FACILITATING NATIVE PLANT RECOVERY ON COPPER
MINE TAILINGS IN THE SEMIARID GRASSLANDS OF
SOUTHERN INTERIOR BRITISH COLUMBIA
by
PAUL MICHAEL ANTONELLI
BNRSc (Honours), Thompson Rivers University, 2013

A THESIS SUBMITTED IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF
MASTER OF SCIENCE
in Environmental Science

This thesis has been accepted as conforming to the required standards by:
Dr. Lauchlan Fraser (Ph.D.), Thesis Supervisor, Department of Biological Sciences and
Department of Natural Resource Sciences, Thompson Rivers University
Dr. Wendy Gardner (Ph.D.), Supervisory Committee Member, Department of Natural Resource
Sciences, Thompson Rivers University
Dr. Tom Pypker (Ph.D.), Supervisory Committee Member, Department of Natural Resource
Sciences, Thompson Rivers University
Dr. Philip Burton (Ph.D.), External Examiner, Department of Ecosystem Science and
Management, University of Northern British Columbia
Dated this 4th day of May, 2018, in Kamloops, British Columbia, Canada

© Paul Michael Antonelli, 2018

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ABSTRACT
Thesis Supervisor: Professor Dr. Lauchlan Fraser

The semiarid grasslands of interior British Columbia (B.C.) are a unique ecosystem
which provides an array of economic and ecological resources, but historic and current human
and environmental pressures have led to their decline. Surface mining involves stripping the
natural vegetation and topsoil, altering of natural topography, and deposition of waste materials
(e.g. tailings and waste rock) at the landscape level. Restoration of natural soil processes and
native vegetation communities on such sites is challenging because 1) the mine soils are often
characterized by having adverse physiochemical properties such as high metals content, extreme
pH, and low organic matter, 2) there are barriers to native seed acquisition and native species do
not perform well on nutrient poor sites, and 3) seedling germination and establishment is limited
in semiarid environments because of prevailing harsh climatic conditions. The primary
objectives at the onset of mine reclamation are to ameliorate the physical and chemical properties
of the soils (usually with an organic amendment) and establish a sustainable vegetative cover to
prevent wind and water erosion of metals and other harmful contaminants (a process known as
phytostabilization). Facilitation by nurse plants and cover crops has recently come to the
forefront as a potentially promising practice for restoring natural communities on degraded sites
in stressful environments. The objectives of this thesis were to 1) investigate the suitability of
locally available organic soil amendments and native bunchgrasses (Pseudoroegneria spicata
and Festuca campestris) for reclamation at the Historic Afton Tailings Storage Facility (TSF),
near Kamloops, B.C., in a greenhouse study and 2) assess the facilitative effects of soil
amendments, Artemesia tridentata nurse plants, and agronomic cover crops on various abiotic
and biotic parameters relating to native grassland species establishment at the TSF. In the
greenhouse, plants were grown in various ash-compost-wood chip combinations and were
evaluated using a randomized complete block design with 13 treatments and 10 replicates. In the
field, native plants were seeded in small (1.23 m2) study plots with cover crops and/or planted
with nurse plants in amended tailings and assessed in a randomized complete block design with 8
treatments and 3 replicates. The results of the greenhouse study indicated that compost was the
most effective amendment, as it effectively ameliorated tailings physiochemical properties and
promoted significantly greater seedling production. Analysis of shoot tissue elemental

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concentrations after 90 d growth determined that both species were not suitable candidates for
phytostabilization because they accumulated high amounts of molybdenum. Artemisia tridentata
nurse plants appeared to exert some facilitative effects including shading which resulted in lower
soil temperatures early in the growing season, but there was also some evidence that they
competed for soil moisture. Nonetheless, plant species diversity was higher under nurse plants
compared to in the open, which indicated that some facilitative mechanisms may be at play.
Cover crops appeared to have a negative effect on native plant establishment which was likely
because of their aggressive growth characteristics and increased competition for soil moisture.
The findings of this study provide important considerations for mine restoration practices in
B.C.’s semiarid grasslands.

Keywords: Facilitation, nurse plants, cover crops, soil amendments, semiarid grassland, native
species

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DEDICATION
I hereby dedicate this thesis to my grandfather, Peter L. Antonelli, and my grandmother, Marylu
Walters, who have both provided a great amount of support and encouragement throughout my
academic pursuit. Thank you.

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ACKNOWLEDGEMENTS
Firstly, I would like to thank my supervisors Dr. Lauchlan Fraser and Dr. Wendy Gardner, for
encouraging me to purse graduate studies after the completion of my undergraduate thesis, and
for providing academic support throughout my time at Thompson Rivers University.

Secondly, I would like to thank KGHM International and the National Sciences and Engineering
Research Council (NSERC) for providing the primary funding for this research. I would also like
to thank KGHM and New Gold for granting access to the study site.

Thirdly, I would like to thank the Contaminated Sites Approved Professionals (CSAP) Society,
the Mining Association of British Columbia, the Canadian Institute of Mining (CIM), the
Technical Research and Committee on Reclamation (TRCR), and the Graduate Studies
Department at Thompson Rivers University for recognizing my hard work and dedication and
rewarding me through scholarships, bursaries and/or grants.

Lastly, I would like to thank my peers, friends, and family for their ever-lasting support and
encouragement throughout my journey through academia.

I must also acknowledge the role of music and the arts in bringing a healthy balance and
mindfulness to my everyday life.

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TABLE OF CONTENTS
Abstract ....................................................................................................................................... i
Dedication ................................................................................................................................. iii
Acknowledgements ................................................................................................................... iv
Table of Contents ...................................................................................................................... v
List of Figures ......................................................................................................................... viii
List of Tables............................................................................................................................. xi
Chapter 1 – INTRODUCTION ................................................................................................... 1
The Importance of Grasslands ................................................................................................. 1
The Mining Industry and its Impacts on the Environment .................................................. 2
Mine Reclamation ..................................................................................................................... 3
Soil Amendments .................................................................................................................... 5
Seeding .................................................................................................................................... 6
Phytostabilization .................................................................................................................... 7
Facilitation and Nurse Plants ................................................................................................... 8
Cover Crops ............................................................................................................................. 9
Thesis Research Objectives .................................................................................................... 10
Literature Cited ....................................................................................................................... 12
Chapter 2 – GROWTH RESPONSE AND METALS UPTAKE OF NATIVE
BUNCHGRASSES DURING ORGANIC AMENDMENT-ASSISTED
PHYTOSTABILIZATION OF ALKALINE MINE TAILINGS ........................................... 18
Introduction ............................................................................................................................. 18
Materials & Methods .............................................................................................................. 22
Mine Tailings and Amendment Analysis .............................................................................. 22
Greenhouse Experiment ........................................................................................................ 23
Results ...................................................................................................................................... 25
Mine Tailings and Amendment Characteristics .................................................................... 25
Growth Response to Soil Amendments ................................................................................. 27
Plant Metals Uptake............................................................................................................... 31
Discussion ................................................................................................................................. 34
Effect of Organic Amendments on Tailings Characteristics ................................................. 34
Growth Response to Organic Amendments .......................................................................... 35
Effect of Amendments on Metals Uptake ............................................................................. 36
Conclusion ................................................................................................................................ 37
Literature Cited ....................................................................................................................... 39
Chapter 3 – FACILITATING MINE RESTORATION IN A SEMIARID
ENVIRONMENT WITH NURSE PLANTS, COVER CROPS AND SOIL
AMENDMENTS ......................................................................................................................... 43
Introduction ............................................................................................................................. 43

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Materials & Methods .............................................................................................................. 49
Study Site ............................................................................................................................... 49
Experimental Design ............................................................................................................. 51
Soil Amendments .................................................................................................................. 52
Nurse Plants ........................................................................................................................... 53
Seed Mix Selection and Seeding ........................................................................................... 54
Irrigation System Set-up ........................................................................................................ 55
Data Logger Set-up ................................................................................................................ 57
Data Collection ...................................................................................................................... 57
Statistical Analyses ................................................................................................................ 59
Results ...................................................................................................................................... 60
Soil Temperature ................................................................................................................... 60
Soil Moisture ......................................................................................................................... 61
Soil Amendments .................................................................................................................. 62
Plant Community Establishment ........................................................................................... 65
Plant Productivity .................................................................................................................. 66
Plant Community Diversity ................................................................................................... 66
Discussion ................................................................................................................................. 72
Effect of Nurse Plants on Abiotic and Biotic Parameters ..................................................... 72
Effect of Agronomic Cover Crops on Abiotic and Biotic Parameters .................................. 77
Conclusion ................................................................................................................................ 79
Literature Cited ....................................................................................................................... 81
Chapter 4 – RESEARCH CONCLUSIONS, MANAGEMENT IMPLICATIONS AND
FUTURE RESEARCH ............................................................................................................... 88
Research Conclusions ............................................................................................................. 88
Greenhouse Study .................................................................................................................. 88
Field Study............................................................................................................................. 90
Management Implications & Future Research .................................................................... 91
Soil Amendments .................................................................................................................. 91
Phytostabilization .................................................................................................................. 92
Nurse Plants ........................................................................................................................... 92
Cover Crops ........................................................................................................................... 93
Literature Cited ....................................................................................................................... 95
Appendix A – SEED GERMINATION TRIAL ...................................................................... A1
Introduction ............................................................................................................................ A1
Materials & Methods ............................................................................................................. A1
Experimental Design ............................................................................................................ A1
Statistical Analysis ............................................................................................................... A2
Results & Discussion .............................................................................................................. A3
Viability of Native Seed ....................................................................................................... A3

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Comparison of Native Species vs. Agronomic Species ....................................................... A4
Effect of Gibberellic Acid on Seed Germination ................................................................. A5
Summary/Conclusions ........................................................................................................... A6
Literature Cited ...................................................................................................................... A7
Appendix B – LABORATORY ANALYTICAL RESULTS .................................................. B1

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LIST OF FIGURES
Figure 2.1. Map of study site at the Historic Afton Tailings Storage Facility 15 km west of
Kamloops, British Columbia. The red marker indicates the location of the tailings site. Green
pins indicate the locations from which the soil amendments were obtained. Compost was from
the City of Kamloops composting facility, wood ash was from the Domtar Pulp Mill, and wood
chips were from a local veneer/plywood factory. ......................................................................... 23
Figure 2.2. View of randomized complete block design used for greenhouse growth trial. ........ 25
Figure 2.3. Pseudoroegneria spicata (left column) and Festuca campestris (right column)
seedling growth after 90 days. From top to bottom: treatments are control, ash, blend and
compost. ........................................................................................................................................ 29
Figure 2.4. Mean Pseudoroegneria spicata and Festuca campestris a) seedling emergence and b)
shoot heights by treatment after 90 d growth in amended mine tailings. Error bars are standard
errors of the mean. Treatments with different letters are statistically significant at P < 0.05 (oneway ANOVA, Tukey’s HSD). * represents statistical significance between species (determined
by t-test) for that treatment. .......................................................................................................... 30
Figure 2.5. Mean Pseudoroegneria spicata and Festuca campestris a) shoot biomass and b) root
biomass per pot by treatment after 90 d growth in amended mine tailings. Error bars are standard
errors of the mean. Treatments with different letters are statistically significant at P < 0.05 (oneway ANOVA, Tukey’s HSD). * represents statistical significance between species (determined
by t-test) for that treatment. .......................................................................................................... 30
Figure 2.6. Relationship between a) Pseudoroegneria spicata total biomass (roots + shoots) and
b) Festuca campestris total biomass per pot and relative concentrations of compost and ash in the
soil amendment mixtures. Data points are untransformed raw data. ............................................ 31
Figure 3.1. Map of study site at the Historic Afton Tailings Storage Facility adjacent to the New
Gold mine, 15 km west of Kamloops, British Columbia. The red marker indicates the location of
the research site. Green pins indicate the locations from which the soil amendments were
obtained. Compost was from the City of Kamloops composting facility and wood ash was from
the Domtar Pulp Mill. ................................................................................................................... 50
Figure 3.2. View of Historic Afton Tailings Storage Facility research plots (left) and individual
plot containing unamended tailings (right). .................................................................................. 51
Figure 3.3. Experimental plot layout for 2016 TSF field study where NP = nurse plant and CC =
cover crop. Soil amendments are indicated by shaded cells and include a ‘compost’ treatment

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and a ‘compost + ash’ treatment. All plots were seeded with a custom native seed mix. Each
combination of treatment factors is represented once within each column (block), and therefore is
replicated three times (n=3). ......................................................................................................... 52
Figure 3.4. View of soil amendments and tailings prior to mixing (left) and amended study plot
(right). ........................................................................................................................................... 53
Figure 3.5. Measuring sagebrush seedlings in the greenhouse prior to transplanting (top left),
transplanted nurse plants at the TSF (top right) and arrangement of nurse plants (S=small,
M=medium, L=large) (bottom). The arrangement of nurse plant size classes was systematic and
consistent throughout study plots. ................................................................................................ 54
Figure 3.6. View of automatic gravity feed drip irrigation system installed at the Historic Afton
TSF research site in 2015. A 2000-gallon water tank elevated on the tailings dam (top left), 3way independent water delivery system (top right), low pressure automatic irrigation timer
(bottom left) and ½ gallon/hr. drip nozzle (bottom right)............................................................. 56
Figure 3.7. Tailings mean and maximum temperature (left) and moisture (right) at the Historic
Afton Tailings Storage Facility over the 2016 study season (April–August). Soil temperature and
moisture were measured at the 5 cm depth (Hobo®, Onset Computer Corporation, Bourne, MA)
in an exposed location. .................................................................................................................. 57
Figure 3.8. Assessing plant cover with a 0.25 m2 quadrat (left) and measuring horizontal
sagebrush canopy area with a custom 2-inch checkerboard (R) during 2016 data collection. ..... 59
Figure 3.9. Mean daily soil temperature (left) and mean daily maximum soil temperature (right)
of study plots with and without big sagebrush nurse plants. Error bars are standard error of the
mean. The * represents a significant treatment effect at the 5% probability level. ...................... 61
Figure 3.10. Time course of soil surface temperature of plots with and without Artemisia
tridentata nurse plants and at an exposed location at the Historic Afton Tailings Storage Facility,
on a clear, hot day in late spring (May 28, 2017). Data points are an average of twelve study
plots except for the exposed tailings which is an average of two similar locations. .................... 64
Figure 3.11. Mean volumetric soil moisture content of study plots with and without agronomic
cover crop (averaged over the study period and by month). June data includes Seed × Amendment
interaction (comp = compost). Error bars are standard error of the mean. Treatments with
different letters are statistically different at the 5% probability level. .......................................... 64

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Figure 3.12. Total plant cover (left) and aboveground plant biomass (right) with and without
Artemisia nurse plants. Error bars are standard error of the mean. Treatments with different
letters are statistically different at the 5% probability level. ........................................................ 69
Figure 3.13. Native graminoid cover (left) and Poa spp. cover (right) response to nurse
plant/cover crop treatments. Error bars represent standard error of the mean. Treatments with
different letters are statistically different at the 5% probability level. .......................................... 69
Figure 3.14. Effect of agronomic cover crops on Pseudoroegneria spicata cover (left) and effect
of cover crops/soil amendments on Elymus trachycaulus cover. Error bars represent standard
error of the mean. Treatments with different letters are statistically different at the 5% probability
level. .............................................................................................................................................. 69
Figure 3.15. Relationship between volunteer species cover and sagebrush abundance parameters
a) canopy elliptical volume, b) aboveground biomass, c) horizontal canopy area and d) canopy
cover. ............................................................................................................................................. 71
Figure 3.16. Effect of cover crops on species richness (left) and effect of nurse plant/cover crops
on Simpson’s diversity index (right). Error bars represent standard error of the mean. Treatments
with different letters are statistically different at the 5% probability level................................... 71
Figure A.1. View of randomized block layout (top left), Festuca campestris seed prior to
germinating (top right), emerging Balsamorhiza sagittata seed (bottom left) and Allium cernuum
seed (bottom right). Treatments were solutions containing either a)1000 ppm Gibberellic acid or
b) deionized water (top left)..A2
Figure A.2 Cumulative germination rates of native grasses over a 30-day greenhouse trial. Error
bars are standard error of the mean. Treatments were a 1000 ppm Gibberellic acid solution (GA)
and deionized water (control)…………………………………………………………………...A3
Figure A.3. Cumulative germination rates of native forbs over a 30-day greenhouse trial. Error
bars are standard error of the mean. Treatments were a 1000 ppm Gibberellic acid solution (GA)
and deionized water (control)…………………………………………………………………...A4
Figure A.4. Cumulative germination rates of agronomic species during a 30-day greenhouse trial.
Error bars are standard error of the mean. Treatments were a 1000 ppm Gibberellic acid solution
(GA) and deionized water (control)……………………………………………………………..A4

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LIST OF TABLES
Table 2.1. Amendment composition for all treatments used for growth experiment ................... 24
Table 2.2. Select chemical and physical parameters of mine tailings, organic amendments, and
amended tailings treatments. ......................................................................................................... 26
Table 2.3. Select metal and metalloid concentrations (mg kg-1) of mine tailings and amendments
used for this study compared to CCME guidelines for agricultural and industrial uses............... 27
Table 2.4. Pseudoroegneria spicata and Festuca campestris shoot accumulation (mg kg-1) of
select metals and metalloids after 90 d growth in amended mine tailings.................................... 33
Table 3.1. Climate data from Kamloops A weather station (345 m in elevation and 8 km
northeast of the study site) including study years and long-term normals. .................................. 50
Table 3.2. List of plant species chosen for field experiment. ....................................................... 55
Table 3.3. Results of 3-way ANOVA looking at the effects of nurse plants (sage/no sage), seed
type (native/native with cover crop) and soil amendments (compost only/compost-ash mix) on
physical soil parameters of study plots at the Historic Afton Tailings Storage Facility............... 63
Table 3.4. Correlation matrix showing Pearson correlation statistics and P-values for
relationships between sage abundance parameters and physical soil parameters of study plots at
the Historic Afton Tailings Storage Facility. ................................................................................ 65
Table 3.5. List of species identified and mean relative cover on study plots (by factor) at the
Historic Afton Tailings Storage Facility. ...................................................................................... 67
Table 3.6. Results of 3-way ANOVA looking at the effects of nurse plants (sage/no sage), seed
type (cover crop/no cover crop) and soil amendments (compost only/compost+ash) on vegetation
parameters of study plots at the Historic Afton Tailings Storage Facility. ................................... 68
Table 3.7. Correlation matrix showing Pearson correlation statistics and P-values for
relationships between sagebrush abundance parameters and vegetation parameters of study plots
at the Historic Afton Tailings Storage Facility. ............................................................................ 70
Table A.1. Days to first germination (T0) by treatment for each of the study species………….A5
Table A.2. Mean days to 50% germination (T50) ± standard error for each of the study species
and two-sample t-test results comparing means between treatments…………………………...A6

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Table B.1. Elemental concentrations of experimental materials and federal soil quality
guidelines………………………………………………………………………………………..B1

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CHAPTER 1 – INTRODUCTION
Human activities such as urban development and conversion of land for agriculture and
industrialization have been ongoing for over a century in order to meet humankind’s current
societal and economic needs, but these activities have resulted in alteration to our natural habitats
and ecosystems. These land use changes are also contributing to global climate change by
disrupting the terrestrial carbon cycle (IPCC, 2014). Globally, extinction rates are estimated to be
100 to 1000 times higher than natural background rates (Ceballos et al., 2015; Thuiller, 2007)
and habitat alteration is suspected to be the leading cause (Barnosky et al., 2011). Such humaninduced rapid losses in biodiversity and natural habitats are threatening the global ecosystems
and the valuable ecosystem services which they provide (Dirzo and Raven, 2003; Mace et al.,
2012). By focusing on repairing natural habitats and ecosystems at the site level, the practice of
ecological restoration offers mitigation of these environmental problems.

THE IMPORTANCE OF GRASSLANDS
Grasslands are one of many of the Earth’s ecosystems experiencing environmental
pressures from land use change and global climate change. Conversion of grasslands to
agricultural crops, livestock pastures, urban areas, and industrial land continues to be
problematic as the human population rises and societies continue to develop. These unique
biomes – which cover almost 4 billion hectares (27%) of the earth’s surface (Costanza et al.,
1997) – are an important natural resource because they provide an array of important ecosystem
services such as wildlife habitat, animal forage, pollination, erosion protection and carbon
sequestration (Wilson, 2009). Though it is difficult to put a price on these precious benefits, a
recent study estimated the value of these ecosystem services to be over $900 billion (USD) per
year (Costanza et al., 1997). When grassland areas are converted to alternate land uses, not only
is the natural capital lost, but so are these important ecological functions – which play a vital role
in maintaining the health and well-being of the global ecosystem. Ecological restoration offers
hope in returning these degraded ecosystems to their pre-disturbed condition (Bradshaw, 1987a).
The semiarid grasslands of British Columbia (B.C.) cover less than 1% of the province’s
total land area yet are home to over 30% of its species at risk (B.C. Conservation Data Centre,
2017), making them one of Canada’s most valued hotspots for biodiversity (Grassland

2

Conservation Council of BC, 2017). The grasslands of southern interior B.C. are considered a
northern extension of the Great Basin region that spans from central Oregon through
Washington, Idaho and Montana, referred to as Palouse Prairie (Shorthouse, 2010). They are
currently in decline due to factors such as urban sprawl, industrial development, agriculture,
over-grazing, tree encroachment and invasive plants. The grasslands across the region have
experienced an extensive history of livestock grazing which has altered natural plant
communities (Huber-Sannwald and Pyke, 2005; van Ryswyk et al., 1966; Wilson, 2009). These
areas also coincide with valuable underground mineral resources thus are attractive areas for
mineral exploration and mining. Generally, semiarid grasslands are extremely sensitive to
disturbances because seedling establishment and soil development are limited by the hot and dry
climate characteristic of grasslands (Jing et al., 2014; Munson and Lauenroth, 2012). As
alteration of these fragile grassland habitats continues, efforts of conservation and ecological
restoration are gaining immense importance.

