prof.dr.ir. L (Liesje) Mommer

Biodiversity in research and for society

My scientific mission is to elucidate how biodiversity affects ecosystem functioning. My research focuses on interactions between plant roots and soil-borne fungi at the community level and has contributed to paradigm shifts in the understanding of resource complementarity and functional trait ecology in grassland systems. Currently I focus on understanding the mechanisms underpinning the biodiversity effects on belowground disease risk. Overcoming this gap is essential for transforming agricultural systems from monocultures that are sensitive to disease outbreaks to diverse cropping systems that are intrinsically resilient to pathogens. The importance of my work is evidenced by the fact that I am recognised as a highly cited scientist (i.e. belonging to top 1% best cited scientists of the world) in 2021 and 2022.  

Nearly two decades of scientific research have convinced me that biodiversity is a safety net for our planet. However, biodiversity loss is unprecedented and threatening the planet, ecosystems and people. This is why I initiated and lead the Wageningen Biodiversity Initiative (WBI). In this capacity, I develop and lead research programmes related to biodiversity in the food system and nature-inclusive society, 2) guide policy making by synthesising scientific insights and discuss these with policymakers and politicians (e.g. the European soil health law https://www.wur.nl/en/dossiers/file/soil-health-2.htm); and 3) speak to the media to create public awareness around the importance of biodiversity for planetary and human health (see picture: speaking about biodiversity on national TV).

Nov 2023: New paper out in New Phytologist: Fungal communities relate to the Root Economic Space

Recent work from my team has shown that there are two axes explaining variation in root traits: the collaboration axis with mycorrhizal partners and the conservation (‘fast–slow’) axis (Bergmann et al, 2020). However, it was unknown to what extent these trait axes affect the assembly of soilborne fungi. In this study we sequenced rhizosphere fungal communities and measured root traits in monocultures of 25 grassland plant species, differing in age. Within the fungal guilds, we evaluated fungal species richness, relative abundance and community composition. Fungal diversity and relative abundance were not strongly related to the root trait axes. However, saprotrophic fungal community composition was affected by the conservation gradient and pathogenic community composition by the collaboration gradient. This new paper gives a first insight into the structuring role of root traits for fungal community composition. With @Justus Hennecke and @Alex Weigelt, #UniLeipzig

The collaborative role of root traits in ecosystem functioning 

Plant roots perform multiple functions, including plant anchorage and belowground resource uptake, especially nitrogen, phosphorus and water. They have evolved a wide range of root traits to simultaneously perform these functions, which respond to spatial and temporal changes in soil properties and resource availabilities. Variation in root traits also implies large impacts on soil and ecosystem functions. However, despite the exponential interest towards root ecology, the connections of root traits to plant and ecosystem functioning remain poorly understood.

Because of this knowledge gap in ecology, I have - together with prof. dr. Alex Weigelt from University of Leipzig, Germany - initiated and led the international sROOT and RootFun workgroups. We have been enjoying working together - online and in person - in a series of collaborative efforts to understand root trait vatiation in whole-plant and ecosystem contexts.

We demonstrated that root trait data from 1810 species across the globe confirm a classical fast-slow “conservation” gradient as frequently found for leaves. Importantly, however, we showed that most variation is explained by an orthogonal “collaboration” gradient, ranging from “do-it-yourself” resource uptake to “outsourcing” of resource uptake to mycorrhizal fungi. Plants thus show us that things have not to be done alone, but that 'doing things together' can be a succesful strategy in life! This broadened “root economics space” provides a solid foundation for predictive understanding of belowground responses to changing environmental conditions.

Do you want to work with root traits yourself? Check out the GRoot root database! We made root trait data accessible for non-experts.

Are you interested in our findings? Check out our high-impact papers:  Bergmann et al 2020 Science Advances; Laughlin, Mommer et al, 2021 Nature Ecol Evol; Weigelt, Mommer et al 2021 New Phytologists, and more in the pipeline! 

