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Soil and vegetation properties on reclaimed oil sands in Alberta, Canada: a synthetic review Wu, ShuYao Apr 30, 2015

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	Soil	and	vegetation	properties	on	reclaimed	oil	sands	in	Alberta,	Canada:	a	synthetic	review																		 			ShuYao	Wu		The	Faculty	of	Forestry	The	University	of	British	Columbia	(Vancouver)		April	2015				 2	Executive	Summary		 The	 oil	 sands	 resource	 in	 Alberta	 represents	 vast	 economic	 opportunities	but	also	dramatic	environmental	 threat.	Many	 researches	have	been	conducted	on	the	properties	of	reclaimed	oil	sands	soils.	This	paper	intends	to	provide	a	synthetic	review	of	 some	 conducted	 researches	on	 the	 soil	 physical,	 chemical	 and	biological	properties	and	vegetation	community	development	in	Alberta.	This	paper	chooses	a	total	of	20	researches	(from	2003	to	2014)	that	restricted	their	study	sites	in	the	oil	sands	 extraction	 regions	 in	 Alberta.	 Five	 of	 the	 researches	mainly	 focused	 on	 soil	physical	properties,	five	on	chemical	ones,	six	on	biological	ones	and	another	four	on	vegetation	 community	 responses.	 This	 paper	 found	 that	 reclaimed	 soils	 generally	have	different	properties	in	all	physical,	chemical	and	biological	aspects	compare	to	natural	 soils.	 Prominent	 physical	 and	 chemical	 differences	 exist	 in	 organic	matter	content,	 soil	 nitrogen	 content	 and	 nitrogen	mineralization	 rate.	 These	 differences	also	 lead	 to	 significantly	 different	 microbial	 community	 structures	 and	 organic	matter	 accumulation	 rate.	 In	 addition,	mitigating	 effects	 of	 time	on	 soil	 properties	and	 vegetation	 communities	 were	 observed	 in	 this	 review.	 In	 the	 end,	 this	 paper	addresses	 the	management	 implications	and	 future	 research	 suggestions	based	on	researches.			 			 3	Table	of	Contents	Executive	Summary	............................................................................................................................	2	Table	of	Contents	.................................................................................................................................	3	1.	Introduction	......................................................................................................................................	4		 1.1	Oil	Sands	Environment	....................................................................................................	4		 1.2	Oil	Sands	Extraction	..........................................................................................................	6		 1.3	Oil	Sands	Reclamaition	....................................................................................................	9		 1.4	Study	Objetives	and	Materials	...................................................................................	12	2.	Research	Findings	.......................................................................................................................	14		 2.1	Soil	Physical	Properties	................................................................................................	14		 2.2	Soil	Chemical	Properties	..............................................................................................	21		 2.3	Soil	Biological	Properties	.............................................................................................	28		 2.4	Vegetation	Communities	..............................................................................................	39	3.	Discussion	.......................................................................................................................................	43		 3.1	Reclamation	Treatment	Effects	.................................................................................	43		 3.2	Reclamation	and	Management	Implications	.......................................................	45		 3.3	Limitations	and	Future	Reseraches	........................................................................	46	References	...........................................................................................................................................	48			 			 4	1.	Introduction		 1.1	Oil	Sands	Environment		 Oil	 sands	 refer	 to	 the	bacteria-processed	products	 of	migrated	bitumen	mixed	with	sand	deposits	 (Anderson	2014).	The	province	of	Alberta	 in	Canada	possesses	1.6	trillion	barrels	of	this	type	of	bitumen,	which	is	the	second	largest	oil	reserve	in	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,	the	Athabasca	region	is	largest	in	size	(grater	than	48,000	km2)	and	contains	the	largest	volume	of	bitumen.	The	estimated	number	varies	from	170	billion	barrels	to	700	billion	barrels	(Fung	and	Macyk	2000;	Hrudey	et	al.	2010).	 			Figure	1.	The	locations	of	three	major	oil	sands	reserves	(the	Athabasca,	Cold	Lake	and	Peace	River)	in	Alberta,	Canada.	(Wikipedia	2006).					 5	The	three	oil	sand	regions	are	all	located	in	the	boreal	forest	zone,	which	is	one	of	the	largest	intact	ecosystems	in	the	world	(Canadian	Boreal	Initiative	2003).	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).	A	highly	diverse	 floral	and	 faunal	species	composition	and	structure	can	be	found	in	this	large	ecological	biome.	In	addition,	the	boreal	forest	provides	an	array	of	 ecosystem	 services	 include	 water	 filter	 and	 storage,	 flood	 mitigation,	 carbon	sequestration,	nutrient	cycling	and	food	and	shelter	provision	for	both	animals	and	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	contribute	billons	of	dollars	to	Alberta’s	economy	annually	(Leatherdale	2008).	For	example,	 the	 investment	 for	 oil	 sands	 industry	 reached	 $17.2	 billion	 in	 2010;	 the	royalties	from	oil	sands	companies	to	the	government	of	Alberta	reached	$3.7	billion	in	 the	 same	 year;	 approximately	 151,000	 Albertans	 are	 directly	 employed	 in	 this	industry	(Government	of	Alberta	2013).		 Due	 to	 the	high	 latitude,	 the	 climate	 in	Alberta’s	 oil	 sands	 regions	 is	 generally	harsh.	The	annual	growing	season	do	not	start	until	the	ground	surface	thaws	in	late	May	or	early	June	and	only	lasts	about	95	days	till	September	(Rowland	2008).	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	include	aspen	 (Populus	 tremuloides	 and	 Populus	balsamifera),	 spruce	 (Picea	glauca	and	Picea	mariana),	 jack	pine	(Pinus	banksiana),	 fir	(Abies	balsamea)	and	tamarack	(Larix	 lariana)	 (Rowe,	 1972).	 Other	 than	 forest,	 bog	 and	 fen	 peatlands	 and	freshwater	wetlands,	which	 cover	 an	 area	 of	 20%	 to	 60%	of	 the	 oil	 sands	mining	regions,	are	also	major	types	of	landscapes	of	the	boreal	ecosystem	in	Alberta	(Vitt	et	al.	2000).		 The	parent	materials	of	oil	sands	soils	originated	from	the	delta	deposits	of	an			 6	ancient	 tropical	 sea	 and	 were	 compressed	 by	 glaciers	 during	 glaciation	 period,	which	gives	the	soils	fine	texture	(Rowland	2008).	These	deposits	are	consolidated	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	Reclamation	Committee,	1998).	This	wide	range	of	soil	order	is	caused	by	different	amount	of	clay-impeded	water	and	different	amount	of	leach	clay	in	soils	(Rowland	2008).	 This	 assortment	 in	 the	 soil	 order	makes	 the	 soil	moisture	 gradient	 to	 vary	from	 xeric	 to	 subhydric	 and	 the	 oxidation	 condition	 to	 vary	 from	 aerobic	 to	anaerobic.	In	addition,	the	peat	and	peat-like	soil	usually	can	be	found	at	soil	surface	(Stolte	et	al.	2000).	 		Table	1.	Commonly	found	natural	soils	in	the	oil	sands	regions	in	Alberta.	 	Name	 General	Descriptions	Orthic	Brunisols	Poorly	developed	mineral-organic	horizon.	No	Bt	or	Bp	horizon	 	High	degree	of	base	saturation	Parent	materials	usually	have	high	base	status	 	Commonly	found	under	forest	and	shrub	vegetation	Orthic	 Gray	Luvisols	Well-developed	 Ae	 and	 Bt	 horizion	 plus	 an	 organic	 surface	horizon	usually	 	Faint	mottling	might	be	found	near	or	within	Bt	horizon	 	Parent	materials	are	commonly	base	saturated	and	calcareous	 	Solum	is	usually	acid	 	Mesic	Fibrosol	 Deep,	relatively	undecomposed	fabric	material	 	Parent	material	is	organic	matter	and	clay-rich	glacial	till	 	High	percentage	of	organic	matter	(>30%)	 	Occur	in	bogs	and	fens	 	Gleysols	 Lack	of	well-developed	mineral-organic	surface	horizon,	such	as	Ah	or	Ap	 	Gleyed	B	or	C	horizon	Usually	occur	in	poorly	drained	areas	Sources:	The	Canadian	System	of	Soil	Classification	1998;	Rowland	2008.	 	1.2	Oil	Sands	Extraction	The	history	of	people	using	the	bitumen	deposition	is	quite	 long.	In	the	past,	 it	was	 traditionally	 used	 by	 First	 Nations	 to	 patch	 canoes	 (Hrudey	 et	 al.	 2010).	 The			 7	modern	 commercial	 oil	 sands	 industry	 in	 Alberta	 started	 slowly	 but	 expanded	rapidly	(Chastka	2004).	Nowadays,	there	are	dozens	of	oil	sands	companies	working	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	(Rowland	2008).	Open-pit	mining	and	 in	situ	extraction	are	the	two	main	oil	sands	extraction	methods	these	companies	are	using.	The	open-pit	extraction	method	can	only	be	applied	in	area	where	the	oil	sands	ore	is	close	to	surface	(Figure	2)	(Anderson	2014).	The	first	step	of	surface	mining	is	the	 removal	of	 all	 vegetation,	 soils	 and	non-ore	horizons	above	 the	deposit.	These	materials	are	usually	referred	as	“overburden”	and	have	depths	range	from	1	m	to	over	70	m	(Hrudey	et	al.	2010).	These	materials	are	usually	stockpiled	somewhere	close	 by,	 sometimes	 for	many	 years,	 before	 they	were	 used	 in	 future	 reclamation	(Mackenzie	2011).	 			Figure	1.	Open-pit	oil	sands	mining	in	Alberta	(National	Geographic	2011).		 However,	 for	 approximately	 80%	 of	 Alberta’s	 oil	 sands	 areas,	 the	 bitumen			 8	deposits	 are	 too	 deep	 for	 the	 open-pit	 mining	 method	 and	 the	 in	 situ	 extraction	method	need	to	be	applied	(RAMP	2015).	Currently,	the	most	commonly	used	in	situ	method	is	the	Steam	Assisted	Gravity	Drainage	(SAGD)	(Figure	3).	This	method	uses	two	 drilled	 horizontal	 wells,	 one	 above	 the	 bitumen	 deposit	 and	 one	 below.	 The	above	well	pumps	heated	steam	in	order	to	melt	and	press	bitumen	in	to	the	lower	well,	 from	which	the	bitumen	is	transported	up	to	the	surface.	Water	 is	 injected	to	replace	the	extracted	bitumen	for	stabilization	purpose	(RAMP	2015).	 	Once	the	oil	sands	deposits	are	extracted,	either	from	open-pit	or	in	situ	method,	they	 are	 transported	 to	 a	 facility	 that	 separates	 the	 bitumen	 and	 the	 sand	 before	they	were	upgraded	into	petroleum	(Rowland	2008).	The	Clark	hot-water	extraction	method,	which	uses	hot	water	with	added	sodium	hydroxide	(NaOH),	is	used	in	this	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	(Visser	1985).	