Discussion
Our study highlights that both plant-plant interactions and plant-soil interactions can affect foliar and root metabolomic profiles viathe regulation of specific metabolites. We showed that metabolites that were regulated in leaves differ from those in roots, and that for two of our three plant species the number of regulated metabolites in leaves was higher than in roots. These results partially confirm our first hypothesis that both plant diversity and soil legacy can alter the overall plant metabolome, as well as affect the regulation of specific metabolites. Moreover, we revealed that the herbivore-induced metabolomic response is modulated by plant-plant and plant-soil interactions. This strongly suggests that the type and diversity of biotic interactions in the environment can alter induced responses to herbivores in plants. This confirms our second hypothesis that the induced defense to herbivory is differently affected by plant diversity and soil legacy. Compared to previous studies that focused on plant diversity effects in a field experiment (e.g., Scherling et al., 2010) or plant-soil feedback effects (Huberty et al., 2020; e.g., Ristok et al., 2019), our study provides new insights towards disentangling plant and soil diversity effects on plant metabolomes, and thus plant-herbivore interactions.