The Critical levels of atmospheric ammonia in a Mediterranean holm-oak forest in North-Eastern Spain
Aguillaume Rodríguez-O'connor, Laura (Centre de Recerca Ecològica i d'Aplicacions Forestals)
Àvila i Castells, Anna (Centre de Recerca Ecològica i d'Aplicacions Forestals)
Pinho, Pedro (Universidade de Lisboa. Centro de Ecologia, Evolução and Environmental Changes)
Matos, Paula (Universidade de Lisboa. Centro de Ecologia, Evolução and Environmental Changes)
Llop, Esteve (Universitat de Barcelona. Departament de Biologia Evolutiva, Ecologia i Ciències Ambientals)
Branquinho, Cristina (Universidade de Lisboa. Centro de Ecologia, Evolução and Environmental Changes)

Data:	2017
Resum:	Despite recent regulations, atmospheric ammonia (NH₃) emissions have not changed much over the last decades and excessive nitrogen remains as one of the major drivers for biodiversity changes. To prevent deleterious effects on species and ecosystems, it is very important to establish safety thresholds, such as those defined by the Critical Level (CLE) concept, "the concentration above which direct adverse effects on receptors may occur, based on present knowledge. " Empirical critical levels of atmospheric NH₃ have mainly been reported for temperate forests and there is a lack of information for Mediterranean forests. Here, we provide a case study on NH₃ CLEs for a typical Mediterranean ecosystem, the holm-oak (Quercus ilex) forest. To derive the CLE value, we measured NH₃ concentrations for 1 year at a distance gradient in the forest surrounding a point source (cattle farm) and used diversity changes of lichen functional groups to indicate the onset of adverse effects. We estimate a NH₃ CLE threshold of 2. 6 μg m⁻³, a value that is higher than that reported in other Mediterranean ecosystems and suggests that the site has been already impacted by NH₃ pollution in the past. In a more general context, this study confirms the validity of lichen functional groups to derive CLEs in Mediterranean forests and woodlands and contribute to the body of knowledge regarding the impacts of NH₃ on ecosystems.
Ajuts:	Ministerio de Ciencia e Innovación CGL2009-13188-C03-01 Ministerio de Ciencia e Innovación CSD2008-00040
Nota:	Altres ajuts: PM would like to thank COSTAction FP0903 for financial support of a short-term scientific mission through contract ECOST-STSM-FP0903-120912-019761. PM, PP, and CB acknowledge FCT-MEC support by contracts BD/51419/2011, BPD/75425/2010, and Investigador FCT. The comments of one reviewer are greatly appreciated.
Drets:	Tots els drets reservats.
Llengua:	Anglès
Document:	Article ; recerca ; Versió acceptada per publicar
Matèria:	Critical levels ; Ammonia ; Ecological indicators ; Lichen functional groups ; Mediterranean ; Quercus ilex forest ; N pollution
Publicat a:	Water, air, & soil pollution, Vol. 228, issue 3 (March 2017) , p. 93-222017, ISSN 0049-6979

DOI: 10.1007/s11270-017-3286-8

Post-print 39 p, 752.9 KB

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