The	ionic	content,	such	as	sodium,	sulfate	and	chloride	ions	are	also	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	compare	to	smaller	ones.	The	fine	particles	can	take	very	long	time,	even	hundreds	of	 years,	 to	 settle	 because	 of	 the	high	 ionic	 content	 (Renault	et	 al.	 1998).	 Gypsum	(CaSO4)	 is	 added	 sometimes	 as	 a	 consolidation	 agent	 to	 accelerate	 the	 settlement	process	of	the	fine	particles	(Li	and	Fung	1998).	 				 9		Figure	2.	Schematic	of	 the	Steam	Assisted	Gravity	Drainage	(SAGD)	 in	situ	bitumen	extraction	method	(the	Pembina	Institute	2005).	 		 There	 are	 three	 main	 types	 of	 waste	 materials	 generated	 from	 the	 bitumen	extraction	and	production	process,	which	are	overburden	material,	tailing	sand	and	fine	tailings	(Fung	and	Macyk	2000).	Overburden	refers	to	the	materials	that	overlay	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	remaining	waste	products	after	bitumen	extraction.	Tailing	sands	are	made	of	96	to	99	percent	sandy	silica	and	the	residual	bitumen.	Nevertheless,	 fine	tailings	mainly	consist	of	clay,	silts	and	residual	bitumen	(Fung	and	Macyk	2000).	 	1.3	Oil	Sands	Reclamation	It	is	mandatory	for	the	oil	sand	industry	to	have	the	disturbed	lands	reclaimed,	re-vegetated	and	certified	by	the	Government	of	Alberta.	However,	the	government	does	not	require	an	exact	identical	condition	but	only	“an	equivalent	land	capability”,	which	is	defined	by	the	Land	Capability	Classification	System	(LCCS)	as	“the	ability	of			 10	the	 land	 to	 support	 various	 land	uses	after	 conservation	 similar	 to	 the	ability	 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.	According	to	the	LCCS	field	manual,	 there	are	three	key	factors	need	to	 be	 addressed	 in	 order	 to	 achieve	 high	 land	 capability,	 which	 are	 minimal	 salt	impacts	(<4.0	dS/m	salinity	EC,	<8.0	Sodicity	SAR	and	<7.5	pH),	sustained	nutrient	cycling	and	sufficient	available	water-holding	capacity	 (CEMA	2006).	Furthermore,	vegetation	community	must	also	be	developed	in	the	sites	in	order	to	be	certifiable	as	successful	reclamation.	Some	indicators	for	successful	vegetation	reestablishment	include	plant	community	composition,	net	primary	production	of	the	ecosystem	and	soil	salinity.	 	The	 first	 step	 of	 reclamation	 is	 the	 replacement	 of	 the	 removed	materials	 or	reconstructing	 the	 soil.	 As	 guided	 by	 the	 above	 legal	 requirements,	 an	 ideal	soil-forming	material	 should	 have	 1)	 the	 ability	 to	 supply	 water	 and	 nutrients	 to	plants;	2)	the	adequate	stability	to	resist	erosion	but	also	enable	root	development	and;	3)	the	ability	to	buffer	environmental	changes	(Rowland	2008).	Various	kinds	of	mining	residuals	are	commonly	mixed	and	used	as	reclamation	materials,	such	as	peat-mineral	mix,	tailing	sands,	topsoil,	subsoil,	overburden,	lean	oil	sand	and	mine	by-products	(Table	2)	(Rowland	2008;	Hrudey	et	al	2010;	Mackenzie	2011).	 	Although	there	 is	no	universal	or	mandatory	prescription	of	how	the	company	should	reconstruct	a	soil,	 five	out	of	 the	seven	popular	prescriptions	 include	using	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	 in	Alberta,	 but	 also	because	peat	may	 improve	organic	 carbon	 content,	 soil	nutrient	 and	 water	 retention	 capacity	 (Rowland	 2008).	 As	 a	 pratical	 example,	Syncrude	Canada	Ltd.	spreads	approximately	15	cm	of	peat	with	20	cm	of	mineral	soil	as	top	 layer	for	plant	growth.	Beneath	this	 layer,	an	up	to	80	cm	deep	capping	layer	 that	 contains	 a	mixture	 of	 lean	 oil	 sands	 and	 overburden	 is	 used	 to	 prevent	water	and	plant	penetrating	to	underneath	toxic	materials	(Figure	4).	 			 11		Table	 2.	 Descriptions	 of	 some	 common	 materials	 used	 for	 soil	 reconstruction	 in	Alberta’s	 oil	 sands	 regions	 (Mossop,	 1980;	 Danielson	 et	 al.	 1983;	 Hardy	 BBT	 Ltd.	1990;	Rung	and	Macyk	2000;	Rowland	2008).	Name	 Origin	and	description	Principle	mineral	component	Physio-chemcial	properties	Peat-mineral	 Stripped	and	mixed	from	boreal	bogs	 	 Clay	loam	or	clay	 	 2	–	17%	organic	C;	Near-neutral	pH;	P:M	ratio	varies	3:2	to	3:4	by	volume	Tailing	sands	 Marine	sands	with	some	shale	beds	from	Cretaceous-era	 	 95%	sand	(quartz),	4%	silt	(feldspar	and	mica)	and	1%	clay	(kaolinite,	illite	and	montmorillonite)	 	Hydrophobic	after	air-drying	Nil	plant	nutrients	Erosion-prone	High	erosion	potential	Low	available	water	holding	capacity,	cation	exchange	capacity,	microbial	activity	and	organic	C	Subsoil	 B	and	C	horizon	of	boreal	forest	soil	 Silt-clay	and	clay	(kaolinite,	illite	and	montmorillonite)	 pH	5.0	–	8.0	Non-saline	<2%	organic	C		Overburden	 Sedimentary	deposits	from	Cretaceous-era	drifted	by	glacial	from	Pleistocene	Epoch	Silt-clay	and	clay	(kaolinite,	illite	and	montmorillonite)	 pH	8.0+	Non-saline	Nil	or	low	organic	C	Low	available	water	holding	capacity,	microbial	activity,	nutrient	status	 		Lean	oil	sand	 Cretaceous-era	marine	sediments	with	migrated	bitumen	Sands	with	some	shales,	silts	and	clays	 <6%	bitumen	by	weight	pH	5.5	–	6.0				 12		Figure	3.	Schematic	representation	of	oil	sands	reclamation	prescriptions	from	three	oil	 sands	 companies	 in	 Alberta,	 Canada	 (Oil	 Sands	 Vegetation	 Reclamation	Committee	1998;	AMEC	and	Paragon	2005;	Rowland	2008).	 		 In	terms	of	vegetation	restoration,	Hordeum	vulgare	(barley)	 is	usually	planted	as	a	cover	crop	initially	to	protect	soil	and	control	erosion.	Additionally,	barley	can	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	(Rowland	2008).	In	the	late	1980’s,	companies	start	to	adapt	natural	re-colonization	instead	of	direct	 seeding.	However,	on	 some	sites,	particularly	 for	 those	 reclaimed	for	 forestry	purposes,	 tree	planting,	 such	 as	 jack	pine,	 balsam	poplar,	white	 birch,	white	 spruce	 and	 aspen,	 is	 still	 used	 (Rowland	 2008;	Alberta	 Environment	 2009).	Shrub	species,	 such	as	 rose,	 low-bush	cranberry,	dogwood,	 raspberry,	 green	alder,	Canada	 buffalo-berry,	 Saskatoon,	 blueberry,	 bog	 cranberry	 and	 bearberry,	 are	replanted	 too	 (Alberta	 Environment	 2009).	 Mixed	 nitrogen,	 phosphorous	 and	potassium	fertilizer	are	used	almost	in	all	sites	in	the	first	one	to	five	years	in	order	to	accelerate	the	vegetation	establishment	(Hrudey	et	al.	2010).	1.4	Study	Objectives	and	Materials	Up	to	 the	year	of	2012,	 there	were	715	km2	have	been	exploited	 for	oil	 sands,	however,	 only	 1	 km2	 of	 which	 has	 been	 successfully	 reclaimed	 and	 certified	(Anderson	 2014).	 Despite	 the	 significant	 economic	 profits	 oil	 sands	 brought	 to			 13	Alberta,	the	environmental	costs	of	exploiting	oil	sands	on	greenhouse	gas	emissions,	air	 and	 water	 quality,	 are	 also	 becoming	 more	 and	 more	 tremendous.	 In	 2010,	approximately	48	million	 tones	of	greenhouse	gas	emissions	 in	Alberta	are	caused	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	 reclaimed	sites	have	already	 turned	 into	over	30-year-old.	More	and	more	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	researches	on	physical,	chemical	and	biological	properties	of	reclaimed	oil	sand	soils	and	 vegetation	 community	 development	 status	 in	 order	 to	 provide	 a	 synthetic	review	 to	 other	 researchers,	 compare	 reclaimed	 soils	 with	 natural	 soils,	 propose	reclamation	and	management	suggestions	and	identify	some	potential	 future	study	focuses.	 	A	 total	 of	 20	 researches	 that	 have	 their	 study	 sites	 in	 the	 oil	 sands	 extraction	regions	in	Alberta	were	chosen.	These	researches	focused	mainly	either	on	physical	(5),	chemical	 (5),	biological	 (6)	soil	properties	(some	studied	mixed	properties)	or	vegetation	 growth	 (4)	 on	 reclaimed	 oil	 sands	 sites.	 Data	 were	 utilized	 from	 12	published	peer-reviewed	journal	articles	and	8	master	thesis	work	range	from	2003	to	2014.	Each	 study	 is	briefly	 retold	by	 its	 study	objectives,	methods,	 key	 findings	and	important	discussion	points.	 			 			 14	2.	Research	Findings	2.1	Soil	Physical	Properties	Table	 1.	 Summary	 of	 discovered	 physical	 properties	 and	 their	 descriptions	 of	reclaimed	oil	sands	soils	in	Alberta,	Canada.	 	Studies	(Year)	Properties	 Findings	Yarmuch	(2003)	Texture	-	Topsoils	range	from	loam	to	clay	loam	to	silty	clay	loam	(silt	loam	to	loam	in	natural	soils)	-	Subsoils	range	from	sandy	clay	loam	to	clay	loam	to	silty	clay	loam	(clay	loam	to	clay	to	heavy	clay)	 	-	Much	more	organic	matter	in	topsoil	layer	compare	to	that	of	natural	soils	-	Subsoils	are	more	similar	but	contain	less	clay	Bulk	density	-	Lower	in	reclaimed	topsoil	compare	to	natural	soils	 	-	Higher	in	young	topsoil	and	lower	subsoil	than	in	old	reclaimed	soils	-	No	significant	differences	between	young	and	old	reclaimed	upper	subsoils	Field	saturated	hydraulic	conductivity	 -	No	significant	difference	neither	between	natural	and	reclaimed	soils	nor	young	and	older	reclaimed	soils	Porosity	-	Higher	macro-,	meso-	and	micro-porosity	in	reclaimed	topsoil	than	that	of	natural	soils	 	-	More	macropores	and	less	micropores	in	reclaimed	subsoils	than	that	of	natural	soils	-	 	 More	micropores	in	young	reclaimed	soils	than	in	old	ones	Leatherdale	(2008)	Soil	moisture	 -	Slope	positions	did	not	significantly	affect	soil	moisture	regime	-	Soils	that	have	higher	amount	of	organic	matter	hold	higher	plant	available	water	Soil	nutrient	(chemical	property)	-	A	high	degree	of	variability	of	soil	nutrients	across	slope	positions	-	Season	appeared	to	be	more	influencing	than	site	conditions	on	nutrient	availability	 	Trites	and	Bayley	(2009)	Organic	matter	accumulation	and	decomposition	in	wetlands	-	Biomass	accumulation	negatively	relates	to	pollutants	but	positively	relates	to	water	depth	but	still	lower	than	natural	wetlands	due	to	high	salinity	-	Similar	litter	decay	rates	between	natural	and	reclaimed	wetlands			 15	Hunter	(2011)	 Water	repellency	-	High	variability	of	water	repellency	exists	within	both	reclaimed	and	natural	sites	-	Surface	reclaimed	soils	appeared	to	have	higher	average	water	repellency	than	subsurface	soils	-	No	significant	differences	found	between	the	RI	values	of	surface	reclaimed	and	natural	soils	Anderson	(2014)	Organic	matter	content	 -	Higher	organic	matter	in	reclaimed	soils	than	natural	soils	mainly	due	to	peat	Sources	of	organic	matter	accumulation	-	Dominant	tree	type	is	the	most	influencing	factor	of	SOM	accumulation	-	Root	and	macrofaunal	bioturbation	dominated	as	source	in	grassland	treatment	-	Dissolved	organic	matter	from	forest	floor	and	macrofunal	activity	dominated	in	deciduous	treatment	-	No	sign	of	accumulation	in	natural	and	reclaimed	spruce	sites	Organic	accumulation	rate	-	Highest	in	deciduous	sites,	moderate	in	grassland	sites	and	slowest	in	spruce	sites	-	The	order	corresponds	with	the	diversity	of	organic	matter	input	and	the	levels	of	macrofaunal	bioturbation		Yarmuch	(2003)	–	Measurement	of	soil	physical	parameters	to	evaluate	soil	structure	quality	in	reclaimed	oil	sands	soils	Alberta,	Canada:		 Yarmuch	(2003)	studied	a	range	of	common	soil	physical	properties	in	order	to	access	 the	 structure	quality	of	 reclaimed	oil	 sands	 soils	 in	 the	Athabasca	oil	 sands	region.	 