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<br />59 <br /> <br />R1paria~ Zones Form Migration Routes <br /> <br />The riparilin zones along tbe stream continuum Und to function as <br />migration corridors especially in arid and sellliarid IlIountainous regions <br />(Figure 6). Birds, deer, and elk annually travel th,~ corridors from <br />high-elevation summer ranges to low-elevation winter ranges. The cover, <br />shelter, feeding, watering and IIlicro-cli...ate opportunities afforded by <br />riparian zones are ideal for IIligr..ting sp..cl.es of wildlife. Some species, <br />such as birds and small mammals use riparian zones alO dispersal routes from <br />their original habitats when confl'onted by shortages of food, water, or <br />other life cycle requirements. <br /> <br />~,."".~.-<!'~I' <br /> <br />,.' , ..4:'- ."",,l.. <br />1 .., ~.'~ . ... . iJ~~I.. <br />SI11"fMf'RMg. ~t. -:'I~""b ~ <br />----~)~.~ ""'~.,~,.... <br />~._~ <br />Spring'n'~ "~0~.". <br />__.d:2'~,~~~_ ~ ~~ <br />- ~,' ,j::J'7~~ <br />Win1P1'R~~~..e. 1(.._........' <br />_'~~~.r <br />- '~- ~ ;;-~,~..;, --,::- - <br />-~- -0;-'" _~; ::---.;::~. <br />-.-,'" -:"~"'::::'-r--"~' . -~- <br />'lgu'.('Jl;P.t4'''I_.~1o''9.i''''I.''d'I'PIJ"''''.''.lllv...It, <br />V......''''I'..b_ro...'Up'...,Il!l".....rfl''a'.,'eo..''c>'r!d&'..Mdb' <br />rnl.ll.d..'b._....."'........rtg..'higPl.J.O..bo..."d.....,... <br />.......'1._"..__1.11"'.,...'.... <br /> <br />(Modified fro. Tholllu et tll 1979) <br /> <br />Riparian Zones Maintain Water Temperature <br /> <br />Water temperature elevation caused by removal of riparian ve,getation <br />can significantly affect stream community structure and function. As water <br />temperature increases, water's capacity to hold oxygen decreases. <br />Therefore, when the water temperature is elevated the ability of streams to <br />assimilate wastes without oxygen depletion is reduced. Elevated <br />temperature also increases the rate at which nutrients attach to suspended <br />solids and thereby reduces readily available soluble forms (Sommers 1975). <br />For example, increases in temperature above 15 C produce exponential <br />increases in the amount of phosphorus released. <br /> <br />Net thermal radiation in relation to stream discharge is the primary <br />determinant of stream water temperature. Stream temp,eratures are therefore <br />greatly affected by nearstream vegetation. The shading ability of the <br />riparian vegetation on smaller streams is a function of canopy density. <br />Weekly maximum temperatures of streams in cropland ar'~as were 5.0 C to 12.8 <br />C (average 4.6 C) higher than those of a nearby forested stream (Green <br />1950). Temperatures of the forested stream during th,~ coldest month <br />(February) were as high as 3.9 C above the farm streallll. Summer water <br />temperatures for a stream inside a small wa,odlot (19 G) were much lower <br />