Integrating the study of non-native plant invasions across spatial scales

Non-native (alien, exotic) plant invasions are affecting ecological processes and threatening biodiversity worldwide. Patterns of plant invasions, and the ecological processes which generate these patterns, vary across spatial scales. Thus, consideration of spatial scale may help to illuminate the mechanisms driving biological invasions, and offer insight into potential management strategies. We review the processes driving movement of non-native plants to new locations, and the patterns and processes at the new locations, as they are variously affected by spatial scale. Dispersal is greatly influenced by scale, with different mechanisms controlling global, regional and local dispersal. Patterns of invasion are rarely documented across multiple spatial scales, but research using multi-scale approaches has generated interesting new insights into the invasion process. The ecological effects of plant invasions are also scale-dependent, ranging from altered local community diversity and homogenization of the global flora, to modified biogeochemical cycles and disturbance regimes at regional or global scales. Therefore, the study and control of invasions would benefit from documenting invasion processes at multiple scales.