The	 author	 also	 compared	 the	 soil	 physical	 properties	 among	 naturally	disturbed	sites	and	reclaimed	sites	with	different	ages.	Nine	naturally	disturbed	sites	and	27	sites	in	disturbed	areas	were	selected.	Soil	pits	were	dug	and	samples	were	collected	within	three	soil	layers:	topsoil	(0-20	cm),	upper	subsoil	and	lower	sub	soil	in	reclaimed	soils	and	LFH,	A,	B	and	BC	or	C	horizons	in	undisturbed	soils.	Physical	properties	that	were	analyzed	included	particle	size	analysis	(hydrometer	method),	soil	bulk	density,	field	saturated	hydraulic	conductivity	(Guelph	Permeameter),	pore	size	 distribution	 and	 available	 water	 holding	 capacity	 (the	 water	 column	method	and	pressure	plate	apparatus).	 	The	 texture	 of	 the	 upper	 subsoil	 and	 the	 lower	 subsoil	 of	peat-mineral-mix/overburden	reclaimed	soils	was	found	to	range	from	sandy	loam			 16	to	sandy	clay	loam	to	clay	loam.	The	comparison	of	soil	physical	properties	between	reclaimed	oil	sands	soils	and	naturally	disturbed	soils	showed	that	the	texture	of	the	topsoil	horizon	was	much	different	 than	the	naturally	disturbed	Ae	horizon	due	to	high	 organic	 matter	 from	 the	 peat	 amendments.	 However,	 the	 upper	 and	 lower	subsoils	of	reclaimed	soils	had	a	slightly	lower	proportion	of	clay	size	particles	than	the	naturally	disturbed	Bt	and	BC/C	horizons	do,	respectively.	 	The	mean	 bulk	 density	 of	 the	 reclaimed	 topsoils	 was	 significantly	 lower	 than	that	of	 the	naturally	disturbed	Ae	horizon.	But	 the	differences	were	not	significant	between	 the	 upper	 and	 lower	 subsoil	 horizons	 and	 the	 corresponding	 naturally	disturbed	 soil	 horizons.	 In	 addition,	 there	were	no	 significant	differences	between	the	 field	 saturated	 hydraulic	 conductivity	 of	 the	 topsoil,	 the	 upper	 and	 lower	subsoils	and	their	corresponding	natural	horizons	either	in	most	instances	(five	out	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	make	soil	aggregates	more	rigid.	 	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.	More	macropores	and	less	micropores	were	found	in	the	reclaimed	upper	and	lower	subsoils	compare	to	the	naturally	disturbed	corresponding	horizons.	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	 do	not	 possess	 limiting	 structures	compare	to	that	of	natural	soils.	 	Soil	 physical	 properties	 were	 also	 compared	 among	 reclaimed	 soils	 with	different	ages.	It	was	found	that	reclaimed	young	topsoil	and	lower	subsoil	horizons	had	higher	bulk	densities	 than	old	ones.	The	differences	of	bulk	densities	between	young	and	old	upper	subsoil	horizons	were	not	significant.	In	addition,	there	was	no	significant	 difference	 found	 in	 the	 field	 saturated	 hydraulic	 conductivity,	 total	porosity	and	amount	of	macro-,	meso-	and	micropores	between	the	old	and	young			 17	reclaimed	 soils	 either.	 However,	 there	 were	 significantly	 higher	 amount	 of	macropores	 and	 lower	 amount	 of	mesopores	 in	 the	 young	upper	 subsoil	 horizons	than	 in	 the	old	ones.	 Yarmuch	explained	 this	 observation	by	natural	 settlement	of	soil	material	over	time.	In	conclusion,	the	author	stated	that	there	is	little	change	in	soil	physical	properties	in	approximately	20	years	and	reclaimed	soil	structures	may	be	stable	or	change	very	slowly	(decades	to	centuries).	 		Leatherdale	(2008)	–	Soil	moisture	and	nutrient	regimes	of	reclaimed	upland	slopes	in	the	oil	sands	region	of	Alberta:	 	The	objective	of	Leatherdale’s	study	is	to	quantify	the	soil	moisture	and	nutrient	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	 soil	moisture	 and	nutrients	 at	 slope	 levels.	 Five	 study	 sites	were	 selected	 approximately	 50-80	 km	 north	 of	 Fort	 McMurrary	 in	 northeastern	Alberta.	Meteorological	parameters	(weather	station),	soil	moisture	(Diviner	2000®	access	tubes),	topsoil,	upper	subsoil	and	lower	subsoil	samples	were	collected	in	the	field.	In	laboratory,	bulk	density,	soil	water	characteristic	curves	(use	pressure	plate	apparatus),	 particle	 size	 distribution	 (use	 hydrometer	 method)	 and	 total	 organic	carbon	(use	dry	combustion	method)	were	determined.	The	 results	 showed	 that	 the	moisture	contents	were	not	 significantly	different	across	the	lower,	mid	and	upper	slope	positions	on	the	reclaimed	upland	soils.	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	(less	or	equal	than	25%).	Soils	that	have	higher	amount	of	organic	matter	hold	higher	plant	available	water.	In	addition,	the	infiltration	rates	were	found	to	be	higher	 in	 soils	 that	 have	 greater	 fraction	 of	 coarse	 textured	 material	 in	 their	peat-mineral	mix	layer.	The	moisture	regimes	of	upper	soil	profiles	in	most	sites	had	quick	responses	 to	precipitation	events,	except	on	sites	 that	 lack	of	vegetation	and	have	hydrophobic	properties.	Soils	with	less	finer	textured	materials	are	subject	to	percolation.	South-	and	west-	 facing	sites	 lost	or	maintained	soil	water	overwinter	while	north-facing	sites	gained	soil	moisture	overwinter.	This	might	be	because	of	a			 18	combination	 of	 less	 incoming	 solar	 radiation	 on	 north-facing	 slope	 and	 the	water-holding	effect	of	vegetation.	In	 terms	 of	 soil	 nutrient	 regimes,	 a	 high	 degree	 of	 variability	 in	 nutrient	availability	was	found	across	the	slope	positions.	The	author	explained	this	through	vegetation	patch	dynamics	and	different	spatial	distributions	of	vegetation	species.	Season	 appeared	 to	 be	 a	more	 influencing	 factor	 of	 nutrient	 availability	 than	 site	conditions.	 Similarity	 in	 seasonal	 nutrient	 availability	 was	 found	 between	 some	reclaimed	soils	and	naturally	disturbed	soils.		Trites	 and	 Bayley	 (2009)	 –	 Organic	 matter	 accumulation	 in	 western	 boreal	 saline	wetlands:	a	comparison	of	undisturbed	and	oil	sands	wetlands:	Since	 the	wetland	 is	also	a	dominant	pre-disturbance	 landscape	 type	 in	Albert	oil	 sands	 region,	 oil	 sands	 companies	 are	 required	 to	 reclaim	 some	 sites	 back	 to	wetlands	even	after	the	salinity	is	elevated.	Therefore,	Trites	and	Bayley	wanted	to	measure	and	compare	the	production	rates,	decomposition	rates	and	organic	matter	(OM)	accumulation	potential	in	reclaimed	wetlands	and	in	natural	wetlands	across	a	salinity	gradient	in	order	to	evaluate	the	potential	of	reclaimed	plants	to	accumulate	peat	 under	 future	 oil	 sands	 reclamation	 scenarios.	 Three	 reclaimed	 oil	 sands	wetlands	and	six	natural	wetlands	were	selected	near	Fort	McMurray,	Alberta.	Total	carbon,	 nitrogen	 and	 phosphorus	 of	 soils,	 aboveground	 wetland	 production,	decomposition	rate	(litter	bag	technique),	C:N:P	ratio	in	aboveground	litter	and	OM	accumulation	potential	were	measured	or	estimated	in	one	to	two	vegetation	zones	at	each	wetland.	 	It	was	found	the	mean	annual	total	biomass	production	in	this	study	was	about	502	 g	 m-2	 and	 the	 production	 rate	 negatively	 related	 to	 salinity.	 Negative	relationship	was	 found	 between	 pollutants,	 such	 as	 NH4+	or	 naphthenic	 acids,	and	biomass	while	positive	relationship	was	observed	between	water	depth	and	biomass,	which	 indicated	 the	 important	 role	 of	 the	 water	 availability	 played	 in	 successful	vegetation	 reclamation.	 High	 water	 level	 can	 also	 decrease	 the	 oxidation	 rate	 of	accumulated	peat.	In	addition,	Trites	and	Bayley	also	observed	different	decay	rates	for	 different	 litter	 types	 but	 same	 decay	 rates	 between	 oil	 sands	 and	 natural			 19	wetlands.	Only	weak	correlation	was	found	between	decay	rates	and	the	C:N	ratios	of	aboveground	plant	tissues	and	no	correlation	was	observed	between	salinity	and	litter	decomposition	rates.	 	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	reclaimed	and	natural	wetlands.	The	quotient	values	were	much	lower	than	average	boreal	bogs	(7.1)	but	similar	to	the	ones	from	poor	and	moderate-rich	wooded	fens	(3.6-4.0).	 Peatlands	 that	 were	 dominated	 by	 Schoenoplectus	 tabernaemontani	 and	Trigiochin	maritima	generated	the	highest	ratios,	which	implied	a	higher	potential	to	accumulate	 OM	 since	 these	 species	 had	 slower	 decomposition	 rates.	 The	 slower	biomass	 decomposition	 rates	 compensated	 the	 salinity-induced	 slow	 production	rates	and	gave	oil	sands	wetlands	relatively	acceptable	peat	accumulation	rates.	 In	the	 end,	 the	 authors	 concluded	 that	 reclaimed	 oil	 sands	 wetlands	 had	 peat	accumulation	 if	 the	condition	of	 sufficient	water	 level	and	 low	pollutants	was	met.	However,	in	general,	the	peat	accumulation	rate	would	still	be	at	a	slower	level	than	in	natural	wetlands	in	the	long	term.		Hunter	 (2011)	 –	 Investigation	 of	 water	 repellency	 and	 critical	 water	 content	 in	undisturbed	 and	 reclaimed	 soils	 from	 the	 Athabasca	 oil	 sands	 region	 of	 Alberta,	Canada:	Hunter	aims	to	quantify	the	degree	of	naturally	occurring	water	repellency	and	the	potential	of	 severe	water	 repellency	 in	 reclaimed	soils.	 In	order	 to	do	 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.	 Soil	water	 repellency	 index	(RI)	were	gathered	by	using	standard	and	mini	 infiltrometers.	Other	methods	such	as	 the	 water	 droplet	 penetration	 time	 test	 (WDPT)	 and	 the	 molarity	 of	 ethanol	droplet	test	(MED)	were	used	along	with	the	in	situ	repellency	index	to	estimate	soil	water	repellency.	The	critical	water	content	of	reclaimed	soils	was	also	determined	through	measuring	the	contact	angle	(CA)	and	WDPT.	 			 20	The	 results	 from	 both	 standard	 and	 mini	 inifltrometers	 suggested	 that	 high	variability	 of	water	 repellency	 exists	within	 both	 reclaimed	 and	 natural	 sites.	 The	mean	RI	values	from	the	mini	infiltrometers	(9.61)	were	higher	than	those	from	the	standard	 ones	 (3.46)	 but	 the	 differences	were	 not	 statistically	 significant	 in	most	sites.	 The	WDPT	 and	 MED	 tests	 also	 demonstrated	 similar	 trends	 of	 high	 spatial	variability	of	soil	water	repellency.	The	surface	reclaimed	soils	appeared	to	have	a	higher	average	RI	 than	 the	 subsurface	 soils.	Nevertheless,	 there	was	no	significant	differences	found	between	the	RI	values	of	the	surface	reclaimed	and	natural	soils.	 	The	 results	 of	 the	 critical	 water	 content	 showed	 that	 reclaimed	mineral	 soils	were	generally	wettable	above	gravimetric	water	contents	of	5	 to	10%.	Subcritical	water	repellency	occurred	in	the	materials	that	were	affected	by	the	coarse	textured	tarball.	 