3.8 Significance of Vegetation
In this report, the local distribution of a VT is defined as the mapped distribution within the
Study Area, and the regional distribution refers to the total known distribution of the VT in
Western Australia.
The local significance of VTs can be measured by the mapped extent of the VT within the
Study Area, and the type and extent of landforms they are associated with. They may also be
significant in containing a particularly significant flora taxon or taxa that may be uncommon
or restricted (e.g. T-DRF and rare or restricted Priority flora, or a disjunct occurrence of a
particular taxon). Table 6 presents local conservation significance rankings of VTs in the
Study Area, based on these criteria, with ‘Very Low’ indicating the lowest conservation
significance ranking, and ‘Very High’the highest.
Table 6:
Descriptions of Local Conservation Significance Ranking of Vegetation
Types in the Study Area
Conservation
Significance
Ranking
Description
Very Low
The VT is very widespread through the Study Area (occupies >30 % of the
Study Area); and
VT does not represent preferred habitat for Threatened (T) Flora, and such flora
has not been recorded in the VT
Low
The VT is widespread through the Study Area (occupies >10 % of the Study
Area); and
VT does not represent preferred habitat for Threatened (T) Flora, and such flora
taxa have not been recorded in the VT
Moderate
The VT is widespread through the Study Area (occupies >10% of the Study
Area); and
VT does represent preferred habitat for Threatened (T) Flora, and such flora taxa
have been recorded in the VT
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Conservation
Significance
Ranking
Description
High
The VT is moderately restricted in the Study Area (occupies < 10 % of the Study
Area; or
VT is mapped on a relatively restricted landform type (i.e. claypans, areas with
lateritic substrate)
VT may represent preferred habitat for Threatened (T) flora, and such flora have
been recorded in VT
Very High
The VT is corresponds with a State or Commonwealth listed Threatened
Ecological Community or Priority Ecological Community; or
The VT is highly restricted in the Study Area (occupies <1% of the Study Area);
and
The VT is preferred habitat for Threatened (T) Flora species, or flora taxa ranked
as P1 or P2
Determining the regional conservation significance of the VTs is difficult as there is no broad
regional dataset including the Study Area available. The nearest publicly available regional
dataset (as presented by Gibson et al. 1994) does not extend northwards to cover the Study
Area. Likewise, the vegetation of the majority of nearby nature reserves has not been mapped
at a VT level. However, there is limited regional data available through historical work
undertaken by Woodman Environmental (2007b; 2009a), including quadrats placed in nearby
Eneminga Nature Reserve, R 40916, as well as in UCL. There is also some qualitative data
available with regards to the restricted wetlands survey undertaken by Woodman
Environmental (Woodman Environmental 2013c).
The descriptions of VTs mapped within the Study Area are also compared against listed TEC
and PEC descriptions (both listed at State and Federal levels) (DEC 2013b; 2013c; DoE
2013c) to determine the likely presence of these communities within the Study Area. By
definition, any TECs or PECs are considered to be regionally significant.
The quadrat data collected within the Study Area can be considered a sub-regional dataset in
itself. The Study Area covers 34 402 ha, the majority of which (32 452 ha; 94 %) is located
on vegetation system association Bassedean_1030. A total of 30 1306 ha of this area is
uncleared; this represents 37 % of the current extent of this vegetation system association
throughout Western Australia (38 % of the current extent of this vegetation system association
in IBRA subregion SWA02).
A qualitative assessment with regard to the regional conservation significance of VTs of the
Study Area has been undertaken. The assessment has taken into account the known
distribution of these VTs outside of the Study Area, the likelihood of any of the VTs being
listed TECs or PECs, and the extent of these VTs mapped within the Study Area in
combination with the types of landforms on which these VTs have been mapped.
3.9 Vegetation Condition Mapping
Vegetation condition was recorded at all quadrats, and also opportunistically within the Study
Area during the 2012 survey where significant areas of disturbance to vegetation were noted
(e.g. weed infestations). Vegetation condition was described using the vegetation condition
scale for the South West Botanical Province (Keighery 1994), as displayed in Table 5.
Vegetation condition polygon boundaries were developed using this information in
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conjunction with aerial photography interpretation, and were digitised as for vegetation type
mapping polygon boundaries.
3.10 Survey for Conservation Significant and Introduced Flora
As per Table 3, and shown on Figure 6, survey for CS and introduced flora taxa has been
historically undertaken in areas of likely impact by future operations, and more widely
through the Study Area. These studies include survey of exploration drilling lines for CS
flora taxa, (including survey for indivdiuals both on and away from proposed drilling lines)
and searching for CS and introduced flora taxa during more widespread mapping exercises,
including during quadrat/site assessment and travelling between quadrats/sites. Due to the
relatively high intensity of historical surveys throughout the Study Area, the distribution of
both CS and introduced flora taxa are generally well known.
Due to the level of historical survey for CS and introduced flora taxa within the Study Area,
specific targeted searches for these taxa within areas of proposed impact were not undertaken
during the 2012 flora and vegetation survey. However, both CS and introduced taxa were
recorded while conducting the current vegetation survey, including within quadrats and whilst
traversing between quadrats.
