarching aim of the study is to assess the different contributions of phenological and physiological processes on recent changes in carbon sequestration in temperate forests and consider how these processes may influence carbon sequestration in the future.

This study will use an indicator-based approach to characterise recent historic variations and trends in temperate forest phenology e.g., start of season, growing season length, and physiology e.g., gross primary productivity, biomass, and how these different processes relate to carbon sequestration. Phenological and physiological processes are both important influences on carbon sequestration, but they are regulated by different environmental drivers, timescales, and feedbacks. Therefore, understanding the differential roles of phenology and physiology (as well as their interactions) on carbon sequestration will help to assess the relative importance of these processes for future carbon changes.

The implications of current and future projected changes in temperate forest phenology and physiology will be considered in the context of changes in carbon sequestration, including the potential for managing these ecosystems to enhance carbon sequestration.

Background
Forests are a major global carbon sink, they cover over 30% of the land surface and currently sequester about twice as much carbon as they emit each year (Harris et al., 2021). These processes are extremely challenging to monitor, and therefore it is difficult to determine the extent to which forests modify atmospheric CO2 concentrations. Temperate forests are one of the main forest biomes, covering about 16% of the global forest area (FAO, 2020), and relative to other forest biomes, temperate forests are very efficient at absorbing carbon, highlighting their importance for carbon sequestration.

To reduce significantly the risks and impacts of climate change, the Paris Agreement (UNFCCC, 2015) committed global governments to limit the increase in global average temperature to 1.5°C above pre-industrial levels. The latest science (IPCC, 2018) shows that net anthropogenic carbon emissions would need to reach net-zero by around 2050 to achieve the 1.5°C goal. Transitioning to a world with net-zero carbon emissions is one of the greatest challenges currently facing humanity. Reaching net-zero will require both reductions in greenhouse gas emissions and increases in CO2 sequestration from the atmosphere, the latter of which requires a substantial contribution from forests.

Figure 1: Phenology at BIFoR FACE. (Top) Canopy greenness from 2016-2020 showing typical deciduous forest spring flush and autumn leaf-drop. The yellow trace repeats the 2016 pattern as a guide to interannual variability. (Bottom left) The normalized difference vegetation index (NDVI), a very commonly-used index of productivity, for the BIFoR FACE Phenocam. Strong interannual variation of spring/autumn timing and overall productivity (the area under each curve) is apparent in the data. (Bottom right) Co-supervisor Anna Gardner on top of the 40-m instrumented tower, tending to Phenocam and flux measurement data. Two of the six FACE infrastructure plots for the elevated CO2 treatment are shown in the background.

CENTA Flagship

This is a CENTA Flagship Project

Case funding

This project is suitable for CASE funding

Host

University of Birmingham

Theme

Climate and Environmental Sustainability
Organisms and Ecosystems

Supervisors

Project investigator

A. R. MacKenzie, BIFoR, University of Birmingham, [email protected]

Co-investigators

Dr Anna Gardner, University of Birmingham, [email protected]
D. Hemming, UK Met Office, [email protected]
F. Gerard, UKCEH Wallingford, [email protected]
I. Robertson, Swansea University, [email protected]

How to apply

Each host has a slightly different application process.
Find out how to apply for this studentship.
All applications must include the CENTA application form.
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Methodology

The work will utilise a range of observations relevant for monitoring phenological and physiological variations across spatial scales from individual sites to global networks and remote sensing, and for temporal scales from minutes to years. The study will combine phenology and physiology data from the elevated CO2 manipulation experiment, BIFoR FACE (Gardner et al., 2021; Norby et al., 2024; McClory et al., 2023 and see Further Details, below). A wide range of other data sources will include individual site measurements of tree ring growth, leaf area index, carbon fluxes and stores; canopy phenology monitoring utilising the global PhenoCam network (NAU, 2022) and vegetation indices derived from large-scale satellite monitoring.
Variations in the phenological and physiological indicators will be compared statistically with estimates of net carbon sequestration at a range of temperate forest flux sites (e.g., from FLUXNET (No date)), and cross-compared across the different scales to quantify relationships and sensitivities between carbon sequestration estimates and the phenological and physiological indicators.
Future changes in the phenological and physiological indicators will be assessed for temperate forest biomes using IPCC CMIP6/7 model projections (of 2050 and beyond), and the potential changes in carbon sequestration will be assessed.

