2020年大学英语四级阅读备考材料5

1、2020年大学英语四级阅读备考材料（18）ResearchSolvesForestryProblemsForestryisascienceand,assuch,thosewhopracticeitmusthaveonethingthatmakescientificprogresspossible：thebenefitofresearch.Everyforestryproblemsolvedbyresearchletsforestryadvanceonemorevitalstep.Logically,therefore,researchtosolveproblemsisamajorjobofth

2、eForestService.Itcoversthewholeforestryfield,includingtheprotectionandmanagementofforests,relatedrangelands,andwater-sheds;utilizationofforestproducts;andtheeconomicaspectsofforestry.TheService'sregionalforestandrangeexperimentstationsanditsForestProductsLaboratoryareconstantlymakingnewforestrys

3、tudiesthroughouttheUnitedStatesandannouncingnewforestryfacts.RedeemingtheAmericanChestnut.Scientistshavelongbeenseekingwaysofbringingbackthatvaluableandstoriedtree,theAmericanchestnut.Attackedbyablight（枯萎病）broughtinfromAsiaabout1900,practicallyallofournativechestnutswerekilled.Theirgaunt（古瘦如柴的）white

4、skeletonsareareminderofatreewhoserangeextendedfromNewEnglandtoAlabamaandLouisiana.Butthereisaglimmerofhope.ForestServicescientistshavefoundafewindividualtreesthatseemtoberesistanttothedisease.Budsorbranchesfrom28ofthesetoughsurvivorshavebeengraftedtootherrootstocksformultiplicationandthechanceforfur

5、therstudyoftheirresistance.ForestresearchmayyetmaketheAmericanchestnutonceagaintemptthepalate(味觉),andalsohelpsupplythenation'stimberneeds.CanLightningFiresBePrevented?Forestershaveahardjobmakingpeoplecarefulwithfireintheforests.Atthesametime,someofthemaretryingtomakeNaturecutdownthenumberoffires

6、shestartswithhermostpowerfulfirestartingweapon,lightning.Alittlewhitecloud,peekingupoveraMontanamountain,isquicklyfoundbyamobileradarunit.Itistrackedasitgetsbiggerandstartsitsjourneywiththewinds.Finally,anylightningstormwhichdevelopsinitisanalyzed.Thiscooperativeresearchproject,knownas"Skyfire&

7、quot;,hasalsomadeexperimentsincloudseedingtoreducelightningoccurrence.Itistooearlyforpositiveconclusions,butscientistsbelievetheirfindingswillleadtoabetterpreparednessandquickerattackonlightning-causedfires.Forestersmayeventuallybeabletopreventlightningfiresmoreeasilythanthosecausedbyman.GettingMore

8、SeedfromBetterTrees.Wouldyoubelievethathealthytreesthathavebeendeliberatelywoundedwillproducemoreseedthanundamagedtrees?That'swhathappenedwhenforesterspartlygirdled(cutawayanarrowstripofbarkpartwayaroundthetree)somelongleafpinesinLouisianatheyproducedtwiceasmanyconesasdidungirdledtrees.InMontana

9、,theytrieditwithfive-yearponderosapines.Theseexperimentaltreesbore26conesasagainstoneconeontheungirdledcontroltrees.IntheSouthwhereslashpineis"chipped"(aformofpartialgirdling)forturpentine,thechippedtreesproduced50percentmoreconesthancomparableunchippedtrees.DevelopingaWhitePineStrainResis

10、tanttoBlisterRust.Youcanalwaysidentifythewhitepinesbecausetheneedlesareinclustersoffiveandtherearefivelettersinthewordw-h-i-t-e.ThisalsoappliestothesugarpineofCalifornia,whichisalsoawhitepine.Countthelettersins-u-g-a-r.Fiveagain!Whitepineshaveaparticularlyviciousenemythediseasecalledblisterrust.Long

11、agoscientistsfoundthatthediseasesporesdonotgofromonewhitepinetoanother;theyneedanalternatehost,eithercurrantorgooseberrybushes.Destroythesebushesnearwhitepinetreesandthediseaseisstopped.Thissoundseasy,butitisaveryexpensiveandtediousjob.Well,forestersaren'tsatisfiedwiththat.Theyhavefoundafewjusta

12、fewwhitepinetreesthatareresistanttothedisease.Startingwiththesefewtrees,theForestServiceandotherpublicagenciesintheUnitedStatesandCanadaaretryingtodeveloparesistantstrainofwhitepinethatwillstillhavegoodtimberquality.HowtonailaHouseTogether.Nailsaretheprincipalfastenersusedinbuildingawood-framehouse.

