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

“Flow regime in a freshwater ecosystem can be the most important perturbation factor governing biota dynamics and ecological processes (Walker et al. 1995; Puckridge et al. 1998; Ward 1998; Ward et al. 2001; Kingsford et al. 2004).”

“Aquatic ecosystems are facing significant pressures that threaten natural dynamics, ecological integrity, and biodiversity [1].”

“…populations and their relationship to critical habitat (e.g., movement among habitat patches), a more fine-grained perspective on thermal habitat [Ward, 1998; Fausch et al., 2002] is needed to ensure an adequate characterization of spatial and temporal heterogeneity in thermal processes that…”

“…systems in other regions of the world remains to be tested, but the general effects of river regulation on benthic invertebrates (Walker, 1985; Ward, 1998) and the importance of aquatic subsidies for terrestrial consumers (Ballinger and Lake, 2006) suggest that similar effects of river…”

“This puts the ʻinstitutional action frameʼ (Schön and Rein, 1994) of the policy sector in direct conflict with contemporary ideas in ecological management regarding the merits of diversity in ecological niches and gradients (e.g. Ward, 1998).”

“…over‐extraction of water (Gleeson et al., 2012), over‐exploitation (Allan et al., 2005), habitat degrada tion (Pratchett et al., 2011), ecosystem modification (Ward, 1998; Allan, 2004), invasive species (Baxter et al., 2007) and reduction in water quality (Tibby & Tiller, 2007; Clews et al., 2010).”

“River floodplains are flood-dependent ecosystems that are an integral part of the river (Ward, 1998).”

“Introduction Natural features of European floodplains are the result of dynamic geomorphological processes that lead to a high habitat diversity of these ecosystems (GERKEN, 1981; GERKEN, 1992a; WARD, 1998; WOLFERT et al., 2001).”

“2008) and (2) the dynamics of riparian zones are strongly influenced by flow regimes and fluvial processes (Ward 1998), particularly sediment movement (Naiman et al.”

“Overbank flood events drive vertical, lateral, and longitudinal exchanges of material and energy (Ward 1998, Amoros and Bornette 2002), ultimately affecting patterns of edaphic conditions, sediment deposition and scour, vegetation dispersal and forest succession, and biogeochemical cycling through…”

“Second, the 479 reduction of the magnitude and frequency of floods resulted in a disruption of lateral 480 processes of river-floodplain connectivity (productivity and disturbance) maintaining riparian 481 succession and diversity (Ward and Stanford, 1995; Ward, 1998).”

“Increasingly, basic principles from landscape ecology have been tailored for river ecosystems (Fausch et al. 2002; Ward 1998; Ward et al. 2002).”

“Also, studies of entire rivers as landscapes with emergent properties changing with the spatial extent of the observations have received increased attention in recent years (Schlosser 1991; Ward 1998; Fausch et al. 2002).”

“Thus, assuming that species track their preferred environmental conditions 50 , the more diverse habitats are across riverscapes, the more variable the composition of communities (beta diversity) 58 .”

“River restoration is growing in importance given that human efforts to regulate flow and stabilize river channels during the 20th century have impacted most large North American rivers (Bayley 1995), with consequent disruption to natural disturbance regimes, truncation of environmental gradients, and severing of conne…”

“The distribution of inundation plays a critical role in controlling the structure and functioning of floodplain and wetland ecosystems (Amoros and Bornette 2002; Junk et al. 1989; Ward 1998).”

“For instance, Warmbold and Wesner (2018) show that the impacts of insectivorous fishes on aquatic-to-terrestrial prey flux (rate of energy exchange between ecosystems; e.g., between water and land) were different than their effects on benthic insect prey biomass in the aquatic ecosystem.”

“Extreme water-level Xuctuations present severe challenges for the conservation of the biodiversity of the lake ecosystems, particularly localized in the shallow waters, where most benthic macroinvertebrate species inhabit (Ward 1992; Ward 1998 ).”

