Invasion pattern of pinus pinaster from plantation into bushland and wetlands in the gnangara mound western australia

THAI NGUYEN UNIVERSITY
UNIVERSITY OF AGRICULTURE AND FORESTRY

CHRISTINE ANNE D.S. BELEN
INVASION PATTERN OF PINUS PINASTER FROM PLANTATION INTO
BUSHLAND AND WETLANDS IN THE GNANGARA MOUND, WESTERN
AUSTRALIA

BACHELOR THESIS

Study Mode : Full- time
Major
Faculty

: Bachelor in Environmental Science and
Management
: International Programs Office

Batch

: K45- Advanced Education Program

Thai Nguyen, 20/11/2017


Thai Nguyen University of Agriculture and Forestry
Degree Program Bachelor in Environmental Science and Management
Student Name
Christine Anne Delos Santos Belen
Student ID
DTN1454290060

Thesis Title
Invasion pattern of Pinus pinaster from plantation into bushland
and wetlands in the Gnangara Mound, Western Australia
Supervisor
Dr. Do Xuan Luan & Dr. Eddie Van Etten
Abstract: The increase of planted forest area worldwide has lead to the extensive
planting of exotic species; however, these species are often invasive and can spread to
neighboring natural ecosystems. One of the most planted exotic species globally is
Pinus (pine trees), particularly Pinus pinaster and understanding its invasion pattern
can raise awareness and can serve as a basis to provide appropriate suggestions to
prevent its spread. In this study, the researcher aimed to identify the invasion pattern of
P. pinaster into adjacent bushland and wetlands in Gnangara Mound, Western
Australia and to determine the factors that influence the spread like fire history. The
study was done by counting the P. pinaster wildlings on a measured 1-hectare quadrat
on every selected site of each natural ecosystem around the plantations: Banksia
woodland, Eucalyptus-Banksia woodland and Melaleuca woodland (wetlands). The
researcher observed that Melaleuca woodland contained the most number of pine
wildlings (465 pines) and showed a distinct invasion pattern, which are the common
two-phase pattern and the Hubbell model. It portrays that the pine wildlings found are
greater in the distance close to the plantation and decreased with distance from the
edge. Meanwhile, both Banksia and Eucalyptus-Banksia woodlands showed a few
number of wildlings (7 and 12 pines, respectively) and no definite pattern of invasion.
The vulnerability of wetlands to pine invasion can be associated with its land
characteristic and resource availability while the resistances of the other ecosystems
are influenced by its composition, dense vegetation (no disturbance) and lack of
nutrient availability for wildlings. Moreover, since P. pinaster species are obligate
seeders and release high number of seeds after fire, burnt Melaleuca woodland sites
showed higher number of wildlings (331 pines) than the unburnt sites (134 pines).
Keywords: Pinus pinaster, pine plantations, invasion pattern,
Number of page

48
Date of Submission
November 20, 2017
ii


ACKNOWLEDGEMENT
The researcher wishes to extend her grateful appreciation to the following
people for their valuable contribution in order to make this research possible. First and
above all, thanks be to God for giving the researcher life, strength, love and courage
throughout this research. Thanks be to God for all His unspeakable gifts. Second, to
her family that never fails to support, guide and love her to fulfill her dreams and to
provide her all the great things possible. To the Advanced Education Program headed
by Dr. Duong Van Thao and to the TUAF officials for their assistance to their students
as well as to Edith Cowan University officials that made this exchange research
program possible. To the researcher’s thesis adviser in Australia, Dr. Eddie Van Etten,
for his warm welcome, never-ending support and guidance throughout the research
process. To the researcher’s thesis adviser in Vietnam, Dr. Do Xuan Luan for his
advices and support. To all the amazing people that the researcher met in Australia that
made her stay there easier and beyond great. To her beloved friend, Mishel Ranada,
who is with her in Australia and helped her all the way. To all her classmates in K45
and to all her Filipino friends, especially her roommates, for the moral support and
encouragements they gave. Lastly, the researcher offers her regards to all of those who
supported her in any respect during the completion of this research. May God bless us
all!

