prof.dr.ir. L (Liesje) Mommer

prof.dr.ir. L (Liesje) Mommer

Persoonlijk hoogleraar

Mijn onderzoeksobject onttrekt zich normaliter aan ons oog: de plantenwortel en de omringende microorganismen zitten verstopt in de grond, maar sturen desalniettemin belangrijke processen in ecosystemen, zoals biomassaproductie en bodemvruchtbaarheid. We hebben aanwijzigingen dat plantensoorten in een soortenrijk grasland elkaar meer opjutten dan in een monocultuur, wat leidt tot een verhoogde groei ondergronds én bovengronds. Mijn doel is om de functionele interacties tussen plantenwortels onderling en hun samenspel met een legioen aan bodemorganismen te onderzoeken. Wat zijn de consequenties van deze ondergrondse 'intriges' voor coexistentie van plantensoorten? En hoe kunnen we deze ecologische inzichten toepassen om duurzamere landbouwsystemen te ontwerpen? Voor meer informatie, zie de engelstalige versie.

Playing hide and seek: the VIDI project

In 2015, I was awarded a personal VIDI Innovational Research grant to reveal the interplay between soil-borne pathogenic fungi, conspecific and heterospecific grassland plants in order to provide a mechanistic basis for the positive biodiversity effects and maintenance of coexistence. Together with the VIDI team members,- Eline Ampt and Davide Francioli -  I aim to reveal the functional interactions of the main fungal actors with plant roots by performing 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. This research will contribute to the fundamental understanding of plant-microbe rhizosphere processes, essential to maintain biodiversity and ecosystem functioning. We aim to provide proof-of-principle that the power of neighbouring plants can be used to reduce pesticide inputs in agriculture.

Root traits and biodiversity-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.

The development of a coherent root trait framework will allow a better prediction of plant community effects on ecosystem processes. The development of such an integrated framework will be particularly relevant for predicting effects of plant biodiversity on ecosystem functioning (BEF). There is consensus in BEF research that it is not plant species richness per se, but the value and range of functional traits of the species and their interactions that determine ecosystem functioning. Until now, the trait approach has only had limited success in BEF research. This may be due to the initial focus on aboveground traits, but also due to a lack of knowledge regarding the trait combinations driving ecosystem functions such as community producivity and nutrient cycling.

A recent success of this research theme is the PhD thesis of Lisette Bakker, which can be found here. Former lab members Monique Weemstra, Janneke Ravenek, Marloes Hendriks who also worked on different aspects of root traits in a biodiversity context.

Beyond my research team I have initiated the sROOT Initiative together with prof. dr. Alex Weigelt from University of Leipzig, Germany. This synthesisinitiative aims to understand root trait vatiation in whole-plant and ecosystem contexts.

Cover crops as a potential way to diversify agro-ecosystems

Cover crops are planted to maintain and improve the quality of probably the most precious asset in agriculture: healthy soils. These crops are currently widely applied to improve soil structure and prevent nutrient leaching. Next to these abiotic goals, cover crops have a major potential to lower the soil-borne disease pressure. The latter is a pressing issue as numerous pesticides that have been applied for decades to manage soil pathogens were banned recently. Particularly for the management of plant-parasitic nematodes and pathogenic fungi there is an urgent need for alternative measures, which may be provided by cover crops suppressing pathogens directly or indirectly via the stimulation of antagonists. However, the presence of multiple soil-borne diseases is commonplace, and a poorly-informed cover crop choice may even result in unintentional accumulation of one of these pathogens. Collborating with Sara Cazzaniga, Hans Helder and Joeke Postma and stakeholders we will provide a scientific basis for optimal cover crop combinations that suppress pathogens and boost soil biodiversity. .

Voor een korte video over mijn inauguratie, klik hier (Februari 2016)