KNIGHT, KATHRYN B.*, LARRY L. ST. CLAIR, and JOHN S. GARDNER. M.L. Bean Life Science Museum and Electron Optics Laboratory Brigham Young University Provo UT 84602. - Lichen-mediated degradation of historic and prehistoric panels at El Morro National Mounument, New Mexico.
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