Exploring Al, Mn and Fe phytoextraction in 27 ferruginous rockyoutcrops plant species.

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Contents lists available atScienceDirect

Flora

j o u r n a l h o m e p a g e :w w w . e l s e v i e r . c o m / l o c a t e / f l o r a

Exploring

Al,

Mn

and

Fe

phytoextraction

in

27 ferruginous

rocky

outcrops

plant

species

Antonella

T. Schettini

a

_,

_Mariangela

_G.P.

_Leite

b

_,

_Maria

_Cristina

_T.B.

_Messias

c

_,

Arnaud

Gauthier

d

_,

_Haixiao

_Li

d

_,

_Alessandra

_R.

_Kozovits

c,∗

a_Graduate_Program_in_Crustal_Evolution_and_Natural_Resources,_Department_of_Geology,_Federal_University_of_Ouro_Preto,_Minas_Gerais,_35400-000,_Brazil b_Department_of_Geology,_Federal_University_of_Ouro_Preto,_Minas_Gerais,_35400-000,_Brazil

c_Department_of_{Biodiversity,}_Evolution_and_Environment,_Federal_University_of_Ouro_Preto,_Minas_Gerais,_35400-000,_Brazil d_Département_des_Sciences_de_la_Terre,_Université_de_Lille1,_Villeneuve_d’Ascq,_France

a

r

t

i

c

l

e

i

n

f

o

Articlehistory:

Received16October2016 Receivedinrevisedform7May2017 Accepted13May2017

EditedbyP.Morellato Availableonlinexxx Keywords:

Biologicalabsorptioncoefﬁcients Canga

Functionaldiversity Phytoremediation Plant-soilrelationship Soilmetalavailability

a

b

s

t

r

a

c

t

Worldwide,substratesnaturallyrichinAl,FeandMnarethesubjectofmining,generatingdegradationof largeareasandproducingwasteswithhighpollutionpotentialforwaterresources,soilandatmosphere, causingharmtohumanhealthandecosystems.Thepresentstudyinvestigatedthetotaland phytoavail-ableconcentrationoftheseelementsinsoilsandleavesof27nativeplantspeciesfromferruginousrocky outcrops,ﬁndingvaluesabovethetoxiclimitsdescribedinliteratureandenvironmentallegislation. Foliarlevelsofmetalsvariedwidelyamongspecies,demonstratingdifferentphytoextractionor exclu-sionpotentials,whichwerenotexplainedbythetotalconcentrationofelementsoravailablesoilfractions. Althoughmostspeciesarenotconsideredhyperaccumulators,theresultsindicatetheexistenceofspecies relatedtositesofgreateravailabilityofcertainmetalsorthatcanmodifysoilqualitythroughtheir dif-ferentphytoextractionskills,withpotentialfutureusesindecontamination,stabilization,phytomining andecologicalrestorationprojects.

1. Introduction

Studiesonaccumulativeplantspecieshavebeenmostlyfocused onthehyperaccumulationcapacityoftoxicelementssuchasCd, Cr, Ni,Zn, Cuand Pbin anattemptto findsuitablespecies for decontaminationorstabilizationprocessesinpost-minedareasor thosecontaminatedbyagriculturalormunicipalwaste(Agarwal, 2009;Sarma,2011).Usuallyconsideredlesshazardous,Fe,Aland Mnare thefocusof significantly fewerphytoremediation stud-ies.However,theexposureofmaterialsrich in thesemetalsto theactionofrainandwindcanleadtocontaminationofwater resourcesandatmosphere,causingharmfuleffectstoenvironment andhumanhealth(BeyersmannandHartwig,2008;Duruibeetal., 2007;Murrayand Finkelstein,2007;Silva etal.,2015).In such situations,Fe,AlandMncouldbeclassifiedashazardouselements.

∗ Correspondingauthor.

E-mailaddresses:antonellatonidandel@yahoo.com.br(A.T.Schettini), mgpleite@gmail.com(M.G.P.Leite),cristinabotanica@gmail.com(M.C.T.B.Messias), arnaud.gauthier@univ-lille1.fr(A.Gauthier),lihaixiao001@gmail.com(H.Li), arkozovits@gmail.com,alessandra.kozovits@pq.cnpq.br(A.R.Kozovits).

In Brazil, currentlyworld’s third largest Fe and Alproducer andsixthmanganeseproducer(IBRAM,2015),largeareas origi-nallycoveredbynativemetalliferousvegetationgivewaytomined landscapeseachyear.Contrarytonationallaw,whichadvocates theuseofnativeplantspeciesintherecoveryofdegradedareas, mostminedareassufferintroductionofexoticspeciesorremain devoidofeffectiverevegetationandecologicalrestorationaction fordecades,resultinginsignificantenvironmentalliabilities.This realityreflectsthelackofstudiesonthebiologyofnativespeciesof ecosystemsnaturallyevolvedonironandaluminousformations, knownasferruginousrockyoutcropsorcangavegetation(Carmo andKamino,2015;Jacobietal.,2007;Skiryczetal.,2014). Floris-ticsurveysinkeyareasofoccurrenceofcangavegetationinBrazil revealthepresenceofadiverseflorawithhighdegreeofendemism. InsoutheasternBrazil,616specieshavebeencatalogedtodate,but onlytwostudiescontaininginformationonthepotentialfor accu-mulationofmetalsin13nativespeciesoftheseecosystemsand othersonsoilsrichinmetalshavebeenpublished(PortoandSilva, 1989;Silva,1992).Noneofthespecieswasconsidered hyperaccu-mulatorofpotentiallytoxicmetals(Co,Cu,Cr,PbandNi>1000ppm, andMnandZn>10,000ppm)accordingtoBakerandBrooks(1989).

