A plant community is a characteristic
group of plants that grow naturally
together in a particular environment. The
composition of a plant community is
determined by a complex interaction of
several factors including climate, soil
type, position in the landscape and
competition between plant species.
Wetlands are dynamic environments that
can experience natural fluctuations in both
water level and water quality. As a
consequence some wetland plants are able
to tolerate both flooding and short periods
of drought within a single year.
There are two broad categories of wetland vegetation.
• Aquatic macrophytes are plants that live either
completely submerged or floating or have some small
portion of the plant emerging from the water. They may
be attached (for example Potamogeton - Pondweed) or
unattached to the sediment (for example Lemna -
• Emergent macrophytes are wetland plants which are
always rooted in the sediment and whose growth habit
results in the plant protruding above the water surface.
For example Baumea articulata (Jointed twigrush) and
Emergent macrophytes are able to reproduce by either
vegetative means or by the production of seed. Vegetative
reproduction is more common and much more rapid than
reproduction by seed. It involves growth of a below ground
rhizome which grows parallel to the ground and produces a
clone of its parent a short distance away. This mechanism
allows emergent plant populations to change their
distribution in response to changes in the wetland’s
hydrological regime. Emergent macrophytes such as sedges
and rushes are able to respond to long term changes in
water levels with recruitment of new individuals taking
place either further upslope or downslope in response to
higher or lower water levels. Rapid changes in wetland
water levels can result from management practices such as
the discharge of stormwater into a wetland or the
installation of drains which lower wetland water levels.
This can result in stress and in some cases death of wetland
plants due to either a lack of water when water levels have
dropped, or a lack of oxygen as a result of prolonged
Common wetland tree species such as Melaleuca
(Modong) and Eucalyptus rudis (Flooded gum) reproduce
by the production and dispersion of seed. As a
consequence, they are unable to respond to rapid changes in
water levels. They can however tolerate several years of
continuous inundation before tree death occurs. Extended
periods of low water levels (for example as a result of
drought) is also likely to lead to mortality.
Water and Rivers Commission WN3 January 2000
Common wetland plant species - Eucalyptus rudis (Flooded
gum) and Melaleuca rhaphiophylla (Swamp paperbark).
As primary producers
wetland plants have a vital role in
significant functions including:
• maintaining water quality by filtering out nutrients and
• providing food, shelter and breeding habitat for both
aquatic and terrestrial fauna;
• preventing erosion; and
• contributing to the organic “tea” colour in wetlands and
the shading of riparian zones which can reduce the
frequency and severity of algal blooms.
Wetland areas are also valued for their landscape amenity, a
large part of which is a consequence of the specialised and
diverse plant species that are found in them.
Seasonal wetlands often have a higher diversity of aquatic
and fringing vegetation in comparison to permanent
wetlands. This is because there is a greater number of
microhabitats in seasonal wetlands. This in turn increases
macroinvertebrate species richness and provides food and
shelter for waterbird populations. Seasonally waterlogged
areas such as palusplains and damplands have been found
to support very high levels of plant species richness. For
example, the Brixton Street palusplain in Kenwick supports
517 plant species in an area of 30 hectares.
Threats to wetland vegetation
Weed invasion is a major problem in wetlands resulting in
increased competition for resources such as water, light,
nutrients and space. Weed distribution is closely linked to
increased levels of disturbance in wetlands from activities
which include clearing, grazing, altered fire regimes and
the spread of dieback.
In rural and semi rural areas grazing of wetland plants by
livestock and pest species such as rabbits can have a
serious impact upon wetland plant species diversity,
distribution and health. Stock grazing can also result in soil
compaction, increased nutrient levels, the introduction of
weed species, trampling of native wetland plants and the
ringbarking of mature trees. Introduced pests, such as
rabbits, can have a very destructive impact upon annual
species and young seedlings.
Wetland plants can be threatened by changes in both
surface water and groundwater levels as a result of human
activities. Wetland plants are sensitive to changes in
hydrology which result in a wetland having too much or
too little water. Abstraction of groundwater, for public or
private use, or the construction of drains can lower the
water table locally and significantly affect wetland
hydrology and ecology. Wetland plants are dependent upon
access to either surface water or groundwater and a decline
in the watertable can result in plant deaths and changes in
species composition and distribution.
Elevated wetland water levels can also pose a significant
threat to wetland vegetation. Increased wetland water levels
are closely linked to clearing within wetland catchments
which leads to elevated groundwater levels and increased
surface runoff as a result of reduced evapotransiration and
increased recharge. Wetlands are also commonly used for
the disposal of stormwater which can significantly alter
water regimes and adversely impact upon water quality.
