title: Lichen responses to nitrogen and phosphorus additions can be explained by the different symbiont responses.
abstract: • Responses to simulated nitrogen (N) deposition with or without added phosphorus (P) were investigated for three contrasting lichen species - the N-sensitive Alectoria sarmentosa, the more N-tolerant Platismatia glauca and the N(2) -fixing Lobaria pulmonaria- in a field experiment. • To examine whether nutrient limitation differed between the photobiont and the mycobiont within the lichen, the biomass responses of the respective bionts were estimated. • The lichenized algal cells were generally N-limited, because N-stimulated algal growth in all three species. The mycobiont was P-limited in one species (A. sarmentosa), but the growth response of the mycobionts was complex, as fungal growth is also dependent on a reliable carbon export from the photobiont, which may have been the reason for the decrease of the mycobiont with N addition in P. glauca. • Our findings showed that P availability was an important factor when studying effects of N deposition, as P supply can both mitigate and intensify the negative effects of N on epiphytic lichens.
authors.affiliation: Department of Ecology and Environmental Science, Umeå University, SE-901 87 Umeå, Sweden.
authors.forename: Otilia
authors.initials: O
authors.lastname: Johansson
authors.affiliation: Department of Ecology and Environmental Science, Umeå University, SE-901 87 Umeå, Sweden.
authors.forename: Johan
authors.initials: J
authors.lastname: Olofsson
authors.affiliation: Climate Impacts Research Centre, Department of Ecology and Environmental Science, Umeå University, SE-981 07 Abisko, Sweden.
authors.forename: Reiner
authors.initials: R
authors.lastname: Giesler
authors.affiliation: Department of Ecology and Environmental Science, Umeå University, SE-901 87 Umeå, Sweden.
authors.forename: Kristin
authors.initials: K
authors.lastname: Palmqvist
mesh_terms: D002734:Chlorophyll / Q000378:metabolism; D005658:Fungi / Q000254:growth & development / Q000502:physiology*; D008011:Lichens / Q000254:growth & development / Q000378:metabolism / Q000502:physiology*; D009584:Nitrogen / Q000032:analysis / Q000378:metabolism*; D010758:Phosphorus / Q000032:analysis / Q000378:metabolism*; D010788:Photosynthesis; D013548:Sweden; D013559:Symbiosis
chemical_list: D002734:Chlorophyll; D010758:Phosphorus; D009584:Nitrogen