Lichen biomonitoring in Northern Utah

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McKenna G. Delton, Botany & Plant Ecology, Weber State University, Ogden, UT; Wildland Resources, Utah State University, Logan, UT and Heather Root, Department of Botany, Weber State University, Ogden, UT

Background/Question/Methods

Nitrogen pollution is a well-documented cause of ecological harm. Lichens have often been used as bioindicators of air pollution, in which concentrations in the thallus are correlated to atmospheric levels. This is an inexpensive alternative to air monitors. However, this type of biomonitoring in the arid western United State has virtually no precedent; other regions with well-developed biomonitoring programs experience a higher percent of pollutant deposition in wet forms. Therefore, it is unknown how bioindicators accumulate pollutants in this region. In the following, nitrogen concentrations were experimentally manipulated through the deposition of ammonium nitrate in wet and dry forms. Branches covered in two species of Xanthomendoza were collected from the foothills of the Wasatch mountains near Ogden, Utah. The branches were then moved to an outdoor site nearby and treated with nitrogen (N) for 13 weeks. An equal amount of ammonium nitrate was added to two treatment groups in wet and dry forms in addition to inert mineral dust which was also used as a dry control. After the treatment period, the lichens were cleaned from the branches and processed using elemental combustion analysis in which percent total N by dry weight was determined.
Results/Conclusions:
The mean total N in the dry control group was 2.4% with the highest value being 2.7% N dw. The mean total N in the dry treatment group was 2.8% with the max % N dw being 3.3%. The mean wet control was 2.6% N dw and the highest value 3.9%, while the wet treatment mean was 2.8% with the highest value being 3.1% N dw. After conducting a Kruskal Wallis one way analysis of variance it was determined that there was no statistically significant difference in N between all 4 treatment groups - this suggests that lichens accumulated the same amount of nitrogen under both wet and dry conditions. If these results are found consistently, it will mean that the mechanism (wet or dry) of nitrogen deposition does not impact how much total N lichen bioindicators accumulate. Much is still unknown about this topic and other methods will need to be explored to determine why lichens in this region correlate poorly to air monitors. However, the dry treatment group did accumulate significant amount of N when compared to the control. This is promising, as it shows that this species could be used to indicate N pollution under dry deposition.