Eucalypt Woodlands of the Western Australian Wheatbelt
1. The Threatened Species Scientific Committee (the Committee) was established under the EPBC Act and has obligations to present advice to the Minister for the Environment (the Minister) in relation to the listing and conservation of threatened ecological communities, including under sections 189, 194N and 266B of the EPBC Act.
2. The Committee provided its advice on the Eucalypt Woodlands of the Western Australian Wheatbelt ecological community to the Minister as a draft of this conservation advice. In 201x, the Minister the Committee’s advice, adopting this document as the approved conservation advice.
3. The Minister amended the list of threatened ecological communities under section 184 of the EPBC Act to include the Eucalypt Woodlands of the Western Australian Wheatbelt ecological community in the category. It is noted that Western Australia recognises components of this ecological community as threatened.
4. The nomination and a draft conservation advice for this ecological community were made available for expert and public comment for a minimum of 30 business days. The Committee and Minister had regard to all public and expert comment that was relevant to the consideration of the ecological community.
5. This conservation advice has been developed based on the best available information ; this includes scientific literature, advice from consultations, and existing plans, records or management prescriptions for this ecological community.
Salmon gum woodland at Korrelocking Nature Reserve,near Wyalcatchem. Photo credit: Matt White
TABLE OF CONTENTS
1. Description of the ecological community
1.1. Name of the ecological community
1.2. Location and physical environment
1.3. Vegetative components
1.3.1. Canopy layer
1.3.2. Understorey (mid and ground) layers
1.3.3. Corresponding vegetation/mapping units
1.4. Faunal components
1.5. Key diagnostic characteristics and condition thresholds
1.5.1. Key diagnostic characteristics
1.5.2. General notes on the definition of the WA Wheatbelt Woodland
1.5.3. Condition thresholds
1.6. Further information to assist in determining the presence of the ecological community and significant impacts
1.7. Area critical to the survival of the ecological community
1.8. National context and existing protection
1.8.1. Land tenure
1.8.2. Threatened ecological communities recognised in WA
1.8.3. Level of protection in reserves
2. Summary of threats
3. Summary of eligibility for listing against EPBC Act criteria
4. Priority research and conservation actions
4.1. Conservation objectives
4.2. Research priorities
4.3. Priority recovery and threat abatement actions
4.4. Existing plans/management prescriptions
4.5. Recovery plan decision
Appendix A – Lists of known species from the ecological community
Appendix B – Additional information about the ecological community
Appendix C – Description of threats
Appendix D – Detailed assessment of eligibility for listing against the EPBC Act criteria 1. Description of the ecological community
The ecological community assessed in this conservation advice is composed of eucalypt woodlands that formerly were the most common type of vegetation across the wheatbelt landscape of south-western Western Australia (WA). The woodlands are dominated by a complex mosaic of several eucalypt species with a tree or mallet1 form over an understorey that is highly variable in structure and composition. Woodlands dominated by mallee forms or vegetation with a very sparse eucalypt tree canopy are not part of the ecological community.
1.1. Name of the ecological community
This advice follows the assessment of a public nomination to list the ‘Eucalypt Woodlands of the Western Australian Wheatbelt’ as a threatened ecological community under the EPBC Act. The nominated name is appropriate for the national ecological community because it adequately captures the type of vegetation and region covered by this ecological community. ‘Eucalypt woodlands’ distinguishes the ecological community as having an open tree canopy dominated by eucalypt species with a single trunk. They are distinct from woodlands dominated by mallee eucalypts or non-eucalypt tree species, and vegetation in which eucalypt trees may be present as sparse, scattered emergents and do not form a distinct canopy. ‘Wheatbelt’ is a widely recognised and used geographic term for the region between the Darling Range and the goldfields. The national ecological community includes component ecological communities that are recognised as threatened in Western Australia (see section 1.8). The name of the ecological community is hereafter abbreviated to the ‘WA Wheatbelt Woodlands’ or ‘the ecological community’.
