Biosphere Atmosphere Exchange 

Dr Tom Pugh leads the Biosphere-Atmosphere exchange group. His background is in computational modelling, particularly using global vegetation models. His research aims to improve understanding of the interactions between vegetation and environmental change at large scales. Tom is also the lead investigator on the TreeMort project.

Dr Adriane Esquivel Muelbert investigates how forests respond to different global change forces and what the implications of these responses are on biodiversity and global biogeochemical cycles. Her work demonstrates the importance of drought tolerance in shaping diversity and composition across Neotropical tree communities and provides evidence that Amazonian forests are changing as a result of the increase in water stress and atmospheric CO2. More recently, she has focused on tree mortality and how tree death varies across large geographical scales. In 2020, Adriane was winner of the Forests 2020 Young Investigator Award and lead for the successful International Tree Mortality Webinar series 

2020 was a busy year for the Biosphere-Atmosphere exchange group. Several major data compilation and processing activities were been completed, providing globally-unique data infrastructure to support research for many years to come. Specifically:

What predisposes individual trees to die? The first version of the TreeMort  global forest dynamics database has been completed. Dr Adriane Esquivel Muelbert  has compiled and standardised 23 million observations from 10 million trees from all corners of the world, coordinating with more than 350 contributors, this provides a unique window into the rates at which trees grow and die in the different forests of the world and is forming the basis for a range of new projects to understand forest function. 

What influences the rates of big forest disturbances? Nezha Acil has delineated and characterised more than 200 million individual disturbance patches across the World’s forests that occurred over 2002-2016, providing a basis for numerous investigations into the drivers and roles of these events in the unique structure of different forests. She presented a first biogeography of disturbance sizes at the American Geophysical Union (AGU) 2020 conference.

What strategies do trees adopt to withstand drought? Dr Daijun Liu has completed a dataset of functional traits related to drought tolerance for more than 10 000 tree species, enabling studies using empirical and modelling techniques that investigate how tree strategies vary across gradients of resources and stress. Results from this work are showing how the most successful hydraulic strategies of trees – and their diversity – vary across the world.

Articles in the Conversation and Birmingham Brief give some context as to the importance of these.

Alex Kulawska has completed and submitted for publication a synthesis of how boreal forests respond to thawing permafrost, proposing a new hypothesis framework to reconcile the conflicting results in the literature. She is now using dendroecological techniques to test some of these hypotheses. 

Lavinia Georgescu has put together a framework to investigate how satellite observations can be employed to assess how tree water content responds to drought at scales spanning whole continents and is carrying out a first analysis for the Amazon rainforest.

Hector Carmargo has reparameterised the LPJ-GUESS crop model to reproduce spatial and temporal patterns of major crop yields across the world and prepared a paper describing the evaluation of this model ready for submission. He is now moving on to parameterise a new ozone damage module for these crops.

Sijeh Asuk has discovered a surprising imprint of how human foraging appears to subtly alter the distributions of tree species in a tropical rainforest in Nigeria. He is now working to expand this analysis across the wider region and, despite the challenges of Coivd-19, is well advanced in a first field assessment of the fruiting phenology of trees that provide important community food sources.

Joe Wayman has completed two very substantial analyses of how the taxonomic and functional diversity of birds in the British Isles vary in space and in time, considering the roles of climate, land-use and topography. He is continuing his analyses of biodiversity-climate interactions, looking at a variety of sites across the tropics.

Nezha Acil and Dr Tom Pugh contributed to a critical response to a recent paper about forest harvest in Europe, which has been accepted for publication in Nature. Tom had a paper published in Biogeosciences exploring the reasons why global vegetation models differ so much in their future projections of carbon turnover. He also contributed to a review in Science of how climate and human influence is driving forests towards being both younger and shorter, a paper providing improved model descriptions of tree phenology and, together with Dr Daijun Liu, a new representation of leaf water potential for large-scale vegetation models.

Both Adriane and Tom have worked to expand the scope and activities of the International Tree Mortality Work, launching a new global seminar series on the topic of tree mortality (with over 300 participants for the first instalment) and questionnaires to assess the availability of data sources to characterise tree mortality across the world. The group said goodbye to Daijun in December, who left after 2.5 years to take up a fellowship in Vienna, but who will remain a close partner in the future. They also welcomed four new members. Julen Astigarraga joined the group as a “virtual” visiting PhD student from the University of Alcalá in Spain. He is using the forest inventory database to look at how tree demographic rates vary across their climatic distributions. Dr Susanne Suvanto joined the group on a 2-year Marie Curie fellowship (ForMMI) to investigate how real forest management vary across Europe and North America and link these to tree mortality. Klaske van Wijngaarden joined to start a PhD project joint with the University of Western Sydney in which she will investigate the contribution of loss of twigs and branches to the forest carbon balance – an often neglected component. Jordan Johnson began his PhD investigating how volcanic eruptions influence the forest dynamics in Chilean temperate forests.

Recent Publications

Esquivel-Muelbert, A. et al (2019) A Spatial and Temporal Risk Assessment of the Impacts of El Niño on the Tropical Forest Carbon Cycle: Theoretical Framework, Scenarios, and Implications. Atmosphere, 10, 588

Ogaya, R., Liu, D., et al (2020) Stem Mortality and Forest Dieback in a 20-Years Experimental Drought in a Mediterranean Holm Oak Forest. Frontiers in Forests and Global Change, 2(89). 

Pugh, T. A. M., et al (2019) Role of forest regrowth in global carbon sink dynamics. Proceedings of the National Academy of Sciences, 116(10), 4382-4387. 

Pugh, T. A. M., et al (2019) Important role of forest disturbances in the global biomass turnover and carbon sinks. Nature Geoscience, 12(9), 730-735.

Sullivan M.,  Lewis, S. L.; […] Esquivel-Muelbert, A.; […] Phillips, O. L. (2020) Long-term thermal sensitivity of Earth’s tropical forests. Science 368, 869-874

Zang, C. S.; Buras, A.; Esquivel-Muelbert, A.; Jump, A. S.; Rigling, A.; and Rammig A. (2020) Standardized Drought Indices in Ecological Research: Why one size does not fit all. Global Change Biology

Zohner C.,  Mo L.,   Pugh T.A.M., Bastin J., Crowther T., (2020) Interactive climate factors restrict future increases in spring productivity of temperate and boreal trees. Global Change Biology 25 (7)