Soilandvegetationpropertieson

reclaimedoilsandsinAlberta,Canada:asyntheticreview

ShuYaoWu

TheFacultyofForestry

TheUniversityofBritishColumbia(Vancouver)

April2015

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ExecutiveSummary The oil sands resource in Alberta represents vast economic opportunities

butalsodramaticenvironmental threat.Many researcheshavebeenconductedon

thepropertiesofreclaimedoilsandssoils.Thispaperintendstoprovideasynthetic

reviewof some conducted researcheson the soil physical, chemical andbiological

propertiesandvegetationcommunitydevelopmentinAlberta.Thispaperchoosesa

totalof20researches(from2003to2014)thatrestrictedtheirstudysitesintheoil

sands extraction regions in Alberta. Five of the researchesmainly focused on soil

physicalproperties,fiveonchemicalones,sixonbiologicalonesandanotherfouron

vegetation community responses. This paper found that reclaimed soils generally

havedifferentpropertiesinallphysical,chemicalandbiologicalaspectscompareto

natural soils. Prominent physical and chemical differences exist in organicmatter

content, soil nitrogen content and nitrogenmineralization rate. These differences

also lead to significantly different microbial community structures and organic

matter accumulation rate. In addition,mitigating effects of timeon soil properties

and vegetation communities were observed in this review. In the end, this paper

addresses themanagement implicationsand future research suggestionsbasedon

researches.

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TableofContents

ExecutiveSummary............................................................................................................................2

TableofContents.................................................................................................................................3

1.Introduction......................................................................................................................................4

1.1OilSandsEnvironment....................................................................................................4

1.2OilSandsExtraction..........................................................................................................6

1.3OilSandsReclamaition....................................................................................................9

1.4StudyObjetivesandMaterials...................................................................................12

2.ResearchFindings.......................................................................................................................14

2.1SoilPhysicalProperties................................................................................................14

2.2SoilChemicalProperties..............................................................................................21

2.3SoilBiologicalProperties.............................................................................................28

2.4VegetationCommunities..............................................................................................39

3.Discussion.......................................................................................................................................43

3.1ReclamationTreatmentEffects.................................................................................43

3.2ReclamationandManagementImplications.......................................................45

3.3LimitationsandFutureReseraches........................................................................46

References...........................................................................................................................................48

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1.Introduction

1.1OilSandsEnvironment

Oil sands refer to thebacteria-processedproducts ofmigratedbitumenmixed

withsanddeposits (Anderson2014).TheprovinceofAlberta inCanadapossesses

1.6trillionbarrelsofthistypeofbitumen,whichisthesecondlargestoilreservein

the world and can supply Canada’s energy demands for next 475 years (Chastko

2004). These oil reserves spread in three regions of Alberta: the Athabasca, Cold

Lake and Peace River (Figure 1) (Canadian Boreal Initiative 2005). Among these

three,theAthabascaregionislargestinsize(graterthan48,000km2)andcontains

thelargestvolumeofbitumen.Theestimatednumbervariesfrom170billionbarrels

to700billionbarrels(FungandMacyk2000;Hrudeyetal.2010).

Figure1.Thelocationsofthreemajoroilsandsreserves(theAthabasca,ColdLakeandPeaceRiver)inAlberta,Canada.(Wikipedia2006).

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Thethreeoilsandregionsarealllocatedintheborealforestzone,whichisone

ofthelargestintactecosystemsintheworld(CanadianBorealInitiative2003).The

boreal forest in Alberta covers an area of 346.964 km2, which represents

approximately 52% of province’s land base (Alberta Environmental Protection

1998).Ahighlydiverse floraland faunalspeciescompositionandstructurecanbe

foundinthislargeecologicalbiome.Inaddition,theborealforestprovidesanarray

of ecosystem services include water filter and storage, flood mitigation, carbon

sequestration,nutrientcyclingandfoodandshelterprovisionforbothanimalsand

human (Leatherdale 2008). This forest also provide many important economic

resources such as wood products, agricultural lands and oil and gas are also

provided to humans by this forest (Canadian Boreal Initiative 2005). All of these

products and services from the boreal forest support thousands of jobs and

contributebillonsofdollarstoAlberta’seconomyannually(Leatherdale2008).For

example, the investment for oil sands industry reached $17.2 billion in 2010; the

royaltiesfromoilsandscompaniestothegovernmentofAlbertareached$3.7billion

in the same year; approximately 151,000 Albertans are directly employed in this

industry(GovernmentofAlberta2013).

Due to thehigh latitude, the climate inAlberta’s oil sands regions is generally

harsh.Theannualgrowingseasondonotstartuntilthegroundsurfacethawsinlate

MayorearlyJuneandonlylastsabout95daystillSeptember(Rowland2008).The

average temperatures range from -22 °C to +17 °C and the annual mean

precipitation is about 470 mm, 300 mm of which comes as rain (Visser 1985;

Rowland 2008). Common vegetation species that can be found in boreal forest

includeaspen (Populus tremuloides and Populusbalsamifera), spruce (Piceaglauca

andPiceamariana), jackpine(Pinusbanksiana), fir(Abiesbalsamea)andtamarack

(Larix lariana) (Rowe, 1972). Other than forest, bog and fen peatlands and

freshwaterwetlands,which cover an area of 20% to 60%of the oil sandsmining

regions,arealsomajortypesoflandscapesoftheborealecosysteminAlberta(Vittet

al.2000).

Theparentmaterialsofoilsandssoilsoriginatedfromthedeltadepositsofan

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ancient tropical sea and were compressed by glaciers during glaciation period,

whichgivesthesoilsfinetexture(Rowland2008).Thesedepositsareconsolidated

and highly sodic and saline (Purdy et al. 2005). There is no single dominant soil

order or subgroup in the oil sands regions but a range of Orthic Brunisols,Mesic

Fibrosol, Orthic or Gleyed Luvisols, and Gleysols (Table 1) (Oil Sands Vegetation

ReclamationCommittee,1998).Thiswiderangeofsoilorderiscausedbydifferent

amountofclay-impededwateranddifferentamountofleachclayinsoils(Rowland

2008). This assortment in the soil ordermakes the soilmoisture gradient to vary

from xeric to subhydric and the oxidation condition to vary from aerobic to

anaerobic.Inaddition,thepeatandpeat-likesoilusuallycanbefoundatsoilsurface

(Stolteetal.2000).

Table1.CommonlyfoundnaturalsoilsintheoilsandsregionsinAlberta.

Name GeneralDescriptionsOrthicBrunisols

Poorlydevelopedmineral-organichorizon.NoBtorBphorizon HighdegreeofbasesaturationParentmaterialsusuallyhavehighbasestatus Commonlyfoundunderforestandshrubvegetation

Orthic GrayLuvisols

Well-developed Ae and Bt horizion plus an organic surfacehorizonusually FaintmottlingmightbefoundnearorwithinBthorizon Parentmaterialsarecommonlybasesaturatedandcalcareous Solumisusuallyacid

MesicFibrosol Deep,relativelyundecomposedfabricmaterial Parentmaterialisorganicmatterandclay-richglacialtill Highpercentageoforganicmatter(>30%) Occurinbogsandfens

Gleysols Lackofwell-developedmineral-organicsurfacehorizon,suchasAhorAp GleyedBorChorizonUsuallyoccurinpoorlydrainedareas

Sources:TheCanadianSystemofSoilClassification1998;Rowland2008.

1.2OilSandsExtraction

Thehistoryofpeopleusingthebitumendepositionisquite long.Inthepast, it

was traditionally used by First Nations to patch canoes (Hrudey et al. 2010). The

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modern commercial oil sands industry in Alberta started slowly but expanded

rapidly(Chastka2004).Nowadays,therearedozensofoilsandscompaniesworking

in the Alberta oil sands regions (Canadian Oil Sands Navigator 2015). The major

three companies are Syncrude Canada Ltd, Albian Sands and Suncor Energy Inc

(Rowland2008).Open-pitminingand insituextractionarethetwomainoilsands

extractionmethodsthesecompaniesareusing.

Theopen-pitextractionmethodcanonlybeappliedinareawheretheoilsands

oreisclosetosurface(Figure2)(Anderson2014).Thefirststepofsurfaceminingis

the removalof all vegetation, soils andnon-orehorizonsabove thedeposit.These

materialsareusuallyreferredas“overburden”andhavedepthsrangefrom1mto

over70m(Hrudeyetal.2010).Thesematerialsareusuallystockpiledsomewhere

close by, sometimes formany years, before theywere used in future reclamation

(Mackenzie2011).

Figure1.Open-pitoilsandsmininginAlberta(NationalGeographic2011).

However, for approximately 80% of Alberta’s oil sands areas, the bitumen

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deposits are too deep for the open-pit mining method and the in situ extraction

methodneedtobeapplied(RAMP2015).Currently,themostcommonlyusedinsitu

methodistheSteamAssistedGravityDrainage(SAGD)(Figure3).Thismethoduses

two drilled horizontal wells, one above the bitumen deposit and one below. The

abovewellpumpsheatedsteaminordertomeltandpressbitumenintothelower

well, fromwhichthebitumenistransporteduptothesurface.Water is injectedto

replacetheextractedbitumenforstabilizationpurpose(RAMP2015).

Oncetheoilsandsdepositsareextracted,eitherfromopen-pitorinsitumethod,

they are transported to a facility that separates the bitumen and the sand before

theywereupgradedintopetroleum(Rowland2008).TheClarkhot-waterextraction

method,whichuseshotwaterwithaddedsodiumhydroxide(NaOH),isusedinthis

separation process (Rowland 2008). The ejected sands (more specifically 95±1%

sand, 4% silt and 1% clay) and water became tailings, which transformed from

moderately acid (pH 5.5-6) to alkaline (pH 7.5-8.5) due to the added chemicals

(Visser1985).Theioniccontent,suchassodium,sulfateandchlorideionsarealso

high in these tailings (Renault et al. 1998). These tailings sands will leave for

settlement and freely drained. The large particles settle out much more quickly

comparetosmallerones.Thefineparticlescantakeverylongtime,evenhundreds

of years, to settle because of thehigh ionic content (Renaultet al. 1998). Gypsum

(CaSO4) is added sometimes as a consolidation agent to accelerate the settlement

processofthefineparticles(LiandFung1998).

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Figure2.Schematicof theSteamAssistedGravityDrainage(SAGD) insitubitumenextractionmethod(thePembinaInstitute2005).

There are three main types of waste materials generated from the bitumen

extractionandproductionprocess,whichareoverburdenmaterial,tailingsandand

finetailings(FungandMacyk2000).Overburdenreferstothematerialsthatoverlay

the oil sands deposits and contain low-grade oil sand, glacial till, glacial-fluvial,

glacial-lacustrine and peat material. Tailing sands and fine tailings are both the

remainingwasteproductsafterbitumenextraction.Tailingsandsaremadeof96to

99percentsandysilicaandtheresidualbitumen.Nevertheless, finetailingsmainly

consistofclay,siltsandresidualbitumen(FungandMacyk2000).

