Ecophysiological perspectives on regeneration in multi-layered forests

Even-aged single tree species management has had a long history in Sweden. The “rotational forestry” model became the most widespread approach after World War II, and gradually the managed forest area of Sweden was converted from multi-layered mixed species forests to even-aged monocultures of pine or spruce.

This practice has come under considerable scrutiny in recent years as the homogenization of forests into monocultures was increasingly recognized as a threat to forest biodiversity. At global and EU levels, the spotlight is on sustainable forest management strategies for preventing biodiversity loss, mitigating climate change, and achieving a climate neutral economy. Likewise, Swedish society is actively debating the role of forestry in delivering a multitude of ecosystem services, while maintaining biomass production. In addition, climate change is presenting new challenges for Swedish forestry, such as an observed decline in forest productivity over the last decade, reduced regeneration and increased seedling mortality, windfall and fire damage, and pest outbreaks.

It has been proposed that introducing higher diversity and heterogeneity into managed forests can be the way forward for: a) maximizing forest productivity under climate change, b) improving forest resilience, and c) simultaneously delivering other services (e.g. climate and biodiversity benefits. But while forest policy and science are exploring the possibilities of alternative forestry practices, such as mixed-species forestry or continuous-cover forestry, forest owners are generally wary of change due to the lack of adequate guidelines and historic precedent. Addressing these challenges requires a strategy for transitioning from the even-aged monocultures of today, to multilayered stands that can be managed using alternative methods, and a detailed understanding of the requirements for seedling establishment outside of the context of current regeneration practices.

The project aims to lay the foundation for this transition, by studying the eco-physiological mechanisms that determine the above- and belowground requirements and limitations of seedling performance of pioneer (pine, birch) and secondary successional, or climax, tree species (spruce) in Sweden and investigating the potential for a management framework that establishes pine and spruce in overlapping stand generations.

This work is part of the doctoral thesis of Marcus Björs at the department of forest ecology and management.