Soil Fauna MIND · Soil micro- and mesofauna as drivers of microbial necromass dynamics

Increasing soil carbon (C) sequestration is critical to mitigate climate change while supporting food security and reversing land degradation. Soil microbial necromass, i.e. dead microbes, has received increasing attention as significantly contributing to stable soil C. The microbiome itself is controlled by soil fauna, through two main trophic groups: microbivores, directly affecting its size and composition, and litter decomposers, modulating its access to resources. However, on-going environmental changes are altering trophic relationships and how this will impact microbial dynamics and C persistence is highly uncertain. My novel contribution to science will be to integrate soil micro- and mesofauna as a dynamic modulator of the soil microbiome, controlling microbial necromass and C persistence. To achieve this, I will manipulate soil micro- and mesofauna in microcosms experiments following two complimentary approaches, i.e., manipulation based on (1) size or (2) trophic classes. I will track the incorporation of 13C-labelled root litter into microbial biomass and necromass and compare microbial growth and carbon use efficiency, in the presence or absence of different soil faunal groups. After one year of incubation, I will measure C stability indicators (mineral-associated and occluded C, bulk δ15N) as well as newly formed microbial necromass to estimate soil C persistence. The experiment will be carried out at two different temperatures (ambient vs 5 °C increase) in a full factorial design to determine how the faunal control of the microbiome might change under future climate conditions. My MSCA project will shed light on the importance of soil fauna and trophic interactions for microbial necromass and soil C dynamics, a crucial approach in harnessing the potential for soil C sequestration and implementing effective management strategies.