F J Obbens
& L W Sage
1 C/o Western Australian Herbarium, Department of Conservation and Land Management
Locked Bag 104, Bentley Delivery Centre WA 6983
2 Swan Coastal District, Department of Conservation and Land Management,
5 Dundebar Road, Wanneroo WA 6065
In the Western Australian wheatbelt, small intact remnants of bushland can contribute
significantly to overall biodiversity. Our comprehensive vascular flora survey of Nature Reserve
A21064, a reserve of 110 hectares near the town of Arthur River, has highlighted this aspect.
Comprehensive surveys of selective wheatbelt reserves provide benchmarks to help us better
understand the flora and vegetation in this highly cleared and fragmented agricultural landscape.
In the diverse flora of this relatively undisturbed upland remnant ten distinct plant communities
encompassing heaths, herbfields, mallee and woodlands can be recognised. The survey identified
323 vascular plant taxa including one rare species, seven priority species and a number of taxa of
special interest recorded from 51 families. Weeds accounted for 22 species (6.8% of total flora),
however, the extent of invasion is relatively low.
Vegetation and flora survey, upland remnant, biodiversity, wheatbelt woodlands
Journal of the Royal Society of Western Australia, 87:19–28, 2004
Nature Reserve A21064 is an upland bush remnant of
high conservation value (i.e. “A” class nature reserve)
with a diverse flora (see species list in Appendix 1). It is
approximately 110 ha in area and is located about 190 km
directly south-east of Perth near the town of Arthur
River, Western Australia (Fig 1). The district has a dry
Mediterranean type climate with very warm, dry
summers and cool, wet winters. Average annual rainfall
for the reserve is about 470 mm, which is typical of the
wetter western (inner) margins of the wheatbelt.
The reserve is situated at the end of an eroded and
generally flattened ridgeline and its upper slopes; the
ridge is the watershed between Mailling Gully to the
south and a smaller unnamed tributary to the north.
These streams eventually drain into the Arthur River
about 7 km west of the reserve. The Arthur River and
adjacent Norcott Plains also run north of the reserve,
about 3 km away. The reserve is a small L-shaped
remnant with the longest east-west boundary (1.9 km)
roughly parallel to the ridgeline/plateau. The north-
south arm of the L measures approximately 1.2 km (Fig
2). Slopes descend gently off the ridgeline and the
predominant aspect is north or north-west. A pattern of
low undulating hills/ridges with interspersed small
valleys and/or plains is typical locally and is a familiar
topography for much of this inner wheatbelt region.
Granite outcrops and/or lateritic breakaways are often
found on the upper slopes or hilltops. Historically, many
upland areas were not cleared for cropping because of
the rougher topography. Also upland areas were
generally abundant in the poisonous Gastrolobium species
that killed domestic stock. Alternatively, some were left
as ‘shade and shelter belts’. Today, very few of these
upland remnants have survived completely intact.
Significant numbers have had a reduction in tree cover
due to past logging (e.g. for timber and fence posts),
insect pests, disease etc, and this has occurred in a
© Royal Society of Western Australia 2004
. Location of A21064 Nature Reserve, near Arthur River,
in the south-west of Western Australia; also shown are 100 mm
Journal of the Royal Society of Western Australia, 87(1), March 2004
relatively short time frame (Landsberg et al. 1990). The
majority of these remnants are also depauperate in
understorey taxa due to selective clearing (e.g. of ‘poison
plants’), frequent grazing by domestic stock, changed
burning regimes, nutrient enrichment, weed invasion,
and other human influenced disturbances (Hobbs &
Atkins 1988; Hobbs 1993; Panetta & Hopkins 1991; Pigott
1994; Yates & Hobbs 1997; Yates et al. 1999; Yates et al.
The wheatbelt region as a whole has been altered from
cleared agricultural land with fragmented small
bushland remnants (Hobbs 1998; Scanlan et al. 1992).
