The subdiscipline of genetics concerned with genetic variation and inheritance in forest trees. The study of forest genetics is important because of the unique biological nature of forest trees (large, long-lived plants covering 30% of the Earth's land surface) and because of the social and economic importance of forests, Knowledge of forst genetics is important. Forest genetics is the basis for conservation, maintenance, and management of healthy forest ecosystems; and development of programs which breed high-yielding varieties of commercially important tree species.