Sclerophyll
Encyclopedia
Leaf
A leaf is an organ of a vascular plant, as defined in botanical terms, and in particular in plant morphology. Foliage is a mass noun that refers to leaves as a feature of plants....
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 many parts of the world, but are most typical in the chaparral
Chaparral
Chaparral is a shrubland or heathland plant community found primarily in the U.S. state of California and in the northern portion of the Baja California peninsula, Mexico...
biome
Biome
Biomes are climatically and geographically defined as similar climatic conditions on the Earth, such as communities of plants, animals, and soil organisms, and are often referred to as ecosystems. Some parts of the earth have more or less the same kind of abiotic and biotic factors spread over a...
s. They are prominent throughout western (Perth
Perth, Western Australia
Perth is the capital and largest city of the Australian state of Western Australia and the fourth most populous city in Australia. The Perth metropolitan area has an estimated population of almost 1,700,000....
), eastern (Sydney
Sydney
Sydney is the most populous city in Australia and the state capital of New South Wales. Sydney is located on Australia's south-east coast of the Tasman Sea. As of June 2010, the greater metropolitan area had an approximate population of 4.6 million people...
) and southern (Adelaide
Adelaide
Adelaide is the capital city of South Australia and the fifth-largest city in Australia. Adelaide has an estimated population of more than 1.2 million...
) parts of Australia
Flora of Australia
The flora of Australia comprises a vast assemblage of plant species estimated to over 20,000 vascular and 14,000 non-vascular plants, 250,000 species of fungi and over 3,000 lichens...
, in the Mediterranean forests, woodlands, and scrub
Mediterranean forests, woodlands, and scrub
Mediterranean forests, woodlands, and scrub biome, defined by the World Wildlife Fund, characterized by dry summers and rainy winters. Summers are typically hot in low-lying inland locations but can be cool near some seas, as near San Francisco, which have a sea of cool waters...
biome
Biome
Biomes are climatically and geographically defined as similar climatic conditions on the Earth, such as communities of plants, animals, and soil organisms, and are often referred to as ecosystems. Some parts of the earth have more or less the same kind of abiotic and biotic factors spread over a...
that cover the Mediterranean Basin
Mediterranean Basin
In biogeography, the Mediterranean Basin refers to the lands around the Mediterranean Sea that have a Mediterranean climate, with mild, rainy winters and hot, dry summers, which supports characteristic Mediterranean forests, woodlands, and scrub vegetation...
, Californian woodlands
California chaparral and woodlands
The California chaparral and woodlands is a terrestrial ecoregion of lower northern, central, and southern California and northwestern Baja California , located on the west coast of North America...
, Chilean Matorral
Chilean Matorral
The Chilean Matorral is a terrestrial ecoregion of central Chile, located on the west coast of South America. It is in the Mediterranean forests, woodlands, and scrub biome, part of the Neotropic ecozone....
, and the Cape Province
Cape Province
The Province of the Cape of Good Hope was a province in the Union of South Africa and subsequently the Republic of South Africa...
of South Africa
South Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...
.
Australian bush
Forest
A forest, also referred to as a wood or the woods, is an area with a high density of trees. As with cities, depending where you are in the world, what is considered a forest may vary significantly in size and have various classification according to how and what of the forest is composed...
s, savanna
Savanna
A savanna, or savannah, is a grassland ecosystem characterized by the trees being sufficiently small or widely spaced so that the canopy does not close. The open canopy allows sufficient light to reach the ground to support an unbroken herbaceous layer consisting primarily of C4 grasses.Some...
s or heathlands
Heath (habitat)
A heath or heathland is a dwarf-shrub habitat found on mainly low quality acidic soils, characterised by open, low growing woody vegetation, often dominated by plants of the Ericaceae. There are some clear differences between heath and moorland...
. Common plants include the Proteaceae
Proteaceae
Proteaceae is a family of flowering plants distributed in the Southern Hemisphere. The family comprises about 80 genera with about 1600 species. Together with the Platanaceae and Nelumbonaceae they make up the order Proteales. Well known genera include Protea, Banksia, Embothrium, Grevillea,...
