Background & Aims

Old, hollow and large deciduous trees are one of Swedens most important keystone structures.  As the trees grow older and larger, they start to develop characteristics, such as hollows, wood mould, decaying roots, dead branches, deep bark fissures, fruits and sappy wounds, that a wide array of organisms utilise as shelter, food source or substrate. Usually, these trees of high biodiversity value (HBV) are defined by the following measurements: Giant trees (Trunk diameter ≥ 0.8 m), Hollow trees (Trunk diameter ≥ 0.4m dbh with entrance hole ≥ 3 cm diameter) and Old trees (Oak and beech older than 200 years. Other tree species older than 140 years). Many different lichens, birds, bats and arthropods are entirely dependent on these deciduous trees. A considerable portion of these organisms are endangered.

Three important features, indicating a trees biodiversity value do exist. Vitality stage, meaning the trees physical condition, is important since different organism utilise different successional life stages of a tree. Trunk circumference can act as a rough indicator of age and availability of characteristics that many organisms need to utilise the tree. Many organisms are also dependent on different types of hollows in trees. Therefore, hollowness stage/size provides information on what type of species can utilise the hollows.