soil seed bank dynamics in transferred topsoil...soil seed bank dynamics in transferred topsoil...

SOIL SEED BANK DYNAMICS IN

TRANSFERRED TOPSOIL EVALUATING RESTORATION POTENTIALS

William M. Fowler

Thanks to my supervisors Dr. Joe Fontaine and Prof. Neal Enright for all the advice and support given over the last year. I would also like to thank the members of the Murdoch University, Terrestrial Ecology Research Group (TERG) for their valuable assistance and guidance, especially Willa Veber and Dr. Philip Ladd, as well as the Murdoch University Environmental Science Association (MUEnSA) for helping find enthusiastic volunteer field assistants. I wish to thank the Department of Environment and Conservation (DEC) for providing technical and financial assistance in addition to information and resources that were vital to this projects success. Finally I would like to thank the Environmental Weeds Action Network (EWAN) for awarding me a scholarship to help me complete this valuable research.

Bachelor of Science in Environmental Science and Environmental Restoration

School of Environmental Science

October 2012

Acknowledgements

DECLARATION

I declare that this thesis is my own original work and has not been submitted for any

other unit for academic credit.

William Michael Fowler

Soil seed bank dynamics of transferred topsoil: evaluating restoration potentials

iii

ABSTRACT

Global change, increasing human population growth and urbanisation represent

increasing pressures on biodiversity and ecosystem function. It is now widely

recognised that conservation of existing natural fragments will not be sufficient to

maintain extant biodiversity or meet conservation goals. Thus there is a major and

rapidly expanding need for the practice of ecological restoration whereby degraded

lands are managed to increase and maintain indigenous species.

A soil seed bank germination experiment was conducted over a period of 13

weeks. This aimed to evaluate restoration values of topsoil transfer, by investigating soil

seed bank similarity to standing vegetation, and exploring mechanisms to improve

restoration outcomes on the Swan Coastal Plain, Western Australia. This was

experimentally designed to make comparisons between the soil seed bank pre and post-

transfer, an aspect of topsoil transfer that has not been looked at previously. In addition

sampling was conducted at two depths, with treated (smoke and heat) and non-treated

trials. This study examined the similarity of the soil seed bank to standing vegetation,

the effect of soil transfer, and the influence of soil spreading depth and fire related

germination cues.

Seventy-three per cent of germinants were found in the top 5 cm of natural (pre-

transfer), soil transfer leading to mixing (no depth effect) and a reduction in germinant

densities (-2472.00 germinants m-2). Treatment with germination cues (heat and smoke

in concert) increased germinant densities by 1537.80 germinants m-2, however no

increase in transferred soils was observed. Native annuals dominated species

composition of transferred soils, contributing 68% of observed richness, with woody

species only accounting for 9% overall. The similarity of the soil seed bank to the

standing vegetation ranged from 15% to 19%, the higher similarity found when

treatment was used. Overall topsoil transfer is a useful tool for restoration; however it

must be used in conjunction with other methods, such as planting and direct seeding, to

return a representative set of species to a site.


iv

TABLE OF CONTENTS

DECLARATION .................................................................................................................. II

ABSTRACT ....................................................................................................................... III

TABLE OF CONTENTS ....................................................................................................... IV

LIST OF FIGURES .............................................................................................................. VI

LIST OF TABLES .............................................................................................................. VII

CHAPTER 1 – INTRODUCTION ........................................................................................... 1

1.1 RESEARCH AIMS ............................................................................................................. 5

1.2 THESIS OUTLINE ............................................................................................................. 6

CHAPTER 2 – STUDY AREA AND METHODS ........................................................................ 7

2.1 STUDY SETTING .............................................................................................................. 7

2.2 FIELD SAMPLING AND DATA COLLECTION ............................................................................... 9

CHAPTER 3 – RESULTS .................................................................................................... 18

3.1 SEED BANK DYNAMICS ................................................................................................... 18

3.2 SIMILARITY .................................................................................................................. 27

3.3 COMMUNITY ANALYSIS .................................................................................................. 27

CHAPTER 4 - DISCUSSION ............................................................................................... 31

4.1 INFLUENCE OF DEPTH OF TOPSOIL ON RESTORATION OUTCOMES ............................................... 31

4.2 THE EFFECT OF TOPSOIL TRANSFER ON GERMINANT COMPOSITION ............................................ 34

4.3 GERMINATION SIMULATION WITH COMMON GERMINATION CUES ............................................. 34

4.4 SOIL SEED BANK AND ITS RELATIONSHIP TO THE STANDING VEGETATION ..................................... 35

CHAPTER 5 – CONCLUSIONS AND RECOMMENDATIONS .................................................. 38


v

5.1 CONCLUSIONS .............................................................................................................. 38

5.2 RECOMMENDATIONS FOR MANAGEMENT OF TOPSOIL TRANSFER ON THE SWAN COASTAL PLAIN ...... 38

5.3 RECOMMENDATIONS FOR FUTURE RESEARCH ....................................................................... 39

REFERENCES .................................................................................................................. 40

APPENDICES .................................................................................................................. 50

APPENDIX A – STATISTICAL SUMMARIES OF ALL NORMAL PARAMETRIC ANALYSIS ............................... 50

APPENDIX B – SPECIES LISTS ................................................................................................. 51


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LIST OF FIGURES

Figure 1 – Diagramatic representation of the change in seed gradient as a result of mixing due to the

transfer process. ........................................................................................................................ 5

Figure 2 – Site locations relative to Perth, Western Australia. The cross indicating the location of

Jandakot Airport from which soil was striped. Triangles indicating the recipient sites of

Forrestdale Lake and Anketell RD. Adapted from the Nokia map service (Nokia 2012). ............ 8

Figure 3 - Position of transects and plots at Jandakot Airport. The area which soil was stripped from

is enclosed by the solid black lines. Plots are represented by the dots; with series of dots

forming transects which are labelled accordingly. ................................................................... 10

Figure 4 - Main: Image of the loader used to harvest topsoil from Jandakot Airport by Urban

Resources. Insert: side view of the wing-like bucket modifications used to prevent over

harvesting of topsoil. ............................................................................................................... 11

Figure 5 – Site and plot locations at Forrestdale Lake. Dots representing plots, clustered in the deep

areas of transferred soil at the three smaller sites within the greater area of Forrestdale Lake

(Nature Reserve). .................................................................................................................... 11

Figure 6 – Site and plot locations and Anketell Road. Dots representing plots, clustered in the deep

areas of transferred soil at the three smaller sites within the greater Anketell Rd site. ........... 12

Figure 7 - Diagram of the soil sampling tube (not to scale) used for sampling topsoil in this study. . 12

Figure 8 – Sampling arangement within each plot (not to scale), the circles representing the

locations of soil samples which were composited. .................................................................. 12

Figure 9 – Diagram of seeding marking procedure, bands indicating colour code progression as

identification became more developed. .................................................................................. 15

Figure 10 – Proportion of total germinants the study over time (weeks). ........................................ 18

Figure 11 – Mean germinants m-2

by treatment across depth and site. ............................................ 19

Figure 12 – Mean species richness by treatment across depth and site. .......................................... 20

Figure 13 – Diversity using the Shannon-Wiener index, by treatment across depth and site. .......... 21


by treatment, across depth and site, comparing growth forms. .. 22


of invasive species and native species split into longevity

categories, across treatment and depth (unknown species removed). .................................... 23

Figure 16 – Density of native perennial species and their proportion of woody and non-woody. .... 25

Figure 17 – Density of germinants m-2

of seeders and resprouters across treatments, depths and

sites. ........................................................................................................................................ 26

Figure 18 – Mean density germinants m-2

of categories of Proteoid roots (0=0, 1=0-25%, 2=25-50%,

3=50-75%, 4=75-100%). ........................................................................................................... 26

Figure 19 – Ordination of all trays using NMS. Axis 1 correlated with site, from transfer to natural.

Axis 2 correlated with depth, 5-10cm to 0-5cm. ...................................................................... 28

Figure 20 – Panel of three joint plot analyses, with correlations. A – Growth form and invasive

status, B – Richness and diversity, C – species. Only those vectors with r2 values > 0.20 are

displayed. ................................................................................................................................ 29

Figure 21 – Graphical representation of the potential influence of compaction in the soil stripping

process. Effect of over harvesting is for illustrative purposes only........................................... 32

Figure 22 – Photo of proteoid roots on site at Jandakot Airport. ...................................................... 33


vii

LIST OF TABLES

Table 1 – Criteria used by DEC and their relative importance in recipient site selection. Adapted

from Brundrett (2012). .............................................................................................................. 9

Table 2 – Ranking system for the allocation of cover rankings consistent with Braun-Blanquet

(1932). ..................................................................................................................................... 10

Table 3 - Top 5 species by abundance for each treatment on natural and transferred soils. Blanks

indicate that the species was not in the top 5 most abundant for that treatment. .................. 24

Table 4 – Average number of species found in the soil seed bank (SSB) and above ground vegetation

(AGV), and the average similarity between the SSB and AGV, using Sorenson’s similarity index.

................................................................................................................................................ 27


1

CHAPTER 1 – INTRODUCTION

Ecological restoration is of vital importance in a world of rapid human

population growth and development, and consequent degradation of the natural

environment. Simply conserving the remaining natural areas is no longer sufficient to

meet current goals (Grimm et al. 2008; McCarthy et al. 2012). Ecological restoration can

be defined broadly as the process of assisting the recovery of an ecosystem that has

been degraded, damaged or destroyed (SER 2004). As biodiversity conservation

becomes ever more important on a global scale, restoration is being used increasingly as

a tool to offset the ecological impacts of development (CBD 2010; Hobbs et al. 2011;

McCarthy et al. 2012). Offsets in restoration may occur through physically restoring an

area to its pre-disturbance state, or by securing and restoring new areas for

conservation (Gardner and Bell 2007; Hobbs et al. 2011). Restoration has the potential

to be misguided, under the expectation that ecosystems can be completely restored,

which may not always be a realistic goal (Gardner and Bell 2007; Hobbs 2007; Hobbs et

al. 2011). Ecological restoration is a relatively new science, and thus requires more

research in order to understand its complexities, and to create better outcomes for

biodiversity conservation in the future.

Increasing pressure on natural areas drives the need for ecological restoration.

