Variation of Tasmanian vegetation from East to West

Last updated

Tasmania can be broadly divided into two distinct regions, eastern and western, that exhibit major differences in climate, geology and vegetation. This divide, termed Tyler's Corridor [1] [2] (in recognition of Peter Tyler, a Tasmanian limnologist), runs from just south of the northwestern corner, and continues south, cutting roughly down the center of the island. [3] The vegetation changes occur principally due to variations in soil types, which are a result of the geological composition, and the vast difference in climate across the state. Generally, the west has a higher mean rainfall but poor acidic soil while the east has a lower mean rainfall but slightly more fertile soil. This results in a larger proportion of rainforest, moorland and wet sclerophyll vegetation dominating in the west and predominantly dry sclerophyll in the east. [3] [4]

Contents

Geology and soil

Surface geology of Tasmania Tasmania simple geology map.png
Surface geology of Tasmania

Tasmania, despite its size, has a very complex and diverse geology. As a geologic simplification, the western half of the state is characterised as being a more ancient fold province and the east, a younger intruded fault province. Western Tasmania contains a vast variety of ancient, deeply folded metamorphosed and non-metamorphosed rocks, namely the Mesoproterozoic quartzite, schist and phyllite. [5] Other more recent geologic signatures are scattered across the west, such as Ordovician limestone, Neoproterozoic dolomite basalt, Devonian granite (in the northwest) and Cambrian sediments. [6] The extensive folding of these rocks (particularly the quartzite) formed jagged mountain ranges and deep river valleys. Exposed to lengthy periods of erosion, the Mesoproterozoic rocks were worn down to shallow, acidic and infertile soil due to their high silica content. [6] [7] The central (central highlands) and southeastern areas are composed of much younger sedimentary rocks that have been intruded by magma, which forms sills and dykes of dolorite. [6] This area has also been impacted by volcanic activity (in the Tertiary period) that has deposited basaltic rock across the landscape. Contrasting with the generally quartzitic soil of the west, basalt is higher in nutrients and, depending on extent of weathering, fertility. [7] The weathering of eastern dolorite intrusions produces clay based soils that (with enough water), like basalt, will allow higher levels of plant production than in the west. [4] [7]

Climate

Tasmania has an incredibly varied climate that is representative of its landforms and location. Tasmania lies between southern latitudes 40–50 degrees and experiences a temperate oceanic climate. Coastal regions rarely experience maximum temperatures below 10 °C, altitudes of 450 m may have maximum temperatures below 10 °C for two months of the year and altitudes of 1000 m or greater will have maximum temperatures below 10 °C for over 6 months of the year. [8] The western region of Tasmania is impacted greatly by the Roaring Forties, strong westerly winds in the southern hemisphere, which cool the rising air mass and reduce air temperatures in this region. Due to the mountain ranges that are scattered predominantly along the west and centre of the east-west divide, the Föhn effect of descending air mass results in a warmer and drier east. [9] The bias of strong winds to the west of the state results in a distinct precipitation gradient from west to east. Western mountain ranges can receive up to 3600 mm of rainfall per year, whereas the east may only accumulate 500 mm.

Vegetation variation

Tasmania has a wide range of vegetation types for its size, which is reflective of its varied geology, topography and climate. The wetter western environments have many similar plant groups to New Zealand and South America due to the persistence of ancient Gondwanan flora that the wet climate permits. [10] The east generally has vegetation that is more characteristic of dry mainland Australia. Although not expressive of the vast mosaic of Tasmanian vegetation communities, the Tasmanian vegetation types can be broadly categorised into seven types: temperate rainforest, wet sclerophyll, alpine and sub-alpine, dry sclerophyll, coastal, moorland, sedgeland and cleared land. [4]

The West

Temperate rainforest in the Tarkine, Tasmania 2007 Tarkine walks.JPG
Temperate rainforest in the Tarkine, Tasmania 2007

