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