1.2. Location and physical environment
The WA Wheatbelt Woodlands ecological community is endemic to south-western WA. It occupies a transitional zone between the wetter forests associated with the Darling Range and the southwest coast, and the low woodlands, mallee and shrublands of the semi-arid to arid interior. The vegetation that occurs east of the agricultural clearing line, primarily in the Coolgardie and Eastern Mallee bioregions, is generally known as the Great Western Woodlands. The Great Western Woodlands generally are not part of the WA Wheatbelt Woodlands ecological community except the westernmost extent that overlaps into the bioregional boundaries outlined in the next paragraph. The ecological community generally lies within the Transitional Rainfall Biological Province of southwest Australia (Hopper and Gioia, 2004).
The wheatbelt region where the ecological community occurs encompasses three IBRA2 subregions:
Avon Wheatbelt subregion AVW01 Merredin;
Avon Wheatbelt subregion AVW02 Katanning; and
Mallee subregion MAL02 Western Mallee.
Most of the WA Wheatbelt Woodland ecological community lies in these bioregions.
Some outlying patches of the ecological community may extend into adjacent areas south and east of the primary wheatbelt bioregions, in the easternmost parts of the Jarrah Forest bioregion. They generally occur south of Northam, extending around the vicinity of localities such as Wandering, Williams, Kojonup and Mount Barker These outlier patches are limited to areas that are not on the Darling range, receive less than 600 mm mean annual rainfall and overlie the Yilgarn Craton geology. As these outliers occur under similar patterns of rainfall, landscape and degree of clearing/threats to the main wheatbelt subregions, they are therefore included as part of the ecological community.
The landscape of the WA wheatbelt and their associated bioregions has been described by Bamford (1995), WA CALM (2002) and McQuoid (2014). Figure 1 (from Bamford, 1995) summarises the relationships between vegetation structure, soils and topography across the wheatbelt.
Figure 1. Diagrammatic relationship between vegetation, topography and soil type in the western and eastern wheatbelt, showing landscape position for the key eucalypt woodlands.
Source: Bamford (1995). Reproduced with permission of the author.
The wheatbelt as defined here occurs entirely within the Yilgarn Craton, a very ancient and extensive geological formation that dominates south-western Australia east of Perth and Geraldton and roughly north from the Stirling Ranges. The landscape is generally of flat to undulating relief that is occasionally broken by granite or other rock outcrops and higher elevation sites, and chains of saline wetlands and salt lakes. The ecological community is generally associated with the flatter, undulating relief, including drainage lines and saline areas.
In the eastern and southern wheatbelt, the drainage is ancient and disconnected or occluded, comprising salt lake systems that only function during very wet seasons WA CALM (2002). Further west, the drainage patterns are rejuvenated and include stream channels that flow in most years. Much of the ecological communuity lies within the Avon River Basin (Basin no. 615) that covers the central and eastern wheatbelt but also extends into the Goldfields region. Other river basins that overlap into the wheatbelt include the Moore-Hill Rivers (Basin no. 617) and Yarra Yarra Lakes (Basin no. 618) in the northern wheatbelt; the Blackwood River (Basin no. 609) and Murray River (WA) (Basin no. 614) in the western wheatbelt; and the Albany Coast (Basin no. 602) and Frankland River (Basin no. 605) in the southern wheatbelt.
The climate of the wheatbelt region varies from warm Mediterranean to semi-arid (WA CALM, 2002). BoM (2012)classifies the region to be within the ‘Grassland’ and ‘Temperate’ Köppen 3 climate classes, which are characterised by summers that are warm to hot, and dry. Seasonal rainfall shows a Winter to Winter Dominant pattern. Annual rainfall isohyets show a gradient of increasing aridity from south-west to north-east – i.e. with increasing distance inland from the coast and ranges. The wheatbelt region varies from about 600 mm/year rainfall closer to the coast to about 250 mm/year at its eastern edge. Climate data for five localities across the extent of the ecological community are summarised in Figure 2 (monthly rainfall) and Table 1 (temperatures).
