Ecological Function in Rivers: Insights from Crossdisciplinary Science

Because much ecological research in rivers applies theories developed elsewhere to a diverse array of habitats renowned for their spatial and temporal complexity, riverine ecology lacks a clear conceptual cohesiveness (Fisher 1997). Hence, the quest to identify, explain, and predict dominant ecological patterns and processes has led to the proposition of many conceptual models that also vary across spatial and temporal scales. These models range from the structure of river networks through to reach-scale models of flow regimes, patch dynamics, sediment organization, and stream hydraulics. Not surprisingly, the explicitness of these conceptual models to specific river types (e.g., headwaters, alluvial rivers, floodplain rivers) contributes significantly to the processes and linkages emphasized by the models. Despite the obvious lack of cohesion in conceptual models of river function, three themes are common to all such models and these are fundamental to riverine ecology: (1) identifying interactions between structure and function; (2) understanding the processes driving the arrangement of structural components in space and time; and (3) identifying how specific habitats and processes are connected in space and time. Critical reviews of conceptual models of river function are given elsewhere (see Thorp et al. 2006). Our aim here is to discuss these three themes as they relate to understanding river function.