A21064, which is surrounded by agricultural land, is no
different. Beard (1980a) mapped the pre-existing
vegetation cover of this entire region using aerial
photography in conjunction with a wide-ranging
examination of the remaining bushland remnants and
their preferred habitat requirements (i.e. soil, slope,
aspect, evelation etc). These vegetation maps show the
reserve’s wider surrounding district as predominantly
York gum (Eucalyptus loxophleba) and wandoo (E. wandoo)
woodland, while several local upland areas (including
A21064) are mapped as wandoo and mallet (Eucalyptus
representation, although these upland areas also contain
significant patches of sheoak (Allocasuarina huegeliana).
Approximately 20-25 km west of the reserve, wandoo
woodland predominates, but marri (Corymbia calophylla)
and jarrah (Eucalyptus marginata) become more common
about another 20 km further westwards within Hillman
and Godfrey State Forest Blocks (Smith 1974). Powder
bark wandoo (E. accedens) is more abundant amongst the
York gums around the Narrogin area, about 35 km north
of the reserve (Beard 1980b). Salmon gum (E.
salmonophloia) tends to replace wandoo further east (25-35
km), while the Beaufort River area, about 30 km south of
the reserve, has a mix of wandoo, yate (E. occidentalis),
teatree (Melaleuca sp.), Casuarina obesa and samphire flats
(Beard 1980a). Overall, the district was once dominated
by open woodlands; however, patches of heath (often
Flora surveys of wheatbelt remnants are sparse
(Obbens et al. 2001). Although not intensive, Muir’s
(1977a) pioneering surveys of 24 wheatbelt reserves are a
notable exception. There are very few flora surveys of
remnants from around this district, reflecting the high
costs of surveying remnants within this vast wheatbelt
region (i.e. 18 million hectares). The soon to be released
Salinity Action Plan (SAP) surveys will change this
situation. While larger remnants (i.e. >2000 ha) are
certainly important for conserving biodiversity and
helping to maintain many of the ecological processes of
this region, this paper aims to highlight the important
contribution of smaller remnants to regional biodiversity,
particularly if they remain intact. A further aim is to
present more botanical survey data for this significant
The vegetation communities of Nature Reserve
A21064 were interpreted from a 1996 aerial photograph
and confirmed in the field during 1999 and 2002.
Classification of these vegetation communities is based
on Muir (1977b). This classification assesses vegetation
structure by taking measures of lifeform/height class and
canopy cover/density class to produce a vegetation type.
For example, trees 15-30 m with a 10-30% canopy cover
were designated woodlands, while the same trees with a
canopy cover of 2-10% would be designated as open
woodlands. To a significant extent this classification also
reflects the species compositional differences.
Additionally, brief investigations were made of the soils
in each vegetation community. The soil surface was
inspected and then shallow holes (3-5 cm depth) were
made to assess soil texture and colour.
The flora survey and collections were accomplished
by walking along 13 transects (10 spaced at 150 m apart
and 3 spaced at 100 m apart) that spanned the full width
of the reserve in a north-south orientation. The first
transect proceeded in a southerly direction from Noble
Road and approximately 50 m in from the reserve’s
north-east corner. Subsequent transects crossed every
vegetation type several times using this technique. This
transect survey was undertaken during mid/late spring
(i.e. October and November 1998). An additional 8
surveys were also carried out between the summer of
1998 and the spring of 2002. On these occasions a
‘randomized stratified walk’ technique (Hopper et al.
1997) was used. This method involves specimen
collections via random walks in each vegetation
community. The purpose of this intensive surveying was
to obtain a voucher specimen of each taxa and to compile
a more complete vascular flora list.
All specimens were submitted for incorporation at the
WA Herbarium. The species names follow the currently
accepted botanical binomials of WACENSUS (WA
Herbarium census of Western Australian vascular
plants), while conservation status of species is according
to the Department of Conservation and Land
Management’s (CALM) Declared Rare Flora and Priority
Flora list (Atkins 2001). The authors also received
invaluable information from WA Herbarium database
records (WAHERB and FLORABASE). The term “total
‘Liliaceae’” refers to the number of closely related, but
different new families that have been split from Liliaceae
in recent years. For A21064 this includes the families
Anthericaceae, Boryaceae and Phormiaceae.
Vegetation and habitat.
