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.
It is a very large (up to 25 cm), showy and firm gilled mushroom with a double ring on the stipe and deeply inserted in soil with a root-like stipe based. It is an edible and searched for species. It is distributed Holarctic and present in East Asia, North America and Europe. It has an ectomycorrhizal life style and inhabits coniferous forests, mainly light montane Picea and Pinus forests. The forests have to be quite mature, well developed, not clear-cut and undisturbed. Soils are preferably calcareous mull and brown clay, terra fusca and base rich brown earths over limestone, calcareous marls and base rich silicates. In the European Nordic countries there is a considerable habitat loss of rich calcareous spruce forests as the calcareous areas often are small, already naturally fragmented, and situated in urbanized areas. The forest habitat, calcareous spruce forests is red-listed as Vulnerable in Norway, and these forests are regarded as declining in the same magnitude in Sweden. It is estimated that the mature/old-growth stands of rich/calcareous spruce forests have had a decline of >30% in Fennoscandia over 50 years (Brandrud 2015). Moist base-rich spruce and fir-spruce forests are endangered biotopes in Austria as well (Essl & Egger 2010). Catathelasma imperiale is present worldwide with estimated 1800 subpopulations and a total of 10800 mature individuals present on an Area of Occupancy of 7200 km2. Usually only a few mature individuals occur at each site. It is re-listed in 15 European countries and considered declining everywhere due to eutrophication, habitat destruction and habitat change. Worldwide, currently considered as NT because of more than 10,000 mature individuals and an AOO more than 2,000 km2. The assessment is based on quite small population size and a diminishing habitat quality.
It is a very characteristic large (up to 25 cm) and firm species deeply inserted in soil of coniferous forests. It is Red Listed in 15 European countries and considered declining due to eutrophication, habitat destruction and management changes.
It has a Holarctic distribution: E Asia (Japan, Korea), North America, Europe. In Europe its main distribution is boreal-subcontinental (Scandinavian Mountains, Limestone Alps). In Europe it is reported from the eastern (Russian Federation), southern (Italy), western (Eastern France, Belgium, Luxembourg), central (Switzerland, Liechtenstein, Austria, southern Germany, Slovakia, southern Poland), Northeast (Estonia) and Northern Europe (Finland, Norway, Sweden).
The population is small and in parts of the distribution area declining, the area is fragmented due to clear cutting and fragmentation of older, high-productive spruce stands. In the European Nordic countries there is also considerable habitat loss of rich calcareous spruce forests as the calcareous areas often are small, already naturally fragmented, and situated in urbanized areas. The forest habitat, calcareous spruce forests is red-listed as Vulnerable in Norway, and these forests are regarded as declining in the same magnitude in Sweden. It is estimated that the mature/old-growth stands of rich/calcareous spruce forests have had a decline of >30% in Fennoscandia over 50 years (Brandrud 2015). Moist base-rich spruce and fir-spruce forests are endangered biotopes in Austria as well (Essl Egger 2010).
Based on GBIF and databases available (see below) 1800 known subpopulations worldwide. The number of mature individuals has been estimated at 10800 following these lines: (a) likely number of current localities (estimated to be ca. 1800) (b) translation of the estimated total number of localities to an estimate of the total number of mature individuals in 2 steps (i calculate the number of functional individuals (ie. sporomata separated by 10 m, template = 3, = 5400): estimation of total number of localities x estimation of the average number of functional individuals/locality; ii convert the number of functional individuals into mature individuals following Dahlberg & Mueller 2010, template = 2 because isolated solitary sporomata; = 10800). The numbers of known localities are 900 and the number of yet unknown localities was estimated to be twice as high. Mature individuals are rare and rarely reach spore production due to collecting activities. The AOO is estimated as 7200 following IUCN guidelines.
Population Trend: Decreasing
It inhabits light montane coniferous forests, mainly Picea and Pinus forests, forest edges and limestone grassland with pines. The forests have to be quite mature, well developed, not clear-cut and undisturbed. Usually only a few mature individuals occur at each site. Its individuals are considered to be old and reestablishment of individuals is very difficult after heavy forest cutting. It occurs on soils moderately dry to fresh, flat to moderately medium, neutral to alkaline, low in nitrogen but well supplied with bases, preferably calcareous mull and brown clay, terra fusca and base rich brown earths over limestone, calcareous marls and base rich silicates. Is lifestly is ectomycorrhizal with conifers.
In Europe it is mainly threatened by eutrophication, habitat loss and habitat quality changes.
Reduction of eutrophication, especially pollution from nearby agricultural areas and site protection are desirable.
Research on distribution, population trends and he ecological requirements of the species should be done.
it is a searched for edible species.
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