Fluvial landscape ecology: addressing uniqueness within the river discontinuum

Abstract

1. As rivers and streams are patchy and strongly hierarchical systems, a hierarchical patch dynamics perspective can be used as a framework for visualising interactions between structure and function in fluvial landscapes. The perspective is useful for addressing fundamental attributes of lotic ecosystems, such as heterogeneity, hierarchy, directionality and process feedback occurring across spatial scales and for illustrating spatio‐temporal linkages between disparate concepts in lotic system ecology such as the River Continuum Concept, the Serial Discontinuity Concept, the Flood Pulse Concept and the Hyporheic Corridor Concept. 2. At coarse spatial scales, the hierarchical patch dynamics perspective describes each river network as a unique, patchy discontinuum from headwaters to mouth. The discontinuum is comprised of a longitudinal series of alternating stream segments with different geomorphological structures. Each confluence in the steam network further punctuates the discontinuum because the sudden change in stream characteristics can create a `gap' in the expected pattern of downstream transitions. The discontinuum view recognises general trends in habitat characteristics along the longitudinal profile, but creates a framework for studying and understanding the ecological importance of each stream's individual pattern of habitat transitions along longitudinal, lateral or vertical vectors at any scale. 3. Object‐oriented modelling and programming techniques provide a means for developing robust, quantitative simulation models that describe the dynamic structure of patch hierarchies. Such models can simulate how the structure and function of lotic ecosystems are influenced by the landscape context of the system (the ecological conditions within which the system is set) and the metastructure (structural characteristics and juxtaposition) of finer‐scale patches comprising the system. 4. A simple object‐oriented, multiscale, discontinuum model of solute transformation and biological response along a stream channel illustrates how changing the branching pattern of a stream and the arrangement of its component patches along the downstream profile will result in substantial changes in predicted patterns of solute concentration and biotic community structure. 5. The importance of context, structure, and metastructure in determining lotic ecosystem function serves to underscore Hynes' (1975) concept that `every stream is likely to be individual.' Advancing the discipline of fluvial landscape ecology provides an excellent opportunity to develop general concepts and tools that address the individual character of each stream network and integrate the concept of `uniqueness within the river discontinuum' into our ecological understanding of rivers and streams.

Longitudinal discontinuities in riverine greenhouse gas dynamics generated by dams and urban wastewater

“…Although the river continuum concept has been useful in explaining gradual longitudinal variations in CO 2 from headwater streams to lowland rivers corresponding to the changing balance between autotrophy and heterotrophy (Borges and Abril, 2012;Koehler et al, 2012;Catalán et al, 2016;Hotchkiss et al, 2015), it has been increasingly recognized that rivers are often divided into discrete 450 segments such as reaches impounded by dams (Ward and Stanford, 1983;Poole, 2002) and eutrophic reaches receiving wastewater (Garnier and Billen, 2007;Yoon et al, 2017;Park et al, 2018). Previous studies of DOM biodegradation have often assumed a selective degradation of labile components of riverine organic matter along the continuum with minimal to low levels of anthropogenic perturbations (Koehler et al, 2012;Weyhenmeyer et al, 2012;Catalán et al, 2016).…”

Influence of morphohydraulic habitat structure on invertebrate communities (Ephemeroptera, Plecoptera and Trichoptera)

“…A number of hierarchical classifications which link the catchment and channel have been proposed as a tool for an effective river investigation and management, e.g. Frissell et al (1986); Pool et al (2002); ; Maddock (1999); Thomson et al (2001); Brierley et al (2002). These works have been used as conceptual guides for the development of the River Morphology Hierarchical Classification framework (RHMC) by Lehotský & Grešková (2003) In RHMC seven levels are identified: 1. catchment; 2. zone; 3. segment; 4. channel-floodplain unit; 5. river reach; 6. morphological unit; 7. morphohydraulic unit.…”

Scaling With Known Uncertainty: A Synthesis

“…The scaling ladder approach is based on the hierarchical patch dynamics paradigm (Wu and Loucks 1995) that integrates hierarchy theory with the patch dynamics perspective. The approach has proven useful in scaling landscape patterns and processes (Hay et al 2001, Poole 2002, Wu and David 2002, Burnett and Blaschke 2003, Hall et al 2004, Poole et al 2004.…”