Table 1. Mean maximum and minimum temperatures and annual rainfall for five localities across the WA wheatbelt. Based on data collected during the period 1981 to 2010.
Mean summer maximum temperature
(monthly range oC)
Mean winter minimum temperature
(monthly range oC)
Mean annual rainfall (mm)
34.5 – 36.8
6.6 – 7.9
32.0 – 34.4
5.2 – 6.1
31.7 – 33.9
5.5 – 6.7
27.3 – 29.5
5.8 - 6.4
29.1 – 30.7
4.0 – 5.0
Source: BoM (2014).
Figure 2. Monthly rainfall (mm) for five localities across the WA wheatbelt. Data are means for the period 1981 to 2010. Morawa, Northam and Merredin are in the Avon Wheatbelt bioregion, Kojonup is in the eastern Jarrah Forests bioregion and Newdegate is in the Western Mallee subregion. A pattern of winter dominant rainfall is consistent for all localities.
Source: BoM (2014).
The wheatbelt region is now dominated by agricultural land uses, principally cereal cropping or grazing, and is extensively cleared of native vegetation.
1.3. Vegetative components
The WA Wheatbelt Woodlands ecological community is a woodland in which the trees typically are spaced and the canopy is relatively open. The understorey is highly variable in structure and composition, and there are no consistent patterns that correlate with what tree canopy species may be present. There can be localised variation in vegetation structure as a consequence of disturbance, for instance fire, or change in site characteristics that allows for gaps in tree canopy cover, a higher density of trees e.g. dense sapling regrowth, or change in the naure of the understorey. While many responses to disturbance may be temporary, some may persist for years before the typical woodland structure re-establishes. For instance, recovery from severe fires involving fire-senstive eucalypts, such as gimlet or salmon gums that are killed by fire, requires many years, as disturbed woodlands need to pass through a cycle of seedling germination, sapling establishment and thinning, and tree maturity.
1.3.1. Canopy layer
The WA Wheatbelt Woodlands ecological community has a tree canopy dominated by eucalypt species. French (2012) identified 158 species and subspecies of Eucalyptus that are present in the wheatbelt region4, of which about 50 species are entirely or mostly restricted to the wheatbelt. Eucalypts occur as a complex mosaic of species across the wheatbelt region, with the mix of species present at a particular site depending on inter-relationships among climate, soils, landform and hydrology.
However, not all wheatbelt eucalypt species are characteristic of the ecological community. Some are excluded from the ecological community for one or more reasons, as follows:
taxa with a mallee growth form;
taxa limited to landscapes that are not part of the ecological community, for instance granite outcrops and rocky rises; or
taxa that have their main distribution outside the wheatbelt, so that occurrences in the wheatbelt represent only a minor part of their natural distribution. Notable examples include: Eucalyptus camaldulensis subsp. arida (river red gum) that extends into the northern wheatbelt but its distribution mostly occurs much further north; E. transcontinentalis (redwood) is more widespread in the Goldfields region but extends into the eastern wheatbelt; and E. marginata (jarrah) predominantly occurs on the Darling Range but can extend downslope into wheatbelt sites.
The species that dominate or co-dominate1 the WA Wheatbelt Woodlands ecological community are based on the floristic classification of wheatbelt woodlands by Harvey and Keighery (2012) and are identified in Table 2a. These species have a tree or mallet habit and many are considered iconic within the wheatbelt landscape; for instance, species such as Eucalyptus salmonophloia (salmon gum), E. loxophleba subsp. loxophleba (York gum), E. salubris (gimlet), E. wandoo (wandoo) and the mallet group of species. One species not recognised as a distinct community by Harvey and Keighery (2012) was added to Table 2a: E. mimica (Newdegate mallet; hooded mallet). There are two subspecies of E. mimica, both of which are limited to the western Mallee subregion and have a restricted distribution (French, 2012). The subspecies have priority 1 and 3 conservation status as poorly known taxa in WA. Their omission from Harvey and Keighery’s report is likely due to sampling artefacts arising from its restricted distribution.
