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ŠUMARSKI LIST 7-8/2021 str. 29     <-- 29 -->        PDF

concentration during the vegetation period decreases due to migration of 137Cs in physiologically most active tissues (shoots and needles).
Comparison of 137Cs activities in different tissues of silver fir – Usporedba aktivnosti 137Cs u različitim tkivima obične jele
Figure 11 shows the distribution of 137Cs activity in rings, shoots, needles of silver fir tissues (the results from the youngest tissue samples generated in the sampling year for tissue types for which is possible to determine the age) for 2003 (winter sample), 2004 (vegetation season sample) and values from the respective samples collected in 2017 and recalculated (eliminated impact of radioactive decay) on July 1, 2003.In Figure 11, it can be primarily observed that in tissues (peak shoots, needles) from samples collected in 2004, values are significantly higher than in previously collected samples, which directly proves the presence of 137Cs redistribution in tree tissues over time (given that the absence of such redistribution over time should decrease the value due to radioactive decay). The existence of redistribution is confirmed by the results in the tissues in which the 137Cs activity was higher in 2003, because these differences (up to three times higher values for samples of bark and cambium near the soil, compared to 2004) were significantly higher than those that would result due only to radioactive decay during less than a year. Furthermore, it can be seen that in the winter period samples higher values of 137Cs were recorded in samples of dead bark, live bark with the cambium, and the young rings and roots, while in the growing season samples higher values were recorded in peak shoots and needles samples. It can be observed that for all tissue types the recalculated values from the samples collected in 2017 are