Where populations of CS taxa were identified during the current survey a representative
collection of material was made, and the abundance and spatial distribution (using GPS
coordinates) of individuals within each population was recorded. Any occurrences of
introduced flora were treated as for populations of CS flora.
3.11 Significance of Conservation Significant Flora Populations
In this report, the local distribution of a flora taxon is defined as one occurring within the
Study Area, and the regional distribution refers to the known distribution of the taxon in
Western Australia. Locations of plants are considered separate populations if there is a
distance of more than approximately 500 m between locations (Stack 2010).
The significance of a local population of a CS flora taxon to the regional conservation
significance of the taxon depends upon the extent of the regional distribution of the taxon, the
number of known populations of the taxon, and the location of local distribution (i.e. within
the Study Area) within the overall regional distribution of the taxon (i.e. throughout the State).
The significance of the local population/s of CS flora taxa within the Study Area to the
regional conservation significance of the taxon has been determined using Table 7.
Table 7:
Significance of Local Populations to the Overall/Regional Conservation of
Species
Ranking
Description
High
Known range of taxon either entirely located within the study area, or within the
survey area and to a radius of <5km of the study area; or
Taxon known from <5 discrete populations, including within the survey area; and
Study area on boundary of known regional distribution; or
Taxon listed as Threatened
Moderate
Known range of taxon extends <50km; and
Taxon known from >5 discrete populations; and
Study area may be on boundary of known regional distribution
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Ranking
Description
Low
Known range of taxon extends >50km; and
Taxon known from >20 discrete populations; and
Study area not on boundary of known regional distribution
3.12 Limitations of Survey
Table 8 presents the limitations of the flora and vegetation survey of the Study Area in
accordance with EPA Guidance Statement No. 51 (EPA 2004).
Minor limitations have been noted with regard to aspects such as disturbance levels (fire
history) and access issues, affecting both structure and composition of the vegetation in some
areas and ability to access vegetation; however, these were seen as being minor. The
historical level of information with regards to CS flora taxa is high; however, additional
survey of final footprints to determine the level of impact to such taxa is likely to be required,
especially for newly recorded species such as Paracaleana dixonii (T-DRF). Further
investigation including analysis of several VTs may in future be warranted, after moderate
levels of variability were seen.
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Table 8:
Limitations of the Flora and Vegetation Survey of the Study Area
Level of Limitation on Survey
Comment
Level of survey.
No limitation.
Level 2 (Detailed) Survey: A detailed survey was conducted throughout September to
November 2012 within the usual peak flowering season in the Northern Sandplain Region
over the majority of the Study Area. Replicated quadrats were established in each VT
identified by initial aerial photograph interpretation over the Study Area. There was also
inclusion of historical data (both recorded in spring and other seasons) for portions of the
existing Cooljarloo mining area.
Competency/experience
of
the
consultant(s) carrying out the survey.
No limitation.
Woodman Environmental personnel have had experience in conducting similar
assessments in the Northern Sandplain Region, with mentoring given to less experienced
botanists throughout the survey. All data collected in the field was quality assessed by
senior Woodman Environmental personnel and all plant identifications verified by senior
Woodman Environmental personnel.
Scope (floral groups that were sampled;
some sampling methods not able to be
employed because of constraints?)
No limitation.
All vascular groups that were present during the detailed survey were sampled; good foot
and vehicle access to most of the Study Area allowed for appropriate sampling techniques
(quadrat establishment, foot transects) to be employed. Survey over most of study area
undertaken at usual peak flowering time (Spring).
Proportion of flora identified, recorded
and/or collected.
No limitation.
High proportion (approximately 80 % of total expected taxa in the area; see Section 3.6) of
perennial and ephemeral vascular taxa recorded; adequate intensity and method of survey,
and good average rainfall totals prior to commencement of survey (between June and
August 2012). All vascular taxa recorded had at least one reference specimen collected,
with specimens identified at the WAHerb and a selection of new taxa for the area
recorded.
Sources of information e.g. previously
available information (whether historic
or recent) as distinct from new data.
No limitation.
Sources include government databases (DPaW TP List, TPFL and WAHerb databases)
and numerous unpublished studies undertaken both by Woodman Environmental and other
consultants within or adjacent to the Study Area; historical locations of CS flora taxa
within the Tronox database also accessed. Good contextual information was available
including previous local experience of Woodman Environmental.
The proportion of the task achieved and
further work which might be needed.
Minor limitation on survey of
distribution of CS flora taxa.
Level 2 survey complete, intensity considered to be adequate. Statistical analysis
considered adequate, however delineation of VTs may benefit from additional statistical
analyses. Further survey of CS flora to accurately define impacts may be required,
especially in relation to newly recorded CS flora.
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Potential Limitation Factor
Level of Limitation on Survey
Comment
Timing/weather/season/cycle.
No limitation.