The distributions of many species in Table 2a are not restricted to the wheatbelt region but extend into adjacent bioregions. Where this occurs, they may be associated with other canopy and/or understorey species that are not typical of the wheatbelt and serve to distinguish the WA Wheatbelt Woodland from other vegetation types.
Many other eucalypt species may be present in association with the key species, depending on location and local site influences, but do not occur as dominant or co-dominant species in the WA Wheatbelt Woodlands ecological community (Table 2b). In some instances, these associated species may occur as a lower subcanopy, particularly in the case of mallees. Amallee subcanopy may comprise one or more species, with those most likely to be present noted in Table 2b. Where the associated species occur individually or collectively as the dominant or co-dominant species, then this represents a different vegetation type to the WA Wheatbelt Woodlands ecological community. For instance a dominant cover of mallee species is properly regarded as a mallee woodland.
Non-eucalypt species may extend into the tree canopy at some sites, for instance where eucalypt woodland intergrades with acacia or sheoak woodlands or shrublands. Non-eucalypt species that may be present in a tree canopy include: Acacia acuminata (jam) [which commonly co-occurs in a canopy with York gum], Allocasuarina huegeliana (rock sheoak) [which may co-occur in a canopy with York gum or wandoo], Callitris columellaris (white cypress pine), Casuarina obesa (swamp sheoak) and some of the larger Melaleuca species e.g. M. rhaphiophylla (swamp paperbark). Where these species become sufficiently abundant and tall to form a distinct and dominant tree canopy, then this represents a shift in vegetation type away from eucalypt woodlands to other, non-eucalypt woodlands or tall shrublands.
Table 2. Tree canopy species of the WA Wheatbelt Woodlands ecological community. Within a given patch of the ecological community, one or more of these species are dominant or co-dominant. Note that some taxa may occur both as a tree or mallee form (see notes below Table 2b).
2a) Key eucalypt species. One or more of these species are dominant or co-dominant within a given patch of the ecological community.
powder-bark; powder-bark wandoo
Eucalyptus astringens subsp. astringens
Eucalyptus densa subsp. densa
narrow-leaved blue mallet
Eucalyptus gardneri subsp. gardneri
Eucalyptus loxophleba subsp. loxophleba
Eucalyptus mimica subsp. continens
Eucalyptus mimica subsp. mimica
small-fruited gum; blackbutt
ornamental silver mallet; ornate mallet
Mt Yule silver mallet; Cadoux mallet
Eucalyptus rudis subsp. rudis
salt gum; salt salmon gum
Eucalyptus sargentii subsp. sargentii
salt river gum
Eucalyptus spathulata subsp. spathulata
Eucalyptus spathulata subsp. salina
Salt River mallet
Eucalyptus wandoo subsp. pulverea
Eucalyptus wandoo subsp. wandoo
2b)Associated canopy species that may be present within the ecological community but are not dominant or co-dominant. The list is not comprehensive and presents the more common taxa encountered.
Sources: Based on woodland floristic community descriptions in Harvey and Keighery (2012) supplemented by accompanying online factsheets (WA DEC, 2007-) and relevant descriptions from the National Vegetation Information System (NVIS). Scientific and common names follow those in French (2012) and WA Herbarium (1998-) and are current to August 2014.
Notes:1 Where tree and mallee forms are recognised as separate subspecies (e.g. York gum), only the ‘tree’ subspecies are included as key species in Table 2a. Where there is no taxonomic distinction between tree and mallee forms, the ecological community is present where the tree form of a key species occurs as a dominant component of the canopy or is co-dominant with other key species.