In	 addition,	 there	was	 a	 clear	 positive	 relationship	 between	 the	 degree	 of	water	repellency	and	the	decomposition	levels	of	peat	materials.	Furthermore,	peat	and	 LFH	 layers	 had	 no	 relationship	 between	water	 content	 and	water	 repellency.	Finally,	Hunter	 concluded	 that	water	 repellency	might	not	 be	 a	major	 issue	 in	 the	Athabasca	oil	sands	region.		Anderson	(2014)	–	Organic	matter	accumulation	 in	reclaimed	soils	beneath	different	vegetation	types	in	the	Athabasca	oil	sands:		 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	 organic	matter	 and	 the	 organic	matter	 accumulation	 rates.	 The	 author	selected	 five	 aspens	 sites,	 five	 spruce	 sites	 and	 five	 grassland	 sites	 that	 ranges	between	20	to	36	years	old	and	are	located	in	the	upland	Athabasca	oil	sands	region.	Five	 nearby	 natural	 sites	 with	 similar	 moisture	 and	 nutrient	 regimes	 were	 also	selected.	 The	 author	 tested	 and	 analyzed	 measurements	 include	 the	 bioturbation	levels,	the	root	abundances	and	the	organic	matter	contents.		 It	was	found	that	the	reclaimed	soils	had	considerably	higher	amount	of	organic	matter	 than	 the	 natural	 soils	 probably	 due	 to	 the	 abundant	 peat	 used	 during	reclamation.	Reclaimed	peat-mineral	mix	soils	were	found	to	have	higher	capacity	to	stabilize	dissolved	organic	matters,	which	led	to	an	increased	residency	time	of	SOM			 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	reclaimed	soils.	 		 The	 sources	 of	 SOM	 accumulation	 depend	 on	 the	 planted	 vegetation.	 For	example,	 root	 and	macrofaunal	 bioturbation	were	 the	 dominating	 SOM	 sources	 in	grassland,	 while	 in	 deciduous	 treatment	 sites,	 dissolved	 organic	 matter	 from	 the	forest	 floor	 and	macrofaunal	 activity	 dominated	 as	 sources.	 There	was	 no	 sign	 of	active	SOM	accumulation	in	natural	sites	and	reclaimed	sites	that	were	planted	with	spruces.	A	strong	 inverse	relationship	between	soil	depth	and	SOM	concentrations	was	found	in	deciduous	sites,	which	was	an	 indicator	of	downward	moving	humus	compounds.	 It	 was	 concluded	 that	 dominant	 tree	 type	 was	 the	 most	 influencing	factor	of	SOM	accumulation.	 		 In	 terms	 of	 the	 forest	 floor	 development,	 grassland	 and	 deciduous	 sites	 had	significantly	 thicker	 forest	 floor	and	more	macrofaunal	activities	 than	spruce	sites.	These	probably	attributed	to	the	higher	quantities	and	better	quality	of	the	organic	matter	input	in	these	two	types	of	sites.	Last	but	not	least,	it	was	found	that	the	SOM	accumulation	 rate	was	highest	 in	deciduous	 sites,	moderate	 in	 grassland	 sites	 and	lowest	in	spruce	sites,	which	correspond	with	the	diversity	of	organic	matter	input	and	the	levels	of	macrofaunal	bioturbation.		 2.2	Soil	Chemical	Properties	Table	 2.	 Summary	 of	 discovered	 chemical	 properties	 and	 their	 descriptions	 of	reclaimed	oil	sands	soils	in	Alberta,	Canada.	Studies	(Year)	Properties	 Findings	Rowland	(2008)	Soil	pH	level	 -	Almost	all	sites,	except	for	one	had	higher	pH	than	natural	ecotypes	because	of	the	nature	of	reclamation	materials	In	situ	bio-available	nutrients	-	High	amount	of	NO3—N	and	low	C:	N	ratio	was	found	in	all	reclaimed	sites	despite	ages	and	fertilizer	application	-	Micronutrient	Na	was	low	on	all	reclaimed	sites			 22	because	of	dispersal	of	Na	from	clays	by	the	addition	of	gypsum	and	leaching	Litter	input	and	organic	layer	development	-	Litter	decomposition	rate	and	the	FH	layer	development	rate	were	slower	on	reclaimed	sites	compare	those	of	natural	sites	-	Approximately	at	least	25	years	was	required	to	have	reclaimed	plant	communities	similar	to	natural	ones	Moisture	content	(physical	property)	-	The	presence	of	tailing	sands	decrease	moisture	content.	-	The	presence/absence	of	plant	root	activity	did	not	affect	moisture	content	Plant	community	development	(vegetation	response)	-	Treatments	that	use	peat-mineral	mix	placed	above	overburden	and	tailing	sands	and	initially	fertilized	with	P,	K	and	elements	such	as	Mn	generated	ecotypes	more	similar	to	the	natural	ones	Turcotte	et	al.	(2009)	 Soil	organic	matter	quality	-	Lower	AUR	residue,	alkyl/O-alky	ratio	and	organic	matter	in	the	organic	matter	heavy	sand	fraction	were	found	in	old	reclaimed	sites	-	Carbon	concentration	in	the	low-density	fraction	can	be	used	as	indicator	of	SOM	quality	in	reclaimed	sites	Hemsley	(2012)	 Nitrogen	availability	and	ecological	responses	-	Higher	atmospheric	nitrogen	deposition	(mainly	as	NH4+)	in	reclaimed	sites	-	Amount	of	wet	N	deposition	negatively	relate	to	canopy	cover	-	Pine	stands	showed	more	close	N	cycle,	higher	total	inorganic	N	and	higher	sensitivity	to	N	deposition	MacKenzie	and	Quideau	(2012)	Nitrogen	mineralization	-	Nitrogen	mineralization	rate	in	peat	mineral	soil	from	laboratory	incubation	was	much	higher	than	natural	forest	soils	-	The	rate	in	forest	floor	mineral	soil	was	at	a	similar	level	as	in	natural	LFH	layers	-	The	rates	obtained	laboratory	was	much	higher	than	field	measurement	and	modeled	decomposition	rates	Microbial	community	structure	-	High	metabolic	quotient	(basal	respiration/total	microbial	biomass)	but	fewer	amounts	of	fungi	and	fungi/bacteria	in	peat	mineral	soil	-	Forest	floor	mineral	mix	showed	more	similar	microbial	community	structure	as	in	natural	soils	-	The	effect	of	NPK	fertilization	on	microbial			 23	structure	was	not	prominent	without	vegetation	presence	Plant	nutrient	availability	-	Much	more	higher	nitrogen	(mainly	in	nitrate	form)	content	was	found	in	peat	mineral	and	mix	soils	than	in	forest	floor	mineral	soils	-	A	strong	association	between	respiration	and	nutrient	availability	 	Quideau	et	al.	(2013)	Nutrient	Availability	 -	Higher	N	and	S	concentrations	in	reclaimed	sites	but	still	some	similarities	with	natural	sites	 	Organic	matter	composition	 -	Higher	amount	of	organic	matter	in	reclaimed	soils.	-	Very	different	organic	matter	chemical	composition	between	natural	and	reclaimed	sites	Microbial	communities	(biological	property)	-	Some	unique	microbes	found	in	reclaimed	sites	compare	to	natural	sites	but	also	with	some	overlaps	with	natural	sites		Rowland	 (2008)	 –	 Recreating	 a	 functioning	 forest	 soil	 in	 reclaimed	 oil	 sands	 in	northern	Alberta:		 In	Rowland’s	study,	a	range	of	variables	were	measured	within	the	Wood	Buffalo	region	 of	 northern	 Alberta	 in	 order	 to	 determine	 whether	 reclaimed	 and	 natural	systems	differ	in	soil	properties	and	how	the	reclaimed	systems	change	over	time.	A	total	of	47	natural	and	reclaimed	soil	plots	were	established.	Variables	that	collected	include	moisture	content,	pH,	C:	N	ratio,	litter	mass	loss	rate,	litter	input	and	organic	layer	 development	 status,	 in	 situ	 bio-available	 nutrients,	 nitrate	 and	 ammonium	production	and	plant	community	development.	Rowland	studied	not	only	chemical	but	also	many	physical	and	biological	properties.	 		 The	 results	 of	 moisture	 showed	 that	 the	 presence	 of	 tailing	 sands	 at	 depth	generally	reduce	moisture	content,	however,	a	peat-mineral	mix	cap	usually	helped	storing	moisture	unless	 tailing	sands	 is	directly	below	 it.	The	presence/absence	of	plant	root	activity	did	not	affect	moisture	content	according	to	the	experiment.	This	might	be	attributed	to	the	microbial	proliferation	in	sites	without	plant	roots.	For	pH	level,	almost	all	sites,	except	for	one,	had	higher	pH	than	natural	ecotypes	because	of	the	 clay-rich,	 calcium-absorbing	 mineral	 soil	 in	 the	 peat-mineral	 mix	 and	 the	windblown	deposits	from	nearby	exposed	tailings.	 			 24	In	terms	of	nutrient	status,	abundant	NO3—N	were	found	in	all	sites	despite	ages	and	fertilizer	application.	Micronutrient	Na	was	low	on	all	reclaimed	sites	because	of	dispersal	of	Na	from	clays	by	the	addition	of	gypsum	and	leaching.	Furthermore,	 it	was	found	that	 litter	decomposition	rate	and	the	FH	layer	development	rates	were	slower	on	reclaimed	sites	compare	those	of	natural	sites.	Approximately	at	least	25	years	was	required	to	have	reclaimed	plant	communities	similar	to	natural	ones.	In	 the	 end,	 the	 author	 concluded	 that	 the	 treatment	 types,	 which	 place	peat-mineral	 mix	 above	 overburden	 and	 tailing	 sands	 both	 generated	 ecotypes	similar	to	the	target	natural	ones.	But	these	sites	with	a	peat-mineral	mix	cap	need	to	 be	 initially	 fertilized	 with	 P,	 K	 and	 elements	 such	 as	 Mn	 for	 successful	 early	ecosystem	development.	Rowland	challenged	the	use	of	N	fertilizer,	clean	peat	and	glacial	 tills	 as	 reclamation	 materials	 since	 abundant	 nitrogen	 was	 also	 found	 in	unfertilized	soils	and	the	peat	and	till	resources	are	non-renewable.	He	also	argued	large-scale	reclamation	should	focus	more	on	ecological	landscape	restoration	than	achieving	exact	original	state.	 		Turcotte	 et	 al.	 (2009)	 –	 Organic	 matter	 quality	 in	 reclaimed	 boreal	 forest	 soils	following	oil	sands	mining:	 		 Turcotte	et	al.	assessed	the	reclaimed	soil	quality	through	a	range	of	soil	organic	matter	(SOM)	parameters	and	compared	these	parameters	with	natural	soils	in	the	Fort	McMurray	oil	sands	region.	They	tried	to	answer	whether	the	SOM	parameters	evolved	with	time	towards	those	of	natural	soils	and	which	reclamation	prescription	performed	the	best.	A	total	of	45	study	sites	(18	natural	sites	and	27	reclaimed	sites)	were	 selected	 within	 an	 86	 km	 radius	 from	 the	 town	 of	 Fort	 McMurray,	 Alberta.	Surface	soils	(0	to	10cm),	excluding	the	raw	litter	layer,	were	collected	in	each	site.	The	samples	were	further	divided	into	clay	and	silt	OM,	low	density	OM	and	heavy	sand	OM	fractions.	In	laboratory,	the	acid-unhydrolyzable	residue	(AUR)	(proximate	analysis),	total	C	(dry	combustion),	value	of	alkyl	C,	O-alkyl	C,	aromatic	C,	phenolic	C	and	carbonyl	C	(spectrometer)	and	carbon	isotopic	composition	(δ13C)	(isotope	ratio	mass	spectrometer)	were	determined.	 		 The	results	demonstrated	that	the	reclaimed	soils	and	the	natural	soils	had	both			 25	similarities	 and	differences	 in	 SOM	parameters.	The	 amount	of	 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	 organic	matter	 fractions	were	 found	 in	 reclaimed	 soils.	 Turcotte	et	 al.	explained	these	by	the	usage	of	peat	amendments	during	reclamation.	For	the	heavy	sand	 and	 finer	 mineral	 particle	 (SiC)	 pools,	 it	 was	 not	 surprising	 to	 find	 the	reclaimed	sites	had	significantly	less	amount	of	humified	organic	matter.	Lastly,	the	carbon	concentrations	in	the	AUR	were	also	higher	in	reclaimed	soils	than	in	natural	soils,	 which	 suggested	 that	 the	 organic	mater	 in	 the	 reclaimed	 soils	 has	 not	 been	strongly	affected	by	microbial	degradation.	 	