Expansion of the built environment is having detrimental effects on natural areas,

through bushland clearing and fragmentation, altering of chemical and physical

dynamics and loss of biodiversity (Folke et al. 2004). It is these natural areas which are

vital for species as either habitat, feeding grounds, for ecological linkages and to provide

ecosystem services (Loreau et al. 2001; Grimm et al. 2008; Palmer and Filoso 2009).

Restoring biodiversity can also create greater resilience to future disturbance as well as

enhance ecosystem function (Loreau et al. 2001; Folke et al. 2004). In addition to

ecological benefits, restoration can return many other values to the landscape, including

personal, socioeconomic and cultural values (Clewell and Aronson 2007).

A broad range of techniques are used to restore areas of degraded vegetation,

most often involving two distinct methods, the planting of nursery-raised seedlings and

direct seeding using seed mixes of desired native species. Topsoil transfer, the process

of moving topsoil containing dormant but viable soil stored seeds of native plants –

potentially in high quantities – is a relatively recent method employed to enhance

restoration success, and is playing an increasing role in the restoration of ecosystems


2

(Tacey, Olsen, and Watson 1977; Engel and Parrotta 2001; Skrindo and Pedersen 2004;

Ralph 2006; Tozer et al. 2012). Direct planting is characterised by relatively high

survivorship but can be expensive and is limited to those species available from

commercial nurseries (Engel and Parrotta 2001; Viani and Rodrigues 2009). Direct

seeding can be done mechanically on a large scale or by hand, but is generally

considered to have a high mortality compared to planting, and is most feasible in areas

receiving over 250 mm rainfall per year (Ackzell 1993; Knight, Beale, and Dalton 1998;

Engel and Parrotta 2001). It is also expensive, since seeds must be collected for each

species, which may vary in their timing and abundance of seeding, and in their

germination requirements, so that their ability to be restored via these methods is

limited (Ralph 2006; Sweedman and Brand 2006; Koch 2007b). Topsoil transfer has

several benefits over these methods, in particular over direct seeding (Fry 2011). The

soil itself can suppress the potential weedy underlying soil which could limit the success

of planting and seeding. Moving topsoil can also transfer beneficial soil microbes and

other propagules of species not able to be restored readily by other methods (Jasper

2007; Koch 2007b). The use of soil seed banks through topsoil transfer is increasingly

common in restoration because of its benefits over other methods (Howard and Samuel

1979; Koch 2007b; Tozer et al. 2012).

Most of the world’s plant communities produce some form of soil seed bank, and

it is these seed banks that are an important part of a functioning ecosystem (Harper

1977; Bell 1999). Mature seed is shed from the parent plant to the soil surface, and

accumulation of these seeds over time develops a soil seed bank comprising seeds which

may be able to remain dormant for many years (Bell, Plummer, and Taylor 1993; Baskin

and Baskin 1998; Fenner and Thompson 2005; Keith 2012).

There are two broad categories of soil stored seed, transient seed banks, those

that persist for less than a year, and persistent seed banks, which persist for longer

periods of time (Fenner and Thompson 2005). This is an important distinction because

transient seed banks tend to be those that germinate immediately or seasonally, while

those that persist for longer periods are dormant until they receive an appropriate

trigger (Merritt and Rokich 2006). Triggers are related to disturbance or opportunity,

whereby either light is received to the understory or a more widespread disturbance

such as fire enables plant propagules stored in the soil to take advantage of a lack in

competition. However, not all species contribute equally to the soil seed bank. For

example, serotiny (canopy stored seed) is used by some species, and is commonly seen

in the Mediterranean regions of Western Australia and South Africa (Lamont et al.


3

1991). Resprouting (tending not to produce high amounts of seed) is also a trait

exhibited in species which results in little contribution to the soil seed bank (Lamont et

al. 1991). Soil seed banks as a result are highly variable in composition and seed density

both locally and globally depending on the ecosystem type, species present and time

since disturbance (Hopfensperger 2007).

Depth, heat and smoke cues are important factors in enabling germination from

soil seed banks in fire-prone environments. Seed density in soil declines with depth,

with most seeds close to the soil surface, those buried at depths greater than a few

centimetres generally failing to germinate (Bellairs and Bell 1993; Brown, Enright, and

Miller 2003; Fenner and Thompson 2005; Luzuriaga et al. 2005; Merritt and Rokich

2006; Fisher et al. 2009). Many seeds in the soil seed bank lie dormant until a

germination cue such as smoke and/or heat occurs. Without such a cue to stimulate

germination, many seeds will not germinate easily (Bell, Plummer, and Taylor 1993; Bell

1999). In fire-prone environments, the chemicals in smoke have been found to be a key

component in triggering germination (Keeley and Keeley 1987; De lange and Boucher

1990; Dixon, Roche, and Pate 1995; Roche, Koch, and Dixon 1997; Smith, Bell, and

Loneragan 1999; Rokich and Dixon 2007; Tozer et al. 2012). Heat is also a common

trigger in many hard-seeded species, due to scarification, or damage of the seed coat

that results from heat exposure (Bell, Plummer, and Taylor 1993; Baskin and Baskin

1998; Enright and Kintrup 2001; Merritt and Rokich 2006). The combination of heat and

smoke together is increasingly seen as the most effective means to illicit germination

across a range of species in such environments (Keith 1997; Blank and Young 1998;

Smith, Bell, and Loneragan 1999; Thomas, Morris, and Auld 2003; Merritt and Rokich

2006; Lindon and Menges 2008).

Seed density is one of the defining characteristics of soil seed banks. Variations

in density can be found between regions and ecosystem types, and are also influenced

by the ecology of the system, including plant functional traits. Much of the global

research into soil seed banks has been undertaken in temperate Mediterranean

environments. For example: the soil seed banks of the Fynbos shrublands of South

Africa range from 1100-1900 seeds m-2 (Holmes and Cowling 1997). Densities of 1050-

1802 seeds m-2 are reported from a heathland environment in Spain (Valbuena and

Trabaud 2001). The northern Jarrah forest of South-West Australia has been seen to

have seed densities of between 377-1579 seeds m-2 (Vlahos and Bell 1986). Tropical

Rainforests in comparison have generally lower densities 88-694 seeds m-2 (Martins and

Engel 2007; Dainou et al. 2011). Soil seed stores in Mediterranean environments thus


4

tend to contain higher amounts of seed that can be utilised for restoration by methods

such as topsoil transfer. However, even within Mediterranean environments plant

functional traits can influence seed density. For instance a vegetation community near

Eneabba, Western Australia, is dominated by serotinous and resprouter species, as such

much lower soil seed densities of 140-174 seeds m-2 (Bellairs and Bell 1993) have been

observed.

Banksia woodland of South Western Australia is a high biodiversity ecosystem

and represents an ecosystem of serious conservation concern (Myers et al. 2000; Rokich

and Dixon 2007). This research project focuses on topsoil transfer as a method for

restoration of Banksia woodland on the Swan Coastal Plain (SCP) of Western Australia.

The Banksia woodlands sit within a biodiversity hotspot, characterised by high richness

and endemism, with 79.2% of the vascular plant species and 21.9% of animal species

endemic to the region (Myers et al. 2000; Paczkowska and Chapman 2000). Within this

hotspot, Perth is a rapidly expanding city resulting in the fragmentation and degradation

of the natural landscape (Ramalho and Hobbs 2012). Continued land clearing,

fragmentation, and degradation results in increased pressure on species requiring

natural vegetation for feeding and roosting habitat, such as Carnaby’s Cockatoo

(Calyptorhynchus latirostris) which is listed as ‘Endangered’ under the Environmental

Protection and Biodiversity Conservation Act 1999 (Cwlth) (Valentine et al. 2011). As a

whole, the South West of WA now only retains 10.8% of its original extant of vegetation.

Within this, the Banksia woodland ecological community is listed as endangered, making

restoration important in this setting to help conserve this community type (Myers et al.

2000; SEWPC 2009).

As the process of topsoil transfer is likely to be used increasingly as an offset to

clearing established vegetation communities for urban development or mining, it is

important for research of this kind to be conducted. Little published, peer-reviewed

research exists on the optimisation of topsoil transfer for restoration purposes

throughout the world. What little research has been carried out has predominantly been

undertaken in Western Australia (Vlahos and Bell 1986; Koch et al. 1996; Ward, Koch,

and Ainsworth 1996; Koch, Ruschmann, and Morald 2009). Alcoa World Alumina

(Alcoa) are the primary drivers of this research for mine site rehabilitation on the

lateritic soils of the Darling Plateau, east of Perth (Koch 2007a). This study on the SCP is

therefore innovative in that it tests the impacts of the transfer process on soil seed bank

properties relating to Banksia woodlands, and the value this process may hold for

restoration and management in the future. Potential applications of this study include


5

the optimisation of procedures and practices of restoration using topsoil transfer, while

also adding to our knowledge of the world’s soil seed banks in different environments. It

is vitally important for the preservation of Western Australia’s unique but threatened

native vegetation that this process is examined in detail, as many of our native plant

species are not currently able to be propagated by any other means (Rokich et al. 2000).

1.1 RESEARCH AIMS

This thesis examines the soil seed bank composition of undisturbed topsoil from a

natural bushland and compares it with the same soil after it has been removed,

transported, and spread at another site in the topsoil transfer process. The aim is to

establish in general terms how successful topsoil transfer is and how it could be more

successful through examining the following specific questions:

1. HOW DOES DEPTH OF TOPSOIL APPLICATION INFLUENCE RESTORATION OUTCOMES?

This research question examines the seed density by depth in the soil seed bank

both pre and post-transfer. Transfer involves stripping a depth of soil greater than

where the bulk of seeds are situated, therefore this may cause dilution of the seed

density of the soil that has been transferred (Figure 1). This may affect the germination

within the transfer sites when compared to the undisturbed bushland since many seeds

previously near the soil surface will now be buried too deep for germinants to grow

through the soil surface. This is important to potentially maximise restoration outcomes,

and because the amount of soil transferred affects the cost of transportation. Alcoa for

instance has used sieving of seed from soil to concentrate seed density and so reduce the

transportation component, however this does also remove small seeded species (Rokich

and Dixon 2007).

Figure 1 – Diagramatic representation of the change in seed gradient as a result of mixing due to the

transfer process.


