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<br />:-:>-.~>.---.~.... <br /> <br />" <br /> <br />398 <br /> <br />J. A. STANFORD ET AL. <br /> <br />"". <br /> <br />Catchment Geology, <br />I Climate, Land-use <br /> <br />Natural.Cultural <br />Selling <br /> <br />'.,'".' '" 'I <br />..:':-.'.: .-:',," <br />. ,..-. ...'.-. <br /> <br />~t~~f;jl~' <br /> <br />nOr ')(\5 <br />u _ v.. <br /> <br />t <br /> <br />:" ~ ....... '.~ <br />/\~:~.\:. :~.: <br />. ~..;. ... . <br /> <br />Discharge <br />Channel-Floodplain <br />Geometry <br /> <br />Temperature <br /> <br />Substratum <br /> <br />Nutrients <br /> <br />Pollutants <br />Harvest <br /> <br />:':::>>:.:.~.:.:... <br /> <br />...:;'c.-'.:: 'c,; <br /> <br />Primary Controlling <br />Variables <br /> <br />::':"':":~'I <br />_. N ." ._-.. <br />. . .... .. ....,.'.... '..~'. <br />~'('~(f:~ .:<:: <br />.- ':~..'. . <br /> <br />f-:";<.::.....:..:.:. <br />,..,.. .'.::'.". <br />....;.:,...: <br /> <br /><,'.- - ~ . <br /> <br />.... -. .'- ~ .;, <br /> <br />t <br /> <br />t <br /> <br />Feedbacks <br />(t.g., ruuritmspfraling) <br /> <br />)~:/i~~;.~~~;;;; .~:~.~ i <br /> <br />i~:;ji.il~i~ <br /> <br />.~,:.. ., .- - ..; <br />t~:.:~~::'1-.<(:;1 <br />:f~'f~,~jil <br /> <br /> <br />Bioproduction <br /> <br />Riverine Foodweb <br />Bloticlll.leraCli.ODS <br /> <br />Oem:Iic and Biogeograpbic <br />IA.lCics <br /> <br />Figure 3. Primary controlling variables and biophysical interactions of river ecosystems <br /> <br />continuum in direct response to variations in the strength of interconnections between channel, ground~ <br />water, floodplain and upland elements of the catchment (Ward and Stanford, 1995a), <br />In our view the primary variables driving the distribution and abundance of animals and plants in flood <br />prone rivers are usually abiotic and primarily determined by the geological and climatic selling of the catch- <br />ment basin (Figure 3). Biotic interactions (e.g, competition, predation, parasitism), while they obviously con- <br />tinually occur within food-webs in all habitats, may become progressively more important and apparent as <br />the time between abiotic disturbances increases, and hence are most pronounced in spring-brooks and lake <br />ouiletstreams where abiotic drivers are comparatively non-variable (Ward and Stanford, 1983b; McAuliffe, <br />1983,1984; Reice, 1994), All big rivers that are not influenced by large on-channellakcs are naturally flood <br />prone, and ultimately biophysical structure is controlled by the inexorable, but highly dynamic, scouring <br />process of cut and fill alluviation, <br />Environmental heterogeneity (complexity) maximizes in the alluvial (aggraded) reaches of the river con- <br />tinuum. Owing to the energetics of materials transport through large catchment basins from high elevation <br />to sea level, alluvial reaches are arrayed along the stream continuum between canyon segments like beads on <br />a string (Figure 2), The hyporheic and riparian corridor is expansive on alluvial reaches and seasonal tem- <br />perature patterns vary within the wide array of aquatic habitats that exist laterally from the channel across <br />the floodplain (Ward, 1984). Large floodplains appear to function as centres of biophysical organization <br />within the river continuum (sensu Regier et ai" 1989). They are likely to be 'hot spots' of biodiversity and <br />bioproduction that are structurally and functionally linked by the river corridor (Copp, 1989; Gregory el <br />ai" 1991; Zwick, 1992; Stanford and Ward, 1993; Ward and Stanford, 1995a,b), Indeed, intermountain <br />and piedmont valley floodplains world-wide are characterized by nutrient-rich floodplain soils and diverse <br />and productive backwater and mainstem fisheries (Welcomme, 1979; Davies and Walker, 1986; Lowe- <br />McConnell, 1987; Sparks et al., 1990; Junk and Piedade, 1994; Welcomme, 1995). These reaches are also <br /> <br />:"...... '.'.',. <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br />(~~~1;~~~.;~~:;? ;.;~, <br /> <br />.::):~~{:..::.. ~'. :~..2 ~ I, <br />.. ~. . '.'-. . <br />~- ... ....; .: .~.~ ; . <br />:.",:,".'.. <br /> <br />. -... .": <br />::':',.;._.~.:,.~<:.-: <br />.~J}~;.::. <br />,'.;;.:.,..'. <br />'..""'."'--"":'1' <br />...-....,.. <br />~:~<.:.... . <br /> <br />...~..'".'.,'...,',;".,'.",..:...~~.;:.,~,:?".,;,:,:::..,t,'..._'.;:....'.'~~,::'::..:..:.:,:...,..:...3:/ ?~-::.~.z'.;:.~ i :> .. ~... " .. .'-.': . ..::~;>:.::.~:;~\;.. .. :.;~-." ~;,':;.~.:;.:. <br />" ".,: :' .:" ....':::{::<3;~~'!;f~';{::..:g:!~:';:/~~ :" ..': .",,'>< <br /> <br />'. <br /> <br /> <br />-- <br />,... ... ....' <br />;"::.l',:~ ': :-,:j':: ;"; :',.~.~i:~, '}+;{i:~ ~>:d;:~::::::'i'.:<:. :f5F'" <br /> <br />...... .. ...... <br />.' :'-c.. "'.''''''.' ,;.. <br />.'.,'. <br />