Forestry: 21% of Pine & Spruce Saplings Die – Planting Time is Key

The future of Sweden’s forests hinges on a sobering reality: roughly one in five newly planted trees doesn’t survive the first three years. A comprehensive, five-year research and development project called Föryngringskollen – meaning “regeneration check” – is shedding light on the factors contributing to this significant plant mortality rate, and pinpointing strategies to improve forest regeneration success. The findings, released by Skogforsk in collaboration with eight major Swedish forestry companies, underscore the critical importance of planting technique and site selection.

The study, which has followed over 100,000 plants across more than 1,500 stands, reveals substantial regional variation. Plant mortality is highest in Svealand, the central region of Sweden, where 28 percent of pine seedlings and 25 percent of spruce seedlings fail to establish before maturity. “A large part of the future of new forests is decided during the establishment phase, and we clearly see that many plants are already failing from the start,” explains Mattias Berglund, a researcher at Skogforsk and project leader for Föryngringskollen.

Regional Challenges: From Drought to Snout Beetles

The reasons for early plant death aren’t uniform across the country. In northern Sweden, drought stress is the primary culprit, particularly affecting pine seedlings planted in “inverted turf” – a planting method where the roots are exposed – on dry or well-drained soil. Spruce seedlings are less sensitive to the planting method in this region, but still experience higher mortality rates when planted in inverted turf or with poor root-to-soil contact.

Southern Sweden faces a different threat: the snout beetle. In Götaland, nearly half of all pine seedlings planted in unprepared soil die within three years due to beetle damage. “In southern Sweden, planting in unprepared soil is a direct risk factor – the snout beetle is unforgiving there,” says Jonas Öhlund, a researcher involved in the project. Skogsaktuellt reports that this pest poses a significant challenge to successful reforestation efforts.

The Importance of Planting Technique and Site Selection

While researchers acknowledge they can’t control the weather or the presence of pests, they emphasize the significant impact of how, where, and what is planted. The Föryngringskollen project highlights the importance of selecting appropriate planting sites and employing effective planting techniques. Specifically, planting in mineral soil – whether through digging a hole, choosing a high or low spot, or using a “hinge” method – yields the best results for pine trees across all regions.

Despite the clear benefits of mineral soil planting, the study found that 17–27 percent of plants are still planted in disturbed humus or unprepared soil, a practice consistently linked to lower survival rates, and dramatically increased risk of snout beetle infestation in Götaland.

Smaller, “bare-root” seedlings are particularly vulnerable to drought when planted in inverted turf in northern and central Sweden. However, the study also found that the survival rate of smaller seedlings is comparable to that of larger seedlings when planted in mineral soil. This suggests that plant size isn’t the primary determinant of success, but rather the quality of the planting site, and technique.

Beyond Planting: Understanding the Broader Context

The challenges to forest regeneration extend beyond immediate planting conditions. Climate change is increasing the frequency and intensity of drought events, exacerbating stress on young trees. Changes in land utilize and forest management practices can also impact plant survival rates. Skogforsk’s Föryngringskollen project page details the project’s methodology, which involves monitoring over 2,500 plantings across Sweden, distributed equally between the north, central, and south regions.

The project’s comprehensive approach – tracking plant vitality, soil conditions, and mark preparation methods – allows researchers to identify key factors influencing plant survival and develop targeted recommendations for forest managers. The data collected will be invaluable for refining reforestation strategies and ensuring the long-term health and productivity of Sweden’s forests.

What Does This Mean for Forest Health?

The findings from Föryngringskollen aren’t just relevant to Swedish forestry. They offer valuable lessons for forest managers worldwide facing similar challenges. The emphasis on site preparation, appropriate species selection, and careful planting techniques underscores the importance of a holistic approach to reforestation.

Reducing plant mortality isn’t simply an economic issue; it’s also crucial for maintaining the ecological integrity of forests. Healthy forests provide essential ecosystem services, including carbon sequestration, biodiversity conservation, and water regulation. By improving regeneration success, People can enhance the resilience of forests to climate change and other environmental stressors.

Looking Ahead: Continued Monitoring and Research

The Föryngringskollen project is ongoing, with researchers continuing to monitor plant survival rates and investigate the underlying causes of plant mortality. Further research is needed to understand the long-term effects of different planting techniques and to develop strategies for mitigating the impacts of climate change and pest outbreaks. The Swedish Forest Society highlights the need for continued data collection and analysis to refine reforestation practices.

The project’s ultimate goal is to provide forest managers with the knowledge and tools they need to ensure the successful regeneration of Sweden’s forests, safeguarding this vital resource for future generations. The initial results clearly demonstrate that significant gains are possible through improved planting practices and a deeper understanding of the factors influencing plant survival.