(Grevillea
Grevillea
Grevillea is a diverse genus of about 360 species of evergreen flowering plants in the protea family Proteaceae, native to Australia, New Guinea, New Caledonia, and Sulawesi. It was named in honour of Charles Francis Greville. The species range from prostrate shrubs less than 0.5 m tall to trees...
s, Banksia
Banksia
Banksia is a genus of around 170 species in the plant family Proteaceae. These Australian wildflowers and popular garden plants are easily recognised by their characteristic flower spikes and fruiting "cones" and heads. When it comes to size, banksias range from prostrate woody shrubs to trees up...
s and Hakea
Hakea
Hakea is a genus of 149 species of shrubs and small trees in the Proteaceae, native to Australia. They are found throughout the country, with the highest species diversity being found in the south west of Western Australia....
s), tea-trees
Melaleuca
Melaleuca is a genus of plants in the myrtle family Myrtaceae known for its natural soothing and cleansing properties. There are well over 200 recognised species, most of which are endemic to Australia...
, Acacia
Acacia
Acacia is a genus of shrubs and trees belonging to the subfamily Mimosoideae of the family Fabaceae, first described in Africa by the Swedish botanist Carl Linnaeus in 1773. Many non-Australian species tend to be thorny, whereas the majority of Australian acacias are not...
s, Boronias, and the Eucalypt
Eucalypt
Eucalypts are woody plants belonging to three closely related genera:Eucalyptus, Corymbia and Angophora.In 1995 new evidence, largely genetic, indicated that some prominent Eucalyptus species were actually more closely related to Angophora than to the other eucalypts; they were split off into the...
s.
The most common sclerophyll communities in Australia are savanna
Savanna
A savanna, or savannah, is a grassland ecosystem characterized by the trees being sufficiently small or widely spaced so that the canopy does not close. The open canopy allows sufficient light to reach the ground to support an unbroken herbaceous layer consisting primarily of C4 grasses.Some...
s dominated by grasses with an overstorey of Eucalypt
Eucalypt
Eucalypts are woody plants belonging to three closely related genera:Eucalyptus, Corymbia and Angophora.In 1995 new evidence, largely genetic, indicated that some prominent Eucalyptus species were actually more closely related to Angophora than to the other eucalypts; they were split off into the...
s and Acacia
Acacia
Acacia is a genus of shrubs and trees belonging to the subfamily Mimosoideae of the family Fabaceae, first described in Africa by the Swedish botanist Carl Linnaeus in 1773. Many non-Australian species tend to be thorny, whereas the majority of Australian acacias are not...
s. Acacia (particularly mulga
Mulga
Acacia aneura, commonly known as Mulga or True Mulga, is a shrub or small tree native to arid outback Australia of areas such as the Western Australian Mulga shrublands.-Description:...
) shrubland
Shrubland
Shrubland, scrubland, scrub or brush is a plant community characterized by vegetation dominated by shrubs, often also including grasses, herbs, and geophytes. Shrubland may either occur naturally or be the result of human activity...
s also cover extensive areas. All the dominant overstorey Acacia species and a majority of the understorey Acacias have a scleromorphic adaptation in which the leaves have been reduced to phyllodes consisting entirely of the petiole
Petiole (botany)
In botany, the petiole is the stalk attaching the leaf blade to the stem. The petiole usually has the same internal structure as the stem. Outgrowths appearing on each side of the petiole are called stipules. Leaves lacking a petiole are called sessile, or clasping when they partly surround the...
. 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 leaves. 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. These traits make the majority of woody plants in these woodlands largely unpalatable to domestic livestock. 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 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
Victoria (Australia)
Victoria is the second most populous state in Australia. Geographically the smallest mainland state, Victoria is bordered by New South Wales, South Australia, and Tasmania on Boundary Islet to the north, west and south respectively....
, found 138 species.
Even less extensive are wet sclerophyll forests. They have a taller eucalyptus overstory than dry sclerophyll forests, 30 metres or more (typically Mountain Ash
Eucalyptus regnans
Eucalyptus regnans, known variously by the common names Mountain Ash, Victorian Ash, Swamp Gum, Tasmanian Oak or Stringy Gum, is a species of Eucalyptus native to southeastern Australia, in Tasmania and Victoria...