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However,inrecentyears,inparalleltothesearchforspeciesthat arehyperaccumulatoroftoxicelementsandassociated methodolo-giesaimedatincreasingsoilandwaterdecontaminationefﬁciency, thereisagrowingdemandforstudiestofacilitatetheecological restorationofareasdegradedbymining.Inthiscase,thediversity ofspeciesand theirecologicalfeatures arefactorsmore impor-tantthanjusttheirhyperaccumulationpotential(Benayasetal., 2009).Recentstudiesinseleniummines,forexample,haveshown thathyperaccumulatorspeciesaffectsoilquality,preventingthe establishmentofotherspecies(Mehdawietal.,2011).Inthiscase, thisspecieswouldbeundesirableforuseinecosystemrestoration projects,oritspresenceshouldfollowrelativephytosociological proportionstootherspeciesofloweraccumulativeorexclusion potentialfoundinpristinenaturalareas.Thecoexistenceof differ-entecophysiologicalstrategiesregardingthemagnitudeofuptake anddistribution ofpotentially toxicelementsin differentplant partsbrings diversity tothe environment and createsdifferent possibilitiesofinteractions betweensoilandplantandbetween plantsandotherorganisms,expandingthefunctionalcomplexity ofecosystems.

ThepresentstudyexploredsomerelationshipsbetweenAl,Fe and Mn concentrations in soil and leavesof 27 native species (belonging to17 families) of a ferruginous rocky outcrop frag-mentintheIronQuadrangle,Brazil.Inagreementwithfindingsin otherenvironmentsevolvedontropicalacidsoils,weexpectedto detectfewmetal-hyperaccumulatingspecies(Kramer,2010),but still,awiderangeoffoliarAl,Fe,andMnconcentrations.Variations inmetalphytoextractionability,asareflexofplantspeciesand ecophysiologicalstrategiesdiversities,shouldbehighevenunder narrowrangesofsoilmetalavailability,andthus,significantand linearrelationshipsbetweensoilandfoliarAl,FeandMn concen-trationswillnotbefound.Somespecies,however,maybemore relatedtocertainsoillevelsofthesemetals,expressingdifferent sensitivitiesorcapabilitiesofsoilalteration.

2. Materialandmethods 2.1. Studyarea

Thestudywasconductedinaferruginousrockyoutcroparea locatedatthe“CachoeiradasAndorinhas”StateEnvironmental Pro-tectionArea,OuroPreto,MinasGerais,Brazil(20◦21S,43◦30W). Theareaconsistsofherbaceousandshrubbystrataassociatedwith rockyoutcropsofitabiritesorcangasandshallowsoils(Valimetal., 2013).Theaveragealtitudeis1492m. Theaverageannual tem-peratureis27.9◦Candannualrainfallofabout1204.8mm,95.5% concentratedinthemonthsfromOctobertoApril.

Thesoilofthestudyareashowedthefollowingaverage val-ues: pH (4.63), P (5.6mgkg−1),N (5.3gkg−1), base saturation (V=9.7%),aluminumsaturationindex(m=32),Fe(458.3gkg−1), Mn(0.9gkg−1)andremainingphosphorus(P-rem=41.3mgL−1). Othervaluesareexpressedincmolcdm−3:Sumofbases(SB=2.0), Ca(1.5),Mg(0.4),K(0.1),Al3+_(0.98).

2.2. Plantandsoilsamples

Atotalof27speciesbelongingto17familiescommonlyfound inferruginousﬁeldsinMinasGeraiswereselected(Jacobietal., 2007;Messiasetal.,2012)(AppendixA,Supplementarymaterial). A350-mtransect wastracedalong thehighest quotaofthe slopeandeveryﬁvemeters,inastraight line,individualsof 27 speciesthat were ata distance ofthree meters totheleft and rightofthetransectaxisweremarked.Then,threeindividualsof eachspeciesweredrawnforthechemicalanalysisofleaves.For eightspecies,however,onlyoneortwoindividualsinthesurveyed

areawerefound,andinthiscase,theconcentrationsofelements shown in Table 1 are not accompanied by standard deviation. Specieswithn=1wereAchyroclinealbicans,Bulbostylisﬁmbriata, Centrosemacoriaceum,Nematanthusstrigillosus,Pleopeltis hirsutis-simaandDoryopterisornithopus.Specieswithn=2werePaliavana sericiﬂoraandPsyllocarpuslaricoides.Healthyandmatureleavesin themiddlethirdofeachwoodyindividualandofallaerialparts ofherbswerecollectedduringtherainyseason(February–March 2013).

