Allocasuarina is a genus in the flowering plant family Casuarinaceae, found primarily in southern Australia. Commonly called sheoaks or she-oaks, they are notable for their long, wiry foliage, the slender green shoots somewhat resembling pine needles - although sheoaks are actually flowering plants. The leaves are reduced to minute scales, arranged spirally along the shoots. These shoots form a dense, soft mat beneath sheoaks, preventing the development of undergrowth and making sheoak woods remarkably quiet.
Another characteristic feature are the spiny "cones", about the size of an acorn but with a texture more resembling a conifer cone. However, sheoak "cones" are actually a woody fruit.
As with legumes, sheoak roots possess nodules containing symbioticnitrogen fixingbacteria; together with their highly drought adapted foliage, this enables sheoaks to thrive in very poor soil and semi-arid areas. However, sheoaks are much less bushfire tolerant than eucalypts.
Fossils of closely related species have been found dating back to the time of Gondwana.
The hard wood and rich texture makes sheoak wood popular among wood_turners. Sheoak wood is also regarded as an excellent firewood as it burns with very little ash.
Because of its ability to grow and develop extensive root systems in very poor or sandy soils, and to completely cover the ground with its "needles", it is often used to stabilise soils in erosion prone areas, or on sand dunes. Sheoak is also used as an ornamentalshrub, although for this purpose the mat of "needles" may become a nuisance and must be carefully considered.
Rainfall was high, but the associated presence of Allocasuarina indicates forest edge conditions, or perhaps disturbance by fire, which removed the canopy long enough for this genus to have a temporary advantage.
The part of this zone in which Allocasuarina was absent may represent the peak frequency of fires, which were detrimental to Allocasuarina.
A dramatic increase in rainfall and possibly soil-nutrients seems to have eliminated fire and caused the local replacement of Eucalyptus and Allocasuarina by a podocarp notophyll evergreen vine forest, including Elaeocarpaceae, Lauraceae, Myrtaceae, Podocarpaceae and, in areas of impeded drainage, palms.
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