Characteristics of Threatened Communities



Yüklə 116.19 Kb.
səhifə7/10
tarix21.08.2017
ölçüsü116.19 Kb.
1   2   3   4   5   6   7   8   9   10

Northern Plains Grassland Community


The Northern Plains Grassland Community is restricted to the naturally treeless plains of northern Victoria, and dominated by largely perennial tussocky grasses and an occasional, sparse occurrence of trees or large shrubs.

The community is a tussock grassland dominated by Danthonia spp. (including Danthonia setacea = Rytidosperma setaceum and D. caespitosa = Rytidosperma caespitosum) and Stipa spp. (including Stipa nodosa = Austrostipa nodosa and S. gibbosa = Austrostipa gibbosa) and other sub-dominant grasses, together with a variety of shrubs and herbs. The families Asteraceae (including Brachyscome chrysoglossa and Vittadinia gracilis) and Chenopodiaceae (including Atriplex semibaccata, Maireana excavata, Einadia spp.) are characteristic. The community is readily distinguished from other grasslands and grassy woodlands in Victoria by the absence of Themeda triandra.

The Northern Plains Grassland Community extends from Echuca in the east to the Patho Plains near the Loddon River in the west. Its soil type and rainfall are probably the two main influences on its floristic composition, although this has been much modified by land-use practices. Soils are heavy and vary from calcareous clay loams to cracking clays that may be inundated for short periods. The higher rainfall regions to the east tend to have greater representation of native perennial grasses while the drier areas to the west tend to be richer in chenopods.


Plains Grassland (South Gippsland) Community


The Plains Grassland (South Gippsland) Community varies in structure from closed tussock grassland to open woodland. Its original vegetation structure is likely to have been an open woodland that included areas of very sparsely-treed tussock grassland with shrubby zones associated with drainage lines.

Grass swards in this community are dominated by Kangaroo Grass (Themeda triandra) and Mat Grass (Hemarthria uncinata = Hemarthria uncinata var uncinata) on drier sites, and Common Tussock Grass (Poa labillardieri) on wetter sites. Characteristic species include Common Blown-grass (Agrostis avenacea = Lachnagrostis filiformis), Smooth Wallaby-grass (Danthonia laevis = Rytidosperma laeve), Heath Wallaby-grass (D. semiannularis = Rytidosperma semiannulare), Mat Grass (Hemarthria uncinata = H. uncinata var. uncinata), Finger Rush (Juncus subsecundus), Common Bog Sedge (Schoenus apogon), Common Tussock-grass (Poa labillardierei var. labillardierei) and Blown Grass (Agrostis aemula = Lachnagrostis aemula). Where trees occur they include a sparse cover of Manna Gum (Eucalyptus viminalis), Drooping She-oak (Allocasuarina verticillata), Blackwood (Acacia melanoxylon) and Black Wattle (A. mearnsii), while shrub species recorded include Golden Spray (Viminaria juncea), Swamp Paperbark (Melaleuca ericifolia) and Prickly Tea-tree (Leptospermum continentale).

This community type occurs in places on the Gippsland plains between the Yarram region, between Seaspray and Welshpool, on the east and the top of Western Port Bay on the west.

Port Phillip Bay Entrance Deep Canyon Marine Community


This is a highly diverse, varied and complex marine community of reef-dwelling sessile invertebrates, chiefly sponges, ascidians, bryozoans, hydrozoans and corals, with the sponges collectively forming what are often referred to as ‘sponge gardens’. The community covers the reef surface at depths below 20-25 m within a steep-sided underwater canyon up to 100 m deep at the entrance to Port Phillip Bay.

The sponge gardens within the community contain over 271 named species of sponge, 115 of which are endemic to the area. This community is also a centre of southern Australian bryozoan diversity, with a greater number of species represented than in the whole of Europe. It is also one of only three areas in Victoria known to support a highly diverse hydrozoan fauna.

The underwater canyon itself bisects a plateau of limestone (calcarenite) reefs, up to 17 m in depth and 1 km in width, and is the main passageway through the Bay entrance for the twice-daily tidal exchange of water between the oceanic waters of Bass Strait and the approximately 2000 km2 area of Port Phillip Bay. Water currents of great strength (3-8 knots) are produced; these form what is known as ‘The Rip’, and lead to a set of marine habitats and conditions that are unique in Victoria and probably Australia.


Red Gum Swamp Community No. 1


The Red Gum Swamp Community No. 1 is a community dominated by River Red Gum (Eucalyptus camaldulensis), and distinguished from other communities that include River Red Gum by the presence of seasonal or intermittent surface water up to a depth of 40 cm that can inundate a site for up to four months of the year.

In wetter examples of this community, the ground stratum is typically dominated by Running Marsh-flower (Villarsia reniformis), Joint-leaf Rush (Juncus holoschoenus), Soft Bog-sedge (Schoenus tesquorum) and Common Spike-sedge (Eleocharis acuta). Frequent sub-dominants in such areas are: Rush Sedge (Carex tereticaulis), Purple Bladderwort (Utricularia dichotoma), Prickfoot (Eryngium vesiculosum), Rough Raspwort (Haloragis aspera), Slender Goodenia (Goodenia gracilis), Yellow Rush (Juncus flavidus), Small Trigger-plant (Stylidium despectum) and Floating Pondweed (Potamogeton tricarinatus).

At the edges of this community and in drier examples the vegetation is not usually dense, with individual plants separated by bare soil and/or soil crust. The sparse to mid-dense ground stratum is usually dominated by Common Wallaby-grass (Danthonia caespitosa) and Brown-back Wallaby-grass (Danthonia duttoniana), along with Blue Devil (Eryngium ovinum) and Soft Bog-sedge (Schoenus tesquorum), except in gilgais where Veined Swamp Wallaby-grass (Amphibromus nervosus) dominates. Frequent sub-dominants include Common Sneezeweed (Centipeda cunninghamii), Lemon Beauty-heads (Calocephalus citreus), Poison Lobelia (Lobelia pratoides), Scaly Buttons (Leptorhynchos squamatus) and Paper Sunray (Helipterum corymbiflorum).

The distribution of Red Gum Swamp Community No. 1 in Victoria is very localised and likely to have always been restricted. The community is currently known to occur in western parts of the Wimmera Catchment Management Authority (CMA) and Glenelg–Hopkins CMA areas. A number of these sites are on private land. In the past this community may have been somewhat more widespread.


1   2   3   4   5   6   7   8   9   10


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

    Ana səhifə