简介:Soilnitrogenpools(NP),denitrification(DN),grossnitrification(GN),N2OandCO2fluxrateswiththeirresponsestotemperatureincreasesweredeterminedunderfivedifferentlandusesandmanagementsinasubalpineforest-grasslandecotoneoftheeasternTibetanPlateau.Landusesconsistedof1)sparsewoodland,2)shrub-land,3)naturalpasture,4)fencedpasture,and5)tilledpasturemimickingagradientdegeneratingecosystemundergrazingimpacts.TheNO3--NcontentwashigherthantheNH4+-Ncontent.Comparingtilledpasturewithfencedpastureshowedthathigherintensivemanagement(tillage)ledtoasignificantdecreaseofsoilorganicmatter(SOM)(P<0.05)inthesoils,whichwasincontrasttothesignificantincreases(P<0.05)ofDN,GN,N2OandCO2fluxrates.GN(excludingtilledpasture)andCO2fluxratesincreasedwithatemperaturerise,butDNandN2Ofluxratesnormallyreachedtheirmaximumvaluesat12-14℃withtilledpasture(thehighestmanagementintensity)beingverysensitivetotemperatureincreases.TherewasadifferencebetweennetnitrificationandGN,withGNbeingabetterindicatorofsoilnitrification.
简介:Thechloroformfumigation-incubationmethowasusedtomeasurthesoilmicrobialbiomassC(SMBC)andN(SMBN)in16loessialsoilssampledfromAnsai,YongshouandYanglinginShaanxiProvince.TheSMBContentsinthesoilsrangedfrom75.9to301.0μgCg^-1withanaverageof206.μgCg^-1,accountingfor1.36%-6.24%ofthetotalsoilorganicCwithanaverageof3.07%,andtheSMBNcontentsfrom0.51to68.40μgNg^-1withanaverageof29.4μgNg^-1,accountingfor0.20%-5.65%ofthetotalNinthesoilswithanaverageof3.36%.AcloserelationshipwasfoundbetweenSMBCandSMBN,andtheybothwerepositivelycorrelatedwithtotalorganicC,totalN,NaOHhydrolizableNandmineralizableN.Theseresultsconfirmedthasoilmicrobialbiomasshadacomparativeroleinnutrientcyclesofsoils.
简介:SulfatecanbeactivatedbyATPsulfurylaseandadenosine5’-phosphosulfatekinase(APSK)invivo.RecentstudiessuggestedthatAPSKinArabidopsisthalianaregulatedthepartitionbetweenAPSreductionandphosphorylationanditsactivitycanbemodulatedbycellularredoxstatus.InordertostudyregulationofAPSKinrice(OsAPSK),OsAPSK1genewasclonedanditsactivitywasanalyzed.OsAPSK1C36andC69werefoundtobetheconservedcounterpartsofC86andC119,whichinvolvedindisulfideformationinAtAPSK.C36A/C69AOsAPSK1doublemutationwasmadebysitedirectedmutagenesis.OsAPSK1anditsmutantwereprokaryoticallyover-expressedandpurified,andthenassayedforAPSphosphorylationactivity.OsAPSK1activitywasdepressedbyoxidizedglutathione,whiletheactivityofitsmutantwasnot.Furtherstudiesinthecasethatoxidativestresswillfluctuateinvivo3’-phosphoadenosine-5’-phosphosulfatecontent,andallAPSKisoenzymeshavesimilarregulationpatternsarenecessarytobeperformed.