“Interpreted at the landscape scale, this hypothesis suggests that spatial and temporal variability in disturbance creates patches of varying age, thus maintaining a diversity of sites suitable to a variety of life history strategies (Ward 1998).”

“…(up-valley/down-valley) and transversal (cross-valley) physicochemical gradients related to shear stress, soil moisture, flooding frequency, sediment texture and cohesion, organic matter, and nutrient content (Naiman and D ´ ecamps, 1997; Pautou et al., 1997; Ward, 1998; Steiger et al., 2005).”

“663 Results Multivariate analysis revealed that riparian forest deforestation affects the variation between hydrological periods (NPMANOVA, F [2,29] = 1.”

“These factors change microhabitat conditions and hydraulic forces (Ward, 1998; Fausch et al., 2002; Benda et al., 2004).”

“The IDH (cf. Grime 1973; Connell 1978; Wilkinson 1999) has been discussed in detail with relation to floodplain environments in a number of articles (e.g. Ward 1998; Ward & Tockner 2001; Amoros & Bornette 2002).”

“Aquatic and riparian environments greatly expand the range of available microclimates within a landscape (Naiman et al. 1998, Chen et al. 1999), and generally support the highest biodiversity (Naiman et al. 1993, Ward 1998 ).”

“…through water flow regimes, water quality and water temperature; and the biological component with a suite of species and communities which have adapted to the conditions created by their interactions with the abiotic components (Poff et al., 1997; Ward, 1998; Ward and Tockner, 2001; Wiens, 2002).”

“A predominant paradigm in aquatic ecology is the connectedness among ecosystem components (Ward 1998; Wiens 2002).”

“magnitude, and water abstraction (Ward, 1998).”

“Therefore, the development of environmental characteristics and biota within floodplain segments with the same connectivity depends on the morphology of the floodplain and may evolve differently in different aquatic habitats within the floodplain [68].”

“Colmation impairs vertical and lateral connectivity, and stream regulation promotes colmation due to a low frequency of flushing flows (Ward, 1998).”

“The diversity of hydro-ecological conditions that result from disturbances due to regular floods and high water tables drives high habitat heterogeneity and primary productivity (Grevilliot et al. 1998, Ward 1998, Gowing et al. 2002, Woodcock et al. 2005).”

“The composition and configuration of the river landscape determines the fish assemblage diversity and abundance [33, 34].”

“Natural disturbances induced by intense rainfall or flooding could enhance the ecological connections between terrestrial and aquatic ecosystems (Ward 1998) and, as mentioned in literature, should enhance the development of resource generalists (Poff and Allan 1995).”

“As attempts to re-establish the ecological connectivity (Ward, 1998) of upland river floodplains in regulated systems gain popularity (Debano and Schmidt, 1990), there is a growing need for a more thorough understanding of the natural functioning of upland riparian ecosystems, and the sediment and…”

“They are characterised by high habitat heterogeneity, primary productivity and biodiversity (Grevilliot et al. 1998, Ward 1998, Gowing et al. 2002a, Woodcock et al. 2005).”

“The composition, configuration and degree of hydrological connectivity of these habitats determine biodiversity and ecosystem processes (Tockner & Stanford, 2002; Ward, 1998).”

“The physical template of these catchments controlled not only stream velocity and channel morphology, factors viewed as 2 of the most important in governing distributions of macroinvertebrates (Ward 1998) and juvenile salmonids (Quinn 2005), but also the type and amount of wetlands.”

“Obligate aquatic species have naturally limited dispersal options, which have been further constrained by widespread habitat fragmentation and water abstractions (Ward 1998).”

“…governed by landscape-level controls on stream hydrology such as geology and land use that are reflected in stream depth, width, and water quality (Hynes 1975, Roth and others 1996, Allan and others 1997, Fitzpatrick and Giddings 1997, Schlosser 2002, Ward 1998, Fausch and others 2002, Allan 2004).”

“One reason that broader-scale factors may better predict local responses is because broad-scale variables integrate a suite of correlated fine-scale factors (Allan et al. 1997, Ward 1998, Huston 1999, Azaele et al. 2015).”

