REVIEWARTICLE

Towards Developing a Functional-Based Approachfor Constructed Peatlands Evaluation in the Alberta OilSands Region, Canada

Felix Nwaishi & Richard M. Petrone & Jonathan S. Price &

Roxane Andersen

Received: 21 March 2014 /Accepted: 23 December 2014# Society of Wetland Scientists 2015

Abstract Peatlands support vital ecosystem services such aswater regulation, specific habitat provisions and carbon stor-age. In Canada, anthropogenic disturbance from energy ex-ploration has undermined the capacity of peatlands to supportthese vital ecosystem services, and thus presents the need fortheir reclamation to a functional ecosystem. As attempts arenow being made to implement reclamation plans on post-mining oil sands landscapes, a major challenge remains inthe absence of a standard framework for evaluating the func-tional state of a constructed peatland. To address this chal-lenge, we present a functional-based approach that can guidethe evaluation of constructed peatlands in the Alberta oil sandsregion. We achieved this by conducting a brief review, whichsynthesized the dominant processes of peatland functional de-velopment in natural analogues. Through the synthesis, weidentified the interaction and feedback processes that under-line various peatland ecosystem functions and their quantifi-able variables. By exploring the mechanism of key ecosysteminteractions, we highlighted the sensitivity of microbially me-diated biogeochemical processes to a range of variability inother ecosystem functions, and thus the appropriateness ofusing them as functional indicators of ecosystem condition.Following the verification of this concept through current pilotfen reclamation projects, we advocate the need for further

research towards modification to a more cost-efficient ap-proach that can be applicable to large-scale fen reclamationprojects in this region.

Keywords Alberta oil sands . Biogeochemical processes .

Constructed peatlands . Ecosystem functions . Reclamationevaluation

Introduction

Since the early 17th century, northern peatlands have becomeincreasingly pressured from anthropogenic disturbances, asdrainage for agricultural improvement became a commonpractice, and as the demand for peat as horticultural substrateand fuel grew (Martini et al. 2006). More recently, the discov-ery of oil sands deposits beneath some boreal forest peatlandsin north-western North America have resulted in one of theworld’s largest industrial exploitation of pristine peatland eco-systems (Rooney et al. 2012). In this region, open-pit miningfor oil sands involves the total stripping of peat layers, leavinglandscapes with very large pits approximately 100 m in depth(Johnson andMiyanishi 2008). The outcome of this process isa complete loss of peatlands and their associated ecosystemservices (ES) such as water storage and cycling, habitat sup-port, and storage of carbon (C) and nutrients.

The environmental regulatory framework for Alberta oilsands development requires the energy industries to returnpost-mining landscapes to equivalent land capabilities, where“the ability of the land to support various land-uses after con-servation and reclamation is similar to the ability that existedprior to industrial development on the land, but the individualland uses will not necessarily be identical to pre-disturbanceconditions” (Alberta Environment 2009). Because of the foot-print of oil sands operations (i.e. a fragmented landscape

F. Nwaishi (*)Department of Geography & Environmental Studies, Wilfrid LaurierUniversity, Waterloo, ON N2L 3C5, Canadae-mail: nwai5240@mylaurier.ca

R. M. Petrone : J. S. PriceDepartment of Geography & Environmental Management,University of Waterloo, Waterloo, ON N2L 3G1, Canada

R. AndersenEnvironmental Research Institute, University of the Highlands andIslands, Castle Street Thurso, Caithness KW14 7JD, Scotland, UK

WetlandsDOI 10.1007/s13157-014-0623-1

without remnants of the pristine structure), this regulatory ob-ligation can only be achieved through reclamation, which willinvolve the complete re-creation of landforms and ecosystemssuch as fen peatlands that dominated the pre-disturbance land-scape in this region (Vitt and Chee 1989). However, consid-ering the notion that several decades are required for the ini-tiation of the peat accumulation function in a peatland (Clymo1983), peatland reclamation presents a significant challenge.To begin to address this challenge, attempts are now beingmade to design fen ecosystems on the post mining oil sandslandscape. For example, Syncrude Canada Ltd.’s Sandhill FenResearch Watershed Initiative constructed a landscape (basedon hydrologic knowledge and intuition) to support peatlanddevelopment on a thin (~50 cm) layer of peat covering a con-structed valley system (Wytrykush et al. 2012). Similarly,Price et al. (2010) presented a concept for the Suncor Pilotfen, which was tested with a numerical groundwater model.The model suggested that the creation of fen peatlands onpost-mining landscape may be possible if peat is salvagedbefore mining and placed in a hydrogeological setting thatcan sustain the requisite wetness conditions required for theestablishment of peatland vegetation and stable hydrologicconditions. The difference between these pilot fen designs isthat the Syncrude fen uses a managed water reservoir to sup-ply flows to the system,while the Suncor fen is designed tohave a self-sustained hydrology (requiring no managed watersupply). These pilot studies involve the transfer of peat from adonor site to a recreated landscape, to form the constructedpeatland. Although this approach will fast-track the initiationof peat accumulation process in constructed peatlands, it is notknown if the transferred peat will support ecohydrologicalfunctions similar to those present in natural analogues in thelong run. Hence, there is need to track the recovery ofreclaimed oil sands peatlands, especially at the early stagesof these pilot projects. These projects provide the opportunityto develop a better understanding of the key ecohydrologicalindicators for the evaluation of constructed fen’s trajectory.

