Most forest tree species return between 50% and 80% of their annual nutrient uptake to the soil but aspen retains over half of its uptake and is particularly efficient at retaining calcium, sulphur and zinc, thereby limiting loss by leaching and improving soil fertility. The ability to absorb zinc and other trace elements allows aspen to survive on the spoil heaps of mining operations and assist in the reclamation of post-mining landscapes, for example lignite mines in Germany, opencast oil shale quarries in Estonia and many sites laid bare by coal spoil, heavy metal and smelter pollution in North America. In North America aspen has been found to naturally colonise large areas of polluted industrial sites and to tolerate soils with low pH, low fertility and heavy metal content. The ability to sucker is also an advantage for rapidly extending across new areas of bare ground. Some aspen forests have developed diverse habitats and thrived for over 70 years on mine tailings near smelter sites. Aspen has a mutualistic relationship with a small group of mycorrhizal fungi from the genera Laccaria, Inocybe, Paxillus and Scleroderma which help to increase phosphorus uptake and ameliorate soil conditions and may be essential for aspen to establish in contaminated soils. Beneficial mycorrihiza such as Laccaria laccata have been recorded with aspen and other Populus species on uranium tailings and the spoil heaps of old arsenic mines in England.

Extract from “Ecology, Conservation and Management of Aspen, A Literature Review, Neil Mackenzie, Scottish Native Woods, 2010