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  • Under Assessment
  • Preliminary Assessed
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Hygrophorus subviscifer (P. Karst.) Harmaja

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Scientific name
Hygrophorus subviscifer
(P. Karst.) Harmaja
Common names
IUCN Specialist Group
Mushroom, Bracket and Puffball
Assessment status
Preliminary Category
VU A2c+3c+4c
Proposed by
Admin IUCN
Ellen Larsson
Tea von Bonsdorff
Comments etc.
Anders Dahlberg, Daniel Dvořák, Irmgard Krisai-Greilhuber

Assessment Notes

R-L categories correct, but text here does not match final assessment. Updated version will be published in IUCN´s Red List June or Nov 2019.


The forest woodwax Hygrophorus subviscifer is a rare, distinct and characteristic and well-investigated species that has has decreased in many parts of Europe and has disappeared from several regions. Its main distribution is concentrated to Fennnoscandia. It forms ectomycorrhiza with Norway spruce (Picea abies) in old-growth, herb-rich coniferous forests usually on base-rich or calcareous soils (Larsson et al. 2010, Kovalenko 2012). The species seems to have a narrow ecological niche and special requirements. H. subviscifer is used as an indicator species of remnants of old spruce forest ecosystem on productive soils with long continuity of trees (von Bonsdorff et al. 2014). These productive forest habitats are of high economic value and under heavy pressure from forestry. The prime cause for the decline of H. subviscifer is clear-cutting.
The old-growth habitat of H. subviscifer is estimated to have decreased by more than 30% during the past 50 years in Fennoscandia where it has its main distribution (estimated three generations) and probably more than 50% in a perspective of 100
years (Ref).

Taxonomic notes

The species was first described from Finland by Karsten as Agaricus subviscifer in 1878 and placed in the genus Hygrophorus by Harmaja in 1985. Was also described by M.M. Moser 1967 as Hygrophorus spodoleucus.

Why suggested for a Global Red List Assessment?

Rare in Northern and mid Europe. The largest population assumed to be in Fennoscandia, where it grows in old growth virgin coniferous forest mainly on more nutrient rich and calcareous soils, associated with (Picea abies) Norway spruce. A habitat which is strongly declining and largely fragmented due to modern forestry with large clear-cut areas.

Geographic range

Hygrophorus subviscifer has its major distribution in boreal regions of northern Europe. It is rare but has a wide distribution in the northern parts of Fennoscandia. In Russia with few observations from Ural (Sverdlovskaya Oblast) and Siberia (Tomskaya Oblast,  Yamalo-Nenetsky Okrug (Tatyana Svetasheva pers. com.) Also known with a few old reports from spruce forests in Switzerland, Estonia and Check Republic (database records). In GBIF there are 210 occurrences from Europe between 1963-2016, mainly from Norway and Sweden, four of them from Estonia and two from Finland.  There is one report from Czech Republic in 2004, but not found since then. The species does not seem to occur in North America and was not included in the monograph on North American species of Hygrophorus by Hesler and Smith 1963.

Population and Trends

Hygrophorus subviscifer is known from approximately 200-250 localities in Fennoscandia and in the range of 25-50 localities in central Europe. The number of localities in Russia is unknown. The total number of localities (including undiscovered ones) may be estimated at less than 1000.
The population of the species is declining due to forestry with clear cutting and fragmentation of older Norway spruce stands. There is considerable habitat loss of rich and calcareous spruce forests in the Nordic countries. The forest habitat, calcareous spruce forests are red-listed as VU (Vulnerable) in Norway (REFERENCE), and these forests are considered as declining in the same magnitude in Sweden and Finland (any reference?). Old-growth forests not having been subjected to clear-cutting are estimated to have decreased with between 30-50% during the past 50 years (Ref). Three generations in ectomycorrhizal fungi are estimated to 50 years (Dahlberg & Mueller, 2011) The decline of sites with H. subviscifer is estimated to be in the same magnitude as the decline of its population size.

Population Trend: Decreasing

Habitat and Ecology

Hygrophorus subviscifer forms mycorrhiza with Norway spruce (Picea abies) and is mainly found in in old unmanaged spruce dominated forests, usuallay herb rich, and on nutrient rich or more calcareous soils (Larsson et al 2010, von Bonsdorff et al. 2014). The mycelia of the fungus is long-lived and considered to potentially be as old as the trees or older. It is only recorded in old growth forests that have not been affected by modern forestry with clear cutting.

Boreal Forest


Hygrophorus subviscifer is today primarily found in old virgin forests, on more calcareous and nutrient rich soils. Today threatened by the decline and fragmentation of this suitable habitats. The forest type has declined with >30 % in Fennoscandia during the last 50 years. The species seems to have poor ability to reestablish in managed forests after clear cutting. Rotation time in managed forests are about 80-100 years.

Unintentional effects: large scale (species being assessed is not the target) [harvest]Habitat shifting & alteration

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

Site/area protection

Research needed

Use and Trade

The species is not be used.


Artdatabanken Sweden 2019. Artfakta Hygrophorus subviscifer. http://artfakta.artdatabanken.se/taxon/831

Artsdatabanken Norway 2019. Rødliste for arter. https://www.artsdatabanken.no/Rodliste

von Bonsdorff T, Kytövuori I, Vauras J, Huhtinen S, Halme P, Rämä T, Kosonen L, Jakobsson S. 2014. Indicator fungi - Norrlinia 27:1-272.

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

GBIF 2019. Hygrophorus subviscifer. https://www.gbif.org/occurrence/map?taxon_key=3344749

Harmaja H. 1985. Studies on white spores agarics. Karstenia 25:41-46.

Hesler LR, Smith AH, 1963. North American species of Hygrophorus. The university of Tennessee Press, Knoxville.

Larsson E, Jacobsson S, Stridvall A. 2010. Släktet Hygrophorus, skogsvaxskivlingar i Sverige. SMF, Mykologiska publikationer 3, ISSN1654-546x

Kovalenko A. 2012. Hygrophorus Fr. In: Knudsen H, Vesterholt J. (Eds.) Funga Nordica. Agaricoid, boletoid, cyphelloid and gasteroid genera, Nordsvamp, Copenhagen, pp. 282–293.

Red List for Ecosystems and Habitat Types. 2018. Norweigian Biodiversity Infomation Centre. https://www.biodiversity.no/Pages/135568

Known distribution - countries

Regional Population and Trends

Country Trend Redlisted