LONGITUDINAL STRUCTURE OF AN AGRICULTURAL PRAIRIE RIVER SYSTEM AND ITS RELATIONSHIP TO CURRENT STREAM ECOSYSTEM THEORY

In an agriculturally developed prairie river system in C Illinois high rates of primary productivity (>15 g C.m-2.d-1) were characteristic of the watershed, although longitudinal patterns in riparian vegetation, stream temperature, and primary productivity were inverted relative to typical streams in forested uplands. Empirical models of gross primary production and community respiration were developed. Light availability, mediated both channel shading and turbidity appeared to be the principal factor limiting primary productivity. Both nitrate and orthophosphorus were found in high concentrations throughout the watershed. Largescale patterns in nutrient availability suggest that landuse patterns, and particularly urbanization, strongly affected spatial and temporal distributions of both nutrients. Differences between prairie river systems and "prototype' structures envisioned by the River Continuum Concept (RCC) derive from the descriptive nature of the RCC, and its inability to incorporate nonstandard distributions of key driving variables. -from Authors