To the west, temperate rainforest, wet sclerophyll and moorland/sedgeland vegetation communities are broadly dominant. Tasmanian temperate rainforests are scattered from the north to south in the west of the state with the majority occurring in the northwest (the Tarkine). [11] Species dominance changes with altitude, montane and lowland rainforest being dominated mostly by Nothofagus species, however the lowland rainforests can also be dominated by Atherosperma , Eucryphia , Phyllocladus and Anodopetalum in less fertile soils. [12] Valleys with high rainfall and low soil fertility may be dominated by conifers Lagarostrobos and Phyllocladus , respectively. There are some corridors of rainforest that can penetrate into the eastern highlands, which is at a much lower altitude. Wet sclerophyll forests are similarly scattered from north to south of western Tasmania (and in some parts of eastern Tasmania, particularly the southeast), however occur in areas of greater fire disturbance. The peppermint Eucalyptus nitida usually dominates the western wet sclerophyll forests when on poor quartzite soils. Understory species consist of Acacia species, Olearia , Bedfordia and Pomaderris . Moorland and sedgeland communities cover a considerable area (17% of the state) with the majority in the southwest of the state. They are fire dependent communities that thrive on poorly drained quartzite soils in wet environments. Thus, the vegetation is composed of pyrogenic heaths (family Ericaceae) and sedges (family Cyperaceae). [4] The dominant species in these communities are Gymnoschoenus sphaerocephalus (buttongrass) in muck peat and Lepidosperma filiforme on more skeletal soils. [13] Moorland and sedgeland vegetation is characteristic of western Tasmania, however also occurs sparsely in areas of low rainfall and poorly drained soils towards the east of the state.

Bathurst Range - Melaleuca.jpg
Buttongrass moorland Southwest Tasmania

The East

Distribution of dry sclerophyll forest in Tasmania Distribution of dry sclerophyll forest in Tasmania.jpg
Distribution of dry sclerophyll forest in Tasmania

To the east dry winds and greater sun exposure result in vegetation bearing smaller leaves and thick waxy cuticles. The dominant vegetation communities are dry sclerophyll forests and Acacia/ Collitris dry woodland. Dry sclerophyll is a huge community occupying over 25% of the state. It is much more open with only 20–25% light interception. [14] Eucalyptus species form the canopy layer and are varied across dry sclerophyll forests depending on altitude, soil type, amount of water and aspect. [4] Closer to the coast Eucalyptus globulus , Eucalyptus brookeriana and Eucalyptus regnans are dominant. [4] When merging with wet Eucalypt forests or in areas with more moisture or shade, Eucalyptus obliqua and Eucalyptus viminalis are present.

In contrast to the wet sclerophyll forests in the west of the state, dry sclerophyll lacks a tall understorey. [4] The understorey is typically composed of a sparse scatter of low trees from the genera Exocarpus , Allocasuarina , Banksia and Bursaria . The shrub layer is very diverse and contains many species from families Asteraceae (daisy family), Fabaceae (pea family), Epacridaceae (heath family) and Myrtaceae. [14]

Allocasuarina littoralis Allocasuarina littoralis.jpg
Allocasuarina littoralis

Dry woodlands are formed by either genus Allocasuarina or Callitris in habitats where it is difficult for eucalypts to thrive. On the east coast Allocasuarina verticillata woodlands inhabit shallow and rocky soils in very dry climates. Understorey is usually composed of Dodenea and Bursaria , sometimes with a prostrate shrub layer of Astroloma , Acrotriche and Lissanthe . The Allocasuarina has reduced scale leaves and photosynthetic branchlets, among other adaptations such as drooping leaves that allow it to thrive in dry habitats and infertile soils. [15] Callitris woodlands occur on the dolerite and basaltic soils of the east coast and are sensitive to fire, limiting distribution. Understorey is usually limited to a few shrubs such as Dodonaea and grasses. [16]