1.3.2. Understorey (mid and ground) layers
The understorey beneath the woodland tree canopy is highly variable in both structure and composition across the wheatbelt. Fox (2001) undertook comparative surveys of the understoreys beneath wandoo, salmon gum and York gum woodlands across the wheatbelt and into adjacent areas of the arid zone, and noted an extremely high degree of floristic variation below the tree canopy. More than half the plant species noted in her survey were only recorded at single sites and no two understoreys were more than 30% alike. Despite this variation, some general trends were apparent. Wandoo woodlands generally had a higher diversity of shrubs, with greater representation of the plant families Papillionaceae (peas), Proteaceae (hakeas, grevilleas, banksias) and Myrtaceae (tea-trees, bottle-brushes). Salmon and York gum woodlands tend to have more similar understoreys, in which Chenopodiaceae (saltbushes) and Asteraceae (daisies) are more prominent. These differences are partly related to soil differences and also to differences in water use and competitiveness for soil moisture by tree canopy species, which influences development of the understorey.
The subcommunities identified by Harvey and Keighery (2002) are partly based on the variability of understorey structure, in addition to other canopy species that commonly co-occur with the dominant tree species. The main understorey structures are outlined below, noting there is considerable diversity and variation in composition within each broad understorey structural category.
Bare to sparse understorey (e.g. under some mallet woodlands).
Herbaceous understorey (e.g. under some York gum, wandoo or wheatbelt wandoo woodlands).
The understorey comprises a ground layer of forbs and/or graminoids though a few, scattered shrubs may be present. Some sites are floristically diverse and herb-rich.
Scrub or heath understorey (e.g. under some York gum, salmon gum, wandoo woodlands).
The understorey comprises a mixture of shrubs from several genera and species. The shrub layer can vary in height, from dwarf to tall, and in cover from open to dense. The nature of the scrub may be influenced by time since disturbance (e.g. fire or grazing), as well as site factors or proximity of adjacent shrublands from which shrubs may intrude into the woodlands. A ground layer of herbs and grasses is present to variable extent, typically being less developed as shrub cover increases, due to shading.
Chenopod-dominated (e.g. under some red morrel, salmon gum, Kondinin blackbutt woodlands).
The understorey is a subset of the scrub category in which the prominent species present are saltbushes, bluebushes and related taxa. They include members of the genera Atriplex, Enchylaena, Maireana, Rhagodia and Sclerolaena. Other, non-chenopod shrubs and herbaceous species may be interspersed amongst the chenopod plants.
Thickets (e.g. under some red morrel, salmon gum, York gum woodlands).
Some taller shrub species may form thickets beneath the tree canopy. This mainly applies to taller Melaleuca species, several of which may which form a tall, dense shrub layer, often in moist conditions. The species present in thickets include: Melaleuca pauperiflora, M. acuminata, M. uncinata group, M. lanceolata, M. sheathiana,M. adnata, M. cucullataand/or M. lateriflora. Tammar thickets which are characterised by Allocasuarina campestris and Melaleuca hamata or M. scalena also may occur beneath wandoo woodlands. A range of other shrub and ground layer species may occur among or below the thickets.
Saline areas (e.g. under some York gum, Salt River gum, salt salmon gum woodlands)
The understorey flora includes a range of salt tolerant species that dominate the understorey in locations that are more saline. Some patches may have a cover of samphire (Tecticornia spp.). While some areas may be naturally saline, in many cases increased salinity has arisen as a consequence of disturbance and is now a major threat, as noted in Appendix C Threats.
The highly biodiverse nature of the wheatbelt landscape, where the composition of plant species can vary markedly from patch to patch, means it is not possible to prepare a comprehensive list of plant species for the WA Wheatbelt Woodland ecological community. However, a list of the key species based on the subcommunity descriptions of Harvey and Keighery (2012) plus corresponding NVIS descriptions has been collated at Table A1 of Appendix A.