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TABLE OF CONTENT

LIST OF FIGURES .............................................................................................................................. 1
LIST OF TABLES ................................................................................................................................ 1
LIST OF ABBREVIATIONS............................................................................................................... 1
PART I. INTRODUCTION ................................................................................................................. 2
1.1 Research Rationale ........................................................................................................................ 2
1.2 Research’s Objectives ................................................................................................................... 6
1.3 Research questions ........................................................................................................................ 6
1.4 Limitations .................................................................................................................................... 7
PART II. LITERATURE REVIEW .................................................................................................... 8
2.1 Pinus.............................................................................................................................................. 8
2.1.1 Pinus as invasive species............................................................................................................ 9
2.2 Pine invasion in the southern hemisphere ................................................................................... 10
2.2.1 Pine invasion in Australia ........................................................................................................ 12
2.3 Factors of Invasion ...................................................................................................................... 13
2.3.1 Invasion pattern ........................................................................................................................ 17
2.3.2 Impacts of Invasion .................................................................................................................. 18
2.4 Pinus pinaster.............................................................................................................................. 18
2.4.1 Pinus pinaster plantation in Perth, Western Australia ............................................................. 19
2.4.3 Regeneration of Pinus pinaster after fire ................................................................................. 20
2.4.4 Pinus pinaster invasion ............................................................................................................ 21
PART III: METHODS ....................................................................................................................... 23
3.1 Materials...................................................................................................................................... 23
3.2 Geographical Information System (GIS) .................................................................................... 23
3.3 Site selection ............................................................................................................................... 24
3.4 Field sampling and Data collection ............................................................................................. 25
3.6 Statistical analysis ....................................................................................................................... 26
PART IV: RESULTS .......................................................................................................................... 27
4.1 P. pinaster plantation edges ........................................................................................................ 27
4.2 Number of pine wildlings ............................................................................................................ 28
4.1 Fire history in relation with wilding regeneration ....................................................................... 30

4.2 Different types of natural vegetation in relation with wildling regeneration .............................. 31
PART V: DISCUSSION AND CONCLUSION ................................................................................ 32
5.1 Discussion ................................................................................................................................... 32
5.1.1 Invasion pattern ........................................................................................................................ 32
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5.1.2 Regeneration based on natural habitat type .............................................................................. 34
5.1.3 Relation of fire history ............................................................................................................. 36
5.1.4 Management of pine wildlings ................................................................................................. 36
5.2 Conclusion................................................................................................................................... 37
REFERENCES .................................................................................................................................... 39
APPENDICES

v


LIST OF FIGURES
Figure 1: Total P. pinaster wildlings density (means/ha) distribution in Melaleuca
woodland (wetlands) in relation to distance from the ecosystem boundary (meters) ...29

LIST OF TABLES
Table 1: A table summary of the different types of edges found adjacent to Pinus
pinaster plantations .......................................................................................................27
Table 2: A summary of the percentage cover of each of the natural ecosystems .........27
Table 3: A summary of the number of wildlings surveyed from all of the eighteen sites
.......................................................................................................................................28
Table 4: ANOVA results with: “Sample” being the three natural ecosystems and
“columns” as the fire history .........................................................................................30

LIST OF ABBREVIATIONS
Abbreviation

Meaning

DPIE

Department of Primary Industries and Energy

ESRI

Environmental Systems Research Institute

FPC

Forest Product Commission

GIS

Geographic Information System

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PART I. INTRODUCTION
This chapter presents the rationale of the study, the objectives, research
questions and limitations of the study.
1.1 Research Rationale
The global demand in forest products, such as timber, and the need to fulfill
various environmental concerns has led to the increase of planted forest area

worldwide (Dodet & Collet, 2012). In order to sustain such needs, many countries are
planting exotic tree species for they are fast growing, easy to establish and have low
shade tolerance. Unfortunately, many of these exotic species used for forest
plantations are considered invasive and can spread into neighboring natural
ecosystems (Richardson, 1998). Most of the time, invasive species are receiving
attention only if the situation becomes serious, that is, once they have escalated over
large areas and dominated nearby ecosystems. Such levels of invasion can result in
major alterations of ecosystem structure and function, and is now one of the major
threats to the Earth’s biodiversity (Williams & Wardle, 2007). Thus, understanding the
invasion pattern of these exotic species can help in preventing and managing their
establishment into natural ecosystems.
One of the most common planted exotic trees globally are species of Pinus,
commonly known as “pines”. Pine species have been planted to areas outside their
natural ranges because of its economic importance, most especially in the Southern
Hemisphere. Since pines can provide fast-growing, high-quality timber products,
plantations of it have resulted in invasion problems in many areas of the world
(Richardson, 1998). The inordinate spreading of Pinus from its plantation into natural
2


