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简介：SoilsamplesweretakenfromanErmansbirch(Betulaermanii)-darkconiferousforest(PiceajezoensisandAbiesnephrolepis)ecotonegrowingonvolcanicejectainthenorthernslopeofChangbaiMountainsofNortheastChina,tocomparesoilcarbon(C)andnitrogen(N)transformationsinthetwoforests.ThesoiltypeisUmbri-GelicCambosolsinChineseSoilTaxonomy.Soilsampleswereincubatedaerobicallyat20-Candfieldcapacityof700gkg-1overaperiodof27weeks.TheamountofsoilmicrobialbiomassandnetNmineralizationwerehigherintheErmansbirchthanthedarkconiferousforest(P<0.05),whereasthecumulativeCmineralization(asCO2emission)inthedarkconiferousforestexceededthatintheErmansbirch(P<0.05).ReleaseofthecumulativedissolvedorganicCanddissolvedorganicNweregreaterintheErmansbirchthanthedarkconiferousforest(P<0.05).TheresultssuggestedthatdifferencesofforesttypescouldresultinconsiderablechangeinsoilCandNtransformations.

简介：TheimpactsofelevatedtemperatureandCO2onyoungsilverbirch(BetulapendulaRoth)saplingsafter0,25,50or75%artificialdefoliationwereassessedbymeasuringplantheightanddrymassofabovegroundcompartmentsandrootsandvariousmorphologicalandphysiologicalvariables.Defoliationeitherincreasedordecreasedplantgrowthdependingontheseverityofdamageandtheclimatictreatment.At21Cand400mgL-1CO2,defoliatedplantswerenotabletocompensateforthelostfoliage,butgrowthcompensationandadaptationtothechangedconditionsweregreater;growthofyoungdefoliatedsilverbirchsaplingsincreased,whichledtoincreasedheightandatendencytoenhancefinalabovegroundandrootbiomassandleafnitrogenandcarboncontentcomparedtothenondefoliatedcontrols.Nevertheless,theshort-termeffectofthedifferentclimaticconditionsdidnotresultinasignificantovergrowthofdefoliatedplants.AslightincreaseintemperatureandCO2werethemostacceptableconditionsfordefoliatedplants;however,a4CincreasewithcorrespondinglyhigherCO2wasmorestressfulasshownbylessgrowthinheightandbiomassallocationtoleaves,stemsandroots.Thefindingsfromthepilotexperimentaremoreapplicabletoyoungbirchtrees,butstressonyoungtreesmaybereflectedinfuturetreegrowth.

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