A REVIEW OF MODELS OF ALIEN PLANT SPREAD

Alien plants invade many ecosystems worldwide, often having substantia l negative effects on ecosystem structure and functioning: The apparen t complexity of invasions has impaired the development of a predictive framework of alien plant spread. Such a framework requires both a con ceptual understanding of the ecology of invasions and appropriate mode lling tools. We demonstrate, using a simple conceptual model and illus trative examples from the literature, that a predictive understanding of invasions can be established. Potential modelling tools are reviewe d by categorizing models of plant spread as either simple-demographic, spatial-phenomenological or spatial-mechanistic, based on the model's data inputs and outputs. The assumptions, predictive potential, knowl edge and data requirements of these modelling tools are discussed in t he context of selecting the most appropriate alien plant spread model for a given case.