ecosystems has been a constant problem in countries like New Zealand (Hunter &
Douglas, 1984; Ledgard, 1988), South Africa (Richardson & Brown, 1986), Chile
(Bustamante & Simonetti, 2005) and Australia (Richardson et al., 1994). Pine
invasions are creating a serious dilemma in New Zealand for they displace the native
biodiversity and alter both aesthetic and environmental values, but also provide an
important source of revenue via exports and local consumption. Moreover, South
Africa are facing problems in managing grazing lands, protected areas and water sheds
due to the domination of Pinus species in different vegetation (Richardson et al.,
1997). The biological invasions of exotic species like pines within natural ecosystems
are now the second greatest danger that is disrupting the world’s biodiversity (Walker

& Steffen, 1997)
Among the cultivators of pine plantations worldwide, Australia is one of the
countries with the largest area of such plantations, with more than one million hectares
nationwide (Australian plantation statistics, 2016). According to Western Australia’s
Forest Products Commission, pine plantations were established in order to sustain the
State’s needs for timber products contributing almost $1.06 billion per year to the
economy. Most area of the pines plantations are composed of species called Pinus
radiata and Pinus pinaster (which is commonly known as maritime pine) though P.
pinaster is more common around Perth and in the northern parts of the Southwest
Region. As stated by Western Australia’s FPC report, P. pinaster was originally from
western Mediterranean Basin and introduced in Western Australia in 1896. P. pinaster
species from Portugal, specifically from Leiria province, showed the best form and
growth rate for the sandy soils during the plantation trials in 1926. Currently, P.
3


pinaster plantations are situated in Western Australia regions of Avon Wheatbelt,
Jarrah Forest and Swan Coastal Plain (Keighery et al., 2013).
In particular, the Gnangara Mound is considered as one of the biggest P.
pinaster plantations in Western Australia. It is situated in the northern part of Perth
metropolitan area on the Swan Coastal Plain and is an unconfined groundwater system
with an extensive area of 2200 km2 (Stock et al., 2013). It is composed of different
dune systems, which also act as superficial aquifer that provides fresh drinking water
throughout Perth. According to Western Australia’s Gnangara Sustainability Strategy
Report, the Gnangara mound mainly includes three maritime pine plantation systems
(Gnangara, Pinjar and Yanchep) which, at 2009, covered an area of 22000 hectares
(ha) though pine clearing is evident. Aside from its timber importance, pines are being
harvested to increase the groundwater recharge in Gnangara Mound, especially in the
southern parts, as groundwater levels have been declining. However, some of the pines
are being reserved to serve as food and habitats for Carnaby cockatoo while other

pines are being replanted after the harvest where groundwater is not being used like in
the northern part of Yanchep. Remnant native vegetation can also be found within
(through wetlands) and adjacent to the pine plantations.
In general, the Gnangara Mound is composed of three different types of native
vegetation surrounding the pine plantations. Banksia woodland (normally a mix of
Banksia menziesii and B. attenuata) can be found in Bassendean dunes (up to 2 million
years old), Eucalyptus-Banksia woodland which is situated in Spearwood dunes (~0.8
million years old) and Melaleuca vegetation that are found in low lying areas where
groundwater reaches near or above the surface in winter (commonly referred as
4


wetlands) within the pine plantations (Stock et al., 2013). In detail, Spearwood dune
can be divided into two sub-systems: the Karrakatta complex which has limestone near
surface and tuart (E. gomphocephala) woodland, and Cottlesloe complex which has
Jarrah (E. marginata) – Marri (Corymbia calophylla) – Banksia woodland. Because P.
pinaster has the ability to regenerate outside its plantations, it can potentially spread
into the mentioned native vegetation above.
According to Alia et al. (1999), P. pinaster fruit production begins at an early
age between 10-15 years old with a regular recurrence of abundant crops every 1 or 2
years, which is why it possesses high reproductive rates and distribution. However,
aside from the fact that it has fast growing characteristics and can reproduce quickly,
the major disadvantage of P. pinaster is its susceptibility to fire.
P. pinaster is considered as one of the coniferous forest types, which frequently
suffer the effects of fire due to its highly flammable resinous needles and woods. In
Spain, the regeneration of P. pinaster species after wildfires has been widely studied
by various authors (Thanos & Marcou, 1991; Trabaud & Campant, 1991; Perez &
Moreno, 1998). According to these studies, rapid natural regeneration of maritime pine
is highly possible because of fires. P. pinaster are obligate seeders which means that it
responds to fire through rapid seed dispersal and that the seedlings reappearing after

the fire originates from the soil seed bank through either by dispersion from
neighboring areas or from the seeds held within the cones in the canopy. Due to
frequent fires within maritime pine communities, it has also acquired series of adaptive
characteristics such as thicker bark and a high yield of serotinous cones. Because of

