ELEMENTAL ANALYSIS OF LICHENS FROM THE WESTERN UNITED STATES: DISTRIBUTION OF PHOSPHORUS AND CALCIUM FROM A LARGE DATA SET

Abstract

Lichen samples were collected and observations about lichen communities were recorded at sites in the intermountain western United States. Specifically the states of Idaho, Montana, Wyoming, Nevada, Utah, Colorado, Arizona, and New Mexico were included in this study. The minor and trace-element concentrations in many of the lichens collected were determined by proton induced X-ray emission (PIXE). These data are part of a base line assessment of current air pollution conditions in this region. These data also provide an opportunity to study some aspects of lichen physiology. Using the data from 508 foliose and fruticose lichens, frequency distributions for concentrations of phosphorus and calcium are considered. Phosphorus has a closely-spaced, bimodal distribution: one mode for foliose lichens and one mode for fruticose lichens. This suggests that all lichen genera in this study have similar requirements and absorption mechanisms for phosphorus. Calcium has a complex frequency distribution and concentrations that range from 450 mg/kg to 14 % dry weight. Contributions to this complex distribution pattern can be understood if the data are resolved into growth form, genera within each growth form, and in some cases species within a given genus. This complex dependence on calcium is strong evidence that lichens develop specific calcium-related adaptations in order to accommodate various habitat conditions.