The Amazon is the most important biome of South America, harbouring extraordinarily high levels of biodiversity and providing important ecosystems services. This biome is particularly notable for evolving independently from fire and in a moist, warm climate. In recent decades, altered fire regimes and an increasingly hotter and drier climate has pushed this key biome towards ecological thresholds that will likely lead to major losses in biodiversity and ecosystem services. Similarly, the ecotonal forests at the Amazon-Cerrado transition are unique ecosystems in terms of form and function, but they may be the first to suffer large-scale tree mortality and species loss due to the combined effects of increased anthropogenic disturbance, altered fire regimes and a drier climate.
Vulnerability of fire and droughts are closely intertwined in Amazonian and transitional forests because fires in this region only occur when there is water stress and a human ignition source. Thus, drought increases vulnerability to fire, but we do not yet understand the magnitude and spatial variation of these vulnerabilities. Once a forest burns there is immediate tree mortality, but recent evidence also shows a significant time-lagged mortality that can last for decades, becoming an important carbon source. However, the mechanistic processes that lead to time-lagged tree mortality in this myriad of forest ecosystems encompassing the Amazon biome and the Amazon-Cerrado transition are still poorly understood. We also lack knowledge on how these processes might vary spatially across the biome and its transition. A better understanding of the mechanisms that lead to tree mortality after fires and droughts is needed to design future policies that emphasise nature-based solutions including restoration and natural regeneration.
This project uses aims at deciphering the mechanisms that underly vulnerability to fire and time-lagged post-fire mortality across the tropical forests in Amazon and Amazon-Cerrado transition. To achieve this aim, we quantify fire vulnerability at three different scales and link them through an upscaling approach. First, we identify the ecological mechanisms that explain why individuals and species die after fires occur. Second, at the community scale, we examine how vegetation structure, community traits and microclimate affect the probability to burn. Third, we predict the vulnerability of the Amazon forests and Amazon-Cerrado transitional forests. This information will be directly applicable for the detection of sensitive hotspots (areas particularly vulnerable to fire) through satellite products. We will deliver quantifiable early-warning metrics of ecosystem vulnerability to fire that can be mapped and incorporated into fire management policies.

This project is led by Dr. Imma Oliveras Menor (U.Oxford, IRD), with Manoela Machado as postdoctoral research assistant (U. Oxford, Woods Hole Climatic Research Centre) , Prof Jos Barlow (U. Lancaster) and Prof Yadvinder Malhi (U. Oxford) as co-investigators, and eight other partner institutions from Brazil, US and UK

Building on a
unique dataset across the Neotropics and Palaeotropics, we will perform an in-depth analysis to decipher o the
role of evolutionary factors on plant community composition and ecosystem net primary productivity. This
information will help on predicting the vulnerability of tropical ecosystems to global change. It will also allow to
identify taxonomic clades that may be most resilient to changes in climate and disturbance regimes, with
potential for informing future restoration practices in the tropics. With 2021 being the first year for the UN
decade of restoration, this study will provide novel and timely knowledge to help restoring degraded or altered
tropical forest ecosystems with suitable native species. THe project is co-led by Dr Imma Oliveras Menor and Dr Claire Fortunel.

Understanding the thresholds for plant water use and water use efficiency (WUE) across tropical transition zones is critical for predicting how these key regions, which are high in biodiversity and provide significant ecosystem services, may respond to climate change. A primary goal of ECOSTRESS is to reduce the uncertainty in estimates of water use and WUE; when combined with ground-based data, this information can provide both a means of validation and an unprecedented opportunity to test novel hypotheses that provide predictive insights.
We will leverage a large and unique existing leaf trait (morphology, photosynthesis, albedo, chemistry, and stable isotopes) dataset from species sampled 1-ha plots in the ECOSTRESS ‘hotspots’ of transition zones of Ghana and Brazil. Because we collected samples from all of the species in each plot that composed 80% of the stand basal area, we are able to compare ECOSTRESS pixels to similarly sized plot-level community weighted means of water use efficiency and canopy temperature dericed from gas exchange measurements and leaf isotopes. We will establish the level of agreement between ECOSTRESS and field data in order to provide a measure of accuracy for ECOSTRESS data. In doing so, we will provide critical insights into how plant WUE and leaf temperature vary across tropical transition zones and test the extent to which there is evidence for thresholds associated with vegetation characteristics.


The team: this research is led by Dr Chris Doughty (NAU) and Dr Greg Goldsmith (Chapman University). Our research team has >10 years expertise working in these transition zones (Co-Is Oliveras and Malhi), extensive knowledge of ECOSTRESS (Co-I Fisher – ECOSTRESS science PI), and expertise in the field, remote sensed, and modeling methods.

Wildfires have become the new norm in many parts of the Amazonian humid forest, an ecosystem
that did not co-evolve with this stressor. Large areas of previously undisturbed and human-modified
forests are catching fire, jeopardizing the future of the largest and most biodiverse tropical rainforest
in the world. Despite the growing prevalence of Amazonian wildfires, we still have a very limited
understanding of why these low intensity understorey fires cause very high rates of tree mortality,
which species functional traits predict vulnerability or survival to these fires, what are the impacts of
wildfires on the forest carbon balance and what are the patterns of taxonomic and functional recovery
following a fire event. We propose a research plan to achieve major advances in our understanding
of such wildfire impacts, including of the underlying mechanisms that cause both short-term and
longer-term tree mortality. We will achieve this by combining a state-of-the-art forest burn experiment
with continued monitoring of a unique set of long-term sampling plots, some of which we have
tracked through a 2015-16 wildfire event associated with a strong El Niño. We are uniquely placed
to address these fundamental questions given our network of burned and unburned forest plots that
is already in place, and the numerous past datasets that we can use as baseline information. As well
as advancing scientific knowledge about a pervasive and increasing threat to the future of tropical
forests in the Anthropocene, our co-designed pathways to impact ensures we will also inform and
improve approaches to minimise risk of fire-induced dieback of humid Amazonian forests.
This project is led by Prof. Yavinder Malhi and Prof. Jos Barlow, Co-I Erika Berenguer and Co-I Imma Oliveras