Conservation of genetic diversity of forest tree species represents the foundation for sustainable forest management and preservation of natural structure of forest stands in the Republic of Moldova. Diversity of geographical regions in the Republic of Moldova has generated various ecological conditions and thus diverse forest communities which are directly affected by habitat degradation, various anthropogenic effects like pollution of air and water, excessive use of certain more valuable species of forest trees, for example oaks, and by the increasing impact of global climatic changes. Study of the particularities of descendent growth, quality of trunks, as well as their resistance to pests, diseases, and abiotic stress in geographical and environmental cultures, is one of the most actual problems in the forest seed zoning based on population genetics. The interaction of inherited characteristics and environmental conditions determine the resistance and productivity of descendents from various environmental and geographical origins. Differences in productivity due these factors might achieve II-III growth classes. In researches carried out by some scientists, it has been shown that the properties of climatic types and ecotypes are inherited and expressed in the second and even in 3-rd generation. Moreover, in geographical cultures that influence descendants’ growth, the strategies of forest restoration and breeding ultimately depend on the relationships between the inherited properties and environmental factors. Despite the fact that the seed zoning based on the population-genetic basis is an important methodological approach for maintaining the productivity and sustainability of plantations, the intensification of global warming tendency in recent years, may exceed the adaptive capacity of woody plants in population. Manifestation during long time of temperatures above the average by only 1-2°C will cause the necessity to increase the adaptive capacity of individuals in plantations, which in turn can lead to regressive succession process and modification of distribution of oak species. Therefore, at present it is very important to identify individuals, families and oak descendents from different ecological zones that are the most resistant to elevated temperatures.  The aim of our research is to study the comparative plant state depending on the genetic characteristics of the pedunculate oak (Quercus robur L.) descendents at the same age, different ecological origin, and growing in the Scientific Reservation "Plaiul Fagului". Plantations growing from local seeds usually have a higher stress resistance and productivity. However, sometimes the ecotypes from other zones have advantages over the local for a number of economically important qualities. Growth and state of plants depends not only on the geographic origin of the seeds, but also on environmental, phenological and individual variability within specific climatic region. The revealing of how in a long time interval the growth and adaptations of descendents of different ecological origins are expressed provides opportunities to evaluate the effectiveness of using the seeds from distant areas during the afforestation works. Conservation of genetic diversity of various forest tree species is conducted through programmes employing in situ and ex situ methods. Conservation of native species by the in situ method is based upon a status quo concept of protection of natural conditions in local habitats with optimal allelic gene frequency having been attained, ensuring survival and reproduction in a given environment. Furthermore, this means that the local populations and certain species of forest trees show best resistance and adaptability to stressful environmental conditions, as well as to pests and diseases. Studies conducted on conservation of genetic diversity include necessary knowledge of the minimum viable population which is necessary for the population’s relatively safe survival in terms of genetic, demographic, environmental and other factors.