SCLEROPHYLL

'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.

Contents

Australian bush

History

References

Australian bush

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.
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.
^[1].
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.
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.^[2]

References

1. Maximum Plant Species Diversity in Terrestrial Communities, Parsons R. F., , , Biotropica, 1974
2. Sclerophyll forests R. Major