Wetland Flora

Photo - Robsley Swamp - Cathy Thrupp

Wetland plants / flora - also known as hydrophytes

A hydrophyte is defined as ‘a plant that grows in water or needs a water-logged environment’ (Shorter Oxford Dictionary). This definition is equivalent to plants described under attribute i of the Queensland Wetlands Program definition: ‘…plants …that are adapted to and dependent on living in wet conditions for at least part of their life cycle…’. Therefore the term hydrophytes is used as a convenient abbreviation for plants described by that attribute.

Wetland plants as a wetland attribute

Hydrophytes have long been used as indicators of wetlands both in Australia (NSW Wetland Management Policy 1996, Paijmans et al., 1985, page 1; PWCNT 2000, quoted by Duguid et al., page 50) and overseas (e.g. Hall and Penfound 1939 and other sources quoted in National Research Council 1995, page 122). This is because of the strong relationship between soil saturation and the development of communities dominated by plants specifically adapted to, and requiring, such conditions. Using plants (or soils) that are adapted to and dependent on wet conditions means that the definition of wetlands includes lands where inundation with water is the dominant factor determining the nature of soil development or the types of plants living in the soil and on its surface (Cowardin et al., 1979).

The prolonged presence of water creates conditions that favour the growth of specially adapted plants (hydrophytes). Hydrophytic adaptations may be morphological (e.g. shallow roots to facilitate survival during times of water logging), reproductive (e.g. seeds need a certain amount of flooding to germinate, can germinate in water or are dispersed by flooding) or physiological (e.g. tolerant to toxins created by anaerobic conditions). Many non-hydrophytes cannot grow where there is even minor water-logging. Hydrophytes adaptations may allow plants to establish and effectively eliminate competition from plants less adapted to wet conditions.

A list of hydrophytes has been assembled to supplement the Queensland Wetland definition and help identify wetlands.

Compilation of a wetland plant indicator list

The indicator list has been assembled mainly by officers of the Queensland Herbarium, of the Department of Environment and Resource Management with reference to publications listed below. Generally, the list is restricted to higher plants and does not comprehensively include lower plants, such as algae and fungi, due to the paucity of knowledge of these latter groups. Plant names follow those listed in the Census of the Queensland Flora (Bostock and Holland, 2007 or subsequent versions of that list).

Photo - Staaten River National Park - GW Wilson

Plant species are included in the list if they are only recorded to naturally occur, achieve maturity and successfully reproduce in areas that experience wet conditions. Wet conditions are defined as areas where the root zone becomes periodically saturated or inundated during the growing season. These are similar criteria to those listed to assess hydrophytes in America (Reed 1988). Such plants are assessed, by association with such environments, to meet the criteria that they are adapted to and dependent on wet conditions for at least part of their life cycle.

Plants growing in artificial or disturbed habitats are not included in this assessment as these situations do not provide the full range of environmental correlates to test dependency on wet conditions throughout a plants lifecycle. For example species on the list may occur in gardens or other disturbed areas that are dry, where competition is artificially eliminated, or establishment aided or when introduced overseas (e.g. M. quinqenervia in Florida (Turner et al., 1997, Serbesoff-King, 2003)). These species are assessed as hydrophytes because they have not been observed to complete their lifecycle outside wet environments under natural conditions.

Species on the list have additional information noted against them including life-form (e.g. tree, shrub, sedge), habitat (e.g. mangrove), if they are exotic and if they are freshwater aquatics i.e. plants that grow only in fresh water or have their perenneating organs submerged in fresh water such as water lilies and plants that are found growing on or in open water.

It is expected that this list will be updated as more information is reviewed or becomes available through application of the definition in field assessment as well as through botanical research. At a species level plants do not have uniform environmental requirements for growth and reproduction (Tiner, 2006) and, individual populations of plants may differ in their adaptation to water logging or flooding (Tiner, 1991). Thus future updates to this list may include sub-sets of species such as species in a particular region that are considered hydrophytes.

Wetland Summary Information

Wetland summary information provides information and links for defined areas (basin, NRM region and local government areas). Information is provided on: wetland summary statistics, flora and fauna, major towns, drainage divisions, bioregions, significant wetlands (for example, those found within Ramsar and Directory of Important Wetlands), relevant management guidelines and more.