Plasticity of plant silicon and nitrogen concentrations in response to water regimes varies across temperate grassland species

Temperate grasslands exhibit strong spatial and temporal variation in water regimes. Thus, grassland plants experience potentially stressful water regimes, which may influence their tissue silicon (Si) and nitrogen (N) concentrations. Plant Si and N concentrations play important ecological roles in temperate grasslands, e.g. by influencing plant performance and herbivory, yet comparisons of species’ responses to a broad range of water regimes, including drought, waterlogging, and flooding, are lacking. We conducted a mesocosm experiment with ten temperate grassland species of two life forms (grasses and forbs) exposed to four different soil water regimes (drought, benign control, waterlogged and flooded conditions), and analysed their Si and N concentrations. Grasses showed lower Si concentrations under drought and flooding compared to the benign control and the highest concentrations emerged under waterlogging. Overall, plant Si responses of grasses were more uniform, while in forbs, r...