ABSTRACT
Any two ecological states have an ecotone, or zone of transition, between them. Recent conceptual advances have demonstrated that rather than being an average or combination of two communities, ecotones occur at multiple scales of ecological organization, are dynamic in space and time, and can exhibit emergent properties. The original concept of the ecotone was related to a spatial scale that encompassed two distinct vegetation communities, but recent research has emphasized the hierarchy of scale within ecotones, from transitions between individual plants (or smaller) to transitions from one biome to another. There are three basic types of ecotone dynamics in space and time: directional, stationary, and shifting, depending on the relative strength of different abiotic and biotic factors in the system. Ecotones modulate flows of material, energy, and organisms across landscapes, which has ramifications for a host of ecological processes such as dispersal, predation, and reproduction. As a result, ecotones can exhibit behaviors, or emergent properties, that are not simply a combination or average of the ecological states between which they are situated.