Intheseecosystems,soilonlyaccumulatesinsmallandshallow depressionsintherelief,whichgenerallydonotexceed5cmin depth.Therefore,soilsamplesat0–5cmindepthwerecollected intheprojectionofthecrownofeachindividualselectedforleaf analyses.

2.3. Plantandsoilanalysis

Leaveswerewashedindeionizedwaterandafterdryinginan ovenat40◦Cfor72h,weregroundinaknifemill.Then,250mg samplesunderwent aciddigestion (7.0ml of nitricacid 2mol/l and 1.0ml of oxygenperoxide 30%v/v) in a microwave (Mile-stone/Ethosone)(Gonzalezet al.,2009).Thereferencematerial usedwasAppleleaves,NIST–1515.Al,FeandMnwere quanti-ﬁedininductivelycoupledplasmaatomicemissionspectrometer (ICP–OES,Agilent725).

Afterdryinginanovenat40◦Cfor72h,thesoilcollectedwas groundandsievedinto0.0625mmmesh.pHwasdeterminedfor 10gsub-samplesofsievedsoilin25mlofdistilledwater.Another soilfraction underwent sequential digestionaccording to Stan-dard, Measurements and TestingProgram (Rauret et al., 2001) forextractingelementslinkedtoreadilyavailable,oxidizableand reduciblesoilfractions.Thevalues obtainedinthreestepswere summedandtheresultwasusedforEnrichmentCoefﬁcient anal-ysis(EC),asitrepresentsthetrulyphytoavailable elementpool (Podlesákováetal.,2001).Al,FeandMnweredeterminedby induc-tivelycoupledplasmaatomicemissionspectrometry(ICP-OES– Agilent725.).ThereferencematerialwasBCR701.

Soil fertility was also analyzed. The following parameters were determined: active acidity(pH), total nitrogen (N), avail-ableandremainingphosphorus(P,P-rem),availablepotassium(K), exchangeable calcium (Ca2+_), _exchangeable _magnesium _(Mg2+_), exchangeablealuminum(Al3+_),_potential_acidity_(H₊_Al), _sum_of bases(SB),effectiveCTC(t),CTCpH7(t),basesaturation(V)and aluminumsaturation(m)usingstandardmethodsadoptedbythe BrazilianResearch Centerfor Agriculture(EMBRAPA,1997).The Ndeterminationwasdonebysemi-microKjeldahlmethod.The availablePandP-remconcentrationweredeterminedby molec-ularabsorptionspectroscopyat725nmaftertheformationofthe molybdenite-Pcomplexviareductionbyascorbicacid.The avail-ablephosphoruswasextractedwithMehlich-1andtoestimatethe remainingP(P-rem)itwasusedasolutionofsoilsamples(5g)with a0.01molL−1CaCl2and60mgkg−1P(EMBRAPA,1997).

2.4. Biologicalabsorptioncoefﬁcients

Thebiologicalabsorptioncoefﬁcient(BAC),whichexpressesthe ratiobetweenshoot(leaf)elementconcentrationandsoil concen-tration(seeBaker,1981),wascalculatedforthe19specieswith asample numberequal tothree withboth thetotal concentra-tionvalues asplant-availablemetalsin soil.BACvalues greater andlowerthan1classifyplants,respectively,asaccumulatorsand excluder.

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Table1

Average(andstandarddeviation)Al,FeandMnconcentrationinsoilsampledunderthecanopyofspeciesintheferruginousrockyoutcropslocatedintheSerradaBrigida, MG,Brazil.

Family Species Soil-total(mgkg−1₎ _{Soil-available}_(mg_kg−1₎ _{total/available}_(%)