5


this, P. pinaster displays the ability to colonize burn sites and neighboring ecosystems
besides it.
Even though there has been extensive research already conducted in different
parts of the world concerning the invasion and regeneration of P. pinaster into natural
ecosystems, there are still insufficient studies in regards with its invasion patterns in
the area of Perth, Western Australia. Determining the invasion pattern of P. pinaster
can lead to identifying the possible impacts of the spread and can help in future
management of such natural vegetation as well as the pine plantations.
1.2 Research’s Objectives
The main objective of this study is to identify the invasion patterns of Pinus
pinaster, growing in plantations on the Gnangara Mound, into native bushland
surrounding the plantations, as well as habitats within the plantations (wetlands). A
secondary objective is to determine the factors influencing the invasion. This research
will provide awareness as to threat posed by maritime pines to the natural vegetation
and will serve as a reference to provide appropriate suggestions for the prevention of
pine invasion.
1.3 Research questions
This research study was guided by the following research questions in
accordance to the objectives of the study:
A. To identify the invasion patterns of Pinus pinaster into bushland
surrounding the plantations and habitats within the plantations
(wetlands).

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a. Is there a certain invasion pattern of P. pinaster into bushland
surrounding the plantations and wetlands within the plantations?
b. How serious is the P. pinaster invasion based on its density and
estimated age (number of nodes)?
c. Are there different patterns of invasion in different vegetation
types?
B. To determine the factors influencing P. pinaster’s invasion.
a. Does the history of prescribed fires and wildfires affect the
regeneration of P. pinaster into bushland and wetlands?
b. Are there any other potential factors of the spreading of P.
pinaster based on its invasion types?
1.4 Limitations
Even though the research study has reached its objectives, some limitations
influenced the research process and result findings. First, because the time given to
conduct the research is only three months, only a few sites were selected and sampled.
Hence, in order to provide more precise results, the research should include more sites
on each category. Another is the fire history data provided by Western Australian Land
Information Authority (Landgate) Firewatch. The yearly-burnt areas maps were found
not entirely accurate for some of the sites observed by the researcher shows evidence
of fire, contrary to what the data presented. According to Landgate Firewatch, not all
fire hotspots are detected by their satellites therefore heat sources that are too small,
not hot enough, or obscured by thick smoke or cloud are not included in their burnt
areas map.
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PART II. LITERATURE REVIEW

2.1 Pinus
Pinus, commonly known as pines, is the most well-known of the large
conifers. It is a genus with around 115 – 120 species of coniferous trees of the
Pinaceae family and is widely dispersed worldwide but is native primarily in the
Northern Hemisphere from the near-arctic to tropical regions. Environmentally, pine
species are well adapted to a variety of climates and requires full sunlight for growth
and production. Pines originated across almost all of the regions in Northern
Hemisphere and specifically abundant in large forest type areas of Europe, Central
America, North America, North Africa and some Asian countries. (Keeley, 2012).
Pines are fast growing species and are very famous for its timber value around
the world. This timber is used in manufacturing of furniture, construction, panelling
and flooring. Another economic value of pines is in the paper-product industries, as
well as being a source of rosin, oils, turpentine and wood tars. Pines are also famously
cultivated for ornamentals and shade trees, as well as planted for reforestation and land
improvement in several parts of the world (Pereira, 2002).
Now that the demand for timber is increasing dramatically, pines are planted
extensively both throughout their natural range and in Southern Hemisphere, where
they are mostly not native. Pines are already introduced to various Southern
Hemisphere countries such as South Africa, New Zealand, Argentina, Chile, Brazil,
and Australia (Richardson et al., 1994). Whenever large plantations of pines have been

