Heavy metal adaptation of mountain birch in industrial barrens

The nickel-copper smelters in Monchegorsk and Nikel, NW Russia, are among the biggest point polluters in Europe. In Monchegorsk, 70 years of SO₂, Ni and Cu emissions have destroyed coniferous forests up to 15 km from the smelter. Despite seed production, there is no mountain birch recruitment in industrial barrens due to low germination and 100% seedling mortality. Consequently, persistence of birch populations in the barrens may be transient, with planting of birch seedlings necessary to avoid local extinction. Genetic adaptation of long lived trees to pollutants has been rarely documented. However, the few mountain birches that survived near Monchegorsk and Nikel have gone through extremely strong survival selection, making the formation of heavy metal adaptations in the barren areas possible. Here I report the preliminary results of three experiments, aimed at studying whether seedlings originating from industrial barrens have heightened heavy metal tolerance, and whether this adaptation has resulted in a trade-off with lowered growth and competitive ability in pristine environments. In a five year experiment I planted birch seedlings from polluted (P) and control (C) origins outdoors to test their response to wind and herbivore stress. In two one-year greenhouse experiments I tested their response to artificial heavy metal addition and drought. P seedlings experienced less herbivory than C seedlings. P seedlings outperformed C seedlings in the heavy metal treatment, but C seedlings were superior in unpolluted conditions. Nickel uptake by P seedlings was lower than C seedlings. These results indicate that long lasting emissions have resulted in the evolution of heavy metal tolerance in birch populations. With the exception of lessened herbivory on P seedlings, the adaptation carries a trade-off with decreased performance in unpolluted conditions. These findings could be beneficial for possible future restoration efforts, as local seedlings could be used for better growth and survival.