Training and skills

DRs will be awarded CENTA Training Credits (CTCs) for participation in CENTA-provided and ‘free choice’ external training. One CTC can be earned per 3 hours training, and DRs must accrue 100 CTCs across the three and a half years of their PhD.

Starting with a DNA to identify and support skills gaps, the project will develop the student’s subject knowledge in forest eco-physiology, Net Zero, and Nature-based Climate Solutions. Coding (data wrangling) and statistics skills will develop through handling remote-sensing and time-series data from disparate sources. Although primarily desk-based, experience of experimental work will be provided through participation in BIFoR FACE data collection, participation which will also provide experience and training in Health and safety in fieldwork. Networking skills will be developed through conference attendance, deepening towards the end of the project through participation in the organisation of conference sessions. Experience of a professional work environment will come through placement with the CASE body.

Partners and collaboration

This work has been re-approved for a CASE award 2025 and is directly aligned with the Met Office’s Research and Innovation strategy themes of “Capturing environmental complexity” and “Advancing observations”. Improved understanding of carbon cycle processes and their relation to net-zero policy are important for Met Office developments in land surface and Earth System modelling. Also, the use of bioclimatic datasets and indicators across multiple spatiotemporal scales helps understand interactions between climate variables and ecological processes, and the role of these processes on carbon sequestration in temperate forests.

Further details

 For any enquiries related to this project please contact A. R. MacKenzie, BIFoR, University of Birmingham, [email protected]. 

BIFoR FACE: https://www.birmingham.ac.uk/research/bifor/face/index.aspx

Met Office Climate Monitoring and Attribution: https://www.metoffice.gov.uk/research/climate/climate-monitoring/index

State of the UK Climate Phenology Supplement: https://www.metoffice.gov.uk/binaries/content/assets/metofficegovuk/pdf/weather/learn-about/uk-past-events/state-of-uk-climate/mo-phenology-supplement-v4.pdf

 To apply to this project: 

You must include a CENTA studentship application form, downloadable from: CENTA Studentship Application Form 2025.

You must include a CV with the names of at least two referees (preferably three) who can comment on your academic abilities.

Please submit your application and complete the host institution application process via: https://sits.bham.ac.uk/lpages/LES068.htm.   Please select the PhD Geography and Environmental Science (CENTA) 2025/26 Apply Now button. The CENTA Studentship Application Form 2025 and CV can be uploaded to the Application Information section of the online form.  Please quote 2025-B22 when completing the application form.

 Applications must be submitted by 23:59 GMT on Wednesday 8th January 2025.  

Possible timeline

Year 1

Literature review; refinement of research questions; identification of case studies; agree comparative study with Phenocam and FLUXNET communities; CENTA cohort-wide training; introduction to professional network; Paper 1: Phenology and Physiology of a temperate forest under 8 years of elevated CO2; progress report and committee.

Year 2

Targeted training as per DNA; extended placement at UK Met Office; poster/lightning talk at CENTA conference; poster at BIFoR Annual meeting; poster/oral at international conference; Paper 2: A review of interactions between phenology and physiology for forest ecosystems; comparative study utilising data from Phenocam network; Paper 3: Phenology and Physiology of temperate forests under climate change: comparisons across the Phenocam and FLUXNET networks; progress committee – submission of thesis plan.

Year 3

Second placement at UK Met Office; Engagement article in practitioner magazine/forum: Changing seasons in a changing world; longer talk at CENTA conference; talk at BIFoR Annual meeting; second international conference; Paper 4: Future changes in the phenological and physiological status of temperate forests assessed using IPCC CMIP6/7 model projections; thesis assembly – introductory and synthesis material; career orientation including engagement with professional practice; thesis submission and viva defence.