Lichen Biodeterioration at Inscription Rock, El Morro National Monument, Ramah, New Mexico, USA

El Mono National Monument is located in Cibola County, New Mexico, about 200 km west of Albuquerque, New Mexico. The main attraction at the Monument is Inscription Rock, a large sandstone formation which has become a natural repository for more than 700 years of comments and notations recorded by travelers through the region. Recently, encroachment of lichens onto several inscription panels has been documented. Because lichens are known to decompose rock surfaces physically and chemically, lichen communities on several panels have been studied. Species and relative abundance data have been compiled. Distribution of lichen species on each panel has been photographically documented in order to monitor future growth/encroachment trends, exfoliation patterns, and changes in species composition. Samples of common lichen species on the Inscription Rock panels were collected from a large, separate boulder field north of the Rock. These samples have been analyzed using thin-layer chromatography and SEM and light microscopy. PIXE analysis was also performed on Usnea hirta samples from five locations in the Monument to determine if air pollution is influencing substrate degradation patterns. Since establishment of the Monument, protection from grazing and wood cutting/gathering has resulted in changes in the microenvironment in and around several of the panels. SEM and light microscopy analysis have shown that mycobiont hyphae regularly penetrate up to 20mm into rock surfaces. TLC analysis has shown that virtually all the major lichen species on the panels produce at least 4–5 secondary chemicals including several organic acids. Elemental analysis data from Usnea hirta samples confirm that all potential pollutant elements are well within background levels. Preemptive recommendations include: 1) continue to monitor growth plots; 2) set up biocide studies; and 3) selectively remove the woody vegetation adjacent to some panels.