El Morro National Monument is located in Cibola County, New Mexico, about 200 km west of Albuquerque, New Mexico. The main attraction at the Monument is a large sandstone formation called Inscription Rock. The formation is a natural repository for more than 700 years of comments and notations recorded by travelers through the region. In excess of 2000 petroglyphs and inscriptions are preserved on the lower reaches of the rock. Recently, encroachment of lichens onto several, inscription panels has been documented. Because lichens are known to decompose rock surfaces physically and chemically, we are evaluating the impact of lichens on several panels. Species lists and relative abundance data for each panel have been compiled. Distribution of lichen species on each panel has been photographically documented in order to monitor growth/encroachment trends, exfoliation patterns, and changes in species composition. Samples of the major lichen species on the Inscription Rock panels were collected from a large boulder field north of Inscription Rock. These samples are being analyzed using Infrared spectroscopy, thin-layer chromatography, and SEM and light microscopy. These data will be used to evaluate the degree of lichen encroachment and substrate degradation. In addition, PIXE analysis is being performed on five samples of Usnea hirta from five locations in the Monument to determine if air pollution is influencing substrate degradation patterns. Since establishment of the Monument, protection of the local landscape from grazing and wood cutting/gathering has resulted in changes in the microenvironment in and around several of the panels. The effects of these changes are also being considered. Data from this study will be used to evaluate remedial procedures for the control and/or removal of lichens from some panels.

Key words: biodeterioration, lichens