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Issue Number #30
Issue Date Summer 2005
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Title The Native Grass Menagerie
Author Phil Watson
Email pajwa@southcom.com.au

Native grasses are once again being given the respect they deserve! Two hundred years of a 'remove and replace' attitude towards native grass-dominated habitats has now changed. Promote and enhance them at all costs is the new imperative!

This is reflected in the extent to which native grasses have successfully naturally regenerated in recent revegetation projects. This now provides one of the key success factors to be assessed when reviewing grassy community restoration projects.

Native grasses have also emerged as the plants of choice, for revegetating of degraded habitats and for establishing an exciting new landscape style based on mass plantings of native grasses. The new Melbourne Freeways are a fine testament to this!

Now home gardeners can be rewarded for growing their own native grass-dominated landscapes with the colourful dainty herbs, lilies and bush peas, which juggle for position amongst these domineering tufty, native grasses. More importantly, within a growing season, they yield a menagerie of fascinating insects, birds and wildlife.

Their Chequered History of Use and Abuse

Traditionally, grass-dominated habitats were an integral part of the aboriginal hunting and gathering life style. The sweet stem bases of Spear grass could be eaten like sugar cane. The Kangaroo, Spear and Tussock grass seeds could be ground into flour. With open palms, the aboriginal women could roll the tough fibrous leaves along their thighs to form a fine thread. A string could be plied from two or three threads and used to make dillies, mats and nets.

To attract kangaroo and harvest of bush tucker easily, aboriginals patch-burnt these grassy swards with hot fires to provide succulent 'green pick'. Only enough roos were killed to ensure that the many shrub and tree seedlings, which germinated after the hot fires, remained heavily grazed. This guaranteed that forest did not encroach across their valued grasslands, which now presents a deep problem for grassland managers.

In contrast to the aborigines, unaware farmers had little appreciation of the ecosystem services supplied by native grasses. For 200 years, native grasses suffered the onslaught of weed invasion, grazing, ploughing, fertilising, exotic pasture over-seeding and 5-acre sub-division. Frequent cool burning to force lush green shoots on Kangaroo grass padocks proved clever at first, but finally degraded them. Weeds or spine tipped, wiry awned seeded Spear grasses, which ruined fleeces and pierced eyes and skin have replaced them. Only a few remnants now remain, located in unexpected sanctuaries such as cemeteries, road and rail reserves.

Introducing Native Grasses and Their Roles

The palate of native grasses available for revegetation include Kangaroo Grass Themeda triandra, Wallaby grasses Austrodanthonia sp., Spear grasses Austrostipa sp., Plume Grasses Dichelachne sp., Common Wheat-grass Elymus scabrous, Blown grasses Agrostis sp., Tussock grasses Poa sp., Weeping Grass Microlaena stipoides, Forest Wire Grass Tetrarrhena distichophylla as well as the coastal sand binding grasses of Hairy Spinifex Spinifex sericeus, Salt-grass Distichlis distichophylla and Coastal Fescue Austrofestuca littoralis.

They not only command respect for their role of sustaining the intricate web of native fauna and flora, but they also provide the filtering role for our watersheds. They soak up the rainfall so it can infiltrate slowly down into the depleted underground aquifers. Alternatively, they draining across and erode our precious soil. Within the urban landscape native grass landscapes are popular due to their natural beauty, drought tolerance, resistance to vandalism and ease of maintenance. They now embellish many prestigious city landscapes and roadside plantings. Even florists are warming to the beauty of their unique flower heads, as seen in their new floral displays.

Habitat for Marsupials, Reptiles and Frogs

Kangaroos, Wallabies, Wombats and Pademelons feed on the aptly named Kangaroo and Wallaby grasses and their suites of inter-tussock herbs. Our small fury hop-alongs such as the Bettong, Southern Brown Bandicoot and Ringtail Possum all build nests for breeding, incorporating native grasses. It is a privilege to see a bettong with a tail coiled around a bundle of native grasses scurrying to build its nest! The Eastern Barred Bandicoot prefers the shelter of native grass tussocks to scratch for seeds and insects. They leave distinctive conical shaped holes in native grass patches after feeding on grubs which munching on the grass roots. Echidnas gorge on the insect treats inhabiting the native grasses. A torchlight safari may reward the keen observer! Native grasses are also a favoured habitat for reptiles such as the Grass Skink, Copperhead, White Lipped and Tiger snakes, which feed on the smaller prey and insects living amongst the native grasses.

The Southern Toddled and Smooth Froglet breed in low lying grassy patches, laying their eggs, on the expectation that the area will be flooded in autumn. Since they walk rather than hop and do not lay their eggs in water, they are radically different to most frogs. However, for the snakes and echidnas they are just as tasty as the other frogs!

Birds Thrive Amongst Native Grass Tussocks

Our native birds and even the nocturnal Greater and Lesser Long-Eared Bats scavenge grassy forest understoreys feeding on plump seed heads and insects. Pardalotes, Thornbills, Honeyeaters, Robins, Whistlers, Fantails, Wrens and the Welcome Swallow all line their nests with dried grasses interwoven with spider webs. Many of these birds busily collect 'beak fulls of nothing'. Closer inspection reveals a fine spider's silk being harvested. These birds, along with their mid to upper canopy feeding species, provide the key to preventing tree dieback. They are known to eat up to 70% of the leaf-feeding insects attacking the stressed trees. Remove or degrade the native grass understorey this ecosystem service rapidly declines as we see from the midlands highway.

Native grasses are ideal sites for web-producing spiders including the Wheel-web Spider. It spins its flimsy wheel-like web in an unusual horizontal position supported by the grass tussocks' intricate 3D architecture. They hang upside down under the web's hub. As they lack poison glands, they use their disproportional long front legs (it cannot walk on flat surfaces) to wrap and subdued their prey. By injecting digestive enzymes they liquefy and suck out the prey's flesh. Of course, birds pick them off like liquorice allsorts.

Habitats for Bees, Ants, Butterflies and Moths

Our small solitary native bees exploit the hollow grass flower stalks. They construct a series of pollen and honey filled cells, into which they lay their eggs. Each cell is sealed with waxy secretions and frass.

Many butterflies and moths larva have evolved to feed voraciously on native grasses. The White Grassdart lays its eggs on the Danthonia sp. and Poa sp. leaves which then hatch into pale green larva. These form a shelter by joining several leaves together. Here they pupate into butterflies that characteristically rest with its forewings held up over its body while its hind wings are held flat. The night feeding Dominula and Tasmanian Skipper butterfly larva also use silk to form a tubular shelter amongst Poa sp. Their butterflies feed on a range of native daisies in the inter-tussock spaces.

The Common Brown butterfly larva feed on Kangaroo Grass, whilst the in summer, adults frequent the flowers of the Native Box Bursaria spinosa. Interestingly, the Ptunarra Brown butterfly relies totally on Poa tussock grasses for their larval food, adult habitat and sunning spots. After mating they drop their eggs, like a low flying bomber, on the tussocks. The larva hatch to feed on the tussock tips. In early autumn, they pupate from the tussock's base into weak-flying gregarious adults.

Conclusion

Grassy woodland communities are diverse systems of checks and balances. To remove any part (roos, wrens, spiders etc) or to add foreign components (sheep, fertilizers, weeds, cool burns etc) will cause a dramatic alteration to the rules under which it functions. Finally do not manage a small grassy remnant under the illusion that it functions like a miniature, extensive grassy woodland, as it responds to a distinctly different set of rules.


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