Zonation Concept (Illies & Botosaneanu 1963), which defined a series of distinct commu- nities along rivers, separated by major faunal transition zones (e.g. the ...
The River Continuum Concept revisited: Lessons from the Alps Bruno Maiolini, M. Cristina Bruno Museum of Natural Sciences of Trento, Section of Hydrobiology and Invertebrate Zoology.
Historical perspective: from the view of rivers as a clinal zonation to rivers as dynamic ecosystems The distribution of organisms, resources, and biological processes change along rivers and depend on large-scale processes (e.g. climatic, hydrological, geomorphological) as well as local ones (e.g. biotic). The first attempt to categorize such discontinuities is the Stream Zonation Concept (Illies & Botosaneanu 1963), which defined a series of distinct communities along rivers, separated by major faunal transition zones (e.g. the rhithral–potamal transition). A more ecological perspective was introduced later by Vannote et al. (1980) with the River Continuum Concept, according to which resources change along a clinal (rather than zonal) gradient which predictably structures the stream biota. The River Continuum Concept explained the changes in biological communities only along the longitudinal dimension of the river, on the basis of its relationships with the terrestrial habitats. It was based on the observation that in small mountain streams below the tree-line, due to the shading effect of riparian vegetation, leaf input (Coarse Particulate Organic Matter, CPOM) largely exceeds primary production, heterotrophy is dominant, respiration is higher than photosynthesis (P/R1); as a consequence, macroinvertebrate communities are dominated by grazers and collectors. In large floodplain rivers, turbidity and unstable sandy riverbeds limit photosynthesis and the system reverts to heterotrophy (P/R