6

2. WHAT EFFECT DOES THE TRANSFER PROCESS HAVE ON GERMINANT COMPOSITION?

The effects of the soil transfer process need to be examined more closely. In this

study trials are conducted both pre-transfer and post-transfer; this is an aspect that has

not been researched elsewhere. The rationale of this part of the study is that the

physical act of transferring the soil may have an influence on the germination ability of

the soil in either a positive or negative way. The process of topsoil transfer may lead to

the physical scarification of seeds within the seed bank, which could mitigate the need

for other germination treatments. Scarification, a physical germination trigger,

combined with smoke and heat treatment should provide enhanced germination of hard

seeded species, as a result the above procedure will be duplicated at the transfer site to

examine the effects of transfer (Baskin and Baskin 1998; Merritt and Rokich 2006).

3. DOES TREATMENT WITH FIRE RELATED CUES ENHANCE GERMINATION SUCCESS?

Treatments with heat and smoke in combination have been conducted to replicate

fire disturbance, considered a vital trigger for seed germination in many species,

especially in SW Australia (Wills and Read 2002). Smoke and heat treatments together

maximise the dormancy breaking effect and subsequent germination response. A

control treatment using watering only was conducted for comparison purposes (Pierce,

Esler, and Cowling 1995; Read et al. 2000; Merritt and Rokich 2006).

4. HOW REPRESENTATIVE IS THE SOIL SEED BANK TO STANDING VEGETATION?

Certain species of the Banksia woodland community will not be present in the soil

seed bank due to being resprouters or serotinous in nature; this includes the dominant

canopy genus, the Banksias (Wills and Read 2007). Previously it has been found that 60-

80% of the species of the Banksia woodland can store their seed in the soil (Rokich and

Dixon 2007). It is important to examine the species composition of the species that are

present in the soil seed bank, and how these relate to the standing vegetation of high

quality bushland sites, as this is the reference for restoration.

1.2 THESIS OUTLINE

This thesis is organised into 5 chapters. Chapter 2 provides details of the study

area and the methods used to answer the stated research questions. Chapter 3 presents

the results. An in depth discussion of these results is provided in Chapter 4, and

conclusions and recommendations for future topsoil transfer projects are presented in

Chapter 5.


7

CHAPTER 2 – STUDY AREA AND METHODS

2.1 STUDY SETTING

The climate of SW Australia is Mediterranean with hot, dry summers and mild,

wet winters (BOM 2012). Annual mean rainfall is 869 mm, 80% of this falling between

May and September, with the summer (December through February) average being 36

mm. Temperatures in summer average 31°C maximum and 17°C minimum, while over

winter, maximum and minimum temperatures average 18°C and 8°C respectively (BOM

2012). A sustained decrease in annual rainfall has been documented since the mid-

1960s with a 23 mm drop per decade (based on 1950-2005 records) (Timbal, Arblaster,

and Power 2006; Gallant, Hennessy, and Risbey 2007). Since the 1970s mean annual

temperature has increased by an average of 0.15°C per decade (Bates et al. 2008).

Climate predictions include continued drying of 15-160 mm and warming of 0.4-2.0°C

by 2030, relative to 1990 (Hughes 2003).

Study sites, Jandakot Airport (from which the topsoil was taken), Forrestdale

Lake and Anketell Rd (where topsoil from Jandakot Airport was received), were located

approximately 20 km south of Perth, Western Australia on the SCP (Figure 2). The SCP is

characterised by sandy soils of varying ages with north-south strips of similarly aged

soils, increasingly old and leached at increasing distances from the Indian Ocean (Powell

2009). Soils at the study sites are classified as Bassendean sands; Aeolian in origin and

pale grey to faint yellow in colour. These are the oldest soils on the SCP, originating in

the middle Pleistocene, around 800,000 years ago (McArthur 1991; Bolland 1998). Due

to their age, minerals and nutrients have been largely been leached, making these soils

quite infertile (Powell 2009).

The extant vegetation of the Jandakot Airport site was remnant Banksia

woodland, a unique vegetation community to the SCP. This vegetation type is dominated

by a tree layer comprising of Banksia attenuata, B. menziesii, B. ilicifolia, Eucalyptus

marginata, E. todtiana and Nuytsia floribunda, with a dense understory of shrubs, herbs,

sedges and rushes (JAH 2009). As with many of Perth’s remnant bushland areas, the site

at Jandakot airport has been isolated by urbanisation, and as such there has been little

influence of fire in the recent past and there is evidence of weed invasion, especially

concentrated at the edges (Fowler pers. obs.).


8

Transfer sites, Forrestdale Lake and Anketell Rd, were selected by the

Department of Environment and Conservation (DEC) based on a variety of priorities

related to restoration and offset objectives (Table 1). These sites are now contained

within nature reserves; however they have had a rich history of disturbance since

European settlement. The study sites at these locations are areas of former agricultural

activity and have been cleared for several decades. Whilst the land in these areas in

recent times was predominantly used for grazing of sheep and other livestock, in the

earlier years of European settlement vegetable crops were the main activity, especially

within the area around Forrestdale Lake, and these areas were held in private

ownership until being assimilated into the reserve (DEC 2005). Historically, cleared

areas at both sites have become highly degraded and are now dominated by weeds

(CCWA et al. 2010). Adjacent areas at both Anketell and Forrestdale have had recent

restoration projects, both by topsoil transfer and other means, with mixed success

(Brundrett, pers. com.).

Jandakot Airport

Perth

Anketell Rd

Forrestdale Lake

Figure 2 – Site locations relative to Perth, Western Australia. The cross

indicating the location of Jandakot Airport from which soil was striped.

Triangles indicating the recipient sites of Forrestdale Lake (Nature

Reserve) and Anketell Rd. Adapted from the Nokia map service (Nokia

2012).

N


9

Table 1 – Criteria used by DEC and their relative importance in recipient site selection. Adapted from

Brundrett (2012).

Criteria Importance

Carnaby’s Cockatoo feeding habitat high

Bush Forever Site high

Within 45 km of Jandakot Airport on Swan Coastal Plain high

Site with secure tenure high

Carnaby’s cockatoo breeding site proximity high

Carnaby’s cockatoo night roost proximity high

Site containing Caladenia huegelii high

Banksia woodland similar to Jandakot Airport (i.e. Bassendean sands) Very high

Proximity to Jandakot Airport Very high

Total area of remnant vegetation high

Declared rare or priority flora: WA State listings medium

Threatened ecological Community or Priority Ecological Community: WA State

listings

medium

Rare or priority fauna: WA State listings medium

2.2 FIELD SAMPLING AND DATA COLLECTION

Field work was conducted in two phases, first the sampling of soils prior to

transfer and second, the sampling of soils at the two recipient sites following transfer of

topsoil. Sampling prior to transfer occurred during the period 24-29 February 2012 and

post-transfer at Anketell Rd and Forrestdale Lake on 23 May 2012. Following field

collection, soil samples were stored in dry paper bags until 1st June when glasshouse

work was initiated. Assessment of the soil seed bank was conducted through mass

germination. This method was chosen due to its practicality over sieve removal of seeds

from soil (which can miss small seeds), and that it excludes seeds that are not viable

(Gross 1990; Baskin and Baskin 1998).

Sampling at Jandakot Airport consisted of four 200 m transects situated

throughout the area designated for clearing and topsoil transfer. Transects were made

up of six 10x10 m plots spaced at ~10 m increments for a total of 24 plots. Extant

vegetation was sampled at all 24 plots, half by DEC in December 2011 and the remaining

half as part of this study. Vegetation data collected by DEC was percentage cover per

species in 10% increments, whereas the subsequent vegetation data collected used the

Braun-Blanquet (1932) cover abundance method, with ranks assigned as shown in

Table 2. The two data sets were rationalised to be comparable for assessment of extant

vegetation and the soil seed bank.


10

Table 2 – Ranking system for the allocation of cover rankings consistent with Braun-Blanquet

(1932).

Ranking Percentage cover 0.1 <1% 1 1-5% 2 5-25% 3 25-50% 4 50-75% 5 75-100%

Vegetation clearing and soil transfer at Jandakot Airport commenced in late

February and transfer was completed by mid-May. Although a large area of Banksia

woodland was cleared, a smaller proportion, approximately 17 ha, had topsoil removed

and transferred (Figure 3) (Brundrett 2012; DEC 2012). Soil stripping from Jandakot

Airport was specified as 70 mm (limits: 50 mm to 100 mm). A converted loader was

used for this process, with wing-like bucket attachments (Figure 4) to prevent

harvesting of soil at greater depths. Topsoil was then transferred to recipient sites,

Anketell Rd (10-12 ha) and Forrestdale Lake (5-6 ha). Where applicable, existing weedy

soil present at recipient sites was removed using a grader, to a depth of 30 mm (limits:

20 mm to 50 mm). Transferred topsoil was then spread over the top at two depths, 50

mm (limits: 40 mm to 60 mm) and 100 mm (limits: 80 mm to 120 mm) (DEC 2012). Two

spreading depths were used to enable further research to be conducted on this project.

Figure 3 - Position of transects and plots at Jandakot Airport. The area which soil was stripped

from is enclosed by the solid black lines. Plots are represented by the dots; with series of dots

forming transects which are labelled accordingly.

N


11

Transfer of soil from Jandakot Airport was received at Lake Forestdale (Figure

5) and at Anketell Rd (Figure 6). An equal number of plots were set up (n=24) to match

the Jandakot site. These were allocated proportionally amongst the recipient sites based

on the extent of the area, with seven plots at Anketell East, four at Anketell West, five at

Forrestdale SW, five at Forrestdale NW and three at Forrestdale SE. These were

randomly positioned within the deep areas of transferred topsoil (~10 cm deep), to

ensure depth of sampling did not penetrate into the underlying, former soil surface.

Figure 4 - Main: Image of the loader used to harvest topsoil from Jandakot Airport by Urban

Resources. Insert: Side view of the wing-like bucket modifications used to prevent over harvesting of

topsoil.

Figure 5 – Site and plot locations at Forrestdale Lake. Dots representing plots, clustered in the deep

areas of transferred soil at the three smaller sites within the greater area of Forrestdale Lake

(Nature Reserve).

N

Wing-like modifications


12

Figure 6 – Site and plot locations and Anketell Road. Dots representing plots, clustered in the deep

areas of transferred soil at the three smaller sites within the greater Anketell Rd site.