THE MINING INDUSTRY AND ITS IMPACTS ON THE ENVIRONMENT
With the exponential rise in human population, industrialization, economic development
and technological advancements, the global demand for minerals is ever-increasing. Canada is a
global leader in mineral and metals production. The mining industry is a significant component
of Canada’s society and economy, employing over 350,000 people across the country and
retaining the largest proportion of aboriginal workers out of any private industry (Mining
Association of Canada, 2016). In 2015, Canada’s mining industry contributed $56 billion (3.4%)
to the total GDP (Mining Association of Canada, 2016). With an abundance of underground
mineral resources, British Columbia is one of Canada’s top four metal producers and the industry
was recently valued at $5.9 billion per year (Mining Association of Canada, 2016). There are
currently a total of 14 major metal and coal mines operating in BC, with several others proposed
or undergoing development (Mining Association of British Columbia, 2017).
As a resource-driven economy, it is important for Canada to encourage environmental
protection and sustainability in the mining industry if it is to maintain its status as a global
mining leader. Although the mining industry is both economically and socially beneficial, the
activities involved in mineral extraction, particularly during open pit and surface mining, can
cause enormous environmental damage to terrestrial ecosystems (Shrestha and Lal, 2011; Ussiri

3

and Lal, 2005). This is because during the mining process 1) removal of natural vegetation,
topsoil, overburden (unconsolidated material), and bedrock is required prior to accessing the
desired below-ground mineral resources and 2) the waste materials (e.g. tailings, waste rock) are
often deposited at the surface, in immense quantities, over large areas of the landscape, which
damages or destroys pre-existing vegetation and soils. In many cases, these landscape level
disturbances result in long term impairment of the pre-existing ecosystem functions (Bradshaw,
1997). The ecological consequences of mining include habitat degradation, losses in biodiversity,
alteration of natural landscapes, and changes in hydrologic patterns (Sheoran et al., 2010;
Shrestha and Lal, 2011). Further, the loss in vegetation and soils leads to a reduction in the
natural capacity of terrestrial ecosystems to sequester atmospheric carbon and regulate the global
climate (Shrestha and Lal, 2006).
The disturbances caused by mining generally include tailings storage facilities, waste
rock dumps, barren stripped areas, roadsides and degraded land used for industrial facilities. It is
estimated that over 0.4 million hectares of land has been disturbed from mining in Canada
(Gardner et al., 2010). In BC, approximately 0.05% (~45,000 ha) of the land base has been
altered by mining (BC Technical and Research Committee on Reclamation, 2017). British
Columbia’s mining industry has committed to prioritizing environmental protection and
sustainability throughout all phases of the mine cycle. Reclamation is the final phase of mining
and involves returning the mined land into a useful and productive state. The BC Mines Act
provides legislation regarding how mining activities are carried out and includes guidelines for
reclamation (Government of British Columbia, Ministry of Energy, 2008).

MINE RECLAMATION
If left to natural processes, mine sites can take hundreds of years to recover from the
environmental damage inflicted during the mining process (Bradshaw, 1987a). Ecological
restoration is the process of assisting the recovery of disturbed ecosystems to their original state
(Bradshaw, 1997). Restoration practitioners strive to achieve similar structure and functions as
the pre-existing ecosystems (Palmer et al., 2006). Reclamation is more concerned with achieving
a socially acceptable new use for the land that does not necessarily coincide with its prior
ecological state (Bradshaw, 1997), a common example being the conversion of mined land to
livestock pasture, agricultural crops or wildlife habitat (Akala and Lal, 2001; Tian et al., 2009;

4

Wood et al., 1995). This type of conventional mine reclamation is becoming less desirable as
these ‘surface-mine grasslands’ tend to lack the diversity, structure and function of natural
ecosystems (Brothers, 1990; Viall et al., 2014; Wu et al., 2011). More recently, restoration of
mine sites to their previous, natural habitat in order to enhance biodiversity and reinstate natural
ecosystem services is becoming the standard (Lesica and Allendorf, 1999). It is now widely
recognized that re-establishing biodiversity is the key to achieving restoration success, as diverse
ecological communities are more resilient to environmental disturbances (Ives and Cardinale,
2004). To accomplish this, practitioners are urged to use ecological theory and principles as
restoration tools to mimic natural processes of ecosystem development during restoration efforts
(Bradshaw, 1997).
For mine restoration to be successful, natural soil processes need to be initiated and a
self-sustainable, native vegetative cover needs to be established. The starting point for any land
restoration project is the soil, or the degraded parent material left behind that has potential to
develop into a soil over time (Bradshaw, 1987a). Plants and soils interact to create a positive
feedback loop that is the primary driving force of soil development (Brady, 1990). Plants assist
in soil development by taking up nutrients from deep soil layers and redistributing them at the
surface as organic matter. The organic carbon of which they are comprised was fixed from the
atmosphere and is the food source for soil microbes and microfauna which facilitate
decomposition, nutrient cycling and the development of soil aggregates (Bradshaw, 1997). Plants
also protect soils from erosion and allow for the accumulation of windborne particles (Bradshaw,
1997). This constant cycle leads to the maturing of soils and the development of distinct soil
horizons (Brady, 1990). The initiation of these soil development processes on degraded mine
sites depends on the initial capacity of the soils to support plant life (Shrestha and Lal, 2006).
The major problems of mine soils are their poor physical and chemical properties that
limit plant establishment and growth (Bradshaw, 1997; Sheoran et al., 2010). For example,
tailings, which are the waste by-product of ore processing, are low in organic matter and
nutrients (Gardner et al., 2010) and have elevated levels of certain heavy metals (Hayes et al.,
2009). These materials are often prone to compaction from heavy equipment (Ussiri and Lal,
2005) and have poor water retaining capacity (Cele and Maboeta, 2016). It is not uncommon for
pH (Solís-Dominguez et al., 2012) and salinity (Bai et al., 2017) levels to be out of the ordinary
which can exuberate issues with metal toxicity (Bolan et al., 2014). Also, microbial populations

5

in tailings are either severely altered or virtually non-existent (Pepper et al., 2012). In arid and
semiarid environments, additional challenges arise from tailings being prone to wind and water
erosion (Mendez and Maier, 2007). The immediate goal of tailings reclamation is to establish a
vegetative cover to stabilize the loose material in place in a process known as phytostabilization
(Mendez and Maier, 2007; Neuman and Ford, 2006). To enhance reclamation success on mine
sites, practitioners can use a variety of site preparation techniques derived from ecological theory
and principles (Bradshaw, 1997).

Soil Amendments
In mine restoration, there are four fundamental challenges of site preparation to
overcome: 1) restoring soil physical structure, 2) retaining soil moisture, 3) providing plant
nutrients, and 4) reducing phytotoxicity (Bradshaw, 1987a; Piorkowski et al., 2015). Soil
amendments are commonly used in revegetation projects to mitigate these ecological
shortcomings. Traditional reclamation involved the application of the topsoil stockpiled during
mining operations, but this material is often limiting, so soil amendments need to be imported
from external sources.
Commonly used soil amendments include inorganic fertilizers, organic amendments and
liming amendments. Long term success with chemical fertilizers is low due to issues with
leaching and the need for constant re-application to sustain plant nutrient needs (Gardner et al.,
2010). Since the mine soils are low in organic matter, the key is to incorporate nutrient-rich
organic materials with enough of a carbon source to initiate microbial activity and nutrient
cycling. These materials are called organic amendments and include municipal compost, wood
chips, straw mulch, paper/pulp and municipal sewage sludge. Liming amendments are primarily
used to reduce soil toxicity by neutralizing acidic soils and immobilizing heavy metals (Brown et
al., 2007; Piorkowski et al., 2015). Since each soil amendment possesses its own unique
characteristics, plant performance is often optimized when a blend of amendments is utilized
rather than a single amendment (Piorkowski et al., 2015). Revegetation success is often greater
when soil amendments are used prior to seeding. For this practice to be economical, amendments
must be imported from local sources because the cost of transportation is high and most projects
require large volumes to cover the vast area being revegetated. Since soil amendments can be
waste by-products of various industries (e.g. pulp and saw mills, sewage treatment plants,

6

composting facilities), the use of these products for mine reclamation can be mutually beneficial
for both the waste generator and the mining operation.

Seeding
Since dispersal distance of native grassland species from surrounding areas is limited
(Ejrnæs et al., 2006), the establishment of a vegetative cover on mine sites is achieved by
seeding and/or transplanting. The techniques for seeding include broadcast seeding, hydroseeding, drill seeding and hand seeding. Seeding gives restoration practitioners the benefit of
choosing which species are introduced to a site. A long-standing ecological theory suggests that
initial floristic composition determines the trajectory of which plant communities develop and
change over time, and the type of inter-specific interactions that will take place (Egler, 1954).
Furthermore, there is evidence that early-growing species can exert “priority effects”
(competitive advantages) that prevent the establishment of slower-growing perennial species
(Grman and Suding, 2010; Plückers et al., 2013). When taking this theory into consideration,
careful selection of appropriate species is important because the composition of the initial seed
mix can determine the outcome of restoration (Larson et al., 2011; Munson and Lauenroth,
2012).
Conventional reclamation often involves planting non-native or agronomic crops to
achieve erosion control and forage value in the short-term. From an economic standpoint,
agronomic species are desirable because they are inexpensive and available in large quantities
from several suppliers. They also tend to establish very rapidly on poor sites, allowing for less
intensive site preparation and quick return of environmental and economic benefits (Skousen and
Venable, 2008; Wu et al., 2011). However, research has shown that these species are extremely
competitive and can prevent native species from establishing (Dormaar et al., 1995; Hagen et al.,
2014). Recently, it has been argued that agronomics can alter the trajectory of natural succession
by preventing the colonization of native species (Davis et al., 2005). These agronomic systems
are also known for their low species diversity (Dormaar et al., 1995). In this sense, seeding with
agronomics can prevent a site from reaching its full ecological potential. However, some work
has shown that given adequate time, native species can, in fact, colonize a site that was initially
seeded with agronomics (Skousen and Venable, 2008). This occurred when sites were seeded
with annual or biennial ‘cover crops’ which are often used to provide quick cover and temporary

7

erosion control while facilitating the establishment of native species. This discrepancy in the
literature merits further investigation into the use of agronomic species for mine restoration.
More recently, attention is shifting towards the use of native species in restoration
projects for many reasons (Burton and Burton, 2002; Godefroid et al., 2011; Kiehl et al., 2010).
Firstly, the introduction of native species is essential if pre-existing ecosystems are to be
reconstructed and the process of natural succession is to be initiated (Godefroid et al., 2011).
Secondly, restoration with native species is often a more desirable land-use objective for First
Nations groups, who are often primary stakeholders of lands disturbed by mining operations.
Finally, native plant communities tend to be more diverse and offer greater ecosystem services
compared to non-native communities (Bradshaw, 1987a; Dormaar et al., 1995), although this is
not always the case in restoration (Ross, 2004). Unlike agronomics, establishment success of
native species is often limited on degraded sites (Burton et al., 2006; Drozdowski et al., 2012).
Additionally, native seed is difficult to obtain in bulk quantities due to a lack of suppliers, and so
the market prices can be high (Burton and Burton, 2002). Also, native species do not establish
well in hydro-seeding mixtures which are often used in reclamation as an economical means of
applying seed to challenging terrain (Oliveira et al., 2013, 2012).

Phytostabilization
Controlling the dispersion of dust is a central challenge for mines operating in arid and
semiarid regions (Mendez and Maier, 2007). Airborne dust from mine lands such as tailings
impoundments and waste rock dumps can contain heavy metal and metalloid contaminants that
cause negative impacts to human health and surrounding ecosystems (EPA, 2016). As such,
mining companies are required by law to implement on-site dust control measures to mitigate
these negative effects. Industrial chemical tackifiers are an effective solution for controlling dust
in the short term, but do not provide a sustainable long term solution because they are expensive
and tend to degrade with time without repeated application (Mendez and Maier, 2007).
Phytostabilization is a remediation technique aimed at restoring vegetative cover on barren land
as a means to control dust and stabilize contaminants belowground (Mendez and Maier, 2007;
Neuman and Ford, 2006). Appropriate species for phytostabilization are native species that 1) are
adapted the regional climate, 2) tolerate increased levels of heavy metals and metalloids, and 3)
minimize shoot uptake while maximizing root uptake of contaminants (Mendez and Maier,

8

2007). Site specific research of species suitability for phytostabilization is needed to add to the
growing body of literature (Solís-Dominguez et al., 2012).

Facilitation and Nurse Plants
For ecological restoration to be successful, it is essential to understand what natural
processes take place, what components make up a given ecosystem in its early successional
phase, and what limits these processes and components from developing over time (Bradshaw,
1987b). Species interactions are a widely researched topic in terrestrial and aquatic ecology.
Species interactions include negative (competition) and positive (facilitation) inter-species
interactions, and interacting species often concurrently exert both negative and positive effects
on one another (Callaway and Walker, 1997). Facilitation results when the net effect of such
interactions is positive. Until recently, ecologists have focussed their research efforts on negative
interactions, and theorized that competition is the driving force of ecological succession
(Cavieres and Badano, 2009; Grime, 1973; Tilman, 1982). However, research conducted within
the past two decades suggests that facilitation also plays an important role in shaping population
and community dynamics in both terrestrial and marine environments (Bertness and Callaway,
1994; Bruno et al., 2003). The concept of facilitation encompasses mutualistic interspecies
relationships that are both facultative and obligate, and occurs when there is either a direct or
indirect positive interaction between associated organisms that are present within the same space
and time (Bruno et al., 2003). One example of a positive species interaction occurs during
primary succession of glacial recession zones, where edaphic conditions are enhanced by pioneer
plants and trees, which, in turn, enables late successional species to successfully colonize the
area (Crocker and Major, 1955). Another well-documented example of facilitation in terrestrial
environments is the symbiosis between arbuscular mycorrhizal fungi and vascular plants
(Quilambo, 2003), a mutualistic interaction involving nutrient and moisture exchange that
empowers plant beneficiaries to exist beyond their fundamental niche (Bruno et al., 2003). The
practice of revegetating former mine lands with native species requires expanding the
fundamental niche of the target native plant community, thus, applying the theory of facilitation
into reclamation practices may be beneficial in establishing native plant communities on former
mine sites.

9

It is theorized that the degree of facilitation increases with abiotic stress (Bertness and
Callaway, 1994), which explains why several examples of facilitation have been documented in
harsh environments, such as those which experience arid or semiarid climates (Padilla and
Pugnaire, 2006). Numerous studies have demonstrated that ‘nurse plants’ play an important role
in such environments (Claus Holzapfel and Mahall, 1999; Maestre et al., 2003; Pugnaire et al.,
1996). Nurse plants facilitate the growth of neighboring plants by modifying the local abiotic and
biotic environment, and the degree of such beneficial effects depends on several factors,
including nurse plant life history stage and root physiology (Callaway and Walker, 1997). In arid
and semiarid environments, certain shrubs exert a ‘nurse effect’ on associated grasses and other
plants, by shading out solar radiation, which in turn reduces local soil evaporation rates, soil
temperature, and plant tissue damage, leading to noticeably enhanced growing conditions for the
emerging understory plant community (Padilla and Pugnaire, 2006). Some studies have shown
that plant community diversity is greater under nurse plants than in the open (Cavieres and
Badano, 2009; Franco and Nobel, 1989). For example Pugnaire et al. (1996) reported improved
understory production and plant species diversity under the canopies of a leguminous shrub in a
semiarid region in Spain, and that the facilitative effects increased with shrub age and size. Nurse
plants can also augment local soil moisture by drawing water from deep soil layers to the surface
through a process known as ‘hydraulic lifting’ (Padilla and Pugnaire, 2006). This phenomenon
has been observed for Artemesia tridentata (big sagebrush) shrubs (Cardon et al., 2013; Richards
and Caldwell, 1987), which are common in B.C.’s semiarid grasslands. Some studies have also
reported enhanced soil nitrogen levels under A. tridentata shrubs (Burke et al., 1989; Cardon et
al., 2013). Although one study by Huber-Sannwald and Pyke (2005), conducted in a semiarid
rangeland, showed minimal success of a target bunchgrass community under adult A. tridentata
shrubs, there is potential for these shrubs to act as a nurse plant in mine reclamation settings,
especially considering the establishment success of exhibited by Booth et al., (2003) on
reclaimed mine lands.

Cover Crops
Another method of facilitating target plant community establishment is through the use of
cover crops. Cover crops are generally used in agricultural settings and in various restoration
projects to mitigate soil erosion and prevent the establishment of weedy species, but can also be

10

used to enhance abiotic and biotic conditions for target plant communities (Espeland and
Perkins, 2013). A typical cover crop is made up of agronomic species and often includes annual
or short-lived perennial grasses and legumes. Together these plants effectively provide a variety
of functions including soil stabilization and improved soil fertility through soil organic matter
inputs and atmospheric N-fixation (Espeland and Perkins, 2013; Moro et al., 1997). One would
suspect that competition from agronomic cover crop species may inhibit the development of the
target community, but research shows that this is less likely in limiting or stressful environments
(Espeland and Perkins, 2013). In stressful environments, cover crops can ameliorate harsh
abiotic conditions, which allows for increased success of neighboring target species (Maestre et
al., 2009, 2003). Based on these results, there is potential to utilize agronomic cover crops in
mine reclamation projects to facilitate the establishment of target native plant communities.

THESIS RESEARCH OBJECTIVES
This study delves into contemporary ecological theory in order to address the question of
whether facilitation – using nurse plants and cover crops – can be applied in a mine reclamation
setting to improve native grassland recovery at the Historic Afton Tailings Storage Facility
(TSF) near Kamloops, B.C. In doing so, this study will also look at the suitability of locally
available soil amendments for reclamation at the TSF. To address these questions, I have
conducted a two-part study involving both a greenhouse (Chapter 2) and a field (Chapter 3)
component. The objectives of the greenhouse study are twofold: 1) to investigate the suitability
of two native, semiarid bunchgrasses (Pseudoroegneria spicata and Festuca campestris) for
phytostabilization of mine tailings, and 2) to assess the optimum ratio of soil amendments for
establishment of these species. The objectives of the field study are threefold: 1) to assess the
effects of Artemisia tridentata nurse plants on the abiotic environment and plant community
establishment during early restoration, 2) to examine whether agronomic cover crops facilitate or
impede native grassland species establishment, and 3) to test the suitability of soil amendments
for mine tailings rehabilitation. Also included is an Appendix with additional results from a seed
germination trial conducted in the greenhouse (Appendix A) and laboratory analytical chemistry
results for the experimental materials (tailings and soil amendments) (Appendix B). The results
of this thesis will contribute to the body of knowledge regarding facilitation in semiarid

11

environments and will be of benefit to restoration ecology scientists and practitioners conducting
reclamation work within B.C.’s semiarid grasslands and similar environments.

12

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Sheoran, V., Sheoran, A.S., Poonia, P., 2010. Soil reclamation of abandoned mine land by
revegetation : a review. Int. J. Soil, Sediment Water 3, 1–21.
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Ontario, in: Shorthouse, J. (Ed.), Arthropods of Canadian Grasslands (Volume 1): Ecology
and Interactions in Grassland Habitats. Biological Survey of Canada, pp. 83–103.
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Shrestha, R.K., Lal, R., 2011. Changes in physical and chemical properties of soil after surface
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Shrestha, R.K., Lal, R., 2006. Ecosystem carbon budgeting and soil carbon sequestration in
reclaimed mine soil. Environ. Int. 32, 781–796. doi:10.1016/j.envint.2006.05.001
Skousen, J.G., Venable, C.L., 2008. Establishing native plants on newly-constructed and olderreclaimed sites along West Virginia highways. L. Degrad. Dev. 19, 388–396.

17

doi:10.1002/ldr.846
Solís-Dominguez, F.A., White, S.A., Hutter, T.B., Amistadi, M.K., Root, R.A., Chorover, J.,
Maier, R.M., 2012. Response of key soil parameters during compost-assisted
phytostabilization in extremely acidic tailings: Effect of plant species. Environ. Sci.
Technol. 46, 1019–1027. doi:10.1021/es202846n
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sequestration resulting from long-term application of biosolids for land reclamation. J.
Environ. Qual. 38, 61. doi:10.2134/jeq2007.0471
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Princeton, USA.
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Plant Sci. 24, 151–165. doi:10.1080/07352680591002147
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of some grasslands at different elevations in British Columbia. Can. J. Plant Sci. 46, 35–50.
doi:10.4141/cjps66-005
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road reclamation on soil biology and plant community composition. Restor. Ecol. 22, 625–
632. doi:10.1111/rec.12115
Wilson, S., 2009. The Value of BC ’s Grasslands : Exploring Ecosystem Values and Incentives
for Conservation. Grasslands Conservation Council of British Columbia, Kamloops, British
Columbia.
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on New Mexico Reclaimed Mine Land. J. Range Manag. 48, 431. doi:10.2307/4002247
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composite/consolidated oil sands tailings, in: Proceedings - Tailings and Mine Waste 2011.
Vancouver, BC.

