What is a continuity forest?
A continuity forest is a forest that has never been clear-cut and the tree continuity has not been broken by clear-cutting or by having been arable, meadow or pasture land. The forest has thus been continuously wooded for a long time.
Are there different definitions of continuity forests?
With regard to the classification of various types of forests, there are some different concepts and definitions.
Sveaskog has chosen to use the definition of continuity forest defined by Skogforsk, with the support of LRF Skogsägarna and the Swedish Forest Agency, on the Skogskunskap (forestry knowledge) website:
A continuity forest is a forest area that has been covered with trees for a long time and has not been cleared. There must also have been no significant changes of tree species. Continuity forests usually have high nature values.
A concretisation of the definition for the practical work of identifying 140-year-old continuity forests has been done with the aim of being easy to apply in practice:
For a stand to be counted as being over 140 years old, either
- at least 30 percent of its trees
- or 200 trunks per hectare must be more than 140 years old.
The Swedish Forest Agency has produced a guide for its inspection work and provides a similar definition of continuity forest:
Area that has been continuously forested for a very long time without significant changes in tree species. A practical foreseeable time horizon back in time is usually the last two forest generations (from a production perspective).
Sveaskog also uses this definition in the nature value assessment methodology it introduced in May 2022.
It may be useful to know that the Forest Stewardship Council (FSC) standard does not include the concept of continuity forest.
Continuity forest in Dalarna, Sweden
Do continuity forests always have high nature values?
Continuity forests can be felled to a certain size, thinned, selectively felled or fertilised and still have unbroken continuity and therefore still be classified as continuity forests. Continuity forests often have high nature values, but this is not always necessarily the case. Even if they have never been clear-cut, they may be managed in such a way that they lack old trees, dead wood and the presence of conservation species.
What is the difference between a continuity forest and a normal planted production forest?
Because a continuity forest has never been clear-cut, it is favourable for species that are sensitive to clear-cutting and land preparation. This is particularly true for certain mycorrhizal fungi, which live in symbiosis with tree roots and may find it difficult to re-establish themselves in an emerging stand because the continuity of tree roots has been broken by clear-cutting. Therefore, it may be appropriate to give extra consideration when felling continuity forests that may be home to such types of sensitive species. Continuity forests that have high nature values according to Sveaskog's nature value assessment methodology must always be set aside in their entirety as conservation forests. These include woodland key-habitat and biotopes requiring special consideration, but also many forests that do not fulfil the criteria for key biotopes.
Alectoria sarmentosa
How does one know if a forest is a continuity forest? What specific characteristics are associated with continuity forests?
Continuity forests often have uneven ages and are otherwise varied in terms of their ecological structure. In north-western Sweden's pine forests, there are often traces of fire in the form of, for example, fire rings on the pines, while the spruce forests in the same area are often multi-layered with trees of different sizes and rich in certain hanging lichens such as twig lichen.
Why has the amount of continuity forests decreased in Sweden?
Felling has been the dominant logging method in many parts of Sweden since the mid-20th century, and for much longer than that in the southern parts of the country.
Where are the continuity forests in Sweden?
Continuity forests are located throughout the country but are particularly common in north-western Sweden. This is because felling was introduced later in the north-west and forestry has been less intensive there. As a result, many continuity forests have been protected as nature reserves and national parks, or by being set aside voluntarily by the forestry industry. This is also why Sveaskog decided in 2021 to set aside all continuity forests in north-western Sweden that are more than 140 years old.
There are also continuity forests in southern Sweden, but planting and regrowth on arable land and treeless meadows and pastures has been common since the 1960s. Forests that are less than 60-70 years old are normally not considered to be continuity forests. It can be more difficult to recognise continuity forests in southern Sweden because they often have a history as grazing forests or wooded pastures.
Dead wood.
How much continuity forest does Sveaskog have?
It is difficult to answer this question precisely, but apart from the designated conservation forests, all the forests in north-western Sweden and some parts of the rest of northern Sweden that are more than about 70 years old are generally continuity forests. Continuity forests are rare in southern Sweden, and it is difficult to assess the amount there. In general, all forests younger than 60-70 years old have been planted after clear-cutting and are therefore not considered to be continuity forests.
How much continuity forest has Sveaskog set aside for nature conservation?
Sveaskog has set aside a total of 460,000 hectares of productive forest land for nature conservation. A large proportion of these forests are continuity forests with high nature values. In addition, Sveaskog decided in 2021 to set aside all continuity forests more than 140 years old in north-western Sweden, regardless of whether or not they have high nature values. Our forecasts show that this means there are around 14,000 additional hectares to add to what has already been set aside. In total, we have therefore set aside 181,000 hectares in north-western Sweden, most of which is covered by continuity forests.
Traces of several fires - both historic and recent.
Are continuity forests managed?
Significant areas of continuity forest are set aside for nature conservation and only nature conservation management is carried out there. The continuity forests that do not have high nature values are managed in the normal way. Pine forests are normally managed with compartmental felling, with general or additional consideration in the form of left trees, dead wood and consideration areas, but various types of shelterwood are also common management methods in continuity forests.
Which species typically exist in continuity forests?
In general, species associated with continuity forests require environments and substrates that have been unaffected for a long time (unbroken continuity) and that take a long time to develop. These can be various lichens, mosses and fungi that don't thrive in more broad-leaved and managed forests. In continuity forests on lean soils and dominated by pine, many species are linked to fire and grow on fire stumps, and lying and standing dead wood, such as various species of small clam lichen. In spruce-dominated multilayered continuity forests, different types of hanging lichens can be found, such as twig lichen or white-rot fungus on fallen trees.
Phellinus ferrugineofuscus
