Cortinarius areni-silvae is a rare ectomycorrhizal fungus associated with Pinus sylvestris in the boreal parts of Europe to Western Siberia. It grows in is dry and nutrient poor lichen - lingonberry dominated sandy old pine forests. This habitat has been and is being negatively impacted by clear cutting and reducing areas of oldgrowth of Scots pine outside protected areas. Is estimated to have declined and to be continuously declining at the global scale due to decreasing area of old growth pine forests and an apparent poor ability to spread and re-establish in managed forest after clear-cutting.

These forests have been and are seriously declining due to forestry but also due to roads, industry/settlements/military activities as well as gravel pits.

The population is estimated to consist of c. 1000 localities and c.x 20 000 mature individuals. The decline of the major habitat of C. areni-silvae is estimated to be in the magnitude of 25-30% in 50 years (three generations) and predicted to continue to decline. The population size is inferred to undergo a similar decline, approxing 30%. The species is thus assessed as NT (A2c+3c+4c).

Cortinarius areni-silvae is distributed in the boreal region of Eurasia, from Fennoscandia (mainly the eastern parts) to the east to Western Siberia (Altay) and probably also further east. The species has a few records in Denmark. It is reported to be rare in Russia.

The species is a rare species presently known from approx. 150 ocalities in the Nordic countries (6 localities in Denmark, 5 localities in E Norway, c. 50 localities in Sweden and stated as rare but widespred in eastern Finland. It is reported as quite rare in Russia (Tatiana Svetasheva, pers. comm). As the knowledge of the population size in Russia is poor, it is conservatively inferred that the number of sites may approach 1000. According to Dahlberg and Mueller (2011), the number of individuals is estimated to approx 20,000 (c. 1000 localities x c 20 mature individuals in each).

The species is nationally redlisted in Denmark (EN; Moeslund et al 2023), Norway (NT; Artsdatabanken (2021) and Sweden (NT; SLU Artdatabanken 2020)). In Finland it is assessed as LC) It is also noticed as an indicator species for oldgrowth sandy Scots pine forests in Finland (Bonsdorff et al 2014), Norway (Brandrud and Bendiksen, 2014 and in Sweden (Nitare 20204; Björnström and Wikström 2024).

The decline of the major habitat of C. areni-silvae (older, dry, sandy pine forests) durig the last 50 years is estimated to be 25-30% in Fennoscandia (Brandrud and Bendiksen 2014) and thought to be similar in the Russian Siberian forest (Flintoff 2013, Kukavskaya et al. 2013). The species population size is inferred to undergo a similar decline of c. 25% within this time frame, corresponding to three generations (see Dahlberg and Mueller, 2011).

Cortinarius areni-silvae is a rare species within the group Phlegmacium of Cortinarius. Its is a mycorrhizal fungus associating with Scots pine growing in nutrient-poor dry and sandy oldgrowth forests with a vegetation of lichens and lingonberry (Vaccinium vitis-ideus) (Brandrud and Bendiksen 2014; Nitare 2023; Nitare et al 2024). The species seems to favour sparse oand light open forests with exposed sand and thin vegetation. Even at extensive areas of appropriate habitat, it is only rarely encountered, typically with single scattered sporocarps.

The species is primarily threatened by clear-cutting of old-growth pine forests (see e.g. Svensson et al. 2019 from Sweden, Kotiaho 2017 from Finland). It is rarely observed in forest regenerated after clear-cutting. Hence conversion of old growth forests to managed forest, i.e. reduced amount of sandy old growth pine forestis the main cause of the decline. It is also negatively affected by areal loss (expansion of urban settlements, military areas, roads etc. (see Brandrud and Bendiksen (2014).

The potential pine habitat is located in northern Europe and extending to western Siberia. Around 1% of the forest is cut annually, so a conservative estimate of the potential decline of appropriate habitat is approximately 30% over 50 year period taking into account uncertainties of forest cutttings and the population in Russia. The population size is inferred to undergo a similar decline, approaching 30% over 50 year period (three generations, see Dahlberg and Mueller, 2011).

Being an ectomycorrhizal fungus, C.areni-silvae is dependent on its obligate association with pines. Although the sporocarps are short-lived, the soil-dwelling mycelia is perennial and may potentially live several decades or even centuries. With a continous presence of mature Scots pine trees at a location, the mycelia may potentially become as old as the trees. Probably C. areni-silvae, as most of this habitat´s ectomycorrhizal fungi,has evolved to survive the historic typically low intensity fires in boreal forests. A key for this survival was that a significant number of trees survived the fires with much of its ectomycorrhizal community associated to its roots.

Site protection is recommended for sites where this species and other ectomycorrhial fungi of conservation interest in this habitat interest have good populations. As forest fires has been an evolutionary important natural distrubance in this habitat, natural or prescribed burning should be considered to maintain desired forest dynamics and biodiversity.

A better understanding of the specie’s biologyand population dynamic would facilitate a better management, e.g.at what conditions it may establish, mycelial longevities and demographic structure within populations. Also to what degree retention trees and alternative forestry in managed forest may maintain the species.

The species is not used.

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Björnström H and Wikström P 2024. Sandtallskogens marksvampar (In Swedish: The fungi of sandy pine forests). Mykologiska publikationer 10. Sveriges Mykologiska Förening. Hamburgsund.

Brandrud, T. E. & Bendiksen, E. 2014. Fungi of sandy pine forests in Norway, and a comparison of this threatened elemööent elsewhere in Europe(-Asia). Agarica 35: 67-87.

Dahlberg A & Mueller G. 2011. Applying IUCN red-listing criteria for assessing and reporting on the conservation status of fungal species. Fungal Ecology 4: 1-16

Flintoff, C. 2013. In Russia’s Vast Far East, Timber Thieves Thrive. Available at: https://www.npr.org/sections/parallels/2013/10/22/239665474/in-russias-vast-far-east-timber-theives-thrive?t=1555403390780.

Kotiaho, J.S. 2017. On effective biodiversity conservation, sustainability of bioeconomy, and honesty of the Finnish forest policy. Ann. Zool. Fennici 54: 13-25.

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Nitare J. 2023. Skyddsvärd skog: naturvårdsarter och andra kriterier för naturvärdesbedömning (In Swedish: Protected forest: nature conservation species and other criteria for nature value assessment). 3rd ed. Skogsstyrelsen. Jönköping. ISBN 987-91-986297-0-5 ö

Nitare J Knutsson T, Brandrud TE, Stjernegaard Jeppessen T and Guldberg Fröslev T. (2024) Ädelspindlingar - guide till svenska natruvårdsarter (IN Swedish: Phlegmacium - a guide to Swedish species of conservation interest. Mykologiska publikationer 12. Sveriges Mykologiska Förening. Hamburgsund. ISBN 978-91-527-9109-7

SLU Artdatabanken (2020). Rödlistade arter i Sverige 2020. (Red-listed species in Sweden 2020)
SLU, Uppsala ISBN 978-91-87853-54-8

Svensson, J., Andersson, J., Sandström, P., Mikusinski, G. and Jonsson, B.G. 2019. Landscape trajectory of natural boreal forest loss as an impediment to green infrastructure. Conservation Biology 33(1): 152-163.

von Bonsdorff, T., Kytövuori, I., Vauras, J., Huhtinen, S., Halme, P., Rämä, T., Kosonen, L. & Jakobsson, S. (2014). Sienet ja metsien luontoarvot. Norrlinia 27, 272.