Landowners / Practitioners

Habitat trees are standing trees, either alive or dead, which display tree microhabitats. Prominent examples of tree microhabitats are cavities and rot holes, tree injuries, cankers, lichens and mosses, fruiting bodies of fungi or crown deadwood. Cavity-bearing trees are among the most important habitat trees for forest wildlife. The abundance and diversity of tree microhabitats strongly increase with tree diameter and bark thickness, and therefore typically with tree age.  They may harbour a broad range of species including bats, birds, insects, mammals, molluscs, spiders or amphibians. Especially old cavities with decayed residue can provide a home for several highly threatened forest beetles. However, also smaller trees can fulfil the role of habitat trees depending on the tree species, or the availability of injuries or epiphytic structures.

To enhance biodiversity in managed forest, the designation of habitat trees can become an integral part of forest operations besides measures such as deadwood accumulation. There are no prescriptions provided but it is recommended to retain five to ten habitat trees per hectare. Habitat trees that are selected, and properly marked, should display microhabitats, or they can also be low quality trees that would be usually removed during a thinning. In the case there are no proper habitat trees, so called “candidate” trees can be designated. At each tree marking visit especially the “candidate” habitat trees should be checked if they still apply or if there are other better candidates. Any new habitat tree, e.g. a tree with a broken top or injury should be added as an addition. The distribution of habitat trees can follow different approaches, either evenly distributed, aggregated or best both combined over a larger forest area.

The designation of habitat trees across forest management units is best combined with other protection measures. Such are strict protected forest reserves and stepping stone habitats (smaller set-asides with longer habitat histories) which can serve as donor areas for temporal colonisation of habitat structures and deadwood. Through the combination of such elements, species which have a limited dispersal potential or lack special structures will be better able to spread and establish temporarily also in managed forests. Thus, habitat trees are one important element for considerably improving the quality biodiversity matrix in managed forests.