Epiphytic Lichens of a Ponderosa Pine Forest in Southeastern Montana

Nineteen lichen species were collected from Pinus ponderosa Dougl. in Custer National Forest in southeastern Montana; 340 trees in four vegetation types were sampled. The dominant lichen species at all heights of the trunks and on lower branches was Usnea hirta (L.) Wigg., constituting 31-74% of total lichen cover. The percentage of U. hirta was highest in the driest vegetation type (P. ponderosa-Agropyron spicatum) and lowest in the most moist vegetation type (P. ponderosa-Prunus virginiana). The majority of lichen cover and diversity on tree trunks was on the lowest 50 cm; diversity and cover increased with ascending moisture levels. Parmeliopsis ambigua (Wulf.) Nyl., Bryoria fuscescens (Gyeln.) Brodo & D. Hawksw., and Cetraria pinastri (Scop.) S. Gray increased most substantially from drier to wetter sites. Most of the lichen species found in this forest type are regular components of Rocky Mountain and/or northern coniferous forests. Other conifer forest types in the Rocky Mountains and Black Hills support richer lichen floras.