This mobile app is a tool for assessing the status of nitrogen in your area by surveying lichen on trees. By identifying the presence or absence of 9 nitrogen sensitive and 8 non-sensitive lichens on tree trunks and branches you can get an estimate of how polluted your area is.
Excess nitrogen can cause eutrophication and acidification effects on semi-natural ecosystems, which in turn can lead to species composition changes and other deleterious effects. Species adapted to low nitrogen (N) availability are at a greater risk from this effect including many slow-growing species, notably lichens and mosses.
Lichens are composite organisms comprising a symbiotic relationship between a single species of fungus and one or more species of algae. The fungal partner provides structure and protection for the algae, which through photosynthesis provides energy and assimilates for the fungal partner.
As organisms without roots, lichens obtain their nutrients from the atmosphere and so are highly susceptible to changes in atmospheric chemistry.
Recent research on oak and birch trees across the UK has identified lichens that are sensitive to, or tolerant of, increasing concentrations of nitrogen pollutants in the atmosphere. In the field, the response to increasing atmospheric nitrogen pollution can be measured by the decrease in N-sensitive lichens and the increase in N-tolerant lichens.
Emphasis has been placed on the use of indicator lichens that do not require identification at the microscopic level and that are least likely to be confused with other species. In some cases, all species in a genus are known to be sensitive (e.g. species of Usnea – the beard lichens). In other cases, an individual species within a genus may be an indicator (e.g. Lecidella elaeochroma).
Includes a simple identification key to epiphytic lichens growing on oak and birch trees that show distinct sensitivity to, or tolerance of, atmospheric N pollution.
Provides a simple robust method to determine levels of risk to a habitat from gaseous nitrogen pollution by calculating a standardised nitrogen air quality index (NAQI).
Indicates nitrogen air quality at the location of the trees sampled.
Guide to using a lichen-based index to assess nitrogen air quality
Impacts of air pollution on Lichens and Bryophytes
Nitrogen deposition
This app was developed by the BRC mobile development team. For suggestions and improvements please do not hesitate to contact us.