“Within freshwater ecosystems, considerations of connectivity, scale, land use and disturbance regimes are also critical for biodiversity conservation planning (Mancini et al. 2005; Saunders et al. 2002; Ward 1998).”

“Ward (1998) expanded previous theoretical developments by explicitly incorporating concepts of terrestrial landscape ecology into a “riverscape” approach to lotic ecology.”

“(16) Trait-related assignment to endpoints of life-history strategies after the classification of Winemiller and Rose (1992). Species previously assigned (Blanck et al.”

“Riparian systems are biologically important components of landscapes worldwide, supporting a disproportionate amount of ecosystem services and species diversity compared with adjacent terrestrial ecosystems (Ward, 1998; Brauman et al., 2007).”

“…ideal empirical context in which to assess phylogenetic community structure at various scales, as assemblages are interdependent in a hierarchical fashion when considering levels from entire drainage basins to local sites and microhabitats (Ward, 1998; Lowe et al., 2006; Statzner & Dolédec, 2011).”

“Flow-regulated rivers show declines in aquatic complexity and biodiversity when river currents are replaced by still water conditions (Poff and Allan 1995; Abramovitz 1996; Ward 1998).”

“They are known to pro- al Eng v a o a s H f i s “ o a n f ( m t i d t t q s ( c r u p F s K.E. Schilling et al. / Ecologic ide important topographic, hydrological and habitat diversity long floodplain corridors (Ward, 1998).”

“Similar developments occurred in aquatic and riverine ecology (Benda et al., 2004; Kiffney et al., 2006; Rice et al., 2006; Ward, 1998).”

“This geomorphological diversity, coupled with constant disturbance brought about by flow variability, erosion and sedimentation, increases the diversity of habitats, ecotones and successional stages, thus enhancing the biotic diversity of the floodplain wetlands (Ward 1998).”

“The diversity in our data set is high compared with that in other studies (e.g. Ward, 1998; Deiller et al., 2001; Orlóci et al., 2002; Wang et al., 2002).”

“Alterations to riparian zones increase their vulnerability, and consequently, that of the rivers, should there be substantial changes in the environmental factors that are essential for the riverine communities [6,15].”

“…of patterns of biodiversity and species richness (Gregory, Swanson, McKee, & Cummins, 1991; Johnson & Host, 2010; Junk, Bayley, & Sparks, 1989; Ward, 1998; Welcomme, 1979), and monitoring of hydrological connectivity should be considered a vital component of efforts to conserve the ecological…”

“…the bio-ecological processes within rivers and corridors have been carried out in large- or medium-sized watercourses, generally in alluvial plains (Ward, 1998), in urbanized landscapes (Oneal and Rotenberry, 2008) and in arid ARTICLE IN PRESS R. Gentili et al. / Flora 205 (2010) 388–398…”

“Flooding is a fundamental driver of the spatial complexity in bottomland ecosystems because of its interactions and feedbacks with sediment dynamics, organisms, and ecological processes (Amoros & Bornette, 2002; Junk, Bayley, & Sparks, 1989; Tockner, Malard, & Ward, 2000; Ward, 1998; Wiens, 2002).”

“The multidimensional gradients structuring rivers and their associated riparian zones have been outlined in successive theoretical frameworks (Petts and Amoros 1996, Ward 1989, 1998, Tockner et al. 2010).”

“(Kjerfve, 1994; Ward, 1998).”

“As such, riverine ecosystems are often referred to as ‘riverscapes’ (Ward 1998; Fausch et al. 2002; Wiens 2002; Allan 2004), the riverine equivalent to terrestrial landscapes.”

“An oxbow lake is a stable lentic system, which, together with rivers, forms a mosaic floodplain of unique environmental gradients (Ward, 1998; Wang et al., 2020).”

“…influence of hydrological variability on local species richness is also likely due to fine-scale habitat heterogeneity and the availability of ‘habitat shelters’ generated by spatiotemporally varying hydrological conditions interacting with the geomorphology of the stream channel (Ward, 1998).”