Riverine landscapes: Biodiversity patterns, disturbance regimes, and aquatic conservation

“The relative narrowness of lotic systems means that they have an intimate contact with their surrounding catchments and the terrestrial ecosystems they contain (Hynes 1975): the trophic dynamics of many loworder streams, for example, is driven primarily by inputs of terrestrial leaf litter (Fisher & Likens 1973); in t…”

“River corridors have been recognised as linear landscapes in which water flows play a key role in connecting various landscape patches (Junk, Bayley & Sparks, 1989; Malanson, 1993; Ward, 1998).”

“…elements at different scales since at least the 1980s (e.g. Allen & Starr, 1982; Urban et al., 1987; Turner, 1989) and those same concepts have more recently been applied to lotic ecosystems (Frissell et al., 1986; Townsend, 1996; Allan & Johnson, 1997; Ward, 1997, 1998; Montgomery, 1999).”

“…and decision makers are seeking measures to alleviate the resulting negative effects (e.g., Convention on Biological Diversity 1992, Christensen Manuscript received 24 July 2000; revised 10 May 2001; accepted 30 May 2001. et al. 1996, Stanford and Poole 1996, Ward 1998, Blöch 1999, Petts 1999).”

“There is general agreement within the scientific community that the flow regime is the grand structuring factor in rivers (Walker and others 1995, Hughes 1997, Poff and others 1997, Richter and others 1997, Ward 1998).”

“Our results imply that management practices that maintain the diversity of aquatic macrophytes in wetlands, such as sustaining or restoring a natural disturbance regim”

“…elements of a wider terrestrial landscape (as per Vannote et al., 1980’s River Continuum Concept) to those characterized by high spatial and temporal heterogeneity (Ward, 1998; Lapointe, 2012), and makes this heterogeneity the focus of assessment (Ward, 1998; Fausch et al., 2002; Legleiter, 2014b).”

“…environmental gradients and thus for high beta diversity of plant species (Whittaker, 1972; Nilsson et al., 1989; Nichols, 2007 The Authors, Journal compilation 2007 Blackwell Publishing Ltd, Freshwater Biology, 52, 651–679 Killingbeck & August, 1998; Ward, 1998; Gould & Walker, 1999; Capon, 2005).”

“For instance, the presence of an oxbow lake largely improves the topographic, hydrological, and habitat diversity of river valleys [279].”

“However, in their natural state, large streams often produce extensive floodplains, which are complex habitat mosaics that typically support high biodiversity (Ward 1998, Ward et al. 1999, Arscott et al. 2005).”

“The RCC is a longitudinal concept and does not consider transversal interactions between the river channel and its floodplain (Van den Brink, 1994; Lorenz et al., 1997; Ward, 1998).”

“It has been proposed that lotic communities are structured as nested hierarchies, with each stage forcing or constraining the stage below it (Frissell et al., 1986; Hildrew & Giller, 1992; Ward, 1998).”

“Remedies to thesehuman-causedproblemsareoftencostlyordifficult toimplement.Intheabsence ofmanipulation,floods and droughts interact with the underlying geology to shape the river’s physical and chemical templates; sites upon which the biotic communities develop over long time scales [23,31,33,34, 73 ] (Fig. 1). Signif…”

“Increasing attention is being paid to river conservation and lotic ecology at the landscape scale (reviewed in Ward, 1998).”

“Stream ecosystems are no exception (Matthews 1998, Ward 1998).”

“These simple scalar patterns of structural diversity may provide insight into the mechanisms responsible for hierarchical arrangement of biodiversity in river corridors (Ward, 1998; Ward et al., 1999a; Ward and Tockner, 2001).”

“Temporally variable flow regimes interact with spatially variable river channel and floodplain forms to support high biodiversity (Ward 1998, Wohl 2012).”

“2007) is needed to better understand key physicochemical and biological processes (Schlosser & Angermeier 1995; Fisher 1997; Ward 1998; Fausch et al. 2002; Power & Dietrich 2002; Wiens 2002; Benda et al. 2004; Fisher et al. 2004).”

“Much of this water would have reached the floodplain, sustaining a floodplain of more than 300,000 ha with complex flood-dependent biota and processes (Ward 1998).”

“Maintaining evolutionary and ecological processes (6), including disturbance regimes (7), hydrologic processes (2), nutrient cycles (8), and connectivity across spatial and temporal scales (9), is central to sound conservation.”

“Décamps (1984) applied this viewpoint to highly managed rivers, and Ward (1998) emphasized the importance of viewing all river systems in a landscape con- text.”

“We hypothesized that beta diversity should be associated with environmental heterogeneity (Anderson et al. 2006; Heino et al. 2013).”

“The ecological attributes of rivers are shaped largely by biogeochemical processes, and the morphology of rivers is strongly influenced by geology and climate (Imhof et al. 1996, Ward 1998).”

“Ecological integrity of floodplain rivers is mainly defined by the extent of the interphase between geomorphology and hydrology, resulting in a reach-specific level of habitat diversity and habitat characteristics (Bayley, 1995; Gregory et al., 1991; Junk et al., 1989; Naiman et al., 1988; Petts & Amoros, 1996; Schiem…”

“However, temporal variation in stream flow has also been identified as an essential driver of river biodiversity, production and sustainability (Poff et al. 1997; Ward 1998).”

“Although natural disturbance regimes can lead to fish mortality, they are a necessary component of a functional freshwater ecosystem (Resh et al., 1988; Ward, 1998).”

“It evaluates conditions in relation to the original state of the river-floodplain system (Ward and Stanford, 1995; Ward, 1998).”