18

CHAPTER 2 – GROWTH RESPONSE AND METALS UPTAKE OF
NATIVE BUNCHGRASSES DURING ORGANIC AMENDMENTASSISTED PHYTOSTABILIZATION OF ALKALINE MINE TAILINGS

INTRODUCTION
As of 2017, there were 14 major metal and coal mines operating in British Columbia
(B.C.), with several more either undergoing care and maintenance or awaiting approval from the
environmental assessment process (Mining Association of British Columbia, 2017). Some of
these projects are located within the interior semi-arid grasslands, which are a unique ecoregion
characterized by hot, dry summers and minimal annual precipitation (Shorthouse, 2010). Tailings
management is one of several challenges faced by mines operating within these grasslands and
other dry environments. If left barren, dust from mine waste sites can spread over long distances
through eolian dispersion and water erosion, posing a risk to human and environmental health
(Mendez and Maier, 2007). Fine particulate waste materials (e.g. tailings, waste rock) that are
stored on mine sites are often high in toxic metals and other contaminants which can cause
adverse human health effects including respiratory disease, heart failure, and lung cancer, and
also impact the surrounding environment by altering water chemistry and causing soil
contamination (EPA, 2016). Conventional remediation methods for controlling tailings dust
include chemical (e.g. industrial tackifiers) and physical (e.g. waste rock, gravel, or clay
capping) stabilization, however, these methods are costly and do not provide a long term solution
(Mendez and Maier, 2007). Phytostabilization is an emerging technology which involves
promoting vegetation growth on barren mine lands to control erosion and stabilize metals
belowground, and may be a more sustainable alternative compared to conventional remediation
techniques.
The goal of phytostabilization is to create a long-term vegetative cap in order to limit the
movement of harmful metal contaminants from mine sites. Once established, the aboveground
portion of the vegetation (canopy) acts to reduce wind erosion, whereas the belowground portion
(roots) limits water erosion and immobilizes metals in the rhizosphere. The belowground
processes involved in phytostabilization include precipitation of metals by bacterial and root
surfaces, precipitation of metals by bacterial and root secretions, bacterial uptake of metals, and
root uptake of metals (Mendez and Maier, 2007). Phytostabilization differs from phytoextraction

19

(another phytoremediation technology) in that the aim is to reduce metal bioavailability and the
risk of metals entering the food chain by minimizing shoot uptake and sequestrating metals
belowground via plant roots and exudates. Contrarily, phytoextraction involves remediating
contaminated materials by promoting hyperaccumulation of metals in shoots and requires
removal of the toxic plant biomass from site which can be laborious and costly (Bolan et al.,
2014). As mandated by federal and provincial regulations, reclamation of land disturbed from
mining is the responsibility of the mining company (Government of British Columbia, Ministry
of Energy, 2008); if successfully implemented, phytostabilization of mine sites within B.C.’s
semiarid grasslands can help mining companies meet reclamation targets, while initiating
ecological restoration and providing long term environmental and socioeconomic benefits
(Costanza et al., 1997; Wilson, 2009).
The starting point for any revegetation project is the soil, or the degraded material left
over from disturbance that has potential to develop into a soil over time (Bradshaw 1987, 1997).
Mine tailings are the by-product of ore processing and consist of fine particulate matter which
often lacks the physical, chemical, and biological properties of a productive soil (Gardner et al.,
2012, 2010; Pepper et al., 2013), and therefore, are not a suitable growth medium for most
terrestrial plants. In general, tailings are high in toxic metals such as arsenic (As), cadmium (Cd),
chromium (Cr), copper (Cu), mercury (Hg), lead (Pb), and zinc (Zn), which, contrary to organic
contaminants, can persist in soils for long periods of time (Bolan et al., 2014). The mobility and
bioavailability of most metals (e.g., Zn, Cu) increases with soil acidity, with a few exceptions
such as molybdenum (Mo) and aluminum (Al) which can become available in alkaline
conditions (Delhaize and Ryan, 1995; EPA, 2007). In addition to metal toxicity, extreme pH
levels, altered soil microbial communities, limited pore space, low amounts of plant nutrients,
and poor water retention make up the factors limiting vegetation establishment success on mine
tailings (Brown et al., 2003; Pepper et al., 2012; Sheoran et al., 2010). Soil amendments are
commonly used in revegetation projects to mitigate these ecological shortcomings and have been
proven to be successful in several scenarios (Brown et al., 2007; Drozdowski et al., 2012;
Gardner et al., 2010; Shrestha et al., 2009).
Soil amendments include organic amendments (e.g. municipal compost, sewage sludge,
wood chips) and liming agents (e.g. wood ash, fly ash). Generally, organic amendments are used
to enhance plant growth by providing nutrients and improving soil physical properties, whereas

20

liming amendments are used to reduce phytotoxicity by neutralizing acidic soils (EPA, 2007),
although, these effects can overlap. Manipulating soil properties such as pH and organic matter
with soil amendments can influence the bioavailability of soil-borne metals and potentially
mitigate any environmental or health risks caused by toxic metals (Bolan et al., 2014). In a
greenhouse investigation, Solís-Dominguez et al. (2012) used compost to increase the pH of
acidic iron mine tailings, which reduced metal bioavailability and made the tailings substrate
more suitable for plant growth. In a review study, Ussiri and Lal (2005) reported improved
physical (bulk density, soil aggregation, and water-holding capacity) and chemical (pH and
electrical conductivity) properties when coal mine soils were amended with fly ash (a by-product
of coal combustion). Furthermore, in a greenhouse experiment, Piorkowski et al. (2015) found a
positive synergistic effect on plant performance when a blend of biosolids and compost was
utilized. Although soil amendments can be the answer to poor productivity on mine sites,
questions remain regarding the economic cost, particularly relating to the availability and the
transport of large volumes required for reclamation at the landscape level. As such, investigation
into sourcing economically and ecologically viable, locally available materials can be beneficial
for mine operations conducting phytostabilization and other reclamation projects.
Revegetation can begin once site preparation and soil amelioration is complete.
Revegetation in arid and semiarid environments is exceptionally challenging due to a variety of
environmental factors, such as reduced moisture availability and high temperatures, which can
limit seed germination and establishment success (Munson and Lauenroth, 2012; Padilla and
Pugnaire, 2006; Simmers and Galatowitsch, 2010). Traditionally, non-native species have been
utilized for mine reclamation because of their tendency to successfully germinate and establish in
harsh environments, and also because of their low cost and ease of availability in large quantities
(Burton and Burton, 2002; Oliveira et al., 2012; Skousen and Venable, 2008). Although, more
recently, the disadvantages of using non-native species are becoming increasingly recognized.
For example, evidence suggests that, due to their competitive nature, non-native species can alter
the trajectory of ecological succession by preventing colonization and establishment of native
species (Davis et al., 2005; Grman and Suding, 2010). In recent decades, attention has shifted
towards using native plant species for reclamation because of their potential to enhance
ecosystem health and function, as well as provide socioeconomic benefits (Burton and Burton,
2002; Kiehl et al., 2010; Skousen and Venable, 2008). Researchers have explored the suitability

21

of several plant species for phytostabilization across a wide range of environments, but we still
remain in the information gathering stage regarding species-specific responses to mine tailings
(Solís-Dominguez et al., 2012). It is known that candidate species must minimize accumulation
of metals in their shoots and tolerate elevated metals, high salinity, and abnormal pH levels
(Mendez and Maier, 2007; Solís-Dominguez et al., 2012). The suitability of plant species can be
determined by calculating the “translocation factor (TF)” which is the ratio of elemental
concentration of shoots versus roots (Mendez and Maier, 2008). Species with TF values of < 1
are optimal for phytostabilization while those which have values of >1 are more suitable for
phytoextraction. Species that are adapted to the local climate are ideal. and so native species are
preferred over introduced species (Mendez and Maier, 2008; Neuman and Ford, 2006).
Tremendous merit can be derived from investigating the suitability of native species for
phytostabilization.
Both Pseudoroegneria spicata (bluebunch wheatgrass) and Festuca campestris (rough
fescue) are bunchgrass species with high forage value, and are native to B.C.’s interior semiarid
grasslands (Government of British Columbia, 1991; USDA, 2016). Pseudoroegneria spicata
tends to occupy low elevation areas and can generally tolerate drier environments compared to F.
campestris which is predominant at higher elevations and is less suited to drought conditions
(Dobb and Burton, 2013; Shorthouse, 2010). Both of these grasses are potential candidates for
phytostabilization within the interior semiarid grasslands, but little is known regarding their
tolerance to soil metal contaminants and their ability to grow on amended mine spoils (e.g.,
Thorne et al., 1998). The tailings discharged from the historic Afton copper and gold mine (near
Kamloops, B.C.) are currently undergoing reclamation, and dust mitigation was one of the
primary objectives of the mining company (KGHM International Ltd.) that held the mineral title
at the time of this study. The historic Afton tailings are moderately alkaline (pH >8.5), high in
copper (600 mg kg-1) and molybdenum (10.5 mg kg-1), and influenced by a semiarid climate,
which provides us with a unique opportunity to conduct phytostabilization research using locally
available soil amendments and native grassland species.
This study summarizes the results of a greenhouse study which was designed to 1)
evaluate three locally available organic amendments (municipal compost, wood ash and wood
chips) in terms of plant growth response on the historic Afton mine tailings, and 2) assess
whether Pseudoroegneria spicata and Festuca campestris are suitable candidates for

22

phytostabilization of these tailings in terms of growth response and metals uptake. Here the aim
is to couple phytostabilzation techniques with native grassland restoration practices in order to
achieve both short and long-term benefits from revegetation of the historic Afton tailings and
similar mine sites.

MATERIALS & METHODS
Mine Tailings and Amendment Analysis
Bulk tailings samples were collected from the Historic Afton Tailings Storage Facility
(TSF), approximately 15 km west of Kamloops, British Columbia (50° 39’ N, 120° 32’ W;
elevation 700 m) (Figure 2.1). The compost amendment was produced from municipal yard
waste at the City of Kamloops Cinnamon Ridge compost facility, the ash was sourced from the
Domtar pulp mill (Kamloops, BC) and is a byproduct of waste wood (commonly referred to as
‘hog fuel’ and derived from softwood) incineration, and the wood chips were waste produced
from a local veneer/plywood factory. The amendments were available within a 30 km radius of
the TSF (Figure 2.1), making the materials economically viable options for reclamation.
Samples of tailings and amendments (3 of each) were passed through a 2 mm sieve and
analyzed for pH and electrical conductivity (EC) using a handheld electrode device (Hanna
Combo HI-98130, Hanna Instruments Inc., Woonsocket, RI, USA) in a 2:1 (soil: deionized
water, by mass) solution reacted for 1 h (modified from Hayes et al. 2009). Soil texture was
classified for tailings samples only, using the pipet sedimentation method (Hayes et al. 2009).
Particle size distribution of the amendments was determined using sieves with mesh sizes
ranging from 0.1 to 16 mm. Organic matter content was determined for all samples by loss on
ignition (550 °C for 6 h) (Hagen et al., 2014). Gravimetric water holding capacity (WHC) was
determined using the methods outlined by Haney and Haney (2010). Subsamples of the tailings
and amendments were sent to the British Columbia Ministry of Environment Analytical
Laboratory (BCMEAL) (Victoria, BC) for analysis of total carbon (C), total nitrogen (N) and
metal concentration including the elements aluminum (Al), arsenic (As), cadmium (Cd), cobalt
(Co), chromium (Cr), copper (Cu), iron (Fe), mercury (Hg), molybdenum (Mo), nickel (Ni), lead
(Pb), and zinc (Zn).

23

Figure 2.1. Map of study site at the Historic Afton Tailings Storage Facility, 15 km west of Kamloops,
British Columbia. The red marker indicates the location of the tailings site. Green pins indicate the
locations from which the soil amendments were obtained. Compost was from the City of Kamloops
composting facility, wood ash was from the Domtar Pulp Mill, and wood chips were from a local
veneer/plywood factory.

Greenhouse Experiment
The greenhouse experiment was conducted from January to March 2016 at the Thompson
Rivers University Research Greenhouse in Kamloops, B.C. The experiment was designed to
investigate the effects of compost and ash amendments on native bunchgrass growth, and to
evaluate the suitability of the selected plant species for phytostabilization of the TSF. Two
representative forage bunchgrass species of the interior semiarid grasslands were selected using
the ‘species objective’ filters in the British Columbia Rangeland Seeding Manual (Dobb and
Burton, 2013). Pseudoroegneria spicata was chosen primarily for its drought tolerance while
Festuca campestris was selected for its tendency to occur naturally at similar elevations to the
study site. A total of 13 ash-compost combinations ranging from 0-100% (w/w) of compost and
wood ash, and 0-10% (w/w) of wood chips were evaluated using a randomized complete block
design with 10 replicates (Figure 2.3). Three subcategories of treatments were selected for
further analysis: ‘ash’ (100% ash), ‘compost’ (100% compost), and blend (40% ash, 50%

24

compost, 10% wood chips). A separate germination trial was conducted to determine seed
viability and germination rates (see Appendix A).
The growth experiment was conducted under controlled conditions (natural and artificial
light: day/night 18 h/6 h; temperature: day/night 21 °C /15 °C; humidity 50-60%) in the research
greenhouse. Two-litre nursery pots with drainage (15 cm top diameter × 14 cm height × 14 cm
bottom diameter) were filled with 500 g of tailings and amended with 150 g (a field equivalent to
150 Mg ha-1) of ash-compost-wood chip mixtures (Table 2.1). The tailings-amendment mixtures
were combined in bulk batches and mixed by hand. Pseudoroegneria spicata and Festuca
campestris seeds (obtained from Pickseed Canada Inc., Abbottsford, B.C.) were sown at a
density of 15 seeds per pot at a depth of approximately 0.5 cm. Pots were watered evenly on
every second day using a garden hose fitted with a perforated spout. Plant root and shoot tissues
were harvested 90 d after seeds were sown. Prior to harvesting, final levels of germination (i.e.
seedling emergence) were determined and shoot heights were measured (in natural repose).

Table 2.1. Amendment composition for all treatments used for growth experiment

Treatment
1 (ash)
2
3
4
5
6
7 (blend)
8
9
10
11
12 (compost)
13 (control)

Wood Ash
(%)
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
0%
0%

Compost Wood chips
(%)
(%)
0%
0%
0%
10%
10%
10%
20%
10%
30%
10%
40%
10%
50%
10%
60%
10%
70%
10%
80%
10%
90%
10%
100%
0%
0%
0%

Field
application rate
(Mg/ha)
150
150
150
150
150
150
150
150
150
150
150
150
0

25

Figure 2.2. View of randomized complete block design used for greenhouse growth trial.

Bunchgrass shoots were clipped at the soil surface and roots were retrieved from the
amended tailings substrate. Plant tissue samples were washed and dried (70 °C for 48 h), then
weighed on an analytical scale to determine root and shoot biomass. Three composite biomass
samples (roots and shoots) were prepared from the amendment treatment subcategories (‘ash’,
‘compost’, and ‘blend’) for analysis of plant tissue elemental concentration by the BCMEAL.
Seedling emergence rates, plant biomass, and tissue metal content data were analyzed in
R version 3.2.3 “Wooden Christmas-Tree” (The R Foundation for Statistical Computing). All
data were checked for normality using boxplots and residual plots. Homogeneity of variance was
assessed using the Fligner-Killeen test, and when necessary, data were transformed using a
natural logarithm or a square root function. Significant differences between species were
determined using the Welch’s two sample t-test. One-way and two-way analysis of variance
(ANOVA) tests were employed to find significant differences between treatment means.
Analysis of covariance (ANCOVA) was employed to control for seedling density when assessing
plant productivity metrics. Treatments were grouped and ranked using Tukey’s HSD test (P <
0.05).

RESULTS
Mine Tailings and Amendment Characteristics
Soil texture analysis revealed that the historic Afton tailings had a sandy clay loam
texture (52.9% sand, 26.5% silt, and 20.6% clay). The gravimetric WHC of the unamended
tailings was relatively high compared to the soil amendments, and decreased when amendments

26

were added (Table 2.2). The tailings were also characterized by a moderately alkaline pH and
low amounts of organic matter, total carbon, total nitrogen and phosphorus. Electrical
conductivity remained below the threshold of 4 dS m-1 at which plant growth is inhibited
(Drozdowski et al. 2012). Analysis of tailings for metals revealed high amounts of Cr, Cu, Mo,
and Ni (Table 2.3). Of these metals, Cu, Cr, and Ni exceeded the CCME guidelines for industrial
land use, while Mo exceeded the less stringent guideline for agricultural land use (Canadian
Council of Ministers of the Environment, 2014).

Table 2.2. Select chemical and physical parameters of mine tailings, organic amendments, and amended
tailings treatments.

Substrate/
Treatment
Experimental
materials
Tailings
Compost
Ash
Wood chips
Amended
tailings
100% ash
100% comp
Blend

C:N

P
(%)

K
(%)

EC b
(dS m-1)

WHCc
(%)

0.01
1.18
0.05
0.12

112:1
21:1
450:1
473:1

0.11
0.30
0.47
-

1.09
1.32
2.49
-

2.1±0.02
3.5±0.23
2.0±0.02
0.5±0.04

69.5±0.66
50.2±3.44
31.0±0.72
22.9±1.36

-

-

-

-

2.4±0.01
3.0±0.17
2.0±0.05

63.6±1.01
69.0±0.54
65.4±0.26

pH

a

OM (%)

C
(%)

N
(%)

8.7±0.07
7.8±0.05
10.3±0.02
7.5±0.10

0.1±0.02
23.9±1.45
26.8±1.23
97.7±0.90

1.12
24.3
22.5
56.7

9.3±0.04
8.1±0.09
8.7±0.04

3.9
4.6
4.3

2.3
2.7
2.5

Values are means ± standard error (n=3). Values without standard errors represent a single sample.
a
OM, organic matter; b EC, electrical conductivity; c WHC, gravimetric water holding capacity.

The municipal yard waste compost was mostly made up of organic material and sands
ranging from 0.1 to 4 mm, but also contained some large woody debris and coarse rocks (≤ 16
mm diameter). The compost was characterized by a slightly alkaline pH, adequate total nitrogen,
and a well-balanced C: N ratio (Table 2.2). Of the substrates studied, the compost had the highest
electrical conductivity (EC). Metal content of the investigated compost met the CCME
guidelines for both agricultural and industrial land uses (Table 2.3). The wood ash amendment
was primarily composed of fine-to-medium particles ranging from 2 to 4 mm and had a
considerably high pH and C: N ratio (Table 2.2). Concentrations of Al were alarmingly high and

27

Zn was above the CCME guideline for agricultural use (Table 2.3). In spite of these
physiochemical limitations, we assessed the ash in this study because of its potential to enhance
plant performance due to other potentially favourable characteristics such as high levels of
phosphorus (P) and potassium (K) (which are also important plant nutrients) relative to the other
amendments investigated. The wood chips (used for the “blend” treatment) ranged from 1 to 16
mm in size and were primarily composed of organic matter (Table 2.2). Because of these
properties, wood chips are a useful tool for adjusting the C:N ratio of reclamation materials and
also for preventing leaching of N from the rooting zone (Piorkowski et al., 2015).

Table 2.3. Select metal and metalloid concentrations (mg kg-1) of mine tailings and amendments used for
this study. Values are compared to the CCME guidelines for agricultural and industrial uses.

Element
Al
As
Cd
Co
Cr
Cu
Fe
Hg
Mo
Ni
Pb
Zn

Ash
1967
< 3.0
< 1.0
25.7
51.8
70.7
486
<3
3.15
30.9
< 1.0
216

Compost
828
< 3.0
< 1.0
16.9
52.2
77.9
545
<3
3.81
26.1
6.6
106

Tailings
74.6
< 3.0
< 1.0
30.8
138
600
525
<3
10.5
90.7
< 1.0
19.6

CCME*
(agricultural)
12
1.4
40.0
64
63
6.6
5
45.0
70
200

CCME
(industrial)
12
22
300
87
91
60
40
89
600
360

*CCME, Canadian Council of Ministers of the Environment soil quality guidelines (2014). Bolded values
are in exceedance of at least one of the referenced guidelines

Growth Response to Soil Amendments
Germination occurred on the amended tailings within four to ten days depending on the
species and growth medium used. Seedling emergence after 90 d growth was low on the
unamended tailings for both grass species (Figure 2.3). Soil amendments, regardless of
composition, had a significant effect (P < 0.05) on Pseudoroegneria spicata and Festuca
campestris emergence compared to the unamended tailings, with the exception of F. campestris
growing on the compost amended tailings which was similar to the unamended tailings (Figure
2.4a). When comparing seedling emergence between species, P. spicata outperformed F.

28

campestris on all treatments, but statistical significances were detected for the ash treatment
only. No clear relationship was observed between amendment relative composition and seedling
emergence rates. Despite successful germination and growth, neither one of the grass species
developed seed heads in any of the treated soils during the 90 d growth period.
Pseudoroegneria spicata shoots were, on average, taller than Festuca campestris shoots
on all treatments, but statistical significances were only detected on the amended tailings (Figure
2.4b). The compost-amended tailings yielded the tallest shoots for both species, however, shoot
heights were not statistically significant compared the blend treatment. There was evidence of a
positive correlation (R2=0.42, P < 0.0001) between compost concentration and P. spicata
seedling height (data not shown). A similar pattern was observed for F. campestris, however, the
association was less prominent (R2=0.25, P < 0.0001).
Plant productivity was sparse on the unamended tailings (Figure 2.3); despite some of the
seeds germinating, final seedling numbers were low. Shoot and root biomass of Pseudoroegneria
spicata were significantly greater (P < 0.05) than Festuca campestris on all treatments (Figure
2.5). On the amended tailings, there was at least a twofold difference in root and shoot biomass
between species. For both species, the compost treatment yielded the highest shoot and root
biomass (up to 1.4 g total dry biomass per pot) while the unamended tailings yielded the lowest.
With regard to total biomass, ash was the least productive amendment while the blend was
intermediate. Plants growing in the ash-amended tailings were stunted and showed signs of
nutrient deficiency (e.g. discolouration of shoots). Statistically, there were no differences in root
biomass between the compost and the blend amendments. There were also no significant
differences in root biomass between the ash and the blend treatments. Root-to-shoot ratios were
similar for both species and ranged from <1:1 on the unamended tailings to up to 3:1 in the ash
treatment (data not shown).

29

Figure 2.3. Pseudoroegneria spicata (left column) and Festuca campestris (right column) seedling
growth after 90 days. From top to bottom: treatments are control, ash, blend and compost.

30

Figure 2.4. Mean Pseudoroegneria spicata and Festuca campestris a) seedling emergence and b) shoot
heights by treatment after 90 d growth in amended mine tailings. Error bars are standard errors of the
mean. Treatments with different letters are statistically significant at P < 0.05 (one-way ANOVA,
Tukey’s HSD). * represents a statistical significance between species (determined by Welch’s t-test) for
that treatment.

