Effects of radiation on radial growth of Scots pine in areas highly affected by the Chernobyl accident

The effects of radiation on radial growth of Scots pine (Pinus sylvestris L.) affected by the Chernobyl accident were studied at five sites with different deposition levels. The study sites were chosen along a high gradient of depositions at the distance of a few hundred meters in the forests with similar forest characteristics. Air dose rates varied at the sites from the background values up to 30 mu Gy h(-1) as of December 1, 2016. Scots pine trees exposed to sub-lethal doses of 8.6-13.2 Gy at the Red Forest site did not demonstrate deviations in formation of annual rings 30 years after the Chernobyl accident compared to trees with lower doses and control trees. Variation with time in annual rings thickness did reveal that the effect of radiation in trees growing at the sites with different contamination not detectable in 1986 and 1987. Conversely, the effects were clear observed in a later period in 1989-1991, i.e. 3-5 years after the accident. Until 2000, there were statistically significant differences in the annual rings growth rates of Scots pine trees exposed to external absorbed dose rates of 4.4-6.7 mGy h(-)(1 )as estimated for June 1, 1986 (or 19.5-30.0 mu Gy h(-1) as of December 1, 2016) compared with the trees of the other sites studied. The results comply with the conclusions from research with acute pine exposure conducted in the Kyshtym area in 1975-1984.