alder and common birch, the initial aggregated pattern was maintained over the examined 14-year period of the forest succession. Bivariate analysis showed that the most common interspecific association between pairs of tree species was spatial segregation (pine vs. alder, alder vs. birch and oak vs. birch) followed by spatial independence (pine vs. oak and oak vs. alder). The positive association was stated only for pine and birch and only for certain spatial scales (> 5 m). Simultaneously, at small distances they showed reciprocal repulsion. Changes in spatial relationships between tree species were negligible over 14-year period of forest succession. Our results confirmed the density-dependent mortality process in the uneven-aged Scots pine-dominated forest over 14-year period of forest development. Our study showed that spatial interactions between individuals along with speciesspecific ecological requirements should be incorporated into realistic models of forest development, helping to manage the forest ecosystems toward their greater structural complexity.

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Wzrost szczepów lipy drobnolistnej (Tilia cordata Mill.) na plantacji nasiennej w Nadleśnictwie Susz

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The radionuclide uptake by crops strongly depends on soil fertility and biological features of plants. The sou" reac tion, humus content, calcium, magnesium and potassium status are the most important soil properties, which determine ra dionuclide transfer to plants. The evaluation of separate soil property influence on the radionuclide uptake by plants is a com plex task. It was found that' "Cs and *Sr transfer to plants are reduced by a factor 1.5 to 3.0 as a result ctf the change of sodpodzolic soil reaction from acid (pHua 4,5-5,0) to neutral range (pHua 6,5-7,0), of humus content from 1.0 up to 3.5% and of exchangeable potassium content from tow (< 80 mg ICjCVkg of soil) up to high range (200-350 mg/kg). The lowest transfer ring of radionuclides to plants was observed at the optimal range of soil fertility parameters. On the basis of compilation and processing of experimental data the transfer factors of l37 Cs and '"Sr from soil to crop had been differentiated according to sail fertility parameters tar prediction of radionuclide accumulation in plant production. The soil fertility has to be improved in such a way that proposes the significant increase of crop yields with decreasing of the risk of people internal irradiation.

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