Figure 2.5. Mean Pseudoroegneria spicata and Festuca campestris a) shoot biomass and b) root biomass
per pot by treatment after 90 d growth in amended mine tailings. Error bars are standard errors of the
mean. Treatments with different letters are statistically significant at P < 0.05 (one-way ANOVA,
Tukey’s HSD). * represents a statistical significance between species (determined by Welch’s t-test) for
that treatment.

A weak positive correlation between amendment compost concentration and total
biomass was detected (Figure 2.6). Total biomass responded negatively to ash concentration.

31

When controlling for seedling density (using ANCOVA), this relationship was strengthened
(R2=0.48 and 0.45 for Pseudoroegneria spicata and Festuca campestris, respectively).

Figure 2.6. Relationship between a) Pseudoroegneria spicata total biomass (roots + shoots) and b)
Festuca campestris total biomass per pot and relative concentrations of compost and ash in the soil
amendment mixtures. Data points are untransformed raw data.

Plant Metals Uptake
Shoot concentrations of select metals were determined for both plant species growing on
the three amendment mixtures (Table 2.4). Analysis indicated that Fe and Mo concentrations
were greater than the domestic animal tolerance limit for several of the treatments. The only
significant treatment effect was for Mo; both grass species accumulated a substantially greater
amount of Mo when growing in the ash-amended tailings compared to the other treatments.
Molybdenum concentration was significantly greater (nearly twofold) in Pseudoroegneria.
spicata tissue compared to Festuca campestris when grown on compost-amended tailings. In
examining the results more closely, Fe exceeded the tolerance limit in F. campestris growing on
the ash-amended tailings but the exceedance was negligible if sampling error is considered.
Despite the aluminum content of the wood ash being considerably high, shoot tissue aluminum

32

concentration remained below the domestic animal tolerance limit on the ash-amended tailings.
Translocation factors were >1 for Mo and Zn and <1 for the remaining metals.

Table 2.4. Pseudoroegneria spicata and Festuca campestris shoot accumulation (mg kg-1) of select metals and metalloids after 90 d growth in
amended mine tailings.

a

b

Element
Al

Total
75

MTL
1000

Cu

600

40

Fe

525

500

Mo

21.9

5

Zn

< 3.0

500

Amendment
treatment
100% compost
100% ash
blend
100% compost
100% ash
blend
100% compost
100% ash
blend
100% compost
100% ash
blend
100% compost
100% ash
blend

shoot tissue metal accumulation
PS vs. FC
P. spicata
F. campestris
(t-test)d
361 ± 93.0 a 245 ± 108 a
NS
526 ± 99.4 a 697 ± 291 a
NS
323 ± 46.6 a 442 ± 202 a
NS
26.4 ± 1.69 a 14.39 ± 1.87 a
NS
27.1 ± 2.25 a 24.0 ± 7.53 a
NS
22.7 ± 0.68 a 22.3 ± 8.54 a
NS
331 ± 65.1 a 273 ± 71.4 a
NS
457 ± 72.8 a 576 ± 216 a
NS
308 ± 32.1 a 343 ± 147 a
NS
37.4 ± 1.32 b 19.7 ± 3.28 b
*
183 ± 46.5 a 202 ± 14.4 a
NS
58.3 ± 15.7 b 48.4 ± 5.41 b
NS
34.9 ± 1.18 a 85.9 ± 27.7 a
NS
29.3 ± 1.0 a
28.1 ± 3.78 a
NS
32.1 ± 1.95 a 38.8 ± 6.96 a
NS

TFe (PS)
0.08 ± 0.02
0.15 ± 0.06
0.07 ± 0.02
0.50 ± 0.04
0.33 ± 0.14
0.24 ± 0.03
0.08 ± 0.02
0.18 ± 0.08
0.08 ± 0.02
2.44 ± 0.16
12.5 ± 4.62
3.43 ± 0.47
0.89 ± 0.04
1.46 ± 0.34
0.87 ± 0.08

TF (FC)
0.07 ± 0.04
0.3 ± 0.11
0.15 ± 0.04
0.12 ± 0.02
0.28 ± 0.09
0.21 ± 0.07
0.08 ± 0.03
0.33 ± 0.11
0.12 ± 0.03
0.41 ± 0.02
2.53 ± 0.30
1.01 ± 0.18
1.60 ± 0.47
1.02 ± 0.28
0.90 ± 0.22

a

Total elemental concentration of mine tailings prior to planting. Values are means ± standard error of the mean. bMTL = maximum tolerable
levels of metals in the shoots; values are for cattle (National Research Council, 2005) and bolded values indicate an exceedance. cTreatment means
with different letters are statistically significant at P < 0.05 (one-way ANOVA, Tukey’s HSD) for each species corresponding to each element.
d
Welch’s two sample t-tests were performed for each row (NS = non-significant; * = significant difference); PS = Pseudoroegneria spicata, FC =
Festuca campestris. eTF = translocation factor; the shoot:root ratio of the concentration of the corresponding element.

33

34

DISCUSSION
Effect of Organic Amendments on Tailings Characteristics
The establishment of vegetation on mine tailings is often facilitated by the addition of
organic soil amendments which are used to enhance soil physiochemical conditions for plant
growth (Brown et al., 2003; Solís-Dominguez et al., 2012). The efficacy of three locally
available soil amendments for reclamation and phytostabilization of the TSF were assessed in a
greenhouse trial. Assessment of tailings characteristics before and after amendment addition
revealed increased organic matter and total C content in the amended tailings, which is consistent
with other mine tailings studies (Cele and Maboeta, 2016; Shrestha et al., 2009). The composttreated tailings had the highest organic matter content and the ash-treated tailings had the lowest.
Organic matter is important for soil rehabilitation and reclamation for several reasons: 1) the
organic C provides an energy source for soil microorganisms which accelerates decomposition
and nutrient cycling, 2) long-term plant nutrient availability is enhanced because nitrogen is in an
organic form and is slowly released over time, and 3) the organic matter improves soil physical
conditions such as water retention and bulk density (Drozdowski et al., 2012; Gardner et al.,
2010; Larney and Angers, 2012; Shrestha et al., 2009). Because of these properties, the longevity
of positive effects is often greater when using organic amendments compared to traditional
reclamation methods such as inorganic fertilizers (Gardner et al., 2012; Tian et al., 2009).
The addition of organic amendments also altered tailings pH levels. The compost and the
blended amendment lowered tailings pH, but the effect was suboptimal as the amended tailings
remained moderately alkaline (pH >8). The ash amendment increased the tailings pH level from
moderately alkaline to strongly alkaline (pH >9), which is above what is deemed normal in most
soils (normal range is 5.5 to 8.5). In a recent review, Sheoran et al. (2010) reported that mine soil
pH range of 6 to 7.5 is adequate for agronomic or horticultural uses of mine sites. Although, in
arid environments, it is normal for pH to be slightly to moderately alkaline (pH between 7 and 9)
(Brady, 1990). Abnormally high soil pH can lead to mobility of As, Mo, and Se as well as
reduced availability of P and certain micronutrients (e.g., B, Mn, Fe) (Bolan et al., 2014b; EPA,
2007). In general, the addition of organic amendments increased the EC of the tailings, with the
exception of the blend which had little or no effect. In all treatments, EC remained below the
critical level of 4 dS m-1 at which plant growth is negatively affected (Drozdowski et al. 2012).

35

Based on the soil parameters assessed, the compost treatment appeared to provide the most
suitable soil conditions for revegetation of the historic Afton tailings.
The tailings investigated in this study had a relatively high gravimetric WHC, and so
water retention was not considered a limitation. Although, it is important to note that high WHC
(>80%) can lead to poor drainage and anoxic conditions which can affect root productivity
(Brady, 1990) and reduce overall revegetation success. The addition of organic amendments
reduced the WHC of the tailings, likely because the addition of larger organic particles reduced
bulk density and improved drainage of the substrate.

Growth Response to Organic Amendments
The results of the experiment indicate that the addition of organic amendments,
regardless of treatment, improved seedling germination and growth of native bunchgrass species
Pseudoroegneria spicata and Festuca campestris on the historic Afton tailings. The positive
influence of soil amendments on plant productivity was likely a result of increased organic
matter content in the amended tailings which improved tailings physiochemical conditions
(Rivard and Woodard, 1989; Shrestha et al., 2009). In a greenhouse study, Solís-Dominguez et
al. (2012) reported improvements in tailings pH, EC, organic carbon and total nitrogen as a result
of compost addition which led to improved plant growth. Of the treatments investigated in my
study, the 100% compost amendment was the most effective at promoting germination and
growth of both species. Plants growing in the ash-amended tailings were stunted and showed
signs of nutrient deficiency; even though the C content of the ash amendment was comparable to
the compost treatment, the lack of nitrogen coupled with increased pH levels may have created
less favourable conditions for plant growth. Under extreme soil pH conditions (<5.5 to >8.5)
certain plant macronutrients (e.g. N, P, K) can become immobilized and microbial activity can
decline (EPA, 2007). Because of these properties, it is possible that certain nutrients that were
contained in the ash, such as P and K, were not available for plant uptake. The data suggests that
incorporating the very strong alkaline ash material into the alkaline tailings was not an effective
method for optimizing plant growth. Assessment of post-amendment nutrient concentrations
would have revealed more insight as to the limitations of the ash material as a soil amendment.
Root-to-shoot ratios were around 1 for the compost treatment which indicates balanced
biomass allocation and adequate nutrient availability in the amended substrate (Wilsey and

36

Wayne Polley, 2006). Generally, when nutrients are limiting, plants will allocate more resources
to their roots which increases the root-to-shoot ratio (Ågren and Franklin, 2003). In this study,
the high root-to-shoot ratios of plants growing in the ash-amended tailings can be explained by
the lack of nitrogen in the growing medium which may have forced plants to allocate more effort
into root production at the cost of shoot production.
With regard to plant growth and overall productivity Pseudoroegneria spicata
outperformed Festuca campestris on all treatments. This can be partially attributed to the ability
of P. spicata to germinate under a wider range of conditions compared to other grassland species
(Young et al., 1981). The results were consistent with a recent field study where Carlyle (2012)
reported higher relative growth rates and shoot and root biomass for P. spicata compared to F.
campestris at the Lac du Bois Grassland Provincial Park (near Kamloops, BC). In the current
study, both grass species responded positively to increases in compost concentration which
suggests that nitrogen may have been a limiting factor for plant growth on these tailings. Several
studies have underscored the importance of soil nitrogen in mine reclamation because it is an
essential plant nutrient, yet it is often limiting in mine soil ecosystems (Bradshaw, 1997;
Shrestha et al., 2009; Shrestha and Lal, 2011).

Effect of Amendments on Metals Uptake
Shoot and root concentrations of select metals were assessed for both species after 90 d
of growing in the amended tailings. The results indicated high concentrations of Mo for both
plant species which exceeded toxicity limits in all treatments, but most notably when the ash
amendment was used. Elevated Mo levels can lead to molybdenosis (induced Cu deficiency)
when ingested by cattle or other ruminants (Drozdowski et al., 2012; Gardner et al., 2012). This
condition is influenced by relative concentrations of copper, molybdenum, and sulfur. In general,
the risk of molybdenosis increases when the Cu: Mo ratio is <2:1 (Mason 1971; cited by Gardner
et al., 2012). In this study, Cu: Mo ratios for all treatments were well below this threshold, with
the highest ratio being for the wheatgrass growing in the compost treatment (0.7:1). The
enhanced Mo uptake by grasses growing on the ash-amended tailings was likely the result of
elevated soil pH levels. Doran and Martens (1972) found similar effects of soil pH on metals
uptake when growing alfalfa in a fly-ash amendment. Under abnormally high pH conditions (pH
>8.5) molybdenum is soluble and readily available for plant uptake (EPA, 2007). This

37

information suggests that Pseudoroegneria spicata and Festuca campestris may not be suitable
for phytostabilization of these tailings due to their tendency to uptake molybdenum under
alkaline conditions. However, further additions of compost and/or wood chips may be worth
investigating because doing so may further neutralize tailings pH, thereby reducing the potential
for Mo uptake and lowering the risk of molybdenosis.
Aluminum concentration of the ash amendment was notably high (Table 2.3). When
coupled with its high pH (Table 2.2) this created ideal conditions for the formation of soluble Al
in the form of aluminate (Al(OH)4-1) which can cause soil toxicity and inhibit plant growth
(Fuller and Richardson, 1986). According to Hodson (2012), some plants are able to tolerate
excessive levels of aluminum and other metals by avoiding shoot uptake and concentrating them
in their roots. Both plant species used in this study accumulated substantially more aluminum in
their roots (up to seven times, data not shown) compared to their shoots which provides some
indication of their tolerance to aluminum. These results suggest that these species may be useful
for remediation of tailings and other mine wastes high in aluminum.
The translocation factor (TF) is a useful metric for measuring metal accumulation in plant
tissues (Mendez and Maier, 2007). Suitable candidate plant species for phytostabilization are
those which minimize shoot accumulation without limiting root uptake, thus TF values of <1 are
preferred (Mendez and Maier, 2008, 2007). While, in the current study, TF generally remained
below this threshold in both species for most of the metals investigated, values for Mo and Zn
exceeded (or were close to) this threshold for all treatments (Table 2.4). The results indicate that
the species investigated may not be suitable for phytostabilization of the TSF because of their
tendency to accumulate high amounts of Mo in their shoots.

CONCLUSION
Of the organic amendments investigated in this study, the City of Kamloops municipal
compost was the most effective at promoting native bunchgrass growth on the amended tailings.
Further investigation using higher rates of compost would be meritable because I suspect that
this will result in enhanced plant performance and reduced Mo uptake. Due to its high pH and
elevated aluminum content, the Domtar pulp mill wood ash was not suitable for amelioration of
alkaline mine tailings, as plants growing in the ash amended tailings were subjected to the ideal

38

conditions for aluminate toxicity. However, there may be potential to use this amendment for
remediation of acidic mine tailings such as those investigated by Solís-Dominguez et al. (2012).
Festuca campestris growth on the amended tailings was sparse in comparison to
Pseudoroegneria spicata. Although the latter exhibited good germination and growth, it also
accumulated elevated levels of Mo in its shoots which counted against its candidacy for
phytostabilization and use as a forage species at the TSF. However, there may be potential to use
these species in other technologies such as phytoremediation, where shoot accumulation is
encouraged and aboveground biomass is subsequently removed from site (Best et al., 2008).
Despite this verdict, further investigation of these grass species is required because it is likely
that under optimal soil pH conditions (pH range of 6 to 7.5), Mo uptake will decrease. Both
species minimized shoot uptake of aluminum when present in high quantities by concentrating it
in their roots, which prompts investigation of these species’ performance on aluminum rich mine
wastes.
The results of this study indicate that the 100% compost amendment is best suited to
ameliorate the mine tailings investigated, and that Pseudoroegneria spicata is the most suitable
candidate for revegetaion and phytostabilization at the TSF. In summary, this study provides
practical information regarding the suitability of soil amendments available in the Kamloops
region and the performance of native grassland species during restoration and phytostabilization
of alkaline mine tailings. In addition to this information being directly applicable to reclamation
at the TSF, it may also be useful for remediation planning and implementation at other sites
located in similar environments. Further research is needed to investigate native bunchgrass
performance on the compost amendment more closely, and to test the greenhouse results in the
field.

39

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between native and introduced grass species. Oecologia 150, 300–309. doi:10.1007/s00442006-0515-z
Wilson, S., 2009. The Value of BC ’ s Grasslands : Exploring Ecosystem Values and Incentives
for Conservation. Grasslands Conservation Council of British Columbia, Kamloops, British
Columbia.
Young, J., Evans, R., Eckert Jr., R., 1981. Temperature profiles for germination of bluebunch
and beardless wheatgrasses. J. Range Manag. 34, 84–89. doi:10.2307/3898117

43

CHAPTER 3 – FACILITATING MINE RESTORATION IN A SEMIARID
ENVIRONMENT WITH NURSE PLANTS, COVER CROPS AND SOIL
AMENDMENTS

INTRODUCTION
Within the past few decades, the importance of conservation and restoration of native
ecosystems and their biological diversity has gained the attention of scientists and practitioners
(Barnosky et al., 2011; Ceballos et al., 2015; Menninger and Palmer, 2006). Globally, grasslands
are an important natural resource because they provide an array of critical ecosystem services
such as wildlife habitat, water filtration and climate regulation, which are beneficial for the
environment and the economy (Costanza et al., 1997). The semiarid grasslands of interior British
Columbia (B.C.), Canada make up only less than 1% of the province’s land area, and are known
for their biological diversity and abundance of endemic plant and animal species (Government of
British Columbia, 1991; Wilson, 2009). These grasslands contain over 30% of the province’s
species at risk as well as several culturally important plant species (BC Conservation Data
Centre, 2017). Human activities such as extensive livestock grazing, urban development,
agriculture, and mining have led to the degradation of these unique ecosystems (Huber-Sannwald
and Pyke, 2005; van Ryswyk et al., 1966; Wilson, 2009). As such, these areas are the focus of
many conservation and restoration efforts (e.g. Grassland Conservation Council of BC, 2017;
Lysne, 2005).
The mining industry is an important component of the Canadian economy (Mining
Association of Canada, 2016), but it is environmentally destructive. The activities throughout the
mine cycle create disturbances on the landscape that leave pre-existing ecosystems in an altered
state (Bradshaw, 1992). For example, during the development of tailings storage facilities,
natural soils and vegetation are removed and replaced with fine-textured waste material
generated from ore processing (known as tailings). These anthropogenic materials typically lack
the physiochemical and biological capacity to support plant growth (Cele and Maboeta, 2016;
Gardner et al., 2010; Pepper et al., 2012); therefore, natural processes such as soil development
and plant community succession are severely impaired unless there is human intervention
(Bradshaw, 1997; Sheoran et al., 2010).

44

Mine reclamation is a type of ecological restoration concerned with returning mined land
to a productive land use. In B.C., mining companies are required to fulfill reclamation targets of
“equivalent land capability” under the B.C. Mines Act (Government of British Columbia,
Ministry of Energy, 2008). A conventional end land use for tailings storage facilities has been
the development of pasture-based ecosystems using non-native agronomic species (Brothers,
1990). Agronomic species were used because of their low cost and availability in large
quantities, and because they tend to establish rapidly on nutrient-poor, environmentally-stressed
sites allowing for quick economic returns and improvements in aesthetic qualities (Skousen and
Venable, 2008; Wu et al., 2011). These reclamation plans are limited and becoming out-dated for
a variety of ecological and social reasons. Firstly, research is showing that agronomic species can
alter the path of succession by preventing the establishment of native species (Davis et al., 2005;
Hagen et al., 2014) which results in plant communities with low genetic diversity (Dormaar et
al., 1995) and ecological resiliency (Menninger and Palmer, 2006). Secondly, non-native species
can rapidly disperse from the site of introduction and invade nearby natural communities
(Richardson et al., 2000). Finally, restoration of natural communities with native species and
biological diversity is a preferred end land use for mine sites from the perspective of First
Nations groups – who hold traditional rights to the land disturbed by mining activities – and
other primary stakeholders of the land.
Establishing native plant communities on mine sites is challenging because native seed is
expensive and difficult to obtain (Burton and Burton, 2002), and seeds do not germinate and
establish well on degraded sites (Drozdowski et al., 2012; Skousen and Venable 2008). If the
mine site being restored is located within a semiarid environment the challenges are exacerbated
because, not only are there physiochemical limitations associated with the mine soils (Mendez
and Maier, 2008), there are also climatic stressors such as intense temperatures, high
evapotranspiration rates, low precipitation, and strong winds (Munson and Lauenroth, 2012;
Pueyo et al., 2009). In BC’s semiarid sagebrush-steppe plant communities, the lack of rainfall
and high evaporation rates during the summer lead to prolonged periods of drought which reduce
germination and growth (Shorthouse, 2010). In such ecosystems, restoration practices can help
ameliorate these harsh abiotic conditions and improve revegetation success (Huber-Sannwald
and Pyke, 2005; Munson and Lauenroth, 2012; Pueyo et al., 2009).

