Quantification of Branch Dwelling Lichens for the Detection of Air Pollution Impact

Abstract

In the Athabasca Oil Sands area of Alberta, a study was carried out to test a lichen community transplant technique and to determine the influence of oil sands extraction and processing emissions on lichen cover of transplanted communities. Measurement errors of a photographic technique for the determination of lichen cover were dependent upon lichen species but were not correlated to lichen cover. When lichen covers were small therefore, relative errors were very large. Changes in cover of naturally occurring lichen communities on black spruce branches were not significant over a four-year period. Lichen communities transplanted under jack pine and white spruce trees had cover changes with time not different from naturally occurring communities even over a period of years.

Significant (P<0.001) cover reductions of some lichen groups occurred on transplanted branches under white spruce within 8–3 km of a pollution source. Evernia, Cetraria, and Bryoria groups were reduced whereas Hypogymnia showed no response over a 3 year measurement period. Reductions in lichen cover were greater than the demonstrated precision of the technique.