1.3OilSandsReclamation

Itismandatoryfortheoilsandindustrytohavethedisturbedlandsreclaimed,

re-vegetatedandcertifiedbytheGovernmentofAlberta.However,thegovernment

doesnotrequireanexactidenticalconditionbutonly“anequivalentlandcapability”,

whichisdefinedbytheLandCapabilityClassificationSystem(LCCS)as“theabilityof

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the land to support various landusesafter conservation similar to theability that

existed prior to an activity being conducted on the land” (CEMA 2006). The

government regulator that is responsible for oil sand lands reclamation oversight

and final certification is the Alberta Environment and Sustainable Resource

Development.AccordingtotheLCCSfieldmanual, therearethreekeyfactorsneed

to be addressed in order to achieve high land capability, which are minimal salt

impacts(<4.0dS/msalinityEC,<8.0SodicitySARand<7.5pH),sustainednutrient

cyclingandsufficientavailablewater-holdingcapacity (CEMA2006).Furthermore,

vegetationcommunitymustalsobedevelopedinthesitesinordertobecertifiable

assuccessfulreclamation.Someindicatorsforsuccessfulvegetationreestablishment

includeplantcommunitycomposition,netprimaryproductionoftheecosystemand

soilsalinity.

The first step of reclamation is the replacement of the removedmaterials or

reconstructing the soil. As guided by the above legal requirements, an ideal

soil-formingmaterial should have 1) the ability to supply water and nutrients to

plants;2)theadequatestabilitytoresisterosionbutalsoenablerootdevelopment

and;3)theabilitytobufferenvironmentalchanges(Rowland2008).Variouskinds

ofminingresidualsarecommonlymixedandusedasreclamationmaterials,suchas

peat-mineralmix,tailingsands,topsoil,subsoil,overburden,leanoilsandandmine

by-products(Table2)(Rowland2008;Hrudeyetal2010;Mackenzie2011).

Althoughthere isnouniversalormandatoryprescriptionofhowthecompany

shouldreconstructasoil, fiveoutof thesevenpopularprescriptions includeusing

peat-mineral mix as a part of the reclaimed soil (Rowland et al. 2009). The

popularity of peat is not only because of its high abundance in the boreal forest

region inAlberta, but alsobecausepeatmay improveorganic carbon content, soil

nutrient and water retention capacity (Rowland 2008). As a pratical example,

SyncrudeCanadaLtd.spreadsapproximately15cmofpeatwith20cmofmineral

soilastop layerforplantgrowth.Beneaththis layer,anupto80cmdeepcapping

layer that contains amixture of lean oil sands and overburden is used to prevent

waterandplantpenetratingtounderneathtoxicmaterials(Figure4).

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Table 2. Descriptions of some common materials used for soil reconstruction inAlberta’s oil sands regions (Mossop, 1980; Danielson et al. 1983; Hardy BBT Ltd.1990;RungandMacyk2000;Rowland2008).

Name Originanddescription

Principlemineralcomponent

Physio-chemcialproperties

Peat-mineral Strippedandmixedfromborealbogs

Clayloamorclay 2–17%organicC;Near-neutralpH;P:Mratiovaries3:2to3:4byvolume

Tailingsands MarinesandswithsomeshalebedsfromCretaceous-era

95%sand(quartz),4%silt(feldsparandmica)and1%clay(kaolinite,illiteandmontmorillonite)

Hydrophobicafterair-dryingNilplantnutrientsErosion-proneHigherosionpotentialLowavailablewaterholdingcapacity,cationexchangecapacity,microbialactivityandorganicC

Subsoil BandChorizonofborealforestsoil

Silt-clayandclay(kaolinite,illiteandmontmorillonite)

pH5.0–8.0Non-saline<2%organicC

Overburden SedimentarydepositsfromCretaceous-eradriftedbyglacialfromPleistoceneEpoch

Silt-clayandclay(kaolinite,illiteandmontmorillonite)

pH8.0+Non-salineNilorloworganicCLowavailablewaterholdingcapacity,microbialactivity,nutrientstatus

Leanoilsand Cretaceous-eramarinesedimentswithmigratedbitumen

Sandswithsomeshales,siltsandclays

<6%bitumenbyweightpH5.5–6.0

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Figure3.Schematicrepresentationofoilsandsreclamationprescriptionsfromthreeoil sands companies in Alberta, Canada (Oil Sands Vegetation ReclamationCommittee1998;AMECandParagon2005;Rowland2008).

Intermsofvegetationrestoration,Hordeumvulgare(barley) isusuallyplanted

asacovercropinitiallytoprotectsoilandcontrolerosion.Additionally,barleycan

add organic matter and nutrients to the soil as well. Since barley is a poor

competitor, they will also be easily replaced by more desired species afterwards

(Rowland2008).Inthelate1980’s,companiesstarttoadaptnaturalre-colonization

insteadofdirect seeding.However,on somesites,particularly for those reclaimed

for forestrypurposes, treeplanting, such as jackpine, balsampoplar,white birch,

white spruce and aspen, is still used (Rowland 2008;Alberta Environment 2009).

Shrubspecies, suchas rose, low-bushcranberry,dogwood, raspberry, greenalder,

Canada buffalo-berry, Saskatoon, blueberry, bog cranberry and bearberry, are

replanted too (Alberta Environment 2009). Mixed nitrogen, phosphorous and

potassiumfertilizerareusedalmostinallsitesinthefirstonetofiveyearsinorder

toacceleratethevegetationestablishment(Hrudeyetal.2010).

1.4StudyObjectivesandMaterials

Upto theyearof2012, therewere715km2havebeenexploited foroil sands,

however, only 1 km2 of which has been successfully reclaimed and certified

(Anderson 2014). Despite the significant economic profits oil sands brought to

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Alberta,theenvironmentalcostsofexploitingoilsandsongreenhousegasemissions,

air and water quality, are also becoming more and more tremendous. In 2010,

approximately48million tonesofgreenhousegasemissions inAlbertaarecaused

by oil sands exploitation (Anderson 2014). Critiques of the effectiveness and

authenticity of oil sand reclamation are also keep arising (Grant et al. 2008). The

earliest reclaimedsiteshavealready turned intoover30-year-old.Moreandmore

researches have been conducted in order to study the reclaimed oil sands soil

properties in Alberta. This paper intends to summarize some of the conducted

researchesonphysical,chemicalandbiologicalpropertiesofreclaimedoilsandsoils

and vegetation community development status in order to provide a synthetic

review to other researchers, compare reclaimed soils with natural soils, propose

reclamationandmanagementsuggestionsandidentifysomepotential futurestudy

focuses.

A total of 20 researches that have their study sites in the oil sands extraction

regionsinAlbertawerechosen.Theseresearchesfocusedmainlyeitheronphysical

(5),chemical (5),biological (6)soilproperties(somestudiedmixedproperties)or

vegetation growth (4) on reclaimed oil sands sites. Data were utilized from 12

publishedpeer-reviewedjournalarticlesand8masterthesisworkrangefrom2003

to2014.Each study isbriefly retoldby its studyobjectives,methods, key findings

andimportantdiscussionpoints.

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2.ResearchFindings

2.1SoilPhysicalPropertiesTable 1. Summary of discovered physical properties and their descriptions ofreclaimedoilsandssoilsinAlberta,Canada. Studies(Year)

Properties Findings

Yarmuch(2003)

Texture

-Topsoilsrangefromloamtoclayloamtosiltyclayloam(siltloamtoloaminnaturalsoils)-Subsoilsrangefromsandyclayloamtoclayloamtosiltyclayloam(clayloamtoclaytoheavyclay) -Muchmoreorganicmatterintopsoillayercomparetothatofnaturalsoils-Subsoilsaremoresimilarbutcontainlessclay

Bulkdensity

-Lowerinreclaimedtopsoilcomparetonaturalsoils -Higherinyoungtopsoilandlowersubsoilthaninoldreclaimedsoils-Nosignificantdifferencesbetweenyoungandoldreclaimeduppersubsoils

Fieldsaturatedhydraulicconductivity

-Nosignificantdifferenceneitherbetweennaturalandreclaimedsoilsnoryoungandolderreclaimedsoils

Porosity

-Highermacro-,meso-andmicro-porosityinreclaimedtopsoilthanthatofnaturalsoils -Moremacroporesandlessmicroporesinreclaimedsubsoilsthanthatofnaturalsoils- Moremicroporesinyoungreclaimedsoilsthaninoldones

Leatherdale(2008)

Soilmoisture

-Slopepositionsdidnotsignificantlyaffectsoilmoistureregime-Soilsthathavehigheramountoforganicmatterholdhigherplantavailablewater

Soilnutrient(chemicalproperty)

-Ahighdegreeofvariabilityofsoilnutrientsacrossslopepositions-Seasonappearedtobemoreinfluencingthansiteconditionsonnutrientavailability

TritesandBayley(2009)

Organicmatteraccumulation

anddecompositioninwetlands

-Biomassaccumulationnegativelyrelatestopollutantsbutpositivelyrelatestowaterdepthbutstilllowerthannaturalwetlandsduetohighsalinity-Similarlitterdecayratesbetweennaturalandreclaimedwetlands

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Hunter(2011)

Waterrepellency

-Highvariabilityofwaterrepellencyexistswithinbothreclaimedandnaturalsites-Surfacereclaimedsoilsappearedtohavehigheraveragewaterrepellencythansubsurfacesoils-NosignificantdifferencesfoundbetweentheRIvaluesofsurfacereclaimedandnaturalsoils

Anderson(2014)

Organicmattercontent

-Higherorganicmatterinreclaimedsoilsthannaturalsoilsmainlyduetopeat

Sourcesoforganicmatteraccumulation

-DominanttreetypeisthemostinfluencingfactorofSOMaccumulation-Rootandmacrofaunalbioturbationdominatedassourceingrasslandtreatment-Dissolvedorganicmatterfromforestfloorandmacrofunalactivitydominatedindeciduoustreatment-Nosignofaccumulationinnaturalandreclaimedsprucesites

Organicaccumulation

rate

-Highestindeciduoussites,moderateingrasslandsitesandslowestinsprucesites-Theordercorrespondswiththediversityoforganicmatterinputandthelevelsofmacrofaunalbioturbation

Yarmuch(2003)–MeasurementofsoilphysicalparameterstoevaluatesoilstructurequalityinreclaimedoilsandssoilsAlberta,Canada: Yarmuch(2003)studiedarangeofcommonsoilphysicalpropertiesinorderto

access the structurequalityof reclaimedoil sands soils in theAthabascaoil sands

region. The author also compared the soil physical properties among naturally

disturbedsitesandreclaimedsiteswithdifferentages.Ninenaturallydisturbedsites

and27sitesindisturbedareaswereselected.Soilpitsweredugandsampleswere

collectedwithinthreesoillayers:topsoil(0-20cm),uppersubsoilandlowersubsoil

inreclaimedsoilsandLFH,A,BandBCorChorizonsinundisturbedsoils.Physical

propertiesthatwereanalyzedincludedparticlesizeanalysis(hydrometermethod),

soilbulkdensity,fieldsaturatedhydraulicconductivity(GuelphPermeameter),pore

size distribution and available water holding capacity (the water columnmethod

andpressureplateapparatus).

