How do above- and belowground diversity modulate the impact of changing weather persistence on grassland growth and ecophysiology?

Precipitation regimes are becoming more persistent under climate change, resulting in abnormal and prolonged dry and wet conditions that can affect ecosystems and lead to yield losses. Understanding how agricultural grasslands respond to changes in precipitation regimes, and whether diversity both above- and belowground can modulate these impacts, is therefore of great importance. In this study, we investigated whether grassland plant diversity (number of species and dominance patterns) and abundance of arbuscular mycorrhizal fungi (AMF) can help stabilize ecosystem functioning under changing weather persistence.The experiment was conducted at the Drie Eiken Campus, University of Antwerp, Belgium. Seven outdoor plots were established using a complete factorial design with two AMF treatments, three precipitation regimes (including a common extreme drought), and seven grassland communities. In total, 350 mesocosms were established. Precipitation patterns were simulated using automated screens and drip irrigation, and the AMF addition was carried out with commercial Rhizoglomus irregulare inoculum pellets. In order to assess the responses of grassland performance and productivity and the role of AMF under changing weather persistence, plant response variables such as aboveground biomass, green cover, and ecophysiological variables (photosynthesis, chlorophyll fluorescence, stomatal conductance, and chlorophyll content) were measured. Furthermore, we have investigated changes in the colonization, richness, diversity, and composition of AMF communities in response to changing weather persistence.Results presented at the conference will cover the 2025 growing season, focusing on stress build-up, resistance and recovery, and effects thereon of the various single and combined treatments. Particular emphasis will be on the importance of plant community composition (differing species, species richness, and dominance patterns) and belowground diversity (AMF). We will discuss the underlying mechanisms, as well as the potential implications for the grassland management and adaptation strategies. Keywords: arbuscular mycorrhizal fungi (AMF), agricultural grasslands, biodiversity, climate change impacts, plant community composition, plant-microbe interaction, plant physiology.