slim-4,000 in Wfiflrlama ken, in large valleys, and especially in eool moisl elimares, llie upslope wind may resuli in ine general ii a! a dam ol eiimulus elouds al «be valley liead. rr g oll as a sueeession bl eluuds lroiri mld—mornlng lo evening in more rropieal riumid elimaies, ilie eloud may be eoneinuously end on ine rrioiinrain lops: inis lonns pan onno sranding eloud ol liigli islands Surn eloud land rainlalll elleels are aereniuared by loiesl on me valley sides and ridges. .s uses «11le humidiry me air slreams by rranspiraiion in nor weallier. Valleys in rundra and desen suppori lree populalions absenl lrorn llie plain or peneplain areas surrounding ibern, bill lne reasons may diller iii rlial rundra valleys are likely lri be prolesled by ldnyenl deep snow rover niis preserves warm or sublzlkul soil lemperaruies in winler las well as pluvlding exress summer men molslurel Valleys m deserls remain moisl due lo lbe deep delrirus wnien lills llioir floms', lne shaded soils lose less moisiure lei evaporaiion Lernal soil lemperarures are also avoided by paroal shaldmg laoln lee-blasl and sandeblasi are modilied or absenl in valley lloors, so inn unproleeled seedlings Ian survive liign winds m inesnellerolyalleys 'rlius, valleys (or wadisl are prelened growing siles m deserrs, and provide lree produrls in oilierwise lreeless lundras, allliougli llie laller sires are rarely oeeupied by numan selllemenl. in me lleld, we ollen nonee a sudden eoldness ,usl belore dawn in valley nus; line is rlie nine ol rne grealesl deplli ol eold air, and nenee llie greattsl inlensiry ulwld llrr nowmg down lrorn ilie moimlains lias pooled all niglil, and yusr belore llie sun rises, we land many animalsl are or our grearesl exposure and lowesl elab ii is ai lliis lime rnar - ds oll glaciers flowing dnwn rald valleys ieaeli llieir maximum speed Willioui wind or air llow, indiaoon nosr ran lorin, as n dose in slrelrered liollows and liee Ell-Hugs in lliese areas, opening up llie elenrmgs or draining lliem oleeild air may help reduee rrosl, il can is die aim lsigure 5,13) Wlen, some years ago, i gyew sueli oops as lorriarioes and eiieurbi ide open lree samples, i did prevenl lrosl, bul losi crop due lei low liyil levels and a lack ol wind or irueel pollinalron, in sueli ease, a sliadeside screen ol ielleelor planrs lacing llie sun would lielp ro keep liglir Izvels up, and planrs io aroaei bees need lo be phced around llie eleariiig. Arbnull or ground browsers vollim loiesrs are also worrisome in gardens lpeissuin and poreupine lor example). Green-leal yegerables, bowever, are nol usually ealen, and can be summarily grown in small lorgl elearings or in open loresl in lrosry areas 5.3 LATITUDE EFFECTS Despile llie weak liglil and anon growmg season al 134 nign lsuopolarl lanrudes, me very long summer days provide rriore llian a sullieienr quanlily ol liglii ior vigorous plani growiri Tne daily loral lor laie summer llulyl is «a langleys ar Madras, lnd (will, ban langleys al Fresno, Calilomia lel, A50 al Fairbanks. Alnska MN) The average radoiion in lemperare areas is is lames inalol llie lropies lcnang, 1963! Thls is accenlualed, on or near cuasis, by ilie moderale lempemrures noin ilie eonlveerion 0! air over warm eurrenls in suen areas as Alaska and me norlnwesr eoaslal regions 0! Europe nie benelil ol lliose areas is lnar iris generally lower lemperaiiires, wnieb suil priolosynlliasis. eonler a pnorusynllielie ellieieney lnal makes a eonsiderable produelion ol rereal, berries, lumaioes, poisons, and vegerable erirps loleranl ol anon season/long day mndlnuns nie ollen deep periglaeial soils provrde rne basis lor irie produelion ol giganrlr lelrilee, rabbage. spinaelies, and roor eiopr, so lliai lliese areas are very lavuurable lor ageloilruie in surnrner, siieri (nmihnns prevail in Alaska, lreland, Ssolland, and pans or Norway sneller and added niienenls irrirn seaweeds and manures yield rirn meadows and heavy vegerable produeiion during lie long summer days The small stoneewalled lields ol lreland produce abundant sweer nay, mm oops, and guns lor siorage during winier. Conversely, llie ample liglil al low (equaloriall lamudes is inellirienl due lo me errremely liigli lemperalures lliere, and me mess ligni may mean iliai planls are ligrii saluraled, Pnoiosynlliesis may actually deeluie in irrelmense lignl, and rise energy buill inlo llie plants may be less in sunlignl llian in panial sliade. snade ldown ro a level ol 20% sunliglill is ol greal benelir in lropieal deserrs and sunny equalorial ales 'lrials ol sliadeelolli wiili soemli liglil lransmisrion may greally inerease plani bulk and produelion, e s ol sugar beer, inus llie imponanoe ol iree snade and slradeelorli in desens and cleared-area nopies. similarly, iemperalures above zsvc (77“F) sliarply decrease pnolosyninelie ellieieney, so llial llie normal deserr or Iquimnal eondillon ol nigli liglii and leniperalure is very inellieienl lor rne produerion ol planl malei-ial la rue areiie or liigii lariludes, IS'C lbw: isoyliriiiori foraddpked speeies and eulnvars, and mind-c lows-in lor uiariy useliil lood planls. Tropies arenmed [on low piodueiion olrnose erops which can be also grown in leinperale areas liglil shade may be the easenrial sompoisenl loir increased yields, in briglii sunliglil, leal lemperaruies ollen ereeed air lerriperaiuies, so llial rne dilluse liglil ol ovrreaal or rloudy days in liigii lariludes lielps planl growslr, especially aller midday as lemperalures wnuld rlren also rise above optimum in dlreer sunllglil, Pbolosynelnelie ellieieney is limiled by line amlity ol lne leal to oblain rarbein dinxide or by low levels ol available earbon dioiirde A| nign liglii iniensiry, we need m supply carbon dioxrde (|o llie saniralion level ol om. b0 oblain a H limes inerease in pnolosyn-