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Recent publications

Workreport 2017-28



Results of Forest Monitoring on Olkiluoto Island in 2016


Aro, L., Lindroos, A-J., Rautio, P., Ryynänen, A., Korpela, L., Viherä-Aarnio, A., Salemaa M.



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The forest investigations form a part of the monitoring programme being carried out on the Olkiluoto Island nuclear waste repository site under the management of Posiva Oy. This report presents results from studies performed on bulk deposition and forest intensive monitoring plots (MRK and FIP plots) in 2016, and results from the soil, ground vegetation and tree foliage surveys which were repeated on the FET sampling plot network since the first round in 2005.

In general, the level of precipitation was lower in 2016 than in 2015. The NH4-N deposition clearly increased again on the bulk deposition plot MRK13. The increase in NH4-N deposition was considered to probably be due to the construction activities in that area. The highest annual NH4-N deposition in stand throughfall during the whole monitoring period 2004-2016 was also measured on the black alder plot in 2016. The NO3-N deposition values decreased in 2015-2016. The soil solution quality in 2016 was quite comparable to that in earlier years. The Sr concentration in soil solution in 2016 was much higher than the values in bulk deposition and stand throughfall, and there was also clear variation between the plots. The variation is probably caused by natural factors, such as the release of Sr from soil minerals due to weathering. There were no essential changes in the properties of the humus layer between 2005 and 2015. However, total concentration of Al and Fe increased clearly in rocky and Fe also in heath forests.

Annual total litterfall production (232–431 gdw/m2 without larger branches) was lower in 2015 than in 2014. Annual variations recorded on Olkiluoto Island are due to natural reasons. High Al and Fe concentrations were found in the remaining litter, and were most likely due to soil dust.

There were no dramatic changes in vegetation cover on the FIP plots during the last 5-year-long monitoring period. The mean height of understorey vegetation varied from 10 cm (forested and drained mires) to 32.4 cm (grove forests) on the FET plots. Total aboveground biomass of understorey vegetation by FET plots varied from 229 to 2055 kg/ha. A clear decreasing trend was detected in B, Cu and Mn concentrations of different plant groups from 2005 to 2015. Concentrations of Al and Fe and heavy metals (Ni, Cd, Cr and Pb) decreased also more or less in all plant groups in all biotopes. Concentrations of key elements (Ag, Cl, Cs, I, Mo, Nb, Ni, Pb, Pd, Se, Sn ja Sr) by plant species and species groups for each biotope are presented in this report.

The spruces in the heath forest were classified as moderately defoliated and the pines both in the mire and in the rocky forest as slightly defoliated. Nutrition of tree species was at a satisfactory level, and there was not a remarkable change in tree nutrition between 2005 and 2015. Key elements in trees are also presented in this report.

No harmful effects of human activities on the forest condition were observed in the nature conservation area.


Biomass, bulk deposition, forest ecosystems, key elements, litterfall production, nutrition, soil solution chemistry, stand throughfall, understorey vegetation


WR 2017-28_web (pdf) (37.5 MB)
Appendix 6_web (xls) (100 KB)
Appendix 7_web (xlsx) (166 KB)
Appendix 9_web (xlsx) (63.4 KB)
Appendix 10_web (xls) (61.5 KB)


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