Al Fe Mn Al Fe Mn Al Fe Mn

Asteraceae Baccharisreticularia 6285.4(1203.3)a _563212.2_(56447.7)b _999.5_(35.0)b _64.0_(22.0)ab _141.8_(56.5)a _73.5_(24.4)a _1.0 _0.03 _7.4 Eremanthuserythropappus 8217.9(597.1)a _416132.2_(106886.5)ab _784.5_(119.9)ab _123.6_(44.7)ab _327.7_(36.8)a _40.6_(11.7)a _1.5 _0.08 _5.2 Eremanthusincanus 5348.4(855.8)a _507384.8_(60941.4)b _1023.2_(104.5)b _44.7_(15.6)ab _110.2_(36.8)a _114.9_(109.2)a _0.8 _0.02 _11.2 Bromeliaceae Dyckiarariﬂora 12751.4(9474.4)a _440265.5_(74597.3)ab _851.5_(166.5)ab _98.8_(32.3)ab _303.0_(56.5)a _78.9_(35.5)a _0.9 _0.07 _9.0 Erythroxylaceae Erythroxylumgonocladum 7201.8(2322.2)a _420047.6_(125137.0)ab _803.6_(106.5)ab _55.3_(6.0)ab _225.0_(85.2)a _94.1_(44.7)a _0.8 _0.05 _11.7 Fabaceae Dalbergiavillosa 7082.6(621.3)a _341532.0_(183468.5)ab _683.6_(254.5)ab _68.3_(5.7)ab _264.8_(15.7)a _97.3_(39.8)a _1.0 _0.08 _14.2 Periandramediterranea 7083.5(5387.4)a _558038.0_(47726.4)b _1092.3_(149.1)b _61.0_(51.2)ab _113.0_(68.3)a _88.8_(92.1)a _0.9 _0.02 _8.1 Sennareniformis 7604.5(3322.4)a _512313.6_(9513.7)ab _916.3_(72.2)ab _55.0_(11.9)ab _284.3_(71.1)a _46.4_(29.6)a _1.2 _0.06 _5.1 Lythraceae Diplusodonbuxifolius 13036.5(9201.4)a _454268.6_(94321.1)ab _842.9_(162.2)ab _104.8_(26.5)ab _292.4_(66.3)a _62.4_(50.4)a _1.0 _0.07 _7.2 Malpighiaceae Byrsonimavariabilis 9225.8(2447.1)a _459082.7_(6243.2)ab _880.0_(151.0)ab _112.0_(26.0)ab _311.6_(54.9)a _62.8_(34.7)a _1.2 _0.07 _7.1 Heteropteryscampestris 11525.8(10672.2)a _510117.1_(47820.0)ab _956.7_(60.1)ab _82.2_(56.0)ab _196.4_(101.4)a _61.0_(51.1)a _0.7 _0.04 _6.4 Melastomataceae Leandraaustralis 8996.6(3437.5)a _438917.3_(36390.3)b _1019.5_(134.3)b _106.9_(53.8)ab _292.3_(96.9)a _120.5_(111.1)a _1.2 _0.07 _11.8

Miconiacorallina 6680.2(3296.2)a _512213.3_(37728.7)ab _939.3_(60.9)ab _87.5_(33.3)ab _305.1_(114.6)a _54.6_(30.0)a _1.3 _0.06 _5.8 Tibouchinaheteromalla 4493.1(1307.0)a _545136.2_(30249.4)ab _944.0_(158.9)ab _61.6_(30.3)ab _128.5_(76.2)a _40.6_(38.0)a _1.4 _0.02 _4.3 Myrtaceae Myrciasplendens 8624.0(2144.1)a _331760.3_(155576.5)ab _886.1_(419.8)ab _124.5_(54.9)ab _215.1_(202.9)a _226.7_(220.1)a _1.4 _0.06 _25.6 Ochnaceae Ourateasemiserrata 7901.3(1798.6)a _496348.3_(32505.6)ab _952.0_(121.9)ab _63.8_(17.8)ab _208.6_(77.1)a _116.9_(70.5)a _0.8 _0.04 _12.3 Poaceae Sporobolusmetallicolus 12751.4(9474.4)a _440265.5_(74597.3)ab _851.5_(166.5)ab _98.8_(32.3)ab _303.0_(56.5)a _78.9_(35.5)a _0.9 _0.07 _9.0 Sapindaceae Mataybamarginata 15278.4(8760.1)a _224707.4_(157606.6)a _488.8_(188.9)a _170.3_(90.3)b _418.8_(328.5)a _58.2_(22.3)a _1.1 _0.19 _11.9 Verbenaceae Lantanafucata 4301.5(789.9)a _495869.3_(54482.7)b _1078.7_(77.4)b _38.3_±_12.0a _84.3_(34.9)a _141.5_(73.3)a _0.9 _0.02 _13.1

Differentletterswithinthesamecolumnindicatesigniﬁcantdifferencesinaverageelementconcentrationamongspecies(Tukey0.05).

2.5. Statisticalanalysis

Data distribution was tested for normality using the Kolmogorov-Smirnoff test with 5% signiﬁcance. The compari-sonbetweenmean Al,Feand Mn concentrationsin leavesand intotalandavailablesoilfractionswasperformedusingANOVA followedbyTukeytestat5%.Thesigniﬁcanceoflinearregressions wastestedamongtheconcentrationsofelementspresentinthe soil (in the total and available fractions), among fractions and betweenleafconcentrationsandsoilfractions.Theprincipal com-ponentanalysis(PCA)wasusedforthespatialorderingofspecies bythestandard concentrationofsoil elements.The Minitab16 wasusedforthestatisticaltests.

3. Results

3.1. TotalandavailableAl,FeandMnsoilconcentration

The lowest total Fe and Mn concentrations (224,707.4mgFekg−1 and488.8mgMnkg−1)werefoundaround Mataybamarginata(Table1),whichwereatleasttwotimesand signiﬁcantlylowerthanthosefoundinsoilunderthecanopyofB. reticularia,E.incanus,P.mediterranea,H.campestris,T.heteromalla, M.corallinaandS.reniformis(consideringonlyFe),andL.australis andLantanafucata(consideringonlyMn).Meanconcentrationsof totalAl,andavailableFeandMninthesoildidnotdifferamong species.RegardingavailableAl,signiﬁcantdifferenceswereonly observedinsoilunderthecanopyofLantanafucata(38.mgkg−1) andM.marginata(170.3mgkg−1).

