Cortinarius cupreorufus is a characteristic and rather well-known indicator species of the rich mycorrhizal fungus element being restricted to calcareous coniferous forests. The species is widespread but rare in Eurasia and N America, and is suffering from decline of calcareous coniferous forest types, due to e.g. areal loss in more heavy populated areas and loss/fragmentation of older coniferous forest stands from modern (clear-cut) forestry. Populations declines are inferred to be approaching the level (25% reduction over three generations in the past and future) to trigger a threatened listing under criteria A2c+3c+4c, hence it is listed as Near Threatened.
Cortinarius cupreorufus belongs to a bicentric boreal-montane coniferous forest element in Europe (Brandrud 2000). Rare, but widespread within the areas of Cortinarius subgenus Phlegmacium-rich, calciphilous coniferous forests in (i) N Europe and (ii) montane-subalpine regions of C and S Europe. The species is also reported from N Asia (Russia) and western North America but seems very rare.
The species is known from 125 localities in Norway, 120 localities in Sweden, and probably approximately the same in Finland. The real number of localities in Fennoscandia is estimated to ca. 3,000, and the real number in N Europe could be 4,000-5,000 localities, when adjacent areas of the Baltic and Russia are included. The species seems somewhat rarer in the montane-subalpine coniferous regions of C Europe, with a rough estimate of 3,000-4,000 localities; altogether approx. 7,000-9,000 localities in Europe. (Few data are available on localities in C/S Europe; according to literature, approx. 32 localities were known from this area per. 2,000; according to recent databases and literature, ca. 40 localities are known from Austria, 13 localities from Slovenia, and 23 localities in Baden-Württemberg, SW Germany).
The species is recorded almost north to the northern border of Picea abies forests in N Fennoscandia (Kaukonen 1994, Jeppesen et al. 2012), and south to NE Spain (Pyrenees 1,400-1,500 m a.s.l., Mahiques 2000) and C Italy (N Apeninnes, Consiglio et al. 2003). Distribution in E Europe little known, but recorded from Poland, probably widely distributed in the Carpathians. The species is recorded from three regions of Russia, including Asian parts (Nezdojminogo 1983).
The species seems to be very rare west of the natural distribution area of Picea abies, but a few outposts are recorded in the Pyrenees (Abies alba forests) and in the fjord districts of Norway (Pinus sylvestris forests). The species occurs high up in the subalpine spruce forests both in C Scandinavia and in the Alps, and occurs near the arctic timberline in N Finland (Kaukonen 1994).
The species is reported from various parts of (montane) Western North America north to the Olympic peninsula, Washington (Moser et al. 1994).
The species is mainly associated with older coniferous forest stands, without influence of modern forestry with clear-cuts. In some, very calcareous areas, it may also (re-)establish in younger, planted forests, due to a high dispersal pressure from adjacent, larger populations in older forests.
Population Trend: decreasing
Cortinarius cupreorufus grows in calcareous coniferous forests, often in deep moss, in dry, shallow soil on limestone outcrops/ridges, sometimes in seasonally ground water influenced habitats or along brooks/creeks. In Europe, it is associated mainly with Picea abies, but also with Pinus sylvestris and Abies alba. In North America probably also with other conifers such as Pseudotsuga menzieni. The species produces large fairy rings in optimal habitats. The species is an important indicator/signal species for calcareous forests with a rich fungal diversity of high conservation value, with many specialized and rare species (rich hot spots; cf. Nitare 2010).
The species is threatened by loss, depauperation and fragmentation of intact, calcareous coniferous forest habitat, due mainly to intensive forestry with clear-cuts. The species seems, especially in northern areas, to suffer from re-establishment in production forests with a (clear-cut) turnover period of less than approx. 80-100 years. The species seems also favored by a moderate level of disturbance such as moderate forest fires and cattle grazing in forests, keeping the forests in a semi-open stage, with openings in the forest floor (small tracks/paths, etc.) and preventing a too heavy humification/acidification of the top soil overlying the calcareous layers.
Cortinarius cupreorufus is included in a number of European Red Data lists (e.g. of Austria and Germany). It is Red-listed as Near Threatened (NT) (C2a(i)) in Norway, and as Vulnerable (VU) (A2c+3c+4c) in Sweden. The estimates of decline of the species and its habitat (calcareous coniferous forests) vary from approx. 10% to >30% decline over the evaluation period (50 years) in Fennoscandia. Calcareous pine forests (NT) and calcareous spruce forests (VU) is red-listed as nature types in Norway, and calcareous coniferous forests types (including e.g. calcareous pine forests of the Carpaths) are on the Natura 2000 list. A decline of 25% over 50 years (three generations) in the past and in the future seems realistic for Europe as a whole.