Considering that fen reclamation is a new and untested con-cept, there is a dearth of information on the appropriate ecologicalapproach for monitoring the trajectory of reclaimed peatlands. Atpresent, the framework available for the evaluation of reclaimedsites in this regionwas developed for otherwetland forms such asopen-water marshes, and is based on the concept of indicatorspecies (Rooney and Bayley 2011). The appropriateness of sucha framework for reclaimed peatland evaluation is contentiousbecause relative to otherwetland types, peatlands are functionallyand structurally unique; they are products of the advanced stagesof wetland succession (Bauer et al. 2003), and support more vitalfunctions (Vitt 2006). For example, unlike the open watermarshes, which will lose most of their water by evaporation,peatlands in the Alberta Oil Sands region within the WesternBoreal Plains conserve water and acts as reservoirs that supplyupland ecosystems during drought periods (Devito et al. 2005;

Petrone et al. 2007a), and as such, the key ecosystem servicesthat they deliver (Grand‐Clement et al. 2013) cannot be effec-tively assessed with the indicator species approach alone. Also,the presence of indicator species (Stapanian et al. 2013) does notaccount for the functional state of a reclaimed ecosystem, be-cause an indicator species might be present in a reclaimed site,yet not functionally equivalent to natural analogues as a result ofabiotic alterations (Dale and Beyeler 2001). That is, indicatorspecies may be present although ecohydrological conditions(i.e. water use efficiency, nutrient cycling) are not suitable forthe long-term sustainability of that species in the reclaimed sys-tem. Hence, if the framework used in evaluating wetland recla-mation is applied to peatlands, such evaluations will be limited toassessing reclamation based on the vegetation community struc-ture and biotic conditions without providing much insight onpeatland ecosystem functioning: i.e. the interaction between bi-otic and abiotic ecosystem processes that supports the continuousflow of energy to sustain ecosystem services (e.g. carbon seques-tration) in the reclaimed peatland.

It can be argued that the indicator species approach has beenused effectively to evaluate the attainment of restoration goals inrestored vacuum-milled peatlands of eastern Canada (Gonzálezet al. 2013), and perhaps peatland restoration concepts should beapplicable to reclamation. However, the difference between theconcept of peatland reclamation (i.e. recreating a peatland eco-system where it has completely been removed from the land-scape) and restoration (i.e. returning peatland functions on dis-turbed peatland remnants) presents the need for developing arigorous framework that can capture the complexities associatedwith reclaimed peatlands. For instance, the planting designadopted in the Suncor’s pilot fen reclamation project involves acombination of vegetation assemblage found in different fentypes (saline, fresh water, rich and poor fen) within this region(Daly et al. 2012). The idea is to select for native species that cansurvive the altered abiotic conditions expected in this constructedecosystem (Harris 2007). This concept could result in multiplesuccessional endpoints (Fig. 1a and b), making the indicatorspecies approach inappropriate in the latter case because, unlikein restored bogswere the successional endpoint is known (i.e. therecovery of a typical Sphagnum moss carpet), that of reclaimedoil sands fen is relatively unknown due to multiple possibilities(Fig. 1a and b).

Interactions between the combined native vegetation spe-cies assemblages or invasion by non-native species and alteredabiotic conditions (e.g. altered hydrology and water quality) inreclaimed sites could lead to the emergence of new ecosys-tems. This has been observed in recreated landscapes(Lindenmayer et al. 2008), which have been classified intohybrid and novel ecosystems based on the degree of transfor-mation from natural analogues (Hobbs et al. 2006). A hybridecosystem is one that is functionally similar but structurallydifferent (e.g. combination vegetation species that occur indifferent natural environments) from natural analogues, while

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novel ecosystems have functional and structural characteris-tics that are completely different from natural analogues(Hobbs et al. 2009). Based on the definition of “equivalentland capabilities” in the oil sands reclamation context, the landuses targeted by reclamation can be classified as hybrid eco-systems, which could evolve into novel ecosystems as a resultof the altered biotic and abiotic conditions anticipated in fenecosystems recreated on post-mining oil sands landscapes(Harris 2007; Daly et al. 2012). The management of ecosys-tems with a combination of rare species and/or altered abioticconditions will require adopting a novel approach that focuson understanding their functioning. Hence, there is a need toshift from the traditional indicator species approach to a

comprehensive functional approach that can improve our un-derstanding of the functional characteristics of these recreatedecosystems through a number of pilot studies, which will in-form future large scale reclamation projects.

Developing a functional-based reclamation evaluationframework requires an understanding of key functional pro-cesses in natural analogues, the identification of quantifiablemeasures of specific ecosystem functions targeted in reclama-tion, and a comprehensive monitoring program that can cap-ture the evolutionary interactions between biotic and abioticvariables in the reclaimed ecosystem. We propose a conceptthat will guide the evaluation of oil sands-reclaimed fen eco-system from a functional perspective, which is more suitable

Ini�al stage of fen reclama�on

Increasing degree of bio�c altera�ons

Incr

easi

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- No change in vegeta�on structure.

-Change in water chemistry, hydrology

and other abio�c variables

Slight change in vegeta�on structure in response to rapid

change in abio�c condi�ons

Rapid change in vegeta�on structure in response to slight

change abio�c condi�on

- Rapid change in vegeta�on structure

without any change in water chemistry,

hydrology and other abio�c variables

a

b

Fig. 1 Schematic representationof: a) potential reclamationtrajectories in response to a rangeof alterations in biotic and abioticcomponents of the constructedpeatland ecosystem; and b) anexample of possible endpointsthat might result from themultipletrajectories, specifically inresponse to various chemicalgradients

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for assessing what is essentially primary succession that hasbegun at some “non-initial” state, and could lead to novelecosystems. We demonstrate the appropriateness of this con-cept by: 1) conducting a brief review to synthesize the process-es that dominate peatland succession and how interactionsbetween these processes supports specific ecosystem function;2) identifying the key ecosystem variables that can be used asquantifiable measures of specific ecosystem functions; and 3)exploring the mechanisms of key ecosystem interactions toidentify the most suitable integral indicator of ecosystem func-tioning. Hence, the aims of this paper are twofold: 1) to initiatethe development of a framework for integrating the diverseresearch data generated from on-going oil sands reclamationpilot studies, towards understanding the functioning of con-structed peatlands; 2) and to stimulate discussions on refiningthe current reclamation evaluation practices towards afunctional-based approach that will be most appropriate forconstructed peatland evaluation in the Alberta oil sands region.