The texture of the upper subsoil and the lower subsoil of

peat-mineral-mix/overburdenreclaimedsoilswasfoundtorangefromsandyloam

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tosandyclayloamtoclayloam.Thecomparisonofsoilphysicalpropertiesbetween

reclaimedoilsandssoilsandnaturallydisturbedsoilsshowedthatthetextureofthe

topsoilhorizonwasmuchdifferent thanthenaturallydisturbedAehorizondueto

high organic matter from the peat amendments. However, the upper and lower

subsoilsofreclaimedsoilshadaslightlylowerproportionofclaysizeparticlesthan

thenaturallydisturbedBtandBC/Chorizonsdo,respectively.

Themean bulk density of the reclaimed topsoils was significantly lower than

thatof thenaturallydisturbedAehorizon.But thedifferenceswerenotsignificant

between the upper and lower subsoil horizons and the corresponding naturally

disturbed soil horizons. In addition, therewereno significantdifferencesbetween

the field saturated hydraulic conductivity of the topsoil, the upper and lower

subsoilsandtheircorrespondingnaturalhorizonseitherinmostinstances(fiveout

of the seven comparisons). This might be attributed to the low-impact reclaimed

techniques that the oil sands industry adopted, such as lightweight equipment,

wheeled and tracked equipment and freezing reclaimed materials beforehand to

makesoilaggregatesmorerigid.

In term of total porosity, all the macro-, meso- and micro-porosity were

significantly higher in the reclaimed topsoils than that in naturally disturbed Ae

horizons.Moremacroporesandlessmicroporeswerefoundinthereclaimedupper

andlowersubsoilscomparetothenaturallydisturbedcorrespondinghorizons.This

is likely due to the higher sand proportions in the reclaimed horizons and the

greater proportions of clay in the naturally disturbed soil horizons. In the end,

Yarmuch (2003) concluded that reclaimed soils donot possess limiting structures

comparetothatofnaturalsoils.

Soil physical properties were also compared among reclaimed soils with

differentages.Itwasfoundthatreclaimedyoungtopsoilandlowersubsoilhorizons

hadhigherbulkdensities thanoldones.Thedifferencesofbulkdensitiesbetween

youngandolduppersubsoilhorizonswerenotsignificant.Inaddition,therewasno

significant difference found in the field saturated hydraulic conductivity, total

porosityandamountofmacro-,meso-andmicroporesbetweentheoldandyoung

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reclaimed soils either. However, there were significantly higher amount of

macropores and lower amount ofmesopores in the youngupper subsoil horizons

than in theoldones. Yarmuchexplained this observationbynatural settlementof

soilmaterialovertime.Inconclusion,theauthorstatedthatthereislittlechangein

soilphysicalpropertiesinapproximately20yearsandreclaimedsoilstructuresmay

bestableorchangeveryslowly(decadestocenturies).

Leatherdale(2008)–SoilmoistureandnutrientregimesofreclaimeduplandslopesintheoilsandsregionofAlberta:

TheobjectiveofLeatherdale’sstudyistoquantifythesoilmoistureandnutrient

regimes of reclaimed soils. More specifically, the author wanted to answer how

topographical position affect soil moisture and nutrients and determine the

temporal variability of soilmoisture andnutrients at slope levels. Five study sites

were selected approximately 50-80 km north of Fort McMurrary in northeastern

Alberta.Meteorologicalparameters(weatherstation),soilmoisture(Diviner2000®

accesstubes),topsoil,uppersubsoilandlowersubsoilsampleswerecollectedinthe

field.Inlaboratory,bulkdensity,soilwatercharacteristiccurves(usepressureplate

apparatus), particle size distribution (use hydrometer method) and total organic

carbon(usedrycombustionmethod)weredetermined.

The results showed that themoisturecontentswerenot significantlydifferent

acrossthelower,midandupperslopepositionsonthereclaimeduplandsoils.This

was explained by the heterogeneity in soil properties, such as peat-mineral mix

depth and distribution, vegetation spatial patterns or relatively gradual slope

gradients(lessorequalthan25%).Soilsthathavehigheramountoforganicmatter

holdhigherplantavailablewater.Inaddition,theinfiltrationrateswerefoundtobe

higher in soils that have greater fraction of coarse textured material in their

peat-mineralmixlayer.Themoistureregimesofuppersoilprofilesinmostsiteshad

quickresponses toprecipitationevents,exceptonsites that lackofvegetationand

havehydrophobicproperties.Soilswithlessfinertexturedmaterialsaresubjectto

percolation.South-andwest- facingsites lostormaintainedsoilwateroverwinter

whilenorth-facingsitesgainedsoilmoistureoverwinter.Thismightbebecauseofa

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combination of less incoming solar radiation on north-facing slope and the

water-holdingeffectofvegetation.

In terms of soil nutrient regimes, a high degree of variability in nutrient

availabilitywasfoundacrosstheslopepositions.Theauthorexplainedthisthrough

vegetationpatchdynamicsanddifferentspatialdistributionsofvegetationspecies.

Season appeared to be amore influencing factor of nutrient availability than site

conditions. Similarity in seasonal nutrient availability was found between some

reclaimedsoilsandnaturallydisturbedsoils.

Trites and Bayley (2009) – Organic matter accumulation in western boreal salinewetlands:acomparisonofundisturbedandoilsandswetlands:

Since thewetland isalsoadominantpre-disturbance landscape type inAlbert

oil sands region, oil sands companies are required to reclaim some sites back to

wetlandsevenafterthesalinityiselevated.Therefore,TritesandBayleywantedto

measureandcomparetheproductionrates,decompositionratesandorganicmatter

(OM)accumulationpotentialinreclaimedwetlandsandinnaturalwetlandsacrossa

salinitygradientinordertoevaluatethepotentialofreclaimedplantstoaccumulate

peat under future oil sands reclamation scenarios. Three reclaimed oil sands

wetlandsandsixnaturalwetlandswereselectednearFortMcMurray,Alberta.Total

carbon, nitrogen and phosphorus of soils, aboveground wetland production,

decompositionrate(litterbagtechnique),C:N:PratioinabovegroundlitterandOM

accumulationpotentialweremeasuredorestimatedinonetotwovegetationzones

ateachwetland.

Itwasfoundthemeanannualtotalbiomassproductioninthisstudywasabout

502 g m-2 and the production rate negatively related to salinity. Negative

relationshipwas found between pollutants, such as NH4+or naphthenic acids,and

biomasswhilepositiverelationshipwasobservedbetweenwaterdepthandbiomass,

which indicated the important role of the water availability played in successful

vegetation reclamation. High water level can also decrease the oxidation rate of

accumulatedpeat.Inaddition,TritesandBayleyalsoobserveddifferentdecayrates

for different litter types but same decay rates between oil sands and natural

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wetlands.OnlyweakcorrelationwasfoundbetweendecayratesandtheC:Nratios

ofabovegroundplanttissuesandnocorrelationwasobservedbetweensalinityand

litterdecompositionrates.

After comparing the organic accumulation and decomposition rates, a net

average annual organic matter accumulation of 307 g m-2 and production to

decomposition quotients ranged from 2.0 to 3.8 were obtained across both

reclaimedandnaturalwetlands.Thequotientvaluesweremuchlowerthanaverage

borealbogs(7.1)butsimilartotheonesfrompoorandmoderate-richwoodedfens

(3.6-4.0). Peatlands that were dominated by Schoenoplectus tabernaemontani and

Trigiochinmaritimageneratedthehighestratios,whichimpliedahigherpotentialto

accumulate OM since these species had slower decomposition rates. The slower

biomass decomposition rates compensated the salinity-induced slow production

ratesandgaveoilsandswetlandsrelativelyacceptablepeataccumulationrates. In

the end, the authors concluded that reclaimed oil sands wetlands had peat

accumulation if theconditionof sufficientwater leveland lowpollutantswasmet.

However,ingeneral,thepeataccumulationratewouldstillbeataslowerlevelthan

innaturalwetlandsinthelongterm.

Hunter (2011) – Investigation of water repellency and critical water content inundisturbed and reclaimed soils from the Athabasca oil sands region of Alberta,Canada:

Hunteraimstoquantifythedegreeofnaturallyoccurringwaterrepellencyand

thepotentialof severewater repellency in reclaimedsoils. Inorder todo this, the

author selected a total of ten sites (four reclaimed and six natural sites) in the

Athabasca oil sands region and examined the mineral and organic reclamation

materials,peat,mineral soil, forest floor in these sites. Soilwater repellency index

(RI)weregatheredbyusingstandardandmini infiltrometers.Othermethodssuch

as the water droplet penetration time test (WDPT) and the molarity of ethanol

droplettest(MED)wereusedalongwiththeinsiturepellencyindextoestimatesoil

waterrepellency.Thecriticalwatercontentofreclaimedsoilswasalsodetermined

throughmeasuringthecontactangle(CA)andWDPT.

20

The results from both standard and mini inifltrometers suggested that high

variability ofwater repellency existswithin both reclaimed and natural sites. The

meanRIvaluesfromtheminiinfiltrometers(9.61)werehigherthanthosefromthe

standard ones (3.46) but the differenceswere not statistically significant inmost

sites. TheWDPT and MED tests also demonstrated similar trends of high spatial

variabilityofsoilwaterrepellency.Thesurfacereclaimedsoilsappearedtohavea

higheraverageRI than the subsurface soils.Nevertheless, therewasnosignificant

differencesfoundbetweentheRIvaluesofthesurfacereclaimedandnaturalsoils.

The results of the critical water content showed that reclaimedmineral soils

weregenerallywettableabovegravimetricwatercontentsof5 to10%.Subcritical

waterrepellencyoccurredinthematerialsthatwereaffectedbythecoarsetextured

tarball. In addition, therewas a clear positive relationship between the degree of

waterrepellencyandthedecompositionlevelsofpeatmaterials.Furthermore,peat

and LFH layers had no relationship betweenwater content andwater repellency.

Finally,Hunter concluded thatwater repellencymightnot be amajor issue in the

Athabascaoilsandsregion.

Anderson(2014)–Organicmatteraccumulation inreclaimedsoilsbeneathdifferentvegetationtypesintheAthabascaoilsands: Anderson researched three aspects of the soil organic matter (SOM) in

reclaimed oil sands soils, which were the organic matter content, the dominant

sources of organicmatter and the organicmatter accumulation rates. The author

selected five aspens sites, five spruce sites and five grassland sites that ranges

between20to36yearsoldandarelocatedintheuplandAthabascaoilsandsregion.

Five nearby natural sites with similar moisture and nutrient regimes were also

selected. The author tested and analyzed measurements include the bioturbation

levels,therootabundancesandtheorganicmattercontents.

Itwasfoundthatthereclaimedsoilshadconsiderablyhigheramountoforganic

matter than the natural soils probably due to the abundant peat used during

reclamation.Reclaimedpeat-mineralmixsoilswerefoundtohavehighercapacityto

stabilizedissolvedorganicmatters,whichledtoanincreasedresidencytimeofSOM

21

in soil profiles. This might be attributed to the higher pH and higher polyvalent

cations contents in peat. This increased residency time of SOM along with fresh

organic matter input probably both contributed to the accumulation of SOM in

reclaimedsoils.

