Dead trees are known to be important for biodiversity, but for many species that depend on dead trees, not any dead tree will suffice. In a new study from the Swedish University of Agricultural Sciences (SLU), researchers have found that old, fire-damaged dead pines (known as kelo wood) are home to several red-listed lichens that are at risk of extinction as their habitats vanish.
Kelo wood or silver wood; these are the majestic silver-colored dead trees that have stood in place for hundreds of years before we were here. They have died slowly, been ravaged by forest fires, and repaired the damage with resin that has impregnated the wood, making it hard and resistant to decay.
In a recently published study, researchers examined the significance of kelo wood for lichens that depend on dead trees, also known as deadwood.
"Deadwood-dependent lichens are an understudied group. They are of considerable conservation concern in today’s forest landscape due to a general lack of deadwood and the slow growth and dispersal rates of these species”, says Albin Larsson Ekström, PhD student at the Swedish University of Agricultural Sciences.
The study was conducted in central Sweden. The researchers inventoried deadwood in sample plots which was categorised based on age and wood quality. These deadwood objects were then surveyed for lichen species that only grow on exposed deadwood. This was done in the years 2014 and 2021.
In total, 27 species of lichens were found. Six of them are categorised as Near Threatened (NT) according to the Red list of Sweden.
“All of the near-threatened species were found exclusively on kelo wood. There were also several of the more common lichens, indicating that this type of deadwood harbors a large proportion of the total community of species”, says Albin Larsson Ekström.
While the study shows that kelo wood is important for lichens depending on deadwood, there is a significant shortage of this type of deadwood in the forest landscape, and it takes several hundred years to form. This suggests that these lichens may face an extinction debt; lichen species depending on kelo wood have not disappeared yet, but they are at risk of doing so as their habitats vanish. Therefore, it is crucial to preserve the remaining kelo wood and create new ones, even though it takes a long time, according to the researchers.
“Kelo wood must be safeguarded across all steps of forest management. At the same time, new kelo wood must be created through repeated prescribed burning. However, in forests where there is already plenty of deadwood, prescribed burning should be avoided to prevent local losses of species," says Albin Larsson Ekström.
Göran Thor, a lichen expert at SLU, made the inventory of lichens. Photo: Albin Larsson Ekström, SLU
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Silverfur. Photo: Jörgen Wiklund, SLU
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Albin Larsson Ekström, Jörgen Sjögren, Line Boberg Djupström, Göran Thor, Therese Löfroth. Reinventory of permanent plots show that kelo lichens face an extinction debt. Biological Conservation. November 2023. https://doi.org/10.1016/j.biocon.2023.110363