A framework for predicting the dynamics of plant-mycorrhizal interactions

Interactions between plants and mycorrhizal fungi shape nutrient cycling and ecosystem function on a global scale, but the dynamics of these interactions remain poorly understood. Due to their below-ground nature, directly observing key dynamical features such as Allee effects and oscillations is often not possible, hampering further progress in this area. Here we present a mechanistic model of plant-mycorrhizal interactions to address this issue. By integrating the facilitative and the antagonistic elements of plant-mycorrhizal interactions with explicit plant-nutrient dynamics, our framework generates testable predictions about the dynamics and persistence of these interactions. We find that plant-mycorrhizal interactions can exhibit different dynamical realms ranging from Allee effects to consumer-resource oscillations, and that these dynamics can be inferred from measurable system parameters (e.g., nutrient or carbohydrate uptake rates and saturation constants) and plant/fungal biomasses. Furthermore, we find that changes in the underlying soil nutrient supply can induce changes from one dynamical realm to another. Finally, we present a decision tree framework for characterizing the dynamics of real systems and discuss implications of our findings for plant-mycorrhizal communities in applied and natural contexts.