The survey was carried out on fly ash landfill Prapretno in Trbovlje, where nine tree species were planted. The purpose of diploma paper is to determine which species will successfully adapt to a given situation which prevails in such degraded areas. From 2001 to 2008 the parameters (such as the growth of trees in height, the development of roots, increment growth of trees) and ecological conditions (which at that time prevailed in the landfill area) wereanalyzed. The reasons for poor thriving of some tree species were not discovered. However, the impact on biodiversity due to the inclusion of new species in the impoverished eco system was examined in the paper. The results showed that the growth of the trees is affected by the combination of abiotic and biotic stress factors. Only four of nine tree species (black hornbeam, black alder, birch, trembling poplar) have successfully adapted and they will be used for the afforestation of the landfill.