Local variation of trace element concentrations in Usnea subfloridana
Adams, Matthew David
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A mensurative study into the local variability of trace element concentrations in the lichen Usnea subjloridana was conducted. Samples were collected from an Abies balsamea located in the Thunder B y region away from any known point sources of pollution. One-thousand and thirty-seven samples were collected and individually weighed. These samples were subsequently grouped into 97 grouped samples, based on their aspect, height on the tree, and weight. Elemental concentrations were determined by inductively coupled plasma atomic emission spectroscopy. Data analyses were conducted on AI, B a, Ca, Cd, Cu, Fe, K, Mg, Mn, Na, P, S, Sr, and Zn concentrations. Two main wind directions were present at the study site; lichens were grouped according to which pattern they were nearest when creating the grouped samples. All elements except Mn were significantly different in concentration at p < 0.00 1 between the two aspect groups. Comparison of the variation around the mean for each element's experimental results and the literature values, indicate local variation can be equal to or greater than what has been found in regional studies. Linear regression models suggest that strict guidelines can reduce this variation for some elements. In conclusion it is found that the common practice of low sampling density over large regions may not be a suitable technique because of the large local variation which is seen in this study. Researchers must know the local variability before making quantitative comparisons at a regional level with few samples.