Two lichenological studies were conducted in the Montricher forests, one on lignicolous lichens of stumps in 2005 and the other on lichens of the different forest types in 2015. The synthesis of the two allows to establish a reference state of forest lichen diversity between 750 and 1 570 m in altitude. 215 species of lichens are documented, two of which are mentioned for the first time in Switzerland, Absconditella sphagnorum and Agonimia repleta, and 26 for the first time in the canton of Vaud. The presence of 20 priority species, 12 of which are related to old trees, gives the massif a cantonal or even national importance for their conservation. An increase in the diversity of lichens as a function of altitude is noted, at a rate of 6.9 species per 100 m. Several hypotheses explaining the causes are discussed, evoking the importance of humidity, light and the age of the trees. The existence of old forests, indicated by certain lichen species, is also discussed. The comparison of surveys in managed forests, in forest reserves with active managements and in forest reserves with minimum intervention allows some conclusions on measures favouring lichens in the forest.