Processes of Peatland Initiation and Succession

Peatland development is initiated by physical processes,which are driven by environmental factors such as climate,relief and hydrogeology. The interactions between these

external abiotic factors produce allogenic processes, whichfeedback on the internal ecosystem variables and autogenicprocesses such as plant and microbial community succession(Payette 1988). Primary peat formation, terrestrialization andpaludification are the three main processes that have dominat-ed the initiation of northern peatlands (Halsey et al. 1998;Ruppel et al. 2013 and the references therein). These threeprocesses have been identified across North American borealforest peatlands, with paludification being the dominant pro-cess over all northern peatlands (see Fig. 2; Vitt 2006; Ruppelet al. 2013; Inisheva et al. 2013). Kuhry and Turunen (2006)described paludification as the inception of peat formation onformerly dry mineral soil substrate occupied by terrestrial veg-etation, following such change in local hydrological condi-tions that result in the inundation or accumulation of runoffwater in topographic lower points. The water-logging of aformerly dry mineral soil substrate alters allogenic and auto-genic processes such as depth of water table and nutrient min-eralization rates, respectively. Soil saturation leads to anaero-bic soil conditions and reduced organic matter breakdown,which results in decreased nutrient cycling. The depositionof eroded nutrient-rich organic matter and dissolved sedimentsby runoff water into the paludified site increases anaerobicoxidation processes such as nitrous oxide (N2O) and methane(CH4) production (Smemo and Yavitt 2011). Thus, at the early

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- ∆ in water by decompand rhizode- Competitionutrients beplants and

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- ↑ Peat depth- ↓ Groundwateinfluence - ↑ Light and ↑

↑ Moisture de

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- ↑ NPP - ↑ CH4 produc- ↑ Biomass accumulation

Mineralisati

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er

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on rate

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tinental Clim

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- Isolation from roundwater inf

- Precipitation fe↓ WT

CO2

- ↑ Acidity and a- ↓ NPP - ↓ Biomass acc

↓ Mineralisatio↓ Litter quality

ate

OmbrotrophicStage

Sedge litter peat

CH4

Woody litter

Moss carp

luence d

2

WT

llelopathy

umulation n rate (CN ratio)

Bog

r peat

et

LEGENDS

= Ja

= Se

= Bla

= Hy

= F

= Eric

ack pine

edge tussocks

ck spruce

drophytes

loa�ng mats

aceous shrubs

Fig. 2 The successional stages of a natural peatland under an idealcontinental boreal climate condition, highlighting dominant allogenicand autogenic processes at various stages along the successionaltrajectory. The thicker arrows indicate the dominant flux at different

stages. The horizontal lines extending from the middle to both ends ofthe trajectory line indicated that microbial mediated biogeochemicaltransformation are dominant in all successional stages due to microbialcompetition for nutrients

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stage of paludification, which is synonymous with therewetting of dewatered peatlands (Zerbe et al. 2013), the pres-ence of nutrient-rich substrates such as mineralized peat willmake the paludified site a hot spot of greenhouse gas (GHG)production (McClain, et al. 2003).

The persistence of inundated conditions in a typical borealforest retards the development of the Pinus banksiana (jackpine) roots due to oxygen deficiency and reduced nutrientcycling in the anoxic rooting zone (Tiner 1991). This leadsto the gradual senescence of Pinus banksiana roots, thenstands, creating more favorable conditions for hydrophyticplants and trees that can grow in waterlogged conditions suchas Picea mariana (black spruce). At this stage, the poor nutri-ent quality (high C:N ratio) of the decomposing Pinusbanksiana litter, further reduces nutrient cycling by alteringthe nutritional status of the decomposer communities(Thormann et al. 2001). Therefore, the litter quality (i.e. afunction of C:N ratio) of the reclamation substrate will beone of the factors controlling the rate of nutrient cycling atthe early stages of reclamation. Following the structural col-lapse of Pinus banksiana stands, opening of the forest coverabets allogenic processes (e.g. reduced precipitation intercep-tion and low evapotranspiration losses) that creates conditionsrelevant to the invasion of hydrophilic plants, which marks thefirst stage of vegetation succession (Mitsch and Gosselink2000; Tuittila et al. 2007). At this stage, the physiologicalstructure of the site is similar to an open swamp in transitionto a marsh, containing vascular plants that are adapted to thewaterlogged conditions through the formation of tussocks,large intercellular spaces (aerenchyma) and floating mats(Rochefort et al. 2012). Part of the dead Pinus banksiana litteris deposited into the anoxic zone where decomposition willcontinue at a slower rate due to the metabolic energy con-straints associated with phenolic inhibition under anoxic con-ditions (Shackle et al. 2000). The aerated portion of the sub-merged Pinus banksiana trunks and the floating mats createsaerobic microsites that are colonized by aerobic microorgan-isms. Aerobic microsites are hot spots of litter breakdownwhere microbial secretion of extracellular enzymes like phe-nol oxidase causes efficient degradation of recalcitrant organicmatter by releasing extracellular hydrolase enzymes from phe-nolic inhibition (Shackle et al. 2000; Freeman et al. 2004).Thus, aerobic microsites form the peat producing layer, oracrotelm in a developing peatland (Ingram 1979). The partial-ly decomposed plant litter produced in the acrotelm are sub-merged into the deeper anoxic zone, the catotelm, whichforms the long-term peat accumulator in a peatland (Clymoet al. 1998).

The biochemical composition of decomposing litter com-bines with rhizodeposition to alter the water chemistry andbiogeochemical processes of developing peatlands (Stracket al. 2006; Bradley et al. 2008). For instance, the persistenceof mineroptrophy (nutrient-rich conditions) and high

photorespiration increases the net primary production (NPP)of Carex sedges (Dise 2009). High productivity of Carexsedges have been associated with high CH4 emission (positivefeedback) as a result of their aerenchymatic tissues, whichserve as conduits for transporting gases from the anoxic zoneto the atmosphere (Yavitt et al. 2000; Lai 2009 and referencestherein). Hence, at the intermediate stage of peat developmentwhen minerotrophic sedges form the dominant plant function-al types (PFT), the flux of CH4 from the constructed peatlandis expected to be at its peak in the absence of other externalforcing factors such as sulfate (SO4

2−) deposition (Dise andVerry 2001). Higher NPP also accelerates litter turnover(Laiho 2006), and the subsequent increase in sedge peat accu-mulation. Humification of accumulated peat leads to acatotelm that is characterized by higher bulk density, lowerspecific yield, pore size distribution and hydraulic conductiv-ity relative to the acrotelm peat (Clymo 1992; Price et al.2003; Holden 2005; Petrone et al. 2008). These peat proper-ties control the water regulation and storage functions inpeatlands (Fig. 3).