45

Restoration begins with addressing the physiochemical and biological soil limitations so
that a vegetative cover can be established (Bradshaw, 1987; Sheoran et al., 2010). The use of
organic soil amendments is a common practice for reclamation of mine sites (Drozdowski et al.,
2012; Orman and Kaplan, 2007; Pepper et al., 2013). The addition of organic matter leads to
improved soil conditions because it increases plant nutrients and microbial activity, enhances
water retention, and reduces soil bulk density (i.e. compaction) (Brown et al., 2003; Cele and
Maboeta, 2016; Gardner et al., 2010). The enhanced soil conditions increase plant productivity
(Gardner et al., 2010; Waterhouse et al., 2014) which, in turn, supports the positive feedback
loop between plants and soils (Shrestha et al., 2009), leading to the development of selfsustainable plant and microbial communities (Palmer et al., 2006; Pepper et al., 2012), the latter
of which is the ultimate goal of restoration (Bradshaw, 1997; Palmer et al., 2006). During mining
operations, natural topsoil is usually conserved for reclamation (Sheoran et al., 2010), but is less
available in arid and semiarid regions because these areas typically have low levels of biomass
productivity and organic matter accumulation (Burke et al., 1989), and so soil amendments often
need to be imported from external sources. From an economic standpoint, locally available
materials are preferred by mining companies because the cost of hauling is reduced. Many
commonly used soil amendments, including municipal sewage sludge, compost, biochar and
wood ash, are waste by-products of various industries; therefore the practice of using these soil
amendments for mine reclamation is mutually beneficial for both the source and the mining
company.
Successful restoration can be achieved when natural ecological processes are mimicked
during the restoration process (Bradshaw, 1997, 1992, 1987). Species interactions among plants
are a well-researched topic in contemporary ecology and should be considered during restoration
(Bertness and Callaway, 1994; Bruno et al., 2003; Stachowicz, 2001). In natural plant
communities, it is understood that neighboring plants simultaneously exert both positive and
negative effects on one another, and it is the net balance that determines the outcome of the
relationship (Callaway and Walker, 1997). Until recently, ecologists have focused on negative
interactions (i.e. competition) as a driving force for ecological succession (Grime, 1973; Tilman,
1982), but the role of positive interactions (facilitation) is rapidly gaining importance in
restoration theory (Bruno et al., 2003) and practice (Gómez-Aparicio, 2009; Padilla and
Pugnaire, 2006). Positive interactions occur when one species (the benefactor) benefits from the

46

presence of another species (the facilitator) that ameliorates abiotic and/or biotic conditions in
some way, making the environment within their vicinity more favorable for survival and growth
(Bertness and Callaway, 1994). For there to be a facilitative effect, the net balance between the
positive (e.g. habitat amelioration, resource enhancement, protection from herbivory) and
negative interactions (e.g. root competition, excess shade, allelopathy) must be positive
(Callaway, 1995). Research has supported the theory that facilitation increases along an abiotic
stress gradient (Bertness and Callaway, 1994; Cavieres and Badano, 2009; Maestre et al., 2009),
therefore it is believed to be an important process during plant community assembly in harsh
environments such as deserts and alpine areas (Padilla and Pugnaire, 2006). However, when
ecological conditions become more favorable, the outcome of the relationship between
associated species may shift from facilitative to competitive (Padilla and Pugnaire, 2009). The
use of facilitation as a restoration tool in stressful environments has gained increased attention in
recent years (Gómez-Aparicio, 2009; Padilla and Pugnaire, 2006; Ren et al., 2008).
In stressful environments, such as deserts and alpine areas, seedling establishment is
enhanced near adult shrubs or other large plants (known as “nurse plants”) (Padilla and Pugnaire,
2006), resulting in noticeably visible “islands of fertility” (Moro et al., 1997; Walker et al., 2001)
around the nurse plants. This phenomenon is a result of the nurse plants facilitating neighboring
individuals by ameliorating extreme environmental conditions through canopy protection and
variety of other mechanisms including resource enhancement and protection from herbivory
(Padilla and Pugnaire, 2009, 2006). There are several advantages to growing close to a nurse
plant, such as 1) the shade provided by nurse plant canopies can buffer extreme air temperatures
and solar radiation which leads to lower soil temperatures and reduced soil water evaporation
(Franco and Nobel, 1989; Padilla and Pugnaire, 2009), 2) nurse plants can improve soil moisture
at the surface through a process known as “hydraulic lift”, where deep soil is accessed by the
taproot and re-distributed at the surface (Cardon et al., 2013; Richards and Caldwell, 1987), 3)
the enhanced conditions under nurse canopies improves productivity and subsequently increases
nutrient cycling through the accumulation of organic matter (Cardon et al., 2013; Claus
Holzapfel and Mahall, 1999; Pugnaire et al., 1996), and 4) canopy protection by nurse plants
prevents understory plants from being grazed (Padilla and Pugnaire, 2006). The facilitative
effects of nurse plants on neighbors (referred to as the “nurse effect”), can be beneficial for

47

establishing desirable species during restoration of degraded ecosystems (Padilla and Pugnaire,
2006).
Studies of nurse effects have been conducted in several biomes throughout the world. In
the Mediterranean semiarid-steppe regions of Spain, the legumous shrub Retama sphaerocarpa
facilitates a diverse understory plant community by reducing air temperature and solar radiation
levels, and by improving soil water and nutrient status (Moro et al., 1997; Padilla and Pugnaire,
2009; Pugnaire et al., 1996). In the extremely arid Sonoran Desert of California, adult Ambrosia
deltoidea and Cercidium microphyllum shrubs facilitate the establishment of the rare cacti
species Carnegia gigantea by providing refuge from high soil temperatures and enhancing soil
nitrogen levels (Franco and Nobel, 1989). A meta-analysis of a wide range of nurse species in
the alpine regions of the Andes Mountains in Chile and Argentina revealed enhanced plant
community diversity under nurse plants compared to exposed areas. As such, facilitation with
nurse plants can be used as a tool for improving the overall health and resiliency of ecological
communities during restoration (Bertness and Callaway, 1994; Callaway, 1995; Cavieres and
Badano, 2009).
Artemesia tridentata (big sagebrush) is a keystone species in the shrub-steppe ecosystems
of B.C.’s semiarid grasslands (Lysne, 2005). In addition to being an important food source for
ungulates and critical habitat for small mammals and birds (McArthur, 2008), A. tridentata is
known for its various facilitative effects on neighboring plants (Cardon et al., 2013; Schlesinger,
1990). Adult shrubs have dense canopies with spread-out branches, and can grow to a height of 4
m (USDA, 2016). The large canopy can act to protect understory herbaceous plants from
extreme temperatures, solar radiation and herbivory, while accumulating moisture (from snow)
in the winter, which facilitates spring growth (West, 2000). The root morphology of A. tridentata
is a dual root system that includes a shallow, diffuse root mass and a deep taproot that can carry
out the process of hydraulic lift (Richards and Caldwell, 1987). Several studies have attributed
enhanced moisture and nutrient availability under of A. tridentata shrubs (Burke et al., 1989;
Cardon et al., 2013) to this phenomenon. Most of the research investigating sagebrush nurse
effects was conducted in degraded rangelands where the shrubs were already well-established
adults (Cardon et al., 2013; Drivas and Everett, 1988; Huber-Sannwald and Pyke, 2005).
However, in mine reclamation settings, there are no mature shrubs because pre-existing plant
communities have been removed by the mining process, therefore seeding, or transplanting

48

seedlings obtained from nurseries are the only feasible options for establishing nurse plants
(Booth, 2005). To date, there has been no research on the facilitative effects of transplanted A.
tridentata seedlings during mine tailings reclamation (but see Schuman et al., 1998).
Another restoration practice widely used in agricultural, rangeland and forested systems
is the use of cover crops. Cover crops are annual or short-lived perennial species which can be
sown together with the target species to achieve short-term ecological benefits, such as forage
production, erosion control, and exclusion of weedy species while the desired plant community
establishes (Espeland and Perkins, 2013). Similar to nurse plants, cover crops can also ameliorate
harsh abiotic conditions by creating favourable microclimates that facilitate the establishment of
desired species (Gómez-Aparicio, 2009; Maestre et al., 2009, 2003). In arid or semiarid
environments, cover crops are capable of reducing soil temperature and evaporation by shading
the soil surface, resulting in improved soil water availability (Choi and Mohan, 1995; KruegerMangold et al., 2006). Cover crops can also improve soil fertility by adding organic matter (or
“green manure”) and fixing nitrogen (depending on whether the species is a nitrogen fixer) (Bai
et al., 2017; Tribouillois et al., 2014). Since most cover crop species tend to be extremely
competitive, introduced species (Tribouillois et al., 2014), there is debate on whether they
impede or facilitate the establishment of long-term, more desirable perennial species (Espeland
and Perkins, 2013). Some studies have shown that sowing with agronomics results in
competitive exclusion of native species, thus halting the progress of natural succession (Davis et
al., 2005; Hagen et al., 2014), while others have reported minimal impacts of cover crops on
early establishment and growth of desired species (Espeland and Perkins, 2013; Skousen and
Venable, 2008). Generally, it seems that the facilitative effects of cover crops are species specific
(Choi and Mohan, 1995; Davis et al., 2005; Espeland and Perkins, 2013; Tribouillois et al.,
2014), and are more pronounced under stressful conditions (Espeland and Perkins, 2013; Maestre
et al., 2009, 2003), therefore, there is potential to use cover crops to facilitate native grassland
plant community development during reclamation of mine sites.
This study investigates the use of nurse plants, cover crops and soil amendments as
restoration tools for re-establishing semiarid grassland communities at the Historic Afton
Tailings Storage Facility. I assessed 1) whether nurse plants influence the abiotic environment
and facilitate the establishment of native species during early restoration, 2) whether agronomic
cover crops facilitate or impede native plant community development, and 3) the efficacy of

49

locally available soil amendments under field conditions. Firstly, I expected plant community
establishment to be more successful under Artemesia tridentata canopies compared to in the
open because of the reported abilities of semiarid shrubs to ameliorate harsh environmental
conditions and improve soil resources. Secondly, I expected annual cover crops to reduce native
plant community diversity in the short-term because of their competitive nature. Finally, I
expected soil amendments to have a positive effect on plant performance and overall restoration
success.

MATERIALS & METHODS
Study Site
In summer 2014, a research site was established at the Historic Afton Tailings Storage
Facility (TSF), which is located approximately 15 km west of Kamloops, B.C. (50° 39’ N, 120°
32’ W; elevation 700 m) (Figure 3.1). The TSF is located within the BGxw1, the Nicola variant
of the very dry warm subzone of the bunchgrass biogeoclimatic zone (Government of British
Columbia Ministry of Forests, 1991). The region experiences a semiarid climate with minimal
annual precipitation (typically <350 mm) and hot, dry summer months with the highest average
daily maximum temperatures (29 °C) occurring in July (Table 3.1). Eighty-one percent of the
precipitation is comprised of rainfall and the remaining 19 % is snowfall. The growing season
typically spans from April to September with average temperatures ranging from 9.9 to 21.5 °C.
Winter mean temperatures range from -2.8 to 5.2 °C (Government of Canada, 2015). The study
year (2016) was hotter and wetter than the long-term average. Daily average and maximum
temperatures during the 2016 growing season were 0.8 and 1.1 °C higher than the normal,
respectively, and mean precipitation was 111% of the long-term average.
The tailings material is fine textured and originated from rock mined from the Afton Pit
and the East and West Ajax Pits (currently owned by New Gold Ltd.) during previous mining
operations which spanned from 1977 to 1997. A series of reclamation activities were conducted
at the ~75 hectare tailings storage facility between 1978 and 1992 in an effort to enhance wildlife
forage and domestic rangeland, and to stabilize soils and prevent erosion. The previous
reclamation involved seeding with agronomic species. At the time of this study, the existing
plant community was sparse and comprised primarily of non-native grasses such as Agropyron

50

cristatum (crested wheatgrass). The tailings facility was dewatered in 2015 and is currently
undergoing reclamation.
Table 3.1. Climate data from Kamloops A weather station (345 m in elevation and 8 km northeast of the
study site) including study years and long-term normals.
1981-2010
long-term
Climate Parameter
2015
2016
normals
Mean annual precipitation (mm)
313.1
335.1
277.6
Mean precipitation Apr. to Oct. (mm)
142.4
181.6
163.4
Mean annual temperature (°C)
10.8
10.4
9.3
Mean temperature Apr. to Oct. (°C)
18.0
17.6
16.8
Mean maximum temperature (°C)
16.6
16.0
14.8
Mean maximum temperature Apr. to Oct. (°C)
25.6
24.9
23.8
Growing degree days Apr. to Oct.*
2376
2301
2175
Frost free period (days)
182
195
169
*Reference temperature = 5 °C

Figure 3.1. Map of study site at the Historic Afton Tailings Storage Facility adjacent to the New Gold
mine, 15 km west of Kamloops, British Columbia. The red marker indicates the location of the research
site. Green pins indicate the locations from which the soil amendments were obtained. Compost was from
the City of Kamloops composting facility and wood ash was from the Domtar Pulp Mill.

51

Experimental Design
The TSF research site was located at the northwest end of the tailings pond and was
comprised of 24 experimental plots arranged in a 3 x 8 grid (Figure 3.2). Each plot was a 180gallon cattle tank buried into the tailings such that the upper rim was situated evenly with the
ground surface. The dimensions of the plots measured 102 cm wide × 147 cm long × 61 cm
deep. The surface area of plots measured 1.23 m2 and the distance between plots was 1.5 m
within columns and 3 m within rows. In fall 2014, stockpiled tailings material was added to each
tank, leaving 15-20 cm of vertical space for the soil amendments to occupy.

Figure 3.2. View of Historic Afton Tailings Storage Facility research plots (left) and individual plot
containing unamended tailings (right).

A randomized complete block design with three factors and three replicates was
implemented at the TSF research site for the 2016 field season (Figure 3.3). The first factor was
soil amendment type (compost/compost + ash), the second factor was nurse plant (sagebrush/no
sagebrush) and the third factor was cover crop (cover crop/no over crop) for a total of eight
different treatment combinations (2 × 2 × 2 = 8). Treatments were randomly assigned to each of
the three blocks using “The Random Number Generator” iPhone iOS application (Nicholas
Dean, 2013).

52

1
2
3
4
5
6
7
8

A
NP

B
NP + CC

NP + CC
CC
NP
CC
NP + CC

NP
NP
NP + CC
CC
CC

C
NP + CC
NP
NP + CC

Soil Amendments

Compost
Compost + Ash

CC
NP
CC

Figure 3.3. Experimental plot layout for 2016 Historic Afton Tailings Storage Facility field study where
NP = nurse plant and CC = cover crop. Soil amendments are indicated by shaded cells and include a
‘compost’ treatment and a ‘compost + ash’ treatment. All plots were seeded with a custom native seed
mix. Each combination of treatment factors is represented once within each column (block), and therefore
is replicated three times (n=3).

Soil Amendments
Two locally available soil amendments: compost from the City of Kamloops Cinnamon
Ridge composting facility and wood ash from the Domtar pulp mill (Kamloops, B.C.) were
selected for the field experiment. The compost was produced from municipal yard waste and the
ash was a byproduct of waste wood (commonly referred to as ‘hog fuel’) incineration (refer to
Chapter 2 for chemical and physical attributes of the soil amendments). Both amendments were
available within a 15 km radius of the TSF. The amendments were stockpiled at the TSF in
September 2014 and covered with tarps until needed for the experiment. The soil amendment
treatments were a ‘compost’ and a ‘compost + ash’ treatment applied at 325 and 340 Mg ha-1,
respectively. The ‘compost’ treatment was a 2:1 mixture of compost and tailings and the
‘compost + ash’ treatment was a 2:1:1 mixture of compost, ash and tailings. In September 2015,
the amendments were mixed in the field and applied to the upper surface of each plot (Figure
3.4).

53

Figure 3.4. View of soil amendments and tailings prior to mixing (left) and amended study plot (right).

Nurse Plants
The nurse plants were one-year old Artemisia tridentata (big sagebrush) seedlings (15-35
cm in height) purchased from Splitrock Environmental (Lillooet, B.C.) in April 2015. Prior to
transplanting, seedling heights were measured and the tallest 36 seedlings were categorized into
three size classes: small (15-17.5 cm), medium (18-22 cm), and large (23-35 cm) and stored in
the greenhouse until needed for the experiment. Nurse seedlings were transplanted to the study
plots in September 2015; one seedling from each size class was randomly selected and planted
on each plot, equating to three seedlings per experimental plot. Care was taken to arrange the
seedlings systematically and consistently throughout study plots (Figure 3.5). The plots – at this
time containing the soil amendments and nurse plants – were overwintered. Four out of thirty-six
(11%) seedlings did not survive the winter. These seedlings were replaced with new seedlings of
the same size class in March 2016.

54

Figure 3.5. Measuring sagebrush seedlings in the greenhouse prior to transplanting (top left), transplanted
nurse plants at the Historic Afton Tailings Storage Facility (top right) and arrangement of nurse plants
(S=small, M=medium, L=large) (bottom). The arrangement of nurse plant size classes was systematic and
consistent throughout study plots.

Seed Mix Selection and Seeding
A total of six native grasses, five native forbs and two agronomic species were selected
for the field experiment (Table 3.2). The native forb species were chosen for their cultural
significance (medicinal and food) and the remaining species were selected based on their
precipitation and elevation range, forage value, erosion control potential, drought tolerance, and
ease of establishment (Dobb and Burton, 2013). The native species chosen for this study are
representative of B.C.’s interior grassland communities. Six of the seven grass species used in
this study are contained in the operational seed mixes used for reclamation at the adjacent New
Gold New Afton Mine.
Twenty-four seed packets (1 per study plot) were filled with 200 seeds of each of the
native grass and legume species. For the ‘cover crop’ treatment, an additional 200 seeds of the

55

agronomic species Lolium multiflorum and Medicago sativa were added to half (12) of the
packets (Table 3.2). All packets received 25 mg of sand to help achieve even dispersal when
sowing. Based on the results of the germination trial (see Appendix A), the seeding rates equated
to ~1200 and ~1500 pure live seeds (PLS) per m2 for the ‘native seed’ and ‘cover crop’
treatments, respectively. These seeding rates are near the uppermost limit of the recommended
sowing density of 750-1500 PLS/m2 for revegetation of degraded grasslands (Burton et al.,
2006). At the end of April 2015, the overwintered study plots were raked to achieve a
heterogeneous soil surface and then seeded by hand. This technique was used because, in a
recent study at the adjacent New Gold mine, raking increased seedling establishment on
stockpiled topsoil (Baethke, 2015). Each study plot received 3 gallons of water immediately after
seeds were sown.

Table 3.2. List of plant species chosen for field experiment.
Common Name
Scientific Name
Type
Source
Uses
Bluebunch wheatgrass
Pseudoroegneria spicata
Native grass
Pickseed
Rough fescue
Festuca campestris
Native grass
Pickseed
Sandberg bluegrass
Poa secunda
Native grass
Pickseed
Junegrass
Koeleria macrantha
Native grass
Pickseed
Slender wheatgrass
Elymus trachycaulus
Native grass
Pickseed
Alkali Bluegrass
Poa juncifolia
Native grass
Pickseed
American vetch
Vicia americana
Native legume
GPEC
Medicinal/food
Yarrow
Achillea millefolium
Native forb
Quality Seed Medicinal
Arrow-leaved balsamroot Balsamorhiza sagittata
Native forb
Quality Seed Food/medicinal
Brown-eyed susan
Gaillardia aristata
Native forb
Quality Seed Medicinal
Nodding onion
Allium cernuum
Native forb
Quality Seed Food
a
Annual ryegrass
Lolium multiflorum
Agronomic grass
Pickseed
a
Alfalfa
Medicago sativa
Agronomic legume
Pickseed
Big sagebrushb
Artemisia tridentata
Native shrub
Splitrock
a
Agronomic seed was added to half of the plots to represent the ‘cover crop’ treatment.
b
Artemisia tridentata seedlings were planted in half of the plots as to represent the ‘nurse plant’ treatment.

Irrigation System Set-up
In April 2015, an automatic gravity fed drip irrigation system was constructed at the TSF
(Figure 3.6). The system utilized a 2000-gallon water tank and consisted of three zones (one per
block), each controlled by a battery powered timer. The irrigation timers were equipped with rain
sensors that prevented the system from operating during rain events. The irrigation system was

56

turned on immediately after the plots were seeded and was programmed to deliver 8-10 mm of
water per week during the seedling establishment period (from the seeding date until mid-May).
The irrigation system was turned off in mid-May and plots became dependent on natural
precipitation for the remainder of the growing season. The reason for limiting the moisture
supply was to reduce the potential for competitive interactions between nurse plant and target
species, thus making any facilitative effects more apparent (Padilla and Pugnaire, 2009). Plots
were monitored several times a week throughout the field season.

Figure 3.6. View of automatic gravity feed drip irrigation system installed at the Historic Afton Tailings
Storage Facility research site in 2015. A 2000-gallon water tank elevated on the tailings dam (top left), 3way independent water delivery system (top right), low pressure automatic irrigation timer (bottom left)
and ½ gallon/hr. drip nozzle (bottom right).

57

Data Logger Set-up
In March 2016, prior to seeding, each plot was instrumented with Hobo ® data loggers
(Onset Computer Corporation, Bourne, MA) to monitor soil moisture and soil temperature levels
throughout the duration of the study. Two additional probes were deployed in an open location,
directly into the tailings. Soil probes were installed at the ~5 cm soil depth (Padilla and Pugnaire,
2009) and data were recorded in hourly intervals from April 1 to August 15 (Figure 3.7).

Figure 3.7. Tailings mean and maximum temperature (left) and moisture (right) at the Historic Afton
Tailings Storage Facility over the 2016 study season (April–August). Soil temperature and moisture were
measured at the 5 cm depth (Hobo®, Onset Computer Corporation, Bourne, MA) in an exposed location.

Data Collection
Baseline soil sampling was conducted in April 2016, prior to seeding the plots. A total of
six composite soil samples (three from each amendment treatment) were taken from the top 15
cm layer of randomly selected plots. The field samples along with samples of pure tailings
material and soil amendments were sent to the British Columbia Ministry of Environment
Analytical Laboratory (BCMEAL) (Victoria, BC) for analysis of soil pH, nutrient and metals
content. Laboratory methodology and results of soil analysis are discussed in Chapter 2 (also see
Appendix B for a list of tailings total elemental concentrations).
Field data collection was conducted during the second week of August 2016. Prior to
sampling, the data loggers were retrieved from the plots and the irrigation system was
disassembled. The data were downloaded from the Hobo® devices using the provided

58

HOBOware software (Onset Computer Corporation, Bourne, MA) and summarized into the
variables ‘mean soil temperature’, ‘mean daily maximum soil temperature’ and ‘mean soil
moisture’. Three soil cores (approx. 53 cm3 each) were taken from the surface of plots
representing the “ash” and “compost” treatments, and from the unamended tailings on the ground
in order to calculate bulk density. Vegetation cover of each plot was documented with high
resolution photographs taken using a Nikon SLR Camera. Plant species cover was assessed using
a 0.25 m2 quadrat (Coulloudon et al., 1999) placed in a representative location within each study
plot (Figure 3.8). The Shannon-Weiner index of plant community diversity was calculated with
the species cover data for each plot using the equation:
𝑆ℎ𝑎𝑛𝑛𝑜𝑛 − 𝑊𝑒𝑖𝑛𝑒𝑟 𝐼𝑛𝑑𝑒𝑥 (𝐻) = − ∑𝑠𝑖=1 𝑝𝑖 𝑙𝑛 𝑝𝑖

[1]

and a Simpson diversity index was calculated using the same data with the equation:
𝑆𝑖𝑚𝑝𝑠𝑜𝑛 𝐼𝑛𝑑𝑒𝑥 (𝐷) = ∑𝑠

1

2
𝑖=1 𝑝𝑖

[2]

where p is the proportion (n/N) of individuals of one particular species (n) divided by the total
number of individuals found (N) and s is the number of species. Both equations are from
Colwell (1988). Four parameters were selected to represent sagebrush/nurse plant abundance.
They were ‘cover’, ‘horizontal canopy area’, ‘canopy volume’ and ‘dry biomass’. When
measuring the horizontal canopy area of the sagebrush nurse plants in the field, plants were
removed from the plots, repotted then placed (one at a time) in front of a custom made
checkerboard with 2-inch squares, then photographed from a standardized distance of about 2 m
(modified from Collins and Becker, 2001) (Figure 3.8). The photographs were imported into
ImageJ 1.50i software (National Institutes of Health, USA) and analyzed by setting the scale
(using the known distance of the checkers) and drawing a polygon around the perimeter of the
shrubs. Sagebrush cover was measured by considering the entire plot as one quadrat. Sagebrush
canopy volume was measured by taking three measurements of the shrub canopy (major axis,
minor axis and vertical axis) (modified from Franco and Nobel, 1989) and inputting the variables
into the equation:

59

𝑉 = 𝑎𝑏𝑐

𝜋
6

[3]

which is used to calculate the elliptical volume (V) of an object; a, b and c are the lengths of the
major axis, minor axis the vertical axis, respectively. Sagebrush seedlings were placed in paper
bags and oven-dried for 24 h at 70 °C to determine dry biomass. Aboveground plant biomass
(excluding sagebrush) within each 0.25 m2 quadrat was clipped as close to the soil surface as
possible. Samples were placed in paper bags and oven-dried for 24 h at 60 °C. Dry weights were
measured and extrapolated to a per hectare yield basis.