1.3.3. Corresponding vegetation / mapping units
Western Australia has a comprehensive state-wide vegetation classification system, in addition to numerous regional and local surveys across the state. As the relevant vegetation data has been widely used for planning and reporting purposes, appropriate cross-references are presented here, as part of the vegetation description. Two available vegetation classification and survey datasets that include the Western Australian wheatbelt are most pertinent to the WA Wheatbelt Woodlands assessment.
The first is the recent floristic classification of wheatbelt eucalypt woodlands by Harvey and Keighery (2012), supplemented by online information presented by WA DEC (2007 -). Harvey and Keighery identified 29 communities based on the key woodland eucalypt species present in the tree canopy (Table 3), though acknowledged that some woodland patches comprise an assemblage of canopy species where no clear dominant is evident. They further recognised 62 sub-communities based on associated tree species that are present and/or understorey structure. The woodland classification was largely limited to eucalypt species with a single trunk and did not comprehensively cover vegetation dominated by mallee and non-eucalypt woodland species.
Some of the 29 communities identified are excluded from the WA Wheatbelt Woodlands, as shown in Table 3. Two communities represent woodlands that mostly occur outside the wheatbelt: Eucalyptus marginata (Jarrah) Woodland is more extensive on the Darling Range, well within the Jarrah Forests bioregion; and Eucalyptus polita (Parker Range Mallet) Woodland mostly occurs in the western Goldfields, east of the Avon Wheatbelt bioregion (French, 2012). Two other communities, E. moderata (Redwood) Woodland and E. yilgarnensis (Yorrell) Woodland are excluded on the basis that these species are more generally regarded as mallees (DPaW, 1998-). Eucalyptus moderata is often a common component of mallee woodlands (French, 2012; All these eucalypt species occur in the wheatbelt and may even be part of the ecological community where they are not dominant but occur in association with other character eucalypt species that dominate the patch.
Table 3. Woodland floristic communities identified by Harvey and Keighery (2012).
Woodland floristic community
Likely to be part of the WA Wheatbelt Woodland ecological community
Eucalyptus occidentalis (Flat-topped Yate) Woodland
Eucalyptus ornata (Ornate Mallet) Woodland
Eucalyptus recta (Cadoux Mallet) Woodland
Eucalyptus rudis (Flooded Gum) Woodland
Eucalyptus salicola (Salt Salmon Gum) Woodland
Eucalyptus salmonophloia (Salmon Gum) Woodland
Eucalyptus salubris (Gimlet) Woodland
Eucalyptus sargentii (Salt River Gum) Woodland
Eucalyptus singularis (Mallet) Woodland
Eucalyptus spathulata (Swamp Mallet) Woodland
Eucalyptus urna (Merrit) Woodland
Eucalyptus wandoo (Wandoo) Woodland
Not part of the WA Wheatbelt Woodland ecological community 2
Eucalyptus marginata (Jarrah) Woodland
Eucalyptus moderata (Redwood) Woodland
Eucalyptus polita (Mallet) Woodland
Eucalyptus yilgarnensis (Yorrell) Woodland
1 Only stands dominated by subspecies loxophleba are included in the WA Wheatbelt Woodlands ecological community. Unlike most wheatbelt woodland trees, subspecies loxophleba can be multi-stemmed but is still considered a tree, rather than mallee. However, subspecies lissophloia and gratiae are recognised to have a mallee growth form, while subspecies supralaevis is limited to the far northern wheatbelt, extending into adjacent bioregions to the north and east. Stands dominated by the latter three subspecies are not part of the WA Wheatbelt Woodlands ecological community.
2 Excluded from the WA Wheatbelt Woodlands ecological community either because they represent woodland types that are more extensive outside the wheatbelt, or the species more typically occur as a mallee growth form. Their single-stemmed or tree forms are uncommon.
The second dataset is the comprehensive state-wide vegetation classification developed by Beard at the 1:250 000 scale and, more recently, at a broader 1:3 million scale (Beard et al, 2013; DPaW, 2013 – see Appendix B for further detail).
