The influence of the pH of the bark of two tree species belonging at Nothofagus genus on the lichen and bryophyte richness was studied. The tree species considered for this study were: N. dombeyi and N. macracarpa situated in two pre-Andean localities; one in the "Radal Siete Tazas" National Reserve and the other in the "Altos de Lircay" National Reserve, Central Chile. In each locality, a total of 20 phorophytes were examined: 10 N. dombeyi and 10 N. obliqua. In each phorophyte, the total lichens and bryophytes were inventoried, the diameter of each one of the phorophytes was measured at breast height (DHA) and, in addition, 10 g of bark were extracted in order to check the pH. The pH of the bark was determined by means of the Mezger's method (1996) and afterwards related to the lichen and bryophyte richness found in the phorophytes of each tree species sampled in both localities. In both localities, the pH of bark of the N. dombeyi phorophytes was markedly more acidic than the one of the N. obliqua. Statistical analyses show a significant difference between the pH of one species and other. The pH of the barks of N. dombeyi and N. obliqua phorophytes, in both localities, not correlated with the richness of the different groups (lichens, mosses and liverworts). However, according to the inventories carried, it observed that some species of lichens have a close relation with the pH of the bark of one or other of the two tree species studied and only a low percentage of them were indifferent to pH of the phorophytes. The mosses preferred bark with pH near to neutrality such as those of N. obliqua, while the liverworts preferred bark were more acid, such as the ones of N. dombeyi.