Ammonia (NH3)

Lichen Diversity (Verein Deutscher Ingenieure (VDI) method)


The VDI approach is a standardized German method that was devised to assess changes in lichen communities over wide geographical areas in order to assess the influence of air pollution in Central Europe. The method is based on the frequency of occurrence of selected widespread lichen species within a unit area on selected tree trunks.

Lichen Diversity (Lichens on twigs method)


Twigs provide a new substrate every year and colonising lichen communities are strongly affected by existing climatic and atmospheric conditions as well as by availability of propagules. Data on lichen diversity from a standard sampling procedure along woodland and or hedgerow margins allows a comparison of lichen communities in the vicinity of a range of environmental conditions, particularly those associated with agricultural conditions. The procedure is repeatable allowing an assessment of changes over time.

Lichen Acidophyte-Nitrophyte Diversity (Dutch method)


Lichen diversity and cover is assessed on trunks of specified trees and weighted according to selected species that are classified as "nitrophytes" (species preferring nitrogen enriched tree bark) or "acidophytes" (species preferring naturally acidic clean tree bark). The method was developed in the Netherlands based on large-scale monitoring in conjunction with physicochemical measurements (van Herk 1999, 2002).

Frost Hardiness (Nitrogen)


The ability of plants to minimise the risk of freezing damage is conferred by sychronising their phenology with the growing environment. The indigenous flora generally has a good safety margin between its frost hardened status and minimum temperatures, unless the growth environment changes. A negative link between enhanced N deposition and reduced frost hardiness was widely suspected to be a casual factor in the observed decline of red spruce in the nineteen eighties (Eagar & Adams 1992).

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