ECOTONE HIERARCHIES

Ecological phenomena are evident over a broad spectrum of space and ti me scales. Ecotones, being defined as zones of transition between adja cent ecological systems, also must occur over an equally broad spectru m of space and time scales. Scale-dependent constraints influence ecol ogical phenomena and resulting zones of transition; however, in tradit ional ecotone studies little treatment has been given to these influen ces. This paper addresses aspects of the ecotone concept that relate t o the strength of interactions between adjacent systems for a hierarch y 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 sugg ested here. Constraints differ across this hierarchy, primarily becaus e of the different scales at which these constraints exert their influ ences. The basic strategy to understand these cross-scale influences m ust be to perform studies at different scales, and a hierarchical appr oach identifies those scales. This also is important for identifying t he appropriate technologies that focus at the scales where transition zones between ecological systems/phenomena are expressed. A broad arra y of technologies are available for integrating the pattern-process re lationships that occur across the many scales in ecological systems.