The sources of SOM accumulation depend on the planted vegetation. For

example, root andmacrofaunal bioturbationwere the dominating SOM sources in

grassland, while in deciduous treatment sites, dissolved organic matter from the

forest floor andmacrofaunal activity dominated as sources. Therewas no sign of

activeSOMaccumulationinnaturalsitesandreclaimedsitesthatwereplantedwith

spruces.Astrong inverserelationshipbetweensoildepthandSOMconcentrations

wasfoundindeciduoussites,whichwasan indicatorofdownwardmovinghumus

compounds. It was concluded that dominant tree type was the most influencing

factorofSOMaccumulation.

In terms of the forest floor development, grassland and deciduous sites had

significantly thicker forest floorandmoremacrofaunalactivities thansprucesites.

Theseprobablyattributedtothehigherquantitiesandbetterqualityoftheorganic

matterinputinthesetwotypesofsites.Lastbutnotleast,itwasfoundthattheSOM

accumulation ratewashighest indeciduous sites,moderate in grassland sites and

lowestinsprucesites,whichcorrespondwiththediversityoforganicmatterinput

andthelevelsofmacrofaunalbioturbation.

2.2SoilChemicalProperties

Table 2. Summary of discovered chemical properties and their descriptions ofreclaimedoilsandssoilsinAlberta,Canada.Studies(Year)

Properties Findings

Rowland(2008)

SoilpHlevel-Almostallsites,exceptforonehadhigherpHthannaturalecotypesbecauseofthenatureofreclamationmaterials

Insitubio-availablenutrients

-HighamountofNO3—NandlowC:Nratiowasfoundinallreclaimedsitesdespiteagesandfertilizerapplication-MicronutrientNawaslowonallreclaimedsites

22

becauseofdispersalofNafromclaysbytheadditionofgypsumandleaching

Litterinputandorganiclayerdevelopment

-LitterdecompositionrateandtheFHlayerdevelopmentrateweresloweronreclaimedsitescomparethoseofnaturalsites-Approximatelyatleast25yearswasrequiredtohavereclaimedplantcommunitiessimilartonaturalones

Moisturecontent(physicalproperty)

-Thepresenceoftailingsandsdecreasemoisturecontent.-Thepresence/absenceofplantrootactivitydidnotaffectmoisturecontent

Plantcommunitydevelopment(vegetationresponse)

-Treatmentsthatusepeat-mineralmixplacedaboveoverburdenandtailingsandsandinitiallyfertilizedwithP,KandelementssuchasMngeneratedecotypesmoresimilartothenaturalones

Turcotteetal.(2009)

Soilorganicmatterquality

-LowerAURresidue,alkyl/O-alkyratioandorganicmatterintheorganicmatterheavysandfractionwerefoundinoldreclaimedsites-Carbonconcentrationinthelow-densityfractioncanbeusedasindicatorofSOMqualityinreclaimedsites

Hemsley(2012)

Nitrogenavailabilityandecologicalresponses

-Higheratmosphericnitrogendeposition(mainlyasNH4+)inreclaimedsites-AmountofwetNdepositionnegativelyrelatetocanopycover-PinestandsshowedmorecloseNcycle,highertotalinorganicNandhighersensitivitytoNdeposition

MacKenzieand

Quideau(2012)

Nitrogenmineralization

-Nitrogenmineralizationrateinpeatmineralsoilfromlaboratoryincubationwasmuchhigherthannaturalforestsoils-TherateinforestfloormineralsoilwasatasimilarlevelasinnaturalLFHlayers-Theratesobtainedlaboratorywasmuchhigherthanfieldmeasurementandmodeleddecompositionrates

Microbialcommunitystructure

-Highmetabolicquotient(basalrespiration/totalmicrobialbiomass)butfeweramountsoffungiandfungi/bacteriainpeatmineralsoil-Forestfloormineralmixshowedmoresimilarmicrobialcommunitystructureasinnaturalsoils-TheeffectofNPKfertilizationonmicrobial

23

structurewasnotprominentwithoutvegetationpresence

Plantnutrientavailability

-Muchmorehighernitrogen(mainlyinnitrateform)contentwasfoundinpeatmineralandmixsoilsthaninforestfloormineralsoils-Astrongassociationbetweenrespirationandnutrientavailability

Quideauetal.(2013)

NutrientAvailability

-HigherNandSconcentrationsinreclaimedsitesbutstillsomesimilaritieswithnaturalsites

Organicmattercomposition

-Higheramountoforganicmatterinreclaimedsoils.-Verydifferentorganicmatterchemicalcompositionbetweennaturalandreclaimedsites

Microbialcommunities(biologicalproperty)

-Someuniquemicrobesfoundinreclaimedsitescomparetonaturalsitesbutalsowithsomeoverlapswithnaturalsites

Rowland (2008) – Recreating a functioning forest soil in reclaimed oil sands innorthernAlberta: InRowland’sstudy,arangeofvariablesweremeasuredwithintheWoodBuffalo

region of northern Alberta in order to determine whether reclaimed and natural

systemsdifferinsoilpropertiesandhowthereclaimedsystemschangeovertime.A

totalof47naturalandreclaimedsoilplotswereestablished.Variablesthatcollected

includemoisturecontent,pH,C:Nratio,littermasslossrate,litterinputandorganic

layer development status, in situ bio-available nutrients, nitrate and ammonium

productionandplantcommunitydevelopment.Rowlandstudiednotonlychemical

butalsomanyphysicalandbiologicalproperties.

The results of moisture showed that the presence of tailing sands at depth

generallyreducemoisturecontent,however,apeat-mineralmixcapusuallyhelped

storingmoistureunless tailingsands isdirectlybelow it.Thepresence/absenceof

plantrootactivitydidnotaffectmoisturecontentaccordingtotheexperiment.This

mightbeattributedtothemicrobialproliferationinsiteswithoutplantroots.ForpH

level,almostallsites,exceptforone,hadhigherpHthannaturalecotypesbecauseof

the clay-rich, calcium-absorbing mineral soil in the peat-mineral mix and the

windblowndepositsfromnearbyexposedtailings.

24

Intermsofnutrientstatus,abundantNO3—Nwerefoundinallsitesdespiteages

andfertilizerapplication.MicronutrientNawaslowonallreclaimedsitesbecauseof

dispersalofNafromclaysbytheadditionofgypsumandleaching.Furthermore, it

wasfoundthat litterdecompositionrateandtheFHlayerdevelopmentrateswere

sloweronreclaimedsitescomparethoseofnaturalsites.Approximatelyatleast25

yearswasrequiredtohavereclaimedplantcommunitiessimilartonaturalones.

In the end, the author concluded that the treatment types, which place

peat-mineral mix above overburden and tailing sands both generated ecotypes

similartothetargetnaturalones.Butthesesiteswithapeat-mineralmixcapneed

to be initially fertilized with P, K and elements such as Mn for successful early

ecosystemdevelopment.RowlandchallengedtheuseofNfertilizer,cleanpeatand

glacial tills as reclamation materials since abundant nitrogen was also found in

unfertilizedsoilsandthepeatandtillresourcesarenon-renewable.Healsoargued

large-scalereclamationshouldfocusmoreonecologicallandscaperestorationthan

achievingexactoriginalstate. Turcotte et al. (2009) – Organic matter quality in reclaimed boreal forest soilsfollowingoilsandsmining: Turcotteetal.assessedthereclaimedsoilqualitythrougharangeofsoilorganic

matter(SOM)parametersandcomparedtheseparameterswithnaturalsoilsinthe

FortMcMurrayoilsandsregion.TheytriedtoanswerwhethertheSOMparameters

evolvedwithtimetowardsthoseofnaturalsoilsandwhichreclamationprescription

performedthebest.Atotalof45studysites(18naturalsitesand27reclaimedsites)

were selected within an 86 km radius from the town of Fort McMurray, Alberta.

Surfacesoils(0to10cm),excludingtherawlitterlayer,werecollectedineachsite.

ThesampleswerefurtherdividedintoclayandsiltOM,lowdensityOMandheavy

sandOMfractions.Inlaboratory,theacid-unhydrolyzableresidue(AUR)(proximate

analysis),totalC(drycombustion),valueofalkylC,O-alkylC,aromaticC,phenolicC

andcarbonylC(spectrometer)andcarbonisotopiccomposition(δ13C)(isotoperatio

massspectrometer)weredetermined.

Theresultsdemonstratedthatthereclaimedsoilsandthenaturalsoilshadboth

25

similarities anddifferences in SOMparameters.The amountof total carbon in the

low-density fraction was similar in disturbed and natural sites. However,

significantly higher O-alky, lower alkyl C and lower carbon concentrations in the

low-density organicmatter fractionswere found in reclaimed soils. Turcotteet al.

explainedthesebytheusageofpeatamendmentsduringreclamation.Fortheheavy

sand and finer mineral particle (SiC) pools, it was not surprising to find the

reclaimedsiteshadsignificantlylessamountofhumifiedorganicmatter.Lastly,the

carbonconcentrationsintheAURwerealsohigherinreclaimedsoilsthaninnatural

soils, which suggested that the organicmater in the reclaimed soils has not been

stronglyaffectedbymicrobialdegradation.

In terms of the SOM parameters between young and old reconstructed soils,

Turcotteetal. foundthattheAURresidue,alkyl/O-alkyratioandorganicmatterin

theorganicmatterheavysand fractiondecreasedwith timesincereclamationand

couldbeusedasindicatorofSOMformationprocessesforreclaimedsoils.Another

goodindicatorforgeneralSOMqualitythattheyfoundwasthecarbonconcentration

inthelow-densityfractionsinceitcorrelatedwithmanySOMparameters. Hemsley (2012) – Ecological response of atmospheric nitrogen deposition onreconstructedsoilsintheAthabascaoilsandsregion: InHemsley’sstudy,heaimedto firstlydeterminetheseasonalamountsofwet

nitrogen(N)deposition,soilnitrogenavailabilityandtheirpotentialrelationshipsin

reconstructed soils and then assess the ecological responses and potential

implications of atmosphericN depositions. A total of 27 siteswith three different

tree canopy coverage (0-30%, 31-65% and 66-100%) and two species types

(trembling aspen and Jack pine) were selected 40 km north of Fort McMuaary,

Alberta. At each site, the author measured and collected atmospheric wet N

deposition (atmospheric deposition collectors), soil N availability (plant root

simulatorprobes),soils,foliageandrootsamples.

The atmospheric N deposition appeared to be <1 kg N ha-1yr-1 greater than

naturalsitesandmainlyweredepositedasNH4+.Canopycoverhadaclearnegative

relationship with the amount of wet N deposition received by reclaimed soils.

26

Although NH4+ precipitated more, it was found that NO3- was the dominant

N-availableforminreconstructedsoilsinthisstudy.Apositiverelationshipbetween

NdepositionandNavailabilitywasalsofound.

