Significant Acidification in Major Chinese Croplands

REPORTS

SignificantAcidificationinMajorwhethertheyalsocausesignificantsoilacidifi-cationatanationalscale.

ChineseCroplands

Anationalsoilsurveywasconductedduringtheearly1980s,andpHwasdeterminedinalltopsoilsthatweresampled(17).Forcomparison,J.H.Guo,1*X.J.Liu,1*Y.Zhang,1J.L.Shen,1W.X.Han,1W.F.Zhang,1P.Christie,1,2wecollectedallpublisheddata(13)ontopsoilpHK.W.T.Goulding,3P.M.Vitousek,4F.S.Zhang1

from2000to2008andcompiledtwo(unpaired)datasets(1980sversus2000s)onthebasisofsixsoilgroupsaccordingtogeographyanduse,withSoilacidificationisamajorprobleminsoilsofintensiveChineseagriculturalsystems.Weusedtwotwosubgroupspersoilgroup:cerealcropsandnationwidesurveys,pairedcomparisonsinnumerousinpidualsites,andseverallong-termcashcrops(tablesS1andS2andfig.S1)(13).Inmonitoring-fielddatasetstoevaluatechangesinsoilacidity.SoilpHdeclinedsignificantly

China,bothsystemsreceiveveryhighnutrient(P<0.001)fromthe1980stothe2000sinthemajorChinesecrop-productionareas.Processesinputsascomparedwiththoseofotheragricul-relatedtonitrogencyclingreleased20to221kilomolesofhydrogenion(H+)perhectareperyear,turalsystemsworldwide(18),especiallythecashandbasecationsuptakecontributedafurther15to20kilomolesofH+perhectareperyeartocrops(suchasgreenhousevegetablesystems),soilacidificationinfourwidespreadcroppingsystems.Incomparison,aciddeposition(0.4towhichhavedevelopedrapidlysincethe1980s2.0kilomolesofH+perhectareperyear)madeasmallcontributiontotheacidificationof(19).

agriculturalsoilsacrossChina.

Theresultsrevealsignificantacidificationofalltopsoils(averagepHdeclinesforthesoilA

groupsof0.13to0.80)exceptinthehighest-pHcidificationcanalterthebiogeochemis-slowlyundernaturalconditionsoverhundredstosoils,whichrepresentonlyasmallpercentageoftryofecosystemsandadverselyaffectmillionsofyears.Oldsoilsandsoilsinhigh-Chinesecultivatedsoils(tableS1).Inallotherbiota(1,2).Poorlybufferedfreshwater

rainfallregionstendtowardgreateracidity(8).soilgroups,acidificationhasbeengreaterincashsystemshavebeenchangedsubstantiallybyan-Naturallyacidsoilsoccupyapproximately30%cropsystems(pHdecreasedby0.30to0.80)thanthropogenicacidification(3),mostlybysulfuricoftheworld’sice-freelandandarecommonlyundercereals(0.13to0.76)(Table1).Theseareandnitricacids,andthesurfaceoceanhasacid-associatedwithphosphorus(P)deficiency,Alsubstantialchanges.ThepHscaleislogarithmicifiedmeasurablyfromincreasedcarbondioxidetoxicity,andreducedbiopersityandproduc-andapHdecreaseof0.30(CO2)intheatmosphere,raisingconcernsabouttivity(9).