In	 terms	 of	 the	 SOM	 parameters	 between	 young	 and	 old	 reconstructed	 soils,	Turcotte	et	al.	 found	that	the	AUR	residue,	alkyl/O-alky	ratio	and	organic	matter	in	the	organic	matter	heavy	sand	 fraction	decreased	with	 time	since	reclamation	and	could	be	used	as	indicator	of	SOM	formation	processes	for	reclaimed	soils.	Another	good	indicator	for	general	SOM	quality	that	they	found	was	the	carbon	concentration	in	the	low-density	fraction	since	it	correlated	with	many	SOM	parameters.	 		Hemsley	 (2012)	 –	 Ecological	 response	 of	 atmospheric	 nitrogen	 deposition	 on	reconstructed	soils	in	the	Athabasca	oil	sands	region:		 In	Hemsley’s	study,	he	aimed	to	 firstly	determine	the	seasonal	amounts	of	wet	nitrogen	(N)	deposition,	soil	nitrogen	availability	and	their	potential	relationships	in	reconstructed	 soils	 and	 then	 assess	 the	 ecological	 responses	 and	 potential	implications	 of	 atmospheric	N	 depositions.	 A	 total	 of	 27	 sites	with	 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	simulator	probes),	soils,	foliage	and	root	samples.	 		 The	 atmospheric	 N	 deposition	 appeared	 to	 be	 <1	 kg	 N	 ha-1yr-1	 greater	 than	natural	sites	and	mainly	were	deposited	as	NH4+.	Canopy	cover	had	a	clear	negative	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-available	form	in	reconstructed	soils	in	this	study.	A	positive	relationship	between	N	deposition	and	N	availability	was	also	found.	 	When	comparing	aspen	and	pine	ecosystems,	a	greater	amount	of	total	inorganic	N	was	found	in	pine	sites	across	all	three	canopy	coverage.	This	was	explained	by	the	physiological	 differences	 between	 aspen	 and	 jack	 pine,	 such	 as	 different	 N	requirement	 and	 uptake	 rates.	 Further	 experiments	 showed	 that	 the	 pine	ecosystems	were	also	more	sensitive	to	the	additional	N	deposition.	A	more	open	N	cycle	was	identified	in	the	pine	stands	than	in	the	aspen	stands	due	to	the	excessive	soil	N	inputs.	In	the	end,	Hemsley	concluded	that	N	is	not	a	 limiting	nutrient	in	his	reclaimed	 sites	 and	 more	 N	 demanding	 species	 should	 be	 planted	 to	 avoid	 N	leaching.	 	 		 	 	Mackenzie	 and	 Quideau	 (2012)	 –	 Laboratory-based	 nitrogen	 mineralization	 and	biogeochemistry	of	two	soils	used	in	oil	sands	reclamation:	 		 The	 objectives	 of	 this	 study	 include	 1)	 determination	 and	 comparison	 of	nitrogen	mineralization	rate	constants	between	peat	mineral	mixed	soil	and	natural	forest	 floor	 mineral	 mixed	 soil,	 which	 are	 two	 types	 of	 oil	 sands	 reclamation	materials,	as	well	as	2)	determination	of	the	effect	of	NPK	fertilization	on	microbial	community	structure	and	nutrient	profiles.	Peat	and	forest	floor	samples	were	taken	from	 a	 sphagnum	 (Sphagnum	 angustifolium)	 dominated	 peatland	 and	 an	 aspen	(Populus	ttremuloides)	stand	in	the	Athabasca	oil	sand	region	to	create	peat	mineral	soil	and	 forest	 floor	mineral	 soil,	 respectively.	The	authors	mixed	 the	 two	 types	of	mixed	soils	 to	create	another	sample	 type	and	added	NPK	 fertilizer	 in	some	of	 the	three	soil	types.	Nitrogen	mineralization	rate	was	estimated	through	measuring	soil	ammonium	 and	 nitrate	 nitrogen	 concentration	 (nitroprusside/salicylate	 and	cadmium	 reduction	methods).	 Phospholipid	 fatty	 acid	 analysis,	 ion	 exchange	 resin	analysis	 and	 MicroResp	 system	 were	 used	 to	 evaluate	 microbial	 community	structure,	soil	nutrient	profile	and	microbial	respiration	rate,	respectively.		 The	nitrogen	mineralization	rate	in	peat	mineral	soil	from	laboratory	incubation	was	 much	 higher	 than	 that	 in	 natural	 forest	 soils,	 while	 the	 rate	 in	 forest	 floor			 27	mineral	soil	was	at	a	similar	level	as	in	natural	LFH	layers.	The	mineralization	rates	of	all	three	types	of	mixed	soils	in	this	study	were	approximately	as	twice	as	faster	than	 model	 estimated	 fast	 decomposition	 rate	 (84	 mg	 N	 kg-1	 yr-1).	 The	mineralization	rates	of	peat	mineral	mixed	soil	from	laboratory	test	were	way	faster	than	the	reported	field	nitrogen	mineralization	rates.	 		 After	 four	 week	 of	 incubation	 in	 aerobic	 conditions,	 peat	 mineral	 soil	demonstrated	 the	 highest	 metabolic	 quotient	 (basal	 respiration/total	 microbial	biomass)	but	 fewer	amounts	of	 fungi	 in	microbial	 composition	compare	 to	natural	soils.	Forest	floor	mineral	mix	showed	more	similar	microbial	community	structure	as	 in	 natural	 soils.	 The	 effect	 of	 NPK	 fertilization	 on	 microbial	 structure	 was	 not	prominent	without	vegetation	presence	but	might	be	a	result	of	the	short	incubation	time.	 		 Based	on	the	results	of	ionic	exchange	resin	analysis,	three	times	higher	nitrogen	(mainly	 in	 nitrate	 form)	 content	 was	 found	 in	 peat	 mineral	 and	 peat	 forest	 floor	mixed	 soils	 than	 in	 forest	 floor	mineral	 soils.	 This	 large	 amount	 of	 nitrate	 in	 peat	mineral	and	mixed	soils	serves	as	an	indicator	of	higher	nitrifier	activity,	as	reflected	by	more	gram-negative	bacteria	found	in	these	soils,	but	also	implies	high	N	leaching	potential.	 In	 contrast,	 additional	 N	 was	 retained	 as	 less	 leachable	 ammonium	 in	forest	floor	mineral	soil.	Furthermore,	a	strong	association	between	respiration	and	nutrient	 availability	 was	 also	 found.	 In	 conclusion,	 Mackenzie	 and	 Quideau	recommend	the	use	of	both	peat	mineral	and	forest	soil	and	layering	them	instead	of	mixing	in	future	oil	sands	reclamation	process,	especially	in	N-deficient	areas.	 		Quideau	et	al.	(2013)	–	Comparing	soil	biogeochemical	processes	in	novel	and	natural	boreal	forest	ecosystems:	 		 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	 and	organic	matter	 characterization	 in	 these	 topsoils	were	measured	by	using	 incubating	plant	 root	 simulator	probes,	phospholipid	 fatty	acid			 28	analysis	and	NMR	spectroscopy,	respectively.		 In	this	study,	vegetation	cover	was	the	most	important	factor	that	influenced	the	key	biogeochemical	 processes	 such	 as	nutrient	 availability,	microbial	 communities	and	organic	matter	 characteristics	 in	natural	 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	chemical	compositions	in	reclaimed	sites	compare	to	natural	sites.	Some	differences	in	the	microbial	communities	(two	unique	unsaturated	PLFAs)	and	some	differences	in	 nutrient	 availability	 such	 as	 higher	 N	 and	 S	 concentrations	were	 also	 found	 in	reclaimed	 soils.	 The	 authors	 explained	 these	 differences	 mainly	 by	 the	characteristics	of	materials	used	during	 reclamation	and	above	ground	vegetation.	In	addition,	the	content	of	base	cations	(Ca,	Mg,	K)	were	found	to	be	good	indicators	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.	 		 2.3	Soil	Biological	Properties	Table	3.	Biological	properties	and	descriptions	of	reclaimed	oil	sands	soils	in	Alberta,	Canada.	 	Studies	(Year)	Properties	 Findings	McMillan	et	al.	(2007)	Microbial	activity	-	Lower	MBC	and	MBN	were	found	in	reclaimed	soils	-	Positive	relationship	between	dissolved	organic	N	(DON)	concentration	and	in	situ	MBC	and	MBN	-	Lower	DON,	total	N,	MBN	found	in	reclaimed	sites	-	Forest	floor	mix	in	reclamation	material	help	increasing	microbial	activity	Nitrogen	mineralization	(chemical	property)	-	Similar	level	of	gross	ammonification	rates	in	reclaimed	and	natural	sites	-	Lower	net	ammonification	rates	in	reclaimed	sites			 29	Soil	pH	level	(chemical	property)	 -	Acidic	in	both	reclaimed	and	natural	soils,	range	from	5.38	to	5.95	Bulk	density	(physical	property)	 -	High	bulk	density	in	reclaimed	topsoil	Soil	moisture	and	temperature	(physical	properties)	-	Lower	soil	moisture	and	higher	temperature	in	reclaimed	topsoil	MacKenzie	and	Quideau	(2009)	Microbial	community	structure	-	Season	and	site	conditions	appeared	to	be	the	most	and	second	most	influential	factor	of	microbial	community	structure	-	Slope	did	not	show	a	significant	effect	-	Total	soil	microbial	biomass	(TMB)	and	soil	fungal	to	bacterial	ratio	(FBR)	were	significantly	affected	by	the	interaction	of	time	and	site	but	without	clear	trend	Nutrient	availability	-	Site	conditions	and	season	were	found	to	be	the	most	and	the	second	most	influential	factor	by	ordination	analysis	-	Slope	did	not	show	significant	effects	on	nutrient	availability	 	-	Ammonium	and	nitrate	concentrations	were	significantly	affected	by	time,	site	and	their	interaction	 	-	Boron	as	an	important	micronutrient	increased	later	in	the	growing	season	Dimitriu	et	al.	(2010a)	Microbial	community	composition	and	function	in	peat	-	Negative	relationship	between	respiration	rates	and	microbial	abundance	(dilution	level)	-	Positive	relationship	between	enzyme	activity	and	microbial	abundance	 	-	No	relationship	between	microbial	richness	and	microbial	abundance	-	High	degree	of	microbe	functional	redundancy	-	Both	taxonomic	diversity	and	the	interactions	between	microorganisms	in	the	inoculum	sources	and	peat	type	would	affect	the	relationship	between	microbial	community	composition	and	function	Dimitriu	et	al.	(2010b)	 Enzyme	activities	 -	Soil	reconstruction	material	instead	of	time-since-reclamation	affected	enzyme	activities	the	most			 30	-	Overburden	and	tailing	sands	caused	significant	decrease	in	phenoloxidase	activity	Microbial	community	composition	-	The	use	of	overburden	and	tailing	sands	increased	the	dissimilarities	of	microbial	community	with	natural	sites	-	Fungal-to-bacterial-biomass	ratio,	pH	and	woody	debris	all	significantly	influence	microorganisms	distribution	in	reclaimed	sites	-	Reclaimed	sites	were	gram-negative	bacterial	dominated	while	naturals	sites	were	ectomycorrhizae	fungi	dominated	-	Successful	development	of	microbial	community	on	reclaimed	soils	depended	indirectly	on	vegetation	regrowth	condition	and	directly	on	soil	abiotic	properties,	such	as	pH	and	reclamation	material	Dimitriu	and	Grayston	(2010)	 Soil	bacterial	diversity	-	Similar	bacterial	community	composition	despite	different	aboveground	vegetation	cover	-	α-Proteobacteria,	acidobacterial	and	betaproteobacterial	sequences	were	the	top	three	dominating	bacterial	sequences	-	Soil	pH	and	soil	moisture	were	the	most	regulating	factor	and	indicator	of	soil	bacterial	community	composition	in	reclaimed	and	natural	soils,	respectively	-	Reduction	in	the	diversity	of	active	bacterial	communities	could	further	cause	declines	in	both	richness	and	evenness	of	dominant	taxa.	 	 	Sorenson	et	al.	