This concept was introduced by the French National Forest Office to characterize the diversity of management methods required in forests for their necessary adaptation to climate change.
The long growth cycle of trees must now contend with a pace of climate change unprecedented in the modern era, catalyzed by human-induced greenhouse gas emissions.
In Belgium, this translates into a greater frequency and duration of summer drought episodes, likely to exacerbate physiological or health problems in certain species. Examples include the dieback problems observed in our forests on spruce (bark beetles) and ash (ash dieback), to name but a few.
The ecosystem services provided by forests can thus be threatened, whether it concerns biodiversity support functions, water regulation and purification functions, the essential role of forests as terrestrial carbon sinks, not to mention their economic functions as a source of renewable materials.
Given this situation and the inherent uncertainties, what strategies and management methods for our forests?
One guiding principle: diversify! And this diversification requires foresight in which the role of humans is paramount.
A resilient ecosystem with a thousand facets, like a mosaic. To ensure the maintenance and development of services provided by forest ecosystems, it is necessary to diversify forest species as well as management methods. The concept is established.
Diversifying Management Methods
This illustration, proposed by the National Forest Office, presents a non-exhaustive overview of management methods that can coexist within a territory. Areas left for natural “regeneration” coexist with planted forests, managed as irregular high forest, regular high forest, etc. Areas of remarkable interest are specifically managed for biodiversity. Senescence islands are created there for the development of habitats and species associated with deadwood.
DIVERSIFYING FOREST SPECIES
A tree can be planted for an exploitation period of 80, 100, 200 years… It is important to ensure the suitability between the species and the local soil and climatic conditions… as well as their probable evolution.
On the one hand, a first strategy consists of diversifying the number of adapted species at the scale of a forest plot, to increase its level of resilience. On the other hand, a second strategy involves using new species, not initially found at our latitudes.
Some native species are currently “struggling” in sites that were once favorable to them. Beech, one of the dominant deciduous species in our forests, has seen its growth decline for several decades, as is the case in the Sonian Forest. Ash, like elm before it, faces significant health problems. Furthermore, the natural migration of species is significantly slower than climate change.
To ensure the medium and long-term maintenance of forest functions, new genetic resources can be introduced. Whether these are new species (pubescent or downy oaks, Oriental beeches, Corsican pine, Atlas cedar, Byzantine hazelnut…), or individuals of native species collected from more southern regions (common beeches originating from Southern Europe,…). This is referred to as “assisted species migration“.
Introducing a non-native species should not be a haphazard undertaking. It requires a structured, long-term scientific approach, such as that implemented by the Royal Forestry Society of Belgium with its “Arboretum” program (article to be published).
Projects supported by PlantC integrate this need for diversification. Alongside you, we are proud to contribute to the mosaic forest of tomorrow.
