Suitability of European Aspen (Populus tremula) for Rehabilitation of Severely Polluted Areas

The rehabilitation of polluted sites requires knowledge of the responses of the keystone species to contaminated soils and to co-occurring environmental stressors, such as climate variations and herbivory. To obtain this knowledge, we monitored the performance of young European aspen (Populus tremula) trees growing naturally at sites 1.8 to 64.5 km from the Monchegorsk copper-nickel smelter in north-western Russia from 2001-2005. Copper and nickel concentrations near the smelter were 25-30 times higher than the regional background. The radial and vertical increments, leaf size, fluctuating asymmetry and insect herbivory did not change along the pollution gradient. Leaf fluctuating asymmetry positively correlated with the site-specific radial increment. Among-year variations in weather conditions did not interact with spatial patterns in aspen performance. Lack of detrimental effects of extreme pollution on any of the studied traits indicates a high tolerance of European aspen to the harsh environmental conditions of industrial barrens. This tolerance makes aspen a suitable species for rehabilitation of areas with extreme levels of soil contamination by copper, nickel and other metals. The fast-growing aspens established in heavily polluted sites may facilitate natural recovery of plant communities by sheltering dwarf shrubs and tree seedlings and by producing litter that improves soil quality.