Soil samples were required to give inference to the area as a whole. Soil

sampling tubes made from PVC pipe, 15.5 cm in diameter, 10 cm length were used

(Figure 7). Five subsamples per 10x10 m plot were taken and composited (Figure 8) for

each of two depths: 0-5 cm and 5-10 cm. This method was chosen as it provides a

consistent volume sample from which further calculations of density can be made and is

similar to the methods employed in other studies of soil seed banks (Bekker et al. 1997;

Fisher et al. 2009).

N

Figure 7 - Diagram of the soil sampling tube (not to

scale) used for sampling topsoil in this study.

Figure 8 – Sampling arangement within each plot

(not to scale), the circles representing the

locations of soil samples which were composited.


13

2.2.1 GLASSHOUSE PREPARATION

Following final field sampling, soil samples were prepared in trays and placed in

the glasshouse for germination trials to assess seed bank composition. Trials were

initiated on 31 May – 01 June, 2012. To maximise germination rates, soil samples were

treated with heat and smoke together, as treatments are known to enhance germination

(Dixon, Roche, and Pate 1995; Keith 1997; Roche, Koch, and Dixon 1997; Keeley and

Fotheringham 1998; Tieu et al. 2001), and another set of soil samples prepared as

controls. The initial step was to prepare germination trays (35.5 cm x 29.5 cm x 5 cm);

192 trays were required for 96 soil samples (48 from pre-transfer site and 48 from post-

transfer sites). Germination trays were cleaned to remove any soil, seeds and pathogens

possibly present from past use. Trays were lined with Chux® cloth and filled with 1500

ml of vermiculite mixed with 500 ml of clean white sand, and the topsoil placed on top of

the sand-vermiculite mix.

Samples varied widely in their bulk densities due to the presence of high levels

of organic matter in some (especially proteoid roots). To make samples consistent,

topsoil samples were poured into a bucket and mixed. The weight of the total sample

was then taken before a quantity of this sample was put into two aluminium trays (29

cm x 19 cm x 5 cm) and weighed to be ~2100 g, with the aim to keep the quantity of soil

treated constant. This was not always possible due to some samples containing a high

proportion of proteoid roots, as these made large volume/low weight samples. All trays

were numbered and labelled as completed, as well assigned a score between 0 and 4 for

the amount of proteoid roots present in the tray, 0 being not present, 4 being 75-100%.

By recording mass used and total sample mass, a correction factor could be applied to

data later. Once trays were filled, half were treated with heat and smoke. Heat treatment

consisted of boiling water poured to fill the tray and left to cool, before being spread

evenly in a germination tray. Control trays were treated with an equal amount of cool

water.

Once all trays were prepared and located in the glasshouse, smoke treatment

was applied to samples that had previously been heat treated. This was done with

aqueous smoke solution REGEN 2000 SMOKEMASTER, a commercially available product

that has been found to replicate the effects of natural smoke associated with bushfires

(Thomas and Davies 2002; Wills and Read 2002). The solution was diluted 10 to 1 as

recommended by the suppliers, and 400 ml lots of the diluted solution were applied by

watering can to each germination tray that required treatment.


14

To ensure possible contamination events of plant propagules entering the

glasshouse were identified, five clean seed-free sand trays were prepared in the same

manner as the other germination trays, but contained sterile sand instead of topsoil.

This was designed to indicate if experimental contamination had occurred from seed

entering the glasshouse through the air conditioning system or other means.

The glasshouse was air-conditioned to prevent excessive temperatures from

occurring, with settings designed not to exceed 24°C (range: 7-24°C). Watering was

maintained by automatic table reticulation, using misters set to run for 10 mins every

second day. Nevertheless, watering rates were found to be variable depending on table

position (range: 15-91 ml). Trays were monitored to evaluate if extra watering was

necessary, and every four weeks trays were re-randomised within the glasshouse to

mitigate any possible effects on germination among trays.

2.2.2 GERMINATION TRACKING

To quantify germination timing and identify species, emergence was checked

weekly and germinants marked with a series of colour-coded toothpicks. Each

germinant was marked with a toothpick consisting of a colour code (up to 4 bands of

colour) to identify germinants of the same species. Over time this identification was

changed as necessary, since germinants that appeared to be the same in early stages of

growth sometimes developed into several distinct species (Figure 9). Due to the very

high density of emerging seedlings, from time to time advanced individuals needed to be

pulled out to prevent too much competition for space in the trays; numbers and

identifications of plants pulled were recorded. Representative plants for each

identification code were potted up and grown on for identification purposes.


15

2.2.3 DATA ANALYSIS

Normal parametric statistics were used to analyse overall patterns of density,

richness, and diversity, native and invasive species, growth habit and certain functional

traits. Data were analysed using multi-way ANOVA for density, richness and diversity on

a per tray basis to assess the potential effect of depth and treatment, plant functional

traits and other grouping factors, among and between sites. Linear regression was also

conducted to gain a measure of estimate, as well as to determine R-squared values. The

statistical analysis program R’ 2.14.2, published by The R Foundation for Statistical

Computing was used for these analysis (R 2012).

Density, richness and diversity are used in this study to investigate how topsoil

transfer influences the soil seed bank, and for overall comparisons between the various

treatments. Density was calculated (Equation 1) to provide a comparable measure of

germination across trays, while species richness, the average number of species in a

given sample, quantified biodiversity, and was important for ecological comparisons

(Gotelli and Colwell 2001). The Shannon-Wiener index of diversity (SWI) was used as

the measure of diversity (Equation 2). This index incorporates both richness and

evenness of the population (Sax 2002). All data was assessed on the groupings of site

(natural/transfer), depth (0-5 cm, 5-10 cm) and treatment (control, treated). All means

were graphed with 95% confidence intervals, to aid the interpretation of figures

(Cumming 2005, 2009). Unknown species were removed from graphical displays as they

represented less than 2% of the data on all occasions, most being less than 1%.

Figure 9 – Diagram of seeding marking procedure, bands indicating

colour code progression as identification became more developed.


16

Sorensen’s similarity index (Equation 3) was used to determine the percentage

of species in common between the soil seed bank and the standing vegetation (Sorensen

1948). Some species had to be removed from this analysis due to being unidentified, to

prevent skewed results. Analysis was conducted with annual and serotinous species,

and with these species removed, for each treatment.

Multivariate community analysis methods were used to explore compositional

changes in the data. Ordination analysis of community composition was done using PC-

ORD version 6.08 (McCune and Mefford 2011). Nonmetric Multidimensional Scaling

(NMS) was used based on the Sorensen distance measure, which performs well in

demonstrating ecological gradients with complex data sets (Culman et al. 2008; Peck

2010). Stress values should ideally be under 20 for this type of ordination, however

values from 20 to 35 can still yield useful interpretations, as stress tends to increase

with sample size (McCune and Grace 2002).

Multi-response permutation procedures (MRPP) were used to assess the

evidence for differences between groups at the community level, evaluating differences

between two or more groups based on within-group similarities (McCune and Grace

2002; Peck 2010). MMRP has the advantages over other multivariate analysis

techniques in that it does not require distribution assumptions, which are rarely met in

ecological situations (Biondini, Bonham, and Redente 1985; Zimmerman, Goetz, and

Mielke 1985; McCune and Grace 2002). The Euclidean (Pythagorean) distance measure

was used for the MRPP due to its better representation of outliers in such an analysis

(McCune and Grace 2002). Rare species were removed from the ordination dataset if

only present once, resulting in 25 species being removed. Outlier analysis was then

( )

∑

Equation 1 – density

Equation 2 – Shannon-wiener index of diversity

Equation 3 – Sorensen’s index of similarity


17

conducted; tray 96 was removed from the dataset on this basis. A random starting

configuration was used, and a thorough NMS was conducted with 250 runs. NMS

ordination was also run with native perennials only, however a useful ordination was

not found using PC-ORD.


18

CHAPTER 3 – RESULTS

The results from this study from sampling conducted prior to topsoil removal

and post-transfer, subsequently examined in the glasshouse are presented and

statistically analysed in three main themes: seed bank dynamics, similarity, and

community analysis.

3.1 SEED BANK DYNAMICS

Seed bank dynamics were examined during germination trials lasting 13 weeks.

Emergence of seedlings peaking around week 8, with a total of 11,551 germinants

recorded over the entire period, belonging to 127 species (Figure 10).

Figure 10 – Proportion of total germinants the study over time (weeks).

Mean density of germinants found in this study was 1935 germinants m-2 this

ranged between 1692-4239 germinants m-2 in natural soils and 795-1016 germinants m-

2 in transferred soils. In total 79% of all germination occurred in the natural soils (0-5

cm: 73%, 5-10 cm: 27%). Transfer (post-transfer) soils on average contributed to 21%

of overall germination (0-5 cm: 54%, 5-10 cm: 46%) (Figure 11).


19

There is a significant depth effect between 0-5 cm and 5-10 cm (F1, 185 = 47.3, p

<0.001), with an average difference of 2347.9 ± 348.7 germinants m-2. However this

depth effect is not the same between sites, indicated by the significant interaction

between depth and site (F1, 185 = 33.4, p <0.001). The overlap of confidence intervals in

transferred soil suggests that there is no depth effect in these soils. These transfer sites

had significantly lower densities than the natural sites (F1, 185 = 104.7, p <0.001), with an

average difference of 2472 ± 348.70 germinants m-2. Treatment had a significant

influence (F1, 185 = 8.5, p =0.003), increasing germination by an average 1537.8 ± 348

germinants m-2, but again this was only apparent in the natural soils, with a significant

interaction between site and treatment (F1, 185 =13.9, p <0.001), the transfer soils

showing no significant influence of treatment.

A total of 127 species were recorded in the study, with species richness patterns

found to be similar to those of density (Figure 12). A significant depth effect is present

(F1, 185 = 80.9, p <0.001), with on average 7.13 ± 0.90 more species being located in the 0-

5cm region. The depth response is different between the natural and transfer soils, as

indicated by the significant interaction between depth and site (F1, 185 = 26.2, p <0.001).

A significant difference between sites is also apparent (F1, 185 = 80.9, p <0.001) between

natural and transferred soils. Transferred soils contained an average of 7.04 ± 0.90 less

Figure 11 – Mean germinants m-2 by treatment across depth and site.