Interpretation of the aerial photograph and site survey
indicated ten major vegetation communities (Fig 2),
including four variants (all explained below). However,
there is considerable variability within some
communities and at differing locations throughout the
reserve. Additionally, there was a range of community
boundaries, some very distinct (e.g. between pure mallet
stands and wandoo woodland or when pure
Allocasuarina huegeliana stands surround granite-exposed
herbfield areas). However, diffuse boundaries have been
drawn at roughly midpoint where any two communities
overlapped (e.g. as demonstrated when Low Woodland
and Low Forest communities merge).
Open Woodland. Dominated by Eucalyptus wandoo with
a generally very open, but variable understorey. This
includes areas of almost pure Gastrolobium trilobum or
numerous orchids/annuals/grasses and smaller shrubs.
Many trees are large to 25 m high with a canopy density
about 5 – 15% (i.e. very sparse to sparse). Soils are either
grey coarse sandy loams or, at the reserve’s western end,
brown coarse loams with some lateritic gravels. This
community represents the top end of shallow drainage
lines that form defined creeks further down slope outside
the reserve boundaries.
Open Woodland. A variant of above, again, dominated
by Eucalyptus wandoo of generally smaller stature and with
a denser canopy cover, about 10 – 25% (i.e. sparse). Lying
entirely on lateritic ridge country, it demarcates itself from
community 1 along the line of a small breakaway. A
sparse to mid dense understorey of predominately
Dryandra species occur on exposed lateritic boulders with
residual soils on the top edge of the breakaway and up
slope at the ridgeline. Elsewhere is fairly open with
various scattered shrubs and some annuals on soils of red-
brown clay loam with numerous gravels.
Low Woodland. A mixed woodland with a mid dense
canopy cover (i.e. about 30 – 70%) consisting of almost
equal proportions of Eucalyptus wandoo (up to 20 m high)
and Allocasuarina huegeliana on grey-brown sandy loams
sometimes with varying amounts of gravel. Understorey
is variable including open areas of low shrubs, annuals
and some grasses to mid dense areas of Acacia or
Low Woodland. A mixed woodland variant of above
with mid dense canopy consisting of Eucalyptus wandoo
(up to 20 m high) and interspersed individuals or patches
of Eucalyptus astringens subsp astringens (Brown Mallet)
and occasionally with scattered Allocasuarina huegeliana.
Again, a variable understorey ranging mostly open to
mid dense in parts. Soils are red-brown coarse clay loams
with gravels and sometimes there is exposed lateritic
Low Forest. Predominantly pure stands of Allocasuarina
and generally mid dense to dense canopy cover (i.e. >
70%). Soils are grey-brown to red-brown sandy or clayey
sand loams sometimes with a little gravel. The
understorey canopy cover is open to mid dense,
including numerous annuals and commonly a tall
where granite is close to the surface and often
outcropping or boulder stacks are nearby.
Woodland. Composed of pure stands of tall (i.e. 25 – 30
m) Eucalyptus longicornis with a very sparse understorey
of Acacia erinacea, Acacia lasiocarpa var. sedifolia, a few
sedges and annuals found on red-brown clay loams.
These areas appear to be associated with shallow
Heath. A heath of mid dense to dense canopy cover
containing a diverse mix of shrubs about 1 – 2 m high on
grey-brown sandy clay loams with some gravel content.
The families Myrtaceae, Proteaceae, Goodeniaceae,
Papilionaceae and Stylidiaceae are well represented along
with many others. This community occurs on the gentle
mid slope areas of the reserve and never appears on the
Heath. A variant of the above comprising a diverse
mix of shrubs (about 1 – 2 m) with interspersed emergent
shrubs (to about 3.5 m) namely Dryandra sessilis and
localised sheet of white sand, which probably overlays
lateritic and/or granitic profiles seen adjacent to this
community. Eremaea pauciflora dominates although many
other species are present.
Low Heath. A very diverse mix of small to mid sized
shrubs (about 0.25 – 1.5 m) with a mid dense canopy
cover found on white-grey clayey loams with occasional
gravel content. This soil profile is possibly exposed and
eroding kaolin, and occurs extensively on lower parts of
the flattened ridgeline. This community contains the
same families as outlined for community 5; however, it
also has a marginally greater diversity of taxa than the
. Map of vegetation communities of A21064 Nature Reserve that include 1 and 1a Open Woodland, 2 and 2a Low Woodland, 3
Low Forest, 4 Woodland, 5 and 5a Heath, 6 Low Heath, 7 Thicket (Tall Heath), 8 Herbfield, 9 and 9a Mallet Woodland, 10 Mallee
Woodland and G Rehabilitated gravel pits. Communities are described below.