, Alpine Ash
Eucalyptus delegatensis
Eucalyptus delegatensis, commonly known as Alpine Ash or Gum-topped stringybark or White-top, is a sub-alpine or temperate tree of southeastern Australia. A straight, grey-trunked tree, it reaches heights of over 90 metres in suitable conditions. The tallest currently known specimen is located in...
, Messmate Stringybark or Manna Gum
Manna Gum
Eucalyptus viminalis, Manna Gum, also known as White Gum, Ribbon Gum or Viminalis is an Australian eucalypt.It is a straight erect tree, often around 40 metres tall, with rough bark on the trunk and base of larger branches, its upper bark peels away in long "ribbons" which can collect on the...
), and a soft-leaved, fairly dense 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. 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
Indigenous Australians
Indigenous Australians are the original inhabitants of the Australian continent and nearby islands. The Aboriginal Indigenous Australians migrated from the Indian continent around 75,000 to 100,000 years ago....
fire use. Deep weathering
Weathering
Weathering is the breaking down of rocks, soils and minerals as well as artificial materials through contact with the Earth's atmosphere, biota and waters...
of the crust over many millions of years leached chemicals out of the rock, leaving Australian soils deficient in nutrients, particularly phosphorus
Phosphorus
Phosphorus is the chemical element that has the symbol P and atomic number 15. A multivalent nonmetal of the nitrogen group, phosphorus as a mineral is almost always present in its maximally oxidized state, as inorganic phosphate rocks...
. 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 cannot 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 many 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. 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. 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.
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
Lignin
Lignin or lignen is a complex chemical compound most commonly derived from wood, and an integral part of the secondary cell walls of plants and some algae. The term was introduced in 1819 by de Candolle and is derived from the Latin word lignum, meaning wood...
, which prevents wilting and allows plants to grow even when there isn't enough phosphorus for substantial new cell growth.
See also
- Mediterranean forests, woodlands, and scrubMediterranean forests, woodlands, and scrubMediterranean forests, woodlands, and scrub biome, defined by the World Wildlife Fund, characterized by dry summers and rainy winters. Summers are typically hot in low-lying inland locations but can be cool near some seas, as near San Francisco, which have a sea of cool waters...
- ChaparralChaparralChaparral is a shrubland or heathland plant community found primarily in the U.S. state of California and in the northern portion of the Baja California peninsula, Mexico...
- California chaparral and woodlandsCalifornia chaparral and woodlandsThe California chaparral and woodlands is a terrestrial ecoregion of lower northern, central, and southern California and northwestern Baja California , located on the west coast of North America...
- Chilean MatorralChilean MatorralThe Chilean Matorral is a terrestrial ecoregion of central Chile, located on the west coast of South America. It is in the Mediterranean forests, woodlands, and scrub biome, part of the Neotropic ecozone....
- FynbosFynbosFynbos is the natural shrubland or heathland vegetation occurring in a small belt of the Western Cape of South Africa, mainly in winter rainfall coastal and mountainous areas with a Mediterranean climate...
- GarrigueGarrigueGarrigue or phrygana is a type of low, soft-leaved scrubland ecoregion and plant community in the Mediterranean forests, woodlands, and scrub biome. It is found on limestone soils around the Mediterranean Basin, generally near the seacoast, where the climate is ameliorated, but where annual summer...
- Maquis shrublandMaquis shrublandthumb|220px|Low Maquis in Corsica.220px|thumb|High macchia in Sardinia.Maquis or macchia is a shrubland biome in the Mediterranean region, typically consisting of densely growing evergreen shrubs such as holm oak, tree heath, strawberry tree, sage, juniper, buckthorn, spurge olive and myrtle...
- MatorralMatorralMatorral is a Spanish word, along with tomillares, for shrubland, thicket or bushes. It is used in naming and describing a Mediterranean climate ecosystem in Southern Europe.-Mediterranean region:...