The urban heat island effect and its impact on lichen abundance and diversity in Jefferson County, Kentucky

Austin Adam

Abstract


For the past century, it has been widely accepted that air pollution (such as SOx and NOx) causes lichen mortality in urban areas. In recent years, however, the Urban Heat Island Effect (UHI) has been explored as a possible cause of lichen mortality. Lichens are the result of a unique symbiotic relationship between fungi and a photosynthesizing partner. One of the benefits obtained from the fungus partner is water retention. The UHI also affects the amount of air moisture, as increased impervious surfaces are found. Areas with less impervious surface cover, and therefore more air moisture, theoretically, should have higher species richness and abundance. In this study, six sites were chosen around Jefferson County in Kentucky. Air temperature and humidity data were obtained from each site along with the abundance and diversity of lichen species. Species richness was performed by the rubber band and circle method on six trees at each of the eight sites. Abundance values were obtained by using only the rubber band method. Both the Shannon and Simpson indices were calculated and compared for each site. Our results suggest that lichen species richness increases with increasing temperature in Jefferson County, and that species richness decreases with increasing air humidity. This is the opposite of what we expected to find. Analysis of Shannon’s index shows that species richness and evenness decrease with increased air temperature and increases with increased air humidity, which we expected to find. However, analysis of the Simpson index shows that diversity increases with increasing air temperature, and decreases with increasing air humidity. Our findings highlight the need for more studies investigating the impacts of UHI on local ecosystem health.


Keywords


Lichen; Urban Heat Island; Louisville

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