Quantifying the target state of forest stands managed with the continuous cover approach - revisiting Moller's Dauerwald concept after 100 years

Continuous cover forestry is often considered a management alternative to age-class forestry, in closer compliance with economic as well as societal demands. It is further thought to provide forest stands of high stability and resilience under conditions of climate change. The guiding principle for the stand structure of continuous cover forestry systems is to create managed forest stands that are multi-layered and hence of high structural diversity. Past studies of both these characteristics have been mostly qualitative. Here we used data from terrestrial laser scanning (TLS) to quantify differences in stand structure between forests managed for decades according to the continuous cover concept and forests managed otherwise. We found that the vertical distribution of plant material in the continuous cover stands was relatively homogeneous and similar to the vertical distribution found in primary European beech forests. We also found that the structural complexity of continuous cover forests was significantly higher than that of even-aged monocultures of Scots pine and Norway spruce. Based on these findings, a scaled index was developed that quantifies structural attributes of TLS point clouds and can significantly distinguish continuous cover forests from even-aged forests. This index may be a useful tool to quantify the difference in structure of a given continuous cover forest stand from a target structure, meaning the theoretical structure describing an ideal continuous cover forest.