(2011)	Soil	organic	matter	composition	 -	Carbon	accumulation	occurred	significantly	only	in	reclaimed	aspen	stands	but	not	in	pine	and	spruce	stands	Microbial	communities	-	Very	low	presence	of	visible	fungal	mycelia	and	fine	roots	occurred	in	most	reclaimed	sites,	indicating	low	microbial	activities	-	When	canopy	cover	was	below	30%,	soil	microbial	community	composition	changed	according	to	used	reclamation	subsoil	texture	-	Above	30%,	the	effects	of	stand	types	on	composition	became	more	apparent	Forest	floor	development	-	Reclaimed	aspen	and	spruce	stands	had	thinner	forest	floor	while	reclaimed	jack	pine	stands	had	reached	similar	thickness	as	in	natural	stands	-	Very	thin	H	layer	in	all	reclaimed	stands	-	Canopy	cover	(include	shrub	cover)	played			 31	important	role	in	influencing	forest	floor	thickness	and	soil	carbon	concentration	-	Stand	Age	was	also	but	only	important	in	aspen	stands	Onwuchekwa	(2012)	 Mycorrhizal	composition	-	Peat-mineral	mix	had	the	highest	amount	of	Ectomycorrhizal	(ECM)	colonization	but	quite	low	Arbuscular	mycorrhizal	(AM)	colonization	-	Tailing	sand	had	low	potential	to	support	both	AM	and	ECM	mycorrhizal	fungi	growth	-	Natural	forest	soils	had	intermediate	amounts	of	both	fungal	types	-	Overburden	had	relatively	high	amount	of	ECM	colonization	but	low	AM	colonization	-	Pleosporales	sp.,	Helotiales	type	and	a	species	that	corresponds	to	the	Pyronemataceae	were	the	most	frequently	recorded	fungi	taxa	-	Artificial	ECM	inoculation	experiment	showed	increased	stem	volume	for	pine	and	spruce,	increased	height	growth	of	pine	but	no	such	height	response	in	spruce	and	increased	survival	rate	of	spruce	while	no	such	response	in	pine.		McMillan	 et	 al.	 (2007)	 –	Nitrogen	mineralization	 and	microbial	 activity	 in	 oil	 sands	reclaimed	boreal	forest	soils:	 		 The	objective	of	 this	study	was	 to	compare	 the	microbial	activity	and	nitrogen	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	northern	Alberta.	Soil	cores	were	taken	in	sites	with	three	different	treatments	and	natural	 sites.	 Net	 nitrification,	 ammonification,	 and	 N	 mineralization	 rates	 were	sampled	from	field	incubations	using	buried	bags	and	estimated	by	15N	isotope	pool	dilution	technique.	In	laboratory,	soil	microbial	biomass	C	(MBC)	and	N	(MBN)	were	measured	by	the	chloroform	fumigation-extraction	method.	 In	addition,	a	moisture	manipulation	experiment	was	also	conducted	to	further	investigate	the	relationships	between	 soil	 moisture	 and	 respiration	 rates,	 MBC	 and	 MBN.	 Other	 basic	 soil	chemical	and	physical	properties,	 such	as	bulk	density,	moisture,	 temperature	and	pH	level	were	also	recorded	in	the	field.		 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.	Lower	topsoil	moisture	content	and	higher	soil	temperature	was	found	in	reclaimed	sites,	which	might	be	 caused	by	 the	 lack	of	 forest	 canopy	cover.	All	 reclaimed	and	natural	sites	had	acidic	pH	conditions	(range	from	5.38	to	5.95).	 		 In	 terms	 of	microbial	 dynamics	 in	 reclaimed	 sites,	 lower	MBC	 and	MBN	were	found	in	reclaimed	soils	compared	to	the	natural	soils.	This	may	be	attributed	to	the	lower	 moisture	 content	 in	 reclaimed	 soils	 and/or	 differences	 in	 organic	 matter	compositions.	 A	 positive	 relationship	 between	 dissolved	 organic	 N	 (DON)	concentration	 and	 in	 situ	MBC	 and	MBN	was	 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	other	hand,	net	ammonification	decreased	in	reclaimed	sites,	which	indicated	either	a	stronger	immobilizing	environment	or	faster	nitrification	rate	at	reclaimed	sites.	 	The	 results	 of	moisture	manipulation	 experiment	 confirmed	 that	 natural	 sites	had	more	 active	microbial	 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-mineral	mix	 treatment	 generated	 the	 second	highest	 respiration	 rates,	MBC	 and	 MBN,	 which	 made	 the	 author	 concluded	 that	 forest	 floor	 was	 a	 good	stimulator	of	microbial	activity	to	have	for	oils	sands	reclamation.		MacKenzie	 and	 Quideau	 (2009)	 –	 Microbial	 community	 structure	 and	 nutrient	availability	in	oil	sands	boreal	soils:	 		 In	 this	 study,	 MacKenzie	 and	 Quideau	 tried	 to	 1)	 determine	 the	 relationship	between	 microbial	 community	 structure	 changes	 and	 vegetation,	 seasonal	 and	annual	variability;	2)	understand	the	effects	of	topography	on	microbial	community	structure	and	nutrient	profiles	in	reclaimed	oil	sands	soils.	Three	reclaimed	sites	on	three	different	 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)	 and	nutrient	 availability	 (PRS	probes)	were	measured	 for	 the	 soil	samples	from	each	site.			 33		 Other	 than	site	or	slope	positions,	 seasons	appeared	 to	be	 the	most	 influential	factor	of	microbial	 community	structure	most	 likely	because	of	 the	changes	 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	structure	because	of	the	effects	of	different	amount	of	vegetation	cover	on	sites.	 In	addition,	both	 total	 soil	microbial	biomass	 (TMB)	and	 soil	 fungal	 to	bacterial	 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-mineral	mix	 placement	and	 re-vegetation	 status.	 Surprisingly,	 slope	 did	 not	 have	 consistent	 effects	 on	reclaimed	microbial	 community	 structure	 in	 this	 study,	which	might	 be	 caused	by	undeveloped	soil	structure.	 		 In	terms	of	nutrient	availability,	sites	and	seasons	were	found	to	be	the	most	and	the	second	most	influential	factor	by	ordination	analysis.	Again,	slope	had	no	effects	on	 nutrient	 availability.	 These	were	 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	continuing	microbial	activities.	 		Dimitriu	 et	 al.	 (2010a)	 –	 An	 evaluation	 of	 the	 functional	 significance	 of	 peat	microorganisms	using	a	reciprocal	transplant	approach:		 	 In	order	to	examine	the	relationship	between	microbial	community	composition	and	function	such	as	respiration,	nutrient	acquiring	and	lignin-degradation	in	peat,	Dimitriu	et	al.	 conducted	a	 reciprocal	 transplant	experiment.	Two	distinct	 types	of	sterile	 peat	 samples,	 humified	 (sedge)	 and	 coarse	 plant	 material	 (fibric)	 were	inoculated	with	serially-diluted	suspensions	(10-1,	10-3,	10-5	and	10-8)	from	the	same	or	 reciprocal	 peats.	 After	 five	months	 of	 incubation,	 all	 active	 bacterial	 taxa	were	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	rates	and	dilution	 levels	but	a	positive	one	between	enzyme	activities	and	dilution	levels.	 Bacterial	 richness	 was	 insensitive	 to	 dilution	 levels	 since	 most	microorganisms	can	regrow	easily	when	the	condition	is	right.	Furthermore,	it	was	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	diversity	and	the	interactions	between	microorganisms	in	the	inoculum	sources	and	peat	types	would	affect	the	relationship	between	microbial	community	composition	and	function.	 		Dimitriu	et	al.	(2010b)	–	Impact	of	reclamation	of	surface-mined	boreal	forest	soils	on	microbial	community	composition	and	function:		 This	 study	 researched	 the	 impacts	 of	 soil	 reclamation	 and	time-since-reclamation	on	enzyme	activities	and	microbial	community	composition	in	the	Athabasca	oil	sands	region.	Bulk	soil	in	both	natural	and	reclaimed	sites	that	ranged	 from	5	 to	 30	 years	 old	 and	used	 seven	different	 reclamation	prescriptions	were	 sampled	 for	 extracellular	 enzyme	 activities	 (microplate	 assays)	 and	community	structure	analysis	(PLFA	and	DGGE	analysis).	In	the	field,	measurements	such	as	carbon,	nitrogen,	pH	and	moisture	were	 taken	using	standard	methods.	 In	addition,	nutrient	availability	(plant	root	simulator	probes)	and	vegetation	structure	were	also	recorded.	 		 The	 results	 from	 reclaimed	 sites	 with	 different	 ages	 suggested	 that	 soil	reconstruction	material	instead	of	time-since-reclamation	affected	enzyme	activities	the	most.	The	use	of	overburden	and	tailing	sands,	which	have	low	carbon	content,	caused	 significant	 decrease	 in	 phenoloxidase	 activities	 and	 increased	 the			 35	dissimilarities	 of	 microbial	 community	 with	 natural	 sites	 (based	 only	 on	 PLFA	results)	and	consequently	were	not	recommended	for	reclamation	use.	Furthermore,	it	was	 found	that	different	 factors	controlled	the	distribution	of	microorganisms	in	reclaimed	sites	and	natural	sites,	which	were	fungal-to-bacterial-biomass	ratio	and	soil	nitrogen,	respectively.	However,	if	all	sites	were	analyzed	together,	soil	pH	and	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	 dominated	while	 natural	 sites	were	 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	reclamation	material.	 		Dimitriu	and	Grayston	(2010)	–	Relationship	between	soil	properties	and	patterns	of	bacterial	β-diversity	across	reclaimed	and	natural	boreal	forest	soils:		 Dimitriu	 and	 Grayston	 tried	 to	 quantify	 the	 phylogenetic	 and	 compositional	diversity	 patterns	 of	 soil	 bacteria	 in	 reclaimed	 and	 natural	 sites	with	 two	 distinct	edaphic	characteristics	(xeric-poor	and	mesic-rich)	in	the	Athabasca	oil	sands	region.	Six	 sites	 (two	 xeric-poor,	 two	 mesic-rich	 and	 two	 reclaimed	 sites	 one	 with	vegetation	and	one	without)	were	chosen	for	bulk	soil	sampling.	Bacterial	diversity	under	 phylogenetic	 and	 species-based	 frameworks	 (16S	 rRNA-sequence-based	approach)	and	the	composition	of	active	taxa	(nucleotide	analog)	in	reclaimed	sites	were	determined.	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	 sequences	were	 the	 top	 three	 dominating	 bacterial	 sequences	found	in	most	sites.	In	natural	sites,	soil	moisture	was	the	most	regulating	factor	that			 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,	was	found	to	be	the	most	influential	factor	of	bacterial	community	structure,	which	 explained	16	 to	34%	of	 the	variability.	 In	 addition,	 soil	 pH	was	 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,	which	was	closely	linked	to	“master”	variables	(e.g.	pH,	moisture)	in	this	study,	could	further	cause	declines	in	both	richness	and	evenness	of	dominant	taxa.	 	 		Sorenson	 et	 al.	 (2011)	 –	 Forest	 floor	 development	 and	 biochemical	 properties	 in	reconstructed	boreal	forest	soils:	In	this	study,	Sorenson	et	al.	evaluated	the	influences	of	different	canopy	cover	and	 three	 reclaimed	 stand	 types	 on	 novel	 soil	 organic	 matter	 composition,	 soil	microbial	 communities	 and	 forest	 floor	 development.	 The	 three	 stand	 types	were	trembling	aspen	(Populus	tremuloides),	jack	pine	(Pinus	banksiana)	and	white	spruce	(Picea	glauca)	located	in	north	of	Fort	McMurray,	Alberta	and	all	ranged	between	16	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	such	as	 thickness	and	morphology.	Soil	 samples	were	also	collected	 for	 laboratory	analysis	of	carbon	and	nitrogen	contents	in	mineral	soils	and	forest	floor.	Microbial	community	 composition	 was	 also	 estimated	 by	 various	 methods	 such	 as	phospholipid	 fatty	 acid	 (PLFA),	 ramped-cross-polarization	 (RAMP-CP)	 and	 13C	nuclear	magnetic	resonance	(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	because	the	average	forest	 floor	thickness	 in	natural	pine	stands	 is	 thinner	than	 in	natural	 aspen	 and	 spruce	 stands.	 