Ecosystem response to drought: unravelling the unexplored role of plant-soil feedback

ended

Drought is severely threatening our ecosystems and their functioning: it causes strong shifts in plant community composition that are difficult to revert. Positive feedbacks often underlie these dramatic shifts, but in many ecosystems drought causes fast-growing species to increase. These species are not only vulnerable to drought, but they also suffer negative plant-soil feedback, i.e. they change the soil microbial community in a way that keeps their own abundance in check. Thus, drought-induced shifts in plant communities do not result from positive feedbacks, unless drought changes plant-soil feedback. We know that plant-soil feedback drives plant community succession, but its role in community response to drought has never been explored. Here, I will unravel whether and how changes in plant-soil feedback underlie strong shifts in plant community composition following drought. This knowledge is crucial for mitigating the effects of drought on terrestrial ecosystems. My objectives are: 1. Examining how drought affects plant community and soil microbial community composition and the implications for plant-soil feedback 2. Quantifying the effects of plant-plant and plant-microbial interactions on plant growth and subsequent shifts in plant community composition in response to drought 3. Disentangling the mechanisms underlying drought-induced changes in plant-soil feedback I will address these objectives in a novel set of approaches. I will identify general patterns in plant-soil feedback across European drought experiments, and assess the role of plant-plant and plant-microbial interactions across a Dutch secondary successional gradient. In a set of targeted mesocosm experiments, I will elucidate the mechanisms underlying changes in plant-soil feedback and the consequences for plant community composition. These approaches will result in a step-change in understanding the dynamics of plant-soil interactions under drought and the consequences for ecosystem change.