Relationships between lichen community composition and concentrations of NO2 and NH3.

The relationship between different features of lichen communities in Quercus robur canopies and environmental variables, including concentrations of NO(2) and NH(3) was investigated. NO(2) concentration was the most significant variable, it was positively correlated with the proportion of lichen cover comprising nitrophytes and negatively correlated with total lichen cover. None of the lichen community features were correlated with NH(3) concentrations, which were relatively low across the site.

Quantifying local traffic contributions to NO2 and NH3 concentrations in natural habitats.

NO(2) and NH(3) concentrations were measured across a Special Area for Conservation in southern England, at varying distances from the local road network. Exceedances of the critical levels for these pollutants were recorded at nearly all roadside locations, extending up to 20 m away from roads at some sites. Further, paired measurements of NH(3) and NO(2) concentrations revealed differences between ground and tree canopy levels.