Conservation of genetic diversity of forest tree species represents the foundation for sustainable forest management and preservation of natural structure of forest stands in Croatia. Diversity of geographical regions in Croatia 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 and by the increasing impact of global climatic changes. The need for conservation of genetic diversity is related to the species pertaining to social broadleaves—the prevailing species in terms of economic utilization as Pedunculate Oak (Quercus robur), Sessile Oak (Quercus petraea) and Common Beech (Fagus sylvatica). Among the conifers Silver Fir (Abies alba) is the most endangered species, with more than 70% of its population being seriously damaged. Other native coniferous species must be preserved from a decrease in genetic diversity as well. Conservation of the noble broadleaves should encompass a larger number of species from various genera (Fraxinus, Alnus, Ulmus, Prunus, Juglans, Castanea, Sorbus, Acer, Malus, Pyrus, Tilia). These are partially endangered because of their exposure to different pests and diseases, as well as by permanent exploitation due to their technical value. Changes in hydrological conditions of rivers have led difficulties in regeneration of the riparian forests and decreased the genetic variability of European Black and White Poplar in their habitats (Populus nigra, P. alba). In Croatia’s Adriatic coastal areas, there is a need for conservation of genetic resources of Dalmatian Black Pine (P. nigra ssp. dalmatica) and Mediterranean Oaks (Quercus ilex, Quercus pubescens). Conservation of genetic diversity of various forest tree species is conducted within the programmes that include in situ and ex situ methods with ensuring quality forest reproductive materials. In Croatia, a total of 125 seed stands have been selected, covering a total area of 3885.53 ha. The ex situ method is implemented by establishment of a total of 50 plots (clonal seed orchards, provenances and progeny trials, clonal archives), covering 114.85 ha.
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