Total Fe and Mn concentrations were positively correlated (F=84.759,p<0.001).No othersigniﬁcantrelationship between totaloravailableconcentrationsofelementswasfound.Available Fe,AlandMnfractionsrepresent,respectively,only0.1%,1.1%and 9.9%ofthetotalfraction(Table1).

3.2. FoliarAl,FeandMnconcentration

Average foliar Al concentrations ranged from 46.6mgkg−1 (P. mediterranea) to 5794.6mgkg−1 (L. australis) (Table 2).The threeMelastomataceaespeciesshowedvaluessigniﬁcanthigher than those found in other species. The average Fe concentra-tionsshowedloweramplitudeamongspecies(from90.6mgkg−1 in O. semiserrata to 696.5mgkg−1 in S. metallicolus). Only this grassyspeciesdifferedsigniﬁcantlyfromotherspecies.Incontrast,

thisspecies showedthelowestaveragefoliarMnconcentration (331.9mgkg−1).SignificantlyhigherMnlevelswerefoundinonly threespecies,B.reticulata,D.rarifloraandL.fucata,whosemean valueswerehigherthan1606.4mgkg−1.Intheanalysisofspecies whose leafconcentrationsweredeterminedina single individ-ual,thelowestMnconcentrationwas100.5(P.sericiflora)andthe highestwas3935.1mgkg−1(A.albicans).

ApositivelinearrelationshipwasfoundinAlandFe concen-trationsinleavesbyexcludingthethreeMelastomataceaespecies fromtheanalysis(R2₌_0.77,_F₌_154.4,_p_<_0.001)._With_the_exception ofMelastomataceaeandC.coriaceum,whichaccumulated respec-tivelyfrom15.3to1.2timesmoreAlthanFe,alltheotherspecies haveaccumulatedonaveragetwiceasmuchFethanAlintheir leaves.Noothersigniﬁcantrelationshipamongleafelementswas found.

3.3. Soil-plantrelationship

Regressionsrevealednosigniﬁcantrelationshipbetweentotal andavailableconcentrationsofelementsinsoilandleavesofthe speciesunderstudy.Theconcentrationsofelementsinsoil, how-ever,segregatedspeciesorspeciesgroups,ascanbeseenbythe spatialordinationsobtainedbythePrincipalComponentAnalyses (PCA)(Fig.1).

PCAusing,respectively,totalandavailableAl,FeandMn con-tentsinsoilunderthecanopyofspeciesindicatedthatthefirst twoaxesexplained,respectively,95%and96%ofthetotalvariance. ThefirstaxisofPCAusingthetotalcontentofelementsexplained morethan78%ofthevariancefoundandwasstronglyand posi-tivelycorrelatedtoAlandFecontentsandnegativelycorrelatedto Mncontent.Mataybamarginataoccurspreferentiallyinsiteswith lowertotalMnconcentrations,whiletheoppositeisobservedforB. reticularia,E.incanus,P.mediterranea,H.campestris,T.heteromalla, M.corallinaandS.reniformis(Fig.1A).Inrelationtotheavailable concentrationoftheseelements,PCAindicatedthatMnandFeare positivelycorrelatedwiththefirstaxis(Fig.1B).TheavailableAl contentisnegativelycorrelatedwiththefirstaxisandstronglyand positivelyrelatedtothesecondaxis,segregatingM.marginatafrom theremainingspecies(Fig.1B).M.marginataoccursatsiteswith higheravailableAlconcentrations,incontrasttoL.fucataandE. incanus,whichoccurinlocationsoflowerconcentrationofthis ele-ment.D.villosaisassociatedwithsiteswithloweravailableFeand Mnconcentrations(Fig.1B).

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Table2

FoliarconcentrationofAl,FeandMn(meanandstandarddeviation)forthe27speciesofferruginousrockyoutcropslocatedintheSerradaBrigida,OuroPreto,MG,Brazil. (−)denoteslackofstandarddeviationdueton<3.

Family Species Elements(mgkg−1)

Al Fe Mn Asteraceae A.albicans 477.7(−) 983.4(−) 3935.1(−) B.reticularia 143.3(39.2)a _255.1_(51.8)ab _1606.4_(589.3)bcd E.erythropappus 212.1(41.0)a _352.8_(55.6)ab _835.9_(87.4)abcd E.incanus 73.6(7.1)a _195.3_(41.1)a _1240.7_(401.6)abcd Bromeliaceae D.rariflora 113.0(26.8)a _434.3_(191.2)ab _1929.4_(377.6)d Cyperaceae B.fimbriata 161.3(−) 376.2(−) 560.1(−) Erythroxylaceae E.gonocladum 80.2(29.3)a _176.3_(49.3)a _428.4_(78.4)ab Fabaceae C.coriaceum 466.8(−) 382.7(−) 164.5(−) D.villosa 148.9(62.1)a _214.9_(24.1)a _1438.3_(399.7)abcd P.mediterranea 46.6(11.2)a _174.9_(70.6)a _570.6_(345.5)abc S.reniformis 58.4(9.4)a _172.1_(6.4)a _854.2_(135.0)abcd Gesnenaceae N.strigillosus 246.5(−) 498.8(−) 249.2(−) P.sericiflora 519.8(−) 861.7(−) 100.5(−) Lythraceae D.microphyllus 146.0(25.1)a _154.7_(23.7)a _385.2_(113.3)ab Malpighiaceae B.variabilis 87.9(16.7)a _201.3_(32.1)a _360.6_(183.6)a H.campestris 244.3(1.5)a _424.7_(1.5)ab _1250.7_(1.5)abcd

