Patterns of species distribution in an Umbilicaria dominated community

Abstract

Cliff and rock outcrop communities of which Umbilicaria lichens form a major component are described. In each of 210 sample sites in central Ontario [Canada], subjective estimates of species abundance were made together with measures of slope, aspect and exposure. Many species have specific requirements for slope and exposure. The significance of the observed patterns is discussed with respect to the known physiology of the Umbilicaria spp.