Nitrogen concentrations in lichens as a proxy for Nitrogen deposition

This study addressed the potential for using lichens as a metric to estimate rates of nitrogen (N) deposition in the Colorado subalpine. I tested the hypothesis that lichen tissue N concentration could be used as a proxy for N deposition in the absence of deposition monitors. To test this hypothesis I conducted two experiments using four species of lichens that occur throughout the subalpine ecosystems of the southern Rocky Mountains. The first experiment measured the changes in lichen N concentration in response to 5 treatment levels of N additions in a greenhouse environment over three months. The second experiment measured lichen tissue N concentration in the vicinity of deposition monitors throughout the Colorado subalpine. For each experiment I used a linear regression to test whether the relationship between N deposition and lichen tissue concentration could be used as a predictive model for N deposition. There was a significant positive relationship between treatment and tissue concentration for Usnea lapponica in the greenhouse experiment. The other three species included in this study showed no correlation. N concentration in Xanthoparmelia coloradoensis showed a significant correlation with measured wet deposition in the field study. The other three species showed no relationship