8


established around the world, invasion problems have followed not long after
(Richardson, 1998).
2.1.1 Pinus as invasive species
Pines are known to be invasive species and are often used as the model group in
studying plant invasion throughout the years. According to one of David M.
Richardson’s studies, pines are utilized for this kind of research since almost all of its

species are already planted extensively in many areas, providing them the
opportunities over many years to sample many potentially invasable habitats
(Richardson, 2006). The reasons as to why pines are one of the most influential of all
invasive plants especially in the Southern Hemisphere have been widely studied by
various authors (Richardson, 2006; Higgins & Richardson, 1998).
Among all the groups of conifers, Pinus is affirmed to be as invasive as any
angiosperm family encompassing pre-dominantly woody taxa. Pines are most clearly
distinguished from all other conifers in their role of aggressive post disturbance
colonizers and are now considered as the most successful conifers in the age of
biological invasions (Richardson & Rejmanek, 2004). In the Southern Hemisphere, 16
Pinus species have already been listed as invasive species particularly in South Africa,
South America, New Zealand and Australia (Higgins & Richardson, 1998).
According to Higgins and Richardson (1998), there are several key plant and
environmental attributes, which promote pine invasions in the Southern Hemisphere.
These are small seed mass, short juvenile periods, high degree of serotiny, low fire
tolerance, short intervals between large seed crops, intermediate disturbance frequency,

9


high latitudes, long residence times and a large extent of human planting. Furthermore,
pines have simple regeneration requirements and exhibit a very wide range of
ecological adaptations such as coping with fire, seed disposal, enhancing its ability to
survive in small populations and rapid population growth. Moreover, Pinus species are
known to be light dependent and fast growing, regenerating as even-aged stands even
after disturbance to retain its position in the landscape (Richardson & Rejmanek,
2004).
In addition, Richardson (2006) indicated that pines have been successful
invaders because they are less resilient on mutualists than most woody plants and that
pine pollen is very copious and broadly dispersed via wind. Seeds of most pine species

are also dispersed by wind and barriers to invasion through the absence of appropriate
mycorrhizal fungi, which existed prior to European colonization in many parts of the
Southern Hemisphere, have largely been overcome (Richardson et al., 1994, 2000).
Furthermore, Higgins and Richardson (1998) discovered that pine trees are also very
dependent on the ecosystem type as an invader. Pines more often spread in ecosystems
like grassland and shrubland as well as in forests and woodlands, only if there have
been a significant disturbance.
2.2 Pine invasion in the Southern Hemisphere
Pine invasions have been already recorded in various places in the Southern
Hemisphere, especially where large populations of pines have been established. The
dispersal of pine seeds from plantation into adjoining natural ecosystems has initiated
large-scale invasions resulting in the disruption of the ecosystem’s function and
structure (Richardson & Rejamnek, 2004). Among all the Southern Hemisphere
10


countries, Australia, New Zealand and South Africa are facing very serious problems
of pine regeneration into natural ecosystems.
In New Zealand, several data were recorded to monitor the invasion of Pinus
species. In 1975, Central Volcanic Plateau was invaded by Pinus contorta covering
30,000 ha of its land while in 1990, 17,500 ha (0.8% of the whole area) has been
dominated by pines in South Island high country (Richardson et al., 1994). The most
recent record in New Zealand shows that approximately 150,000 ha of land are already
been affected by Pinus invasion (Ledgard, 2001).
Most of the studies about pine invasions were conducted in South Africa
providing them more accurate quantitative data and better understanding about it
(Richardson, 2006). Pinus pinaster is by far the most invasive Pinus species in South
Africa invading more than 300,000 ha, mostly in fybos (low shrubland) vegetation. It
is followed by P. radiata covering 34,000 ha (Richardson et al., 1997). Pinus
regeneration in natural ecosystems is causing major concerns in South Africa because

of the pines ability to potentially reduce the stream flow (Versfeld & Van Wilgen,
1986). In 1995, they established the “Working for Water Programme” to control the
species invasion while in 2003, 5 million dollars was allotted to clear 2,400 ha of
Pinus invasion in South Africa (Marais et al., 2004).
More pine invasions documented in the Southern Hemisphere include the
spread of P. pinaster in Uruguay, P.koraiensis and P. luchuensis in Japan, P. patula in
Madagascar and P. caribaea in New Caledonia. Moreover, Pinus species like P.
halepensis, P. monticola, P. ponderosa, P. contorta, P. elliotti, P. sylverstris and P.

