The aim of this project is to determine the ecological relationship between bacteria and soil aggregates. We inoculate individual beneficial bacteria and different microbial communities from different natural soils in simulated Mars soil, attempting to explain their improvement in soil aggregate stability by bacterial exudates (EPS), necromass and microbial functional traits.

Sufficient Phosphorus (P) and Iron (Fe) supply is essential for crop production. Most of the P and Fe in soil is not readily available for the plant, making agriculture depending on inorganic fertilizers mainly derived from depletable resources. An alternative to this unsustainable practice is to use recycled compounds recovered during wastewater treatment. This project focuses on the use of the two recycled compounds struvite (MgNH4PO4·6H2O) and vivianite (Fe3(PO4)2·8H2O) which are both insoluble and hard to synchronize with the nutrient needs during early plant development. To increase efficient nutrient release of these recycled sources, we propose the use of microbes that can solubilize P and release siderophore, both recognized traits of plant growth promoting microbes. Several plant growth-promoting microbes have been isolated, but their transfer to agriculture, so far, resulted in an inconsistent success, due to competition or resistance of the resident soil microbiome to inoculants. This project will circumvent this challenge by steering the local microbiome with the addition of recycled nutrients and will further optimize the microbiome by microbial community breeding. Overall, this project will focus on identifying microbial community members with struvite and vivianite solubilizing function, optimizing these communities, determining the role of these communities on increasing the nutrient release as well as monitoring the recruitment of these beneficial microbes in the rhizosphere and the effect on plant growth.

The Maasheggen area is a unique cultivated landscape in the Netherlands (near Boxmeer, province Noord-Brabant) and has been designated as a UNESCO biosphere reserve (https://www.maasheggenunesco.com/en/). Its mosaic of hedgerows, small arable fields and meadows make this a very interesting area to study the effects of land use and landscape elements on functional biodiversity and ecosystem services.

SPI-Birds Network and Database (www.spibirds.org) is a centralized and community-driven initiative that connects researchers working on wild bird populations in which individuals are uniquely marked and recognized. SPI-Birds makes research groups and their datasets visible, provides systematic data archiving, ensures data quality and integrity, and facilitates data sharing and comparative, cross-dataset analyses. For this purpose, we have developed a data standard and series of data quality checks agreed upon by the community, which adhere to the FAIR principles.

Understanding carbon cycling in soils is of vital importance, because it determines soil-climate feedbacks via balance of carbon between the soil and the atmosphere, as well as soil health. Soil communities play a key role in driving soil carbon cycling. Soil organisms degrade organic matter, which drives emissions to the atmosphere. At the same time they use carbon for their own growth and thereby determine the amount of carbon retained in soils and microbial biomass. Higher trophic levels of soil organisms may modify the activity and performance of soil microorganisms by feeding on them, as well as by changing abiotic conditions in the soil. As a result, they can strongly impact the role of microorganisms in driving carbon cycling and storage. How soil communities and trophic interactions between soil organisms drive carbon losses and gains in soils is still poorly understood. Therefore in my group, we focus on how soil communities drive soil carbon cycling. We pay specific attention to relationships between litter and decomposer communities in driving soil carbon cycling and to the role of higher trophic levels in modifying rates of carbon cycling. This is work is carried out in close collaboration with the Lejoly group.