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ŠUMARSKI LIST 7-8/2021 str. 25     <-- 25 -->        PDF

Comparison of age sequences of 137Cs activity in shoots of silver fir with those in silver fir needles (Figure 2) for individual height between two years (2003 and 2004), also using non-parametric test for related samples (“Wilcoxon matched pairs test”), shows that the 2004 values are statistically significantly (p = 0.05) higher than in those in 2003, at all three heights. This result, very similar to that of the shoots, can be equally interpreted (as a result of increasing the rate of photosynthesis and metabolism levels during vegetation period, leading to a temporary accumulation of 137Cs in the needles). The regularity is shown even at a height of 25 m (not in the shoot case).
Comparison of age sequences of 137Cs activity in silver fir shoots with those in needles (Figures 2 and 3) was conducted separately for each height and year, also using the non-parametric test for related samples. The obtained results show that for the same year the values in the shoots are always statistically significantly (p = 0.05) higher than those in the needles of the same age at all three heights. This result can be associated with a smaller amount of flow in the peripheral tissues of the tree conduction system, which results in smaller amounts of 137Cs entering/appearing in these tissues. Figure 3 shows a transparent distribution of 137Cs through shoots and silver fir tree needles of different ages, separately for each height (8, 16 and 25 m). This figure shows what has already been pointed out: 1) higher values in 2004 during the vegetation period compared to those in the winter period of 2003 (at all heights, both in shoots and needles) and 2) generally higher values in shoots relative to those in needles (for both years, at all tree heights). Additionally, in this picture (looking only at the medians of age series related to the same tissue type in the same year connected by lines), it can qualitatively determine an overall increase in 137Cs activity in shoots and needles of the tree heights (regardless of age). Although due to the small number of sample point (three heights) it is not possible to test this increase for significantly positive correlation, it is appropriate to point out that such positive correlation is consistent with other results presented. That is, when viewed within the same type of tissue, the largest activity of 137Cs can be expected in areas of greatest physiological activities, which, if we talk about the shoots and needles, should be higher in the tissue sample from higher stem (having