Last week I attended the 2-day New Phytologist symposium on ‘Above- and below-ground Biodiversity for Sustainable Ecosystems‘ that was organised by Associate Editor Marcel Van Der Heijden at Agroscope (Reckenholz, Switzerland) on behalf of the BiodivERsA “#DiggingDeeper” project.

I personally loved the symposium, not only because of the great line-up of speakers and because it was a perfect opportunity to catch up with friends and meet new ones, but also because of the great science directed toward improving the sustainability of agroecosystems. The symposium covered various topics, including plant and soil biodiversity impacts on ecosystem functioning and multifunctionality and, of course, the threat of global changes.

Senior Editor Richard Bardgett (University of Manchester) kicked off the symposium with some insights into the resilience of soil microbial communities to drought. This talk also highlighted the current lack of knowledge on how microbes respond to long term climate perturbations (e.g., drying/rewetting). Associate Editor Franciska De Vries (University of Amsterdam) added that root traits can have strong implications in microbial community responses to drought, emphasising the importance of considering plant-soil interactions in climate change research. Jonathan Bennett (University of Saskatchewan) also showed that soil biodiversity can mediate resistance to various types of disturbance in grasslands.

Klaus Birkhofer from the Brandenburg University of Technology highlighted that more knowledge is needed on how climate change will impact agricultural systems and provided insights on how to manipulate drought in agroecosystems. A bit later in the meeting, Nico Eisenhauer from Leipzig University added that it is important to consider both land-use and climate change in agricultural systems and presented some results on soil organisms and processes responses.

A strong focus of the meeting was on the role of biodiversity on ecosystem functioning. Peter de Ruiter from University of Amsterdam gave an interesting introductory talk on the topic entitled ‘Why are there so many species in earth?’ This highlighted the fact that all species within a species-rich community don’t all interact constantly together, which is not really considered in current models. Gaètane Le Provost from the Senckenberg Biodiversity and Climate Research Centre and Biodiversity Exploratories project emphasised the importance of landscape diversity, which forms vital part of ecosystem services provided at the plot level (i.e., role of the surroundings). ‘Diverse forests store more carbon and support larger trees’ was the message of Bernhard Schmid (University of Zurich) who showed his work on the BEF China experiment (for more details, take a look at this recent video podcast). Finally, Fernando Maestre from University of Alicante presented the large amount of work and findings from his team on biodiversity effects on multifunctionality of global drylands.

Biodiversity is not only species richness. Functional attributes are also important and this is what our Associate Editor Eric Allan (University of Bern) is currently testing in grasslands, through an impressive multifactorial experiment (PaNDiv experiment) which combines different levels of diversity, functional trait attributes (fast and slow growing species), nitrogen enrichment and fungal leaf pathogen exclusion. Initial results show that nitrogen addition cancels the positive relationship between functional diversity and ecosystem multifunctionality. Eric’s talk was followed by Tom Crowther from ETH Zurich who demonstrated through a large scale experiment that the competitive ability of saprophytic fungal species is related to their environmental tolerance. Florine Degrune from Freie Universität Berlin and the Digging Deeper project ended the first day of the meeting by highlighting regional and local drivers of soil protists.

The second day of the symposium was dedicated to the role of biodiversity on agricultural sustainability and started with Claire Chenu (AgroParisTech/INRA) who just received the 2019 INRA Lifetime Achievement Award (Prix de la Recherche Agronomique 2019, France). Claire highlighted some very interesting results on how to improve carbon storage through agroforestry. Matthias Suter from Agroscope also showed that increasing plant diversity in sown grasslands can strongly enhance multifunctionality. From the Digging Deeper project: Gina Garland demonstrated that cover crop duration, rather than diversity, is key for sustainable intensification of European agroecosystems, Sara Hallin highlighted that diversification of agriculture supports multiple ecosystem services and Aurélien Saghai showed that changes in plant or soil diversity can condition N2O emissions by affecting plant microbiome selection. Laurent Philippot from INRA asserted that plants are not passive straws and that they play an important role in nitrogen cycling in agroecosystems. An interesting talk from Matthias Rillig (Freie Universität Berlin) highlighted the importance of interacting global change factors on soils. In this experiment, Matthias and collaborators tested 10 drivers of global change both individually and in combination, at levels ranging from 2 to 10 factors and showed increasing effects when factors were combined.

Each session was followed by a panel discussion with the audience, which yielded interesting debates on how to apply fundamental research in agricultural systems. In the audience, Elena Havlicek (Swiss Federal Office of the Environment, Soil Section) asked the tough but very relevant question: how can research results be used to scheme new agricultural policies? What is the most important factor? Claire Chenu and other panel members agreed that maintaining plant cover across all lands was one of the top priorities – bare soil cannot maintain or promote ecosystem functions and services.

Eva Reinhard, Head of Agroscope, presented some examples on how biodiversity has been included in Swiss policies and it was quite impressive! Switzerland’s agri-environmental policy has included cross-compliance and Ecological Compensation Areas (ECA) since 1998! Biodiversity has been monitored extensively at the national scale, but also more intensively across agricultural areas. Eva’s talk was follow by Urs Niggli, Director of the Research Institute of Organic Agriculture (FiBL Switzerland) who discussed the trade-off between agricultural productivity and ecosystem services and the need for innovations to redesign farming systems for the future.

The meeting continued with Ian Sanders from University of Lausanne, with real solutions to increase food production using arbuscular mycorrhizal fungi (AMF). Indeed, Ian showed that by inoculating cassava (Manihot esculenta) with the right AMF genotype, it is possible to improve yield up to 30 tons per hectare while rapidly increasing soil aggregation and reducing carbon release. Considering that the current average yield for cassava is 12 tons per hectares, this is a major innovation for the development of agriculture in countries where cassava is the main food source (Africa, South America). Cassava currently feeds 2 billions people per day! The method still requires some adjustments but this was my favourite talk of the meeting because it was focused on solutions and provided some hope for improving both agricultural sustainability and productivity.

Then, Maarja Öpik from University of Tartu (Estonia) presented results from another BiodivERsA project: SoilMan. Maarja highlighted how AMF respond to management practices and the potential to use AMF for vegetation restoration. On the same topic, Jasper Wubs from ETH Zurich presented his work on whole-soil microbiome inoculation to target the restoration of particular vegetation types. Associate Editor Marcel Van Der Heijden from Agroscope ended this series of talks by showing the impacts of different agricultural practices on soil biodiversity and how we can use knowledge on soil biota to improve sustainability of agricultural systems.

In my opinion, the meeting was a success and started constructive and timely discussions on how to improve our understanding of plant-soil interactions (e.g., long-term responses), global changes (e.g., multiple interacting factors) and biodiversity effects on multifunctionality. The meeting also provided guidance on how to transfer knowledge into real agricultural solutions and policies. Let’s hope research continues in this direction, with a focus on finding solutions to worldwide problems!

Pierre Mariotte, Associate Editor of Journal of Ecology, Agroscope, Nyon, Switzerland

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On the same topic, have a look at the Special Feature ‘Ecological Solutions to Global Food Security’ published in the Journal of Ecology.