YES-27-G-07: Tropical Forest Response to Climate Change

Predicting Tropical Forest Response to Climate Change (YES-27-G-07)

Tropical forests provide an array of globally important ecosystem services, including carbon uptake and storage, tropical climate regulation and biodiversity maintenance, all of which will be affected, potentially threatened, by climate change. However, predictions of how tropical forests will respond to climate change are highly uncertain.  Tropical forest stress caused by climate change includes an increase in vapour pressure deficit which may cause an increase in evaporative water loss, an increase in severity of droughts stressing tree water conductance system, increase of heat which may reach levels damaging plant organs. In contrast a beneficiary environmental change for plant functioning is the increase of atmospheric CO₂ while of course at the same time leading to the negative climate effects on tropical forests.

Plant hydraulics and water stress

Over recent years indicators related to tree hydraulics as well as limits of plant leaf functioning under heat have been developed and have been measured for a fairly large number of species in the tropics. Trees need to constantly water their crowns to avoid them to dry out, wilt and eventually die. They accomplish water transport in filamentous vessels by a pull from the crown against pull from the soil. The drier the soil and the higher temperatures the higher pull is needed to ‘pump’ water to the crown.

If the stress on the water filaments becomes too large they may turn into vapor. At this point vessels lose their capacity to conduct water. The point at which this happens is estimated by measuring so-called vulnerability curves, sigmoidal in shape, on tree branches. Similar vulnerability curves are measured on leaves to determine at what levels of temperatures and heat doses leaf photosystems disintegrate. The point at which 50% percent loss occurs is the primary indicator of failure. It differs among species.

Available datasets

Our group has measured / measures various datasets which should permit to evaluate a predictive model of how Amazon’s tropical forests will be affected by an increasingly warmer and erratic climate with both more severe droughts and floods. Moreover with funding from past and ongoing grants we have measured hydraulic and thermal traits and safety margins across a wide range of species and locations. These data complement many decades-long individual tree growth and mortality data at a widespread network of 1 ha forest plots. More recently we have furthermore started to measure continuously water potentials (pull) in soil and canopies, soil moisture profiles and sap flux in trees along a S-N transect in Southern Amazonia. Finally we maintain also an ongoing 1ha forest plot drought experiment in Southern Amazonia.

Besides these datasets we have developed an individual trait based model (TFS, trait-based forest simulator) which is tailored to analyse tropical forest dynamic at the 1ha spatial scale.

PhD project

The purpose of this PhD is first to enable the trait and individual forest plot simulator TFS with a hydraulics model designed to use the hydraulic vulnerability characteristics of trees which we are currently developing – and then evaluate the trait based simulator against observations.  The candidate will then use the model to simulate how climate change affects the tree hydraulic systems of trees in Amazonia across a wide range of observed growth strategies– both up to now and into the future. The project will also establish whether we can link model predictions of increasing stress on the tree hydraulic system to mortality patterns basin-wide.

The overall aim of the project is to obtain an improved understanding  how Amazon forests will respond to climate change.

 

 

Student profile

The project is suitable for a student with both strong biological / ecological  and math / computational background.

Supervision

The student will be co-supervised in Leeds by Prof. Emanuel Gloor (ecosystem modelling, tropical forest ecophysiology), Prof. David Galbraith (tropical forest ecophysiology, drought experiment)  and Prof. Oliver Phillips (tropical forest inventories, forest ecology).

The work will be in collaboration with Professors Beatriz Schwantes-Marimon and BenHur Marimon, University of Mato Grosso, Brazil.

Contact emails: Emanuel Gloor ([email protected]), David Galbraith ([email protected]), Oliver Phillips ([email protected])

 

References

Anderegg W. R. L., Berry J. A., Smith D. D., Sperry J. S., Anderegg L. D. L., Field C. B. (2012) The roles of hydraulic and carbon stress in a widespread climate-induced forest die-off. Proceedings of the National Academy of Sciences, USA 109, 233–237.

Jiménez-Muñoz, J. C., Mattar, C., Barichivich, J., Santamaría-Artigas, A., Takahashi, K., Malhi, Y., et al. (2016). Record-breaking warming and extreme drought in the Amazon rainforest during the course of El Niño 2015–2016. Sci. Rep. 6:33130. doi: 10.1038/srep33130

Sperry, J. S., Venturas, M. D., Anderegg, W. R., Mencuccini, M., Mackay, D. S., Wang, Y., Love,  D. M. (2017) Predicting stomatal responses to the environment from the optimization of photosynthetic gain and hydraulic cost. Plant, Cell & Environment 40, 816–830.

Fyllas, N. M.,  E. Gloor, L. M. Mercado, S. Sitch, C. A. Quesada, T. F. Domingues, D. R. Galbraith, A. Torre-Lezama, E. Vilanova, H. Ramírez-Angulo, N. Higuchi, D. A. Neill, M. Silveira, L. Ferreira, G. A. Aymard, Y. Malhi, O. L. Phillips, and J. Lloyd (2014) Analysing Amazonian forest productivity using a new individual and trait-based model (TFS v.1) Geosci. Model Dev., 7, 1251–1269, doi: 10.5194

Javad, A., Premugh, V., Tiwari, R., Bandaru, P., Sunny, R., Hegde, B.,  Clerici, S., Galbraith, D.,  Gloor, M.,  Barua, D. (2025), Leaf Temperatures in an Indian Tropical Forest Exceed Physiological Limits but Durations of Exposures Are Currently Not Sufficient to Cause Lasting Damage,  Global Change Biology, 31:e70069      https://doi.org/10.1111/gcb.70069

Esquivel-Muelbert, A. et al. Tree mode of death and mortality risk factors across Amazon forests (2020) Nat. Comm.11, Article number: 5515

Reis, S. M., Marimon, B. S., Esquivel-Muelbert et al. (2022). Climate and crown damage drive tree mortality in southern Amazonian edge forests. Journal of Ecology, 110, 876–888. https://doi.org/10.1111/1365-2745.13849

van Tiel, N. G. Lenczner, M.P. Rao, C. Grossiord, & D. Tuia, Tropical forests are facing increasing risks of exposure to critical temperature thresholds, Proc. Natl. Acad. Sci. U.S.A. 123 (28) e2528622123, https://doi.org/10.1073/pnas.2528622123 (2026).

Tavares, J.V., et al., Basin-wide variation in tree hydraulic safety margins predicts the carbon balance of Amazon forests (2023) Nature, 617, 111-117. ISSN 0028-0836