Both the east and west have relatively similar coastal vegetation, however due to the larger swells of the west and the depositional process of the eastern shores, the west is much rockier and the east has more beaches. [17] The west also has much more fire disturbance than the east. In the west, frontal dunes are vegetated with genera Disphyma , Carpobrotus and Acaena . Leptospermum species and Leucopogon australis are common on the upper strata and the lee faces of dunes support Banksia and Leucopogon parviflorus . [4] The dunes in the east have more grass such as Spinifex hirsutus , Poa triodioides (syn. Festuca littoralis) and other Poa species. Behind these dunes, Banksia woodland merges with dry sclerophyll E. viminalis dominated woodland. [4]

Related Research Articles

<span class="mw-page-title-main">Sclerophyll</span> Type of plant/vegetation

Sclerophyll is a type of vegetation that is adapted to long periods of dryness and heat. The plants feature hard leaves, short internodes and leaf orientation which is parallel or oblique to direct sunlight. The word comes from the Greek sklēros (hard) and phyllon (leaf). The term was coined by A.F.W. Schimper in 1898, originally as a synonym of xeromorph, but the two words were later differentiated.

<span class="mw-page-title-main">Tasmanian temperate rainforests</span> Terrestrial ecoregion in Tasmania, Australia

The Tasmanian temperate rain forests are a temperate broadleaf and mixed forests ecoregion in western Tasmania. The ecoregion is part of the Australasian realm, which includes Tasmania and Australia, New Zealand, New Guinea, New Caledonia, and adjacent islands.

<span class="mw-page-title-main">Geography of Tasmania</span>

Tasmania, the largest island of Australia, has a landmass of 68,401 km2 (26,410 sq mi) and is located directly in the pathway of the notorious "Roaring Forties" wind that encircles the globe. To its north, it is separated from mainland Australia by Bass Strait. Tasmania is the only Australian state that is not located on the Australian mainland. About 2,500 kilometres south of Tasmania island lies the George V Coast of Antarctica. Depending on which borders of the oceans are used, the island can be said to be either surrounded by the Southern Ocean, or to have the Pacific on its east and the Indian to its west. Still other definitions of the ocean boundaries would have Tasmania with the Great Australian Bight to the west, and the Tasman Sea to the east. The southernmost point on mainland Tasmania is approximately 43°38′37″S146°49′38″E at South East Cape, and the northernmost point on mainland Tasmania is approximately 40°38′26″S144°43′33″E in Woolnorth / Temdudheker near Cape Grim / Kennaook. Tasmania lies at similar latitudes to Te Waipounamu / South Island of New Zealand, and parts of Patagonia in South America, and relative to the Northern Hemisphere, it lies at similar latitudes to Hokkaido in Japan, Northeast China (Manchuria), the north Mediterranean in Europe, and the Canada-United States border.

<i>Phyllocladus aspleniifolius</i> Species of conifer

Phyllocladus aspleniifolius, commonly known as the celerytop pine, is an endemic gymnosperm of Tasmania, Australia. It is widespread and common in Tasmania, with the most abundance in the western highlands. Its ‘leaves’ appear similar to those of a celery plant, hence the common name.

<span class="mw-page-title-main">Cumberland Plain</span> Plain in Australia

The Cumberland Plain, also known as Cumberland Basin, is a relatively flat region lying to the west of Sydney CBD in New South Wales, Australia. An IBRA biogeographic region, Cumberland Basin is the preferred physiographic and geological term for the low-lying plain of the Permian-Triassic Sydney Basin found between Sydney and the Blue Mountains, and it is a structural sub-basin of the Sydney Basin.

<span class="mw-page-title-main">Geography of Western Australia</span>

Western Australia occupies nearly one third of the Australian continent. Due to the size and the isolation of the state, considerable emphasis has been made of these features; it is the second largest administrative territory in the world, after Yakutia in Russia, despite the fact that Australia is only the sixth largest country in the world by area, and no other regional administrative jurisdiction in the world occupies such a high percentage of a continental land mass.

<span class="mw-page-title-main">Eastern Australian temperate forests</span> Ecoregion in Australia

The Eastern Australian temperate forests, or the Eastern Australian temperate and subtropical forests, is a broad ecoregion of open forest on uplands starting from the east coast of New South Wales in the South Coast to southern Queensland, Australia. Although dry sclerophyll and wet sclerophyll eucalyptus forests predominate within this ecoregion, a number of distinguishable rainforest communities are present as well.

