University of New England researchers say that maintaining shade is the key to loosening the stranglehold of lantana on Australia's east coast.
Lantana is believed to infest four million hectares of coastal land in Australia from North Queensland to south of Sydney.
Lantana Camara was imported from Brazil as a garden plant and was first recorded in Australia at Adelaide's Botanic Gardens in 1841. A prolific seed producer, lantana was quickly spread by birds carrying the seeds in their droppings. The weed grows in thickets in tropical and sub-tropical zones around the world, with all attempts at biological controls so far proving fruitless.
After numerous studies at sites in the Oxley Wild Rivers National Park and near Lake Macquarie, PhD student in the Division of Ecosystem Management, Chris Gentle and Vice-Dean in the School of Rural Science and Natural Resources Dr John Duggin have found that the maintenance of shade from tall trees is the most important factor in preventing the establishment of lantana.
Dr Duggin said that lantana was particularly damaging to Australia because it was a menace to both farmers and the natural environment.
"Lantana releases a chemical which inhibits the growth of native species, and can quickly colonise and dominate a site where the overstorey has been disturbed," Dr Duggin said. "This reduces biodiversity and ability of native systems to re-establish themselves.
"We found that disturbances to the canopy leading to increases in the amount of light reaching the forest floor was the most significant cause of establishment - more significant than the fertility of the soil and soil disturbance. The removal of the understorey and shrub layer also increased the rate of lantana establishment, but not as significantly as the removal of the canopy."
Dr Duggin said this caused a dilemma for forest managers because controlled burning off, which reduces the risk of catastrophic fire and the destruction of the forest canopy, might lead to moderate lantana infestation.
"The population of lantana just explodes after high-intensity fires," Dr Duggin said. "In terms of management, you need to protect the overstorey of the forest by avoiding these wildfires. But in trying to avoid wildfires by burning off fuel loads, you need to make sure you don't scorch the shrubs in the understorey. There is a very fine line to tread in preventing wildfires with low-intensity fires."
He said that to further control lantana, burning off should be avoided in "ecotones" or the transition areas between different eucalypt forests, and cattle should be kept away from forest margins.
Dr Duggin said this research indicated that the challenge in trying to control lantana may be to find a native plant that can compete with it and provide a shade canopy to stop it from spreading.
Media contact: Gavin Atkins, Publicity Office, UNE, Armidale, (02) 6773 3570
This page is maintained and updated fortnightly by
Jo
Philp Publicity Office,
University of New England, Armidale NSW 2351, Australia, phone (02)
6773 2103
Last updated 3 July, 1998