Long-term effect of fertilization on ¹³⁷Cs concentration in Scots pine needles

¹ Finnish Forest Research Institute, Parkano Unit, Kaironiementie 15, FI-39700 Parkano, Finland
² Radiation and Nuclear Safety Authority, P.O. Box 14, FI-00881 Helsinki, Finland

Abstract

Long-term observations on the effects of a fertilization treatment on ¹³⁷Cs concentrations in forest vegetation are scarce. Needles of Scots pine were used as biological indicators of radionuclide uptake of trees. The fertilization experiments are located in western Finland in an area where radioactive contamination from the Chernobyl accident in 1986 was relatively high (22–75 kBq m⁻²) compared to other parts of Finland. Fertilization treatments included different combinations of major nutrients, i.e. nitrogen, phosphorus, potassium and calcium. Needle ¹³⁷Cs concentrations of Scots pine were analyzed during 1991–2006. The effect of fertilization on ¹³⁷Cs concentration was tested 5 to 20 years after radioactive contamination from the Chernobyl accident in 1986. Fertilization clearly decreased ¹³⁷Cs concentration in Scots pine needles 1–21 growing seasons after application. Single K fertilization decreased significantly ¹³⁷Cs concentration 21 growing seasons after radioactive deposition on a drained mire. Mineral nutrients (application of commercial fertilizer or wood ash) can well be recommended for remediation of forests contaminated by accidental radionuclide deposition. The site conditions need to be taken into account in planning of remediation.