20

species than the natural soils. Treatment has a significant influence on richness (F1, 185 =

7.4, p =0.007). Treatment effect between sites is not the same, with a strong interaction

influence (F1, 185 = 13.2, p <0.001), no significant response of treatment in the transfer

soils.

Figure 12 – Mean species richness by treatment across depth and site.

The mean Shannon-Wiener diversity (SWI) was 2.01, with natural 0-5 cm being

highest at 2.34. A somewhat different pattern to the density and richness plots can be

observed (Figure 13). There is a significant depth effect among both sites (F1, 185 = 34.8, p

<0.001), and a significant difference between sites (F1, 185 = 28.8, p <0.001). There are no

significant interactions of treatments.


21

Figure 13 – Diversity using the Shannon-Wiener index, by treatment across depth and site.

Overall, grassy species (including grasses and grass-like species) contributed

812.58 germinants m-2 or 41.98%. Herbs accounted for 676.84 germinants m-2 or

34.97%, both the grassy and herbaceous species represented the majority of germinants

found within the seed bank (76.95%) (Figure 14). The remainder was filled by the

shrubs (166.53 germinants m-2, 8.60%), succulents (274.85 germinants m-2, 14.2%).

Grassy species were significantly influenced by depth (F1, 185 = 20.6, p <0.001),

representing a reduction between 0-5 cm and 5-10 cm of an average of 699.57 ± 166.58.

A significant site effect is also supported (F1, 185 = 106.2, p <0.001) and although

treatment is not significant for grassy species overall, there is a significant interaction

here, suggesting a shift in the pattern generated by treatment between sites (F1, 185 =

14.9, p <0.001).

The density of herbaceous species follows a similar trend to that of the grassy

species, having a depth effect (F1, 185 = 45.1, p <0.001), a site effect (F1, 185 = 73.0, p

<0.001), and significant treatment effect (F1, 185 = 3.9, p =0.05). Significant interactions

are seen between depth and site (F1, 185 = 38.1, p <0.001), also between site and

treatment (F1, 185 =4.4, p =0.04).


22

The density attributed to shrub species, significant depth (F1, 185 =7.2, p =0.008),

site (F1, 185 =129.8, p <0.001), treatment (F1, 185 =20.3, p <0.001), interaction between

depth and treatment (F1, 185 = 5.0, p = 0.03) and interaction between site and treatment

(F1, 185 =8.4, p =0.004).

Succulent species has significant depth effect (F1, 185 = 5.6, p = 0.02) this differing

between sites (F1, 185 = 10.1, p = 0.002), significant site effect (F1, 185 = 5.2, p = 0.02), with

an increased representation in the transferred soils.

Figure 14 – Mean germinants m-2 by treatment, across depth and site, comparing growth forms.

Across all treatments and depths, invasive species represent on average 8%,

native annuals 68% and native perennials 17% (Figure 15).

Significant depth effect can be seen for invasive species is observed (F1, 185 = 26.8,

p <0.001), with an estimated reduction of 421.64 ± 59.75 germinants m-2. There is a

significant difference between sites (F1, 185 = 23.6, p <0.001), 412.70 ± 59.75. Treatment

has a negative effect on invasive species (F1, 185 = 5.6, p = 0.02), a difference of 187.02

germinants m-2. A significant interaction is present between depth and site (F1, 185 = 30.9,

p <0.001), indicating the depth effect was not the same among.


23

Native annual species have a significant depth factor (F1, 185 = 33.9, p <0.001),

1592.80 ± 283.2 germinants m-2, significant site effect, (F1, 185 = 62.9, p <0.001), resulting

in a difference of 1506.50 ± 283.20 germinants m-2, and significant effect of treatment

(F1, 185 = 6.4, p = 0.01) resulting in an increase of 1149.40 ± 283.20. Significant

interactions can also be seen between depth and site (F1, 185 = 23.5, p <0.001), and

between site and treatment (F1, 185 = 12.7, p <0.001).

Native perennial species, have a significant depth effect (F1, 185 = 14.5, p <0.001),

184.34 ± 59.98 germinants m-2. Significant site effect is also present (F1, 185 = 175.2, p

<0.001) a difference of 417.61 ±59.98 germinant m-2. Treatment effect is significant (F1,

185 = 14.6, p <0.001), resulting in an increase of 304.52 germinants m-2. Significant

interactions of depth and site (F1, 185 = 7.0, p = 0.009) and site and treatment (F1, 185 =14.7,

p <0.001).

Figure 15 – Mean germinants m-2 of invasive species and native species split into longevity

categories, across treatment and depth (unknown species removed).


24

The top 5 species contributed 47% to 65% of the overall germination in each

grouping (Table 3). All of the species represented in the high dominance categories are

native species. Native annuals are most dominant in the soil seed bank, with Crassula

colorata, Isolepis marginata and Centrolepis glabra occurring in the top 5 abundant

species across all groupings. Crassula colorata became most dominant in the transferred

soils.

Table 3 - Top 5 species by abundance for each treatment on natural and transferred soils. Blanks

indicate that the species was not in the top 5 most abundant for that treatment.

Germinants (Percentage of grouping) Species Natural

(control) Natural

(treated) Transfer (control)

Transfer (treated)

Centrolepis alepyroides - - 57 (4%) -

Centrolepis glabra 249 (7%) 566 (10%) 116 (9%) 67 (6%) Crassula colorata 244 (7%) 329 (6%) 466 (36%) 336 (31%) Gnephosis angianthoides - - 64 (5%) -

Isolepis marginata 617 (17%) 1257 (23%) 145 (11%) 136 (13%) Isotoma hypocrateriformis - - - 40 (4%)

Leucopogon conostephioides 262 (7%) - - - Poranthera microphylla - 346 (6%) - -

Trachymene pilosa 341 (9%) - - - Unknown_24 - 345 (6%) - 55 (5%)

Totals 1713 (47%) 2843 (51%) 848 (65%) 634 (59%)


25

Native perennial (discussed previously), is made up of woody and non-woody species

(Figure 16). They differ in that woody species are effected by treatment (F1,185 = 20.1, p

<0.001), increasing density by 201.09 ± 36.24 germinants m-2, where as this is not

significant in non-woody species. Woody species also have a significant interaction of

depth and treatment (F1,185 = 4.9, p = 0.03). Non-woody have a significant interaction of

depth and site (F1,185 = 5.7, p = 0.02), where woody species do not.

Figure 16 – Density of native perennial species and their proportion of woody and non-woody.

Overall seeders contributed to 87% of the composition, a further 11% were

resprouting species. Seeder and resprouter species, despite being different in

abundance, both followed a similar trend to each other, both having significant depth

(F1, 185 = 44.6, p < 0.001; F1, 185 =9.5, p = 0.002), site (F1, 185 =87.2, p <0.001; F1, 185 =89.1, p

<0.001), and treatment (F1, 185 = 8.1, p 0.005; F1, 185 =7.0, p = 0.009) effect. Interactions

are seen between depth and site (F1, 185 = 32.2, p <0.001; F1, 185 = 4.1, p = 0.04), as well as

site and treatment (F1, 185 = 12.3, p <0.001; F1, 185 = 15.5, p <0.001), indicating the depth

and treatment effects are not the same between sites.


26

Figure 17 – Density of germinants m-2 of seeders and resprouters across treatments, depths and

sites.

Overall the highest densities of germinants are associated with the mid-range of

proteoid root score >0 to 75%, the highest category of root matter (75% to 100%)

resulted in reduced germination.

Figure 18 – Mean density germinants m-2 of categories of Proteoid roots (0=0, 1=0-25%, 2=25-50%,

3=50-75%, 4=75-100%).


27

3.2 SIMILARITY

Similarity between the soil seed bank and the extant vegetation, without

excluding species such as annuals and serotinous species, is 19% ± 2.8. With serotinous

species excluded from the standing vegetation and annuals removed from the soil seed

bank results from control (not treated soil seed bank), similarity then reduced to 15% ±

2.5. Treated soil seed banks result in the highest similarity of 19% ± 3.3.

Table 4 – Average number of species found in the soil seed bank (SSB) and above ground vegetation

(AGV), and the average similarity between the SSB and AGV, using Sorenson’s similarity index.

Average ± 95CI SSB AGV Sorenson’s similarity (%)

SSB and AGV (full)† 27 ± 2.2 33 ± 1.8 19 ± 2.8 SSB and AGV (control)* 5 ± 0.7 26 ± 1.4 15 ± 2.5 SSB and AGV (treated)* 9 ± 0.9 26 ± 1.4 19 ± 3.3

† Only unidentified species were removed.

* All serotinous species and annuals were removed from the standing vegetation. All annuals and unidentified species

were removed from the soil seed bank data. These would not have been consistently present between sampling.

3.3 COMMUNITY ANALYSIS

The NMS ordination of species abundance in all trays, using the Sorenson

distance measure, yielded a 2-dimentional solution with a final stress of 20.52, and

instability of 0.000 over 58 iterations (Figure 19). Axis 1 (capturing 44% of the

variability) is associated with a site based gradient, axis 2 (capturing 27% of the

variability) a depth gradient (cumulative r2 = 0.71). MRPP analysis was conducted on

several combinations of groups; distinct variations in community structure could be

seen between depth and site (A=0.14, p<0.001) and between natural and transferred

soils (A=0.10, p<0.001), however treatment showed no significant difference (A=0.01,

p<0.002).

The panel of joint plot comparisons, and associated correlation tables (Figure 20,

A, B and C) visually show the relationship of variables with the ordination axes. Only

vectors with an r2 > 0.20 are displayed. All growth forms are associated with depth

(Figure 20, A). Succulents are correlated with site, however they are the only growth

form negatively correlated with axis 1. All growth forms are correlated negatively with

axis 2, suggesting 0-5 cm natural soils are more important.


28

Diversity, richness and proteoid score (Figure 20, B) show density and richness

correlated strongly with site, the negative correlation with axis 2 suggesting these

factors are also correlated with 0-5 cm natural soils. Proteoid score has a strong

correlation with natural sites as a whole.

Species, (Figure 20, C) show the most highly correlated species. Crassula colorata is the

only species negatively correlated with axis 1 (site), having a greater correlation with

depth. All other species here are correlated with the natural site.

