Fifty-two species of lichens were found on Larix lyallii Parl. and Pinus albicaulis Engelm. trees in 31 stands in the subalpine zone of the mountains of southwestern Alberta. The species belong to the following North American distributional elements: 25, Pan Boreal; 13, Arctic Boreal; 8, Cordilleran or Western Boreal; 2, Pan North American; 2, Eastern Boreal; and 1, uncertain.In Larix lyallii, quadrats occupying the lower 30 cm of the trunk were characterized by a Parmeliopsis hyperopta – P. ambigua – Cetraria pinastri union whereas quadrats in a region 40 cm deep, centered at 1.3 m from the base, were occupied by a Letharia californica – Alectoria glabra union. In Pinus albicaulis, the lower quadrats were characterized by a Parmeliopsis ambigua – Cetraria pinastri – Parmeliopsis hyperopta – Lecidea fuscescens union whereas the upper were occupied by a Parmelia sphaerosporella – Letharia californica – Lecanora varia – Alectoria glabra union.Forty-eight species occurred on the smooth to rough, more absorbent, bark of Pinus albicaulis compared with 32 found on the rough bark of Larix lyallii.Succession followed four stages: (1) the invasion of appressed foliose lichens on the tree bases, (2) the appearance of crustose species on the lower four feet of the trunk, (3) the invasion of foliose species on the trunk and branches, and (4) the appearance of fruticose species.
