Long-term yield and biodiversity in stands managed with the selection system and the rotation forestry system: A qualitative review

There is an increasing interest in implementing Continuous Cover Forestry (CCF) as a tool to mitigate negative effects of the traditional rotation forestry system on biodiversity. However, the effects of CCF on forest growth and yield and on biodiversity is still poorly known. In this qualitative review, we compare biodiversity and longterm yield between the selection system, which is a type of CCF practiced in full-storied forests, and the traditional rotation forestry system. We specifically focus on forests dominated by Picea abies, which is a tree species of high economic relevance. Our literature search resulted in 17 publications on stand growth and yield and 21 publications on biodiversity. A majority of simulation studies found a higher long-term yield in the rotation forestry system, but it is challenging to conclude which system is the most productive. The magnitude of the difference in yield between systems, and how it varies across different environmental conditions, remains to be determined. For biodiversity, comparisons of species assemblage and individual species were only made to certain phases of the rotation cycle (recent clearcuts and middle-aged stands). Nevertheless, two aspects can be highlighted: i) the species assemblage in clearcuts differ substantially from stands managed with the selection system. Some of these effects may however be short lasting as examplified by studies on beetle assamblages showing that middle-aged rotation forestry stands become more similar to stands managed with the selection system, ii) the selection system maintains a similar species assemblage as the uncut control during the first years after cutting. In conclusion, management with the selection system may come with a loss in long-term stand yield, but much of the species assemblage is maintained after logging. We recommend future studies to specifically focus on long-term effects on biodiversity - in particular on species of conservation concern. There is also a need to establish a long-term research infrastructure to further develop the field.

Automated summary

There is growing interest in implementing Continuous Cover Forestry (CCF) to mitigate the negative effects of traditional rotation forestry on biodiversity, although the impacts of CCF on forest growth, yield, and biodiversity are not well understood. This qualitative review compared biodiversity and long-term yield between the selection system (a type of CCF) and traditional rotation forestry in Picea abies-dominated forests. The majority of simulation studies found higher long-term yield in rotation forestry, but the most productive system remains uncertain. Biodiversity comparisons showed differences between clearcuts and stands managed with the selection system, but more research is needed to determine the long-term effects on biodiversity.