Melastomataceae L.australis 5794.6(1913.1)c _379.6_(206.8)ab _1475.6_(537.1)abcd

M.corallina 2154.3(521.5)b _401.1_(90.6)ab _661.3_(175.2)abc

T.heteromalla 892.9(90.4)b _321.0_(51.1)ab _1017.9_(322.2)abcd

Myrtaceae M.splendens 144.0(96.1)a _203.6_(102.7)a _352.7_(55.0)a

Ochnaceae O.semiserrata 55.7(12.6)a _90.6_(14.8)a _1378.7_(753.0)abcd

Poaceae S.metallicolus 340.7(313.9)a _696.5_(500.1)b _331.9_(63.24)a Polypodiaceae P.hirsutissima 284.4(−) 576.0(−) 325.0(−) Pteridaceae D.ornithopus 280.5(−) 487.6(−) 194.0(−) Rubiaceae P.laricoides 241.7(−) 300.7(−) 297.3(−) Sapindaceae M.marginata 375.0(103.5)a _519.0_(112.6)ab _435.9_(372.6)ab Verbenaceae L.fucata 214.4(92.1)a _438.2_(113.6)ab _1758.5_(966.4)cd

Differentletterswithinthesamecolumnindicatesigniﬁcantdifferencesinaverageelementconcentrationamongspecies(Tukey0.05).

Fig.1. SpatialorderingdiagramofthetwoaxesofthePrincipalComponentAnalysisshowingthespatialorderingofspeciesinrelationto(A)totaland(B)availableFe,Al andMnsoilconcentration.Codeofspecies(seeAppendixA,Supplementarymaterial).

3.4. Biologicalabsorptioncoefﬁcient

WhenconsideringthetotalAlandFeconcentrationsinsoil,all speciesshowedenrichmentratioslowerthan1,beingclassifiedas excludingspeciesfortheseelements(Figs.2and3).Valuesgreater than1wereestimatedforMnin10outof19species(Fig.4),which wereconsideredMnaccumulators.However,usingtheavailable fractionofelementstocalculatethecoefficient,mostspecieswould beclassifiedas Al(15 species, Fig.2) and Feaccumulators (13 species,Fig.3),andallofthemMnaccumulators(Fig.4).CAB val-ues>1(Alavailable)rangedfrom54.1to1.1,andfrom5.2to1.1 (CABFeavailable)and24.5and3.0(CABMnavailable).WhileCAB valuesobtainedwithtotalandavailableAlcontentsseemtofollow apositivelinearrelationship,thesameisnottrueforFeandMn.

4. Discussion

Thesoil ofthestudyareais similartothose foundinother ferruginousoutcropsinsouthernBrazilandtypicallyclassiﬁedas dystrophic(CarmoandJacobi,2016;Messiasetal.,2013;Vincent andMeguro,2008.Factorssuchashighamountofironoxidesthat havelowCECinadditiontothelandslope,contributetothe leach-ingofessentialsoilnutrients.TotalFe,MnandAlconcentrations weremanytimeshigherthantheaveragevaluesofsoils world-wide(Kabata-Pendias,2011).Althoughonly0.1%,1.1%and9.9%, respectively,oftotalFe,AlandMnareintheavailablesoilfraction, theseconcentrationsexceedthelimitestablishedbytheBrazilian Agricultural Research Company (Ribeiro et al., 1999) for agri-culturalcrops(>45mgFekg−1,>12mgMnkg−1andexchangeable aluminum>1).Thisfactimposesrestrictionsontheestablishment ofsomespeciesinadjacentecosystemsunderdifferentchemical

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Fig.2. BiologicalabsorptioncoefﬁcientsofAlforspecies(n=3)oftheferruginousﬁeldofSerradaBrigida,MG,Brazil.ValuescalculatedwithtotalandavailableAlconcentration insoilarerespectivelyrepresentedbytheblackandwhitebars.Y-axisisinlogarithmicscale.BACvaluesnotlog-transformedaredisplayednexttothebars.Namesofspecies areabbreviatedaccordingtotheirinitials(AppendixA,Supplementarymaterial,Table2).

