To be continued: the legacy of the River Continuum Concept

Posted on December 14, 2021


A recent review examined the historical importance of the River Continuum Concept (RCC), which was introduced by Robin Vannote and co-workers in 1980.  This concept revolutionised stream ecology research by prompting a shift from a descriptive to a predictive approach and encouraging multidisciplinary collaboration between biologists, geomorphologists and geochemists.  The RCC became a key framework for testing ideas about species distributions, community structure and energy flow in rivers.  The most innovative feature of the RCC is its proposal that biological communities vary in response to predictable changes in organic matter, channel form and light penetration that occur between headwaters and the lower reaches of river systems.  For example, upstream channels are narrow and strongly shaded by streamside vegetation, which contributes large amounts of coarse organic matter in the form of leaf litter, but downstream channels are wider and here primary production is limited by water depth and turbidity rather than riparian vegetation.  Although the RCC is not universally applicable, it has acted as a catalyst for later studies that have examined its limitations and thereby expanded the theoretical framework of river ecology.  Key research here has focussed on the dynamics of the whole stream network (not just the main stem), the effects of discontinuities along the length of a stream, and the ways that biological dispersal interacts with environmental variation.   It’s now clear that side channels and backwaters are important refuge habitats, that the floodplain is a key source of nutrients and organic matter, and that intermittent and temporary rivers are more common than previously thought.  As a result, river networks are now often visualised as mosaics of habitat patches rather than as continuous linear systems.  These investigations have spawned a clutch of post-RCC theories about river function, such as the Serial Discontinuity Concept, the Flood Pulse Concept, the Riverine Productivity Model, the River Wave Concept and adaptations of metacommunity and metaecosystem theory.   One of the most recent of these ideas is the Network Position Hypothesis, which predicts that the processes driving stream communities vary depending on their position in the river network: for instance, compared to headwater communities, those downstream should be more influenced by dispersal dynamics because they are more centrally located and/or better connected.

References:

Doretto, A. et al.  2020.  The River Continuum Concept: lessons from the past and perspectives for the future. Canadian Journal of Fisheries and Aquatic Sciences 77, 1853–1864.   https://doi.org/10.1139/cjfas-2020-0039

Vannote, R.L. et al.  1980.  The River Continuum Concept.  Canadian Journal of Fisheries and Aquatic Sciences 37(1), 130–137.  https://doi.org/10.1139/f80-017