Sclerophyll: Difference between revisions
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Most areas of the Australian continent able to support woody plants are occupied by '''sclerophyll''' communities as [[forest]]s, [[savanna]]s or [[Heath (habitat)|heathlands]]. Common plants include the [[Proteaceae]] ([[Grevillea]]s, [[Banksia]]s and [[Hakea]]s), [[Melaleuca|tea-trees]], [[Acacia]]s, [[Boronia]]s, and the [[Eucalypt]]s. |
Most areas of the Australian continent able to support woody plants are occupied by '''sclerophyll''' communities as [[forest]]s, [[savanna]]s or [[Heath (habitat)|heathlands]]. Common plants include the [[Proteaceae]] ([[Grevillea]]s, [[Banksia]]s and [[Hakea]]s), [[Melaleuca|tea-trees]], [[Acacia]]s, [[Boronia]]s, and the [[Eucalypt]]s. |
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The most common sclerophyll commmunities in Australia are [[savanna]]s dominated by grasses with an overstorey of [[Eucalypt]]s and [[Acacia]]s. Acacia (particularly [[mulga]]) [[shrubland]]s also cover extensive areas. All the dominant overtorey Acacia species and a majority of the understorey Acacias have a scleromorphic adaptation in which the leaves have been reduced to phyllodes comprised entirely of the petiole <ref>Simmons, M. 1982. Acacias of Australia. Thomas Nelson, Melbourne</ref>. Many plants of the sclerophyllous woodlands and shrublands also produce leaves unpalatable to herbivores by the inclusion of toxic and indigestible compounds in an attempt to maintain these long-lived leave. This trait is particularly noticeable in the eucalypt and Melaleuca species which possess oil glands within their leaves that produce a pungent volatile oil that makes them unpalatable to most browsers <ref>Florence, R. G. 1996. Ecology and silviculture of eucalypt forests. CSIRO Publishing, Collingwood.</ref> These traits make the majority of woody plants in these woodlands largely unpalatable to domestic livestock <ref>Mott, J. J., and J. C. Tothill. 1984. Tropical and subtropical woodlands. in G. N. Harrington and A. D. Wilson, editors. Management of Australia's Rangelands. CSIRO Publishing, Melbourne</ref>). It is therefore important from a grazing perspective that these woodlands support a more or less continuous layer of herbaceous ground cover dominated by grasses. |
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The most common sclerophyll commmunities in Australia are [[savanna]]s dominated by grasses with an overstorey of [[Eucalypt]]s and [[Acacia]]s. Acacia (particularly [[mulga]]) [[shrubland]]s also cover extensive areas. |
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Sclerophyll [[forests]] cover a much smaller area of the continent, being restricted to relatively high rainfall locations. They have a eucalyptus overstory (10 to 30 metres) with the understory also being hard-leaved. ''Dry sclerophyll'' forests are the the most common forest type on the continent, and although it may seem barren dry sclerophyll forest is highly diverse. For example, a study of sclerophyll vegetation in Seal Creek, [[Victoria (Australia)|Victoria]], found 138 species. |
Sclerophyll [[forests]] cover a much smaller area of the continent, being restricted to relatively high rainfall locations. They have a eucalyptus overstory (10 to 30 metres) with the understory also being hard-leaved. ''Dry sclerophyll'' forests are the the most common forest type on the continent, and although it may seem barren dry sclerophyll forest is highly diverse. For example, a study of sclerophyll vegetation in Seal Creek, [[Victoria (Australia)|Victoria]], found 138 species. |
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Sclerophyllous plants are all part of a specific environment and are anything but newcomers — the [[Proteaceae]] family dates back 80 million years to the late [[Cretaceous]] — but sclerophyll forests did not start becoming a major part of the Australian landscape until around 15 million years ago. By the time of European settlement, sclerophyll forest accounted for the vast bulk of the forested areas. |
Sclerophyllous plants are all part of a specific environment and are anything but newcomers — the [[Proteaceae]] family dates back 80 million years to the late [[Cretaceous]] — but sclerophyll forests did not start becoming a major part of the Australian landscape until around 15 million years ago. By the time of European settlement, sclerophyll forest accounted for the vast bulk of the forested areas. |
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Most of the wooded parts of present-day Australia have become sclerophyll dominated as a result of the extreme age of the continent combined with [[Indigenous Australians|Aboriginal]] fire use. Deep [[weathering]] of the crust over many millions of years leached chemicals out of the rock, leaving Australian soils deficient in nutrients, particularly [[phosphorus]]. Such nutrient deficient soils support non-sclerophyllous plant communities elsewhere in the world and did so over most of Australia prior to human arrival. However such deficient soils can not support the nutrient losses associated with frequent fires and are rapidly replaced with sclerophyllous species under traditional Aboriginal burning regimes. With the cessation of traditional burning non-sclerophyllous species have re-colonised sclerophyll habitat in may parts of Australia. |