Morphologically,	 very	 low	 presence	 of	 visible	fungal	mycelia	and	fine	roots	occurred	in	most	sites,	which	led	to	absent	or	very	thin	H	 layers.	These	very	 thin	H	 layers	 indicated	 low	microbial	 activities.	 In	 aspen	and			 37	spruce	 stands,	 canopy	 cover	 played	 an	 important	 role	 in	 influencing	 forest	 floor	thickness	and	 soil	 carbon	concentration.	 Stand	age	was	also	but	only	 important	 in	the	aspen	stands,	which	may	be	a	result	of	the	faster	establishment	of	canopy	cover	in	 time.	 In	 addition	 to	 tree	 canopy,	 shrub	 canopy	 also	 had	 a	 positive	 relationship	with	forest	floor	development	in	coniferous	stands.	 	Although	 carbon	 and	 nitrogen	 concentration	 increased	 in	 the	 aspen	 and	 pine	stands,	the	sign	of	natural	carbon	accumulation	(change	in	the	light	fraction	carbon	composition)	 from	 regrown	 canopy	 was	 only	 clear	 in	 the	 aspen	 stands.	 Another	discovery	of	this	study	was	the	relationships	among	reclamation	prescription,	stand	type,	canopy	cover	and	soil	microbial	community	composition.	When	canopy	cover	was	 below	 30%,	 soil	 microbial	 community	 composition	 changed	 according	 to	reclamation	subsoil	texture.	However,	above	30%,	the	effects	of	stand	types	became	more	apparent.	Therefore,	 the	authors	suggested	that	achieving	30%	canopy	cover	should	be	a	critical	threshold	point	during	soil	reclamation	in	oil	sands	regions.		Onwuchekwa	(2012)	–	Enhanced	revegetation	and	reclamation	of	oil	sands	disturbed	land	using	Mycorrhizae:		 Since	mycorrhizal	 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	strains	in	reclamation	materials	and	conducted	another	experiment	to	evaluate	the	potential	 benefits	 of	 artificial	 ectomycorrhizal	 (ECM)	 fungi	 inoculation	 on	 white	spruce	 and	 jack	 pine	 seedling	 growth	 and	 survival.	 For	 the	 natural	 mycorrhizal	(Arbuscular	mycorrhizal	 and	ectomycorrhizal)	 inoculum	potential	 assessment,	 five	different	 reclamation	 materials,	 including	 peat-mineral	 mix,	 overburden,	 tailing	sands,	topsoil	and	intact	forest	soil,	were	collected	in	the	oil	sands	mining	areas	near	Fort	McMurray,	 Alberta.	 	 Red	 clover	 (Trifolium	pretense)	 and	white	 spruce	 (Picea	glauca)	seeds	were	selected	as	testing	species	for	the	natural	mycorrhizal	inoculum	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	 rates	were	collected	from	field	observation;	biomass	was	obtained	by	combustion	method;	and	mycorrhizal	 type	 was	 determined	 by	 DNA	 extraction	 and	 PCR	 amplification	methods.		 The	 results	 of	 natural	 mycorrhizal	 inoculum	 potential	 reported	 very	 low	presences	of	both	arbuscular	mycorrhizal	(AM)	and	ECM	fungi	in	tailing	sands.	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	amount	of	ECM	colonization	but	 low	AM	colonization.	Topsoil	was	 found	to	be	 the	most	 acceptable	 reclamation	 substrate	 since	 the	 amount	 of	 colonization	 of	 both	species	was	relatively	high.	 		 In	this	study,	Pleosporales	sp.,	Helotiales	type	and	a	species	that	corresponds	to	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	development	of	mycorrhizal	could	be	dramatically	different	in	greenhouse	and	field.		 The	 results	 of	 artificial	 ECM	 inoculation	 experiment	 showed	 increased	 stem	volume	 for	 both	 species,	 increased	 height	 growth	 of	 jack	 pine	 but	 no	 such	 height	increment	in	white	spruce.	This	might	be	attributed	to	site	characteristics	and	better	cooperation	between	jack	pine	roots	and	fungi.	In	addition,	the	survival	rate	of	white	spruce	seedlings	did	 improved	by	more	than	10%	possibly	due	to	higher	moisture	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-introduction	of	mycorrhizal	fungi	during	reclamation	process	has	the	potential	to	become	an	effective	approach	to	improve	vegetation	development.			 39		 2.4	Vegetation	Communities	Table	 4.	 Some	 characteristics	 of	 vegetation	 community	 development	 on	 reclaimed	oil	sands	soils	in	Alberta,	Canada.	 	Studies	(Year)	Properties	 Findings	Cooper	(2004)	 Wetland	vegetation	-	Plant	health	and	rooting	depths	in	the	reclaimed	wetlands	were	acceptable	-	Similar	vegetation	abundance	but	different	species	composition	between	reclaimed	and	reference	wetlands	-	Salinity	in	surface	water	and	subsoils,	wetland	isolation	and	harsh	climatic	condition	are	three	limiting	factors	of	vegetation	development	in	reclaimed	wetlands	and	may	even	alter	species	replacement	sequences	Lilles	et	al.	(2009)	Aspen	and	white	spruce	growth	on	natural	saline	soils	-	White	spruce	growth	was	unaffected	by	the	different	salinity	levels	 	-	Aspen	growth	was	reduced	with	high	salinity	-	Neither	white	spruce	nor	aspen	showed	evidence	of	salinity-related	effects	on	root	distribution	and	nutrient	stress	in	foliage	development	Pinno	et	al.	(2012)	 Aspen	growth	and	development	-	Soil	type	(mainly	organic	matter	content)	had	the	largest	impact	on	aspen	growth	when	no	fertilizer	was	applied.	But	the	impact	diminished	after	fertilization	-	No	impact	of	soil	type	was	found	on	seed	germination	and	seedling	establishment	-	Aspen	growth	was	only	positively	related	to	increasing	K	availability	-	Incomplete	fertilization	might	give	aspen	an	even	lower	bud	set	than	no	fertilization	Kovalenko	et	al.	(2013)	 Wetland	food	web	structure	 	-	Reclaimed	wetlands	were	low	in	macrophyte	biomass,	microbial	biomass,	trophic	diversity	and	invertebrate	richness	but	high	in	the	concentration	of	naphthenic	acids	compare	to	reference	wetlands	-	Wetland	age	and	peat-mineral	mix	did	not	significantly	mitigate	the	effects	of	oil	sands	waste	materials	on	the	aquatic	biota	but	still	some	improvement	in	biomass	of	major	biotic	compartments	-	Low	C:	N	ratios	in	reclaimed	wetlands		Copper	(2004)	–	Vegetation	community	development	of	reclaimed	oil	sands	wetlands:		 In	Copper’s	study,	he	tried	to	answer	whether	chemical	and	physical	conditions	of	 reclaimed	wetlands	would	 intervene	with	 vegetation	development	 and	whether	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	species	richness,	aerial	percent	cover	and	similarity	of	the	vegetation	among	a	newly	constructed	consolidated/composite	tailings	(CT)	wetland,	a	natural	wetland	and	an	opportunistic	wetland	 for	 two	 years.	 Other	measurements	 such	 as	metals,	 anions,	electrical	conductivity,	pH	and	temperature	in	water	were	also	taken.	 		 The	 results	of	visual	 assessments	of	plant	health	and	 rooting	depths	 in	 the	CT	wetland	indicated	that	the	physical	and	chemical	conditions	of	tailings	did	not	limit	plant	 growth	 and	 survival	 for	 most	 species.	 However,	 despite	 the	 similar	 species	abundances,	 the	 species	 compositions	 between	 reconstructed	 CT	 wetland	 and	reference	wetlands	were	quite	different.	This	partially	might	be	caused	by	the	high	natural	 variability	 in	 water	 regimes	 in	 the	 reference	 wetlands.	 Some	 species	emergence	was	inhibited	from	reclaimed	wetland	subsoils	due	to	high	salinity.	The	author	proposed	 that	 salinity	 in	 surface	water	 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	replacement	sequences.		Lilles	 et	 al.	 (2012)	 –	 Growth	 of	 aspen	 and	 white	 spruce	 on	 naturally	 saline	 sites	 in	northern	 Alberta:	 implications	 for	 development	 of	 boreal	 forest	 vegetation	 on	reclaimed	saline	soils:		 Since	a	lot	of	reclaimed	oil	sands	soils	have	high	salinity,	Lilles	et	al.	investigated	the	height	and	basal	area	growths	of	mature	trembling	aspen	and	white	spruce	on	six	natural	sites	across	a	saline	gradient	(high,	medium,	low	and	control)	in	order	to	predict	future	forest	productivity	on	reclaimed	saline	soils	in	northern	Alberta.	Tree	growth	rates	of	height	and	basal	area,	root	distributions	and	foliar	parameters	were	collected	in	these	sites.	 		 It	 seemed	 that	 white	 spruce	 growth	 was	 unaffected	 by	 the	 different	 salinity	levels	while	mature	aspen	growth	was	reduced	with	high	salinity.	Although	medium	and	low	saline	soils	provided	fast	aspen	growth,	aspen	in	the	high-salinity	sites	had	similar	growth	rates	in	pest-	and	pathogen-stressed	stands.	The	effects	of	salinity	on	aspen	growth	might	 get	 even	 stronger	with	 time.	The	differences	 in	plant	biology,			 41	such	 as	 shade-tolerance	 ability	 and	 natural	 growth	 rate	 variability,	 explained	 the	differences	between	aspen	and	white	spruce	growths	in	response	to	salinity.	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	 should	not	 be	used	 for	 forestry	production	purpose	due	 to	the	low	productivity.	 		Pinno	et	al.	(2012)	–	Trembling	aspen	seedling	establishment,	growth	and	response	to	fertilization	on	contrasting	soils	used	in	oil	sands	reclamation:		 This	 study	 used	 a	 greenhouse	 experiment	 to	 examine	 the	 complete	 cycle	 of	aspen	 growth	 and	 development	 on	 a	wide	 range	 of	 soil	 types.	 These	 soils	 all	 had	been	used	as	surface	materials	during	oil	sands	reclamation.	Eight	distinct	salvaged	stockpiles	 of	 soil	with	 a	 range	 in	 fertility,	 pH,	 organic	matter	 content	 and	 P	were	used,	which	were	peat-mineral	mix,	forest	floor-mineral	mix,	B	horizon-very	high	P,	B	horizon-low	P	and	low	pH,	B	horizon-high	P	and	low	pH,	B	horizon-low	P	and	high	pH,	 subsoils	 and	 tailing	 sands.	 Variables	 that	 were	 measured	 include	 seed	germination	and	survival	rates	as	well	as	height	growth	before	and	after	fertilization.	 		 The	 results	 suggested	 that	 soil	 type	 had	 the	 largest	 impacts	 on	 aspen	 growth	when	no	 fertilizer	was	 applied.	 But	 the	 impacts	 diminished	 after	 fertilization.	 The	best	and	worst	aspen	growth	was	found	on	soils	with	abundant	organic	matter,	such	as	peat-mineral	and	forest	floor-mineral	mix,	and	soils	with	low	organic	matter,	such	as	subsoil	and	tailing	sands,	respectively.	No	impact	of	soil	type	was	found	on	seed	germination	and	seedling	establishment	since	consistent	water	supply	was	provided	in	the	greenhouse.	 	Although	N,	P	K	appeared	to	all	below	the	optimal	 foliar	concentrations,	aspen	growth	 was	 only	 positively	 related	 to	 increasing	 K	 availability.	 This	 is	 probably	because	of	 the	 large	 imbalances	within	the	 internal	N:	P	ratios.	Surprisingly,	aspen	growth	 did	 not	 response	 significantly	 to	 PK	 fertilization	 given	 the	 very	 low	 P	availability	 in	some	soils	and	the	positive	relationship	with	K.	Another	noteworthy			 42	finding	 was	 that	 incomplete	 fertilization	might	 give	 aspen	 an	 even	 lower	 bud	 set	than	a	no	fertilization	treatment.	 		Kovalenko	et	al.	(2013)	–	Food	web	structure	in	oil	sands	reclaimed	wetlands:		 Kovalenko	 et	 al.	 aimed	 to	 firstly	 characterize	 the	 effects	 of	 oil	 sands	 process	materials	(tailings	and	water)	and	peat-mineral	mix	on	food	web	compartments	and	carbon	 flows	 in	 reconstructed	 wetlands	 and	 then	 evaluate	 the	 effects	 of	time-since-reclamation	 on	 wetland	 trophic	 structure.	 