The destruction of biodiversity is by far the most serious environmental issue facing Australia, with Melbourne and its surrounds being no exception. To preserve Melbourne’s remaining biodiversity, it is essential that currently threatened species and ecosystems are adequately protected and monitored. Listed as endangered under the Environment, Protection & Biodiversity Act (1999), the Matted Flax-lily (Dianella amoena), is one such species. It can be found, albeit in vastly depleted stocks, on the iconic Victorian Volcanic Plains.
The Victorian Volcanic Plains lie to the north and west of the Melbourne CBD, and are characterised by Cainozoic volcanic deposits, which feature rolling basaltic plains punctured by stony rises. Remnant populations of D. amoena have been recorded at Bundoora, Eltham, Craigieburn, Reservoir, and Epping. Within the Epping-Wollert Grassy Woodlands (a locality within Plains Grassy Woodland – EVC 55), where I often work, D. amoena can be found on occasion persisting naturally. However due to agricultural activities from the 1830s onwards, most notably intensive grazing, its distribution has become severely limited. Today, this perennial, often straggly, tufted lily, can perhaps be more commonly observed in the offset sites managed by the company I currently work for: Australian Ecosystems, and others. This article sheds a little bit of light on what it takes to manage this important federally listed endangered species.
Fig. 1: Bulbous fruit of Dianella amoena (Matted Flax-lily).
Geology and Soil of Epping-Wollert:
The D. amoena specimens I help manage consist of offset plantings located within the Aurora Estate, Epping. The practise of offsetting involves the translocation of species and/or ecosystems from a site under development to another site of ecological equivalence elsewhere in the landscape6. Aurora, where this particular offsetting program is taking place, consists of a new housing development traversing the peri-urban jurisdictions of Epping and Wollert in Melbourne’s outer north.
The soil of this region is often either a moderately acidic dark grey brown loam, with a lighter subsurface layer, or a slightly acidic dark grey to black heavy clay soil, with a slightly alkaline subsoil. These soils have developed from nutrient-rich Cainozoic basalts, in some cases extruded only several thousand years ago. Their subsequent evolution is in part a function of the climate of this area, with the relative lack of rainfall favouring the retention of silica and cations. In the case of much of Western Victoria, including parts of Epping-Wollert, this combination of younger basalts and incomplete leaching of elements, produces a form of clay (smectite) that shrinks and swells during seasonal wetting and drying. D. amoena has adapted to the wet cracking clay soils that are commonplace in this area, and prior to being destroyed by agriculture, were fairly commonplace in drainage lines and around ephemeral swamps.
Fig. 2: A quintessential Victorian Volcanic Plains rocky knoll featuring weathered vesicular basalt.
Fig. 3: The soils of Melbourne's north, including the study area (courtesy: Flora of Melbourne by Marilyn Bull).
The heavy basalt-derived clay soils and low rainfall – typically 500-700mm per year – of the Epping-Wollert region limit the range of plants able to flourish there. Trees in particular are limited by the hard, cracked soil that characterises the warmer months. Species that can be observed in the area include: Cassinia arcuata (Drooping Cassinia), Eucalyptus camaldulensis (River Red Gum), Acacia melanoxylon (Australian Blackwood), Acacia paradoxa (Paradox Acacia), Convolvulus angustissimus subsp. omnigracilis (Slender Bindweed), Eryngium ovinum (Blue Devil), Themeda triandra (Kangaroo Grass), Rytidosperma racemosum (Striped Wallaby-grass), and if you’re lucky, the threatened Amphibromus fruitans (River Swamp Wallaby Grass) and Carex tasmanica (Curly Sedge). Dianella amoena was historically an integral part of this vegetation assemblage, gracing the once capacious native grasslands and woodlands of the region. Unfortunately in many areas, particularly on disturbed sites, invasive exotic species have out-competed not only the vulnerable D. amoena, but other, more robust local natives. These weed species include: Phalaris aquatica (Bulbous Canary Grass), Brassica fruticulosa (Mediterranean Cabbage), Helminthotheca echioides (Bristly Ox-tongue), Cynara cardunculus (Artichoke Thistle), Rumex crispus (Curly Dock), Centaurium tenuiflorum (Slender Centaury), amongst many others.
Our goal is to successfully re-introduce D. amoena into the site, with the objective of facilitating a self-sustaining population. It’s a small, yet crucial job, if we are to ensure D. amoena, and Melbourne’s rich and unique biodiversity more generally, is protected not only for future generations, but indeed for its own sake.
Fig. 4: Convolvulus angustissima subsp. omnigracilis (Slender Bindweed) is present at Site #1.
