The relationship between propagule pressure and invasion success has been described empirically as a key process for understanding invading species. Much of the empirical work has been conducted in controlled seed addition plots, while the theoretical framework is largely verbal. Here we present an individually-based, spatially explicit simulation model in which invading propagules are introduced into a plot and allowed to grow. Each plant has two-dimensional location in the plot and circle of influence representing the area of resource utilization for the plant (analogous to the size of the plant). Essentially, this models spatial microsites for propagule establishment. The model has been specifically tailored to match the spatial scale of empirical prairie-based experiments. Results/Conclusions
We describe the basic relationship between propagule pressure and invasion success given a variety of scenarios such as competition from resident species and predation. The result of the model is a saturating response with propagule pressure such as those observed in empirical studies. Finally, the model is extended to include the linkage of above-ground and below-ground processes by modeling two circles of influence, one for the above ground and one for the below ground processes. Changes in the relative size of these circles allows us to model the effect of empirical treatments in prairie studies such as haying and nutrient addition.
