Further to the article, and before you chop down trees to obtain the gold, the concentrations of gold mentioned equate to 500 trees containing enough gold to make a wedding ring [1]. Also links to CSIRO's media release [2] and the paper [3].
[1] http://www.abc.net.au/news/2013-10-23/an-gold-found-in-gum-t...
[2] http://www.csiro.au/Portals/Media/Gilding-the-gum-tree-scien...
[3] http://www.nature.com/ncomms/2013/131022/ncomms3614/full/nco...