The protected hanging lichen longbeard may be threatened in the long term – even in protected areas. In the Skuleskogen National Park, the world’s longest lichen has declined by over 40 percent over three decades, a study shows.
Longbeards are the “Christmas tree glitter” of the natural forest and can be several meters long. It grows in old and moist spruce forests. The lichen is also an important sign of diversity in forests.
But in a long-term study, researchers can show that hanging lichen has decreased by 42 percent over 37 years in the Skuleskogen National Park, which is located in the High Coast World Heritage Site.
– It is well known that hanging lichens decrease in cultivated forests. This study indicates that the long-term survival of red-listed hanging lichens may be threatened even in forests that have strong protection, says researcher Per-Anders Esseen at Umeå University.
Longbeard is red-listed as vulnerable and protected throughout the country. Sweden and Norway have the largest incidences of longbeards in Europe and therefore have a special responsibility for preserving the lichen, say the researchers.
– Long-term data on the dynamics of populations of threatened species in forests is crucial to being able to understand and predict how these species are affected by global environmental factors. Such knowledge is also needed to develop effective management measures, says Per-Anders Esseen.
So long beards were inventoried
In 1984, the researchers carried out a comprehensive inventory of longbeards in Skuleskogen.
355 trees on which the lichen was growing were marked with numbered aluminum tags and placed at the tree base. In 2021, the inventory was repeated and the trays were searched with a metal detector.
The researchers were able to establish that the longbeard had disappeared from 81 percent of the marked trees. The die-off was greater on remaining trees than the losses that occurred through damage from wind.
A total of 207 new longbeard trees were also found, indicating high turnover of host trees at the local level.
The study has also provided completely new knowledge about the spatial dynamics of the longbeard in forest landscapes and shows that the lichen’s spread is strongly limited.
Longbeards spread mainly with larger fragments that only spread a few meters in 37 years. The poor spread explains why the lichen is linked to forests with long continuity, where trees have not been affected by forest fires. This also explains why the distribution of the longbeard in the national park was about the same in 2021 as in 1984.
Data on the composition and age of the forest show that extensive harvesting took place in Skuleskogen between 1860 and 1900, but the researchers found no large-scale disturbances during the last 80 years.
Climate change a threat
The decline in longbeards appears instead to be due to a combination of air pollution, climate change – with milder, snowy winters and summer heat waves – and denser forests. The lichen can also be threatened by storms and fires.
The study shows a great need to develop a detailed action program to ensure the survival of the longbeard in Sweden, say the researchers, who also want to see a national program for monitoring red-listed lichens in both protected and cultivated forests.
Hanging lichen – complex and sensitive
Lichens are complex symbiotic organisms between, for example, fungi, green algae and cyanobacteria. They lack roots and passively absorb water.
Hanging lichens such as longbeards, with their thin hair-like branches, are particularly sensitive to environmental impacts such as air pollution, forestry and climate change. At the same time, they are important parts of the world’s forest ecosystem.
Hanging lichens contribute to the forest’s nutrient turnover and are habitats for insects and spiders. They are also important food for the reindeer during the winter when ground lichens are unavailable.
Long-term dynamics of the iconic old-forest lichen Usnea longissima in a protected landscape, Forest Ecology and Management.
Per-Anders Esseen, Professor emeritus vid institutionen för ekologi, miljö och geovetenskap, Umeå universitet, [email protected]
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