Threats and measures

The oak forests were greatly reduced already in the 17th and 18th centuries, due to timber exports and ship building. Today, logging is still among the main factors affecting hollow oaks. The trees are felled to make room for houses and roads, for safety reasons, or to accommodate increased efficiency in agriculture. Deterioration of the environment in and around the hollow oaks is also something that negatively affects them. Regrowth is one example – trees and bushes start growing where the oak has previously stood by itself, leading to increased shade as well as nutrient competition. It is therefore a good measure to remove competing tree vegetation around old oak trees. In addition to taking old oak trees into account when for example developing new housing areas, it is also important to ensure that there are younger oaks in areas with old oaks. Thus, the organisms will have a new place to establish themselves when the old trees are eventually broken down.

Illustration showing root zone/”total rotsone” (1), drip zone/”dryppsone” (crown extent – 2) and estimated root plate zone /”rotplatesone”(red demarcation – 3). Intervention within the drip zone can lead to damage to the tree’s roots. In general, major measures should be avoided within the entire root zone (Biofokus). Photo: Erik Solfjeld / Biofokus.

Houses placed close to trees can lead to damaged roots, changed water access, changed sun/shade conditions and a greater need to remove dead branches and hollow or weakened trees for safety reasons. Photo: Vilde Olberg / Biofokus.

When digging under the tree crown, the roots are destroyed. Digging, even far away from a tree, can also change the tree’s water supply, which in the worst case scenario can kill the tree. Photo: Vilde Olberg / Biofokus.

Buildings that are built right next to homes will sooner or later lead to conflict. An older house on the left, a new one on the right, both in Oslo. Photo: Stefan Olberg / Biofokus.

Sources:

Direktoratet for naturforvaltning 2012. Handlingsplan for utvalgt naturtype hule eiker