Figure 19 – Ordination of all trays using NMS. Axis 1 correlated with site, from transfer to natural.

Axis 2 correlated with depth, 5-10cm to 0-5cm.

Axis 1 (r) Axis 2 (r) Grassy .727 -.353 Herb .528 -.404 Shrub .654 -.043 Succulent -.096 -.649 Woody . .654 -.043 Native .648 -.474 Invasive .335 -.438 Annual .566 -.544 Perennial .727 -.038

Axis 1 (r) Axis 2 (r) Proteoid score

.625 .021

Richness .673 -.334 Density .624 -.503

Axis 1(r) Axis 2(r) Austrostipa compressa (austcomp)

.451 -.133

Centrolepis glabra (centglab)

.485 -.102

Crassula colorata (crascolo)

-.100 -.641

Isolepis marginata (isolmarg)

.577 -.292

Laxmannia sessiliflora (laxmSP)

.464 -.039

Leucopogon conostephioides (leuccono)

.452 .017

Figure 20 – Panel of three joint plot analyses, with correlations. A – Growth form and invasive status, B – Richness and diversity, C – species. Only those vectors with r2 values > 0.20

are displayed.

A. Joint plot analysis of growth form and invasive status. B. Joint plot analysis of richness and diversity. C. Joint plot analysis of species.


31

CHAPTER 4 - DISCUSSION

4.1 INFLUENCE OF DEPTH OF TOPSOIL ON RESTORATION OUTCOMES

4.1.1 THE SOIL SEED GRADIENT

Consistent with previous work (Bellairs and Bell 1993; Read et al. 2000; Rokich

et al. 2000; Brown, Enright, and Miller 2003; Pickup, McDougall, and Whelan 2003;

Fenner and Thompson 2005; Merritt and Rokich 2006; Fisher et al. 2009), natural soils

had a strong depth gradient with most (73%) seeds in the top 5 cm. In transferred soils

there was no evidence of this depth gradient, although few studies have looked at this

aspect. Koch et al. (1996) found evidence of a mixed profile after the topsoil transfer

process had been conducted, finding only 15% of the seed within the top 5 cm (diluted

from 20 cm) of transferred soil, compared the results of this study which found 54%

(diluted from 7 cm, range: 5-10 cm) of the seed in this depth zone after transfer. A study

into soil seed banks affected by intense disturbance by Luzuriaga et al. (2005)

demonstrated a similar effect from the disturbance of ploughing.

It would be expected that transferred soils, after a mixing effect during the

transfer process, would be an average between the 0-5 cm and 5-10 cm depths of the

undisturbed soils. However, transferred soils produced less germinants than even the

undisturbed 5-10 cm from Jandakot Airport. Alcoa found in its mining operations within

the Jarrah forest of Western Australia that compaction had caused a 5% reduction in the

profile by up to 75 cm in depth (Croton and Watson 1987). Compaction occurring during

the clearing and to a lesser extent during the soil stripping process may have resulted in

a greater proportion of topsoil being removed from the soil source site (Figure 21). Thus

this would have a dilution effect reducing germination in the transferred samples.


32

Figure 21 – Graphical representation of the potential influence of compaction in the soil stripping

process. Effect of over harvesting is for illustrative purposes only.

Although this study anticipated that the physical abrasion of transfer could be

beneficial by being a physical germination trigger, this was not the case, as germination

was less in transferred soils. The transfer process and compaction may have caused

damage to seeds within the soil seed bank, contributing to reduced germination

(Chambers and MacMahon 1994; Koch et al. 1996). Compaction is generally considered

a hindrance to in situ emergence of seedlings (Thill, Schirman, and Appleby 1979;

Kozlowski 1999; Botta et al. 2006), but no previous work has examined compaction

specifically for physical seed damage. In one of the few studies of the transfer process,

Koch et al. (1996) observed decreases in the germinable seed throughout the process,

with 31% of the original density found after respread of soil. Physical abrasion from

topsoil handling may destroy seed, especially smaller seeded species (Koch et al. 1996).

This trend is mirrored in this study, as it was observed that transferred soils were 26%

of the density of the pre-transfer soils.

4.1.2 LOSS OF ORGANIC MATTER (PROTEOID ROOTS)

The results show evidence that a dilution effect also occurs with the proteoid

organic matter within the soil. Proteoid roots are an adaption of the flora of south

Western Australia to low nutrient environments (Watt and Evans 1999; Neumann and

Martinoia 2002). Due to the rapid turnover of active roots, they add much organic

material to an otherwise impoverished soil structure, and therefore increase the

nutrient and water holding capacity of the soil (Neumann and Martinoia 2002). In this


33

study, the highest proteoid root scores are correlated with natural soils, and were highly

visible on site at Jandakot Airport (Figure 22). Therefore, as organic matter was less

prevalent in the transferred soils, this may have had implications on the success of

certain species that are adapted to the conditions provided by proteoid roots. DeFalco et

al. (2009) found a consistent positive relationship between cover of litter and the viable

soil density, proposing that litter is an indicator of degradation in arid lands. This may

have played some role in the high densities observed with root scores of >0 to 75%.

Organic material located in the top few centimetres of soil results in seedlings that are

more likely to establish successfully (Canham and Marks 1985; Baskin and Baskin

1998). Homogenization of the soil profile due to transfer can therefore create a loss of

stratification, seed dilution and loss of organic material that helps provide soil structure

needed for successful establishment.

Figure 22 – Photo of proteoid roots on site at Jandakot Airport.

4.1.3 IMPLICATIONS FOR THE TRANSFER PROCESS

From these results it can be seen that the mixing process that occurs when

transferring topsoil results in around 50% of the germinants lying beyond a germinable

depth. To maximise potential for restoration, soil stripping ideally needs to be a

maximum of 5 cm to retain high density, richness and structure in the transferred soil.

In order to take advantage of the seed store, its attributes, and the weed suppression

qualities of transferred topsoil, double stripping is a possible alternative to the single

stripping process conducted. Alcoa currently practices this, removing a shallow top

layer separately from underlying material, and subsequently returning soil in the same

order in which it was removed in, thus providing concentration of seed, suppression of

weeds, and maximisation of structural and biological attributes (Koch 2007a).


34

4.2 THE EFFECT OF TOPSOIL TRANSFER ON GERMINANT COMPOSITION

All growth forms were reduced in abundance in the transfer process. Community

analysis shows that there is a significant difference between natural and transferred

soils. The highest densities, richness, and most plant functional types were correlated

with 0-5 cm in natural soils. A greater proportion of succulents can be seen in

transferred soils. The abundance of these is still equal or less than those of natural soils,

therefore the seeds of the succulents, predominately Crassula, were likely less negatively

affected by the process of transfer. Interestingly shrubs and woody species are of a

greater proportion in 5-10 cm natural samples than the 0-5 cm natural samples, whilst

there is a reduced proportion of grassy and herbaceous species. Several factors could

lead to such a difference between natural and transferred soils. Koch et al. (1996)

flagged damage to seed during the process as being influential of low establishment.

Therefore, those species with more durable seeds could be less diminished than those

smaller seeded species. Timing of topsoil transfer has previously been found to effect

outcomes for restoration and germination (Ward, Koch, and Ainsworth 1996; Rokich et

al. 2000; Merritt and Rokich 2006). The time which topsoil transfer occurred (late

autumn) may have had some influence on the soil seed bank viability. Transfer that

occurs earlier in a year offers improved seedling recruitment, due to the greater time

available for establishment while appropriate conditions are present (Merritt and

Rokich 2006). Other studies have produced similar recommendations, such as Rokich et

al. (2000) who demonstrated autumn transfer produced better results than winter and

spring.

4.3 GERMINATION SIMULATION WITH COMMON GERMINATION CUES

This study has found that smoke and heat treatment (in combination) offered an

enhanced density and richness in natural soils and no impact on diversity. Previous

literature has found smoke and heat in combination to be important in enhancing

germination of the soil seed bank (Dixon, Roche, and Pate 1995; Enright et al. 1997;

Morris 2000; Read et al. 2000; Merritt et al. 2007). More recently there has been

increasing literature on smoke and heat in combination being the best method in which

to induce germination of seed in a broader range of species (Read et al. 2000; Thomas,

Morris, and Auld 2003; Merritt and Rokich 2006). Although abundance did increase,

composition seems to have not been significantly altered. Overall only native species

were affected positively by treatment, invasive species were found to decline. Not all

species respond to heat and/or smoke treatment (Thomas, Morris, and Auld 2003;


35

Clarke and French 2005). Studies have also previously shown that invasive species are

more vulnerable to heat and smoke exposure (Smith, Bell, and Loneragan 1999; Read et

al. 2000), and therefore may decline in abundance with such a treatment.

Heat and smoke treatment of transferred soil samples did not significantly alter

the soil seed bank composition, although woody species showed a response to

treatment in transferred soils. In this study, soil of the transfer sites were damp due to

recent rains, and this may have negated the effect of the treatment. However, being

damp alone is unlikely to be the cause as all treated samples were wet due to the

application of boiling water for heat treatments . Alternatively seasonality is more likely

to have played an influence. Several studies, such as that by Roche, Dixon and Pate

(1998) and De Lange and Boucher (1993), found that the season of smoke application

had an effect on germination response, summer having a greater response than late

autumn or winter. As a result of damp soil, the sampled transfer topsoil may have

already started germinating. However, due to the vulnerability of seed being damaged,

the movement of transfer/sampling could consequently reduce germination. Losses of

presence and abundance of species have been observed after ripping in autumn and

winter, compared with summer (Ward, Koch, and Ainsworth 1996). This is evidence

that disturbance after rains damages the viability or physically damages the early

emerging seed, and therefore effects the perceived results, although it is likely that this

would only affect the early responders (weeds and annuals) (Fisher et al. 2009).

4.4 SOIL SEED BANK AND ITS RELATIONSHIP TO THE STANDING VEGETATION

4.4.1 SEED BANK COMPOSITION

The soil seed bank is not representative of standing vegetation, even though

invasive species had a surprisingly little impact on the soil seed bank (accounting for

only 7% of overall germination). The species present in high abundance across all

treatments, namely Crassula colorata, Isolepis marginata, and Centrolepis glabra, were all

native annuals, with this group representing 68% of the soil seed bank composition.

