Overview

Project Highlights:

  • State-of-the-art forest modelling for climate projection.
  • Substantial international networking opportunities.
  • Highly transferable computing skills.

Overview:

The world’s forest ecosystems provide or mediate many services to society, and to the planet, including removing huge amounts of CO2 from the atmosphere every year1, modifying the hydrological cycle, and fundamentally influencing the local climate.  Yet it is highly uncertain whether forests will continue to function as they do now under the changing environmental conditions projected for the coming century and beyond.

One crucial question is whether increased temperatures will lead to a large increase in drought-related mortality in trees. Such an outcome could transform the shape and function of global forests and release a huge amount of CO2 to the atmosphere.

The mechanisms by which trees dies from drought have long been controversial2, but recent evidence strongly indicates that hydraulic failure, i.e. a stress-induced inability to transport water through the plant, is a major cause3. There is evidence that trees may maximise their competitiveness by running very narrow safety margins with respect to drought, yet it is possible that the incredible diversity of tree species in some forests will prevent a wholesale forest die-off under climate change. This exciting doctoral project focuses on trying to answer the pressing question of whether future drought is likely to cause widespread global tree mortality. It will develop a treatment of drought mortality within a state-of-the-art global ecosystem model, and use this model to assess rates of tree mortality under environmental change, and the impact that such mortality has on ecosystem services such as global carbon storage. There will be the opportunity to work with field data from the BIFoR experimental woodland, and on international case studies. The modelling tool used forms part of a major Earth System Model, and thus there will be the potential for developments in this project to propagate directly into the results of major ecosystem and climate assessments, such as future assessment reports of the United Nations Intergovernmental Panel on Climate Change.

Research Questions:

  • Can a large-scale terrestrial ecosystem model simulate drought stress and mortality in present environments?
  • How does a more accurate model of drought mortality modify projections of biogeochemical and hydrological cycles, and thus global climate?

Objectives:

  • To improve representations of plant hydraulics & mortality within the dynamic global vegetation model LPJ-GUESS;
  • To evaluate the new model against existing mortality datasets and against detailed stress data from BIFoR FACE; and
  • To produce global estimates of the impact of drought mortality on the carbon, water, and nutrient (N, P) cycles.
Clockwise from top-left: schematic of leaf gas-exchange showing the fundamental connection between carbon assimilation and water loss; BIFoR research woodland Mill Haft; schematic of land surface model processes; and BIFoR FACE ring foundations at Mill Haft.

Methodology

This PhD connects to a major international modelling programme using the LPJ-GUESS global vegetation model, and the possibility to run this coupled to an Earth System Model. It is also integral to a major FACE programme investigating the response of mature forest ecosystems to elevated CO2.

Modelling: LPJ-GUESS is a world-leading model for simulating vegetation dynamics such as establishment, mortality, and plant succession, along with the resultant effects on biogeochemical and hydrological cycles. LPJ-GUESS also includes models of nitrogen cycling, fire, and anthropogenic management. The project initially requires the design of experiments for the current model, and then developments of the model code for subsequent steps.

Fieldwork: It is vitally important that modellers understand the strengths and weaknesses of the observational data they use to develop and challenge their models. The student will work alongside fieldwork researchers carrying out studies of the ecophysiology of mature woodland under climate change at BIFoR FACE, and be involved in the interpretation of results.

Training and Skills

The Doctoral Researcher will receive key training from the University of Birmingham in Earth system modelling, and associated visualisation systems. There will be close cooperation with researchers working at Mill Haft, and participation in interpreting BIFoR FACE data. The Doctoral Researcher will be supported to present their work at international conferences and publish their findings in high-impact journals. There will be the opportunity to attend selected modules from MSc courses taught within the School.

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. Training will progress from core skills sets to a bespoke set of master classes specific to the student's project. Attendance at the national Earth system modelling summer school will be obligatory and attendance at other relevant training schools will be strongly encouraged.   

Timeline

Year 1: Induction, literature review, simple initial model runs, CENTA training. Fieldwork shadowing. Study visit to Senckenburg Biodiversity and Climate Research Centre, Germany.

Year 2: Model development. International case study secondment.

Year 3: Final model runs, conference attendance, thesis and publication preparation.

Partners and collaboration (including CASE)

Supervisory team: Dr Tom Pugh is vegetation modeller with expertise in the LPJ-GUESS global vegetation model and EC-Earth Earth System Model; Dr Jeremy Pritchard is a plant scientist with experience in plant hydraulics; Prof Rob MacKenzie leads BIFoR.

Prof. Thomas Hickler will provide additional modelling training and advice on forest ecophysiology under climate change.

Further Details

The PhD studentship with be held at the University of Birmingham, linking strongly to the LPJ-GUESS teams at Lund University, Sweden, and Senckenburg Biodiversity and Climate Research Centre, Germany.