11


taeda have all regenerated in natural ecosystems of Argentina while P. elliotti, P.
taeda and P. kesiya successfully invaded parts of Brazil. On the other hand, other
countries like Colombia and Kenya recorded no invasion despite its large pine
plantations (Richardson et. al., 1994).
2.2.1 Pine invasion in Australia
Pines were introduced in Australia and have been continuously cultivated
rapidly in response to the Australian Government policy “Plantations for Australia:
2020 Vision”. Its goal is to expand Australia’s total plantation area between 1996 and
2020, leading to annual increase of almost 10,000 ha (DPIE, 1997). Current record
shows that more than 1 million ha of pine plantations are growing across the country.
Pinus radiata is by far the most commonly cultivated Pinus species with over 770,000
ha followed by Southern pines, P. taeda, (~156,000 ha) and maritime pine, P. pinaster,
(~42,000 ha) (Australian plantation statistics, 2016).
Although there are no Pinus species yet reported in Australia’s Weeds of
National Significance, a number of it are already considered as invasive species
including P. caribaea,P. contorta, P. elliottii, P. halepensis, P. jeffreyi, P. nigra, P.
pinaster, P. ponderosa, P. radiata and P. taeda (Richardson, 2006). Although records
of pine invasion in Australia are somehow rare, some places were noted to be affected

by it. In South-east Australia, P. radiata is considered highly invasive while P. radiata,
P. nigra and P. pinaster dominated natural ecosystems of Victoria. In fact, it have
been noticed to be regenerating into ecosystems like lowland grasslands, grassy
woodlands, dry and damp scherophyll forest, heathland and riparian vegetation and
has been listed as a very serious invader in Victoria (Carr et al., 1992).
12


Moreover, P. radiata wildings have also been recorded in native ecosystem and
roadsides adjacent to plantations in South of Australia (Muyt, 2001). It has been listed
as naturalized in several regions of the state and invasions have been observed in the
Mount Loft Rangers region and Lower Eyre Peninsula (Virtue & Melland, 2003).
Furthermore, P. radiata invasion was recorded to be more serious in New South Wales
where majority of its plantations are located (Williams & Wardle, 2007).
Other pine invasions recorded in Australia include spread of pines in Western
Australia and Tasmania as well as P. elliottii covering habitats in east coast of
Australia. In Queensland, P. radiata, P. elliottii, P. caribea and its hybrid have been
regenerating from planted areas to adjacent ecosystems. Moreover, P. brutia has been
spreading in South Australia as well as P. halepensis wildings invading in mallee and
grassy woodlands. P. pinaster has been a noted invader in New South Wales, Victoria
and South Australia while P. nigra has limited spread in both Victoria and Adelaide
(Muyt, 2001; Carr et al., 1992; Swarbrick & Skarrat, 1994).
2.3 Factors of Invasion
Several studies have been made in many parts of the world to identify the
factors that affect the invasion of pines. Such factors can be divided into five types:
time, ground-cover characteristics of invaded areas, disturbance, resident biota and
fire.

Time

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Time is an integral factor of invasion yet it is hard to identify how it operates in
determining the success of pines as an invader, since many factors changes with time
(Richardson et al., 1994). Opportunities for seed release, long-distance dispersal and
seedling establishment are episodic and do not always coincide. For example, seed
recruitment of several pine species is restricted to a short period after fire. Therefore,
more time after fire can generate greater propagule pool, better chance of recruiting
offspring and greater probability of invasion. However, on a normal pine plantation,
most pine species take between 7 and 15 years to produce viable seeds, which is the
minimum period between introduction and the first invasion episode (Richardson et al.,
1994). Time is a valuable function that captures all eventualities to start an invasion.
Ground-cover characteristics of invaded area
The major ecosystem types can be ranked according to their vulnerability to
Pinus invasions (all other factors being equal) as follows: forest < shrubland <
grassland << dunes < bare ground. Bare ground and dunes can be instantly invaded by
pines, like in coastal dunes between Montevideo and Punte del Este in Uruguay that
were covered by P. pinaster. Grassland types that were recorded to be invaded consist
of a wide range from natural or semi-natural “rangeland” groupings (temperate, moist
and subtropical), “improved” grasslands (pasture) and grassland exposed to grazing
pressure. Pines that have spread in shrublands include fybos and dwarf shrublands in
South Africa and Bankisa (proteaceae) woodland in Australia. On the other hand,
undisturbed and intact forests appear to be resistant of pine invasions though some
cases like the coastal forest in Eastern Cape as well as Eucalyptus forests and disturbed
dry sclerophyll forest in Australia were invaded (Richardson et al., 1994).
14


