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A mixed forest leads to less damage to trees, according to extensive data analysed by Micael Jonsson and his colleagues. Photo: Ulrika Bergfors
A mixed forest leads to less damage to trees, according to extensive data analysed by Micael Jonsson and his colleagues. Photo: Ulrika Bergfors

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Mixed forests reduce the risk of forest damage in a warmer climate

Forests with few tree species pose considerably higher risk of being damaged and especially vulnerable is the introduced lodgepole pine. This is shown in a new study by researchers from Umeå University and the Swedish University of Agricultural Science in Uppsala. The results can be useful for preventing forest damages and financial losses related to the forest industry.

Fungi, insects, fires and cervids, such as moose, are examples of natural factors behind tree damages in Swedish forests. Sometimes, the damages become so extensive that they impact the function of forest ecosystems, not least the ability of forests to provide wood and other tree products.

“In a warmer climate with more extreme weather and new pest organisms, and with a more intense forestry, forest damages are expected to become more common and more severe. It is therefore important to understand causes of forest damages and whether it can be prevented,” says researcher Micael Jonsson at Umeå University, who led the study.

The Swedish national forest inventory has collected extensive data from Swedish forests. Since 2003, data on forest damages have also been collected.

In the current study, the research group has analyzed 15 years of these data from all over Sweden, to investigate which damages are most common and which factors determine the risk of a tree becoming damaged. The study is more extensive both in time and geographically than previous studies.

The results show that wind and snow are the most common causes of tree damage, followed by forestry and then fungi. Damages from cervids – mostly moose – are on fifth place. 94 percent of all trees showed some kind of damage. Coniferous trees and young stands showed the highest risk of damage, and in warmer parts of Sweden, stands with few tree species showed a considerably higher risk of being damaged compared to stands with a higher number of tree species.

“Our results show that there is a potential to reduce the risk of forest damages via a changed forest management. Especially, a higher proportion of broadleaf trees in the otherwise so coniferous-dominated production forest would result in fewer damages. We can for example see that the lodgepole pine, introduced by the forestry industry, has the highest risk of damage. Its introduction therefore counteracts a profitable forestry,” says Micael Jonsson.

The results also indicate that a higher number of tree species in a stand act as an insurance against extensive forest damages in a warmer climate.

“We must adapt Swedish forests and forest management methods to a future warmer climate. Including more tree species in production forests seems to be an adaptation that could work!” says co-author Jan Bengtsson at the Swedish University of Agricultural Science.

However, the study also shows that the data material has some weaknesses. For example, it has not been possible to establish the cause behind a large proportion of the damages.

“The national forest inventory collects important data for our understanding of the forest, but when it comes to the damage inventory, the data quality needs to improve to be fully usable in forestry practices,” says Jon Moen, co-author at Umeå University.

About the scientific article

Micael Jonsson, Jan Bengtsson, Jon Moen, Tord Snäll. Tree damage risk across gradients in tree species richness and stand age: implications for adaptive forest management. Ecosphere, 19 November 2024. DOI: 10.1002/ecs2.70071

Read the full article: https://esajournals.onlinelibrary.wiley.com/doi/10.1002/ecs2.70071

For more information, please contact:

Micael Jonsson, Associate Professor, Department of Ecology and Environmental Science, Umeå University

Phone: +46 90 786 69 23

Email: micael.jonsson@umu.se

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Umeå University is a comprehensive university and one of Sweden’s largest higher education institutions with around 38,000 students and 4,600 staff. We have a diverse range of high-quality educational programmes and research within all disciplinary domains and the arts. The University offers world-class educational and research environments and helps expand knowledge of global significance. This is where the groundbreaking discovery was made of the CRISPR-Cas9 gene-editing tool, which was awarded the Nobel Prize in Chemistry. At Umeå University, everything is just around the corner. Our tightly knit campus makes it easy to meet, collaborate and share knowledge, something that encourages a dynamic and open culture.

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Sara-Lena Brännström

Sara-Lena Brännström

Communications officer Faculty of Science & Technology +46 90 786 72 24

Umeå University

Umeå University is a comprehensive university and one of Sweden’s largest higher education institutions with around 38,000 students and 4,600 staff. We have a diverse range of high-quality educational programmes and research within all disciplinary domains and the arts. Umeå University is also where the groundbreaking CRISPR-Cas9 gene-editing tool was discovered, starting a revolution in genetic engineering that led to the Nobel Prize in Chemistry.

The University has an international atmosphere and centres its work around core academic values. Our tightly knit campus makes it easy to meet, collaborate and share knowledge, something that encourages a dynamic and open culture where we celebrate each other’s successes. Umeå University prides itself in offering a world-class educational and research environment and expanding knowledge of global significance, where the sustainable development goals of Agenda 2030 inspire and motivate. We have creative and innovative research environments that offer the best potential for taking on the challenges facing society. Through long-term collaborations with organisations, industry and other higher education institutions, the University is helping northern Sweden become a knowledge region. The societal transformation and the massive investments currently occurring in northern Sweden create complex challenges but also opportunities. Umeå University is focused on conducting research about and within a society in transition and continuing to offer academic programmes for regions that need to expand quickly and sustainably.

Campus Umeå and the Umeå Arts Campus are close to the city centre and next to one of Sweden’s largest and most renown university hospitals. Education is also provided in several other towns, including Skellefteå, Örnsköldsvik, Lycksele and Kiruna. Umeå University is home to the highly ranked Umeå Institute of Design, the environmentally certified School of Business, Economics and Law, and the School of Architecture, the only one in Sweden with an artistic profile. Next door is Bildmuseet, which is Umeå’s contemporary art museum, and Curiosum, Umeå’s science centre. Umeå University is one of Sweden’s five national sports universities, has an internationally leading Arctic Research Centre, and has Várdduo, which is Sweden’s only research unit for Sámi research and indigenous research.