Whencomparingaspenandpineecosystems,agreateramountoftotalinorganic

Nwasfoundinpinesitesacrossallthreecanopycoverage.Thiswasexplainedbythe

physiological differences between aspen and jack pine, such as different N

requirement and uptake rates. Further experiments showed that the pine

ecosystemswerealsomoresensitivetotheadditionalNdeposition.AmoreopenN

cyclewasidentifiedinthepinestandsthanintheaspenstandsduetotheexcessive

soilNinputs.Intheend,HemsleyconcludedthatNisnota limitingnutrientinhis

reclaimed sites and more N demanding species should be planted to avoid N

leaching. Mackenzie and Quideau (2012) – Laboratory-based nitrogen mineralization andbiogeochemistryoftwosoilsusedinoilsandsreclamation: The objectives of this study include 1) determination and comparison of

nitrogenmineralizationrateconstantsbetweenpeatmineralmixedsoilandnatural

forest floor mineral mixed soil, which are two types of oil sands reclamation

materials,aswellas2)determinationoftheeffectofNPKfertilizationonmicrobial

communitystructureandnutrientprofiles.Peatandforestfloorsamplesweretaken

from a sphagnum (Sphagnum angustifolium) dominated peatland and an aspen

(Populusttremuloides)standintheAthabascaoilsandregiontocreatepeatmineral

soiland forest floormineral soil, respectively.Theauthorsmixed the two typesof

mixedsoils tocreateanothersample typeandaddedNPK fertilizer insomeof the

threesoiltypes.Nitrogenmineralizationratewasestimatedthroughmeasuringsoil

ammonium and nitrate nitrogen concentration (nitroprusside/salicylate and

cadmium reductionmethods). Phospholipid fatty acid analysis, ion exchange resin

analysis and MicroResp system were used to evaluate microbial community

structure,soilnutrientprofileandmicrobialrespirationrate,respectively.

Thenitrogenmineralizationrateinpeatmineralsoilfromlaboratoryincubation

was much higher than that in natural forest soils, while the rate in forest floor

27

mineralsoilwasatasimilarlevelasinnaturalLFHlayers.Themineralizationrates

ofallthreetypesofmixedsoilsinthisstudywereapproximatelyastwiceasfaster

than model estimated fast decomposition rate (84 mg N kg-1 yr-1). The

mineralizationratesofpeatmineralmixedsoilfromlaboratorytestwerewayfaster

thanthereportedfieldnitrogenmineralizationrates.

After four week of incubation in aerobic conditions, peat mineral soil

demonstrated the highest metabolic quotient (basal respiration/total microbial

biomass)but feweramountsof fungi inmicrobial compositioncompare tonatural

soils.Forestfloormineralmixshowedmoresimilarmicrobialcommunitystructure

as in natural soils. The effect of NPK fertilization on microbial structure was not

prominentwithoutvegetationpresencebutmightbearesultoftheshortincubation

time.

Basedontheresultsofionicexchangeresinanalysis,threetimeshighernitrogen

(mainly in nitrate form) content was found in peat mineral and peat forest floor

mixed soils than in forest floormineral soils. This large amount of nitrate in peat

mineralandmixedsoilsservesasanindicatorofhighernitrifieractivity,asreflected

bymoregram-negativebacteriafoundinthesesoils,butalsoimplieshighNleaching

potential. In contrast, additional N was retained as less leachable ammonium in

forestfloormineralsoil.Furthermore,astrongassociationbetweenrespirationand

nutrient availability was also found. In conclusion, Mackenzie and Quideau

recommendtheuseofbothpeatmineralandforestsoilandlayeringtheminsteadof

mixinginfutureoilsandsreclamationprocess,especiallyinN-deficientareas. Quideauetal.(2013)–Comparingsoilbiogeochemicalprocessesinnovelandnaturalborealforestecosystems: Quideau et al. studied a range of key soil biogeochemical attributes, such as

nutrient availability, organic matter composition and microbial communities in

reclaimed oil sand soils. A total of 41 sites (15 natural and 26 reclaimed) were

sampled for topsoils (top 0-10cm). In laboratory, nutrient bioavailability, soil

microbial communities andorganicmatter characterization in these topsoilswere

measuredbyusing incubatingplant root simulatorprobes,phospholipid fattyacid

28

analysisandNMRspectroscopy,respectively.

Inthisstudy,vegetationcoverwasthemostimportantfactorthatinfluencedthe

keybiogeochemical processes such asnutrient availability,microbial communities

andorganicmatter characteristics innatural sites, especially in coniferous stands.

After comparing the natural and reconstructed sites, Quideau et al. found much

greater amount of soil organic matter and dramatically different organic matter

chemicalcompositionsinreclaimedsitescomparetonaturalsites.Somedifferences

inthemicrobialcommunities(twouniqueunsaturatedPLFAs)andsomedifferences

in nutrient availability such as higher N and S concentrationswere also found in

reclaimed soils. The authors explained these differences mainly by the

characteristicsofmaterialsusedduring reclamationandabovegroundvegetation.

Inaddition,thecontentofbasecations(Ca,Mg,K)werefoundtobegoodindicators

of some specific ecosite groupings. In the end, since the responses of soil

biogeochemical attributes are very variable, Quideau et al. emphasized the

importance of considering the range of natural landscape variability and testing

more than a few soil biogeochemical attributes for effective reclaimed soils

assessment.

2.3SoilBiologicalProperties

Table3.BiologicalpropertiesanddescriptionsofreclaimedoilsandssoilsinAlberta,Canada.

Studies(Year)

Properties Findings

McMillanetal.(2007)

Microbialactivity

-LowerMBCandMBNwerefoundinreclaimedsoils-PositiverelationshipbetweendissolvedorganicN(DON)concentrationandinsituMBCandMBN-LowerDON,totalN,MBNfoundinreclaimedsites-Forestfloormixinreclamationmaterialhelpincreasingmicrobialactivity

Nitrogenmineralization(chemicalproperty)

-Similarlevelofgrossammonificationratesinreclaimedandnaturalsites-Lowernetammonificationratesinreclaimedsites

29

SoilpHlevel(chemicalproperty)

-Acidicinbothreclaimedandnaturalsoils,rangefrom5.38to5.95

Bulkdensity(physicalproperty)

-Highbulkdensityinreclaimedtopsoil

Soilmoistureand

temperature(physicalproperties)

-Lowersoilmoistureandhighertemperatureinreclaimedtopsoil

MacKenzieandQuideau(2009)

Microbialcommunitystructure

-Seasonandsiteconditionsappearedtobethemostandsecondmostinfluentialfactorofmicrobialcommunitystructure-Slopedidnotshowasignificanteffect-Totalsoilmicrobialbiomass(TMB)andsoilfungaltobacterialratio(FBR)weresignificantlyaffectedbytheinteractionoftimeandsitebutwithoutcleartrend

Nutrientavailability

-Siteconditionsandseasonwerefoundtobethemostandthesecondmostinfluentialfactorbyordinationanalysis-Slopedidnotshowsignificanteffectsonnutrientavailability -Ammoniumandnitrateconcentrationsweresignificantlyaffectedbytime,siteandtheirinteraction -Boronasanimportantmicronutrientincreasedlaterinthegrowingseason

Dimitriuetal.(2010a)

Microbialcommunitycompositionandfunctionin

peat

-Negativerelationshipbetweenrespirationratesandmicrobialabundance(dilutionlevel)-Positiverelationshipbetweenenzymeactivityandmicrobialabundance -Norelationshipbetweenmicrobialrichnessandmicrobialabundance-Highdegreeofmicrobefunctionalredundancy-Bothtaxonomicdiversityandtheinteractionsbetweenmicroorganismsintheinoculumsourcesandpeattypewouldaffecttherelationshipbetweenmicrobialcommunitycompositionandfunction

Dimitriuetal.(2010b)

Enzymeactivities

-Soilreconstructionmaterialinsteadoftime-since-reclamationaffectedenzymeactivitiesthemost

30

-Overburdenandtailingsandscausedsignificantdecreaseinphenoloxidaseactivity

Microbialcommunitycomposition

-Theuseofoverburdenandtailingsandsincreasedthedissimilaritiesofmicrobialcommunitywithnaturalsites-Fungal-to-bacterial-biomassratio,pHandwoodydebrisallsignificantlyinfluencemicroorganismsdistributioninreclaimedsites-Reclaimedsitesweregram-negativebacterialdominatedwhilenaturalssiteswereectomycorrhizaefungidominated-Successfuldevelopmentofmicrobialcommunityonreclaimedsoilsdependedindirectlyonvegetationregrowthconditionanddirectlyonsoilabioticproperties,suchaspHandreclamationmaterial

DimitriuandGrayston(2010)

Soilbacterialdiversity

-Similarbacterialcommunitycompositiondespitedifferentabovegroundvegetationcover-α-Proteobacteria,acidobacterialandbetaproteobacterialsequenceswerethetopthreedominatingbacterialsequences-SoilpHandsoilmoisturewerethemostregulatingfactorandindicatorofsoilbacterialcommunitycompositioninreclaimedandnaturalsoils,respectively-Reductioninthediversityofactivebacterialcommunitiescouldfurthercausedeclinesinbothrichnessandevennessofdominanttaxa.

Sorensonetal.(2011)

Soilorganicmatter

composition

-Carbonaccumulationoccurredsignificantlyonlyinreclaimedaspenstandsbutnotinpineandsprucestands

Microbialcommunities

-Verylowpresenceofvisiblefungalmyceliaandfinerootsoccurredinmostreclaimedsites,indicatinglowmicrobialactivities-Whencanopycoverwasbelow30%,soilmicrobialcommunitycompositionchangedaccordingtousedreclamationsubsoiltexture-Above30%,theeffectsofstandtypesoncompositionbecamemoreapparent

Forestfloordevelopment

-Reclaimedaspenandsprucestandshadthinnerforestfloorwhilereclaimedjackpinestandshadreachedsimilarthicknessasinnaturalstands-VerythinHlayerinallreclaimedstands-Canopycover(includeshrubcover)played

31

importantroleininfluencingforestfloorthicknessandsoilcarbonconcentration-StandAgewasalsobutonlyimportantinaspenstands

Onwuchekwa(2012)

Mycorrhizalcomposition

-Peat-mineralmixhadthehighestamountofEctomycorrhizal(ECM)colonizationbutquitelowArbuscularmycorrhizal(AM)colonization-TailingsandhadlowpotentialtosupportbothAMandECMmycorrhizalfungigrowth-Naturalforestsoilshadintermediateamountsofbothfungaltypes-OverburdenhadrelativelyhighamountofECMcolonizationbutlowAMcolonization-Pleosporalessp.,HelotialestypeandaspeciesthatcorrespondstothePyronemataceaewerethemostfrequentlyrecordedfungitaxa-ArtificialECMinoculationexperimentshowedincreasedstemvolumeforpineandspruce,increasedheightgrowthofpinebutnosuchheightresponseinspruceandincreasedsurvivalrateofsprucewhilenosuchresponseinpine.

