LICHENS OF SOIL CRUST COMMUNITIES IN THE INTERMOUNTAIN AREA OF THE WESTERN UNITED-STATES

Lichens are common components of microbiotic soil crusts. A total of 3 4 species from 17 genera are reported from soil crust communities thro ughout the Intermountain Area. Distribution of terricolous lichens is determined by various physical and biological factors: physical and ch emical characteristics of the soil, moisture regimes, temperature, ins olation, and development and composition of the vascular plant communi ty. Some species demonstrate a broad ecological amplitude while others have a more restricted distribution. All growth forms are represented ; however, the vast majority of soil crust lichens are squamulose (min utely foliose). Fruticose species are least abundant. In exposed, midd le-elevation sites vagrant (detached) species are common. This paper d escribes and discusses terricolous lichen communities of desert habita ts of the intermountain western United States. Effects of various huma n-related activities including grazing, wildfire, air pollution, and r ecreation vehicles on soil crust lichens are discussed. Gypsoplaca mac rophylla (Zahlbr.) Timdal, a rare squamulose lichen which occurs on gy psifersous soils, was recently collected in Emery County, Utah, and is reported as new to the state.