Conservation Science W. Aust. 7 (2) : 349–361 (2009) Flora and vegetation of banded iron formations of the Yilgarn Craton: Cashmere Downs Range RACHEL MEISSNER1, GAYNOR OWEN1 & BEN BAYLISS1,2 1 Science Division, Department of Environment and Conservation, PO Box 51, Wanneroo, Western Australia, 6946. Email: [email protected] 2 Current Address: Avon Natural Diversity Alliance (ANDA), Department of Environment and Conservation, Locked Bag 104,Bentley Delivery Centre WA 6983. ABSTRACT A quadrat based study of the flora and plant communities of the banded ironstone range of Cashmere Downs, found 144 taxa, with 142 native and two weeds. Two priority taxa and five taxa with significant range extensions (>100km) were found. Fifty one quadrats were established to cover the major geographical, geomorphological and floristic variation across the range. Data from 49 of these quadrats were used to define five community types, with two subtypes in two communities. Differences in communities were strongly correlated with underlying geology and soil fertility. None of the plant communities found on the banded ironstone ranges on Cashmere Downs are represented in secure conservation reserves. INTRODUCTION of banded ironstone ridges. Mafic and ultramafic rocks are prevalent amongst banded iron formations. The second Cashmere Downs is a pastoral lease located on the area to the east runs in a north-east south-west line. The northern side of Lake Barlee, approximately 100km south ridges are predominantly banded iron formations, at a of Sandstone, and 550 km northeast of Perth, in the central higher elevations and have fewer exposed outcrops of mafic Goldfields region of Western Australia. The range on and ultramafic rock. Cashmere Downs is located in central region of the Yilgarn The climate of the region is semi-desert Mediterranean Craton on the Youanmi Terrane (Cassidy et al. 2006). It with mild wet winter and hot dry summers (Beard 1990). is characterized by strike ridges and subrounded hills, with Mean annual rainfall at Cashmere Downs Station is prominent ridges of banded-iron formations and chert 252.9 mm, with moderate seasonal variation over the 83 (Chen 2004). There is currently no accepted topographic years of record (1919–2002: decile 1, 128.5 mm; decile name for these features and here will be referred to as the 9, 426.9 mm). The highest maximum temperatures occur Cashmere Downs Range. The whole area has previously during summer, with January as the hottest month (mean undergone exploration for base metals and is currently maximum temperature 36 °C and mean 6.2 days above being explored for iron ore. 4 0 °C). Winters are mild with lowest mean maximum The Cashmere Downs Range belongs to the northern temperature recorded for July of 17.5 °C. Temperatures section of the Mount Elvire greenstone belt which is occasionally fall below 0 °C in winter (a mean 0.9 days structurally composed of several synclines resulting from below 0 °C), with a mean minimum of 5.9°C in July. several deformation events. The range is composed of The Cashmere Downs Range is located in the east of ultramafic rocks (generally referred to as greenstones), the Murchison bioregion, but has only been mapped at a mainly tremolite-chlorite (-talc) schists, intercalated with very broad scale. Beard (1976) mapped the Murchison metamorphosed mafic rocks and banded iron formations region at 1:1,000,000 and mapped the range as mulga (Stewart et al. 1983, Chen 2004). Mafic refers to igneous and Acacia quadrimarginea scrubland. A regional survey rocks or minerals of high magnesium-iron content of the Youanmi-Leonora region, where the range is (Eggleton 2001). Metagabbro is the dominant mafic rock located, reported a general cover of Acacia scrub with in the Cashmere Downs area and is commonly found scattered shrubs of Senna spp. and Ptilotus obovatus and exposed on the flanks of banded ironstone and chert ridges herbaceous plants such as Cheilanthes sp. (Milewski & Dell, (Chen 2004). 1992) on the upland areas. Payne et al. (1998) mapped The range on Cashmere Downs is the result of several the range as part of the Brooking land system, defined as folds and consequently can be divided into 2 main areas. ridges, hillslopes, stony plains of banded ironstone, The first area, at the western side of the range, runs dominated by the stony ironstone mulga shrublands approximately north-south with a more complex geology vegetation class (Acacia aneura tall shrublands). To date, there have been no targeted surveys of the Cashmere Downs Range and the only descriptions have © The Government of Western Australia, 2009 been part of a broader condition or mapping survey (Beard 350 R. Meissner et al. 1976; Payne et al. 1998). Previous vegetation surveys of METHODS other Banded Iron Formation ranges have shown the presence of rare and endemic taxa and floristic The methodology employed in this survey follows the communities that are unique to and often restricted to standard procedure used in previous vegetation surveys the range (Gibson and Lyons 