McMillan et al. (2007) –Nitrogenmineralization andmicrobial activity in oil sandsreclaimedborealforestsoils: Theobjectiveof thisstudywas tocompare themicrobialactivityandnitrogen

mineralization among soils reclaimed with forest floor-mineral mix (LM),

peat-mineral mix (PM), a combination of the two (L/PM) and natural soils from

northernAlberta.Soilcoresweretakeninsiteswiththreedifferenttreatmentsand

natural sites. Net nitrification, ammonification, and N mineralization rates were

sampledfromfieldincubationsusingburiedbagsandestimatedby15Nisotopepool

dilutiontechnique.Inlaboratory,soilmicrobialbiomassC(MBC)andN(MBN)were

measuredbythechloroformfumigation-extractionmethod. Inaddition,amoisture

manipulationexperimentwasalsoconductedtofurtherinvestigatetherelationships

between soil moisture and respiration rates, MBC and MBN. Other basic soil

chemicalandphysicalproperties, suchasbulkdensity,moisture, temperatureand

pHlevelwerealsorecordedinthefield.

For basic soil properties, it was found that soil bulk density was higher in

32

reclaimed topsoil and explained by the compaction during reclamation process.

Lowertopsoilmoisturecontentandhighersoiltemperaturewasfoundinreclaimed

sites,whichmightbe causedby the lackof forest canopycover.All reclaimedand

naturalsiteshadacidicpHconditions(rangefrom5.38to5.95).

In terms ofmicrobial dynamics in reclaimed sites, lowerMBC andMBNwere

foundinreclaimedsoilscomparedtothenaturalsoils.Thismaybeattributedtothe

lower moisture content in reclaimed soils and/or differences in organic matter

compositions. A positive relationship between dissolved organic N (DON)

concentration and in situMBC andMBNwas also observed. However, despite the

higher DON, total N, MBN found in natural sites, gross ammonification rates in

reclaimed sites did not appear to be affected by reclamation disturbance. On the

otherhand,netammonificationdecreasedinreclaimedsites,whichindicatedeither

astrongerimmobilizingenvironmentorfasternitrificationrateatreclaimedsites.

The results ofmoisturemanipulation experiment confirmed that natural sites

hadmore activemicrobial activates than reclaimed sites did based on the higher

MBC and respiration rates (but similar MBN value as in the LM treatment). The

forest floor-mineralmix treatment generated the secondhighest respiration rates,

MBC and MBN, which made the author concluded that forest floor was a good

stimulatorofmicrobialactivitytohaveforoilssandsreclamation.MacKenzie and Quideau (2009) – Microbial community structure and nutrientavailabilityinoilsandsborealsoils: In this study, MacKenzie and Quideau tried to 1) determine the relationship

between microbial community structure changes and vegetation, seasonal and

annualvariability;2)understandtheeffectsoftopographyonmicrobialcommunity

structureandnutrientprofilesinreclaimedoilsandssoils.Threereclaimedsiteson

threedifferent slopes (upper,mid and lower)were selected for sampling in three

different years in approximately 60km north of Fort McMurray, northeastern

Alberta. Basic chemical and physical properties, microbial community structure

(PLFA analysis) andnutrient availability (PRSprobes)weremeasured for the soil

samplesfromeachsite.

33

Other thansiteorslopepositions, seasonsappeared tobe themost influential

factorofmicrobial communitystructuremost likelybecauseof thechanges in soil

moisture levels. For samples that were taken in the same season, site condition

became the second most important factor that influences microbial community

structurebecauseoftheeffectsofdifferentamountofvegetationcoveronsites. In

addition,both total soilmicrobialbiomass (TMB)and soil fungal tobacterial ratio

(FBR) were significantly affected by the interaction of sampling time and site

conditions but without clear trend. The effects of site and time interaction were

mainly explained by substrate differences, time since peat-mineralmix placement

and re-vegetation status. Surprisingly, slope did not have consistent effects on

reclaimedmicrobial community structure in this study,whichmight be causedby

undevelopedsoilstructure.

Intermsofnutrientavailability,sitesandseasonswerefoundtobethemostand

thesecondmostinfluentialfactorbyordinationanalysis.Again,slopehadnoeffects

on nutrient availability. Thesewere also explained by time since reclamation and

re-vegetation status. Ammonium and nitrate concentrations were significantly

affected by time, sites and their interaction because of the associated effects of

different vegetation cover on soil microbial communities. Boron, which is an

important micronutrient increased later in the growing season as a result of

continuingmicrobialactivities. Dimitriu et al. (2010a) – An evaluation of the functional significance of peatmicroorganismsusingareciprocaltransplantapproach:

Inordertoexaminetherelationshipbetweenmicrobialcommunitycomposition

andfunctionsuchasrespiration,nutrientacquiringandlignin-degradationinpeat,

Dimitriuetal. conducteda reciprocal transplantexperiment.Twodistinct typesof

sterile peat samples, humified (sedge) and coarse plant material (fibric) were

inoculatedwithserially-dilutedsuspensions(10-1,10-3,10-5and10-8)fromthesame

or reciprocal peats. After fivemonths of incubation, all active bacterial taxawere

labeled (nucleotide-analog technique), the peat’s functional potential and the

structures of active and total bacterial communities (PCR-DGGE) were also

34

measured.

In general, the findings showed a negative relationship between respiration

ratesanddilution levelsbutapositiveonebetweenenzymeactivitiesanddilution

levels. Bacterial richness was insensitive to dilution levels since most

microorganismscanregroweasilywhentheconditionisright.Furthermore,itwas

found that not only the inoculum source but also the peat type significantly

influenced the bacterial community structure and richness. Nevertheless, the

inoculum source and peat type did not influence active bacterial populations and

respiration rates, which implied a high degree of functional redundancy.

Furthermore, the authors also found that nutrient acquisition enzyme and

lignin-degrading activities were mainly affected by soil types and microorganism

community composition, respectively. It was concluded that both taxonomic

diversityandtheinteractionsbetweenmicroorganismsintheinoculumsourcesand

peattypeswouldaffecttherelationshipbetweenmicrobialcommunitycomposition

andfunction. Dimitriuetal.(2010b)–Impactofreclamationofsurface-minedborealforestsoilsonmicrobialcommunitycompositionandfunction: This study researched the impacts of soil reclamation and

time-since-reclamationonenzymeactivitiesandmicrobialcommunitycomposition

intheAthabascaoilsandsregion.Bulksoilinbothnaturalandreclaimedsitesthat

ranged from5 to 30 years old andused sevendifferent reclamationprescriptions

were sampled for extracellular enzyme activities (microplate assays) and

communitystructureanalysis(PLFAandDGGEanalysis).Inthefield,measurements

suchascarbon,nitrogen,pHandmoisturewere takenusingstandardmethods. In

addition,nutrientavailability(plantrootsimulatorprobes)andvegetationstructure

werealsorecorded.

The results from reclaimed sites with different ages suggested that soil

reconstructionmaterialinsteadoftime-since-reclamationaffectedenzymeactivities

themost.Theuseofoverburdenandtailingsands,whichhavelowcarboncontent,

caused significant decrease in phenoloxidase activities and increased the

35

dissimilarities of microbial community with natural sites (based only on PLFA

results)andconsequentlywerenotrecommendedforreclamationuse.Furthermore,

itwas foundthatdifferent factorscontrolledthedistributionofmicroorganismsin

reclaimedsitesandnaturalsites,whichwerefungal-to-bacterial-biomassratioand

soilnitrogen,respectively.However,ifallsiteswereanalyzedtogether,soilpHand

woody debris accumulation also played significant roles of shaping microbial

distribution in general, which implied vegetation development could influence

microbial community growth indirectly. Another difference between

microorganisms in reclaimed and natural soils was that reclaimed sites were

gram-negative bacterial dominatedwhile natural siteswere ectomycorrhizal fungi

dominated. Finally, the authors concluded that the successful development of

microbial community on reclaimed soils depended indirectly on vegetation

regrowth condition and directly on soil abiotic properties, such as pH and

reclamationmaterial. DimitriuandGrayston(2010)–Relationshipbetweensoilpropertiesandpatternsofbacterialβ-diversityacrossreclaimedandnaturalborealforestsoils: Dimitriu and Grayston tried to quantify the phylogenetic and compositional

diversity patterns of soil bacteria in reclaimed and natural siteswith two distinct

edaphiccharacteristics(xeric-poorandmesic-rich)intheAthabascaoilsandsregion.

Six sites (two xeric-poor, two mesic-rich and two reclaimed sites one with

vegetationandonewithout)werechosenforbulksoilsampling.Bacterialdiversity

under phylogenetic and species-based frameworks (16S rRNA-sequence-based

approach)andthecompositionofactivetaxa(nucleotideanalog)inreclaimedsites

weredetermined.

The two types of natural sites had more similar phylogenetic and taxonomic

diversities among bacterial communities compare to the reclaimed sites. The

composition of the bacterial communities in two reclaimed sites was also similar

despite contrasting vegetation covers. The α-Proteobacteria, acidobacterial and

betaproteobacterial sequenceswere the top three dominating bacterial sequences

foundinmostsites.Innaturalsites,soilmoisturewasthemostregulatingfactorthat

36

of soil bacterial community composition and explained 32% of the variance in

phylogenetic structure. However, in disturbed sites, soil pH, instead of vegetation

cover,wasfoundtobethemostinfluentialfactorofbacterialcommunitystructure,

which explained16 to34%of thevariability. In addition, soil pHwas also a good

indicator of soil bacterial richness (Chao1) and diversity (Shannon). In the end, it

was concluded that a reduction in the diversity of active bacterial communities,

whichwascloselylinkedto“master”variables(e.g.pH,moisture)inthisstudy,could

furthercausedeclinesinbothrichnessandevennessofdominanttaxa.

Sorenson et al. (2011) – Forest floor development and biochemical properties inreconstructedborealforestsoils:

Inthisstudy,Sorensonetal.evaluatedtheinfluencesofdifferentcanopycover

and three reclaimed stand types on novel soil organic matter composition, soil

microbial communities and forest floor development. The three stand typeswere

tremblingaspen(Populustremuloides),jackpine(Pinusbanksiana)andwhitespruce

(Piceaglauca)locatedinnorthofFortMcMurray,Albertaandallrangedbetween16

to 33 years old. A total of 32 sites (11 aspen, 11 spruce and 10 pine sites) were

established and surveyed for vegetation composition and forest floor parameters

suchas thicknessandmorphology.Soil sampleswerealsocollected for laboratory

analysisofcarbonandnitrogencontentsinmineralsoilsandforestfloor.Microbial

community composition was also estimated by various methods such as

phospholipid fatty acid (PLFA), ramped-cross-polarization (RAMP-CP) and 13C

nuclearmagneticresonance(NMR)analysis.

In contrast to aspen and spruce stands, which had thinner forest floor

development than reference natural stands, pine stands had already reached the

thickness similar to nearby natural pine stands at the time of study but mainly

becausetheaverageforest floorthickness innaturalpinestands is thinnerthan in

natural aspen and spruce stands. Morphologically, very low presence of visible

fungalmyceliaandfinerootsoccurredinmostsites,whichledtoabsentorverythin

H layers.Thesevery thinH layers indicated lowmicrobial activities. In aspenand

37

spruce stands, canopy cover played an important role in influencing forest floor

thicknessand soil carbonconcentration. Standagewasalsobutonly important in

theaspenstands,whichmaybearesultofthefasterestablishmentofcanopycover

in time. In addition to tree canopy, shrub canopy also had a positive relationship

withforestfloordevelopmentinconiferousstands.

