Cortinarius bulliardii, is a characteristic mycorrhizal species associating with Quercus, sometimes with Fagus and Corylus. It is a calciphilic species inhabiting mainly natural or near-natural oak and beech forests growing on the limestone soil. The mentioned type of habitat has an ongoing and significant declining due to areal loss and decreased ecological conditions (transformation to other types of habitats, clear-cutting, eutrophication, oak deseases, etc). The characteristic appearance of C. bulliardii and the fact that its belong to the rich fungal element of this type of habitat, make it possible to consider this species as an indicator of valuable natural territories and “mushroom hotspots”.

Global red-list assessment: There are approx. 330 known localities/sites in Europe and 1 in Turkey, the estimated total number can to be approx. 3500 localities, which corresponds to approx. 70,000 mature individuals. The decline of the calcareous Quercus forests in the 50 years evaluation period is estimated to be > 20%. Based on this, the species is assessed as NT according to the A-criterion.

Cortinarius bulliardii is a species complex, consisting of four already quite good circumscribed species (bulliardii, cinnabarinus, coccineus, longistipitatus) and more studies are underway.
At this stage it should be added that this assessment includes 2 further cryptic species of the bulliardii group still from deciduous forests (unpublished data).

Cortinarius bulliardii is a rare characteristic species associated mostly with mature calcareous broadleaved forests which are everywhere undergoing reduction and degradation. This species can be a good indicator of valuable forest communities containing at the same time many other rare species of different groups of organisms.

Cortinarius bulliardii is a European species, widely distributed within the temperate-mediterranean European Quercus-Fagus range, known from at least 23 countries, including European part of Russia, east to the Tula region (Russia), and North to S Sweden (Consiglio et al, 2003; Cortinarius bulliardii.., 2021;  Gyosheva et. al., 2006; Knutsson, T. 2014, Krieglsteiner, Gminder, 2010; Mahiques, 2000; Nezdojminogo, 1996; Peric, Peric, 2005; Rebriev et al., 2012, Tănase, Pop A, 2005; Tkalčec et al., 2008). It is also reporrted from Turkey (Şengul et al (2021).  Reports from North America are not verified by sequencing, and probably represents other taxa.

According to GBIF data and other listings, C.bulliardii is recorded from at least 28 sites in southern Sweden, 28 in France, 25 in Spain, 20 in Denmark, 17 in UK, 10 in Germany, 7 in Slovenia.  Some countries are not represented in GBIF, and some of those already mentioned above are only partially represented, but they have data on this species distribution in their national and regional databases: there are 46 known localities in Austria, about 50 in Switzerland, 60 in Italy, 30 in Hungary, 8 in Russia, and 1 in Albania. Based on this, there are an estimated approx. 330 known localities/sites in Europe, with the largest number of sites in the countries where limestone soils and appropriate forest communities are widespread.  Despite the relatively large number of localities in some countries, a decline was noted, and the species is redlisted in Austria, Bulgaria,  Denmark, Germany, Montenegro, Poland, Sweden, Switzerland (National Red Lists.., 2021; ECCF, 1998-2018), as well as in some regions of Russia (Order..,2020).
Habitat assessments at EU biogeographical level shows that the mentioned habitats (9160, 9170,9150) are assessed as Unfavourable-Inadequate or Unfavourable-Bad due to indicators of structure and function and poor future prospects (European Environment Agency, 2013-2018). An especially alarming situation is observed in oak calcareous forests, which have ongoing and significant decline from 1960s, due to oak deseases, areal loss, abandment of traditional management like grazing, forestry (Grigorjev et al. 2000, Knutsson 2014).
Taking in account all needed evidence the estimated population size in Europe is approx 3500 localities, that is approx. 70,000 mature individuals. Estimated habitat loss in the past and ongoing is >20% over the 50 years covering three generations of this species. 

Cortinarius bulliardii is a mycorrhizal symbiont of Quercus spp., Fagus sylvatica, Corylus avellana, sometimes also with Tilia cordata. It is considered to be a thermophilous species preferring warm forests and restricted to relatively old dry oak and beech forest on limestone ground. According to Nature 2000 habitats it’s confined to oak and beech calcareous forests of codes 9150 (Medio-European limestone beech forests of the Cephalanthero-Fagion), 9160 (Sub-Atlantic and medio-European oak or oak-hornbeam forests of the Carpinion betuli), 9170 (Galio-Carpinetum oak-hornbeam forests). In Eastern Europe, including the European part of Russia, it is found mainly in oak forests (or polidominant and mixed forest with oak) growing on limestone slopes of southern exposure. In Mediterranean region also growing in evergreen oak forests

The main threats for this species and it’s habitat are forestry, including clear-cutting of its habitat, conversion into conifer or poplar plantations, limestone mining, transformation of natural forest communities into parks and other recreation zones.  Intense anthropogenic impact, including nitrogen deposition as well as tourism due to mass visiting and trampling of the leaf litter, can also be a direct threat to the population decline, since disturbance or destruction of litter leads to degradation of mycelium, which usually spreads in the upper layer of the soil and the lower layer of the litter. The spread of oak decline (Phytopthora desease) throughout the region is a serious emerging threat. Drought due to changing climate in some parts of its rage are stressing its host.

The species is included in red lists of Switzerland (Vu), Sweden (Vu), Croatia (NT), Austria (NT), Bulgaria (En), Denmark (En), Germany (Vu), , Romania (Vu) (National Red Lists.., 2021; ECCF, 1998-2018,  SLU Artdatabanken, 2020, Tkalčec et al, 2008; Dämon, Krisai-Greilhuber, I. 2017, Gyosheva, M.M. et. al., 2006; Den danske Rødliste, 2019, Rote-Liste-Zentrum, 2021, Tănase, Pop, 2005), also in regional Red Data Books of Russia (Order.., 2020).
The conservation actions suggested is mainly focused on area/site protection from logging and transformation of habitats, as well as limestone mining in the location of the species and the surrounding area, regulation of recreational activities leading to the destruction of leaf litter.

More data on distribution and monitoring of C. bulliardii are needed as well as trends of state of calcareous Carpinus-Quercus forests are nesessary.  Taxonomic research is needed to clarify the phylogenetic relations of European,  American and Japan populations.

No use or trade is known.

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