Mechanisms determine plant invasion impact. Plant invasion impact results from direct and indirect interactions between invasive and native species based on the interplay between invasive species traits, structure and function of the recipient community, and spatio-temporal heterogeneity of the environment. Direct interactions between invasive and native species result from competition or facilitation, e.g. for resources, whereas indirect interactions are mediated via subsequent changes in the biotic and abiotic environment, which may favour self-reinforcing processes of the invader or stabilizing processes of the community. Examples of important factors for each category are given in the boxes.