Native perennials are an important group and are the focus of restoration efforts.

Without these species restoration is unlikely to be successful; however this group only

represented a fraction of the composition (17%).

There is also little similarity to the standing vegetation on a plot by plot basis.

This study found the seed bank – extant vegetation similarity ranged between 15% and

19% (excluding serotinous and annual species). This is less than the value that


36

Hopfensperger (2007) reported in a review of similarity, finding 31% similarity for

forest ecosystems over 31 separate studies. However, these forest ecosystems were

found to be the least similar, being most similar in grasslands (Hopfensperger 2007).

The results of Hopfensperger (2007) suggests the idea that grasslands invoke

high similarity due to grasses having a similar (prolific) seeding habit. This is further

supported by Odgers’ (1994) study in Eucalypt forests where grass species have a

similarity of 82-93%, and De Villiers (2001) who reported a similarity of 75% of annuals

in the South African Karoo. With a mixed community such as a woodland or forest

system, the prolific seeders, such as the grasses and herbs, will be disproportionate in

number compared to the other functional types, as they have a higher degree of

similarity within the soil seed bank. In Mediterranean fire prone environments,

similarity is likely to be lower; Enright et al. (2007) reported values of 26-43% in an

area with a high degree of serotiny. Furthermore, this region has a high abundance of

resprouter species which do not produce high quantities of seed. Although it is the

standing vegetation that drives the assemblage of the soil seed bank, due to

disproportionate seeding and dormancy mechanisms amongst species, the soil seed

bank alone is not capable of restoring many of the species required to achieve

restoration goals.

4.4.2 SYSTEM RE-ASSEMBLAGE

Results suggest that the system after topsoil transfer is in the early stages of re-

assemblage. Overall 77% of the soil seed bank studied was comprised of grassy and

herbaceous species, and although there is a high proportion of native species (91%),

68% of these are annual species. This is suggestive of early re-assemblage through

secondary succession. It is not well documented if the early composition after topsoil

transfer adjusts over time to become more similar to that of the original vegetation. A

natural part of recovery from disturbance is the rapid recovery from the pioneer

species, as these species are generally short-lived annual species such as grasses and

herbs (predominately seeders) (Enright and Cameron 1988; Hobbs and Atkins 1990).

The low numbers of woody species recruitment (8.6% shrubs, 0% trees) found in this

study was likely due to the soil seed bank not being the only source of recruitment (the

seed bank alone excludes resprouter and serotinous species). It is important to consider

that some species may not germinate in the early stages, or require specific conditions

to initiate germination that may have not been met (e.g. repeated drying and

wetting)(Lush, Kaye, and Groves 1984; Hobbs and Atkins 1990; Pickup, McDougall, and


37

Whelan 2003; Fenner and Thompson 2005). But, as governed by the concept of

complete initial floristics (Egler 1954), the climax community of woodland is unlikely to

be achieved with topsoil transfer alone.

4.4.3 IMPLICATIONS OF THE SIMILARITY OF THE SOIL SEED BANK TO THE

STANDING VEGETATION.

The soil seed bank is not representative of the standing vegetation, even with

removal of annual and serotinous species. This is likely due to many of this category

being resprouter species and therefore not producing much seed in relation to seeder

species (87% seeders, 11% resprouters). Similarity is higher with treatment of smoke

and heat in combination. Although disproportionate (seeders vs. resprouters), density of

woody species overall is reasonable (47-166 germinants m-2), and structural

regeneration of shrubs is possible over time through succession.

The study timeframe of thirteen weeks may not have been long enough to fully

establish the longer term composition of the soil seed bank. A longer timeframe to

observe the germination and compositional profile for Banksia woodland species after

topsoil transfer may be useful to examine the richness and compositional trends further.

Furthermore, factors such as repeated wetting and drying were not demonstrated in

this experiment, it has been recognised to aid seeding emergence in some species (Lush,

Kaye, and Groves 1984; Pickup, McDougall, and Whelan 2003; Fenner and Thompson

2005).


38

CHAPTER 5 – CONCLUSIONS AND RECOMMENDATIONS

5.1 CONCLUSIONS

Topsoil transfer is a useful tool for restoring degraded lands, especially where

other restoration options are not practical due to weed infestations or degraded soil

physical or chemical properties. This practice also aids to restore portions of the

vegetation community usually neglected by other forms of restoration due to

germination difficulties or technical restraints with these species. Furthermore,

restoring these species and a soil seed bank will aid future disturbance resilience of the

regenerated landscape. However, in the Banksia woodland of the SCP, topsoil transfer

alone may not adequately re-establish the structure and species composition required

for full recovery as many resprouter and serotinous species are often not

representative. Further ecological interventions through planting or direct seeding are

required for this to become a functioning Banksia woodland system.

The results of this project are highly useful for the optimization of the topsoil

transfer process. There is a dilution effect associated with the process of topsoil transfer,

which resulted in a loss of germinant density, richness and changes in the composition

of the soil seed bank. Timing is important in how effective treatment will be; treating

before rainfall while soil is still dry, being the key to successful results across all native

species groups. Treatment with germination cues (heat and smoke in combination)

resulted in an increase in density and species richness, overall improving the similarity

to the standing vegetation, but not influencing the relative proportions of growth forms.

Although there were some limitations to this study, mainly its length, these

results have several implications for topsoil transfer. The main findings suggest that the

transfer process needs rethinking due to the dramatic decrease in the germinable seed

bank post-transfer. The following section provides recommendations for future studies

and management of topsoil transfer.

5.2 RECOMMENDATIONS FOR MANAGEMENT OF TOPSOIL TRANSFER ON THE SWAN

COASTAL PLAIN

From this study, it is suggested that the soil seed bank does not highly resemble

the standing vegetation. Therefore, topsoil transfer should be conducted alongside other

means of restoration, such as planting or direct seeding, to make the post-restoration

community more resemblant of the original remnant bushland. There is supportive


39

evidence to suggest that topsoil transfer should be conducted in the summer months

while seeds are at their maximum dormancy. Once it becomes cooler and wetter, there

is a greater possibility of loss of seeds due to damage in the transfer process. Ideally,

treatment with smoke and heat should be conducted; a possible method could be the

application and subsequent burning of woody debris applied to the transfer areas,

therefore increasing the potential of serotinous species in restoration by releasing them

from the canopy.

Concentration of seed density is important to maximise the potential for

restoration using topsoil transfer. Stripping at a shallower depth will help increase seed

density by minimising the dilution effect seen with greater depth, enabling adjustment

for a potential compaction effect Alternatively, a form of double stripping could be

conducted to help retain other benefits associated with the soil, such as suppression of

weeds from underlying degraded soils, beneficial soil associations and chemical

properties that are also being transferred.

5.3 RECOMMENDATIONS FOR FUTURE RESEARCH

This research has raised questions of the topsoil transfer process, as well as

suggested ways that this process could be more successful. Continued monitoring of

past and present transfer projects is important for developing a full picture of topsoil

transfer and how these re-assembling communities change over time. Several areas can

be researched further to gain greater knowledge of the processes and the interactions

present to further develop solutions.

Soil stripping may have been inaccurate due to compaction; further research is

required on the influence of compaction and how much of an influence this plays. This

needs to be quantified in terms of measurable depth of compaction, so procedures can

be altered accordingly. Additionally the influence of compaction and other soil

disturbances involved need to be studied in regards to seed mortality in these

environments.

A small-scale simulated topsoil transfer (under controlled conditions) may be of

benefit to gain a detailed understanding of topsoil transfer, providing valuable insights

into the process by minimising potential variables. The simulation of topsoil transfer

could be achieved by gathering set-depth samples from remnant bushland and mixing

them together to simulate transfer, taking subsequent samples from this mixed soil, thus

removing potential contamination and compaction effects.


40

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APPENDICES

APPENDIX A – STATISTICAL SUMMARIES OF ALL NORMAL PARAMETRIC ANALYSIS

Table A1 – Statistical summaries of all normal parametric analysis. “NS” denotes non-significant values.

Density Richness Diversity Invasive Density

Native Density

Grassy Species

Herb Species

Shrub Species

Succulent Species

Native Annual

Native Perennial

Woody Non-woody Seeder Resprouter

Depth P-Value <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 0.008 0.02 <0.001 <0.001 0.009 0.002 <0.001 0.002

F-Value 47.3 80.9 34.8 26.8 43.6 20.6 45.1 7.1 5.6 33.9 14.5 7.0 10.3 44.6 9.5

Estimate (SE)

-2347.90 (348.70)

-7.13 (0.90) -0.42 (0.09) -421.64 (59.75)

-1933.70 (315.30)

-699.57 (166.58)

-1331.5 (195.1)

-43.83 (36.24)

-280.14 (98.62)

-1592.8 (283.2)

-184.34 (59.98)

-44.26 (36.24)

-140.08 (41.20)

-2091.20 (321.40)

-147.39 (48.38)

Site P-Value <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 0.02 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001

F-Value 104.7 144.8 28.8 23.6 109.4 106.2 73.0 129.8 5.2 62.9 175.2 130.3 85.2 87.2 89.1

Estimate (SE)

-2472.00 (348.70)

-7.04 (0.90) -0.35 (0.09) -412.70 (59.75)

-2076.60 (315.30)

-874.88 (166.58)

-1421.6 (195.1)

-212.40 (36.24)

33.09 (98.62)

-1506.5 (283.2)

-417.61 (59.98)

-212.82 36.24

-204.79 (41.20)

-2135.30 (321.40)

-210.37 (48.38)

Treatment P-Value 0.003 0.007

NS

0.02 <0.001 0.008 <0.001 <0.001

NS

0.01 <0.001 <0.001

NS

0.005 0.009

F-Value 8.5 7.4 5.6 13.6 7.1 3.9 20.3 6.4 14.6 20.1 8.1 7.0

Estimate (SE)

1537.80 (348.70)

3.54 (0.90) -187.02 (59.75)

1720.00 (315.30)

619.25 (166.58)

578.0 (195.1)

201.52 (36.24)

1149.4 (283.2)

304.52 (59.98)

201.09 (36.24)

1379.30 (321.40)

179.38 (48.38)