Matted Flax Lily (Dianella amoena) management:
We (Australian Ecosystems Pty. Ltd.) manage two fenced-off areas of translocated D. amoena adjacent to the Aurora Estate in Epping, Melbourne. The first translocation site (Site #1) is situated on a higher elevation and boasts an archetypal rocky knoll. The other - Site #2, lies in an ephemeral depression approximately 500m from Site #1. The two environments are noticeably different, and as such require particular management strategies. Both sites are watered using an 800L tank and hose which is positioned on the back of a ute. This is connected to the irrigation pipes that run through both sites. Drip nozzles have been placed where each offset plant has been planted. Occasionally, drip nozzles become clogged and require replacement. Also, as the D. amoena, spread via rhizomes away from the initial nozzle, we add nozzles along the irrigation line to ensure the new shoots receive adequate water in periods of extreme heat. Brush-cutting and selective herbicide spraying is undertaken to ensure weeds don’t out-compete D. amoena (except in Golden Sun Moth flying season), and slug bait is applied when signs of slug damage are observed.
This site is higher up in the landscape, and considerably drier than Site #2. It is also less weed-infested and accommodates a larger assemblage of local native species. Native species, other than the transplanted D. amoena, found on this site include: Senecio quadridentatus (Cotton Fireweed), Epilobium sp. (Willow-herb), Rytidosperma and Austrodanthonia sp. (Wallaby Grasses), Themeda triandra (Kangaroo Grass), Cassinia arcuata (Drooping Cassinia), and Convolvulus angustissimus subsp. omnigracilis (Slender Bindweed). In general, Site #1 requires more water, but less weed control than Site #2. Site #1 is also perfect habitat for the endangered Golden Sun Moth (Synemon plana) due to the presence of Wallaby Grasses. During GSM flight-season – typically November to January – we refrain from both brush-cutting and herbicide application.
Site #2 sits in a swale-like depression. The heavy clay soil at this location is very adept at holding water, and is particularly susceptible to the seasonal cracking in the summer months. After rainfall events, the soil remains damp-to-wet underfoot for up to a week or more. Due to a combination of moisture retentive soil, high nutrients, and the fact that run-off tends to accumulate at the bottom of the landscape (which contains weed seed as well as excess nutrients from run-off), Site #2 is more weed infested than Site #1. Aside from the occasional Senecio quadridentatus (Cotton Fireweed) and Epilobium sp. (Willow-herb), this site tends to be dominated by weeds. The ever-opportunistic Helminthotheca echioides (Prickly Ox-tongue) being particularly problematic.
Fig. 5: Sometimes nozzles on irrigation lines require either cleaning or replacement. It is vital that all nozzles are monitored to ensure each D. amoena specimen is receiving water, particularly in the dry and desiccating heat of summer.
Fig. 6: Each D. amoena is accompanied by a metal tag.
Fig. 7: A D. amoena specimen at Site #1 exhibiting rhizomatous growth. Very promising! The omnipresent Nassella neesiana (Chilean Needle-grass) can be seen looming in the background.
Food For Thought: Biodiversity Conservation and Local Engagement:
On a theoretical level, I personally believe in the idea of the ‘co-construction’ of nature. That is, the acknowledgement that urban ecologies and landscapes are the product of engagements between human and non-human inhabitants of cities. Because of the rapid urbanisation of the Epping-Wollert Grasslands and Grassy Woodlands, and the proximity of houses to the D. amoena offset sites, I think it is fair to say that much of this region could now be categorised as an urban, or at the very least, peri-urban ecosystem. The intersection between biodiversity conservation and the local citizenry is therefore a vital factor, not only in terms of the long-term conservation of endangered species such as Dianella amoena and Synemon plana (Golden Sun Moth), but also in understanding how people interact with their surrounding landscape(s) more generally. Research demonstrates that people are more willing to help preserve an environment if they feel included within it. Thus building a relationship of mutual respect between scientists, land managers, and local citizens is, in my opinion, a key imperative. Whilst local native species may not be attractive to the average homeowner and gardener for use in their own gardens, the unavoidable existence of the surrounding landscape of Epping-Wollert and its unique biology, remains an important social and environmental interface. If through clever planning, public engagement, education programs, and mutual understanding, the local population can be included within the management framework, as opposed to excluded from it, as too often has been the case in biodiversity management in the past, perhaps we stand a better chance of not only achieving important conservation goals, but also in learning how citizens interact and value urban landscapes and nature more generally.
Fig. 8: The conventional conservation/biodiversity management approach.
Fig. 9: Me walking though Site #1 checking irrigation lines, nozzles, and slug damage.
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By Dominic Bowd (B.Sc./B.A. UNSW)