Although carbon and nitrogen concentration increased in the aspen and pine

stands,thesignofnaturalcarbonaccumulation(changeinthelightfractioncarbon

composition) from regrown canopy was only clear in the aspen stands. Another

discoveryofthisstudywastherelationshipsamongreclamationprescription,stand

type,canopycoverandsoilmicrobialcommunitycomposition.Whencanopycover

was below 30%, soil microbial community composition changed according to

reclamationsubsoiltexture.However,above30%,theeffectsofstandtypesbecame

moreapparent.Therefore, theauthorssuggestedthatachieving30%canopycover

shouldbeacriticalthresholdpointduringsoilreclamationinoilsandsregions.

Onwuchekwa(2012)–EnhancedrevegetationandreclamationofoilsandsdisturbedlandusingMycorrhizae: Sincemycorrhizal fungi has the ability to increase vegetation reestablishment

success, Onwuchekwa assessed the natural mycorrhizal inoculum potential in

various oil sands reclamation materials, identified and characterized the fungal

strainsinreclamationmaterialsandconductedanotherexperimenttoevaluatethe

potential benefits of artificial ectomycorrhizal (ECM) fungi inoculation on white

spruce and jack pine seedling growth and survival. For the natural mycorrhizal

(Arbuscularmycorrhizal andectomycorrhizal) inoculumpotential assessment, five

different reclamation materials, including peat-mineral mix, overburden, tailing

sands,topsoilandintactforestsoil,werecollectedintheoilsandsminingareasnear

FortMcMurray, Alberta. Red clover (Trifoliumpretense) andwhite spruce (Picea

glauca)seedswereselectedastestingspeciesforthenaturalmycorrhizalinoculum

potential assessment. For artificial mycorrhizal inoculation (grow from Glucose

yeast) experiment, white spruce and jack pine (Pinus banksiana) were inoculated

with three different ECM species (Hebeloma crustuliniforme, Laccaria bicolor and

38

Suillus tomentosus). Seedling shoot and diameter growths and survival rateswere

collectedfromfieldobservation;biomasswasobtainedbycombustionmethod;and

mycorrhizal type was determined by DNA extraction and PCR amplification

methods.

The results of natural mycorrhizal inoculum potential reported very low

presencesofbotharbuscularmycorrhizal(AM)andECMfungiintailingsands.The

peat-mineral mix had the highest amount of ECM colonization but quite low AM

colonization probably because ECM can produce ectoenzymes to absorb excess

nitrogen in peat. Intact forest soil did not have the expected high amount of

mycorrhizal colonization but intermediate amounts of both types probably due to

the low diversity of replanted vegetation species. Overburden had relatively high

amountofECMcolonizationbut lowAMcolonization.Topsoilwas foundtobe the

most acceptable reclamation substrate since the amount of colonization of both

specieswasrelativelyhigh.

Inthisstudy,Pleosporalessp.,Helotialestypeandaspeciesthatcorrespondsto

the Pyronemataceae were the most frequently recorded fungi taxa and could be

found in topsoil, overburden, forest soil and tailing sands.These three species are

non-host specific in most cases. However, the author reminded us that the

developmentofmycorrhizalcouldbedramaticallydifferentingreenhouseandfield.

The results of artificial ECM inoculation experiment showed increased stem

volume for both species, increased height growth of jack pine but no such height

incrementinwhitespruce.Thismightbeattributedtositecharacteristicsandbetter

cooperationbetweenjackpinerootsandfungi.Inaddition,thesurvivalrateofwhite

spruceseedlingsdid improvedbymorethan10%possiblyduetohighermoisture

access. But no such increased survival rate was observed for jack pine possibly

because of non-indigenous fungi specie selection or site climatic conditions

favouring certain type of fungal species. In general, Onwuchekwa concluded that

re-introductionofmycorrhizalfungiduringreclamationprocesshasthepotentialto

becomeaneffectiveapproachtoimprovevegetationdevelopment.

39

2.4VegetationCommunities

Table 4. Some characteristics of vegetation community development on reclaimedoilsandssoilsinAlberta,Canada. Studies(Year)

Properties Findings

Cooper(2004)

Wetlandvegetation

-Planthealthandrootingdepthsinthereclaimedwetlandswereacceptable-Similarvegetationabundancebutdifferentspeciescompositionbetweenreclaimedandreferencewetlands-Salinityinsurfacewaterandsubsoils,wetlandisolationandharshclimaticconditionarethreelimitingfactorsofvegetationdevelopmentinreclaimedwetlandsandmayevenalterspeciesreplacementsequences

Lillesetal.(2009)

Aspenandwhitesprucegrowthonnatural

salinesoils

-Whitesprucegrowthwasunaffectedbythedifferentsalinitylevels -Aspengrowthwasreducedwithhighsalinity-Neitherwhitesprucenoraspenshowedevidenceofsalinity-relatedeffectsonrootdistributionandnutrientstressinfoliagedevelopment

Pinnoetal.(2012)

Aspengrowthanddevelopment

-Soiltype(mainlyorganicmattercontent)hadthelargestimpactonaspengrowthwhennofertilizerwasapplied.Buttheimpactdiminishedafterfertilization-Noimpactofsoiltypewasfoundonseedgerminationandseedlingestablishment-AspengrowthwasonlypositivelyrelatedtoincreasingKavailability-Incompletefertilizationmightgiveaspenanevenlowerbudsetthannofertilization

Kovalenkoetal.(2013)

Wetlandfoodwebstructure

-Reclaimedwetlandswerelowinmacrophytebiomass,microbialbiomass,trophicdiversityandinvertebraterichnessbuthighintheconcentrationofnaphthenicacidscomparetoreferencewetlands-Wetlandageandpeat-mineralmixdidnotsignificantlymitigatetheeffectsofoilsandswastematerialsontheaquaticbiotabutstillsomeimprovementinbiomassofmajorbioticcompartments-LowC:Nratiosinreclaimedwetlands

Copper(2004)–Vegetationcommunitydevelopmentofreclaimedoilsandswetlands: InCopper’sstudy,hetriedtoanswerwhetherchemicalandphysicalconditions

of reclaimedwetlandswould intervenewith vegetationdevelopment andwhether

natural colonization of local plant species would occur in reclaimed wetlands in

40

order to assess the effectiveness of natural recovery. He studied and compared

speciesrichness,aerialpercentcoverandsimilarityofthevegetationamonganewly

constructedconsolidated/compositetailings(CT)wetland,anaturalwetlandandan

opportunisticwetland for two years. Othermeasurements such asmetals, anions,

electricalconductivity,pHandtemperatureinwaterwerealsotaken.

The resultsofvisual assessmentsofplanthealthand rootingdepths in theCT

wetlandindicatedthatthephysicalandchemicalconditionsoftailingsdidnotlimit

plant growth and survival for most species. However, despite the similar species

abundances, the species compositions between reconstructed CT wetland and

referencewetlandswerequitedifferent.Thispartiallymightbecausedbythehigh

natural variability in water regimes in the reference wetlands. Some species

emergencewasinhibitedfromreclaimedwetlandsubsoilsduetohighsalinity.The

authorproposed that salinity in surfacewater and subsoils,wetland isolation and

harsh climatic conditions were the three most important limiting factors of

vegetation development in reclaimed wetlands and may even alter species

replacementsequences.Lilles et al. (2012) – Growth of aspen and white spruce on naturally saline sites innorthern Alberta: implications for development of boreal forest vegetation onreclaimedsalinesoils: Sincealotofreclaimedoilsandssoilshavehighsalinity,Lillesetal.investigated

theheightandbasalareagrowthsofmaturetremblingaspenandwhitespruceon

sixnaturalsitesacrossasalinegradient(high,medium,lowandcontrol)inorderto

predictfutureforestproductivityonreclaimedsalinesoilsinnorthernAlberta.Tree

growthratesofheightandbasalarea,rootdistributionsandfoliarparameterswere

collectedinthesesites.

It seemed that white spruce growth was unaffected by the different salinity

levelswhilematureaspengrowthwasreducedwithhighsalinity.Althoughmedium

andlowsalinesoilsprovidedfastaspengrowth,aspeninthehigh-salinitysiteshad

similargrowthratesinpest-andpathogen-stressedstands.Theeffectsofsalinityon

aspengrowthmight get even strongerwith time.Thedifferences inplantbiology,

41

such as shade-tolerance ability and natural growth rate variability, explained the

differencesbetweenaspenandwhitesprucegrowthsinresponsetosalinity.Neither

white spruce nor aspen showed evidences of salinity-related effects on root

distribution and nutrient stress in foliage development. In the end, the authors

concluded that aspen and white spruce could establish on saline soils with the

presence of organic matter layer and appropriate nutrient and moisture levels.

However, these stands shouldnot beused for forestryproductionpurposedue to

thelowproductivity. Pinnoetal.(2012)–Tremblingaspenseedlingestablishment,growthandresponsetofertilizationoncontrastingsoilsusedinoilsandsreclamation: This study used a greenhouse experiment to examine the complete cycle of

aspen growth and development on awide range of soil types. These soils all had

beenusedassurfacematerialsduringoilsandsreclamation.Eightdistinctsalvaged

stockpiles of soilwith a range in fertility, pH, organicmatter content and Pwere

used,whichwerepeat-mineralmix,forestfloor-mineralmix,Bhorizon-veryhighP,

Bhorizon-lowPandlowpH,Bhorizon-highPandlowpH,Bhorizon-lowPandhigh

pH, subsoils and tailing sands. Variables that were measured include seed

germinationandsurvivalratesaswellasheightgrowthbeforeandafterfertilization.

The results suggested that soil type had the largest impacts on aspen growth

whenno fertilizerwas applied. But the impacts diminished after fertilization. The

bestandworstaspengrowthwasfoundonsoilswithabundantorganicmatter,such

aspeat-mineralandforestfloor-mineralmix,andsoilswithloworganicmatter,such

assubsoilandtailingsands,respectively.Noimpactofsoiltypewasfoundonseed

germinationandseedlingestablishmentsinceconsistentwatersupplywasprovided

inthegreenhouse.

AlthoughN,PKappearedtoallbelowtheoptimal foliarconcentrations,aspen

growth was only positively related to increasing K availability. This is probably

becauseof the large imbalanceswithinthe internalN:Pratios.Surprisingly,aspen

growth did not response significantly to PK fertilization given the very low P

availability insomesoilsandthepositiverelationshipwithK.Anothernoteworthy

42

finding was that incomplete fertilizationmight give aspen an even lower bud set

thananofertilizationtreatment. Kovalenkoetal.(2013)–Foodwebstructureinoilsandsreclaimedwetlands: Kovalenko et al. aimed to firstly characterize the effects of oil sands process

materials(tailingsandwater)andpeat-mineralmixonfoodwebcompartmentsand

carbon flows in reconstructed wetlands and then evaluate the effects of

time-since-reclamation on wetland trophic structure. In order to do these, 17

naturallyformedreferencewetlandsand12oilsands-affectedwetlands,whichwere

constructedin1970to2004withtailingsandwater,wereselectedforaccessingthe

composition and biomass of aquatic plants and invertebrates (sweep nets and

floating hoop traps), microbial biomass (chlorophyll a concentrations and

combustionmethod),andfoodwebstructure(stableisotopedata).

