Plants of the Deserts
Australian deserts are not vast areas of sand dunes like pictures of the vast sandy deserts of other countries.
The average annual rainfall for Australian deserts is about 250mm. However, the evaporation rate is also very high so that small showers are not very effective for plant growth.
Plants have adapted to long dry spells by growing as individuals, with bare spaces between plants. These might fill with small, fast-growing plant species after rain but these finish their life cycle quickly, then dry out and leave the patches until the next rain. The tougher, established plants get refreshed, flower and set seed so as to expand their territory.
The deserts are usually covered with shrubs and grasses that can cope with long dry periods. However, there are rocky outcrops that do hold water in cracks and at depth. Larger plants have roots that can access this stored moisture and so Eucalypts (mostly Corymbias), Casuarina and Acacias are often found here. Watercourses that collect the runoff from heavy rains also often have trees and large shrubs accessing the water stored underground.
The other big influence on plants in the Australian deserts is the influence of fire. Lightning strikes are the most common source of fires and these leave scars that can be seen for years after. Fires remove a lot of vegetation from the country but many plants have adapted to this regime. Hard seed pods (eg Hakea) or hard tough seed coats (pea-flowered plants) can withstand the heat of the fire and then become more able to germinate with following rains.
The desert plant populations are dynamic. Annual plants flourish after a fire as there are more spaces to occupy. However, the newly germinated perennial plant seedlings continue to grow and repopulate the country once again.
Many areas of the Australian deserts do not get visited by botanists to survey the diversity of plants in these remote areas. Watercourses and springs become reservoirs of plants that are not seen widely elsewhere. The Desert Discovery projects visit these remote areas surveying for plants to better understand their population size and distribution. Species new to science are always there to be found.