Picture: Artwork by (C)Colleen Iversen showing the spirit of sROOT: Collaborate! Image of the turtles are  inspired by the game Dodelido, as playing games was a fun and connecting asset of the working group.

June 2023: Update in Nature about the Root Economics Space

Two recent publications1,2 have explored the importance of roots for understanding plant form and function, but reached opposite conclusions on the basis of largely overlapping data. Carmona et al.1 concluded that their results “do not confirm the strong covariation between leaf and fine-root traits predicted by the plant economics spectrum hypothesis”. By contrast, Weigelt, Mommer et al.2 concluded that “key leaf and fine-root traits were aligned along the expected [fast–slow] ‘conservation’ gradient of plant economic investment”. In a new reflection paper by Weigelt, Mommer et al in Nature the sROOT team reflects on the causes for the apparent discrepancies of these studies. Take home message: What you put in, determines what you get out: rationale behind trait selection is vital for the conclusions.

Weigelt, A., Mommer, L., Andraczek, K. et al. The importance of trait selection in ecology. Nature 618, E29–E30 (2023). https://doi.org/10.1038/s41586-023-06148-8

November 2022: Meeting Merlin Sheldrake - Lessons from fungi for leading change 

In 2022 Merlin Sheldrake was awarded the Groeneveldprijs for his incredibly beautiful book about the fungal world 'Entangled Life'. I was offered the honor to deliver the Groeneveld lecture. I spoke about how working with soil-borne fungi has changed my way of being and leading for change. Read the whole lecture here. The beautiful mycelium on the slide is excellent artwork by Suzette Bousema.

October 18th 2022: PhD defense Eline Ampt

Biodiversity can reduce or increase disease transmission. These divergent effects suggest that community composition rather than diversity per se determines disease transmission. In natural plant communities, little is known about the functional roles of neighbouring plant species in belowground disease transmission. 

In her PhD thesis, Eline focussed on  the belowground interactions of a plant community and a unbiquitous pathogenic actor:  the soil-borne fungus Rhizoctonia solani. Eline investigated the transmission of this pathogen on community composition. Neighbouring plants either reduced or increased disease transmission in host plants. Her work shows that neighbour-induced shifts in the importance of these mechanisms across root networks either make or break disease transmission chains. Some neighbours are nice, others you better avoid. Plants are just like people ;)

Understanding how diversity affects disease transmission requires integrating interactions between host, neighbouring species and their pathogens in a given environmental setting. Future work will need to reveal what plant traits and interactions with other soil microbes affect this biodiversity-disease relationship.

Three papers have been publised already, in European Journal of Plant Pathology, New Phytologist and Journal of Ecology. she has been awarded the Hugo de Vries award of the best botanical thesis in the Netherlands of 2022. 

Playing hide and seek: the VIDI project

In 2015, I was awarded a personal NWO-VIDI Innovational Research grant to reveal the interplay between soil-borne pathogenic fungi, conspecific and heterospecific grassland plants in order to reveal the role of soil-borne pathogens in regulating the positive biodiversity effects and maintenance of coexistence. Together with the VIDI team members,- Eline Ampt, Sofia Fernandes Gomes, Jose Macia Vicente (and in the past also Davide Francioli),  I aim to reveal the functional interactions of the main soi-borne fungal pathogens driving the biodiversity effect in grasslands. My team and I perform 1) community assembly studies with both fungal and plant communities in order to test host-specificity 2) focus-expansion experiments with plant monocultures and mixtures to study density-dependence and neighbour effects. The insights obtained from these controlled experiments will be tested at larger spatial scales and over longer time scales, in more natural settings. 

To reveal these ‘hidden’ interactions and the consequences for ecosystem functioning, I and my team integrates insights from plant ecology, molecular biology, soil chemistry and phytopathology. My mission is to translate the ecological insights from these biodiversity experiments to diversify agricultural ecosystems, as I described in this blog https://jecologyblog.com/2018/03/05/liesje-mommer/.