EXECUTIVE SUMMARY A field survey of the Wallaby Prospect was performed over two site visits during Spring and following summer rains; 3-4 September 1998 and 24-25 February 1999. This survey documented flora found over the area, and described ten distinct vegetation map-units associated with the mining leases. Vegetation types encountered were described and categorised, and the botanical significance of the vegetation in the local and the regional contexts was assessed. The ten map-units described were: Main Exploration Area A1 Halophytic Dwarf Scrub D B Atriplex vesicaria Low Heath D C Open Low Scrub A on Sandy Dunes Bordering Lake Carey D1 Mulga Low Woodland A E Melaleuca uncinata Low Woodland B Proposed Haul Road Route A2 Halosarcia Dwarf Scrub D around Salt Pans F Maireana pyramidata Dwarf Scrub C G Acacia kalgoorliensis Open Scrub D2 Mulga Low Woodland A above Low Grass on Deep Aeolian Sands D3 Mulga Low Woodland A along Drainage Lines A total of 125 species of flowering plants from 50 genera and 24 families was identified over the Wallaby survey area. Those families showing highest species richness were Chenopodiaceae (37 spp.), Myoporaceae (15 spp.), Poaceae (10 spp.), Asteraceae (10 spp.), Mimosaceae (9 spp.) and Caesalpiniaceae (7 spp.). These six families accounted for 88 of the total 125 species recorded. All ten map-units described are well distributed regionally, and all but Map-unit G (Acacia kalgoorliensis Open Scrub) are well distributed locally. Recent biological surveys around Lake Carey however have confirmed a wider distribution for this community than initially realised. Traverses made around the northern and north-eastern margins show an extension to the populations recorded along the proposed Wallaby haul road. One of the species identified from the survey area, Acacia kalgoorliensis, is listed as "Priority 3 flora" under the Wildlife Conservation (Rare Flora) Notice (1994) and Declared Rare and Priority Flora List for Western Australia (Atkins 1996). A second species, Halosarcia "Angel Fish Island" sp., is presently restricted to the margins of Lake Carey, based on current collection details. It has however, been collected from a number of populations and appears to readily colonise disturbed surfaces. It may be given conservation status in the near future following further taxonomic review of the genus. TABLE OF CONTENTS EXECUTIVE SUMMARY i 1. Preamble 1 2. INTRODUCTION 1 Regional Setting 1 Climate 2 3. Vegetation and Flora 2 Background 2 Objectives and Methods 3 Results 3 Flora 3 Vegetation 4 Main Exploration Area 4 A1 Halophytic Dwarf Scrub D 4 B Atriplex vesicaria Low Heath D 6 C Open Low Scrub A on Sandy Dunes Bordering Lake Carey 7 D1 Mulga Low Woodland A 7 E Melaleuca uncinata Low Woodland B 9 Proposed Haul Road Route 10 A2 Halosarcia Dwarf Scrub D around Salt Pans 10 F Maireana pyramidata Dwarf Scrub C 11 G Acacia kalgoorliensis Open Scrub 11 D2 Mulga Low Woodland A above Low Grass on Deep Aeolian Sands 12 D3 Mulga Low Woodland A along Drainage Lines 13 Local and Regional Distribution of Map-units 15 Threatened Flora 16 Potential Impacts 17 4. bibliography 24 LIST OF TABLES TABLE 1: Mixed Halosarcia spp. Dwarf Scrub D. 5 TABLE 2: Halophytic Complex forming Dwarf Scrub D. 5 TABLE 3: Frankenia sp. and Lawrencia sp. Open Dwarf Scrub D. 6 TABLE 4: Species common to Map unit B - Atriplex vesicaria Low6Heath D. 6 TABLE 5: Species common to Map unit C - Open Low Scrub A on Sandy Dunes Bordering Lake Carey. 7 TABLE 6: Species common to Map unit D1 - Mulga Low Woodland A. 8 TABLE 7: Species common to Map unit E - Melaleuca uncinata Low Woodland B. 9 TABLE 8: Species common to Map unit A2 - Halosarcia Dwarf Scrub D around Salt Pans. 10 TABLE 9: Species common to Map unit F - Maireana pyramidata Dwarf Scrub C. 11 TABLE 10: Species common to Map unit G - Acacia kalgoorliensis Open Scrub. 12 TABLE 11: Species common to Map unit D2 - Mulga Low Woodland A above Low Grass on Deep Aeolian Sands. 13 TABLE 12: Species common to Map unit D3 - Mulga Low Woodland A along Drainage Lines. 14 LIST OF FIGURES FIGURE 1: Plan of the Wallaby deposit showing the open cut and proposed haul road route (see insert). 26 FIGURE 2: Vegetation types of the Wallaby Project represented as ten map-units (see insert). 27 LIST OF APPENDICES APPENDIX 1: Vegetation classification used for the Jubilee Flora Survey (from Muir 1977). A1:1 APPENDIX 2: Conservation Codes for Western Australian Flora (see Atkins 1996). A2:1 APPENDIX 3: Flora of the Wallaby Project Area. A3:1 LIST OF PLATES PLATE 1: Halosarcia spp. (samphire) occurred as scattered individuals around the immediate margin of Lake Carey, a zone subject to periodic inundation. 18 PLATE 2: Plant species diversity increased along the low foredune crest, approximately 10 m from the lake edge. Halosarcia remained the dominant genus. 