Assessment Notes

Justification

Tricholoma borgsjoeënse is a mycorrhizal species associated with rich/calcareous old-growth forests of Picea abies and more or less confined to boreal areas of Fennoscandia, possibly also occurring in western Russia (Brandrud 2013, Christensen and Heilmann-Clausen 2013). The species is regarded as threatened in the Nordic countries, declining e.g. from clear-cut forestry and fragmentation of older Norway Spruce stands. The species is assessed as Vulnerable because of an estimated reduction of more than 30% over the last 50 years (three generations), a decline projected to continue and caused by habitat loss and degradation. This meets the thresholds for listing as VU A2c+3c+4c.

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Geographic range

The species has its major distribution in boreal regions of N Europe. It is rare but has a wide distribution in boreal C-N Fennoscandia, and very probably also occurs in adjacent areas of W Russia (Brandrud 2013). It is also known from two recent records of montane-subalpine spruce forest regions in C Europe; from The Czech Republic (Holec and Kriz 2012) and from Germany (from database). A very closely related species, T. atroviolaceum occurs in North America.

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Population and Trends

Tricholoma borgsjoeënse was described in 2006 from Sweden (Jacobsson and Muskos 2006), and is thus still fairly poorly known. Apparently, it is a northern, rare species, more or less confined to richer/calcareous, boreal Norway spruce forests. Most records are from central- and northern parts of Fennoscandia (middle- northern boreal regions). It follows the boreal spruce forest belt almost to the west coast of C Norway. In Norway, it is reported from 10 localities (2014). mainly in Trøndelag (-Nordland) and some inner valleys of SE Norway. In Sweden, the species is also known from approx. 10 localities, of which six are from Medelpad, C. Sweden, the district from where the species was originally described. In Finland the species is recorded from the south coast up to Lappland, but everywhere very rare (Salo et al. 2005. The real number of localities in Fennoscandia is estimated at 400-500. The species is expected to occur also in (W) Russia, but suitable rich-calcareous spruce sites probably thins out eastwards in N Europe. More localities will probably appear also in C Europe, but these are likely to be few and small outposts of a northern distribution, to be compared with other, northern boreal spruce forest taxa in Europe, such as Cortinarius borgsjoeensis.

The population of the species is declining due to clear cutting and fragmentation of older, high-productive Norway spruce stands. There is also considerable habitat loss of rich/calcareous spruce forests in the Nordic countries as the calcareous areas often are small, already naturally fragmented, and situated in urbanized areas. The forest habitat, calcareous spruce forests are red-listed as Vulnerable in Norway, and these forests are regarded as declining in the same magnitude in Sweden. Altogether, we estimate that the mature/old-growth stands of rich/calcareous spruce forests have had a decline of >30% in Fennoscandia over 50 years.

Tricholoma borgsjoeënse is red-listed as VU (C2a(i)) in Norway (2015) , as VU (A2c+3c+4c; C1+2a(i)) in Sweden (2015) and as Near Threatened (NT) (B2a,b(iii,iv); D2) in Finland (2010).

Population Trend: decreasing

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Habitat and Ecology

Tricholoma borgsjoeënse is an ectomycorrhizal fungus associated with Norway spruce, Picea abies. It occurs in rich low-herb spruce forests, or calcareous spruce forests, often in mossy, mesic to seasonally hydrophilous sites. It is mainly associated with older spruce forest stands that have not been influenced by modern forestry with clear-cuts.

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Threats

Tricholoma borgsjoeënse is threatened by loss, decline and fragmentation of old growth Picea abies forest habitat. The species seems to have a poor ability to re-establish in managed forests after clear-cutting and a (clear-cut) turnover period of less than ca. 80-100 years.

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Conservation Actions

To prevent decline and fragmentation of rich spruce forests with good habitat quality, it is important to set aside reserves with productive coniferous forests as well as to identify appropriate woodland key habitats. In production forests, it will  promote the potential occurrence of the species by employing low intense selective cutting or having a high level of retention forestry, leaving much of the stand qualities intact, including a continuity of the trees and thereby enable the long-lived mycelia of the species to survive.

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Use and Trade

Is presumably an edible species.

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Source and Citation

Brandrud, T.-E. 2015. Tricholoma borgsjoeënse. The IUCN Red List of Threatened Species 2015: e.T76266962A76267304. https://dx.doi.org/10.2305/IUCN.UK.2015-4.RLTS.T76266962A76267304.en .Accessed on 3 February 2024

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• Country occurrence