With increased humification of the catotelm peat, the up-welling of nutrient-rich pore water from the mineral substrateis retarded by three processes: 1) the production of organicacids during peat humification increases the competition be-tween hydrogen ions and cation nutrients (Damman 1978); 2)the low hydraulic conductivity of the highly humified peatreduces the upwelling of cation-rich solutes through the peatmatrix; and 3) diminishing head gradients as the elevation ofthe mound increases. Thus, a continuous increase in catotelmpeat thickness gradually isolates the acrotelm from theminerotrophic groundwater, resulting in ombrotrophic(nutrient-poor) conditions (Vitt 2006). The appearance ofSphagnum mosses is a floristic indicator of ombrotrophy, afinal stage in peatland succession (Mitsch and Gosselink2000; Tuitti la et al. 2013). Ombrotrophication isbiogeochemically associated with reduced mineralizationrates and NPP (Bayley et al. 2005), lower CH4 and N2O emis-sion, with CO2 being the major GHG (Martikainen 1996;Regina et al. 1996), and high acidity and production ofallelochemical that slows the rate of nutrient cycling(Bradley et al. 2008).

Peatland Ecological Functions and Related EcosystemVariables

All the successional stages observed in natural peatlands maynot occur in a constructed peatland, because reclamation at-tempts to skip initial successional stages by transferring peatfrom a donor peatland to a constructed site. Hence, from afunctional perspective, it is expected that constructedpeatlands may start from the intermediate stage of naturalpeatland succession. To be classified as an “equivalent land

Wetlands

capability”, ecohydrological conditions (especially biogeo-chemical functions) in the constructed peatland are also ex-pected to align with those observed at the intermediate stage innatural analogues. Peatland ecological restoration targets therecovery of hydrologic regulation and water storage (Priceet al. 2003; Holden 2005), biogeochemical transformation(Limpens et al. 2008; Dise 2009), vegetation species succes-sion (Bauer et al. 2003; Tuittila et al. 2007), primary produc-tion and decomposition rates (Clymo et al. 1998; Frolkinget al. 2001). Since these ecosystem functions vary along thesuccessional pathway of a developing peatland (Fig. 2), ourunderstanding of the functional state of a reclaimed peatlandcan be improved by aligning their functional characteristicswith those observed in a natural analogue, to find a suitablereference along the successional pathway that can be used forevaluating a given site. However, assessing the functionalstate of an ecosystem requires identifying the quantifiableecosystem variables that are associated with specific peatlandecosystem functions (Table 1).

Hydrologic Regulation and Water Storage Functions

Peat physical properties such as pore size distribution, specificyield, hydraulic conductivity and bulk density control the

movement and storage of water in the peat (Boelter 1968).The hydrologic regulatory function of peatlands is a productof the range of variability between these peat properties withinthe acrotelm and catotelm (Fig. 3; Holden 2005; Petrone et al.2008). The partially decomposed property of plant litter in theacrotelm forms a porous medium through which water readilyinfiltrates into the peat layers. The ease of infiltration throughthe acrotelm is due to the presence of many large pores (highaverage pore size) in partially decomposed plant litter, whichallow a greater proportion of the infiltrating water to bedrained by gravity (Price et al. 2003). As water infiltrates intothe peat matrix, the increase in water table is modulated by therelatively high specific yield, as is its decline as water is lost todrainage and evapotranspiration. During drier periods whenthe water table is lower, the well-drained large-pore matrix inthe upper acrotelm becomes a poor conductor of water andevapotranspiration losses are curtailed (Price and Whittington2010). The rate of lateral seepage is defined by the hydraulicconductivity of the porous peat; a function of the degree ofpeat decomposition and compression. When the water table ishigh, the acrotelm has high transmissivity and can readilyshed water, whereas during dry periods when the water tableis low, the highly decomposed catotelm peat characterized byvery small pores restricts lateral water loss to maintain waterstorage in peatlands. Consequently, peatlands have the ability

Biogeochemical Transformation Function

Active Microbial Community

Water Chemistry

GHG Fluxes

Redox Potential

Photosynthetic Efficiency

Biomass Accumulation Rate

Plant Litter Quality

Aquatic C Fluxes

Primary Production and Decomposition

Vegetation Succession Function

Vegetation Community Diversity

Community Competition

Seed rain and invasion potentials

Peat Depth

ET Losses

Watertable Fluctuation

Hydrologic Regulation Function

Peat Physical Properties

Fig. 3 Conceptual diagram demonstrating the dominant interaction and feedbacks processes that support various ecosystem functions in peatlands. Thedouble-pointed lines indicate a feedback interaction while single-pointed ones indicate a one-way interaction and points towards the dependant variable

Wetlands

Tab

le1

The

major

peatland

ecosystem

functio

nalcharacteristicstargeted

inreclam

ation,

thequantifiablevariablesassociated

with

specificecosystem

functio

ns,relativ

ecostof

evaluatio

n,levelof

expertiserequired

andtheapproach

used

inassessingkeyecosystem

processesin

variouspeatland

ecologicalevaluatio

nstudies

Peatland

functio

nal

characteristics

Quantifiablemeasuresof

ecosystem

functio

nRelative

cost

Levelof

expertise

required

Approachesused

inmonito

ring

keyecosystem

processesin

Peatland

ecologicalevaluatio

nstudies(references)

Hydrologicregulatio

n•Stratification

ofpeat

hydrau

licprop

erties

(specificyield,

porosity,h

ydrauliccond

uctivity,b

ulk

density)

andCatotelm

thickn

essa

$++

•Dipwellsan

dpiezom

eter

neststo

mon

itor

water

tabledy

namicsa(Price

etal.2010)

$+

•Ana

lysisof

peat

hydrau

licprop

erties

a(Price

2003;P

etrone

etal.2008;Cunliffeetal.2013)

•Evapotranspiration(ET)losses

andwater

balancea

$$$

+++

•Contin

uous

measuremento

fatmospherichydrologicflux

a(Petrone

etal.2001,2004)

Biogeochemical

transformation

•Greenho

usegas(G

HG)flux

esa

$$+++

•Cha

mberan

dmicrometeorologicalm

easurementsof

GHG

flux

esa(Petrone

etal.2001,

2003;W

addingtonetal.2

003;

StrackandWaddington2007)

•Redox

potentiala

$$++

•Redox

andDOmeasurements(Thomas

etal.1995;

Niederm

eier

andRobinson2007)

•Dissolved

oxygen

(DO)

$$++

•Aqu

aticcarbon

flux

esa

$$++

•Aqu

aticCflux

measurements

a(W

addingtonetal.2008;

Hölletal.2009)

•Microbial

activity

$$++

•MicroRespexperiments(A

ndersenetal.2013b)

•Mineralizationrates

$$++

•In-situnu

trientsmineralizationexperiments

a(M

acraeetal.2013)

Vegetationsuccession

•Vegetationdiversity

a$

+++

•Vegetationsurvey

a(CooperandMacDonald2000;T

ritesandBayley2009).