Fig.3.Biologicalabsorptioncoefﬁcients(BAC)ofFeforspecies(n=3)oftheferruginousﬁeldofSerradaBrigida,MG,Brazil.ValuescalculatedwithtotalandavailableFe concentrationinsoilarerespectivelyrepresentedbytheblackandwhitebars.X-axisisinlogarithmicscale.BACvaluesnotlog-transformedaredisplayednexttothebars andwerebelow0.01forallspecieswhenconsideringtotalBAC.Namesofspeciesareabbreviatedaccordingtotheirinitials(AppendixA,Supplementarymaterial,Table2).

soilconditions,asrockyoutcropsonquartzite(Messiasetal.,2013). Althoughthesemeansoilconditionsarenotrestrictiveforahigh diverseﬂoraofferruginousrockyoutcropsandprobablytoother plantsadaptedtoAl-richerlateriticsoils(butpoorerinFeandMn,

Haridasanand Araújo,1988), themetalvariationin microtopo-graphicscale,asperformedinthisstudy,suggestssegregationof speciesorgroupsofspecies.Fine-scalesurveysonrockyoutcrops

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Fig.4. BiologicalabsorptioncoefﬁcientsofMnforspecies(n=3)oftheferruginousﬁeldofSerradaBrigida,MG,Brazil.ValuescalculatedwithtotalandavailableMnsoil concentrationarerespectivelyrepresentedbytheblackandwhitebars.Y-axisisinlogarithmicscale.BACvaluesnotlog-transformedaredisplayednexttothebars.Names ofspeciesareabbreviatedaccordingtotheirinitials(AppendixA,Supplementarymaterial,Table2).

surfaceshaveprovedtobeastrongtoolforidentifyingpatternsof functionalgroupsdistribution(Carmoetal.,2016).

Thestudyareapresentedgreatspatialheterogeneityregarding totalandavailableconcentrationsofelementsinthesoilbelow thecanopies of thedifferent species, representing a mosaic of differentlandscapeoccupationopportunitiesforspecieswith var-iousdegreesofsensitivitytoabundantelements(Fe,MnandAl). Mataybamarginataseemstobethemostsensitivespecies,asit occupiedsiteswithlowerFeand Mnconcentrations,andatthe sametime,withhigherAllevels.TheAlconcentrationvaried3.6 timesbetweentheupperandlowerlimitsinthearea,andabout 2.5and2.2timesforFeandMn.Towhatextentthisvariationrange worksasaselectionfactorfortheestablishmentofspeciesoristhe resultoftheactionofthesespeciesonthephysicalandchemical soilpropertiesisstillcontroversial.Plantshavemechanismsfor selectivelyuptakingsoilchemicalelements,favoringthe absorp-tionofacertaingroupwhileavoidingothers,therebychangingthe relativeproportionsofsoilelements.Thisspecies-speciﬁceffect mightbeespeciallyrelevantinrockyoutcrops,whereingeneral, soilvolumesexploredbyplantsareverysmall.Insuchtypeof envi-ronments,soilmayonlyaccumulate discontinuouslyinshallow (usuallylessthan5cmindepth,Carmoetal.,2016)andsmallrelief depressions.Eachspotofreducedsoilvolumeundergo continu-ousinﬂuenceofrootsandlitterproducedbyinitiallyestablished plantspecies.Our resultsindicatepatternsofsoil-plant species relationship,butdonotallowmechanisticexplanationconcerning soilbiogeochemistrydynamics.EremanthusincanusandL.fucata arefoundonsoilpatcheswithlowerAlbutwithhigherMn concen-tration.BaccharisreticulariaoccursinsoilswithhigherFeandMn andlowerAlconcentrations,whiletheoppositewasobservedfor M.marginata.Dalbergiavillosa.E.erythropappusandE.gonocladum, whichoccurin soilswithlowerFeandMnconcentrations.In a naturalseleniferousarea,twohyperaccumulatorspeciesenhanced soilSeconcentrationswhilepreventingtheestablishmentof Se-sensitivespecies(Mehdawietal.,2011).Onthecontrary,thesoil

underthecanopyofT.heteromallaandM.corallina,twoAl accu-mulatorspecies,exhibitedlowerAlbuthigherFeconcentration. TheMelastomataceaehasbeenrecognizedashavingalarge num-berofAlhyperaccumulatorspeciesworldwide(Haridasan,2008; Jansenetal.,2002),however,thereisnoconclusiveevidenceabout theabilityof this familytosigniﬁcantly altertheAl concentra-tioninsoils.Incertainecosystems,litterfallmayrepresentamajor abovegroundinputofAltothesoilorganichorizon(Rustadand Cronan,1995).MostoftheAlremainsforlongperiodsimmobilized indecayinglitter,adsorbedontohumiccarboxylgroupexchange sites,andthus,AlaccumulatesovertimeintheO-horizon.Inthe Cerrado,thesoilAlavailabilitydidnotvaryoverfourstudiedyears eveninplotstreated withtwicethelitterbiomassfoundinthe untreatedarea(Villalobos-Vegaetal.,2011).

