Wetland vegetation a plant community is a characteristic

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Wetland vegetation

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

Typha orientalis (Bulrush).

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

rhaphiophylla (Swamp paperbark), Melaleuca preissiana

(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).

Eucalyptus rudis

Melaleuca rhaphiophylla

Wetland vegetation functions

As primary producers



wetland plants have a vital role in

wetland ecology. Wetland plants perform a number of other

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

carbon compounds by means of photosynthesis. This organic matter

produced forms the basis of wetland food webs.

Lexia dampland, a seasonal waterlogged wetland.  

S. Stratico

Control of weed species is essential to maintain native plant

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


Preventative management is the best method of weed

control. This means:

• garden rubbish and clippings should never be disposed of

in wetlands;

• 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. 

Further reading

Available from Water and Rivers Commission

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

Protection, Australia.

Brouwer, D. (1995) Managing your wetlands on farms.


Buchanan, R.A. (1991) Bush Regeneration: Recovering

Australian landscapes. TAFE, Sydney, Australia.

Chambers, J.M. Fletcher, N.L. and McComb, A.J. (1995) 

A Guide to Emergent Wetland Plants of South Western

Australia. Marine and Freshwater Research Laboratory,

Murdoch University.

Froend, R.H. Farrell, R.C.C. Wilkins, C.F. Wilson, C.C. and

McComb, A.J. (1993) Wetlands of the Swan Coastal Plain,

Volume 4. The Effect of Altered Water Regimes on Wetland


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.

Waterbird usage of wetlands on the Swan Coastal Plain.

Water Authority of Western Australia and Environmental

Protection Authority, Australia.

A permanent wetland showing healthy emergent vegetation.

For more information contact

Level 2, Hyatt Centre

3 Plain Street 

East Perth Western Australia 6004

Telephone: (08) 9278 0300

Facsimile: (08) 9278 0301

or your regional office

Website: http://www.wrc.wa.gov.au

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

ISSN 1442-6900      

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.

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