<span class="mw-page-title-main">Ecology of Tasmania</span>

The biodiversity of Tasmania is of exceptional biological and paleoecological interest. A state of Australia, it is a large South Pacific archipelago of one large main island and a range of smaller islands. The terrain includes a variety of reefs, atolls, many small islands, and a variety of topographical and edaphic regions on the largest island, all of which promote the development of unusually concentrated biodiversity. During long periods geographically and genetically isolated, it is known for its unique flora and fauna. The region's climate is oceanic.

<span class="mw-page-title-main">Tasmanian dry sclerophyll forests</span>

Dry sclerophyll forests occur throughout northern and eastern Tasmania. Characterised by the population of hard-leafed (sclerophyll) and often spiky, drought-adapted plants, dry sclerophyll forests are found in regions of where annual rainfall is below 1000mm.

<span class="mw-page-title-main">Cumberland Plain Woodland</span> Indigenous woodland community in Sydney, Australia

The Cumberland Plain Woodland, also known as Cumberland Plain Bushland and Western Sydney woodland, is a grassy woodland community found predominantly in Western Sydney, New South Wales, Australia, that comprises an open tree canopy, a groundcover with grasses and herbs, usually with layers of shrubs and/or small trees.

<span class="mw-page-title-main">Ecology of Sydney</span> Geographic aspect of Sydney, Australia

The ecology of Sydney, located in the state of New South Wales, Australia, is diverse for its size, where it would mainly feature biomes such as grassy woodlands or savannas and some sclerophyll forests, with some pockets of mallee shrublands, riparian forests, heathlands, and wetlands, in addition to small temperate and subtropical rainforest fragments.

<i>Chordifex hookeri</i> Species of flowering plant

Chordifex hookeri is commonly known as woolly buttonrush or cord-rush. It is a rush species of the genus Chordifex in the family Restionaceae. The species is endemic to Tasmania.

<span class="mw-page-title-main">Southeast Australia temperate forests</span> Terrestrial ecoregion in Australia

The Southeast Australia temperate forests is a temperate broadleaf and mixed forests ecoregion of south-eastern Australia. It includes the temperate lowland forests of southeastern Australia, at the southern end of the Great Dividing Range. Vegetation ranges from wet forests along the coast to dry forests and woodlands inland.

<span class="mw-page-title-main">Tasmanian temperate forests</span> Ecoregion in Tasmania, Australia

The Tasmanian temperate forests is a temperate broadleaf and mixed forests ecoregion in Australia. The ecoregion occupies the eastern portion of the island of Tasmania, which lies south of the Australian mainland.

<span class="mw-page-title-main">Tasmanian Central Highland forests</span> Terrestrial ecoregion in Tasmania, Australia

The Tasmanian Central Highland forests is a temperate broadleaf and mixed forests ecoregion in Australia. It covers Tasmania's Central Highlands region.

<i>Bedfordia salicina</i> Species of flowering plant

Bedfordia salicina, commonly known as Tasmanian blanketleaf, is an endemic angiosperm of Tasmania, Australia. It is widespread throughout wet sclerophyll forests, moist gullies and intermediate forests and woodlands between wet and dry sclerophyll communities. Bedfordia salicina is abundant at low elevations, on dolerite, sandstone and mudstone substrate, east of Tylers line. Alternating leaves droop down to blanket the stem, coining the species common name, blanketleaf.

<span class="mw-page-title-main">Blue Mountains and Southern Highlands Basalt Forests</span> Ecological community in New South Wales

The Blue Mountains and Southern Highlands Basalt Forests are a sclerophyll temperate forest community that stretch from the northern fringes of the Blue Mountains to the Southern Highlands in New South Wales, Australia. Featuring both wet and dry sclerophyll forests, as well as small rainforest pockets, the community features tall (30m+) and open eucalypt forests and woodlands that lie on igneous rock.