Obbens & Sage: Vegetation and flora of an upland remnant, Western Australian wheatbelt
Thicket (Tall Heath). Comprising a dense mix of taller
shrubs (about 1.5 – 3.0 m) dominated by Dryandra,
particularly D. armata and D. nobilis, but including some
other tall Proteaceae species (e.g. Adenanthos cygnorum
and Hakea trifurcata) and occasionally interspersed
mallees. These thickets are located on the flattened
ridgeline. The soils are red-brown to grey-brown coarse
clayey loams or sandy loams with abundant lateritic
gravels, rocks and some exposed hardcap.
Herbfield. Exposed or near-surface granite sheets with
some residual surface soil or soil pockets frequently
covered by Borya sphaerocephala, mosses and lichens, but
including numerous annual herbs and some sedges.
Generally abutting or surrounded by Allocasuarina
Mallet Woodland. Dense pure stands of Eucalyptus
almost absent understorey except for a few resilient
shrubs and abundant bark litter. Soils are red-brown to
brown coarse clay loams with numerous gravels. All
occurrences in the reserve are on the ridgeline including
one area adjacent to and on a lateritic breakaway slope.
Mallet Woodland. This community, a variant of the
above, comprises more open and generally taller (about
15 to 25 m) stands of Eucalyptus astringens subsp
ranging from open to mid dense. The open to mid dense
understorey includes Acacia celastrifolia, A. pulchella,
Nemcia obovata, Dryandra nobilis and many others. Soils
are red-brown to grey-brown clayey loams containing
numerous gravels with rocks/hardcap regularly
occurring within this ridgeline community.
Mallee Woodland. Consisting of various mallee
species, but occasionally pure stands to 4 m high and
sometimes with other tree species interspersed or with
tall shrubs. In the western end of the reserve these
mallees tend to be Eucalyptus aspersa, E. falcata, E. latens
and E. thamnoides subsp megista while in other areas
mainly E. incrassata and E. pluricaulis subsp pluricaulis.
This community is located either on the ridge or the
adjacent upper slope areas where the soils are red-brown
loams with gravels. .
Rehabilitated gravel pits. Old gravel extraction sites
that have been deep ripped and allowed to regenerate
naturally. At this stage, the flora comprises mainly
pioneer species and limited occurrences of several weed
A total of 323 vascular plant taxa (including 22 weed
species) from 51 families was listed for Nature Reserve
A21064 with dicots and shrub species being the
predominant taxa for the reserve (Table 1).
The most represented families were Myrtaceae (39),
Proteaceae (29), Papilionaceae (26), Orchidaceae (26),
Poaceae (20), total ‘Liliaceae’ (20), Asteraceae (17),
Stylidaceae (17), Cyperaceae (16), and Goodeniaceae (12).
Nine Poaceae and three Asteraceae species recorded are
The genera with the greatest number of species were
One declared rare species (Conostylis drummondii) and
seven priority species (Dryandra rufistylis, Eucalyptus
aspersa, E. latens, Leucopogon florulentus, L sp
Dongolocking, Microcorys lenticularis and Thysanotus
The vegetation of the reserve is not unique because
similar vegetation types or variants thereof can be found
in other upland remnants in this region. Overall the
vegetation of the reserve is relatively pristine and
contains a wide representation of upland communities
for its small size. This alone makes it quite special in
Plant type and lifeform for all taxa collected at A21064.
terms of value as public conservation estate. These
woodlands can be moderately diverse due to the
abundant annuals present, but more frequently it is the
open heaths and patches of other communities within
these woodlands that account for the greater proportion
of species diversity, particularly perennial species (Yates
et al. 1999). Table 1 also reaffirms this with 131 perennial
shrub taxa listed, the next highest being perennial herbs
at 127 taxa, but with significantly less vegetative cover
overall than the shrubs produce.