Resilience: nitrogen limitation, mycorrhiza and long-term palaeoecological plant-nutrient dynamics

Ecosystem dynamics are driven by both biotic and abiotic processes, and perturbations can push ecosystems into novel dynamical regimes. Plant-plant, plant-soil and mycorrhizal associations all affect plant ecosystem dynamics; however, the direction and magnitude of these effects vary by context and their contribution to ecosystem resilience over long time periods remains unknown. Here, using a mathematical framework, we investigate the effects of plant feedbacks and mycorrhiza on plant-nutrient interactions. We show evidence for strong nutrient controlled feedbacks, moderation by mycorrhiza and influence on ecological resilience. We use this model to investigate the resilience of a longitudinal paleoecological birch-δ15N interaction to plant- soil feedbacks and mycorrhizal associations. The birch-δ15N system demonstrated high levels of resilience. Mycorrhiza were predicted to increase resilience by supporting plant-nitrogen uptake and immobilizing excess nitrogen; in contrast, long-term enrichment in available nitrogen by plant-soil feedbacks is expected to decrease ecological resilience.