Mostspecies have beenconsideredexcluders, when consid-eringtheBACvaluescalculatedusingthetotalconcentrationsof soilelements(Baker,1981).However,whenconsideringthe phy-toavailableconcentration,thescenerychanges.Agradientoffoliar concentrationsand BACvalues is found,withBAC variationsof about8,12and87timesbetweenmaximumandminimumMn, FeandAlvalues,indicatingthecoexistenceoffunctionalgroupsof high,mediumandlowaccumulationorexclusioncapacity.Even amongthethreeMelastomataceaespeciesunderstudy,whichhad thehighestAlphytoextractionvalues,beingtwoofthem(L. aus-tralisandM.corallina)classiﬁedashyperaccumulatorsaccording toJansenetal.(2002,foliarAl>1000ppm),theBACavailablevalues variedwidely(14.5inT.heteromallaand54.2inL.australis).

Regardlessofnotbeingclassiﬁedashyperaccumulatorplants, foliarAl,MnandFeconcentrationsinseveralspeciesunderstudy arehigh,showingthattheyarenotfullyeffectiveinexcludingthese elementsfromaerialtissues,eveninthecaseofAl,whichisnotan essentialelement.Thus,thesespeciesareworkinglike accumula-torspecies,whereAlusuallyaccumulatesontheleafepidermisby transpirationstream(LeitenmaierandKüpper2013;Maltaetal., 2016).Curiously,althoughnospeciﬁcmetabolicroleofAlinplants

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hasbeendescribedsofar,somecommonplantspeciesofCerrado onlysurviveinthepresenceofexchangeablealuminum(Haridasan, 2008).Al+3_may_reach_about_two_times_higher_values_than_the_mean valuefoundinthestudyarea(HaridasanandAraújo,1988)anda considerablenumberofplantsaccumulatingmorethan1000ppm ofAlinleaveshavebeenfoundinCerradobiome(Haridasan,1982, 2008;HaridasanandAraújo,1988;Souzaetal.,2015).According toBressanetal.(2016)thepatternofAlaccumulationinleaves inassociationwithcellwallssuggeststhatAlhasstructuralrather thanphysiologicalrolesinCerradowoodyspecies,andthatAlis possiblyisolatedfrommetabolism.Ontheotherhand,withvery few exceptions,Cerrado plants accumulate much lowerFe and Mnconcentrationinleaves(MiattoandBatalha,2016)thanthose recordedinferruginousrockyoutcropspecies.

In thestudy area, manganese hyperaccumulation (foliarMn >10,000ppm,BakerandBrooks,1989)wasnotidentified,but val-uesexceeding400mg/kgwerefoundintheleavesof18ofthe27 speciesunderstudyinlevelsconsideredtoxicformostcultivated plants (Kabata-Pendias, 2011; Millaleoet al.,2010).Achyrocline albicansshowedaverageconcentrationofabout10timesthislimit. ThereareevidencesthatsomeplantspeciesbenefitfromMn accu-mulation(Millaleoetal.,2010).HighMnconcentrationshavebeen foundinspeciestypicalofdystrophicrockyfieldsandareassociated withastrategytoenhancephosphoruptake(Lambersetal.,2015). Inaddition,manganese,aswellasaluminum (Hajibolandetal., 2013),seemstohaveanegativeeffectonironuptakeinthesoil duetocompetitiveinhibitionbythesameabsorptionsite(Foyetal., 1978).Todate,nothresholdhasbeensetforFehyperaccumulation inplantsandleafconcentrationshigherthan500ppmsuggestFe toxicity(Marschner,2012).Amongthe27speciesstudied,onlyfive exceededthisconcentrationinleaves.Again,A.albicanspresented thehighestconcentration,983.4mgkg−1.

Theunderstandingofbiogeochemicalinteractionsamongsoil elements,thephysiologicalfunctionsandecologicalconsequences of their accumulation at different levels and in differentplant tissuesremaina current targetof scientiﬁc demandduetothe potentialuseofthisknowledgeinthephytominingand phytoex-tractionareasandintherecoveryofdegradedareas.

Theresultsfoundforthe27speciesunderstudyindicatethe co-existence, in ferruginous ecosystems, of different exclusion andaccumulationcapabilitiesof abundantand potentiallytoxic elementsin the soil,resulting in highcomplexity of ecological functionsmediatedbythemetal-plantrelationship.Insect-plant interactions(Behmeretal.,2005;Quinnetal.,2011;Ribeiroetal., 2017; Søvik et al., 2015) and interactions between plants and microorganismscanalsobemutuallyaffectedbythefunctional skills of accumulatingor excluding metals (Khan, 2005).Metal hyperaccumulationstrategydoesnotappeartobedominantinthe ﬂoraofferruginousrockoutcrops,similarlytothatobservedby Kramer(2010)indifferentecosystems.Thus,effortsforthe restora-tionofferruginousﬁeldecosystemsshouldbebasedonfacilitating theestablishmentofthegreatestpossiblenumberofspeciesand functionalgroupsofplants.

Acknowledgements

ThisprojectwassupportedbyFAPEMIG(APQ-02098-14)and CNPq (304224/2013-8). Antonella T. Schettini received CAPES scholarship.

AppendixA. Supplementarydata

Supplementarydataassociatedwiththisarticlecanbefound, intheonlineversion,athttp://dx.doi.org/10.1016/j.ﬂora.2017.05. 004.

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