Ecotone Hierarchies.

Ecological phenomena are evident over a broad spectrum of space and time scales. Ecotones, being defined as zones of transition between adjacent ecological systems, also must occur over an equally broad spectrum of space and time scales. Scale-dependent constraints influence ecological phenomena and resulting zones of transition; however, in traditional ecotone studies little treatment has been given to these influences. This paper addresses aspects of the ecotone concept that relate to the strength of interactions between adjacent systems for a hierarchy of ecotones in a biome transition area in central New Mexico on the Sevilleta National Wildlife Refuge. Zones of transition occur at plant, population, patch, landscape, and biome levels in the hierarchy suggested here. Constraints differ across this hierarchy, primarily because of the different scales at which these constraints exert their influences. The basic strategy to understand these cross-scale influences must be to perform studies at different scales, and a hierarchical approach identifies those scales. This also is important for identifying the appropriate technologies that focus at the scales where transition zones between ecological systems/phenomena are expressed. A broad array of technologies are available for integrating the pattern-process relationships that occur across the many scales in ecological systems.