Disturbance

Disturbance has been a crucial factor that plays a major role in facilitating
invasions. Man-modified disturbances like herbivore pressure (grazing and trampling),
prescribed fires and mechanical clearing of vegetation are commonly associated as the
cause of invasions. All recorded pine invasions into forests show signs of severe
disturbance as well as most shrubland sites, though some studies indicate that invasion
can occur even without disturbance of sites. Even invaded grasslands noted in
Australia, South Africa and New Zealand have a history of perturbation (Richardson et
al., 1994). Due to disturbances, invadability of an ecosystem increases because of
reduced competition from resident plants that creates an invasion window (sensu
Johnstone, 1986).
Resident biota
The plant and animal community of the ecosystems adjacent to pine plantations
can also influence the degree of invadability. The presence or absence of a particular
or group of species is important to predict the invasion of pines (Richardson et al.,
1994). For instance, the open forest of Eucalyptus blakeyli in North-eastern of Victoria,
and fybos covered by Protea nitida are resistant to the spreading of pines (Richardson
et al., 1992). On the contrary, Dracophyllum Subulatum Hook f. shrubland and
Chionochloa rigida (Raoul) Zotov. fussock grassland in New Zealand are easily
invaded by P. contorta and P. nigra respectively (Richardson et al., 1994). There is
still no definite list of species that are resistant or susceptible to Pinus invasion.
15


Various vertebrates can also be responsible for either controlling or promoting
pine regeneration to adjacent ecosystems by removing competing vegetation, by
destroying pines or by dispersing its seeds (Richardson et al., 1994). For example,
possums (Wills & Begg, 1986), rabbits (Belton & Ledgard, 1991), and hares (P.A.
Williams, pers, obs) may check the invasion of pines in New Zealand by browsing its
seedlings. On the other hand, reduced population of rabbits in Eucalyptus forests in
Australia had resulted to more successful invasion of P. radiata. Moreover, seeddispersion of cockatoos opened a window for pine spread in Australia (Richardson et

al., 1994; Buchanan, 1989). Vegetation and animal community are indeed factors that
can promote or be a barrier to pine invaders.
Fire
Naturally occurring fires or even prescribed fires can influence the spread of
Pinus species. Some species such as P. radiata and P. pinaster are known to be fire
evader because of its tendency to releases stored seeds after high intensity fires
(Williams & Wardle, 2007). Such species can endure high temperature with the help
of their cones to protect seeds and maintain its viability in post-fire environment
(Linhart, 1978). Fire stimulates the release of large amounts of seed from the
serotinous cones and can create favorable conditions for germination and
establishment (Hanley & Fenner, 1998; Trabaud, 1995). Fires are categorized to be
disturbance hence serving as a window for pine invasion because of lack of
competition.

16


2.3.1 Invasion pattern
Invasion of pines are usually cause by wind-dispersed seedlings, which
involves a two-phase process: (1) immigration and establishment; and (2) population
growth (Richardson et al., 1994). Most common distances from the source is 100 m
but for some cases, it ranges from 8 km to 25 km due to strong winds and sites located
on ringes or hill tops (Ledgard, 1988; Lee, pers. comm.). Dominant winds during times
of seed release will govern seed distribution and result in a higher propagule pressure
and greater risk of invasion (Richardson et al., 1992).
A study by Allen and Lee (1989) described the invasion pattern of pines in New
Zealand, particularly in Chionochloa rigida tussockland. After the seed-dispersal
through wind, the growth and establishment of P. nigra and P. contorta were enhanced
due to its close proximity to tall tussocks and soon overtop the original vegetation.
Wildings population eventually increases as seeds are released regularly or, in the case

of serotinous species, en masse soon after a major disturbance such as fire (Richardson
et al., 1994).
Moreover, other documented invasions like the regeneration of P. pinaster in
South African fynbos (Kruger, 1977; Richardson & Cowling, 1995), P. radiata in New
Zealand and other more cases (Bannister, 1965; Richardson & Brown, 1986) showed
similar two-phase process but were caused by mammals. Seedlings clumped around
the pine trees attracted vertebrates and were dispersed. Established and scattered pine
wildlings increases as population grow after fires (Richardson & Cowling, 1995).

