简介：Effectsofthreegapswhicharelarge(118m2),medium(86m2)andsmall(20m2),respectively,andundercanopyofTsugalongibracteataforestontheseedlingestablishmentofT.longibracteatawerestudiedthroughseedburialexperimentsfromDecember2003toJanuary2005inTianbaoyanNationalNatureReserveofFujian,China.TheresultsshowedthattheareaofgaphadanevidenteffectontheseedlingestablishmentofT.longibracteata.TheseedlingemergenceratesofT.longibracteatainplotsoflargegap,mediumgap,smallgapandundercanopywere10%,10%,4%and6%,representinganincreasingtrendalongwiththegapsizeincreasingwithoutasignificantdifference.Rainerodingandinsectsfeedingweretwomainfactorsleadingtoseedlingdeath.Thelargerthegapsizewas,themoreseedlingswerekilledbyrainerosionandthefewerseedlingswerekilledbyinsectsfeeding.Theemergencetimeofseedlingswasalmostsameinallplotswhiletheirdeathtimewasdifferentrespectively.Thegapsizehadasignificantimpactonseedlingsurvivalrate.Theseedlingsurvivalratewashighestinthemediumgapplot(27.0%)andnexttothehighestinlargegapplot(7.3%),andseedlinginsmallgapplotandundercanopyplotdiedoutafteronegrowingseason.Increasedlightsupplyingapswasfavorablefortheseedlingsgrowthandsurvival.IncreasedlightsupplyinthelargegapcouldenhancethegrowthofseedlingleafandrootofT.longibracteata,andtheseedlinginturnallocatedmoredrymasstorootandleaf,butithaslittleimpactonthegrowthofstem.ThisresearchindicatesthatT.longibracteataisapioneerspeciesanditsseedlingestablishmentneedamediumorlargegap(>50m2).

简介：Themechanicalpropertiesofwoodpowder/polypropy!enecompositeswithdifferentwoodparticlesizesandwoodspecieshavebeenstudied.AllofthewoodparticiesizesincreasedtheE-modulusofthecomposites.Tensiletestsshowedthatwoodpartidesizeshadanegativeeffectontheelongationatbreakandthetensilestrengthofthecompositeshasbeenimprovedwhenwoodparticlesizeswerebe(ow150μm(below100mesh).Fortheimpacttests,thewoodpartidesizeshadanegativeeffect,buttheMDFf...

简介：Inaviewofnaturalconditionsofestablishingnaturereserve,anindexsystemwaspreparedforquantitativeassessmentonstatusofendangeredspecies,andthusdegreeofendangeredspeciesinTibetwasevaluated.Takingasub-ecozoneasbasicunit,top5animalsand1plantwithhighEaswellasthenumberofspeciesineachunitwereenumerated;andthedegreeoflandutilizationwasfiguredout.Afterward,weselected6coefficients,assignedweight,andframedformulatoreckonproportionofnaturereserve,thusanareaofnaturereserveineachsub-ecozonewasobtained.In5schemesofweightassignment,aschemewithmediumareaofnaturereservewasselected.Allsub-ecozoneswereclassifiedinto4gradespriorconservation,1wasingradeA,2ingradeB,2ingradeC,and11ingradeD.Totalplannedareawasapproximately365135km2,about48834km2smallerthantheactualareaof413969km2,ratioofnaturereserveinTibetdiminishesfrom34.4%to30.38%.Basedon3factorsofhumandisturbance,ratioofbuffer-experimentalzoneinproposednaturereservewascalculated.Itwasdemonstratedthatexistingsizeofnaturereservesisexcessiveonthewhole,andtheirdistributionisnotreasonableentirely.Thesizeofnaturereservesin3sub-ecozonesofnorthernChangtangshoulddecrease,anddecrementofareaisapportionedamongother13sub-ecozoneswhichshouldincreasenaturereserve.HeterogeneityofregionaldistributionofrarespeciesinTibetisquiteobvious,soproposedareadistributionofnaturereservesismorescatteredthantheexisting.