Most of the wooded parts of present-day Australia have become sclerophyll dominated as a result of the extreme age of the continent combined with [[Indigenous Australians|Aboriginal]] fire use. Deep [[weathering]] of the crust over many millions of years leached chemicals out of the rock, leaving Australian soils deficient in nutrients, particularly [[phosphorus]]. Such nutrient deficient soils support non-sclerophyllous plant communities elsewhere in the world and did so over most of Australia prior to human arrival. However such deficient soils can not support the nutrient losses associated with frequent fires and are rapidly replaced with sclerophyllous species under traditional Aboriginal burning regimes. With the cessation of traditional burning non-sclerophyllous species have re-colonised sclerophyll habitat in may parts of Australia. The presence of toxic compounds combined with a low carbon : nitrogen ratio make the leaves and branches of scleromorphic species long-lived in the litter, and can lead to a large build-up of litter in woodlands <ref>White, M. E. 1986. The Greening of Gondwana. Reed Books, Frenchs Forest, Australia.</ref> <ref> <ref>Flannery, T. 1994. The future eaters. Reed New Holland, Frenchs Forest, Australia.</ref>. The toxic compounds of many species, notably Eucalyptus species, are volatile and flammable and the presence of large amounts of flammable litter, coupled with an herbaceous understorey encourages fire <ref>Burrows, W. H., J. O. Carter, J. C. Scanlan, and E. R. Anderson. 1990. Management of savannas for livestock production in north-east Australia: contrasts across the tree-grass continuum. Journal of Biogeography 17:503-512.</ref>. All the Australian sclerophyllous communities are liable to be burnt with varying frequencies and many of the woody plants of these woodlands have developed adaptations to survive and minimise the effects of fire <ref>Harrington, G. N., M. H. Friedel, K. C. Hodgkinson, and J. C. Noble. 1984. Vegetation ecology and management. in G. N. Harrington and A. D. Wilson, editors. Management of Australia's Rangelands. CSIRO Publishing, Melbourne.</ref> |
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Sclerophyllous plants generally resist dry conditions well, making them successful in areas of seasonally variable rainfall. In Australia, however, they evolved in response to the low level of phosphorus in the soil — indeed, many Australian native plants cannot tolerate higher levels of phosphorus and will die if fertilised incorrectly. The leaves are hard due to [[lignin]], which prevents wilting and allows plants to grow even when there isn't enough phosphorus for substantial new cell growth.<ref>{{cite web|url = http://www.amonline.net.au/factsheets/sclerophyll_forests.htm | title = Sclerophyll forests | author = R. Major | year = 2003 | publisher = Australian Museum | accessdate = 2005-02-14 }}</ref> |
Sclerophyllous plants generally resist dry conditions well, making them successful in areas of seasonally variable rainfall. In Australia, however, they evolved in response to the low level of phosphorus in the soil — indeed, many Australian native plants cannot tolerate higher levels of phosphorus and will die if fertilised incorrectly. The leaves are hard due to [[lignin]], which prevents wilting and allows plants to grow even when there isn't enough phosphorus for substantial new cell growth.<ref>{{cite web|url = http://www.amonline.net.au/factsheets/sclerophyll_forests.htm | title = Sclerophyll forests | author = R. Major | year = 2003 | publisher = Australian Museum | accessdate = 2005-02-14 }}</ref> |
Revision as of 22:58, 18 September 2007
![](http://upload.wikimedia.org/wikipedia/commons/thumb/8/8c/Fynbos-landscape-1.jpg/220px-Fynbos-landscape-1.jpg)
Sclerophyll is a type of vegetation that has hard leaves and short internodes (the distance between leaves along the stem). The word comes from the Greek sclero (hard) and phyllon (leaf). Sclerophyllous plants occur in all parts of the world but are most typical of Australia. They are also prominent in the Mediterranean forests, woodlands, and shrub biome that covers the Mediterranean Basin, Californian woodlands, Chilean Matorral, and the Cape Province of South Africa.
Australian bush
![](http://upload.wikimedia.org/wikipedia/commons/thumb/f/f0/Bush_Eagle-Bay_WA.jpg/220px-Bush_Eagle-Bay_WA.jpg)
Most areas of the Australian continent able to support woody plants are occupied by sclerophyll communities as forests, savannas or heathlands. Common plants include the Proteaceae (Grevilleas, Banksias and Hakeas), tea-trees, Acacias, Boronias, and the Eucalypts.
