Title: Sizing up the reach of the willow's weep

willoiw picture[Stock Journal 15 Aug, 2011 by Nicky Phillips SMH] -- IN PARTS of China, its branches are used to ward off evil spirits, while other cultures view them as a symbol of wisdom. In Australia, however, willow trees are held in no such esteem. Here, they are classified as a weed of national significance. So pervasive is the plant that a team of CSIRO scientists has used genetic testing to track the movements of this species. Their research has found willow trees can spread their seeds and pollen a distance of up to 15 kilometres. The findings will help conservationists eradicate the introduced plant, which costs millions of dollars each year to control.

Ecologist Tara Hopley, who spent months in north-east Victoria collecting willow seeds as part of her PhD, said an average female tree would produce up to 300,000 seeds a year. But genetic testing, the first large-scale use of the technique on weeds in Australia, also showed some trees were larger producers than others, Ms Hopley, who studies at the Australian National University and CSIRO, said.An ecologist and supervisor of the CSIRO project, Andrew Young, said about 20 per cent of the trees at a site would produce up to 75 per cent of the seeds released in the area.''Everybody doesn't contribute equally,'' Dr Young, the director of the Centre for Australian National Biodiversity Research, said.

They found bigger and older trees were the main culprits. The findings will provide a valuable insight for willow control managers.''If you knock those 20 per cent down first it would be more efficient, rather than individually knocking over all of one population which takes a lot of time,'' Dr Young said.

And conservation managers would not need to use elaborate tests to know who were the largest seed producers, he said.''They can predict which trees are important simply based on canopy size and how much they flower.''

The discovery that seeds and pollen could travel such long distances also explained why typical willow-control methods, which involved removing all the trees over a stretch of a few hundred metres, would often result in trees returning three to five years later.

''The seeds can travel quite a long way beyond the scale that normal control methods are undertaken,'' Dr Young said.

Willows were introduced from Europe to stabilise river banks. But the species has become invasive in many regions, and could alter a river's ecology, Dr Young said.''They grow very aggressively, and can displace native plants,'' he said.



From http://sj.farmonline.com.au, see original source.



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Article: WeedsNews2074 (permalink)
Categories: :WeedsNews:wons, :WeedsNews:research alert, :WeedsNews:genetics
Date: 15 August 2011; 1:10:01 PM AEST

Author Name: David Low
Author ID: adminDavid