New research explores the impacts of continuous cover forestry in Sweden

Currently, nearly all of Sweden's forests are managed using even-aged forestry, where the forest is clear-cut after 60 to 120 years and then replanted with new trees.

"The final harvest and the subsequent clear-cut phase disadvantage several forest-dwelling species. There is a growing societal interest in alternative management methods, such as selective logging and continuous cover forestry. The hope is that such methods will benefit biodiversity and forest ecosystem services," says Jörgen Sjögren, a researcher at SLU and the leader of the study.

Simultaneous studies of species and ecosystem services

Selective logging involves harvesting the largest trees at intervals of approximately every fifth to fifteenth year, while gap cutting creates smaller openings in the forest (see fact box below). Currently, there is limited knowledge on how selective logging and gap cutting affect biodiversity and ecosystem services.

Separate studies have shown, for example, that several bird species benefit from leaving small and medium-sized trees during forestry operations, while lichens living lower on tree trunks are disadvantaged due to shading from the retained small trees. Regarding timber production, it is challenging to draw clear conclusions about how it is affected by non-clearcut methods. Summarizing previous research on forest ecosystem services, some studies indicate a decrease in timber production with clearcut-free methods, while others show a slightly increased timber production. Blueberry shrubs benefit from leaving more trees during forestry operations.

"This underscores the need to study multiple species groups and ecosystem services simultaneously when examining the effects of a new forestry system, which has not been done on a larger scale concerning selective logging and gap cutting. We aim to change that with our research," says Jörgen Sjögren.

Study areas in Sweden and Finland

The research will be conducted in several Swedish and Finnish forests where some studies on species and ecosystem services related to selective logging and gap cutting have already been carried out. These data will be supplemented with new investigations. A total of seven different species groups (for example mosses, lichens, beetles, and vascular plants) will be included in the study.

"Transitioning from one management method to another requires suitable and accessible forests for the new methods. Mapping where in the country such forests are located is also part of the project," says Jörgen Sjögren.

For example, selective logging requires a forest with trees of all sizes but with significantly more small trees than large ones, known as a full-layered forest.

"With this project, we aim to contribute to increased knowledge about how biodiversity is affected by these management methods," concludes Jörgen Sjögren.