13、Howthesenailsareselectedanduseddetermineshowsolidthebuildingwillbe.It'simportanttoknowthesize,number,andplacementofnailsnecessarytoconstructahousesoitwillsuccessfullyresistsuchforcesofnatureasstrongwinds,hurricanes,earthquakes.TheForestProductsLaboratoryatMadison,Wisconsin,aunitoftheForestServic

14、e,hasmadeexhaustivestudiesofnailingtechniques.Theresults,containedinabooklet,TechniqueofHoseNailing,areofvaluetoengineers,architects,carpenters,andhome-ownersasaguidetothebuildingofbetterhouses.Withthebooklet(availablefromtheU.S.ForestService)onecanjudgethequalityofthenailingintheconstructionofhisow

15、nhouse.Will"sandwich"HousesBePractical?TheForestProductsLaboratorydevelopedasandwichbuildingpanelwithacoreofhoneycombpaper.Treatmentwithsyntheticresinsmakesthehoneycombedpaperresistanttomoistureanddecay.Tostudythesuitabilityofsuchpanesforhouseconstruction,ateststructurewasbuiltsomeyearsago

16、attheLaboratoryExposuretoMadison'srigorousweatherforsometimeindicatesthat"sandwiches"willbesuitableforuseinbuildings.Sandwichpanelsarenowusedindoors,partitions,furniture,anddemountablebuildings.Intimetheywillnodoubtbeusedinhouseconstruction.CanDirectSeedingofPineBeImproved?Inthepast,th

17、ereplantingofburned-overorcleancutforestareashasbeendonebythesomewhatslowandlaboriousmethodofindividualplantingofseedlingswhichhadbeenraisedintreenurseries.Directseedinginsuchareashadprovenunsuccessfulbecausebirdsandrodentswouldhelpthemselvestothisreadysupplyoffoodbeforetheseedcouldgerminate.Now,dis

18、coveryofabirdandrodentrepellentthatcanbeeasilyappliedtolongleafpineseedsbeforesowingis-makingthedirectseedingoftreespracticalandinexpensive.Therepellent,composedoftetramethylthiuramdisulfide,isnotharmfultobirdsoranimalsintheamountsusedanddoesnotretardgerminationoftheseed.Althoughitisslightlyirritati

19、ngtotheeyes,nose,andthroatofhumans,itissafetouse,accordingtostudiesmadebytheAlexandria(Louisiana)ResearchCenteroftheForestServiceandtheU.S.FishandWildlifeService.Directsowingoftreeseedsisthecheapestwaytoplant.Foresters,however,stilladvocatesettingoutseedlingsbecauseitisasimplerprocedureformostpeople

20、andmorepredictable.Butseedingisbecomingmorefoolproofandinanotherfewyearsshouldbemoregenerallyaccepted.Seedingcostsabout$8.50peracrecomparedto$12peracreforplantingseedlings.DoesAgeAffectStrengthofWood?Atestofthefloorjoists(托梁)oftheOctagonHouse,Washington,D.C.,showsjoiststhatwerecutformvirginSoutherny

21、ellowpineofhighqualitytobeasstrongaswhentheywereinstalledmorethan150yearsago.MechanicaltestbytheForestProductsLaboratoryshowedthatthetimberswerestrongenoughfortheirpurposeanddifferedlittlefromthestrengthofsimilarnewly-cuttimbers.Thetestsweremadeonsectionsfromseveralpartsofthejoists.Nodecaywasfound.1. Thepassagegivesageneraldescriptionofcontributionsmadebyforestry.2. Forestfirescausedbyligh