In	 order	 to	 do	 these,	 17	naturally	formed	reference	wetlands	and	12	oil	sands-affected	wetlands,	which	were	constructed	in	1970	to	2004	with	tailings	and	water,	were	selected	for	accessing	the	composition	 and	 biomass	 of	 aquatic	 plants	 and	 invertebrates	 (sweep	 nets	 and	floating	 hoop	 traps),	 microbial	 biomass	 (chlorophyll	 a	 concentrations	 and	combustion	method),	and	food	web	structure	(stable	isotope	data).		 The	 results	 indicated	 that	 reclaimed	 wetlands	 were	 significantly	 low	 in	macrophyte	biomass,	microbial	biomass,	trophic	diversity	and	invertebrate	richness	but	 high	 in	 the	 concentration	 of	 naphthenic	 acids,	 which	 is	 a	 toxic	 constituent,	compared	with	reference	wetlands.	Several	other	inorganic	compounds	in	oil	sands	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	invertebrate	and	macrophyte	biomasses	in	reclaimed	wetlands.	 		 In	 terms	 of	 the	 effects	 of	 time-since	 reclamation	 and	 peat-mineral	 mix	amendment,	there	was	insufficient	evidence	to	conclude	that	wetland	age	and	peat	could	mitigate	 the	effects	of	oil	 sands	waste	materials	on	 the	aquatic	biota	despite	peat’s	complex	direct	and	indirect	effects	on	water	quality.	But	the	older	reclaimed	wetlands	tended	to	have	slightly	higher	biomass	of	major	biotic	compartments,	such	as	 benthic	 and	 planktonic	 invertebrates,	 and	 emergent	 macrophytes	 than	 the	younger	ones.	Lastly,	the	author	also	pointed	out	that	the	lower	C:	N	ratios	found	in	reclaimed	wetlands	could	be	a	sign	of	nitrogen	limitation.			 43	3.	Discussion	3.1	Reclamation	Treatments	Effects		 In	general,	the	reclaimed	oil	sands	soils	are	quite	different	from	natural	soils	in	many	 soil	 physical,	 chemical	 and	 biological	 properties.	 For	 starters,	 compare	 to	natural	boreal	forest	soils,	higher	soil	temperature	and	lower	moisture	content	could	be	 found	 in	 recently	 reclaimed	sites	due	 to	 lack	of	 layer	 (McMillan	et	al.	 2007).	 In	addition,	organic	matter	content	and	organic	matter	accumulation	rate	were	found	significantly	 different	 between	 reclaimed	 and	 natural	 forest	 sites	 in	 several	examined	studies	such	as	Trites	and	Bayley	2009,	Quideau	et	al.	2013	and	Anderson	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	overburden	possessed	adverse	chemical	properties.	However,	in	reclaimed	wetlands,	Trites	 and	 Bayley	 (2009)	 found	 that	 input	 litter	 type	 instead	 of	 reclamation	materials	was	the	stronger	influencing	factor	of	decomposition	rate.	The	causes	for	this	different	response	between	wetlands	and	forests	require	further	 investigation.	Possible	 candidates	 of	 the	 causes	 might	 be	 different	 microbial	 communities	composition	and/or	different	microbial	activities	levels.	Bulk	density	was	 also	 found	 to	 be	 higher	 in	 reclaimed	 soils	 due	 to	 equipment	compaction	during	reclamation	by	McMillan	et	al.	2007.	Surprisingly,	Yarmuch	2003	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.	These	contrasting	results	of	bulk	density	demonstrated	the	potential	of	preventing	soil	compaction	with	careful	 low-impact	management	and	the	necessity	of	promoting	these	techniques.	For	chemical	properties,	the	higher	nitrogen	(N)	content	in	reclaimed	soil	is	the			 44	most	prominent	difference	compare	to	natural	soils	as	supported	by	Rowland	2008,	Hemsley	2012,	MacKenzie	and	Quideau	2012	and	Kovalenko	et	al.	2013.	This	might	be	 attributed	 to	 the	 higher	 atmospheric	 nitrogen	 deposition	 in	 reclaimed	 soils,	which	is	caused	by	the	lower	canopy	covers	(Hemsley	2012;	MacKenzie	and	Quideau	2012).	 Nevertheless,	 in	 contrast	 to	 those	 studies,	 McMillan	 et	 al.	 (2007)	 found	 a	lower	 total	N	 and	 lower	net	nitrogen	mineralization	 rate	 in	 reclaimed	 forest	 soils.	The	 reason	 might	 be	 that	 MacKenzie	 and	 Quideau	 (2012)	 obtained	 the	 N	mineralization	rates	results	only	 for	peat-mineral	mix	and	forest-floor	mineral	mix	soils.	 And	 these	 results	 were	 from	 laboratory	 inoculation	 instead	 of	 filed	measurements.	 The	 real	 field	 N	mineralization	 rate	 can	 be	 suppressed	 due	 to	 the	adverse	 chemical	 conditions	 created	 by	 other	 reclamation	 materials	 such	 as	overburden	and	tailings.	In	terms	of	microbial	communities,	more	bacterial	and	less	fungi	were	found	in	reclaimed	soils	compare	to	natural	soils	(Dimitriu	et	al.	2010b;	Sorenson	et	al.	2011).	McMillan	et	al.	(2007)	found	lower	microbial	biomass	C	and	microbial	biomass	N	in	reclaimed	soils,	which	 implied	 lower	microbial	activity.	This	might	be	 the	result	of	the	slightly	higher	pH	level	in	reclaimed	soils	(Rowland	2008)	since	multiple	studies	showed	that	soil	moisture	and	pH	are	the	two	most	important	factors	that	shape	soil	microbial	 community	 structure	 in	 reclaimed	 soils	 (Mackenzie	 and	 Quideau	 2009;	Dimitriu	et	al.	2010b;	Dimitriu	and	Grayston	2010).	A	more	concerning	 fact	 is	 that	the	 negative	 effects	 of	 reclamation	 materials	 on	 microbial	 enzyme	 activities	 can	persist	even	after	the	sites	became	old	(Dimitriu	et	al.	2010b).	The	 vegetation	 communities	 of	 reclaimed	 forest	 and	wetlands	 appeared	 to	 be	growing	but	not	as	 good	as	 in	natural	 sites.	 In	wetlands,	different	 compositions	of	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	chemical	pollutant	levels	in	reclaimed	wetlands.	 	Lastly,	 some	mitigating	effects	of	 time	were	observed	 in	 a	 few	studies	 such	as	Rowland	2008,	Sorenson	et	al.	2011	and	Kovalenko	et	al.	2013.	Although	vegetation			 45	communities	and	 forest	 floor	 in	aspen	appear	 to	be	able	 to	achieve	similar	natural	stages	 approximately	 25	 years	 after	 reclamation,	 some	 more	 resistant	 soil	properties	like	texture	and	the	forest	floor	in	conifer	forests,	which	have	less	organic	matter	inputs,	will	not	be	able	to	recover	to	the	pre-disturbance	state	even	after	20	years.	3.2	Reclamation	and	Management	Implications		 Other	than	the	aforementioned	low-impact	reclamation	techniques,	many	other	reclamation	and	management	lessons	can	be	learned	based	on	the	research	results,	namely:	1. Topsoil	 was	 found	 to	 be	 the	most	 acceptable	 reclamation	 substrate	 in	terms	 of	 mycorrhizal	 fungi	 growth	 supporting	 ability.	 The	 use	 of	overburden	 and	 tailing	 sands	 should	 be	 minimized	 and/or	 carefully	planned	due	 to	 their	 low	ability	 to	 support	enzyme	activities	and	 fungi	growth	as	well	as	their	potential	to	increase	dissimilarities	of	microbial	community	compositions	between	natural	and	reclaimed	soils	(Dimitriu	et	al.	2010b;	Onwuchekwa	2012)	2. The	use	of	forest	floor	during	reclamation	as	an	organic	amendment	can	improve	 soil	 nitrogen	 mineralization	 rate	 (McMillan	 et	 al.	 2007;	MacKenzie	and	Quideau	2009).	Layering	the	peat-mineral	mix	and	forest	floor	 mineral	 mix	 soil	 instead	 of	 mixing	 them	 is	 also	 recommended	(MacKenzie	and	Quideau	2009).	3. Complete	 fertilization	 is	 necessary	 for	 aspen	 stands	 growth	 since	incomplete	 fertilization	might	 give	 reclaimed	 aspen	 stands	 even	 lower	bud	set	than	a	no	fertilization	treatment	(Pinno	et	al.	2012).	Good	aspen	growth	requires	both	organic	matter	and	K	fertilization.	4. 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	 will	 not	 be	 suitable	 for	 commercial	 forestry	production	purpose	because	of	the	low	productivity	(Lilles	et	al.	2009).			 46	5. For	 faster	 organic	 quality	 improvement,	 aspen	 can	 be	 planted	 in	reclaimed	 sites	 since	 reclaimed	aspen	 stands	had	 faster	decomposition	rates	and	better	carbon	accumulation	than	reclaimed	jack	pine	and	white	spruce	stands	 (Sorenson	et	al.	2011).	However,	 for	areas	needs	 thicker	forest	floor,	jack	pine	is	preferred	than	aspen	and	white	spruce	due	to	its	low	decomposition	rate	(Sorenson	et	al.	2011).	 	6. Since	nitrogen	is	excessive	 in	many	reclaimed	sites,	more	N	demanding	species	can	be	planted	to	avoid	N	leaching	(Hemsley	2012),	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,	assisting	the	reintroduction	of	ecotomycorrhizal	fungi	in	reclaimed	sites	should	be	encouraged	if	commercially	available.	8. Better	salinity	control	might	be	needed	in	wetland	reclamation	because	salinity	is	still	an	important	limiting	factor	of	vegetation	development	in	reclaimed	wetlands	and	may	even	alter	 species	 replacement	sequences	(Cooper	2004).	9. Reclamation	monitoring	 program	may	use	 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).	3.3	Limitations	and	Future	Researches	Although	most	of	the	studies	(15	out	of	20)	in	this	report	was	conducted	by	(or	involved	with)	University	of	Alberta,	universities	 in	neighboring	provinces	 such	as	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,	many	more	 studies	 are	 being	 finished	 and	published	every	year.	For	instance,	one	master	thesis	that	studies	the	relationships	between	vegetation	 types	 and	 soil	 carbon	 is	 just	 about	 to	 finish	 in	UBC.	Given	 the			 47	large	 amount	 of	 researches,	 this	 paper	 definitely	 will	 not	 be	 able	 to	 cover	 all	published	studies	and	future	publications	on	the	properties	of	reclaimed	soils.	 	Another	 major	 limitation	 of	 this	 study	 is	 the	 absence	 of	 statistical	 analysis.	Researches	of	reclaimed	soils	properties	vary	in	methods	and	results.	The	causes	of	these	variances	and	some	even	contradicting	results	can	only	be	speculated	without	proper	statistical	analysis.	Both	 limitations	call	 for	the	necessity	of	a	meta-analysis	on	 reclaimed	 soils	 properties	 since	 meta-analysis	 allows	 researchers	 to	simultaneously	study	multiple	factors	of	a	particular	issue	across	a	broad	scale	and	find	the	hidden	trends	(Arnqvist	and	Wooster	1995).	 	Other	 than	meta-analysis,	 since	many	 researches	 have	 built	 the	 foundation	 of	basic	physical,	chemical	and	biological	properties	of	reclaimed	oil	sands	soils,	more	researches	 may	 start	 to	 shift	 toward	 some	 second-	 and	 third-order	 effects	 of	reclaimed	soils.	For	example,	more	 in	depth	 investigation	on	vegetation	responses,	local	hydrology	change	and	wildlife	population	behavior	and	recovery	in	reclaimed	stands	all	can	be	researched	in	the	near	future.	 	Last	but	not	least,	I	found	that	many	researches	that	studied	the	effects	of	time	on	 reclaimed	 soil	 properties	 used	 earlier	 sampled	 soils	 as	 their	 reference	 soils.	Including	the	original	samples	of	reclamation	materials	at	time	zero	when	possible	is	recommended	 for	 future	 time-effect	 researches	 since	 the	 time-zero	 samples	 may	provide	more	sound	and	effective	evidences	of	 for	 the	effects	of	 time	on	reclaimed	soil	properties.	 		 		 			 48	References	Alberta	Environmental	Protection.	1998.	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