简介：Thepatternofprecipitation,includingprecipitationamount,frequencyandintensity,maychangeinthefutureaccordingtothepredictionofclimatechange.Inaridzones,thesoildynamics,plantgrowthandvegetationchange,desertificationandhydrologymightbeaffectedbyprecipitationchange.Ingeneral,theprecipitationinextremearidzoneandaridzoneshowedanincreasetendencywhereastheprecipitationinsomeareainsemi-aridzoneandsub-humidaridzoneshowedadecreasetendency.Theincreaseofprecipitationcouldenhancethegrowthofbiologicalsoilcrust,improvesoilwaterstatus,promoteplantgrowth,increasevegetationcoverage,facilitatethechangefromdesertvegetationtograsslandvegetation,anditisbenefittothereversionoflanddesertification.Inaddition,theincreaseofprecipitationcouldalsoincreasetheriverrunoff,lakestorageandpromotetheoccurrenceofflood,whilethedecreaseofprecipitationhastheadverseeffect.Thesestudieswillbenefitthepredictionofthepossibleresponseofecosystemprocessestothepotentialchangeofprecipitationpatterninaridzonesinthefuture,anditisimportanttotheconservationofnaturalvegetationandthecontrolofdesertification.Morefieldexperimentsandstudiesshouldbeconductedinthefuture,includingtheeffectofincreasedprecipitationortemperature,nitrogendepositionandCO2onsoil,vegetation,desertificationandhydrologyofaridzones,soasthemorepersuasiveresultscouldbeobtainedfromtheseexperimentsandstudies.

简介：Time-temperaturesuperpositionprinciple(TTSP)wasusedtoexaminedynamicviscoelasticpropertiesofChineseFir(Cunninghamialanceolata)woodatanextremelylowmoisturecontent(0.6%).Storagemodulusandlossfactordatawereobtainedatdifferentconstanttemperaturesrangingfrom25℃to150℃infrequencymultiplexingexperiments(0.1-20Hz).Allviscoelasticcurvesatothertemperatureswereshiftedalongthelog-frequencyaxistosuperimposethemonareferencetemperature(i.e.135℃inthisstudy)curve.Theextendedstoragemodulusandlossfactorisothermalmastercurveswereoverawiderangeoffrequency.TheshiftfactorsweredeterminedtobeafunctionoftemperatureandfittedintotheArrheniusequationwiththeleastsquaresmethod.TheresultsshowedthatthestoragemodulusdatawereexcellentlyfittedintotheArrheniusmodel,indicatingthevalidityofthemodeltocharacterizethedynamicstiffnessbehaviorofdrywoodintherangeof25-150℃usingtheTTSP.However,thetime-temperatureequivalencewasnotabletopredictthedampingproperties.

简介：ThisstudywasconductedintheHuoditangnaturally-regeneratedforest,whichislocatedatthecenterofthenaturalforestregionacrossthesouthern-slopeoftheQinlingMountains.Rainwaterandstreamwatersampleswerecollectedmainlyinrainyseasonsinthearea.ThesamplepHvaluesandchemicalconcentrationsweremeasured.Theresponseofstreamwaterchemistrytorainwateracidificationintheregionwasstudied.TheresultsshowedthatlongtimerainwateracidificationcouldresultinreductionofpHvalue,Ca2+andMg2+concentrationinthestreamwater.ThechangesofK+,Na+concentrationofstreamwaterwerenotcorrelatedwiththerainwateracidification.TherewasnoresponseofZn,PbandCdconcentrationofthestreamwatertorainwateracidification.Theacidifiedrainwaterdidnotresultinthereleaseoftheheavymetalsenrichedintheforestsoil.