Detailed field survey conducted throughout September to November 2012. Peak
flowering season for the area, with average rainfall over the usual ‘wet’ winter months
(June - August) and leading up to the survey; taxa of both ephemeral and perennial taxa
flowering at the time of the survey.
Disturbances (e.g. fire, flood, accidental
human intervention etc.), which affected
results of survey.
Minor limitation.
Previous fire history of parts of the Study Area influenced patterns discernible from aerial
photography and also existing structure and composition of the vegetation in some areas;
this had a minor effect on the survey results in regard to vegetation polygon boundaries.
Intensity of survey.
No limitation.
Survey intensity adequate to identify floristic and structural groupings of terrestrial flora as
required by a Level 2 survey, with replication of quadrats through plant community types
and additional foot searching allowed for identification of native and introduced taxa.
Lower intensity of survey over areas where access was more difficult. Lower density of
sampling in western and far southern parts due to limited access and previously established
sites (historical data). Moderate level of searching for CS flora taxa over potential areas of
impact (mainly historical data).
Completeness and mapping reliability.
Minor limitation.
Vegetation survey of Study Area considered complete; additional searching of footprints
and surrounds for certain CS flora taxa may be required. Mapping reliability good as high
resolution aerial photography was used, 235 new quadrats were established (total 370
quadrats used in analysis), and foot and vehicle transecting was employed; fire history
affected some vegetation patterns discernible on aerial photography. Statistical analysis
returned generally strong groups, however several VTs contained either moderate levels of
variation or appeared very similar to other groups suggesting additional statistical analysis
may be warranted.
Resources and experience of personnel.
No limitation.
Adequate resources and taxonomists with appropriate expertise in Northern Sandplain
flora were utilised. Woodman Environmental personnel with adequate experience in the
Northern Sandplains area were utilised, mentoring given to less experienced team
members.
Remoteness and/or access problems.
Minor limitation.
Access to the Study Area was considered adequate given the compact nature of the Study
Area, occurrence of local tracks and proximity of public roads. Access was more difficult
in the far southern and western parts of the Study Area.
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4.
RESULTS
4.1
Flora of the Study Area
In total, 1156 discrete vascular flora taxa and 1 putative hybrid have been recorded within or
immediately adjacent to the Study Area, representing 86 families and 318 genera. This
includes 1063 native taxa, and 93 introduced (weed) taxa. The families with the highest
number of taxa were Myrtaceae (134 taxa), Proteaceae (104 taxa), Fabaceae (98 taxa),
Cyperaceae (67 taxa) and Asteraceae (64 taxa). A full list of taxa is presented in Appendix E.
A total of 641 flora taxa were recorded during surveys in 2012, of which 65 are introduced.
This includes 81 native plant taxa (including 8 with incomplete identifications) and 34
introduced taxa which have not previously been recorded within the Study Area.
4.1.1
Conservation Significant Flora Taxa
A total of 67 discrete CS flora taxa, including five potential CS flora taxa (those taxa with
indeterminate identifications that possibly represent CS flora) have been recorded from within
the Study Area during both the 2012 and historical surveys (Table 9). This total includes four
T-DRF taxa, as listed by DPaW (Strijk 2013; DPaW 2013a). A total of 23 CS flora taxa were
recorded during the current (Spring 2012) surveys. Locations of the CS flora known from
within the Study Area are shown in Figures 7.1 - 7.5, and presented in Appendix H.
Table 9 indicates the number of locations, the equivalent number of populations and the VTs
in which these taxa have been recorded to occur within the Study Area. Note that records
from Cleared (C) or Rehabilitated (R) areas are historical records; the vegetation in these
areas are now either cleared, or have been cleared and rehabilitated. The listing of vegetation
types includes all VTs in which these CS flora taxa have been recorded; the preferred habitat
of each of these taxa (the most common VTs in which these taxa have been recorded) are
further described in Appendix I.
The source data of these taxa and location records has been taken from all historical studies
summarised in Section 2.5 (where specific locational data is available), results of searches of
relevant DPaW databases (DEC 2012) and the Tronox Iluka Database (Tronox 2013b). A
dash (‘-’) indicates that no point location data is available.
Table 9:
Summary of Conservation Significant Taxa Known from within the Study
Area
Taxon
Conservation
Code (DPaW
2012c)
Number of
Locations
Recorded in
the Study Area
Total Number of
Populations
Known in the
Study Area
Vegetation
Types in
Which Present
Allocasuarina grevilleoides
P3
2
2
7
Andersonia gracilis
T-DRF (VU)
1094
39
1, 2, 5, 6, 7, 9b,
17, 18, C, R
Angianthus micropodioides
P3
30
15
2, 5, 13
Anigozanthos humilis subsp .
chrysanthus
P4
3
3
17, 18
Anigozanthos viridis subsp.
terraspectans
T-DRF (VU)
57
22
1, 2, 4, 5, 6, 9b,
17, 18 C, R
Anigozanthos viridis subsp .
?terraspectans
T-DRF (VU)
2
2
1
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