•Seedbank/rainandinvasion

potentials

a$

++

•Com

munity

dynamics

$$+++

•Rem

otesensingtechniques

(Ozesm

iand

Bauer2002;A

ndersonetal.2010;Knothetal.2013)

Biodiversity

andtrophic

interactions

•Fun

ctiona

lmicrobial

diversity

a$$$

+++

•Microbial

function

aldiversity

a ,metagenom

ics(A

rtzetal.2008a;P

reston

etal.2012;

Andersenetal.2013a,b;B

asiliko,etal.2013)

•Sp

eciesrichness/diversity

forvarioustaxa

(other

than

plants)

$+++

•Sp

eciesnumberandinteractions

(Desrochersetal.1998;

WattsandDidham

2006)

Prim

aryproductio

nand

decompositio

n•Abo

vean

dbelowgrou

ndbiom

assaccumulation

a$

+•Vegetationbiom

assmeasurementa(Cam

illetal.2001)

•Gross

photosynthesisandecosystem

respiration

a$$

++

•Chambermeasuremento

fgrossphotosynthesisandecosystem

respiration

a(Frolkingetal.

1998;M

oore

etal.2002).

•Organ

icmatterqu

ality,e.g.C:N

ratioof

littera

$$++

•Organ

icmatteran

alysisby

FTIR

spetroscop

ya(Basiliko

etal.2007;

Artzetal.2008b).

•Lon

g-term

litterba

gexperiments

a(Thorm

annetal.2

001;

Moore

etal.2007;

Luccheseetal.2010)

The

relativ

ecostismostly

basedon

analytical/in

strumentalrequirem

ent:procedures

that

canbe

readily

implem

entedin

thefieldwith

outmuchinstrumentatio

naredenotedas

$;thosethat

require

instrumental/analyticalprocessing,butwherethemethods

arewelld

eveloped

andinexpensiveare$$;and

thoseforwhich

thereisspecialistequipmentrequiredand/or

technicalsupportare$$$.Similar

idea

appliesto

denotatio

nsforlevelo

fexpertise

aQuantifiableecosystemvariablesandmeasurementapproachused

inon-going

pilotreclamationprojectsintheAlbertaoilsands

region.T

hose

inboldtextindicatewhatisconsidered

themostimportant

variablesandmeasurementapproach

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to self-regulate their hydrology and keep water levels relative-ly stable (Rochefort et al. 2012).

In an intact peat layer, hydraulic conductivity, average poresize and specific yield are expected to decrease down thediplotelmic profile (from acrotelm to catotelm), while bulkdensity increases (Clymo 1992). The gradual accumulationof decomposing litter during natural peatland development(Fig. 2) creates the diplotelmic peat layers. This attribute iscompromised in constructed peatlands because the process ofsite preparation and donor peat deposition results in afragmented peat layer, which lacks the stratified propertiesthat support the hydrologic regulatory functions of intact peat.The implications of this will be seen in the establishmentlimitations of native peatland vegetation species. For instance,regenerating mosses with large open pores are incapable ofgenerating a strong capillary rise of water from the underlyingfragmented peat because of the abrupt transition in peat hy-draulic properties, notably water retention capacity (McCarterand Price 2013). Decomposition and compression at the baseof the regenerating moss profile may take decades, but isnecessary to modulate the hydrology in a way that favourscarbon accumulation (Taylor 2014) Thus, the recovery of peatstratification, which can be assessed by monitoring the peatphysical properties along the peat profile (Table 1), will be aneffective proxy for evaluating the recovery of hydrologic reg-ulatory functions in a reclaimed peatland. This evaluation isrelatively easy to implement, and can be achieved within thefrontier of funds available to small reclamation researchgroups. The root architecture of reclamation pioneer vegeta-tion (Carex species) presents some potential to facilitate therecovery of peat stratification through rhizosphere effect, dur-ing root growth and development in constructed peatlands.Mulching has been used to promote the recovery of microhydrologic functions, such as soil moisture regulation in cut-over peatland restoration (Price et al. 1998; Petrone et al.2004).

Biogeochemical Transformation Functions

The hydrologic regulatory function in peatlands delineates thepeat column into hydrological diplotelmic (oxic and anoxic)layers, which creates a redox gradient. Another important mi-crobial ecological niche exists at the interface of the hydrolog-ical diplotelmic layers, a biogeochemical hotspot named themesotelm (Clymo and Bryant 2008). This is the layer wherethe mean annual depth of water table fluctuates within theacrotelm and can be quantitatively defined as plus or minusthe standard deviation of the mean annual depth of water tablewithin the acrotelm. Hence, the peat column can therefore bedescribed as a triplotelmic biogeochemical system.

Peatland biogeochemical transformations are products ofthe feedback interactions between microbial activity and

chemical dynamics (Fig. 3; Hunter et al. 1998). The type, rateand pathways of biogeochemical processes are vertically strat-ified in response to the unique attributes of each of the peatlayers. Microbial functional groups, which act as the biologi-cal engines of peatland biogeochemical transformation, showa vertical stratification along this triplotelmic peat layer (Artz2009; Andersen et al. 2013a). In the acrotelm, the availabilityof oxygen raises the oxidation state of inorganic elements,while anoxia in the catotelm reduces oxidized compounds.These changes in oxidation states involve redox reactions,which form the basis of microbially mediated biogeochemicalprocesses in peatlands (Hunter et al. 1998; Falkowski et al.2008).