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2.3.2 Impacts of Invasion
According to Richardson et al. (1994), pine wildlings can dominate or overtop
the natural canopy of invaded ecosystems. This can result to marked shifts in the
relative abundance of native biota and will alter the structure and function of the
original ecosystem. For instance, invasion of P. pinaster and P. radiata in the Cape
Province of South Africa resulted to conversion of fynbos to pine forest, leading to
extinction of many indigenous plants (Richardson & Van Wilgen, 1986; Richardson et
al., 1989). This case also happened in New Zealand where pines suppressed the
indigenous vegetation in tussocklands ecosystem (Ogle, 1976; Watt, 1986). Moreover,
Springett (1976) noted the pines in Western Australia had lower rates of
decomposition than adjacent native woodland while several studies stated that pine
wildlings are less useful as wildlife habitat compared to native habitats like Eucalyptus
forests (Mcllroy, 1978; Friend, 1980, 1982; Recher, 1982).
2.4 Pinus pinaster
Pinus pinaster, commonly called as maritime pines, is a widespread conifer tree
that originated from the Western Mediterranean. This Pinus species can be commonly
found growing well in temperate-warm locations and can be found from coasts to
high-altitude Mountains. It is a fast growing and light demanding species and is wellknown for its “ecologically-versatile” characteristics presenting remarkable genetic

variation (Pereira, 2002; Alia et al., 1996; Praciak et al., 2013).
In terms of regeneration, P. pinaster can only regenerate from its seeds
(obligate seeders). Its seeds have large wings as a specialized wind dispersal structure
that results to long distance dispersion (Fernandes et al., 2016). Moreover, because P.
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pinaster is an obligate seeder and has serotinous cones, it usually responds to fire
through rapid seed dispersal (Calvo et al., 2007). It can maintain a long-term
permanent seed bank in its serotinous cones, which will open and spread to
neighboring areas after fire (Daskalakou & Thanos, 1996; Rodrigo et al., 2004). Many
studies already explained the influence of fire on P. pinaster seeds (Torres et al., 2006;
Calvo et al., 2007; Torres, 2002).
P. pinaster has increased in presence not only in other parts of the Northern
Hemisphere but also in the Southern Hemisphere. It has been extensively planted
outside its natural range, like in Australia, New Zealand, South America, South Africa,
and United States, mainly due to its economical and environmental importance. P.
pinaster has been used for its major product, which is wood that covers a broad range
of final products such as furniture, construction wood and poles. It is also utilized for
soil protection, reforestation of degraded areas and dunes stabilization. Because of its
worldwide demand, it has been considered as a highly invasive species especially in
the Southern Hemisphere (Pereira, 2002; Higgins & Richardson, 1998).
2.4.1 Pinus pinaster plantation in Perth, Western Australia
P. pinaster plantations in Perth, Western Australia are mainly located on the
Gnangara Groundwater Mound of the Swan Coastal Plain, just north of Perth, which is
composed of three main areas: Gnangara, Pinjar and Yanchep. The establishment of
these plantations near Perth first started in mid-1920s in order to meet the state’s
demand for timber (Valentine & Stock, 2008). The pine plantations on the whole
Gnangara Mound are said to provide timber for up to 25 years from 2003 (Gnangara
Sustainability Strategy, 2009). The extensive planting first began in Gnangara area

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with most recent plantings dating from 1989-1999. In Pinjar, most of the maritime
pines were planted from 1970-1978 while the oldest pines in Yanchep were planted
from 1961-1969, though more than half of the plantation were established after 1970
(Finn et al., 2009).
Recent data shows that there are 22 000 ha of pine plantations within the
Gnangara Mound and only 5 000 ha of it remains. Remnants natural bushland can be
found adjacent to the pine plantations like Banksia woodland and Eucalyptus-Banksia
woodland as well as within the plantations like Melaleuca woodland. The existing P.
pinaster plantations provide environmental benefits and serve as an important food
source for Carnaby’s black Cockatoos; the State’s indigenous and threatened bird
(Gnangara Sustainability Strategy, 2009; Stock et al., 2013).
2.4.3 Regeneration of Pinus pinaster after fire
Among other conifer communities, pines frequently suffer the effects of fire
(Trabaud & Campant, 1991). In particular, P. pinaster contains high resin content
hence producing and spreading flames quite quickly (Elvira & Hernando, 1989).
According to Torres et al. (2006), the seeds of P. pinaster showed greater sensitivity to
high temperatures compared to other species in the Pinus family. In order to adapt to
frequent fires, P. pinaster tends to produce an abundant quantity of serotinous cones to
maintain the survival of its seeds. Regeneration of P. pinaster after fires had been
widely studied by various authors (Calvo et al., 2007; Calvo et al., 2003; Alvarez et al.,
2007).

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