Depth:site P-Value <0.001 <0.001

NS

<0.001 <0.001 0.009 <0.001

NS

0.002 <0.001 0.009

NS

0.02 <0.001 0.04

F-Value 33.4 26.2 30.9 28.8 7.0 38.1 10.1 23.5 7.0 5.7 32.2 4.1

Estimate (SE)

2326.40 (402.60)

5.33 (1.04) 383.30 (68.99)

1953.20 (364.10)

509.33 (192.35)

1390.0 (225.2)

361.53 (113.87)

1585.9 (327.0)

183.78 (69.26)

113.75 (47.57)

2106.0 371.20

113.32 55.86

Depth:Treatment P-Value

NS NS NS NS NS NS NS

0.03

NS NS NS

0.03

NS NS NS F-Value 5.0 4.9

Estimate (SE)

-93.43 (41.85)

-92.59 (41.85)

Site:Treatment P-Value <0.001 <0.001

NS NS

<0.001 <0.001 0.04 0.004

NS

<0.001 <0.001 0.004 0.003 <0.001 <0.001

F-Value 13.9 13.2 19.5 14.9 4.4 8.4 12.7 14.7 8.5 9.1 12.3 15.5

Estimate (SE)

-1502.50 (402.60)

-3.79 (1.04) -1608.70 (364.10)

-742.11 (192.35)

-471.3 (225.2)

-121.13 (41.85)

-1165.6 (327.0)

-265.26 (69.26)

-121.97 (41.85)

-143.29 (47.57)

-1301.80 (371.20)

-219.82 (55.86)

Adjusted R-Squared 0.51 0.58 0.25 0.31 0.52 0.44 0.45 0.47 0.08 0.41 0.54 0.47 0.36 0.48 0.38


51

APPENDIX B – SPECIES LISTS

Table B1 - List of species recorded in plant surveys conducted at Jandakot Airport, with invasive

status.

Genus species Status

Acacia pulchella native

Acacia saligna native

Acacia willdenowiana native

Adenanthos cygnorum native

Allocasuarina humilis native

Amphipogon turbinatus native

Arnocrinum preissii native

Austrostipa compressa native

Banksia attenuata native

Banksia ilicifolia native

Banksia menziesii native

Baumea vaginata native

Beaufortia elegans native

Bossiaea eriocarpa native

Briza maxima invasive

Burchardia congesta native

Caladenia flava native

Caladenia sp. native

Calectasia narragara native

Calytrix flavescens native

Calytrix fraseri native

Carpobrotus edulis invasive

Cassytha sp. native

Chamaescilla corymbosa native

Chordifex sinuosus native

Conostephium pendulum native

Conostephium preissii native

Conostylis aculeata native

Conostylis juncea native

Conostylis setigera native

Croninia kingiana native

Dampiera linearis native

Dasypogon bromeliifolius native

Daviesia triflora native

Desmocladus fasciculatus native

Desmocladus flexuosus native

Ehrharta calycina invasive

Eremaea asterocarpa native

Eremaea pauciflora native


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Eucalyptus marginata native

Eucalyptus todtiana native

Gastrolobium capitatum native

Gladiolus caryophyllaceus invasive

Gompholobium tomentosum native

Haemodorum spicatum native

Hardenbergia comptoniana native

Hemiandra pungens native

Hensmania turbinata native

Hibbertia huegelii native

Hibbertia hypericoides native

Hibbertia subvaginata native

Hypocalymma robustum native

Hypochaeris glabra invasive

Hypolaena exsulca native

Jacksonia furcellata native

Lasiopetalum drummondii native

Laxmannia squarrosa native

Lechenaultia floribunda native

Lepidosperma drummondii native

Lepidosperma squamatum native

Lepidosperma tenue native

Leucopogon conostephioides native

Leucopogon insularis native

Leucopogon sp. native

Levenhookia stipitata native

Lomandra caespitosa native

Lomandra hermaphrodita native

Lomandra micrantha native

Lomandra preissii native

Lomandra sp. native

Lomandra suaveolens native

Lyginia barbata native

Lysimachia arvensis invasive

Melaleuca ryeae native

Melaleuca systena native

Melaleuca thymoides native

Nuytsia floribunda native

Patersonia occidentalis native

Persoonia saccata native

Petrophile linearis native

Philotheca spicata native

Phlebocarya ciliata native

Phlebocarya filifolia native

Pimelea sulphurea native

Podolepis gracilis native


53

Rhytidosperma occidentale native

Scaevola repens native

Schoenus curvifolius native

Schoenus efoliatus native

Scholtzia involucrata native

Solanum nigrum invasive

Sonchus oleraceus invasive

Stirlingia latifolia native

Stylidium piliferum native

Stylidium repens native

Stylidium sp. native

Tetraria octandra native

Thysanotus thyrsoideus native

Thysanotus triandrus native

Trachymene pilosa native

Ursinia anthemoides invasive

Wahlenbergia preissii native

Xanthorrhoea preissii native

Xanthosia candida native

Table B2 – List of species germinated in glasshouse experiment, with invasive status, and number of

germinants observed across treatments.

Natural Transfer

Genus species Status control treated control treated

Acacia pulchella native 0 4 0 1

Aira caryophyllea invasive 31 11 6 1

Aira cupaniana invasive 1 1 3 0

Anigozanthos humilis native 5 26 2 5

Anigozanthos manglesii native 0 20 0 0

Arctotheca calendula invasive 1 0 5 11

Austrostipa compressa native 126 91 7 3

Bossiaea eriocarpa native 3 8 1 3

Briza maxima invasive 89 33 2 1

Briza minor invasive 1 0 0 0

Bromus diandrus invasive 2 1 14 20

Calandrinia granulifera native 3 0 5 1

Calandrinia corrigioloides native 13 31 0 2

Cardamine hirsuta invasive 0 0 2 0

Carpobrotus edulis invasive 1 7 10 16

Cassytha sp. native 0 2 0 0

Centrolepis alepyroides native 152 202 57 31

Centrolepis aristata native 0 0 5 2

Centrolepis glabra native 249 566 116 67

Chamaescilla corymbosa native 116 38 17 2

Conostephium pendulum native 0 2 0 0


54

Conostylis aculeata native 0 40 0 1

Conostylis juncea native 4 20 0 0

Conostylis setigera native 0 3 0 0

Conyza bonariensis invasive 34 10 12 2

Crassula colorata native 244 329 466 336

Cynodon dactylon invasive 0 0 0 1

Dasypogon bromeliifolius native 1 1 0 0

Daviesia pedunculata native 1 0 0 0

Daviesia triflora native 0 1 0 0

Desmocladus flexuosus native 6 6 2 0

Drosera erythrorhiza native 0 1 0 0

Drosera menziesii native 0 3 0 0

Drosera platypoda native 2 1 1 0

Drosera platypoda native 3 5 1 0

Ehrharta calycina invasive 0 1 0 5

Euphorbia peplus invasive 1 0 0 1

Gamochaeta coarctata invasive 1 0 1 1

Gladiolus caryophyllaceus invasive 48 13 12 0

Gnaphalium indutum native 0 0 0 1

Gnephosis angianthoides native 2 0 64 26

Gompholobium tomentosum native 5 62 6 20

Hensmania turbinata native 1 0 0 0

Hibbertia hypericoides native 1 0 4 0

Hibbertia sp. native 0 1 0 0

Hibbertia sp. native 2 1 0 0

Hibbertia subvaginata native 8 7 3 1

Homalosciadium homalocarpum native 21 26 1 4

Hypocalymma angustifolium native 1 1 0 0

Hypochaeris glabra invasive 66 60 13 9

Isolepis marginata native 617 1257 145 136

Isotoma hypocrateriformis native 1 37 1 40

Jacksonia furcellata native 1 3 0 0

Juncus sp. unknown 1 8 13 17

Laxmannia ramosa native 1 5 1 0

Laxmannia sessiliflora native 164 152 57 29

Lechenaultia floribunda native 8 169 3 12

Lepidosperma drummondii native 1 0 0 0

Leucopogon conostephioides native 262 173 19 28

Leucopogon sp. native 14 4 1 3

Levenhookia pusilla native 15 3 0 3

Levenhookia stipitata native 68 85 6 4

Lolium sp. invasive 42 14 2 3

Lomandra caespitosa native 1 2 0 0

Lomandra hermaphrodita native 0 3 0 0

Lomandra preissii native 0 0 0 1

Lomandra sp. native 1 0 0 0


55

Lotus sp. invasive 0 0 1 1

Lyginia barbata native 3 1 0 0

Lysimachia arvensis invasive 1 0 0 0

Medicago sp. invasive 0 0 1 0

Microtis sp. native 5 1 1 0

Patersonia occidentalis native 1 3 2 0

Phlebocarya ciliata native 2 2 0 0

Phlebocarya filifolia native 0 1 0 1

Podolepis lessonii native 23 74 0 0

Podotheca chrysantha native 0 0 1 0

Podotheca gnaphalioides native 9 14 6 4

Poranthera microphylla native 21 46 3 4

Poranthera microphylla native 75 346 35 21

Rhodanthe corymbosa native 60 47 2 1

Rhodanthe laevis native 6 3 0 0

Romulea rosea invasive 0 2 11 1

Sagina apetala invasive 0 0 1 0

Sagina apetala invasive 0 0 2 0

Schoenus curvifolius native 1 1 0 0

Solanum americanum invasive 1 0 0 0

Solanum nigrum invasive 3 2 3 1

Sonchus oleraceus invasive 1 1 5 0

Spergula arvensis invasive 0 0 1 0

Stylidium brunonianum native 3 141 1 4

Stylidium emarginatum native 132 204 15 26

Thysanotus manglesianus native 4 1 2 0

Thysanotus sp. native 3 2 0 1

Thysanotus triandrus native 1 1 1 0

Trachymene pilosa native 341 179 21 32

Trifolium campestre invasive 4 5 2 0

Unknown_01 invasive 8 5 1 1

Unknown_02 native 0 1 1 0




Unknown_06 unknown 0 0 0 1












56










Ursinia anthemoides invasive 86 56 0 8

Vulpia sp. invasive 65 25 7 2

Wahlenbergia capensis invasive 13 32 9 2

Wahlenbergia preissii native 147 222 7 15

Xanthosia candida native 2 5 1 1

Totals 3624 5547 1297 1083

soil seed bank dynamics in transferred topsoil...soil seed bank dynamics in transferred topsoil...

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