Pure stands, especially those consisting of conifers such as spruce, are particularly susceptible to drought, storms and infestation by pests such as the bark beetle. Many studies show that the conversion to climate-stable mixed forests is one of the most important measures for protecting our forests. It will also help to achieve continuous high yields for the timber industry into the future.
Mixed forests are more productive and economically viable
It is often assumed that pure stands are more economically productive. Scientific studies prove the opposite. For example, a comprehensive analysis and evaluation by Pretzsch & Schütze for Central European forests shows:
Stand productivity in mixed stands is 7–53% higher than in pure stands, depending on species combination, site quality and stage of development.
This is due to the more efficient use of resources such as light and nutrients by different tree species.
Mixed forests are more resilient
Mixed forests are like good insurance: they spread the risk and thus protect against the greatest threats – now and into the future.
1. Drought-resistant
A study by the Helmholtz Centre for Environmental Research (UFZ) shows that mixed forests cope much better with drought.
While the productivity of monocultures plummeted by 50% during drought, it only fell by 25% in diverse forests.
2. Pest-resistant
In mixed forests, pests such as the bark beetle are not finding an unlimited food supply. The Forest Research Institute (FVA) confirms that tree diversity slows down the spread of diseases and insects.
3. Windthrow-resistant
Mixed forests are more wind-resistant. The roots of different tree species anchor themselves better in the soil, supporting each other and thus minimizing the risk of widespread windthrow.
A study by the Northwest German Forest Research Institute, which looked at storms such as “Kyrill,” showed that mixed stands are on average 25-50% more resistant to windthrow than pure stands.
4. Risk diversification
Using different tree species in the same area spreads the risk of loss. In the event of the unexpected death of a tree species—such as ash dieback or bark beetle infestations—the stand remains stable.
Conclusion
The conversion of forests to mixed forests is essential from an ecological and economic point of view. This investment in diversity is the best insurance for your forest property.
We are happy to support you in planning and implementing your forest conversion project.
Sources & further information
“Tree species mixing...”, Pretzsch & Schütze read here
Silvicultural lessons from Hurricane Kyrill, Jörg Nagel (NW-FVA), “Forst & Holz (63/3)”
