Plant species, and even ecotypes, generate unique communities of soil organisms. These soil communities in turn influence plant growth and competition. The nature of these plant-soil feedbacks is unique to different species and has been implicated in the success of invasive plants. Previous work has demonstrated that novel negative soil feedbacks in an invaded environment can reverse competitive hierarchies, allowing an otherwise competitively inferior plant to become invasive. I developed a universal model of plant competition with soil feedbacks to explore how both positive and negative feedbacks, and the combination of the two, affect plant competition. I identify coexistence and invasion thresholds with four potential scenarios of plant-soil feedbacks: Enemy Release, Pathogen Accumulation, Novel Weapons, and Nutrient Availability.

Results/Conclusions

My analyses suggest that the success of a plant species depends strongly on the nature of the relationship between soil communities and plants: specifically, how plant growth is affected by different soil community densities. Finally, using a patch-based spatial model, I explore how changes in spatial heterogeneity can affect the spread of invasive plant species by changing the costs and benefits of plant-soil interactions.