Models of Ecological Processes in Riverine Ecosystems

Abstract

Ecological models are more like artists' sketches of landscapes than true facsimiles; and as such, they should be considered heuristic, that is, works in progress. Models describing structure and function within mostly pristine riverine ecosystems are primarily adaptations of theories developed in other ecosystems. Those most specific to lotic systems incorporate the unusually high degree of spatiotemporal variability of rivers. They are also hierarchical and account for the river's four dimensional nature: longitudinal (upstream-downstream), lateral, vertical (surface to hyporheos), and temporal. The best known model restricted to lotic ecosystems is the River Continuum Concept (RCC), which predicts a clinal response of organisms and ecological processes to gradual and continuous changes in physical conditions along a longitudinal dimension. The original RCC was modified along the lateral dimension for floodplain rivers by the Flood Pulse Concept, and the RCC's food web predictions were challenged by the Riverine Productivity Model, which emphasizes the importance of instream primary production. The importance of tributary junctions and branching patterns are emphasized in the Network Dynamics Hypothesis. More recent models, like the Riverine Ecosystem Synthesis, portray rivers as structured by large hydrogeomorphic patches rather than gradual clines and incorporate conclusions of the Natural Flow Regime model.