Developing a trait-based framework for predicting soil microbial community response to extreme events

Climate change is already affecting the Earth's ecosystems. While most people think of increasing average temperatures when they think about climate change, recent years have shown us that even in the UK flooding and droughts are becoming more common, their effects devastating for many animals and plants. However, while the aboveground effects of these extreme weather events can clearly be seen, the carnage belowground remains hidden from our eyes. The soil is inhabited by millions of tiny creatures: a handful of soil can contain billions of bacterial cells, from tens of thousands of bacterial species, as well as hundreds of fungal species. The biomass of the microorganisms that live in the soil can even outweigh the biomass of the much larger animals that live on it! But these creatures are not immune to the consequences of drought and flooding. Especially bacteria don't cope very well with drought: they have semi-permeable cell walls and drought causes their cells to shrivel and die. After rewetting, they swell up and explode. Fungi, which perform many of the same functions as bacteria in the soil, are better able to cope with extreme drought than bacteria: they have stronger cell walls and are slower-growing than bacteria, which makes them more likely to resist stresses like drought. Flooding, in contrast, causes low oxygen conditions in the soil, which might be more favourable for bacteria, which are aquatic organisms, than for fungi. However, bacterial and fungal populations themselves consist of thousands of species, and these species might differ in their response to drought and flooding. But, we have very little idea of how bacterial and fungal populations are affected by these extreme weather events.

Although soil bacteria and fungi are hidden beneath our feet, they perform functions that are crucial for the functioning of the Earth's ecosystems: they decompose organic matter, thereby releasing nutrients for plant growth. These are the processes that support all ecosystems on land, including the agricultural systems that produce our food. However, when bacterial and fungal populations are affected by extreme weather events, so will the processes that they perform, and these changes in processes can in turn affect aboveground plants and animals. So, these unseen organisms have the potential to make the consequences of extreme weather events that we can see with our eyes even worse. However, at present, we don't know how we can predict how changes in bacterial and fungal populations will result in a change in the processes that they perform.

In this project, we will investigate how bacterial and fungal populations that live in the soil are affected by extreme weather events, and we aim to identify the traits that are responsible for this. For example, some groups of bacteria can form spores and thus survive a wide range of stresses, but there might be many other traits that can allow bacteria and fungi to cope with extreme weather events. We will use a unique experiment in which we subject soils from different climates across Europe not just to drought and flooding, but also to heatwave and freezing, and we will combine this with state-of-the-art DNA sequencing and bioinformatics to quantify bacterial and fungal response and to infer the traits responsible for this. In addition, we will measure how the processes that these organisms perform change with these extreme weather events. This work will result in fundamental knowledge on soil bacterial and fungal response to extreme weather events, and in a framework that allows us to predict how soils and their functioning will respond to extreme weather events. This knowledge is of the highest importance for adapting the Earth's ecosystems to climate change.

Who will benefit from the proposed research and how?

Scientific community:
Our project will deliver fundamental knowledge on the mechanisms though which extreme climatic events affect soil microbial communities and soil functioning, and build a predictive framework that will form the basis of future research into ecosystem response to climate change and impact on biogeochemical cycles. We will identify key microbial traits and genes that can predict microbial community response to extreme events. We will make this knowledge publicly available, in addition to engaging with the modelling community through a scientific workshop focussed on incorporating this knowledge into global biogeochemical models.
Importantly, this project creates a powerful network of collaborators and sampling sites across Europe. We aim to maximally involve all project partners and to foster a long-term network of collaborators and grassland sites, which will be of enormous value for future research.

Stakeholders and policymakers:
Our research has an immediate relevance for national (UK) and European policy. UK policymakers are showing a strong interest in identifying indicators of soil health and resilience, and monitoring these on a national scale. Our project will deliver a list of traits and taxa that informs on soil microbial community response to climate change and can thus be used as indicators of the vulnerability of soils and their functioning to climate change.
Local landowners and stakeholders that own or manage the grasslands sites used in this research will benefit from this research through gaining a greater understanding of how grassland functioning is affected by climate change.

The general public:
The general public will benefit from this research by being able to learn about different grasslands and local communities across Europe, as well as about soils and their importance for ecosystem functioning. The research will benefit UK and EU citizens by underpinning future policy for adaptation to, and mitigation of, climate change.

Staff working on the project:
All people involved in this project will benefit by being trained in this highly relevant and timely research area, by gaining transferrable skills that can be used in any employment sector, and by being part of a powerful international network of project partners. Any other PhD students working with the PI and co-Is will also benefit from ongoing work within the proposed project with opportunities to do add-on and linked experiments.