“Oxbow lakes increase the topographic, hydrological and habitat diversity of the floodplain (Castella et al., 1984; Bornette et al., 1998; Ward, 1998) and the rate at which they transition from lentic to terrestrial habitat is controlled by how quickly they are filled by sediment (Piégay et al.”

“In general, fluvial systems maintain multiple interactive pathways across the riverine landscape (Ward, 1998), these features of the water biological resources should be taken into account for management, planning and conservation purposes.”

“1], Ward 1998) emphasized the role of lateral interactions with the floodplain as drivers of species richness.”

“Reaches and segments are usually considered as one-dimensional longitudinal habitats in constrained stream networks (Ward 1998) (Fig.”

“In this study, we use the phrase ‘riverscape’ (sensu Ward 1998; Fausch et al. 2002) genetics as an aquatic counterpart to landscape genetics in terrestrial ecosystems, and we consider how genetic differentiation of an aquatic organism is influenced by riverscape variables, namely seasonal barriers…”

“ant ecological factor in river corridors (Hejny, 1960; Van der Valk, 1981; Day etal., 1988; Baker, 1990; Naiman et al, 1993; Plachter & Reich, 1998; Pollock et al, 1998; Ward, 1998).”

“Floodpulses shape the ‘‘riverscape’’ (Ward, 1998; Allan, 2004) by creating and abandoning meanders and their substructures (e.g., Wantzen et al. 2005a).”

“Furthermore, the riverscape concept advocates a continuous downstream description of habitat variables in order to ensure that crucial features that explain the population dynamics of a particular reach are not missed (Fausch et al., 2002; Ward, 1998; Wiens, 2002).”

“Thus, the geomorphic structure of a flood plain is the template within which hydrologic function evolves and upon which, resulting habitat diversity and biocomplexity depend (Ward, 1998).”

“For example, overbank (flood) flows are a well-recognized functional flow component that supports a broad suite of physical and ecological processes, including the maintenance of habitat heterogeneity in space and time (Ward, 1998), providing cues for fish migration and reproduction (Jeffres, Opperman, & Moyle, 2008)…”

“(iii) In these landscapes site conditions vary greatly including, possibly, wetlands, old and abandoned river courses, places eroded through mechanical disturbance (Gregory et al., 1991; Ward, 1988); (iv) there are no immigration barriers within these landscapes.”

“Dams affect biota via disruption of the natural flow regime or the seasonal flood pulse to which organisms are adapted (Ward, 1998; Keddy et al., 2009) and by blocking migration routes (Poff et al., 1997; Poff and Zimmerman, 2010).”

“It is a multidisciplinary task, requiring biological, hydrological and geomorphological studies to be combined within a landscape perspective (Frissel et al. 1986; Gregory et al. 1991; Malanson 1993; Petts and Bravard 1996; Wassen and Groothans 1996; Hughes 1997; Ward 1998).”

“The lateral and vertical heterogeneity of hydraulic conductivities of the soil Hydrogeology Journal (2012) 20: 5–25 DOI 10.1007/s10040-011-0791-5 interface should contribute to a patchiness of nutritive conditions (Ward 1998).”

“…and rivers, riparian zones are prone to frequent natural flooding disturbances and are characterized by a strong environmental moisture gradient, generating a high spatial and temporal heterogeneity, which promotes a high biodiversity (Gregory et al. 1991; Naiman & D ecamps 1997; Ward 1998).”

“For mountain streams, for instance, human activities may result in the degradation of biogeographical barriers, thereby altering patterns of alpha and beta diversity among localities (Ward, 1998; Allan, 2004; Allan & Castillo, 2007; Passy & Blanchet, 2007; Donohue et al., 2009).”

“These exchange processes are altered and cut off respectively by the construction of dykes and dams and have significant effects on biodiversity (Ward and Stanford, 1995; Ward, 1998; Tockner et al., 1999b).”

“Floods are important drivers of ecological change that can significantly alter the aquatic biota (Ward, 1998; Adis and Junk, 2002; Lytle and Poff, 2004).”

“regulation, pollution and changes in land use, which reduce water flow and enhance river incision, sediment scouring, and water eutrophication (Ward and Stanford, 1995; Ward, 1998; Gasith and Resh, 1999).”

“the dispersal of organisms (Ward, 1998).”

“Hence, it remains difficult to evaluate how (and how much) recruitment processes, or their separate stages, contribute to the high biodiversity and commonly observed gradients found in vegetation along stream riparian zones (Naiman & D ecamps 1997; Pollock, Naiman & Hanley 1998; Ward 1998).”

“River regulation and water extraction for irrigation have changed the hydrology of rivers globally, disrupting river-floodplain connectivity, reducing flooding frequency and depleting water tables (Ward, 1998).”

“To deal with the greater demands on the world’s freshwater (March et al. 2003), barriers are constructed for power generation, flood control and irrigation, resulting in widespread degradation of river ecosystems (Zwick 1992; Ward 1998; King and Schael 2001).”

“In rivers the high biodiversity is attributed to large habitat heterogeneity (Hildrew, 1996; Ward, 1998).”

“Several studies have emphasized the importance of riparian ecosystems as centres of biodiversity since they link terrestrial and aquatic systems (Malanson, 1995; Naiman et al., 1993; Ward, 1998; Ward et al., 2002).”

“The mosaic of habitat patches, ecotones, and successional stages – the riverscape in all its complexity – is largely responsible for the biodiversity of rivers (Ward, 1998; Fausch et al., 2002; Robinson et al., 2002).”