Oxidized forms of inorganic compounds such as NO3− and

Mn4+ are readily available to plant roots within the oxic peatlayer since aerobic conditions efficiently sustain the energydemand of microbial activities. However, in the anoxic peatlayers, anaerobic microorganisms are more efficient at utiliz-ing the oxidized forms of some plant essential nutrients (e.g.NO3

−, Mn4+, Fe3+ and SO42−) as alternative electron accep-

tors. Consequently, this leads to the reduction in oxidationstate of inorganic plant nutrients, and subsequent productionof gaseous compounds like N2O and CH4 (Martikainen 1996).As with the early stage of peatland development, reductionprocesses may dominate at the initial stage of constructedpeatland development, when the acrotelm layer is very thin.Denitrification, the reduction process responsible for the re-moval of excess mineral nitrogen (N) compounds from theenvironment, is not a common process in natural peatlands(Dise and Verry 2001; Seitzinger et al. 2006). But in the casewhere peatlands receive elevated inputs of inorganic-N fromwet and dry atmospheric deposition (e.g. ~25 kg N ha−1 yr−1

rate of deposition have been reported for sites adjacent to anactive oil sands mine; Proemse et al. 2013), denitrification isdominant (Aerts 1997). Denitrification may also serve as akey mechanism for removing the excess N present in themineralised donor peat used in constructed peatlands, whichwill be necessary for reducing N-toxicity to sensitive peatlandplants (e.g. Sphagnum moss) and eutrophication of down-stream ecosystems (improved water quality).

Methanogenesis and sulfur reduction (SR) are well-studiedbiogeochemical transformation processes in peatlands (Lai2009 and references therein) and constructed wetlands (Wuet al. 2013 and references therein). Based on the electron tow-er theory (Laanbroek 1991), these transformations occur atvery low redox potentials (about −150 mV) when the reduc-tion process becomes strictly anaerobic, involving only obli-gate anaerobes like sulfur-reducing bacteria and methanogens.Within this negative redox gradient, SR outcompetesmethanogenesis in the utilization of available substrate as aresult of thermodynamic and kinetic advantages (Dise andVerry 2001; Vile et al. 2003; Gauci et al. 2005). Contrary tothe previous thoughts that anaerobic CH4 oxidation is solely

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dependent on SR, evidence from recent studies suggests thatother undiscovered anaerobic CH4 oxidation pathways arepresent. This study further explained that the reduction innet CH4 flux often observed after SO4

2− addition to peatlandscould be as a result of gross CH4 production suppression andnot the stimulation of anaerobic methane oxidation (Smemoand Yavitt 2007). This is based on the premise that in mostcases, the SO4

2− concentration of natural peatlands is belowthe kinetic energy threshold required to stimulate sulfate-dependent anaerobic methane oxidation (Schink 1997).Therefore, this lends more support to the circumstantial evi-dence that other unappreciated anaerobic pathways that in-volve methane oxidation or methanogenesis inhibition (e.g.reverse methanogenesis and NO3

−- dependent anaerobicmethane oxidation) are present in peatlands, and could ac-count for the imbalance between anaerobic methanogenesisand aerobic CH4 consumption (Smemo and Yavitt 2011 andthe references therein).

However, the specific electron acceptors involved in theseanaerobic pathways were not determined by current studies,which consistently demonstrate that in peat soils, the additionof common electron acceptors (i.e. NO3

−, Fe3+ and SO42−) do

not stimulate anaerobic methane oxidation (Smemo and Yavitt2007; Gupta et al. 2013). These findings, however, may befraught with the limitations associated with in-vitro studies,which fail to account for other controls that may complementthese common electron acceptors under in-situ conditions(e.g. rhizosphere effect and re-oxidation associated with watertable fluctuations). In contrast to the electron acceptor/kineticenergy limitations present in natural peatlands, anaerobic CH4

oxidation and/or suppression are expected to be dominantprocesses in constructed peatlands within the Alberta oil sandsregion. This follows the observation that ongoing industrialdevelopments in this region are linked to elevated throughfalland bulk deposition of reactive N and S, with mean annualdeposition rates of 25 and 20 kg S ha−1 yr−1 measured onterrestrial sites near (~3 km) an active oil sands development(Fenn and Ross 2010; Proemse et al. 2012, 2013). Althoughthese deposition rates are low compared to those of otherNorth American, European and Asian sites affected by elevat-ed anthropogenic deposition (Dentener et al. 2006), the max-imum rate of S deposition (39.2 kg SO4-S ha−1 yr−1) is higherthan what was applied by Dise and Verry (2001) to stimulatethermodynamically favorable processes at the expense ofmethanogenesis.

Depending on the rate of methanogenesis and/or anaerobicCH4 oxidation, part of the CH4 produced in a peatland isliberated from the catotelm to the atmosphere by diffusionthrough the peat matrix, ebullition (release of bubbles fromwater-saturated peat) and plant transport (Strack et al. 2006;Lai 2009). In the mesotelm, part of the CH4 diffusing throughthe peat pores undergoes aerobic oxidation by methanemonooxygenase (MMO) enzyme activity of methanotrophic

bacteria (Hanson and Hanson 1996). Considering the non-specific catalytic behaviour of monooxygenase enzyme andsimilarities between CH4 and NH4

+ (Holmes, et al. 1995),ammonium monooxygenase activity can stimulate eitherCH4 or NH4

+ oxidation in the mesotelm. This presents amechanism that can couple atmospheric N deposition andassociated denitrification to CH4 sink functions in reclaimedpeatlands adjacent to active oil sands development. Themesotelm and other aerobic microsites within the anaerobiczones (e.g. the rhizosphere of sedges) are a very critical nichein the global C biogeochemical cycle because the oxidation ofCH4 can reduce the global warming potential of peatland CH4

emission by 3.7 times per molecule per 100 years relative toCO2 (Lashof and Ahuja 1990; Lelieveld et al. 2002; Shindellet al. 2005; Frolking and Roulet 2007). Hence, the develop-ment of a functional mesotelm in constructed peatlands isessential to mitigate the potential contribution of thesepeatlands to global warming. Since dominant hydrologicalregimes poses a major control on the periodically oxic/anoxic mesotelm (Clymo and Bryant 2008), the absence ofhydrologic regulatory function at the early stage of reclama-tion may result in limited aerobic CH4 oxidation potential.This suggests that anaerobic CH4 oxidation and/ormethanogenesis inhibition could be the dominant pathwaysof CH4 sink function until a functional mesotelm layer isformed in the constructed peatlands.