<span class="mw-page-title-main">Rainforests and vine thickets</span>

Rainforests and vine thickets are a major vegetation group in Australia. It consists of temperate to tropical rainforests, monsoon forests, and vine thickets. Rainforests and vine thickets are generally found in small pockets across the eastern and northern portions of the continent, including western Tasmania, eastern New South Wales, eastern Queensland, the northern portion of the Northern Territory, and the Kimberley Region of northeastern Western Australia.

References

  1. Tyler, Peter (1992). "A lakeland from the dreamtime: the second founders' lecture". British Phycological Journal. 27 (4): 353–368. doi: 10.1080/00071619200650301 .
  2. Tyler, Peter (December 2007). "The distinctive limnological character of south west Tasmania". Australasian Plant Conservation. 16 (3): 27–28.
  3. 1 2 Rees, Andrew.B.H; Cwynar, Les.C (2010). "A test of Tyler's Line - response of chironomids to a pH gradient in Tasmania and their potential as a proxy to infer past changes in pH". Freshwater Biology. 55 (12): 2521–2540. doi:10.1111/j.1365-2427.2010.02482.x.
  4. 1 2 3 4 5 6 7 8 9 Reid, James.B; Hill, Robert.S; Brown, Michael.J; Hovenden, Mark.J (2005). Vegetation of Tasmania. Tasmania: Australian Biological Resources Study. p. 108.
  5. Marshak, Stephen (2011). Earth: Portrait of a Planet (Fourth ed.). USA: W W NORTON & Company. p. 283.
  6. 1 2 3 Seymour, D.B.; Green, G.R.; Calver, C.R. (2007). The Geology and Mineral Deposits of Tasmania: a summary (PDF). Tasmanian Geological Survey Bulletin. Vol. 72. p. 3. ISBN   978-0-7246-4017-1.
  7. 1 2 3 Cotching, Bill (2009). Soil Health for Farming in Tasmania. Tasmania: Richmond Concepts & Print. p. 95.
  8. Langford, J (1965). "Weather and climate". Atlas of Tasmania. Tasmania: Lands and surveys. pp. 2–11.
  9. Sharples, J.J; Mills, G.A.; McRae, R.H.D.; Weber, R.O. (2009). "Fire danger anomalies associated with foehn-like winds in southeastern Australia". 18th World IMACS: 268.
  10. Hill, Robert.S (December 1990). "Sixty Million Years of Change in Tasmania's Climate and Vegetation". Tasforests: 89.
  11. Worth, J.R; Jordan, G.J; McKinnon, G.E; Vaillancourt, R.E (2009). "The major Australian cool temperate rainforest tree Nothofagus cunninghamii withstood Pleistocene glacial aridity within multiple regions: evidence from the chloroplast" (PDF). New Phytologist. 182 (2): 519–532. doi: 10.1111/j.1469-8137.2008.02761.x . PMID   19210718.
  12. Jackson, W.D (1983). "Tasmanian Rainforest Ecology". Tasmania's Rainforest's: What Future. Hobart: Australian Conservation Foundation. pp. 9–39.
  13. Jarman, S.J; Kantvilas, G; Brown, M.J (1988). "Buttongrass Moorlands in Tasmania". Tasmanian Forest Research Council Research Report No.2.
  14. 1 2 Duncan, F; Brown, M.J (1985). "Dry Sclerophyll vegetation in Tasmania". Wildlife Division Technical Report 85/1- National Parks and Wildlife Services.
  15. Crowley, G.M (1986). Thesis: Ecology of Allocasuarina littoralis. James Cook University.{{cite book}}: CS1 maint: location missing publisher (link)
  16. Parker, D.G (1999). "Structural patterns and changes in Callitris - Eucalyptus woodlands at Terrick Terrick State Park, Victoria". Victorian Grassy Ecosystems Reference Group.
  17. Colhoun, E.A (1989). "The Quaternary". The Geology and Mineral Resources of Tasmania. Brisbane: Geological Society of Australia. pp. 410–418.