The results indicated that reclaimed wetlands were significantly low in

macrophytebiomass,microbialbiomass,trophicdiversityandinvertebraterichness

but high in the concentration of naphthenic acids, which is a toxic constituent,

comparedwithreferencewetlands.Severalotherinorganiccompoundsinoilsands

process water, such as AL, AS, Cd, Mo and Se, also contributed to the observed

reduction in major biotic compartments but can be detoxicated with time more

easily compare to the naphthenic acids. Additionally, high salinity also interacted

with other stressors and propagated throughout the food web, causing lower

invertebrateandmacrophytebiomassesinreclaimedwetlands.

In terms of the effects of time-since reclamation and peat-mineral mix

amendment,therewasinsufficientevidencetoconcludethatwetlandageandpeat

couldmitigate theeffectsofoil sandswastematerialson theaquaticbiotadespite

peat’scomplexdirectandindirecteffectsonwaterquality.Buttheolderreclaimed

wetlandstendedtohaveslightlyhigherbiomassofmajorbioticcompartments,such

as benthic and planktonic invertebrates, and emergent macrophytes than the

youngerones.Lastly,theauthoralsopointedoutthatthelowerC:Nratiosfoundin

reclaimedwetlandscouldbeasignofnitrogenlimitation.

43

3.Discussion

3.1ReclamationTreatmentsEffects

Ingeneral,thereclaimedoilsandssoilsarequitedifferentfromnaturalsoilsin

many soil physical, chemical and biological properties. For starters, compare to

naturalborealforestsoils,highersoiltemperatureandlowermoisturecontentcould

be found in recently reclaimedsitesdue to lackof layer (McMillanetal. 2007). In

addition,organicmattercontentandorganicmatteraccumulationratewerefound

significantly different between reclaimed and natural forest sites in several

examinedstudiessuchasTritesandBayley2009,Quideauetal.2013andAnderson

2014. They all found much higher organic matter content and lower organic

accumulation rates in reclaimed soils compare to natural soils. These findings are

not surprising since large amount of peat was commonly used during the

reclamation process and many reclamation materials such as tailing sands and

overburdenpossessedadversechemicalproperties.However,inreclaimedwetlands,

Trites and Bayley (2009) found that input litter type instead of reclamation

materialswasthestrongerinfluencingfactorofdecompositionrate.Thecausesfor

thisdifferentresponsebetweenwetlandsandforestsrequirefurther investigation.

Possible candidates of the causes might be different microbial communities

compositionand/ordifferentmicrobialactivitieslevels.

Bulkdensitywas also found to be higher in reclaimed soils due to equipment

compactionduringreclamationbyMcMillanetal.2007.Surprisingly,Yarmuch2003

found a contrasting result of lower bulk density in reclaimed topsoil compare to

natural Ae horizon. This could be attributed to some low-impact reclaimed

techniques that the oil sands companies adopted, such as lightweight equipment,

wheeled and tracked equipment and letting the reclaimed materials be frozen

beforehand.Thesecontrastingresultsofbulkdensitydemonstratedthepotentialof

preventingsoilcompactionwithcareful low-impactmanagementandthenecessity

ofpromotingthesetechniques.

Forchemicalproperties,thehighernitrogen(N)contentinreclaimedsoilisthe

44

mostprominentdifferencecomparetonaturalsoilsassupportedbyRowland2008,

Hemsley2012,MacKenzieandQuideau2012andKovalenkoetal.2013.Thismight

be attributed to the higher atmospheric nitrogen deposition in reclaimed soils,

whichiscausedbythelowercanopycovers(Hemsley2012;MacKenzieandQuideau

2012). Nevertheless, in contrast to those studies, McMillan et al. (2007) found a

lower totalN and lowernetnitrogenmineralization rate in reclaimed forest soils.

The reason might be that MacKenzie and Quideau (2012) obtained the N

mineralizationratesresultsonly forpeat-mineralmixandforest-floormineralmix

soils. And these results were from laboratory inoculation instead of filed

measurements. The real field Nmineralization rate can be suppressed due to the

adverse chemical conditions created by other reclamation materials such as

overburdenandtailings.

Intermsofmicrobialcommunities,morebacterialandlessfungiwerefoundin

reclaimedsoilscomparetonaturalsoils(Dimitriuetal.2010b;Sorensonetal.2011).

McMillanetal.(2007)foundlowermicrobialbiomassCandmicrobialbiomassNin

reclaimedsoils,which implied lowermicrobialactivity.Thismightbe theresultof

theslightlyhigherpHlevelinreclaimedsoils(Rowland2008)sincemultiplestudies

showedthatsoilmoistureandpHarethetwomostimportantfactorsthatshapesoil

microbial community structure in reclaimed soils (Mackenzie and Quideau 2009;

Dimitriuetal.2010b;DimitriuandGrayston2010).Amoreconcerning fact is that

the negative effects of reclamation materials on microbial enzyme activities can

persistevenafterthesitesbecameold(Dimitriuetal.2010b).

The vegetation communities of reclaimed forest andwetlands appeared to be

growingbutnotas goodas innatural sites. Inwetlands,different compositionsof

species were found between natural wetlands and reclaimed wetlands (Cooper

2004). Kovalenko et al. (2013) also found low macrophyte biomass, microbial

biomass, trophic diversity and invertebrate richness due to the relatively high

chemicalpollutantlevelsinreclaimedwetlands.

Lastly, somemitigatingeffectsof timewereobserved in a fewstudies suchas

Rowland2008,Sorensonetal.2011andKovalenkoetal.2013.Althoughvegetation

45

communitiesand forest floor inaspenappear tobeable toachievesimilarnatural

stages approximately 25 years after reclamation, some more resistant soil

propertiesliketextureandtheforestfloorinconiferforests,whichhavelessorganic

matterinputs,willnotbeabletorecovertothepre-disturbancestateevenafter20

years.

3.2ReclamationandManagementImplications

Otherthantheaforementionedlow-impactreclamationtechniques,manyother

reclamationandmanagementlessonscanbelearnedbasedontheresearchresults,

namely:

1. Topsoil was found to be themost acceptable reclamation substrate in

terms of mycorrhizal fungi growth supporting ability. The use of

overburden and tailing sands should be minimized and/or carefully

planneddue to their lowability to supportenzymeactivitiesand fungi

growthaswellastheirpotentialtoincreasedissimilaritiesofmicrobial

communitycompositionsbetweennaturalandreclaimedsoils(Dimitriu

etal.2010b;Onwuchekwa2012)

2. Theuseofforestfloorduringreclamationasanorganicamendmentcan

improve soil nitrogen mineralization rate (McMillan et al. 2007;

MacKenzieandQuideau2009).Layeringthepeat-mineralmixandforest

floor mineral mix soil instead of mixing them is also recommended

(MacKenzieandQuideau2009).

3. Complete fertilization is necessary for aspen stands growth since

incomplete fertilizationmight give reclaimed aspen stands even lower

budsetthananofertilizationtreatment(Pinnoetal.2012).Goodaspen

growthrequiresbothorganicmatterandKfertilization.

4. Aspenandwhitesprucecouldestablishonsalinesoilswiththepresence

of organic matter layer and appropriate nutrient and moisture levels.

However, these stands will not be suitable for commercial forestry

productionpurposebecauseofthelowproductivity(Lillesetal.2009).

46

5. For faster organic quality improvement, aspen can be planted in

reclaimed sites since reclaimedaspen standshad fasterdecomposition

ratesandbettercarbonaccumulationthanreclaimedjackpineandwhite

sprucestands (Sorensonetal.2011).However, forareasneeds thicker

forestfloor,jackpineispreferredthanaspenandwhitespruceduetoits

lowdecompositionrate(Sorensonetal.2011).

6. Sincenitrogenisexcessive inmanyreclaimedsites,moreNdemanding

speciescanbeplantedtoavoidNleaching(Hemsley2012),

7. The results of artificial ecotomycorrhizal fungi inoculation experiment

showed increased stem volumes for pine and spruce, increased height

growth for pine and increased survival rate of spruce (Onwuchekwa

2012).Therefore,assistingthereintroductionofecotomycorrhizalfungi

inreclaimedsitesshouldbeencouragedifcommerciallyavailable.

8. Bettersalinitycontrolmightbeneededinwetlandreclamationbecause

salinityisstillanimportantlimitingfactorofvegetationdevelopmentin

reclaimedwetlandsandmayevenalter species replacementsequences

(Cooper2004).

9. Reclamationmonitoring programmayuse carbon concentration in the

low-density fraction as indicator of SOM quality in reclaimed sites

because of it relates to many other organic attributes (Turcotte et al.

2009).

3.3LimitationsandFutureResearches

Althoughmostofthestudies(15outof20)inthisreportwasconductedby(or

involvedwith)UniversityofAlberta,universities inneighboringprovinces suchas

University of British Columbia (UBC) and University of Saskatchewan are also

conducting or conducted many researches about the soil properties in Albert’s

reclaimed oil sands regions. Therefore,manymore studies are being finished and

publishedeveryyear.Forinstance,onemasterthesisthatstudiestherelationships

betweenvegetation types and soil carbon is just about to finish inUBC.Given the

47

large amount of researches, this paper definitely will not be able to cover all

publishedstudiesandfuturepublicationsonthepropertiesofreclaimedsoils.

Another major limitation of this study is the absence of statistical analysis.

Researchesofreclaimedsoilspropertiesvaryinmethodsandresults.Thecausesof

thesevariancesandsomeevencontradictingresultscanonlybespeculatedwithout

properstatisticalanalysis.Both limitationscall forthenecessityofameta-analysis

on reclaimed soils properties since meta-analysis allows researchers to

simultaneouslystudymultiplefactorsofaparticularissueacrossabroadscaleand

findthehiddentrends(ArnqvistandWooster1995).

Other thanmeta-analysis, sincemany researches have built the foundation of

basicphysical,chemicalandbiologicalpropertiesofreclaimedoilsandssoils,more

researches may start to shift toward some second- and third-order effects of

reclaimedsoils.Forexample,more indepth investigationonvegetationresponses,

localhydrologychangeandwildlifepopulationbehaviorandrecoveryinreclaimed

standsallcanberesearchedinthenearfuture.

Lastbutnotleast,Ifoundthatmanyresearchesthatstudiedtheeffectsoftime

on reclaimed soil properties used earlier sampled soils as their reference soils.

Includingtheoriginalsamplesofreclamationmaterialsattimezerowhenpossibleis

recommended for future time-effect researches since the time-zero samples may

providemoresoundandeffectiveevidencesof for theeffectsof timeonreclaimed

soilproperties.

48

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