The most common sclerophyll commmunities in Australia are savannas dominated by grasses with an overstorey of Eucalypts and Acacias. Acacia (particularly mulga) shrublands also cover extensive areas. All the dominant overtorey Acacia species and a majority of the understorey Acacias have a scleromorphic adaptation in which the leaves have been reduced to phyllodes comprised entirely of the petiole [1]. Many plants of the sclerophyllous woodlands and shrublands also produce leaves unpalatable to herbivores by the inclusion of toxic and indigestible compounds in an attempt to maintain these long-lived leave. This trait is particularly noticeable in the eucalypt and Melaleuca species which possess oil glands within their leaves that produce a pungent volatile oil that makes them unpalatable to most browsers [2] These traits make the majority of woody plants in these woodlands largely unpalatable to domestic livestock [3]). It is therefore important from a grazing perspective that these woodlands support a more or less continuous layer of herbaceous ground cover dominated by grasses.
Sclerophyll forests cover a much smaller area of the continent, being restricted to relatively high rainfall locations. They have a eucalyptus overstory (10 to 30 metres) with the understory also being hard-leaved. Dry sclerophyll forests are the the most common forest type on the continent, and although it may seem barren dry sclerophyll forest is highly diverse. For example, a study of sclerophyll vegetation in Seal Creek, Victoria, found 138 species. [4].
Even less extensive are wet sclerophyll forests. They have a taller eucalyptus overstory than dry sclerophyll forests, 30 metres or more (typically Mountain Ash, Alpine Ash, Messmate Stringybark or Manna Gum), and a soft-leaved, fairly open understory (tree ferns are common). They require ample rainfall — at least 1000mm (40 inches).
History
Sclerophyllous plants are all part of a specific environment and are anything but newcomers — the Proteaceae family dates back 80 million years to the late Cretaceous — but sclerophyll forests did not start becoming a major part of the Australian landscape until around 15 million years ago. By the time of European settlement, sclerophyll forest accounted for the vast bulk of the forested areas.
Most of the wooded parts of present-day Australia have become sclerophyll dominated as a result of the extreme age of the continent combined with Aboriginal fire use. Deep weathering of the crust over many millions of years leached chemicals out of the rock, leaving Australian soils deficient in nutrients, particularly phosphorus. Such nutrient deficient soils support non-sclerophyllous plant communities elsewhere in the world and did so over most of Australia prior to human arrival. However such deficient soils can not support the nutrient losses associated with frequent fires and are rapidly replaced with sclerophyllous species under traditional Aboriginal burning regimes. With the cessation of traditional burning non-sclerophyllous species have re-colonised sclerophyll habitat in may parts of Australia. The presence of toxic compounds combined with a low carbon : nitrogen ratio make the leaves and branches of scleromorphic species long-lived in the litter, and can lead to a large build-up of litter in woodlands [5] Cite error: A <ref>
tag is missing the closing </ref>
(see the help page).. The toxic compounds of many species, notably Eucalyptus species, are volatile and flammable and the presence of large amounts of flammable litter, coupled with an herbaceous understorey encourages fire [6]. All the Australian sclerophyllous communities are liable to be burnt with varying frequencies and many of the woody plants of these woodlands have developed adaptations to survive and minimise the effects of fire [7]
Sclerophyllous plants generally resist dry conditions well, making them successful in areas of seasonally variable rainfall. In Australia, however, they evolved in response to the low level of phosphorus in the soil — indeed, many Australian native plants cannot tolerate higher levels of phosphorus and will die if fertilised incorrectly. The leaves are hard due to lignin, which prevents wilting and allows plants to grow even when there isn't enough phosphorus for substantial new cell growth.[8]
References
- ^ Simmons, M. 1982. Acacias of Australia. Thomas Nelson, Melbourne
- ^ Florence, R. G. 1996. Ecology and silviculture of eucalypt forests. CSIRO Publishing, Collingwood.
- ^ Mott, J. J., and J. C. Tothill. 1984. Tropical and subtropical woodlands. in G. N. Harrington and A. D. Wilson, editors. Management of Australia's Rangelands. CSIRO Publishing, Melbourne
- ^ Parsons R. F. (1974). "Maximum Plant Species Diversity in Terrestrial Communities". Biotropica. 6 (3).
{{cite journal}}
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ignored (|author=
suggested) (help) - ^ White, M. E. 1986. The Greening of Gondwana. Reed Books, Frenchs Forest, Australia.
- ^ Burrows, W. H., J. O. Carter, J. C. Scanlan, and E. R. Anderson. 1990. Management of savannas for livestock production in north-east Australia: contrasts across the tree-grass continuum. Journal of Biogeography 17:503-512.
- ^ Harrington, G. N., M. H. Friedel, K. C. Hodgkinson, and J. C. Noble. 1984. Vegetation ecology and management. in G. N. Harrington and A. D. Wilson, editors. Management of Australia's Rangelands. CSIRO Publishing, Melbourne.
- ^ R. Major (2003). "Sclerophyll forests". Australian Museum. Retrieved 2005-02-14.