Ecosystem variables such as GHG fluxes are products ofthe biogeochemical transformation functions in peatlands, andcan therefore be used as quantifiable proxies to assess the stateof biogeochemical transformation functions in constructedpeatlands. Also, since oxygen limitation in the saturated peatlayer is a major factor that determines the rate of biogeochem-ical transformations (Armstrong 1967); the concentration ofdissolved oxygen (DO) and redox potential can be used as aquantifiable ecosystem variable for assessing the potentiallydominant redox process in constructed peatlands.Furthermore, measuring microbial activities, using recent ad-vanced techniques in environmental genomics and stable iso-tope probing (Manefield et al. 2002; Whiteley et al. 2006) canbe explored as a means to identify active taxa (through in situextraction and analysis of rRNA) that can then be related tospecific biogeochemical functions. Although this evaluationapproach might seem unrealistic within the scope of small-scale research, these approaches are essential to identify theactive portion of the microbial community and to associatespecific micro-organisms with key processes under given en-vironmental conditions (Basiliko et al. 2013). Alternatively,within the scope of limited resources, evaluation of temporalvariability in water table depth, microbial activity, nutrientmineralization rates and GHG fluxes can be explored to un-derstand biogeochemical functioning of the ecosystem.Although it can be argued that these can only provide specu-lative information on the dominant microbially-mediated

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biogeochemical processes, the products of the processes(NO3

−, Mn4+, Fe3+ and SO42−) can be easily analyzed to iden-

tify dominant functions.

Vegetation Succession Function

Peatland vegetation species succession is the function thatenables peatlands to develop into a unique habitat that sup-ports biodiversity, a vital ecosystem service in pristinepeatlands. The water chemistry and dominant hydrologic con-ditions control the succession of vegetation species inpeatlands (Fig. 3; Tuittila et al. 2007). The recovery of vege-tation succession functions in oil sands constructed peatlandsis of utmost priority to reclamation stakeholders in the Albertaoil sands region. But concerns have been raised about theeffect of industrial effluents of salinity and napthenates-affected water from substrate materials used in constructingsurrounding hill slopes, on the recovery of this vital peatlandfunction (Price et al. 2010; Rooney and Bayley 2011). Theresponse of reclamation vegetation assemblages to altered abi-otic environment is unknown. However, greenhouse studies(Pouliot et al. 2012; Rezanezhad et al. 2012) demonstratedthat some vascular plants such as Carex species (e.g.C. aquatilis) as well as Calamagrostis stricta, can havestress-free growth in the current salinity and naphthenic acids(NAs) levels (~385 mg l−1 of Na salts and ~40 mg l−1 of NAs)present in oil sands process-affected water (OSPW). The samestudies also showed that peat forming bryophyte species (e.g.Bryum pseudotriquetrum, Dicranella cerviculata and Pohlianutans) could not tolerate these conditions. Considering thatfield conditions are more extreme relative to mesocosm con-ditions, the anticipated poor water quality presents a majorlimitation to the field establishment of diverse, native peat-forming vegetation species in oil sands constructed peatlands.Field observations have also shown that in wetlands wheresalinity tolerant vascular plants are dominant, biodiversity isvery low, leading to a “green desert” of vigorous plant standswith low diversity of insects and vertebrates (Trites andBayley 2009; Foote et al. 2013).

The findings from these studies suggest that establishing adiverse and analogous peatland vegetation community maynot be feasible at the early stages of constructed peatlanddevelopment in the Athabasca oil sands region. Since someminerotrophic vascular plants have shown a potential to be-come a tolerant pioneer species, constructed peatlands in thisregion may follow a PFTs succession similar to that observedin natural peatlands. However, the compromised chemical andhydrologic gradients anticipated in these sites might combinewith invasive species competition to derange the recovery ofnative peatland vegetation succession function. This lendsmore supports to the inappropriateness of using only an indi-cator species approach for the evaluation of constructed

peatlands in the oil sands region. Continuous (annual growingseason) vegetation surveys are being used to keep track ofcommunity competition, invasion potentials and vegetationsuccession in constructed peatlands. This measurement is veryimportant, but relatively labour-intensive in a large-scalestudy. Hence, there is a need for further research on the en-hancement of vegetation surveying through remote sensingtechniques.

Primary Production and Decomposition Functions

The capacity of peatlands to store carbon is due to an imbal-ance between the rates of NPP and decomposition, driven by acombination of hydrologic gradients, litter quality and waterchemistry (Thormann et al. 2001; Turetsky and Ripley 2005;Laiho 2006). NPP is a function of the photosynthetic efficien-cy of plants (Fig. 3), therefore varies among different peatlandPFTs (Laine et al. 2012; Tuittila et al. 2013). A study ofpeatland NPP suggests that among the PFTs present duringnorthern peatland succession, minerotrophic sedges have thehighest NPP, while ombrotrophic forbs have the lowest(Frolking et al. 2010). Considering the open structure of con-structed peatlands, the combination of high light saturationpotential in sedges (Busch and Lösch 1998), adequate photo-synthetic active radiation (PAR) in the continental boreal cli-mate (Frolking et al. 1998), and atmospheric N input from oilsands activities (Proemse et al. 2013) may result in very highNPP for pioneer salinity tolerant Carex species. In addition,high levels of nutrient deposition will also alter the litter qual-ity of pioneer vegetation by reducing the C: N ratio, whichwill accelerate litter decomposability (Fig. 3; Aerts et al.1995), and consequently affect the rates of carbon accumula-tion as peat (Bragazza et al. 2006). Hence, maintaining a nearsurface water table is essential to peat accumulation inreclaimed peatlands receiving high nutrient inputs and pro-ducing low refractory litter. It is uncertain, however, whetherthe fragmented peat substrate used in reclamation can main-tain a stable hydrologic regime and support near surface an-oxia for most of the growing season. Over time, if the hydro-logic regulatory function is not recovered, total decompsitionmay exceed NPP leading to net carbon loss.