18 PLATE 3: Gypsiferous soils inland of the lake shoreline gave rise to the formation of an open low shrubland dominated by Frankenia species. 19 PLATE 4: Atriplex vesicaria (bladder saltbush) Low Heath D was the dominant vegetation unit present over the lake flats. 19 PLATE 5: The low vegetation cover typical over the lake flats was interrupted by small pockets of pale coarse sand, which supported a taller vegetation cover. 20 PLATE 6: Approximately 500 m from the lake edge Atriplex vesicaria Low Heath D grades into Mulga Low Woodland A, which occurs in red aeolian quartz sand. 20 PLATE 7: Melaleuca uncinata (broombush) is prevalent around the edge of Ti Tree Dam. This species is well adapted to tolerate periodic inundation. 21 PLATE 8: Salt pans were common around the Wallaby lease. A number of the larger salt pans did not support vegetation in the central catchment (background), however Halosarcia spp. were common around the fringes of these systems. 21 PLATE 9: Maireana pyramidata (foreground) formed a dominant vegetation unit along the haul road. 22 PLATE 10: Acacia kalgoorliensis Open Scrub was widespread along the haul road route, occurring on shallow soils over hardpan, commonly with a stony ironstone surface. 22 PLATE 11: The Priority 3 species Acacia kalgoorliensis occurred to a height of 4 m. 23 PLATE 12: The mid-shrub Eremophila forrestii and grass Eragrostis eriopoda were both common to Map-unit D2 - Mulga Low Woodland A above Low Grass on Deep Aeolian Sands. 23 1. Preamble Placer (Granny Smith) Pty Ltd holds Mining and Exploration leases in the north-eastern gold fields area of Western Australia, approximately 20 km south of Laverton on rangeland that is used for grazing sheep (Mt Weld Station) (Figure 1). Placer (Granny Smith) Pty Ltd currently operates one open cut pit (Sunrise) however plans to develop a number of new resources in the coming years. The recent discovery of the Wallaby prospect is anticipated to lead to the early development of this resource. It is proposed that a new open cut pit is developed along with the construction of an associated haul road. It can be anticipated the new haul road will extend approximately 6.85 km to the east where it will join up with the proposed "Hill Side Well" haul road (Figure 1). This report is based on two field surveys conducted in the area between 3-4 September 1998 and 24-25 February 1999. The initial survey occurred during the month of maximum flowering potential. The second survey occurred following a summer rainfall event, capturing a number of grasses not recorded during the initial survey. The objectives of the survey were to document the flora found on the mining leases associated with open cut and haul road disturbances, to describe and categorise the vegetation types encountered, and to assess the botanical significance of the vegetation in the local and the regional contexts. 2. INTRODUCTION Regional Setting The Project area lies in the Austin Botanical District of the Eremaean Botanical Province. Previous surveys have documented the broad land systems and vegetation units present in the area, however detailed assessment of local associations is lacking. Beard (1974) described vegetation of the area as "mulga and saltbush succulent steppe", grading into "mulga low woodland" along the proposed haul road route to the east. Pringle, Van Vreeswyk and Gilligan (1994) provide resource condition statements for the north eastern goldfields (Menzies, Edjudina, Leonora, Laverton, Sir Samuel and Duketon 1: 250 000 scale map sheets), with reference to pastoral impacts. Over these areas pastoralism covers approximately 83 percent of their survey area. The most frequently observed impacts were loss in perennial species richness and loss in perennial plant density. Major alterations in vegetation and consequent erosion were observed within the chenopod shrublands, as a result of historical overgrazing. Rangeland encompassing the "Wallaby" area has recently been destocked. The most recent Range Condition Report conducted on the Mt Weld pastoral lease, found 71 percent of the rangeland was in fair to good condition and only 8 percent was in very poor condition (Pringle 1994). Climate The region experiences hot, dry summers and cool winters. In the temperate zones of Australia, Beard (1990) gives an arid classification to areas with an average annual rainfall of less than 250 mm. Laverton (townsite) records an average annual rainfall of 221 mm, with highest monthly averages recorded between January-June (WA Regional Office of the Bureau of Meteorology 1998). Winter rains are associated with southern depressions, and are generally more reliable. Summer rain comes from sporadic and localised thunderstorms (or occasionally remnant tropical cyclones) which give sudden heavy falls. The summer rains are usually of higher intensity and shorter duration than the autumn rains, contributing to an often erratic annual range.