Figure 3.8. Assessing plant cover with a 0.25 m2 quadrat (left) and measuring horizontal sagebrush
canopy area with a custom 2-inch checkerboard (R) during 2016 data collection.

Statistical Analyses
Data for the field experiment were analyzed statistically using R version 3.2.3 “Wooden
Christmas-Tree” (The R Foundation for Statistical Computing). All data were checked for
normality using boxplots and residual plots. Homogeneity of variance was assessed using the
Fligner-Killeen test, and when necessary, the data were transformed using a natural logarithm or
a square root function. To determine if any of the three factors (soil amendment, nurse treatment
and cover crop) influenced reclamation success, the measured field parameters were analyzed
using a three-factor analysis of variance (ANOVA) followed by a Tukey-HSD post-hoc test. All
data were tested for significance at the 5% probability level. The mean ± standard error was
reported for the significances detected. A correlation matrix was developed to investigate for
relationships between sagebrush abundance and the abiotic and biotic parameters collected in the

60

field. Significant correlations (at P < 0.05) were investigated further using linear regression
analysis.

RESULTS
Soil Temperature
Mean daily soil temperatures of the study plots during the growing season were 11.0 ±
0.1 °C in April, 12.7 ± 0.1 °C in May, 16.3 ± 0.1 °C in June and 18.3 ± 0.1 °C in July (data not
shown). Artemisia nurse plants had a significant effect on mean daily soil temperature in the
early months of the growing season (April-May) and when averaged across the entire study
period (April-July) (Table 1). Mean daily temperatures in both April and May were 0.3 °C cooler
with nurse plants compared to without (Figure 3.9). When averaged over the entire study period,
soil temperature was 0.2 °C lower with nurse plants compared to in the open (Figure 3.9). There
were no significant correlations between sage abundance parameters (canopy volume,
aboveground biomass, horizontal canopy area and canopy cover) and mean soil temperature
(Table 3.3).
Mean daily maximum soil temperatures of the study plots during the growing season
were 14.1 ± 0.12 °C in April, 15.7 ± 0.18 °C in May, 19.3 ± 0.2 °C in June, and 20.8 ± 0.19 °C in
July (data not shown). When analyzing by month, there was only some evidence of Artemesia
canopies ameliorating extreme soil temperatures and this occurred in April, prior to seeding the
study plots (Table 3.3). During April, daily maximum soil temperatures were, on average, 0.6 °C
lower on nurse plots compared to the control (Figure 3.9). When analyzing soil temperatures
over the course of a single day, variations in temperature extremes were more apparent. On the
hottest day in May (May 28, 2017), when air temperatures reached 33.2 °C, maximum soil
temperatures were 13.8 °C in the open compared to 12.2 °C in plots without shrubs and 11.8 °C
in plots with shrubs (Figure 3.10). Overnight temperatures dropped to 7.5 °C, 9.6 °C and 9.5 °C
for the open location, and on plots without shrubs and with shrubs, respectively.
There was slight evidence (at the 10% probability level) of cover crops having a
moderating effect on soil temperature levels during the month of June (Table 3.3). Mean daily
soil surface temperatures of the study plots were, on average, 0.2 °C cooler in the shaded area
beneath the agronomic grasses compared to under stands of native grasses (data not shown).

61

Mean soil temperatures were 16.2 ± 0.1 vs 16.4 ± 0.1 °C for cover crops and no cover crops,
respectively.

Figure 3.9. Mean daily soil temperature (left) and mean daily maximum soil temperature (right) of study
plots with and without Artemisia tridentata (big sagebrush) nurse plants. Error bars are standard error of
the mean. The * represents a significant treatment effect at the 5% probability level.

Soil Moisture
Volumetric soil moisture content averaged 0.12 ± 0.01 m3 m-3 in April, 0.33 ± 0.02 m3 m-3
in May, 0.27 ± 0.02 m3 m-3 in June, and 0.17 ± 0.02 m3 m-3 in July. There was no direct evidence
of the presence of Artemisia shrubs exuding a positive (nor negative) effect on soil moisture
levels throughout the study period (Table 3.3). However, a slight negative trend (at the 10%
probability level) between sagebrush canopy volume and understory soil moisture levels was
identified in the months of May and June (Table 3.4). A similar trend was identified between
sage biomass and soil moisture in May only.
Cover crops had a negative effect on soil moisture levels over the entire study period and
in the months of June and July (Table 3.3). Soil moisture content was, on average, 22.5% lower
with cover crops (Figure 3.11). When analysing each month separately, moisture levels on plots
seeded with cover crops were 8% lower in May and 39% lower in July. In June, the effect on soil
moisture also depended on soil amendment type as indicated by the Seed × Amendment
interaction (Table 3.3). During June, soil moisture content of the study plots ranged from 19.2 to
30.6%, with the combination of cover crops and ash having the lowest amount of all treatments
(Figure 3.11).

62

Soil Amendments
After one growing season, the bulk density values of the amended tailings were almost
half that of the unamended tailings (1.52, 1.56 and 2.32 Mg m-3 for the ash, compost and control,
respectively) (data not shown). There were no clear direct effects of soil amendments on the
other abiotic variables examined (Table 3.3).

Table 3.3. Results of 3-way ANOVA looking at the effects of nurse plants (sage/no sage), seed type (native/native with cover crop) and soil amendments
(compost only/compost-ash mix) on physical soil parameters of study plots at the Historic Afton Tailings Storage Facility.
Nurse
Nurse x
Nurse x
Seed x
Nurse x Seed x
Seed
Amendment
Block
plant
Seed
Amendment
Amendment
Amendment
PPPPPPPAbiotic
F
value
F
value
F
value
F
value
F
value
F
value
F
P-value
F
value
Environment
Mean daily soil
temperature
April-July
6.34
0.70
0.419
0.00
0.957
3.74 0.074 1.00 0.335
3.48
0.083 0.73
0.407
2.75
0.099
0.025
April
12.0
0.63
0.437
0.22 0.646
2.55
0.106
0.003
May
16.5
0.15
0.709
0.82
0.382
1.67 0.218 1.26 0.280
4.57
0.051 0.62
0.445
11.4
0.001
0.001
June
4.40
3.72
0.02
0.889
2.97 0.107 1.85 0.195
4.18
0.060 0.00
0.968
7.58
0.055
0.074
0.006
July
0.62
0.445
0.00
0.988
0.41
0.535
3.08 0.101 0.07 0.795
0.10
0.759 0.07
0.793
0.74
0.494
Max daily soil
temperature
April-July
April
May
June
July

0.41
8.75
1.12
0.81
0.70

0.535
0.008
0.308
0.382
0.418

0.02
0.20
0.51
0.47

0.900
0.663
0.487
0.502

0.00
0.03
0.25
0.09
0.03

0.966
0.865
0.625
0.767
0.856

0.15
0.00
0.22
0.32

0.702
0.979
0.650
0.580

0.01
0.93
0.00
0.05
0.00

0.945
0.347
0.962
0.828
0.978

0.20
0.18
0.03
0.36

0.664
0.676
0.871
0.559

0.09
0.03
0.02
0.01

0.770
0.865
0.889
0.929

0.11
1.38
0.31
0.32
0.25

0.896
0.277
0.737
0.735
0.782

Soil moisture
April-July
0.38
0.548
5.68
1.99
0.180
0.03 0.862 0.22 0.644
1.20
0.292 1.15
0.032
April
1.61
0.221
0.05
0.834
0.08 0.785
May
0.58
0.460
0.81
0.382
1.30
0.274
0.21 0.651 1.21 0.290
0.01
0.947 0.09
June
0.16
0.697
8.14
3.40
0.086
0.46 0.509 0.05 0.826
4.81
0.013
0.046 1.73
July
0.27
0.610
10.9
2.74
0.120
0.17 0.684 0.00 0.982
2.45
0.140 3.63
0.005
Bolded values indicate a statistical significance at the 5% probability level (non- italicized) or 10% probability level (italicized).

0.301
0.769
0.209
0.078

4.06
7.60
2.07
8.55
5.08

0.041
0.004
0.164
0.004
0.022

63

64

Figure 3.10. Time course of soil surface temperature of plots with and without Artemisia tridentata nurse
plants and at an exposed location at the Historic Afton Tailings Storage Facility, on a clear, hot day in late
spring (May 28, 2017). Data points are an average of twelve study plots except for the exposed tailings
which is an average of two similar locations.

Figure 3.11. Mean volumetric soil moisture content of study plots with and without agronomic cover
crop (averaged over the study period and by month). June data includes Seed × Amendment interaction
(comp = compost). Error bars are standard error of the mean. Treatments with different letters are
statistically different at the 5% probability level.

65
Table 3.4. Correlation matrix showing Pearson correlation statistics and P-values for relationships
between sage abundance parameters and physical soil parameters of study plots at the Historic Afton TSF.
Canopy Volumea
Abiotic
Environment
Mean daily soil
temperature
April-July
April
May
June
July
Maximum daily
soil temperature
April-July
April
May
June
July

Biomassb

Horizontal Areac

Canopy Coverd

Pearson

P-value

Pearson

P-value

Pearson

P-value

Pearson

P-value

-0.07
-0.16
-0.12
0.14
-0.05

0.818
0.626
0.708
0.674
0.866

0.14
-0.11
0.15
0.32
0.03

0.655
0.730
0.646
0.318
0.931

0.06
-0.01
0.03
0.21
-0.07

0.857
0.968
0.934
0.519
0.823

0.22
0.03
0.15
0.34
0.11

0.485
0.934
0.651
0.274
0.728

-0.20
-0.12
-0.25
-0.15
-0.19

0.530
0.720
0.425
0.647
0.555

-0.19
-0.11
-0.19
-0.13
-0.22

0.562
0.733
0.559
0.692
0.501

-0.15
0.01
-0.17
-0.13
-0.18

0.645
0.965
0.597
0.676
0.580

-0.10
0.10
-0.14
-0.06
-0.15

0.762
0.749
0.672
0.860
0.641

Soil moisture
April-July
-0.45
0.140
-0.36
0.245
-0.41
0.186
-0.17
0.591
April
-0.09
0.782
0.02
0.945
-0.05
0.873
0.12
0.706
May
-0.49
0.102
-0.30
0.348
-0.52
0.081
-0.50
0.099
June
-0.43
0.160
-0.42
0.169
-0.22
0.502
-0.50
0.099
July
-0.49
0.103
-0.40
0.204
-0.48
0.118
-0.26
0.424
a
b
c
sagebrush canopy elliptical volume; sagebrush aboveground biomass; sagebrush horizontal canopy
area; d sagebrush canopy cover. Bolded values are statistically significant (P < 0.1).

Plant Community Establishment
At the end of the growing season, three (Pseudoroegneria spicata, Elymus trachycaulus
and Poa spp.) of the six seeded native grasses were observed to have established on the study
plots (Table 3.5). Native forb establishment was limited to only one (Achillea millefolium) of
four species seeded. Three non-seeded, volunteer species (Hordeum jubatum, Puccinellia
nuttaliana and Danthonia intermedia) were also recorded on the study plots.

66

Plant Productivity
Statistically, there was no evidence of Artemisia shrubs facilitating target species
establishment (Table 3.6). In fact, total plant cover (excluding nurse plant cover) was lower on
plots planted with nurse shrubs compared to those without (76.2 ± 5.3 vs. 93.5 ± 3.2%,
respectively) (Figure 3.12). There was also some evidence (at the 10% probability level) of a
negative effect of Artemisia on total aboveground plant biomass (excluding nurse plant biomass)
when the data was transformed using a natural logarithm function (5323 ± 295 Kg ha -1 without
sage vs. 4658 ± 330 Kg ha-1 with) (Figure 3.12).
When analyzed by functional group, native graminoid cover was lower with Artemisia
than without, but this effect also depended the addition of cover crops, as shown by the Nurse ×
Cover Crop interaction (Table 3.6). Native graminoid cover was highest (69.8 ± 3.6%) when
nurse plants and cover crops were excluded and lowest (21.1 ± 7.3%) when both treatments were
included (Figure 3.13). A notable positive trend between sagebrush abundance parameters and
volunteer species cover was detected, with the strongest determinant of volunteer cover being
horizontal canopy area (Table 3.7; Figure 3.15).
When analysing plant cover by species, Poa spp. followed a similar pattern where cover
was determined by an interactive effect involving nurse plants and cover crops (45.8 ± 5.8% for
no sage/no cover crop vs. 14.2 ± 4.5% for sage/cover crop, respectively) (Figure 3.13). The
agronomic cover crop had a negative (i.e. competitive) effect on Pseudoroegneria spicata cover
(16.4 ± 2.6 without agronomics vs. 3.4 ± 0.6% with) (Figure 3.14). The establishment of Elymus
trachycaulus depended on an interactive effect between cover crops and soil amendments (Table
3.6), with the compost-native seed combination yielding the highest cover (7.5 ± 1.7%) and the
compost-cover crop combination yielding the lowest (0.83 ± 0.8) (Figure 3.14).

Plant Community Diversity
There was evidence of nurse plants and cover crops having an effect on plant community
diversity. Artemisia shrubs and cover crops had an interactive effect on the Simpson’s diversity
index (D) (Table 3.6); the combination of nurse plants without cover crops had the highest D
value (4.2 ± 0.3) while nurse plants with cover crops had the lowest (2.8 ± 0.4) (Figure 3.16).
Species richness was influenced by the addition of agronomic cover crops; on average, 6.4 ±
0.19 species were counted on plots with cover crops compared to 5.3 ± 0.2 without (Figure 3.16).

Table 3.5. List of species identified and mean relative cover on study plots (by factor) at the Historic Afton Tailings Storage Facility.

Species
Scientific Name
Bluebunch wheatgrass Pseudoroeugneria spicata
Bluegrass species
Poa spp.
Slender wheatgrass
Elymus trachycaulus
Yarrow
Achillea millefolium
a
Annual ryegrass
Lolium multiflorum
Alfalfaa
Medicago sativa
Foxtail barley
Hordeum jubatum
Nuttall's alkaligrass
Puccinellia nuttalliana
Timber Oatgrass
Danthonia Intermedia
Big sagebrushb
Artemisia Tridentata
a
b
agronomic species; nurse plant

Type
Seeded
Seeded
Seeded
Seeded
Cover crop
Cover crop
Volunteer
Volunteer
Volunteer
Nurse plant

Functional group
Native graminoid
Native graminoid
Native graminoid
Native forb
Agronomic graminoid
Agronomic legume
Native graminoid
Native graminoid
Native graminoid
Native shrub

Sage
9.4
18.9
5.6
4.8
23.3
1.1
8.3
8.8
0.1
19.8

No
Sage
11.6
34.3
4.6
3.1
29.4
1.6
7.4
8.0
0.0
0.0

Relative Cover (%)
Cover No cover
crop
crop
Compost
3.4
18.2
10.6
16.6
37.4
24.7
3.3
7.1
4.5
2.5
5.5
4.0
50.5
0.0
30.1
2.5
0.0
1.6
7.5
8.1
6.1
4.8
12.3
8.8
0.1
0.0
0.1
8.7
11.4
9.7

Compost
-ash mix
10.5
28.3
5.8
3.9
22.7
1.1
9.5
8.1
0.0
10.2

67

Table 3.6. Results of 3-way ANOVA looking at the effects of nurse plants (sage/no sage), seed type (cover crop/no cover crop) and soil amendments (compost
only/compost+ash) on vegetation parameters of study plots at the Historic Afton Tailings Storage Facility.
Nurse
Nurse x
Seed x
Nurse x Seed x
Plant
Seed
Amendment Nurse x Seed
Amendment
Amendment
Amendment
Block
PPPPPPPPBiotic
F
value
F
value
F
value
F
value
F
value
F
value
F
value
F
value
Environment
Plant
Productivity
Plant biomassa
3.30
0.091* 2.49 0.137 0.06 0.804 0.54 0.474 0.42
0.527
0.09
0.772
0.91
0.357
0.26
0.776
b
Total cover
10.5
0.353
0.07
0.788
4.16
0.061
3.70
0.051
0.006 3.32 0.090 0.15 0.707 0.04 0.836 0.92
Native graminoid
cover
8.43
0.931
1.59
0.227
1.08
0.317
0.09
0.918
0.012 42.3 <0.01 1.21 0.289 4.89 0.044 0.01
Native forb cover
1.22
0.288 2.79 0.117 0.00 0.978 1.22 0.288 0.35
0.562
0.29
0.599
1.35
0.265
0.79
0.471
Volunteer cover
0.15
0.704 1.52 0.238 0.34 0.567 0.33 0.578 0.00
0.981
0.02
0.877
0.27
0.611
1.69
0.221
P. spicata cover
0.41
0.530 20.1 0.001 0.01 0.944 0.81 0.383 0.01
0.944
0.22
0.644
0.06
0.811
1.26
0.313
Poa spp. cover
10.5
0.709
0.14
0.709
0.91
0.357
0.24
0.786
0.006 16.0 0.001 0.91 0.357 5.22 0.039 0.14
E. trachycaulus
cover
0.47
0.503 4.74 0.047 0.84 0.375 0.64 0.436 0.47
0.503
5.79
0.12
0.736
3.37
0.064
0.031
Plant community
diversity
Species richness
1.22
0.288 14.9 0.002 0.30 0.590 2.74 0.120 0.30
0.590
0.00
1.000
1.22
0.288
Shannon (H)
1.67
0.217 0.20 0.663 1.49 0.242 4.58 0.050 0.48
0.501
0.76
0.397
1.05
0.322
Simpson (D)
1.53
0.237 2.18 0.162 1.52 0.238 5.68 0.032 1.24
0.284
0.54
0.475
0.65
0.435
a
b
Bolded values are significant at 5% probability level; Significant at 10% probability level; Excludes Artemisia tridentata nurse plant

0.30
1.57
1.67

0.742
0.243
0.224

68

69

Figure 3.12. Total plant cover (left) and aboveground plant biomass (right) with and without Artemisia
nurse plants. Error bars are standard error of the mean. Treatments with different letters are statistically
different at the 5% probability level.

Figure 3.13. Native graminoid cover (left) and Poa spp. cover (right) response to nurse plant/cover crop
treatments. Error bars represent standard error of the mean. Treatments with different letters are
statistically different at the 5% probability level.

Figure 3.14. Effect of agronomic cover crops on Pseudoroegneria spicata cover (left) and effect of cover
crops/soil amendments on Elymus trachycaulus cover. Error bars represent standard error of the mean.
Treatments with different letters are statistically different at the 5% probability level.

70
Table 3.7. Correlation matrix showing Pearson correlation statistics and P-values for relationships
between sagebrush abundance parameters and vegetation parameters of study plots at the Historic Afton
Tailings Storage Facility.
Biotic Environment
Plant productivity
Plant biomass*
Total cover*
Native gramnoid cover
Native forb cover
Volunteer cover
P. spicata cover
Poa spp. cover
E. trachycaulus cover

Canopy Volumea
Pearson P-value

Biomassb
Pearson P-value

Canopy Areac
Pearson P-value

Canopy Coverd
Pearson P-value

-0.52
-0.09
-0.31
-0.22
0.72
-0.52
-0.34
0.27

-0.53
-0.05
-0.24
-0.15
0.75
-0.46
-0.32
0.39

-0.44
0.08
-0.28
-0.19
0.76
-0.54
-0.31
0.37

-0.45
0.08
-0.15
-0.04
0.74
-0.36
-0.25
0.44

0.081
0.786
0.323
0.496
0.008
0.082
0.275
0.394

0.079
0.869
0.454
0.638
0.005
0.132
0.314
0.208

0.150
0.796
0.386
0.564
0.004
0.070
0.321
0.232

0.141
0.795
0.647
0.901
0.006
0.247
0.437
0.149

Plant community
diversity
Species richness (S)
0.11
0.725
0.11
0.729
0.17
0.591
0.10
0.746
Shannon index (H)
0.21
0.506
0.27
0.402
0.20
0.532
0.27
0.404
Simpson index (D)
0.24
0.445
0.28
0.373
0.21
0.503
0.29
0.353
Bolded values are significant at the 5% probability level. *Excludes Artemisia tridentata nurse plant.
a
sagebrush canopy elliptical volume; bsagebrush aboveground biomass; csagebrush horizontal canopy
area; d sagebrush canopy cover

71

Figure 3.15. Relationship between volunteer species cover and sagebrush abundance parameters a)
canopy elliptical volume, b) aboveground biomass, c) horizontal canopy area and d) canopy cover.

