Characteristics of Threatened Communities



Yüklə 116.19 Kb.
səhifə8/10
tarix21.08.2017
ölçüsü116.19 Kb.
1   2   3   4   5   6   7   8   9   10

Rocky Chenopod Open-Scrub Community


The Rocky Chenopod Open-Scrub Community may be described as an open-scrub community with a shrubby understorey and a characteristically open ground layer. Soils are generally skeletal and high in calcium, increasing with depth. Chenopods are abundant. The canopy is formed from stands of frequently stunted and multi-stemmed Bull Mallee (Eucalyptus behriana) with Yellow Gum (E. leucoxylon = E. leucoxylon subsp. connata), and/or Grey Box (E. microcarpa) and occasional Red Box (E. polyanthemos) towards the margins. Box Mistletoe (Amyema miquellii) is widespread in the canopy.

Typical examples of the community are dominated by Bull Mallee. The shrubby understorey is predominantly Gold-dust Wattle (Acacia acinacea), Golden Wattle (A. pycnantha), tall Cassinia species (Cassinia longifolia and C. arcuata) and shrubby chenopods, notably Fragrant Saltbush (Rhagodia parabolica) and Barrier Saltbush (Enchylaena tomentosa = Enchylaena tomentosa var. tomentosa). Small-leaf Clematis (Clematis microphylla = Clematis decipiens) is found on medium-height and smaller shrubs. The ground layer contains a high proportion of ephemerals and several drought-tolerant perennial dwarf shrubs and herbs, including Inland Pigface (Carpobrotus modestus), Saloop Saltbush (Einadia hastata), Nodding Saltbush (Einadia. nutans = E. nutans subsp. nutans) and species of Sclerolaena. Although not a dominant feature of this layer, tussock grasses (notably Danthonia spp. = Rytidosperma spp., Poa spp. and Stipa spp. = Austrostipa spp.) are scattered throughout. Abundant bryophytes and soil lichens are also present. Rare species associated with this community include Brittle Greenhood (Pterostylis truncata), Kidney Saltbush (Atriplex stipitata), Fragrant Saltbush (Rhagodia parabolica), Spreading Eutaxia (Eutaxia diffusa = E. microphylla var. diffusa), Leafy Templetonia (Templetonia stenophylla), Turkey-bush (Eremophila deserti) and Cane Spear-grass (Stipa breviglumis = Austrostipa breviglumis) (rare both in Victoria and nationally).

The community has a very restricted distribution and less than 200 ha may currently exist, all on sites near Melbourne. The largest remnant of about 150 ha occurs in the vicinity of Djerriwarrh and Coimadai Creeks in the Long Forest area to the west of Melton (from which ‘Long Forest Mallee Community’, its former classification within the National Estate, was derived).

San Remo Marine Community


The San Remo Marine Community is an intertidal and subtidal reef community on a mixed substrate of mud, old basaltic rock and sand, at the south-eastern corner of Western Port. It occurs between the township of San Remo and the edge of the relatively deep eastern tidal channel that connects Western Port with Bass Strait, and runs in a SW-NE direction between Phillip Island and the mainland.

The community is extremely species-rich when compared with relatively impoverished reefs to the east and west. It is characterized by the recording of 93 species of opisthobranch mollusc, of which 21 have yet to be formally described and named. Other species include seagrasses, intertidal algae, and a variety of sponges, bryozoans, molluscs, crabs, echinoderms and fish. Of significance is the relative abundance of the rare bivalve Anadara trapezia, once widespread and frequently found in fossil beds and Aboriginal middens, but which has declined markedly in range since European settlement.

The substratum on which this community is found forms roughly a right-angled triangle. Its base is approximately 1.5 km of San Remo foreshore, which has a northerly aspect, unusual in Victoria. It then extends outwards and northwards to the tidal channel for a distance between a few metres at its southwest corner, near the San Remo end of the bridge to Phillip Island, to about 1.2 km from the foreshore at its north-eastern extremity. Currents in the channel become very rapid during rising and falling tides.

Sedge-rich Eucalyptus camphora Swamp Community


The Sedge-rich Eucalyptus camphora Swamp Community is characterized by a moderate cover canopy (20-50%) of Mountain Swamp Gum (Eucalyptus camphora = E. camphora subsp. humeana), 6-25 m in height, over a shrub layer dominated by Woolly Tea-tree (Leptospermum lanigerum) and a ground cover of diverse sedges and rushes.

Ground cover species include Fen Sedge (Carex gaudichaudiana), Tassel Sedge (C. fascicularis), Tall Sedge (C. appressa), Leafy Flat-sedge (Cyperus lucidus) and Soft Twig-sedge (Baumea rubiginosa), while grasses and herbs include Australian Gipsywort (Lycopus australis), Ridged Knotweed (Persicaria sp.) and Showy Willow-herb (Epilobium pallidiflorum). The community varies in structure from an open woodland or open grassy woodland to a closed shrubland and, where it has been highly disturbed, a grassland dominated by the Common Reed (Phragmites australis). Soft Twig-sedge is usually absent from seasonally-inundated sites. At drier sites Variable Sword-sedge (Lepidosperma laterale var. majus) is frequently co-dominant with the Carex species. Blackwood (Acacia melanoxylon) and Slender Tussock-grass (Poa tenera) are also found at the drier sites. Where the community is associated with well-defined stream-beds or near-permanent flowing water, Woolly Tea-tree may form a closed shrubland with scattered, emergent Mountain Swamp Gum. Ground cover species there include other species characteristic of seasonally inundated sites, such as Wing Pennywort (Hydrocotyle pterocarpa), Small River Buttercup (Ranunculus rivularis = Ranunculus amphitrichus) and Swamp Club-sedge (Isolepis inundata). Scented Paperbark (Melaleuca squarrosa) can be found co-dominant with Woolly Tea-tree in the lower reaches of ephemeral tributaries. In these areas, Mountain Swamp Gum has a cover of 5-20%.

The only known occurrence of the Sedge-rich Eucalyptus camphora Swamp Community is within the Yellingbo Nature Conservation Reserve in the Yarra Valley, 50 km east of Melbourne.


1   2   3   4   5   6   7   8   9   10


Verilənlər bazası müəlliflik hüququ ilə müdafiə olunur ©azkurs.org 2016
rəhbərliyinə müraciət

    Ana səhifə