1998a, 1998b, 2001a, of other ironstone and greenstone ranges in Western 2001b; Gibson 2004a, 2004b; Markey and Dillon 2008a, Australia (Gibson and Lyons 1998a, 1998b, 2001a, 2008b; Meissner and Caruso 2008a, 2008b, 2008c). The 2001b; Gibson 2004a, 2004b; Markey and Dillon 2008a, aim of the present study was to undertake a detailed 2008b; Meissner and Caruso 2008a,b,c). Fifty one 20 x floristic survey of the Cashmere Downs and to identify 20 m quadrats were established on the crests, slopes and and describe the flora and plant communities that occur foot slopes of the range on Cashmere Downs in August on these ironstone ranges. This paper is one of a continuing and September 2006 (Figure 1). Quadrats were established series examining the flora and vegetation of banded iron to cover the broader geographical and geomorphological formation ranges in the Yilgarn (Markey and Dillon 2008a, variation on banded iron formations and adjacent 2008b; Meissner & Caruso 2008a, 2008b, 2008c). geologies found in the study area. The quadrats were Figure 1. Location of the study area, approximately 100km south of Sandstone, on the Cashmere Downs pastoral lease. Fifty one quadrats (V) were established on the ranges of Cashmere Downs. The 480m contour is shown. Flora and vegetation of Cashmere Downs Range 351 strategically placed in vegetation across the range in a analyses of banded ironstone ranges and to allow these toposequence, from crests and slopes of exposed bedrock comparisons not to be confounded by temporal variations and scree, to footlsope and plains composed of colluvial in annuals numbers (Gibson & Lyons 1998 a, b, 2001a,b; deposits. Each quadrat was permanently marked with four Gibson 2004a,b; Markey and Dillon 2008a,b; Meissner steel fence droppers and their positions determined using and Caruso 2008a,b,c). The quadrat and species a GPS unit. All vascular plants within the quadrat are classifications were undertaken using the Bray - Curtis recorded and collected for later identification at the coefficient followed by Flexible UPGMA (Unweighted Western Australian Herbarium. pair-group mean average; β = -0.1; Belbin 1989) Data on topographical position, disturbance, clustering. The Bray – Curtis coefficient is commonly used abundance, size and shape of coarse fragments on surface, in ecological studies especially in presence/ absence the abundance of rock outcrops (defined as the cover of datasets (Belbin 1989; Clarke et al. 2006) while Flexible exposed bedrock), cover of leaf litter and bare ground UPGMA is an effective method of recovering true group were recorded following McDonald et al. (1990). structure (Belbin & McDonald 1993). PATN uses a beta Additionally, growth form, height and cover were recorded value of -0.1 in Flexible UPGMA to dilate and counteract for dominant taxa in each strata (tallest, mid- and lower). the known underestimation of larger association values The quantitative data were used to describe the plant (Belbin 1989; Belbin et al. 1992). Indicator species and communities following McDonald et al. (1990). species assemblages characterising each community were determined following Dufréne and Legendre (1997) using Soil Analysis INDVAL routine in PC-ORD (McCune and Mefford 1999). Quadrats were ordinated using SSH (semi-strong Twenty soil samples were collected from the upper 10 cm hybrid multidimensional scaling), a non parametric of the soil profile within each quadrat. The soil was bulked approach and not based upon the assumptions of linearity, and the 2 mm fraction extracted using the Mehlich No. 3 or presume any underlying model of species response procedure (Mehlich 1984). The extracted samples were gradients. Correlations of environmental variables were analysed for B, Ca, Cd, Co, Cu, Fe, K, Mg, Mn, Mo, Na, determined using PCC (Principal Component Ni, P, Pb, S and Zn using an Inductively Coupled Plasma Correlation) routine and significance determined by – Atomic Emission Spectrometer (ICP-AES). The MCAO (Monte Carlo Attributes in Ordination) routine extracted samples were then analysed using Inductively in PATN (Belbin 1989). PCC uses multiple linear Coupled Plasma – Atomic Emission Spectrometer (ICP- regressions of variables in the three dimensional ordination AES). This procedure is an effective and cost efficient space (Belbin 1989). Statistical relationships between alternative to traditional methods for evaluating soil quadrat groups were tested using Kruskal-Wallis non fertility and has been calibrated for Western Australian parametric analysis of variance (Siegel 1956), followed by soils (Walton and Allen 2004). pH was measured in 0.01M Dunn’s Multiple comparison test (Zar 1999). CaCl2 at soil to solution ratio of 1:5. Effective cation Nomenclature generally follows Paczkowska and exchange capacity (eCEC) was calculated from the sum Chapman (2000). of exchangeable Ca, Mg, Na and K (Rengasamy & Churchman 1999). Exchangeable Ca, Mg, Na and K were obtained by multiplying the values of Ca, Mg, Na and K RESULTS obtained from ICP-AES by a standard constant.