Interactions Between Biotic and Abiotic Componentsof Peatland Functions

The goal of peatland reclamation is focused on creating a self-sustaining ecosystem that is carbon-accumulating, capable ofsupporting a representative assemblage of species, and resil-ient to normal periodic stresses (Daly et al. 2012). For anecosystem to be self-sustaining, the key ecosystem processesthat support various ecosystem functions need to be tightly

Wetlands

coupled, in order to maintain the continuous flow of energyrequired for sustained delivery of ecosystem services.Evaluating the actualization of reclamation goals will requirean integrated hydrological, biogeochemical and ecological re-search monitoring program that can capture the complex in-teractions between interrelated components of various ecosys-tem functions.

Exploring the interactions and feedback mechanisms thatunderline the tight coupling between ecosystem processes andfunctions will guide the integration of reclamation monitoringdata towards evaluating the functional state of a reclaimedecosystem. The conceptual model, (Fig. 3) illustrates themechanisms that sustain the ecosystem processes of peatlanddevelopment and succession (Fig. 2). Considering the multi-ple feedbacks that may result from simultaneous ecosystemprocesses, it is worthy to note that these interactions are non-unidirectional in nature. Interactions between components ofdifferent ecosystem functions often result in inter-functionaldependency, a control feedback mechanism. For instance,with regards to the interaction between hydrologic regulationand vegetation succession functions, the phenological charac-teristics (e.g. stomatal conductance and root architecture) ofpeatland vegetation regulated ET losses, water use efficiencyand consequently, hydrologic fluxes (Petrone et al. 2007b;Brown et al. 2010). As a feedback mechanism, vegetationcommunities will also shift in response to changes in hydro-logic conditions (Laiho 2006). The dependency of NPP anddecomposition on photosynthetic efficiency and litter qualityrespectively, creates a similar inter-functional link betweenvegetation succession and peatland carbon accumulationfunctions (Bauer et al. 2003).

A strong feedback interaction between biogeochemicaltransformation and vegetation succession functions is evidentin the interdependency between vegetation communities, wa-ter chemistry, microbial communities and nutrient cycling(e.g. mineralization and GHG fluxes). Similarly, the redox-sensitivity of biogeochemical processes leads to a tight cou-pling between hydrologic regulation and biogeochemicaltransformation functions (Niedermeier and Robinson 2007).The response sensitivity of these feedback mechanisms variesamong the levels of interaction, and can be explored as anindicator of the functional characteristics of reclaimedpeatland ecosystems. Microbially mediated biogeochemicalprocesses are very sensitive, respond rapidly to changes inconditions and are quantifiable. They also depend and feed-back on all the other ecosystem functional components suchas water table fluctuations and redox gradients, plant litterquality, and vegetation community diversity. Hence,microbially mediated biogeochemical processes will be a suit-able indicator of ecosystem functioning.

Such functional evaluation can be achieved by quantifyingmeasures of ecosystem processes that interact with biogeo-chemical transformation functions (Fig. 3), using the most

important variables highlighted in Table 1. For example, apracticable approach to undertake this functional evaluationwill involve monitoring the growing season’s hydrologic var-iability (water table fluctuations), a function of peat stratifica-tion. If the ecosystem is functional, microbial activities such asdecomposition and mineralization will be responsive to sea-sonal variability in hydrologic conditions due to redox gradi-ents (Fig. 3). As a result, the rate of nutrients transformationand supply rates will determine vegetation productivity andcommunity diversity in the short-term and long-term respec-tively. Vegetation productivity and community diversity willfeedback on litter quality, which interacts with microbial ac-tivity and hydrologic conditions to determine the degree oforganic matter sequestration, a targeted function in peatlandreclamation. The functional state and trajectory of the con-structed peatland can then be delineated by relating their func-tional characteristics (e.g. microbial carbon utilization profile)to those of different possible natural analogues (e.g. Fig. 1b;saline fen and rich fen).

Conclusion and Recommendation for Future FenReclamation Projects

Based on the limitations associated with the contemporarybio-indicator “tick box” approach of wetland evaluation, wepresent the concept of a functional-based approach that will bemore appropriate for the evaluation of constructed peatlandsin the Alberta oil sands region. The appropriateness of thisconcept is grounded on the potentials to define the functionalcharacteristics that might evolve in an ecosystem where therange of variability in biotic and abiotic conditions can resultto multiple trajectories and endpoints. Hence, this conceptaddresses the need to develop an integrated functional-basedapproach for the management of novel ecosystems that couldevolve in constructed peatlands.

Adopting this concept in fen reclamation projects is feasi-ble since it is based on the integration of quantifiable ecosys-tem processes that have been extensively studied in naturaland restored peatlands (Table 1). But since it can be arguedthat some of these measurements are expensive, highly labourand time-intensive, or require advanced scientific expertise,we have highlighted the most important variable that can beused to achieve meaningful results, especially within the fron-tiers of a small research group with limited funds. However,considering that this concept of fen reclamation is still at thepilot stage, it is premature to determine if the functional eval-uation of constructed peatland can be significantly simplifiedto a less cost and labour-intensive venture, considering thetargeted functions that need to be assessed in this peatlands.Our approach presents the first attempt to develop a cost-efficient functional based approach to evaluate constructed

Wetlands

oil sand peatlands, and opens a horizon for future research onthe subject matter.

Considering that energy industries are obliged to ensurethat what they reclaim is functioning as natural analogues,we trust a functional approach will ensure this, whereas theindicator species approach might lead to wrong conclusionsabout ecosystem processes (e.g. GHG emissions) due to al-tered abiotic conditions. We also believe that the industry andenvironmental regulators in this region appreciate the need todevelop a process-based evaluation approach, as they are al-ready investing in pilot fen projects were this concept will betested. Although these pilot studies are cost-intensive, the costassociated with these cannot bematched with the environmen-tal cost of losing peatland ecosystem services in the first place.Once informed insight about the functional characteristics ofthe constructed peatlands have been established from thesepilot studies, we will be more confident in selecting the keyvariables and processes that are most relevant in the context ofcost-efficient, future large scale peatland reclamation projectsin the Alberta oil sands region.

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