title: Tools for determining critical levels of atmospheric ammonia under the influence of multiple disturbances.
abstract: Critical levels (CLEs) of atmospheric ammonia based on biodiversity changes have been mostly calculated using small-scale single-source approaches, to avoid interference by other factors, which also influence biodiversity. Thus, it is questionable whether these CLEs are valid at larger spatial scales, in a multi- disturbances context. To test so, we sampled lichen diversity and ammonia at 80 sites across a region with a complex land-cover including industrial and urban areas. At a regional scale, confounding factors such as industrial pollutants prevailed, masking the CLEs. We propose and use a new tool to calculate CLEs by stratifying ammonia concentrations into classes, and focusing on the highest diversity values. Based on the significant correlations between ammonia and biodiversity, we found the CLE of ammonia for Mediterranean evergreen woodlands to be 0.69 μg m(-3), below the previously accepted value of 1.9 μg m(-3), and below the currently accepted pan-European CLE of 1.0 μg m(-3).
authors.affiliation: CERENA-Centro de Recursos Naturais e Ambiente, Instituto Superior Técnico, Universidade de Lisboa (CERENA-IST-UL), Av. Rovisco Pais, 1049-001 Lisboa, Portugal; Universidade de Lisboa, Faculdade de Ciências, Centro de Biologia Ambiental (CBA-FC-UL), Portugal. Electronic address: ppinho@fc.ul.pt.
authors.forename: P
authors.initials: P
authors.lastname: Pinho
authors.affiliation: Universidade de Lisboa, Faculdade de Ciências, Centro de Biologia Ambiental (CBA-FC-UL), Portugal; Universtitat de Barcelona, Dpt. Biologia Vegetal-Botànica, Spain.
authors.forename: E
authors.initials: E
authors.lastname: Llop
authors.affiliation: CERENA-Centro de Recursos Naturais e Ambiente, Instituto Superior Técnico, Universidade de Lisboa (CERENA-IST-UL), Av. Rovisco Pais, 1049-001 Lisboa, Portugal.
authors.forename: M C
authors.initials: MC
authors.lastname: Ribeiro
authors.affiliation: Universidade de Lisboa, Faculdade de Ciências, Centro de Biologia Ambiental (CBA-FC-UL), Portugal.
authors.forename: C
authors.initials: C
authors.lastname: Cruz
authors.affiliation: CERENA-Centro de Recursos Naturais e Ambiente, Instituto Superior Técnico, Universidade de Lisboa (CERENA-IST-UL), Av. Rovisco Pais, 1049-001 Lisboa, Portugal.
authors.forename: A
authors.initials: A
authors.lastname: Soares
authors.affiliation: CERENA-Centro de Recursos Naturais e Ambiente, Instituto Superior Técnico, Universidade de Lisboa (CERENA-IST-UL), Av. Rovisco Pais, 1049-001 Lisboa, Portugal.
authors.forename: M J
authors.initials: MJ
authors.lastname: Pereira
authors.affiliation: Universidade de Lisboa, Faculdade de Ciências, Centro de Biologia Ambiental (CBA-FC-UL), Portugal.
authors.forename: C
authors.initials: C
authors.lastname: Branquinho
mesh_terms: D000393:Air Pollutants / Q000032:analysis*; D000641:Ammonia / Q000032:analysis*; D001272:Atmosphere / Q000737:chemistry; D044822:Biodiversity; D004784:Environmental Monitoring / Q000379:methods*; D008011:Lichens / Q000737:chemistry / Q000145:classification
chemical_list: D000393:Air Pollutants; D000641:Ammonia
keywords: Biodiversity; Critical thresholds; Eutrophication; Functional groups; Global change; Nitrogen