Can ammonia tolerance amongst lichen functional groups be explained by physiological responses?
Ammonia (NH3) empirical critical levels for Europe were re-evaluated in 2009, based mainly on the ecological responses of lichen communities without acknowledging the physiological differences between oligotrophic and nitrophytic species. Here, we compare a nitrogen sensitive lichen (Evernia prunastri) with a nitrogen tolerant one (Xanthoria parietina), focussing on their physiological response (Fv/Fm) to short-term NH3 exposure and their frequency of occurrence along an NH3 field gradient. Both frequency and Fv/Fm of E. prunastri decreased abruptly above 3 μg m(-3) NH3 suggesting direct adverse effects of NH3 on its photosynthetic performance. By contrast, X. parietina increased its frequency with NH3, despite showing decreased capacity of photosystem II above 50 μg m(-3) NH3, suggesting that the ecological success of X. parietina at ammonia-rich sites might be related to indirect effects of increased nitrogen (NH3) availability. These results highlight the need to establish NH3 critical levels based on oligotrophic lichen species.
Universidade de Lisboa, Faculdade de Ciências, Centro de Biologia Ambiental, Campo Grande, Bloco C2, 1749-016 Lisboa, Portugal. Electronic address: silvana.munzi@gmail.com.
S
S
Munzi
Universidade de Lisboa, Faculdade de Ciências, Centro de Biologia Ambiental, Campo Grande, Bloco C2, 1749-016 Lisboa, Portugal.
C
C
Cruz
Universidade de Lisboa, Faculdade de Ciências, Centro de Biologia Ambiental, Campo Grande, Bloco C2, 1749-016 Lisboa, Portugal.
C
C
Branquinho
Universidade de Lisboa, Faculdade de Ciências, Centro de Biologia Ambiental, Campo Grande, Bloco C2, 1749-016 Lisboa, Portugal; Centre for Natural Resources and the Environment, Instituto Superior Técnico, Universidade de Lisboa (CERENA-IST-UL), Av. Rovisco Pais, 1049-001 Lisboa, Portugal.
P
P
Pinho
Centre for Ecology & Hydrology, Edinburgh, Bush Estate, Penicuik EH26 0QB, UK.
I D
ID
Leith
Centre for Ecology & Hydrology, Edinburgh, Bush Estate, Penicuik EH26 0QB, UK.
L J
LJ
Sheppard
D000222:Adaptation, Physiological / Q000502:physiology*; D000393:Air Pollutants / Q000032:analysis / Q000633:toxicity*; D000641:Ammonia / Q000032:analysis / Q000633:toxicity*; D001203:Ascomycota / Q000502:physiology*; D004784:Environmental Monitoring / Q000379:methods; D005060:Europe; D008011:Lichens / Q000187:drug effects / Q000502:physiology*; D009584:Nitrogen / Q000032:analysis / Q000633:toxicity; D010788:Photosynthesis / Q000187:drug effects
D000393:Air Pollutants; D000641:Ammonia; D009584:Nitrogen
Critical levels; Environmental protection policy; Evernia prunastri; Nitrogen; Xanthoria parietina