Figure 3.16. Effect of cover crops on species richness (left) and effect of nurse plant/cover crops on
Simpson’s diversity index (right). Error bars represent standard error of the mean. Treatments with
different letters are statistically different at the 5% probability level.

72

DISCUSSION
Effect of Nurse Plants on Abiotic and Biotic Parameters
Artemisia nurse plants lowered mean daily soil temperature of the study plots by only a
small margin (0.3 °C) during the early months of the growing season (April – May). When
investigating a time course over the hottest day in May, it was found that soil temperatures under
nurse plants were up to 2 °C cooler than in the exposed location. The lower soil temperatures
under nurse plants can attributed to shading by shrub canopies, which limited the amount of solar
radiation reaching the soil surface during daylight hours, and may be a critical process for
seedling survival and establishment (Franco and Nobel, 1989; Padilla and Pugnaire, 2009). Since
the nurse plants used in this study were only small, one-year-old seedlings (15-35 cm in height),
the degree of shading was minimal compared to what has been reported in similar environments
under large, adult nurse plants. For example, Franco & Nobel (1989) examined the nurse effects
of various arid shrub species in the Sonoran Desert, USA and reported soil surface temperatures
of up to 13.5 °C lower under adult Hilaria rigida plants compared to an exposed location (where
soil surface temperatures reached 71 °C). Another study by Padilla & Pugnaire (2009) in a
Mediterranean semiarid region of Spain found that air temperature averaged about 9 °C lower
underneath the canopy of mature Retama sphaerocarpa shrubs compared to in gaps over a 6-day
period during the summer. It is likely that the effect of shading on the understory soil surface
temperature will become more prominent as the Artemisia canopies grow larger and are able to
provide more shade.
The facilitative effect of nurse plants on soil surface temperature diminished (shifting
from positive to neutral) during the mid to later summer months (June – July). This observation
is consistent with reports of interactions shifting with temporal variations in the environment
(Bruno et al., 2003; Maestre et al., 2009), and could be partially due to the effect of shading by
nurse plant canopies becoming less significant as the understory grasses and other vegetation
developed. Similar to the nurse plants, the established vegetation would have also been able to
modify soil surface temperature by casting shade on the understory, resulting in similar
conditions to the habitat under nurse plants. The observed nurse effect on soil surface
temperature will likely persist further into the growing season in subsequent years as the
Artemisia shrubs mature.

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Whether or not the lower temperatures under nurse plants were beneficial for seedling
survival is arguable because the conditions early in the growing season (when the nurse effect
was observed) were not that extreme. Models of plant-plant interactions suggest that the
magnitude of facilitation increases with abiotic stress (Bertness and Callaway, 1994; Callaway
and Walker, 1997; Maestre et al., 2009). In extreme arid conditions, seedlings can benefit from
the shade under nurse plants because it reduces heat stress and water loss (Franco and Nobel,
1989). However, when conditions are less severe, the positive benefits of shade might be
outweighed by the negative aspects of growing under a shrub canopy such as increased
competition for light, nutrients and water (Padilla and Pugnaire, 2009; Walker et al., 2001). More
detailed measurements of other physical parameters associated with microclimatic amelioration
(e.g. solar radiation, wind speed, air temperature, relative humidity) might have helped to further
explain the facilitative processes under Artemisia shrubs.
It is important to note that shade can have a negative effect if light becomes limiting
(Franco and Nobel, 1989; Padilla and Pugnaire, 2009). However, past field experiments have
shown a large variation in seedling response to shade (Maestre et al., 2003; Padilla and Pugnaire,
2009; Walker et al., 2001). For example, a study by Huber-Sannwald & Pyke (2005) assessed P.
spicata seedling survival under artificial shade and reported higher mortality rates for seedlings
growing under strong shade conditions as opposed to full exposure or moderate shade. This
could also be true for the other grassland species assessed in the current study. Whether or not
shade results in a net facilitative effect on the plant community depends on the degree to which
other interacting variables or combinations of variables are influenced by nurse plants (Walker et
al., 2001). The effect of canopy protection by Artemisia seedlings on the understory
microclimate warrants further investigation.
Contrary to reports of improved water availability near Artemisia shrubs, there was no
indication of nursing success under canopies with regard to soil moisture levels during any of the
months investigated. In fact, there was slight evidence of shrubs having a negative effect on soil
moisture in May and June, as indicated by the weak negative correlation between shrub
abundance and soil moisture levels. The decline in soil water with shrub abundance could likely
be a result of high spring water demand (Drivas and Everett, 1988; Lysne, 2005) coupled with
increased transpiration from the larger canopies. Larger plants would typically have greater leaf
area which would increase transpiration rates during the day (when stomata are open) and lead to

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a loss of water from the system (Cardon et al., 2013; Evans and Black, 1993). It is known that
Artemisia shrubs take advantage of spring moisture (mostly from snowmelt) by allocating
resources to aboveground vegetative growth early in the season, and that growth rates
subsequently diminish in the summer and fall when moisture is more limiting and the plants are
in their reproductive growth phase (Lysne, 2005; McArthur et al., 1998). In a greenhouse study
investigating Artemisia tridentata seedling growth, Booth et al., (1990) reported substantial early
aboveground growth rates which diminished after about 12 weeks into the experiment. The rapid
early growth is believed to be an evolutionary adaptation to drier habitats where summer drought
is common (Booth et al., 1990; Mcarthur and Welch, 1982). The field data suggests that
Artemisia seedlings may exert a competitive effect on neighbors with regard to soil moisture
uptake during the spring, and that this effect increases with canopy size and shrub biomass. This
is consistent with ideas in the literature that increased facilitator size can result in an increase in
the relative strength of competition, especially when ecological conditions are not severe
(Callaway and Walker, 1997; Maestre et al., 2009).
The lack of evidence supporting a positive nurse effect on soil moisture can be attributed
to several factors. Firstly, due to the small size of the nurse plants, the effect of shading was
minimal; therefore, it is possible that evaporation rates at the soil surface were not much different
under shrubs compared to in the open (during early months) or under the established grasses and
other vegetation (during later months). Secondly, the shrubs may not have had adequate time to
develop their root systems because they were only transplanted during the fall prior the study
year; therefore, the contribution of water from hydraulic lifting from deeper soil layers was
probably minimal to negligible. In a field study, Richards & Caldwell (1987) documented
enhanced water availability at the subsurface soils (35-80 cm) of a mature Artemisia tridentata
stand (where rooting depths reached over 2 m) as a result of hydraulic lifting from deeper soil
layers. In the current study, the rooting depth of the transplanted seedlings was limited by the
initial pot size (15 cm) as well as the depth of the study plots (61 cm), and so the soil moisture
near and beyond the bottom of the containers would not have been accessible for root uptake.
Finally, since the study year was a particularly wet year, the facilitative effects of nurse shrubs
may have been less obvious because soil moisture was not as limiting as during a normal
precipitation year. The effect of nurse plants on soil moisture would likely be more prominent
during a drier year (Maestre et al., 2003; Padilla and Pugnaire, 2009) and under mature shrubs

75

(Cardon et al., 2013; Richards and Caldwell, 1987). As the plant root systems mature and are
able to access water from deeper soil layers, hydraulic lifting could become a more significant
factor influencing soil moisture and other important soil resources within the vicinity of
Artemisia shrubs (Cardon et al., 2013; Richards and Caldwell, 1987).
The results suggest that Artemisia seedlings competed for water during the early months
of the growing season but had no effect later in the season when conditions were drier.
Contrarily, nurse canopies had a positive effect on soil temperature during the early months, but
no effect during the later months when temperatures were warmer. This is consistent with
reports of plant-plant interactions (i.e. facilitation vs. competition) shifting over a temporal scale
(in this case, from negative to neutral for soil moisture, and from positive to neutral for soil
temperature) in response to changes in nurse plant physiology and growth stage (Maestre et al.,
2003; Pugnaire et al., 1996) and across an abiotic stress gradient (Maestre et al., 2009;
Tewksbury and Lloyd, 2001). In semiarid environments, water is often more limiting than light
or nutrients (Casper and Jackson, 1997), therefore it is possible that competition for water early
in the season may be a more important factor determining survivability than the microclimatic
amelioration provided by the nurse canopy.
Several studies have reported facilitation of perennial grasses and other plant species by
shrubs in semiarid ecosystems (Padilla and Pugnaire, 2006). In these areas, the facilitative
mechanisms within the vicinity of shrubs are often associated with resource enhancement (e.g.
improved soil fertility and water retention) (Moro et al., 1997), microclimatic amelioration (e.g.
reduced temperature and solar radiation levels, increased humidity) (Franco and Nobel, 1989)
and protection from herbivores (Bruno et al., 2003; Ren et al., 2008). Cavieres & Badano (2009)
demonstrated that these positive plant-plant interactions can improve the fitness of individuals of
certain species and lead to an overall increase in species diversity at the community level. The
results of the current study are in agreement with their work, and support the hypothesis that
facilitation by Artemisia nurse plants leads to an increase in species diversity.
Shrubs had a positive effect on the Simpson’s diversity index (D) (although this effect
also depended on whether cover crops were planted with nurse plants). The combination of nurse
plants without cover crops yielded the highest D value, and the treatment with nurse plants and
cover crops yielded the lowest. This indicates that, in the absence of competition from cover
crops, Artemisia shrubs facilitated the establishment of a more diverse ecological community.

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One explanation for the increased diversity under nurse plants could be due to the increase in
volunteer species cover. Relative cover of Puccinellia nuttalliana, Danthonia intermedia, and
Hordeum jubatum were all higher on plots with nurse plants and total cover of these three grass
species (grouped together as “volunteer cover”) increased with all of the four measured sage
abundance parameters. It is possible that Artemisia canopies intercepted the wind-dispersed seed
of these colonizer species and facilitated their establishment through climatic amelioration and
other facilitative processes. A study by Moro, Pugnaire, Haase, & Puigdefabregas (1997)
suspected the same mechanism was responsible for increased species richness under Retama
sphaerocarpa canopies in a semiarid region of Spain. The suspected ability of Artemisia shrubs
to intercept wind-dispersed seed of colonizer species and facilitate their establishment could lead
to the formation of fertile shrub islands (i.e. islands of fertility) over time (Moro et al., 1997;
Walker et al., 2001) which can aid in the natural recovery of disturbed grassland ecosystems. The
increased species diversity under nurse plants is an important finding because plant communities
with high diversity generally have greater ecosystem functionality and so they are more resilient
to environmental perturbations (Callaway and Walker, 1997; Cavieres and Badano, 2009).
Both plant biomass and total plant cover were lower under shrub canopies compared to in
the open. This could be a direct result of belowground competition (for water and nutrients) with
the shallow, fibrous roots of the Artemisia plants limiting the growth of the understory plant
species. In a field study, Huber-Sannwald & Pyke (2005) reported an overall increase in
Pseudoroegneria spicata biomass under Artemisia canopies when seedlings were planted in rootexclusion tubes, which suggested that root interactions between nurse plant and associated
species can limit seedling growth. Competition for water increases when both the nurse plant and
the target species have shallow rooting systems and when there are differences in water potential
between nurse and target species (Franco and Nobel, 1989). The belowground competition
between Artemisia and neighbors is likely to be greater when the shrubs are in their seedling
phase because the rooting zone is co-occupied by both species (Maestre et al., 2003). The species
that are most able to benefit from the interaction with a nurse plant are those that can withstand
the negative effects of root interference (Liancourt et al., 2005). As the shrubs develop deeper
root systems, belowground root competition with associated species is expected to decrease
because the respective rooting systems will each occupy their own niche within the soil profile.

77

Evidence of such a phenomenon was observed in a study by Moro et al., (1997) who reported
that plant biomass was higher under mature shrubs compared to younger, immature shrubs.
When analyzing by plant functional group, native gramnoid cover was highest when
nurse plants and cover crops were excluded and lowest when cover crops were included. When
looking at individual species, Poa spp. cover followed a similar trend. Poa spp. were also the
most dominant of the native grass species on all plots. This could be because the Poa species
planted are known to be tolerant of alkaline conditions (Dobb and Burton, 2013). Despite Poa
spp. performing well on the tailings, the results suggest that belowground competition from
nurse plants and cover crops can limit their establishment on the amended tailings.

Effect of Agronomic Cover Crops on Abiotic and Biotic Parameters
Despite high germination in the greenhouse (see Appendix A), the establishment success
of Medicago sativa in the field was limiting; therefore, the other agronomic species, Lolium
multiflorum, can be considered the main driver of the observed changes in abiotic and biotic
parameters with cover crops. The agronomic cover crop had a minor effect on soil temperatures
in June. Increased shade under the vigorous cover of L. multiflorum can explain why soil
temperatures were lower compared to plots planted with slower-establishing native grasses. Choi
& Mohan, (1995) suspected that improved microclimatic conditions under a similar cover crop,
Panicum virgatum, facilitated the establishment of later successional native species on an iron
mine tailings site in New York, USA.
Soil moisture levels during the months of June and July were lower on plots seeded with
cover crops compared to those without. This finding suggests that Lolium multiflorum competed
for soil moisture during the drier months of the growing season. The competitive abilities of L.
multiflorum in terms of its rapid growth and resource acquisition rates have been demonstrated
(Tribouillois et al., 2014). In June, soil moisture depended on an interactive effect involving
cover crops and soil amendments, with the compost-cover crop treatment having the lowest
moisture levels. This could be because improved nutrients on the compost-amended plots (see
Chapter 2) led to enhanced belowground growth and increased plant water uptake.
Cover crops interacted with nurse plants to influence the Simpson diversity (D) index.
Species diversity values on plots with cover crops and no nurse plants was statistically similar to
the values for plots with nurse plants and no cover crops. This finding indicates that cover crops

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may also be an important facilitative tool for long-term grassland recovery. A study by Choi &
Mohan, (1995) determined that the annual grass Panicum virgatum facilitated natural
colonization of an iron mine tailings site in eastern USA by capturing wind-blown seed of woody
species from surrounding areas and acting as a “nurse crop” during establishment. In their study,
P. virgatum cover decreased substantially after several years, giving way for the colonized native
species to dominate the plant community. It is possible that the same mechanism (capturing of
volunteer seed) is responsible for the improved species diversity with Lolium multiflorum. A
longer term study is needed to investigate how L. multiflorum influences grassland plant
community dynamics over time.
The agronomic cover crop (dominated by Lolium multiflorum) inhibited the growth of
native gramnoid species Pseudoroegneria spicata, Elymus trachycaulus and Poa spp. Previous
field studies of grassland restoration have shown that non-native annual grasses can exert
“priority effects” (competitive advantages of early-growing species) that reduce the growth of
native perennial grasses both in the short- and long-term, and that can play a major role in
determining future plant community composition (Fukami et al., 2005; Grman and Suding, 2010;
Plückers et al., 2013). In the short-term, these effects are primarily a result of agronomics
outcompeting native species by germinating and growing more rapidly, but in the long term, soil
legacies (alteration of soil physiochemical conditions such that growth of other species is
inhibited) can play a major role (Grman and Suding, 2010; Viall et al., 2014). The greenhouse
results (Appendix A) coupled with the field data suggest that strong priority effects exhibited by
L. multiflorum are driving the observed reduction in native species cover on plots seeded with
agronomics.
The species that had moderate germination success in the greenhouse did not perform
well in the field. While germination rates of Festuca campestris, Koeleria macrantha, and
Gaillardia aristata ranged from 60 to 80% in the greenhouse (see Appendix A, Figure A.2.),
none of these species were observed on any of the study plots in the field. This suggests that
species establishment on the amended tailings may have been limited by competition from the
faster-growing species such as Lolium multiflorum and Pseudoroegneria spicata, and that some
of the native grasses are also capable of exerting priority effects that limit the establishment of
other native species.

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The physical data suggests that competition for water (from both cover crops and nurse
plants) may be one mechanism explaining the reduction in native species productivity on the
treatment plots. Studies have shown that native bunchgrasses are sensitive to below-ground
competition from other grasses (Herron et al., 2001) and shrubs (Huber-Sannwald and Pyke,
2005) until they can establish a mature root system (Cline et al., 1977). A longer term study is
needed to determine whether the annual cover crop will persist, or whether native perennials will
eventually take over. A study by Skousen & Venable (2008) assessing native species
establishment on highway roadsides determined that competition from agronomic cover crops
was most intense during the first year of reclamation, but that co-seeded native grasses were able
to increase in subsequent years. Contrarily, another study assessing priority effects during dry
acidic grassland restoration observed that plant community composition four years after seedling
was similar to that of the initial seed mixtures (Plückers et al., 2013).
The results obtained in the current study contradict those reported by Espeland & Perkins,
(2013) who found that the agronomic cover crop Avena sativa did not inhibit early growth of
perennial grasses including Elymus trachycaulus (which was also used in this study). In the
current study, it is possible that the improved nutrients on the compost-amended tailings led to
enhanced growth and subsequent competition by Lolium multiflorum, which in turn reduced E.
trachycaulus cover. Grman & Suding (2010) suggested that seeding native species prior to the
establishment of agronomics could increase restoration success. Doing so would allow the
practitioner to benefit from the short-term practical uses of cover crops (e.g. erosion control,
aesthetics, nutrient retention, invasion resistance) while the perennial grass community develops
over time.

CONCLUSION
The results of the field study provide several important considerations for mine
restoration practices in B.C.’s interior semiarid grasslands. The presence of Artemisia nurse plant
seedlings improved microclimatic conditions by reducing soil surface temperature early in the
growing season, but there was some evidence of a competitive effect with regard to soil water
usage in the spring. This study did not assess other environmental parameters, such as air
temperature, solar radiation, relative humidity and wind speed under nurse canopies, and so it is
difficult to ascertain whether the young Artemisia plants had a net facilitative effect on the

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understory abiotic environment. It is suspected that belowground competition with shrubs led to
an overall decrease in grassland species cover and biomass. This effect is expected to diminish as
nurse plant roots develop and become capable of extracting water from deeper soil layers.
Furthermore, species diversity responded positively to nurse plants indicating that some
facilitative mechanisms are at work. These mechanisms may promote the formation of “islands
of fertility” around Artemisia shrubs over time due to enhanced productivity and subsequent
buildup of organic matter. Given the short duration of this study, the influence of nurse plants on
soil physiochemical parameters was not assessed. A longer term study would reveal more insight
into the facilitative processes taking place within the vicinity of Artemisia shrubs. The influence
of nurse plants on the parameters investigated should increase as the shrubs grow and mature.
The hypothesis that cover crops would impede native species diversity was not
supported. The plots planted with nurse plants had the highest diversity, but those seeded with
cover crops were statistically similar. Despite high germination success in the greenhouse,
Medicago sativa establishment was not successful in the field, and therefore this species was
only a minor component of the agronomic cover crop. Competition from Lolium multiflorum
with the native perennials at the onset of reclamation resulted in a strong priority effect after the
first year. A longer term study is needed to assess whether the competitive effects of L.
multiflorum will persist or whether native perennial grass cover will improve over time.
Despite a negative response to the wood ash amendment in the greenhouse (see Chapter
2), plant performance did not appear to be affected in the field. The two soil amendment
treatments were statistically similar to one another with regard to the abiotic parameters
investigated in the field. The addition of soil amendments reduced the bulk density of the tailings
by almost twofold, which shows that these materials can be useful for addressing some of the
physical limitations of mine tailings. An interactive effect between soil amendments and cover
crops resulted in lower cover of Elymus trachycaulus, likely because the improved soil
conditions with the compost-amended tailings led to increased competition from the fastgrowing agronomic annual, Lolium multiflorum.
The results of the study suggest that Artemisia nurse plants are a promising tool for native
grassland recovery on mine tailings under the circumstances tested. Although the agronomic
cover crop treatment increased total biomass, the emergence of key native grass species was
inhibited which indicates that cover crops are less useful for grassland recovery on mine tailings.

81

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CHAPTER 4 – RESEARCH CONCLUSIONS, MANAGEMENT
IMPLICATIONS AND FUTURE RESEARCH
RESEARCH CONCLUSIONS
The natural habitats and ecosystems within British Columbia’s interior semiarid
grasslands have been altered by human activities such as urban development, mining, and
agriculture. Conservation and restoration of these grasslands is important because they offer a
wide array of ecological and economic benefits including biodiversity, wildlife habitat, water
filtration, and carbon storage (Wilson, 2009). Traditional restoration practices involved seeding
degraded land with fast-growing agronomic species, but more recently, the importance of reestablishing pre-existing native plant communities and biodiversity is increasingly being
recognized (Burton and Burton, 2002; Skousen and Venable, 2008). Mine tailings, however, are
not an ideal growing medium for native plants because they tend to lack the physiochemical and
biological attributes of a native soil (Gardner et al., 2010; Pepper et al., 2013). Restoration in arid
and semiarid environments can be especially challenging because extreme temperatures and
desiccation threaten seedling survival (Padilla and Pugnaire, 2006). Successful development of
native grassland communities on such sites depends on the ability of practitioners to manipulate
the abiotic environment such that it is more favourable for plant growth (Pueyo et al., 2009) and
reconstruct natural ecological processes such as soil and plant succession (Bradshaw, 1997). The
aim of this thesis was to investigate the efficacy of a variety of restoration practices including 1)
the use of locally available soil amendments for improving tailings physiochemical conditions,
2) remediation of metals and other contaminants through phytostabilization, and 3) facilitation of
native grassland species with nurse plants and cover crops. These methods were assessed though
a two-part study involving a one-year field study at the Historic Afton Tailings Storage Facility
(TSF) and a three-month greenhouse experiment at the Thompson Rivers University Research
Greenhouse in Kamloops, B.C.

Greenhouse Study
The objectives of the greenhouse experiment were to 1) investigate the suitability of two
native, semiarid bunchgrasses (Pseudoroegneria spicata and Festuca campestris) for

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phytostabilization of the historic Afton tailings, and 2) to assess the effect of soil amendments on
soil physiochemical attributes and plant productivity.

