Physiological responses of lichens to factorial fumigations with nitric acid and ozone

This paper addresses the effects of gaseous nitric acid (HNO3) and ozone (O3), two important air pollutants, on six lichen species with different morphological, ecological, and biological characteristics. The treatment chambers were set up in a factorial design consisting of control chambers, chambers fumigated with HNO3, with O3, and with HNO3 and O3, together. Each species showed a different sensitivity to the fumigations, reflecting the physiological variation among species. Our results clearly indicate that HNO3 is a strong phytotoxin to many lichens, and that O3 alone has little effect on the measured parameters. The combined fumigation effects of HNO3 and O3 were not significantly different from HNO3 alone.

► We fumigated 6 lichen species with factorial combinations of nitric acid (HNO3) and ozone (O3).
► Some species were highly sensitive to HNO3 while others were tolerant.
► No species responded significantly to O3.
► The combined fumigation effects of HNO3 and O3 were not significantly different from HNO3 alone.
► HNO3 may play an important role in lichen community composition in areas with high HNO3 pollution.