Understanding and predicting sensitivity of Amazonia’s forests to increasing heat and drought

Tropical forests fulfil important roles both for climate and biodiversity. They are exposed to a range of pressures including an increasingly hotter and erratic climate as well as changing atmospheric composition (particularly CO2 and N2O levels raising) (Lapola et al., 2023). In the Amazon there is clear evidence not only of temperatures increasing but also of shifts in the hydrological cycle, with dry season length and seasonal amplitude of precipitation increasing. How these forests will be affected on a long-term is unclear. To observe and understand mechanistically what changes these forests are undergoing and whether limits of functioning may be reached, members our group maintain an widespread pan-tropical forest census network. In addition our group has measured tropical tree traits characterizing mechanistically tree vulnerability to heat and drought. It is starting a drought experiment in Southern Amazonia this summer, the region where temperatures have increased most rapidly.

The traits like e.g. species-specific vulnerability of the tree hydraulic system to drought and atmospheric vapor pressure deficit open the possibility to analyse demographic changes of these forests with a mechanistic individual based forest simulator (specifically TFS ‘trait-based forest simulator). In turn such a model can be used to explore future forest trajectories. The model we would like the student to use (TFS) is tailored to model and analyse forest plot census data over time. It parametrizes forests using traits and includes a mechanistic description of tree hydraulics and hydraulic failure using observed vulnerability curves.

The purpose of the studentship is to apply the model to Amazonian forest demographics data (from forest census plots) using characteristics of the vulnerability of tree hydraulic systems to drought. Specific questions and tasks will include to answer to what extent overreaching limits of functioning of tree hydraulic system can predict mortality risk, to then predict mortality risk maps as a function of dry anomalies across the Amazon, and similarly for thermal limits, and eventually to predict tree functional shifts as a result of a changing climate.

The PhD post is part of the UKRI funded consortium project SOS-Amazon which has just started. Thus the candidate will have the opportunity to participate in regularly occurring meetings of the full consortium. As part of this project annual forest censuses along a South to north gradient in Southern Amazonia will be measured, as well as a continuously climate and soil state. The candidate will have the possibility to join / co-lead these efforts.

The PhD links also to a second UKRI grant (LethalPsi) led by Prof. David Galbraith. It studies limits of functioning of forest trees under drought using a drought experiment in Southern Amazonia. This project has also just started. There will be the possibility to apply the model to this experiment and use it as a calibration / test case.

Applicants to this scholarship in the School of Geography should have a keen interest in questions related to the natural environment and climate change. They should have strong quantitative abilities and skills and in particular a flair for applying computer models to natural problems. Backgrounds in fields like biology, environmental science and engineering, computational mathematics and physics are all well-suited. 

For entry requirements and information on how to apply, please see the project page on the University of Leeds website.

For questions please contact either Prof. E. Gloor ([email protected]) and/or Prof. D. Galbraith ([email protected]).

Applicant conditions:

• Applicants must not have already been awarded or be currently studying for a doctoral degree.
• The Applicant should start as soon as possible ideally before June 2024.
• Applicants must live within a reasonable distance of the University of Leeds whilst in receipt of this scholarship.