Key Findings of Greenhouse Study:


Compost improved native bunchgrass productivity on the amended tailings

A study by Piorkowski et al., (2015) emphasized the economic and ecological importance of
using locally available soil amendments for soil reclamation. I was interested in determining the
most effective amendment mixture – in terms of plant growth response – of the locally available
materials at hand. The results of the greenhouse study determined that, of the three soil
amendments investigated, the City of Kamloops municipal yard waste compost was the most
effective at increasing aboveground and belowground biomass and shoot heights of native
bunchgrasses Pseudoroegneria spicata and Festuca campestris. Contrarily, the Domtar wood ash
appeared to have a negative effect on productivity, as I found that increasing the relative amount
of ash in the amendment mixture produced shorter seedlings with lower overall biomass.


Pseudoroegneria spicata (bluebunch wheatgrass) and Festuca campestris (rough
fescue) are not suitable candidates for phytostabilization of the historic Afton
Tailings

The objective of phytostabilization is to promote the growth of plant species that can stabilize
metals in the rhizosphere while limiting shoot uptake (Mendez and Maier, 2008, 2007). The
translocation factor (ratio of shoot elemental concentration-to-root elemental concentration) is a
useful metric for determining species suitability. Both grass species assessed had TF values of >1
for molybdenum and zinc which indicates that these species are “hyper-accumulators” of these
metals and therefore are not suitable candidates for phytostabilization of the historic Afton
tailings because excess amounts of these metals can be toxic to wildlife and domestic animals.

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Field Study
The objectives of the field study were to assess 1) whether Artemisia tridentata seedlings
can be used as nurse plants to facilitate native grassland species establishment, 2) if agronomic
cover crops benefit or impede native plant community development, and 3) the effect of soil
amendments on revegetation success.

Key Findings of Field Study:


Artemisia tridentata nurse plants facilitated the establishment of a more diverse
grassland plant community

Studies have shown that, under adverse ecological conditions, certain shrubs called nurse
plants can facilitate the establishment of neighbouring plants through a variety of mechanisms
including abiotic amelioration, resource enhancement, and protection from herbivory (Bruno et
al., 2003; Padilla and Pugnaire, 2006), and that this process can lead to an overall improvement
in plant community diversity (Cavieres and Badano, 2009). I was interested in determining
whether Artemisia tridentata seedlings were capable of facilitating the establishment of a more
diverse grassland plant community on the mine tailings site. The results of the field study
indicated greater plant community diversity under nurse plants which was possibly a result of the
improved microhabitat (e.g. lower temperatures, protection from wind, solar radiation) under A.
tridentata canopies.


Agronomic cover crops had a negative effect on native grassland species
establishment

In agricultural settings, cover crops are useful tools for reducing nitrogen leaching,
preventing erosion, and improving soil organic matter during the fallow period (Espeland and
Perkins, 2013). These fast-growing, annual grasses can also be planted during restoration to
provide quick benefits and improve the abiotic conditions for the slower-growing native species
to establish (Choi and Mohan, 1995; Skousen and Venable, 2008). But in some instances,
agronomics can out-compete native species and sterilize the process of native plant community

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development and succession (Davis et al., 2005; Grman and Suding, 2010). I was interested in
finding out if the agronomic grass species Lolium multiflorum and legume Medicago sativa
facilitate or interfere with native grassland community establishment during early mine
reclamation. The results of the one-year field study indicate that cover crops had a negative
effect on native grassland species productivity and suggest that competition for moisture during
the hot and dry summer months may have been a limitation to native species establishment.

MANAGEMENT IMPLICATIONS & FUTURE RESEARCH
Soil Amendments
Surface mining requires the removal of pre-existing soil and vegetation which often results in
long-term impairment of ecological processes (Bradshaw, 1997; Shrestha and Lal, 2011). The
degraded material (e.g. tailings, waste rock) left behind cannot facilitate plant life or soil
processes because it is low in organic matter and nutrients, and lacks the physical attributes of
well-functioning soils (Gardner et al., 2010; Sheoran et al., 2010). Land application of organic
waste by-products such as compost, wood ash, and biosolids is an effective method for restoring
the soil’s physiochemical attributes and its ability to promote primary production (Larney and
Angers, 2012; Zebarth et al., 1999). These materials are often high in organic matter and include
nutrients such as nitrogen and phosphorous which makes them a good soil amendment for mine
reclamation (Park et al., 2011; Shrestha et al., 2009). Vast quantities of amendments are needed
in order to cover the disturbed surface, and so sourcing locally available industrial waste
materials can reduce transport costs and be more efficient (Piorkowski et al., 2015).
My study assessed three locally sourced organic materials in terms of their potential for use
as soil amendments at the TSF. Of the materials investigated, the City of Kamloops municipal
yard waste compost seemed to have the best qualities and the most noticeable effect on plant
growth, although, further research assessing higher application rates is necessary to determine
the full potential of this amendment. The wood ash – created from “hog fuel” incineration at the
Domtar pulp mill in Kamloops, B.C. – was a less promising product for amending the alkaline
tailings because of its high pH and total aluminum content, which most likely caused the
observed negative effect on plant growth. Because of its high pH, the ash may be a more suitable
amendment for reclamation of acidic mine tailings where it can act as a soil conditioner to buffer
pH levels and limit heavy metal bioavailability (Solís-Dominguez et al., 2012). There were no

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clear effects of wood chips on plant growth, but there were improvements in soil organic matter
and carbon which indicates that this material could be mixed with other amendments as a slowrelease carbon source that can be beneficial in the long term.

Phytostabilization
Phytostabilization is an emerging remediation technology that utilizes a vegetative cap to
prevent the dispersion of toxic metals and other harmful contaminants from tailings and other
mine waste sites (Mendez and Maier, 2008, 2007). A recent study by Solís-Dominguez et al.,
(2012) emphasized that there is currently a lack of information regarding species-specific
performance and suitability for phytostabilization. Information regarding plant tissue metal
accumulation is especially important because revegetated mine sites are often grazed by
livestock and/or wildlife (Schuman et al., 2010; Solís-Dominguez et al., 2012). Suitable species
are those which can tolerate the adverse physiochemical conditions of mine soils while avoiding
shoot uptake of metals.
My study investigated growth responses and plant tissue metal accumulation of two
bunchgrass species native to B.C.’s semiarid grasslands and found that neither species were
promising candidates for phytostabilization of the historic Afton tailings because both species
accumulated high amounts of Mo and Zn in their shoots. In terms of growth and productivity on
the mine tailings, Pseudoroegneria spicata is the better candidate and may still have a use as for
other remediation techniques such as phytoextraction (Mendez and Maier, 2008). With this
technology, shoot uptake is encouraged and plants containing the sequestrated metals are mowed
and subsequently removed from the site, resulting in a reduction in tailings metals concentrations
over time. Some of the other native grassland species that were successful in the field, such as
Poa spp., Elymus trachycaulus and Puccinellia nuttalliana, should also be considered, as they
appeared to perform well on the alkaline tailings. The suitability of other native species that can
tolerate alkaline soils, such as Distichlis spicata and Hordeum jubatum (Porensky et al., 2014;
Robson et al., 2004) should also be investigated.

Nurse Plants
Under extreme ecological conditions, such as in arid and semiarid environments,
facilitation by nurse plants can enhance target species establishment (Franco and Nobel, 1989;

93

Padilla and Pugnaire, 2006). Facilitation between nurse plant and associated species typically
includes some form of habitat amelioration, resource enhancement and/or protection from
grazing that results in a net positive effect on plant establishment (Bruno et al., 2003; Padilla and
Pugnaire, 2006). Recently, facilitation with nurse plants and has been deemed as an appropriate
technique for the restoration of degraded semiarid environments (Maestre et al., 2003; Pueyo et
al., 2009). However, since competition and facilitation occur simultaneously, in some instances,
competitive effects may be stronger than facilitation, resulting in a net interaction that is negative
(Bertness et al., 1999; Padilla and Pugnaire, 2006). Because of this, there is a need to investigate
facilitative mechanisms across a wide range of environments and plant communities (Cavieres
and Badano, 2009; Padilla and Pugnaire, 2009; Pueyo et al., 2009), and to determine which
species (both the facilitator and beneficiary) are appropriate for facilitation in a given system
(Padilla and Pugnaire, 2006).
My study assessed the suitability of a semiarid shrub Artemisia tridentata (big sagebrush)
as a nurse plant for grassland restoration at the TSF. The study revealed that nurse plant canopies
were effective at reducing soil surface temperatures early in the growing season but that
competition for soil moisture with neighbors can potentially outweigh this positive effect.
Nonetheless, nurse plants appeared to successfully promote a more diverse ecological
community which may be a result of canopies intercepting wind dispersed seed from
surrounding plant communities and facilitating their establishment. Soil temperature and soil
moisture were the only abiotic variables assessed, and so further research looking at other
parameters such as wind speed, air temperature and solar radiation, under nurse plants (Padilla
and Pugnaire, 2009) is recommended. It would also be beneficial to plant nurse shrubs with only
one species (rather than an entire community) to determine the specific interactions taking place
between A. tridentata and target grassland species (Huber-Sannwald and Pyke, 2005).
Comparing the environment and biotic responses under nurse plants to artificial shade structures
would also be interesting (Pueyo et al., 2009).

Cover Crops
Because of their wide use in agricultural systems (Espeland and Perkins, 2013;
Tribouillois et al., 2014), there is potential for agronomic cover crops to be used as a tool for
restoration of mine tailings sites. Cover crops (fast-growing agronomic annual grasses and/or

94

legumes) are typically used to provide quick ecological and economic benefits, such as erosion
control, prevention of N leaching, and addition of green manure (i.e. organic matter) which can
make the environment more favourable for the target plant community to establish (Espeland and
Perkins, 2013). However, in some instances, these fast-growing introduced species can
outcompete slower-growing native species and halt the process of ecological succession (Davis
et al., 2005) due to the “priority effects” of being the first to establish (Grman and Suding, 2010;
Plückers et al., 2013). Other studies, however have shown that, given adequate time, native
species can, in fact, establish on sites that have been seeded with agronomics (Espeland and
Perkins, 2013; Skousen and Venable, 2008).
My study investigated the use of Lolium multiflorum and Medicago Sativa as cover crops
for facilitating native grassland species establishment at the TSF. The data suggests that cover
crops (primarily L. multiflorum, as M. sativa establishment was poor) impeded native species
establishment and resulted in the formation of less diverse plant communities after one growing
season. This was likely because the agronomic species exhibited rapid germination and growth
and competition for soil moisture. A longer-term study would be beneficial to determine if these
“priority effects” persist, or whether native species cover will increase with time. As with the
nurse plants, it would also be interesting to assess the interactions between L. multiflorum and a
single target species growing within close proximity to one another.

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Padilla, F.M., Pugnaire, F.I., 2006. The role of nurse plants in the restoration of degraded
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504. doi:10.4141/S98-074

A1

APPENDIX A – SEED GERMINATION TRIAL
INTRODUCTION
Seed dormancy and viability of seed stock are barriers to successful germination of native
seed during restoration projects. Pre-treatments such as mechanical scarification, cold
stratification and application of hormones can break dormancy and improve germination success
in some species (Dobb and Burton, 2013). Gibberellic acid (GA), or Gibberellin is a naturally
occurring plant hormone that stimulates growth of germinating seeds. The use of GA as a seed
treatment has had variable success, depending on the species tested (Çetinbaş and Koyuncu,
2006; Gonzalez-Melero et al., 1997).
During winter 2015, a seed germination trial was conducted at the Thompson Rivers
University Research Greenhouse (Kamloops, B.C.) to test the effects of GA on seed germination
of the native species being used in this study. The objectives of the trial were threefold: 1) to
determine the viability of the native seed stock acquired for the field experiment, 2) to assess the
effects of GA on seed germination of the study species and 3) to compare seed germination
between agronomic and native species.

MATERIALS & METHODS
Experimental Design
Germination rates of the thirteen study species (see Chapter 3, Table 2) were assessed for
two treatments: ‘GA’ and ‘control’. Each treatment was replicated three times (13 species × 2
treatments × 3 replicates = 78). The germination trial was conducted over a 30-day period under
controlled conditions (temperature 21 °C, natural and artificial light, day/night 16 hrs/8 hrs).
Seventy-eight petri dishes (35 mm diameter × 18 mm deep) were lined with filter paper and
labelled by species and treatment. Each dish received 20 seeds of a single species. Petri dishes
were randomly assigned to a single block using “The Random Number Generator” iPhone iOS
application (Nicholas Dean, 2013) (Figure A1). Petri dishes were placed at the centre of the
greenhouse pod (where temperature and lighting were most stable). The filter paper was kept
saturated with either a) 1000 ppm Gibberellic acid solution (GA) (Çetinbaş and Koyuncu, 2006)
or b) deionized water (control), depending on the assigned treatment. The greenhouse pod was
monitored daily and the number of germinated seeds was recorded every second day. Seeds were

A2

considered germinated when the radicle length reached twice the radicle width. The germinated
seeds were removed from the petri dishes once they were counted.

Figure A.1. View of randomized block layout (top left), Festuca campestris seed prior to germinating
(top right), emerging Balsamorhiza sagittata seed (bottom left) and Allium cernuum seed (bottom right).
Treatments were solutions containing either a) 1000 ppm Gibberellic acid or b) deionized water (top left).

Statistical Analysis
Mean germination rates were calculated for each 2-day interval in order to show
cumulative germination over the 30-day trial period. The time to first germination (T0) (Ranal
and Santana, 2006) was recorded for each replicate. Time to 50%

germination (T50) was

calculated by using the equation from Çalişkan et al. (2012):
(𝑁+1)
−𝑛𝑖
2

Τ50 = 𝑡𝑖 [ 𝑛𝑗−𝑛𝑖 ] (𝑡𝑗 − 𝑡𝑖)

[4]

A3

where N is the final number of seeds germinated and ni and nj are the total number of seeds
germinated at time ti and tj (where ni < (N+1)/2 < nj). Two sample t-tests were used to compare
the final germination rates and T50 between treatments for each species. Significances were
accepted at the 5% probability level.

RESULTS & DISCUSSION
Viability of Native Seed
Germination rates of native grasses ranged from 62 to 97%, with Festuca campestris
having the lowest germination and Elymus trachycaulus having the highest after 30 days (Figure
A1). Native forb germination was more variable and ranged from 0 to 87% (Allium cernuum and
Achillea millifollium, respectively) (Figure A2). The native forbs Balsamorhiza sagittata and A.
cernuum were the slowest to germinate (Tables A1 and A2) and final germination rates were low
compared to the other forbs (Figure A2).

Figure A.2 Cumulative germination rates of native grasses over a 30-day greenhouse trial. Error bars are
standard error of the mean. Treatments were a 1000 ppm Gibberellic acid solution (GA) and deionized
water (control).

A4

Figure A.3. Cumulative germination rates of native forbs over a 30-day greenhouse trial. Error bars are
standard error of the mean. Treatments were a 1000 ppm Gibberellic acid solution (GA) and deionized
water (control).

Figure A.4. Cumulative germination rates of agronomic species during a 30-day greenhouse trial. Error
bars are standard error of the mean. Treatments were a 1000 ppm Gibberellic acid solution (GA) and
deionized water (control).

Comparison of Native Species vs. Agronomic Species
The agronomic grass Lolium multiflorum had the highest germination rate (98%) of all
the species examined (Figure A3). The native bunchgrasses Poa secunda, Pseudoroegneria
spicata and Elymus trachycaulus were comparable at 90, 93 and 97%, respectively (Figure A1).
Although, L. multiflorum emergence was much quicker compared to the native grasses (Tables

A5

A1 and A2). The fastest species to germinate was the agronomic legume Medicago sativa. The
native legume Vicia americana was comparably slow (Figure A2). Germination speed of the
pioneer species, Achillea millefolium was similar to the agronomic species.

Effect of Gibberellic Acid on Seed Germination
Depending on the species, treatment with GA solution either hindered, had no effect, or
improved seed germination. The GA treatment had a significant positive effect on emergence of
the native forbs Balsamorhiza sagittata (P=0.010) and Allium cernuum (P=0.016) (Figure A2),
but had a negative effect on both Poa species (P=0.037 and P=0.0005 for Poa secunda and Poa
juncifolia, respectively) (Figure A1). Interestingly, without the GA treatment, A. cernuum seeds
could not break dormancy within the 30-day trial period (Figure A2; Table A2). With regards to
germination speed, GA solution improved the performance of Elymus trachycaulus and B.
sagittata and had no effect on any of the other species (Tables A1 and A2).

Table A.1. Days to first germination (T0) by treatment for each of the study species.
Species
Control
GA
Pseudoroegneria. spicata
<4
<4
Festuca campestris
<6
<6
Poa secunda
<6
<4
Koeleria macrantha
<4
<6
Elymus trachycaulus
<4
<4
Poa juncifolia
<4
<4
Vicia americana
<10
<10
Achillea millefolium
<4
<4
Balsamorhiza sagittata
<14
<10
Gaillardia aristata
<4
<4
Allium cernuum
<12
Lolium perenne*
<4
<4
Medicago sativa*
<2
<2
GA: 1000 ppm Gibberellic acid solution; Control: deionized water.
*Agronomic species

A6
Table A.2. Mean days to 50% germination (T50) ± standard error for each of the study species
and two-sample t-test results comparing means between treatments.
P-value
Species
Control
GA
(t-test)
Pseudoroegneria spicata 3.8 ± 0.07
4.0 ± 0.34
0.583
Festuca campestris
10.3 ± 0.36
9.3 ± 0.33
0.121
Poa secunda
6.7 ± 0.99
6.6 ± 1.04
0.976
Koeleria macrantha
5.2 ± 0.23
5.5 ± 0.73
0.702
Elymus trachycaulus
5.1 ± 0.30
3.7 ± 0.17
0.016
Poa juncifolia
4.7 ± 0.41
3.6 ± 0.23
0.078
Vicia americana
10.3 ± 0.59
10.8 ± 1.24
0.761
Achillea millefolium
3.1 ± 0.00
3.1 ± 0.03
0.444
Balsamorhiza sagittata
24.8 ± 2.20
15.7 ± 0.69
0.017
Gaillardia aristata
4.7 ± 0.58
3.5 ± 0.24
0.121
Allium cernuum
17.8 ± 3.32
Lolium perenne*
3.1 ± 0.03
3.1 ± 0.02
0.433
Medicago sativa*
1.6 ± 0.03
1.6 ± 0.02
0.564
GA: 1000 ppm Gibberellic acid solution; Control: deionized
water. Bolded values are statistically significant (P < 0.05).
*Agronomic species

SUMMARY/CONCLUSIONS


The agronomic species were quicker to germinate compared to the native species.



Germination rates of the native bunchgrasses Poa spp., Pseudoroegneria spicata and
Elymus trachycaulus were similar to the agronomic grass Lolium multiflorum.



Treatment with Gibberellic acid improved germination success of Balsamorhiza
sagittata, Allium cernuum and Elymus trachycaulus, but hindered Poa spp. seed
emergence.



The effects of Gibberellic acid on seed germination were variable and appeared to be
species dependent; seed size and seed coat thickness may be a factor.

A7

LITERATURE CITED
Çalişkan, O., Mavi, K., Polat, A., 2012. Influences of presowing treatments on the germination
and emergence of fig seeds (Ficus carica L.). Acta Sci. Agron. 34, 293–297.
doi:10.4025/actasciagron.v34i3.13392
Çetinbaş, M., Koyuncu, F., 2006. Improving germination of Prunus avium L . seeds by
gibberellic acid , potassium nitrate and thiourea. Hortic. Sci. 33, 119–123.
Dobb, A., Burton, S., 2013. British Columbia rangeland seeding manual. Ministry of
Agriculture, Victoria, BC.
Gonzalez-Melero, J., Perez-Garcia, F., Martinez-Laborde, J., 1997. Effect of temperature,
scarification and gibberellic acid on the seed germination of three shrubby species of
Coronilla L. (Leguminosae). Seed Sci. Technol. 25, 167–175.
Ranal, M. a., Santana, D.G. De, 2006. How and why to measure the germination process? Rev.
Bras. Botânica 29, 1–11. doi:10.1590/S0100-84042006000100002

B1

APPENDIX B – LABORATORY ANALYTICAL RESULTS
Table B.1. Elemental concentrations of experimental materials and federal soil quality guidelines.
Ash

Substrate
Compost

Tailings

1967
<2
< 3.0
27.2
1225
35594
< 1.0
25.7
51.8
70.7
486
<3
10.7
3888
680.1
3.15
3897
30.9
< 1.0
918
6.0
9.74
43
<2
509
1864
<6
53.8
8.00
216.0
84.9

828
<2
< 3.0
8.9
475
9793
< 1.0
16.9
52.2
77.9
545
<3
10.7
1775
83.8
3.81
597
26.1
6.6
452
< 3.0
8.49
177
<2
225
2096
<6
58.0
8.17
105.9
81.2

75
<2
< 3.0
< 1.0
492
4770
< 1.0
30.8
138
600
525
<3
8.4
706
23.7
10.5
712
90.7
< 1.0
977
6.1
11.2
213
<2
365
2993
<6
180
14.0
19.6
55.4

20
12
2
1.4
40
64
63
6.6
5
45
70
1
200
-

40
12
22
300
87
91
60
40
89
600
2.9
360
-

0.05
0.47
2.49
0.15
22.5

1.18
0.30
1.32
0.21
24.3

0.01
0.11
1.09
0.26
1.12

-

-

NO3-N

19.7

35.1

1.22

-

-

NH4-N

< 0.01

6.31

0.78

-

-

Element
Main Elements (mg kg-1)
Al
Ag
As
B
Ba
Ca
Cd
Co
Cr
Cu
Fe
Hg
Li
Mg
Mn
Mo
Na
Ni
Pb
S
Sb
Se
Si
Sn
Sr
Ti
Tl
V
Y
Zn
Zr
Total Plant Nutrients (%)
N
P
K
S
C
Available Nutrients (mg/kg)

Soil Quality Guideline*
CCME ALa
CCME ILb

*Canadian Council of Ministers of the Environment Soil Quality Guidelines for a Agricultural Land Use
and b Industrial Land Use (Canadian Council of Ministers of the Environment, 2014).