+correspondstoadoublinginhydrogenion(H)activity.

marinebiopersityandecosystemfunction(4–6).ChineseagriculturehasintensifiedgreatlySoilsingroupI[forexample,leachedredAnthropogenicacidificationofsoilshasreceivedsincetheearly1980sonalimitedlandareawithsoils(Argi-UdicFerrosols)andyellowsoils(Ali-lessattention.SoilsarestronglybufferedbyionlargeinputsofchemicalfertilizersandotherPeriudicArgosols)]arethemostacidicinsouthexchangereactions,bytheweatheringofsoilmin-resources.Grainproductionandfertilizernitro-Chinaandhaveacidifiedfurthersincethe1980s,erals,and(intheacidicrange)byinteractionswithgen(N)consumptionreached502millionandwithpHdeclinesof0.23and0.30(P<0.001)inaluminum(Al)andiron(7).Soilsacidifyvery

32.6milliontonsnationallyin2007,respectively,cerealandcashcropsystems,respectively(Table1).increasesof54and191%ascomparedwith1981AlthoughnetpHdecreasesforgroupIsoilswere1

CollegeofResourcesandEnvironmentalSciences,China(10).HighlevelsofNfertilizationcandrivesoilsmallascomparedwiththoseofothergroups,theAgriculturalUniversity,Beijing100193,China.2Agri-Environmentacidificationbothdirectlyandindirectly(11–13),impactmaybemorepronouncedbecausetheseBranch,3

Agri-FoodandBiosciencesInstitute,BelfastBT95PX,UK.DepartmentofSoilScience,RothamstedResearch,Harpenden,andtheratesofNappliedinsomeregionsaresoilsareapproachingpHvaluesatwhichpoten-HertsAL52JQ,UK.4DepartmentofBiology,StanfordUniversity,extraordinarilyhigh(14)ascomparedwiththosetiallytoxicmetalssuchasAlandmanganese(Mn)Stanford,CA94305,USA.

ofNorthAmericaandEurope(15).Thesehavecouldbemobilized(20,21).

*Theseauthorscontributedequallytothiswork.

degradedsoilsandenvironmentalqualityintheAttheotherextreme,soilsingroupV[main- NorthChinaPlain(16)andintheTaihuLakelyfluvo-aquicsoils(Ochri-AquicCambosols),zhangfs@http://doc.guandang.net.

Towhomcorrespondenceshouldbeaddressed.E-mail:regioninsouthChina(14).Here,weinvestigate

whicharewidelydistributedinnorthChina]are

Table1.TopsoilpHchangesinmajorChinesecroplandsbetweenthe1980sand2000s.Thesoilgroupsaredefinedin(13).NS,notsignificant;pHrangeisanaverage(5to95percentile).

1980s

2000s

SoilgroupSamplenumber

pHvalueCerealcropsystems*

Cashcropsystems

Samplenumber

pHvaluepHchangeSamplenumber

pHvaluepHchangeI3015.375.14(4.40–6.60)505(4.17–6.52)–0.23 3375.07(3.93–6.44)–0.30 II11576.336.20(5.00–8.04)1101(5.00–7.70)–0.13 4135.98(4.58–7.49)–0.35 III2976.425.665.62(4.50–8.30)211(4.27–8.06)–0.76 98(4.27–7.73)–0.80 IV5626.326.005.60(5.10–7.89)537(4.84–7.60)–0.32 238(4.07–7.42)–0.72 V9957.967.697.38(6.39–8.80)850(5.37–8.70)–0.27 520(5.69–8.20)–0.58 VI

493

8.168.168.170.01(ns)

(7.10–8.80)

250

(7.49–8.82)

–0.00(ns)

10

(7.43–8.93)

*Cereal/fibercrops(suchasrice,wheat,maize,andcotton). High-inputcashcrops(suchasvegetables,fruittrees,andtea).

P<0.001.

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REPORTS

consideredresistanttoacidificationbecauseoftheirrelativelyhighCaCO3content(5to10%).However,theyhavealsoacidifiedsignificantly(P<0.001),withpHdecreasesaveraging0.27and0.58undercerealsandcashcrops,respec-tively.ThepHdeclineingroupVissmallcomparedwiththoseofgroupsIIIandIV(Table1)(13)butprobablyresultedinsubstantiallossofCaCO3.Therefore,soilpHdeclinemightbeexpectedtoaccelerateint …… 此处隐藏：15074字，全部文档内容请下载后查看。喜欢就下载吧 ……