This paper gives an overview of the activities carried out in order to conserve the black poplar (Populus nigra L.) and European white elm (Ulmus laevis Pall.) genofond in the protected natural area 'Veliko ratno ostrvo', as well as the results after the completion of these activities. These studies proved to be necessary due to the fact that the presence of black poplar and european white elm trees in rytic forests on the territory of the Republic of Serbia in the last decades have been decreasing. In the total forests of Serbia, autochthonous poplar forests participate with only 0.5-1.0%, and the European white elm is present with less than 1% of the trees and classified in the category of rare/endangered species. Based on the research carried out in the past six years, 907 black poplar trees and 89 trees in the Veliko ratno ostrvo Island area were recorded. In populations of black poplar and European white elm there was a high degree of genetic variability at the level of morphological and molecular markers. Both populations were characterized as good candidates for in situ conservation method and accordingly, conservation areas were marked. The high presence of weeds and the absence of natural regeneration indicate the need for additional measures of ex situ conservation. For the purpose of ex situ conservation in autumn 2013th, a total of 770 European white elm seedlings originating from 14 mother trees were planted, and in the autumn of the next year, a total of 802 black poplar clones originating from 9 selected trees from this area. The executed and prescribed measures of in situ and ex situ conservation are in line with current planning documents and protection measures of this area. By implementing measures of ex situ conservation of black poplar and European white elm genofond to the Veliko ratno ostrvo Island, the area under genetic resources of these species has been increased and a new young population has been established that will contribute to the biological stability of forest ecosystems.