Assessment Notes

Justification

Tricholoma apium is a characteristic and well-known, mainly European species of dry, pine forests. In Europe, the species is a representative and indicator species of old, dry, lichen-dominated sandy pine forests with a high conservation value, including a rich fungal biodiversity. The habitat of dry pine forest of Tricholoma apium is assessed as having had, is presently facing and expected to continue to have a more than 30% decline in quality and quantity (pine forest area), due to altered land-use/deforestation and intensive forestry, and eutrophication by large atmospheric N-depositions (antropogenic). Evaluation period 50 years (= three generations according to the recommendation of Dahlberg and Mueller 2011). In Fennoscandia, an ongoing population decline inferred from habitat change (forest statistics) is estimated to exceed 30%. Hence, T. apium is assessed to meet the category Vulnerable (VU) under the criteria A2c+3c+4c 

Sandy oligotrophic pine forests have been declining in most parts of Europe (cf. Brandrud and Bendiksen 2014) and T. apium is included on most national Red Lists of this region (viz. Austria, Czech Republic, Finland, Estonia, Latvia, Norway, Sweden, Switzerland, and United Kingdom). The decline is due to (i) eutrophication/heavy nitrogen-deposition in large parts of Europe, (ii) habitat-loss due to urbanization and (iii) reduced habitat qualities of remaining forests due to intensive forestry with clear-cuts (i.e. in northern Europe). The element of mycorrhizal fungi in dry sandy pine forests are probably among the most threatened and declining fungal elements of Europe

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Geographic range

Tricholoma apium has its core area in N Europe, in (eastern Norway-) Sweden-Finland (-Estonia), and probably also Russia. The species further has a wide but fragmented distribution in Western and Central Europe, and appears everywhere to be very rare, with only a few sites (some more in the Czech Republic). The species is in Europe found southwest to Spain and east to Turkey (in Cedrus forest). The species is not reported from Japan or other countries in eastern Asia. Tricholoma apium is widely distributed but rare in North America (known from the Pacific Northwest and Michigan-Masachusetts-Newfoundland).

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Population and Trends

Tricholoma apium is currently known from ca. 350-400 localities in Fennoscandia (50 sites in Norway, approximately 200 sites in Sweden). The total number of localities, including yet unrecorded sites, may be 10 times  higher and are estimated to approximately 3,500-4,000 in Fennoscandia, possibly approx. 5,000 if Russia and Balticum are included. The numbers indicated from western  and central  Europe are very low (except for some more localities from the Czech Republic), approximately 100 altogether, making the estimates for the entire European populations to approx. 6,000 sites, that is approx. 120,000 individuals.

The species is rare and apparently not widely distributed in North America, possibly constituting approximately one-fourth of the total global population.

Due to various negative trends (areal loss, nitrogen-pollution/fertilization, clear-cutting), the dry (sandy) pine forests housing this species has had a considerable decline during 50 years in Europe. Probably some of the forest types in North America have had a similar decline due e.g. to modern forestry and in some areas also due to urbanization (e.g. in Massachusetts, where the forested area is now declining according to forest statistics).

The species is estimated to have decreased by more than 30% in three generations (50 years) based on habitat-loss.

Population Trend: decreasing

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Habitat and Ecology

Tricholoma apium forms mycorrhiza with Scots Pine (Pinus sylvestris) in Europe, whereas it is reported from various conifers in North America (Bessette et al. 2013). In Europe, T. apium is mainly associated with dry, often lichen-dominated sandy pine forests with thin organic soils, on glacifluvial deposits, e.g. on flood-plains along the larger rivers and on eskers-ridges (formed from subglacial rivers; Brandrud and Bendiksen 2014). In central and western Europe, the species is reported also from coastal sand-dunes with pines. In Southern Scandinavia, T. apium also occurs in calcareous pine forests without any sand deposits (but on mineralic soil with little humus). In North America, the species seems to occur mainly in sandy soils.

The species seems to be favoured by some disturbance, such as small paths/openings in humus layer and probably also low-intense forest fires with scattered surviving pine trees. The species is almost confined to old-growth forests, and is hardly observed in younger, even-aged forests that has been clear-cut.

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Threats

Tricholoma apium is primarily threatened by clear-cutting of old-growth pine forests, nitrogen fertilization of forests, and urbanization. The species appears more or less dependent on forest/tree/root continuity, and is one of the more ´sensitive sandy pine forest species to modern clear-cutting forestry.

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Conservation Actions

To prevent decline and fragmentation of the old-growth sandy pine forests with natural dynamics, it is important to set aside Scots Pine forest reserves, preferentially larger, continuous areas, in regions where the species have good populations. In these forests, natural or prescribed burning should be considered to maintain desired forest dynamics. It is furthermore important to maintain other kinds of disturbance factors, such as (moderate) grazing, providing small openings in the humus layer. 

Further studies are needed to document population dynamics, its dependence on old-growth forests with a slow turnover/root continuity and its dependence on moderate disturbance regimes with small paths or other kind of humus layer openings. The phylogeographic patterns of the species, especially the degree of differentiation between North American and European populations should be clarified. There is also a need to further document the apparent lack of the species in pine forests of eastern Asia, in sites where a number of otherwise co-occurring species are found.

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Use and Trade

Is an edible species.

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Source and Citation

Brandrud, T.-E. 2015. Tricholoma apium. The IUCN Red List of Threatened Species 2015: e.T79515478A79515482. https://dx.doi.org/10.2305/IUCN.UK.2015-4.RLTS.T79515478A79515482.en .Accessed on 3 February 2024

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• Country occurrence