The story behind the article: Climate change impacts on below-ground communities

Free‐air carbon dioxide enrichment (FACE) experiments have dramatically increased our understanding of how plants may respond to future climate change scenarios. These experiments also provide unique opportunities to better predict how below-ground symbiont communities, crucial to plant health, may respond to climate change. Dr Irena Maček and Prof. Alex Dumbrell give us their behind the scenes insights into their paper that combines Illumina HiSeq sequencing and one of the longest running FACE experiment to find novel insights into mycorrhizal fungi communities and climate change.

Check out the full study here.

The Giessen FACE experimental setup. Photo courtesy of Irena Macek

What led to your interest in this topic / what was the motivation for this study?

Arbuscular mycorrhizal (AM) fungi form mutualistic associations with over two‐thirds of plant species, providing numerous benefits in exchange for carbon. Importantly, different AM fungi provide different plant species with different resources. Thus changes to AM fungal communities can alter plant competition and above-ground productivity. This functional differentiation has motivated both of us to explore the ecological mechanisms regulating AM fungal communities, and it was apparent there was a lack of knowledge on how AM fungal communities respond to elevated atmospheric CO2. This is a major research gap, as AM fungi are entirely dependent on their hosts for carbon and changes in photosynthesis in a high CO2 world may influence this. Thus the chance to sample plant roots from one of the longest running free‐air carbon dioxide enrichment (FACE) experiment in the northern hemisphere in Giessen (Gi-FACE) was an excellent opportunity to address this gap in global climate-change research.

What difficulties did you run into along the way? 

Long-term FACE experiments in natural ecosystems are extremely rare, because such set-ups demand stable funding and the persistence of several generations of highly motivated researchers. This would have been a far greater current problem if Prof. Christoph Müller (Justus‐Liebig University Giessen) and his group had not continuously addressed these difficulties since the Gi-FACE experiment’s inception. Another difficulty that we are increasingly finding in metabarcoding research is how to present often extensive and complex data. Dr Dave Clark (University of Essex) was central in working on innovative ways to address this challenge and moving beyond coarse summaries of total community change.

What is the biggest or most surprising innovation highlighted in this study? 

For the first time, we have combined a long-term FACE experiment in a natural habitat with high-throughput molecular sequencing (Illumina HiSeq) and new ways of presenting community data. This has allowed us to see subtle population-level responses within broader community-level responses of AM fungi to elevated atmospheric CO2 across the course of a year.

Moving forward, what are the next steps in this area of research?

Understanding the impacts of global-climate change on terrestrial ecosystems requires an integrative approach that explores responses across all levels of biological organisation and spatiotemporal scales, both above- and below- ground. We still lack a comprehensive understanding about how interactions between the above- and below- ground components of biodiversity respond to both acute short-term (e.g. episodic heatwaves, drought etc.) and chronic longer-term climate changes (e.g. warming, elevated CO2). New experiments aimed at addressing these knowledge gaps with robust levels of replication and appropriate experimental durations for capturing longer or shorter-term responses are required, and these must allow for combined sampling of above- and below- ground biota.

Plant root with arbuscular mycorrhizal fungal structures (hyphae and arbuscules). Photo courtesy of Irena Macek

What would your message be for students about to start developing or using novel techniques in Molecular Ecology? 

The same as our message for all earlier career researchers – identify your research question, read around your research area, develop your hypotheses and plan an appropriate study to address them, and then choose the correct tools/techniques to conduct the research with. The novel techniques can have a lot of analytical power but can also produce a lot of erroneous data due to the rapid development, a lack of testing and a lack of experience. It is very important to initiate the study with clear questions resulting in hypotheses driven research. Do invest time in skills of data analyses and bioinformatics from the very beginning as there is never enough time to do that the later you are in a career, the more difficult it gets with many other obligations.

What have you learned about methods and resources development over the course of this project? 

The field of molecular ecology continuously develops at a rapid pace. It is crucial to have a good network of people with a multidisciplinary range of expertise to collaborate with and to capitalise on all these new and often varied developments. Essentially, good collaboration is crucial. It should also be fun, which is always a good recipe for it to be sustainable and develop into a long-term connection.

Describe the significance of this research for the general scientific community in one sentence.

Elevated levels of atmospheric CO2,reflective of those we will experience in the next ~100yrs, drive changes in symbiotic AM fungal populations with the potential to resonate throughout their associated plant communities, changing above-ground competition dynamics and ecosystem productivity in currently unpredictable ways.

Describe the significance of this research for your scientific community in one sentence.

Predictions regarding future terrestrial ecosystems must consider changes both above-ground and below-ground, but avoid relying on broad‐scale community‐level responses of soil microbes observed on single occasions.

Citation: Maček, I, Clark, DR, Šibanc, N, et al. Impacts of long‐term elevated atmospheric CO2 concentrations on communities of arbuscular mycorrhizal fungi. Mol Ecol. 2019; 28: 3445– 3458.

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