The WA Wheatbelt woodlands ecological community potentially corresponds to 45 Beard vegetation associations. The most likely equivalents are with the 37 asociations that are dominant or unique within the wheatbelt regions. Table 4 lists all these associations, along with their corresponding classification under the National Vegetation Information System (NVIS). Woodland vegetation associations that orignally had a very low representation in the wheatbelt, i.e. less than twenty percent of their total pre-European extent occurred in the wheatbelt, were disregarded. These vegetation associations are considered to represent intrusions of vegetation associations that are more typical of the surrounding bioregions into the wheatbelt.
Twelve eucalypt woodland vegetation associations are considered to be part of the dominant associations of the wheatbelt (Table 4a). Each dominant vegetation association had an extensive pre-European extent of greater than 100 000 hecatres and, collectively, accounted for at least 40% of the original pre-European extent of total native vegetation across the wheatbelt subregions. Most (nine) of the dominant woodland vegetation associations also were unique to the wheatbelt region.
Another 25 woodland vegetation associations are less prevalent but unique to the wheatbelt region. These collectively accounted for only a minor proportion of the original native vegetation, about three percent of the total original extent of native vegetation.
Eight eucalypt woodland vegetation associations occur in the wheatbelt that are neither dominant or unique to the wheatbelt, but also cannot be disregarded as minor intrusions. In some cases, more than 50 percent, (but less than 75 percent) of their total original extent occurred in wheatbelt bregions (Table 4c). Again, these units collectively accounted for only a minor proportion of the total original vegetation across the wheatbelt.
Further information on corresponding vegetation associations is presented in Appendix B.
Table 4. Beard vegetation associations (VA) likely to correspond to the WA Wheatbelt Woodland ecological community. Equivalent NVIS descriptions are shown, based on available level 6 (sub-association) descriptions. The estimated proportion of original extent present in the wheatbelt bioregions also are shown based on 2013 data.
4a) Eucalypt woodland vegetation associations that were formerly dominant1 within the wheatbelt bioregions.
U2 Eucalyptus salubris, Eucalyptus sheathiana \tree, tree mallee\6\i
Source: Data on extent calculated from DPaW (2013).
Notes to Table 4:
1 Definiton of term follows that of DPaW (2014). Dominant refers to VAs that together occupied 85% of the pre-European vegetation extent in the three wheatbelt subregions, determined by rankings of pre-European extent [most to least extensive] for all wheatbelt VAs, based on data from DPaW (2013).
2 Definiton of term is based on that of DPaW (2014), who defined ‘unique’ as individual VAs that had at least 85% of their total pre-European extent in a given subregion. For the purposes of this assessment, the threshold has been modified to include VAs that had 75 % or more of their original extent across the collective wheatbelt subregions. Percentages calculated from data in DPaW (2013). Some vegetation associations may be considered unique if outlier woodlands in the southeastern part of the Jarrah Forests bioregion, adjacent to the Avon Wheatbelt, are taken into account. A revised percentage of original extent that includes outlying remnants is presented in square brackets for these units.
3 Wheatbelt generally refers to the three IBRA subregions AVW01 Merredin, AVW02 Katanning and MAL02 Western Mallee. Outlying patches may occur in the southeastern part of the Jarrah Forests bioregion.
Legend to symbols in NVIS descriptions: ^ identifies the dominant species and growth form in each vegetation layer.
+ identifies the dominant vegetation layer among Upper (U), Middle (M) and Ground (G) layers. These may be divided into taller and lower levels.
\Numbers\ refer to height classes; in the case of trees \7\ refers to a height of 10-30 metres and \6\ to <10 metres.
\Letters\ refer to cover characteristics for each stratum; \i\ refers to foliage cover of 10-30% and \r\ to foliage cover of <10%. Where there is an upper stratum of trees, they correspond to woodland and open woodland structural formation classes, respectively.