<p>Many species and hence biodiversity depend on old, large oaks (Quercus robur) with hollow trunks. The populations of oak-living organisms have to migrate to a nearby old oak in order to survive the death of the host. The oak district south of Linköping, Sweden, is unique in area and the number of old oaks. It is anyway doubtful whether regeneration of oak will secure future continuity. Oaks are light-demanding and thrive in open pastures. Grazers also pose a problem, eating acorns and seedlings not protected by e.g. thorny shrubs. This is a study of regeneration of young oaks in the oak district and the influence of management, light conditions and thorny shrubs. There were less grown-up oaks up to 40 cm diameter than between 40 and 80 cm in grazed areas. The occurrence of oak seedlings was very low in dark un-grazed areas. Seedlings were much more common under than outside of oak canopies regardless of management. Ground coverage was lower at seedlings than in random plots. In grazed areas the density of seedlings was 30 times higher in thorny shrub than outside, but few seedlings were higher than 80 cm. The study showed that thorny shrubs are vital for establishment and survival of oak seedlings in grazed areas. It also showed that there is a risk of gaps in oak age distribution in the oak district. Management should spare thorny shrub and help seedling establishment outside of oak canopies, were oak seedlings are more likely to become trees.</p>

Many species and hence biodiversity depend on old, large oaks (Quercus robur) with hollow trunks. The populations of oak-living organisms have to migrate to a nearby old oak in order to survive the death of the host. The oak district south of Linköping, Sweden, is unique in area and the number of old oaks. It is anyway doubtful whether regeneration of oak will secure future continuity. Oaks are light-demanding and thrive in open pastures. Grazers also pose a problem, eating acorns and seedlings not protected by e.g. thorny shrubs. This is a study of regeneration of young oaks in the oak district and the influence of management, light conditions and thorny shrubs. There were less grown-up oaks up to 40 cm diameter than between 40 and 80 cm in grazed areas. The occurrence of oak seedlings was very low in dark un-grazed areas. Seedlings were much more common under than outside of oak canopies regardless of management. Ground coverage was lower at seedlings than in random plots. In grazed areas the density of seedlings was 30 times higher in thorny shrub than outside, but few seedlings were higher than 80 cm. The study showed that thorny shrubs are vital for establishment and survival of oak seedlings in grazed areas. It also showed that there is a risk of gaps in oak age distribution in the oak district. Management should spare thorny shrub and help seedling establishment outside of oak canopies, were oak seedlings are more likely to become trees.