One species of emergent macrophyte that is causing
problems in wetlands on the Swan Coastal Plain is the
introduced bulrush Typha orientalis. Its distribution and
abundance has increased substantially in several coastal
plain wetlands as a consequence of changes in hydrology,
nutrient enrichment and disturbance.
Protecting wetland vegetation
Fencing is an important management tool used to prevent
livestock and pest grazing, reduce trampling of wetland
vegetation and to limit human activities to appropriate
areas. Both the wetland and its dryland buffer should be
fenced to adequately protect the wetland system. There are
many different fencing options and it is important to
identify the specific management requirements so that the
location and design of fencing and gates, is appropriate and
Plants convert carbon dioxide and water into sugars and other complex
produced forms the basis of wetland food webs.
communities in wetlands. The appropriate method of weed
control or removal will depend on the type of weed
problem. Examples of some methods used to control
terrestrial weed species are:
• manual removal by either hand weeding, using a knife or
trowel, crown cut or digging out the entire plant;
• mulching in disturbed areas;
• herbicide spraying or wiping (care must be taken to avoid
herbicide drift and not to use chemicals which may leach
into the wetland); and
• stem injection with herbicide or the painting of herbicide
on the freshly cut stump to control weed trees or large
control. This means:
• garden rubbish and clippings should never be disposed of
• not planting invasive exotic species in parkland next to
• removing problem plants immediately, to prevent them
from spreading and taking hold;
• clearing weeds around seedlings for the first two years to
dramatically improve growth and survival rates;
• maintaining overstorey native trees that will help to shade
out many weeds;
• taking care when spraying for weeds on adjacent land to
avoid spray drift into wetland areas; and
• fire management is necessary to prevent the loss of fire
sensitive and fire dependent native plant species and to
avoid increased weed invasion.
In conjunction with weed control it is important to
rehabilitate native wetland vegetation to prevent further
weed invasion, protect wetland water quality and provide
habitat for native flora and fauna.
Water note WN1, Wetlands and weeds
Water note WN2, Wetlands and fire
Water note WN4, Wetland buffers
Water note WN5, Wetlands as waterbirds habitat
Available from other sources
Australian Association for Environmental Education (WA)
(1994) Forum Proceedings. Weeding Western Australia;
A forum for Land Managers.
Balla, S. (1994) Wetlands of the Swan Coastal Plain,
Volume 1. Their nature and management. Water Authority
of Western Australia and the Department of Environmental
Brouwer, D. (1995) Managing your wetlands on farms.
Buchanan, R.A. (1991) Bush Regeneration: Recovering
Chambers, J.M. Fletcher, N.L. and McComb, A.J. (1995)
Froend, R.H. Farrell, R.C.C. Wilkins, C.F. Wilson, C.C. and
McComb, A.J. (1993) Wetlands of the Swan Coastal Plain,
Hussey, B.M.J. Keighery, GJ. Cousens, RD. Dodd, J.
Lloyd, SG. (1997) Western Weeds: A guide to the weeds of
Western Australia. Plant Protection Society of Western
Hussey, B.M.J. and Wallace, K.J. (1993) Managing your
bushland. Department of Conservation and Land
Management, Perth, Western Australia.
Powell, R. (1990) Leaf and Branch - Tree and tall shrubs of
Perth. Department of Conservation and Land Management,
Perth Western Australia.
Schetlma, M. and Harris, J. (eds.) (1995) Managing Perth’s
Bushlands: Perth’s bushlands and how to manage them.
Greening Western Australia. Perth, Western Australia.
Storey, AW. Vervest, RM. Pearson, GB. and Halse, SA.
(1993) Wetlands of the Swan Coastal Plain, Volume 7.
Water Authority of Western Australia and Environmental
Protection Authority, Australia.
A permanent wetland showing healthy emergent vegetation.
Level 2, Hyatt Centre
3 Plain Street
East Perth Western Australia 6004
Telephone: (08) 9278 0300
Facsimile: (08) 9278 0301
or your regional office
This water note is produced as part of the Waterways WA Program. Managing and enhancing our waterways for the future.
Text by Mike Allen. Water note project coordination by Jodie Oates and Heidi Oswald.
Printed on recycled paper January 2000
This Water Note is intended to be a general guide only and is not a comprehensive document.
For further information on any particular issue please contact the Restoration & Management Section at the Water and Rivers Commission.