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Responses of epiphytic lichens to an experimental whole-tree nitrogen-deposition gradient
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. (Arcum)
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
2010 (English)In: New Phytologist, ISSN 0028-646X, E-ISSN 1469-8137, Vol. 188, no 4, 1075-1084 p.Article in journal (Refereed) Published
Abstract [en]

• Here, we examined the responses of the epiphytic lichens Alectoria sarmentosa and Platismatia glauca to increased atmospheric nitrogen (N) deposition in an old-growth boreal spruce forest, to assess the sensitivity of these species to N and define their critical N load. • Nitrogen deposition was simulated by irrigating 15 trees over a 3 yr period with water and isotopically labeled NH(4) NO(3) , providing N loads ranging from ambient to 50 kg N ha(-1)  yr(-1) . • Thallus N concentration increased in both species with increasing N load, and uptake rates of both NH(4) (+) and NO(3) (-) were similar. Photobiont concentration increased linearly with increased N in both species, saturating in A. sarmentosa in the third year at the highest N loads (25 and 50 kg ha(-1 ) yr(-1) ). The simulated N deposition decreased the phosphorus (P) concentration in A. sarmentosa, and increased the N : P ratio in both species. • Significant responses in lichen chemistry were detected to inputs of 12.5 kg N ha(-1)  yr(-1) or higher, suggesting that resources other than N limit lichens at higher N loads. However, the data also suggest that N saturation may be cumulative over time, even at low N.

Place, publisher, year, edition, pages
Wiley , 2010. Vol. 188, no 4, 1075-1084 p.
Keyword [en]
15N-labeled ammonium nitrate, Alectoria sarmentosa, Chla, critical load, lichen sensitivity, phosphorus, latismatia glauca, simulated nitrogen deposition
URN: urn:nbn:se:umu:diva-37620DOI: 10.1111/j.1469-8137.2010.03426.xISI: 000284074900016PubMedID: 20731782OAI: diva2:369416
Available from: 2010-11-10 Created: 2010-11-10 Last updated: 2016-05-20Bibliographically approved
In thesis
1. Epiphytic lichen responses to nitrogen deposition
Open this publication in new window or tab >>Epiphytic lichen responses to nitrogen deposition
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Nitrogen (N) deposition has increased globally over the last 150 years and further increase is predicted for the future. Nitrogen is an important nutrient for lichens, involved in many processes in both photobiont and mycobiont.  However, N can be a stressor, causing many lichens and lichen communities to disappear with increased deposition. The objective of this thesis was to investigate the response of epiphytic lichens to increased N load. This was done by simulating an increased N deposition to lichens in a boreal forest with low background N, including both short term studies with transplanted lichens and long term studies of naturally established lichens. Alectoria sarmentosa was used as a model species for a N-sensitive lichens and Platismatia glauca as a relatively more N-tolerant lichen. Nitrogen deposition was simulated by daily spraying during the growing season with water and isotopically labeled ammonium nitrate (NH4NO3). In Paper I, I found that when N is supplied in realistic doses (equivalent to deposition of 0.6, 6, 12.5, 25 and 50 kg N ha-1), there were no significant differences in uptake of NO3- or NH4+ in either of the lichen species. The results in Paper II indicate that A. samentosa may be limited by phosphorous (P) and not N limited as expected. That study highlights the importance of P, when studying the effects of N deposition, since P can both mitigate and intensify the negative effects of N on epiphytic lichens. Paper III shows that four years of simulated N deposition caused an alteration of the epiphytic lichen community, since A. sarmentosa decreased in the highest N loads (25 and 50 kg ha-1 year-1), Bryoria spp. decreased to 12.5 kg N and higher loads and Hypogymnia physodes decreased over time for all treatments except in 12.5 kg ha-1, where it only decreased during the first treatment year and then increased after 2007.  The abundance of Platismatia glauca increased over time, independent of treatment. As hypothesized, responses to the treatments differed among species, reflecting their different N optima. In paper IV, the effects of N on carbon-based secondary compounds were studied. None of the studied species (P. glauca, A. sarmentosa, Lobaria scrobiculata and Xanthoria aureola) reduced their concentration of secondary compounds during the experimental period, but in P. glauca the concentration of all compounds were significantly lower in N treated thalli compared with control thalli. The results are consistent with a high degree of constitutive defence in three of the four studied lichens, and we conclude that all four studied lichens seem to have a robust chemical defence system despite considerable manipulation of the environmental conditions. However, we don't know if these lichens are able to keep up the high protection level over longer periods comprising a number of years when more new tissue is formed. In conclusion, long term experiments are necessary to understand lichen response to environmental changes.

Place, publisher, year, edition, pages
Umeå: Institutionen för ekologi, miljö och geovetenskap, Umeå universitet, 2011. 25 p.
Lichens, air pollution, nitrogen deposition, phosphorus, growth, chlorophyll a, boreal forest, field experiment, irrigation, carbon based secondary compounds, Lavar, luftföroreningar, alg, svamp, kväve, fosfor, skog
National Category
Research subject
Ecological Botany
urn:nbn:se:umu:diva-43751 (URN)978-91-7459-232-0 (ISBN)
Public defence
2011-06-01, Älgsalen, Uminova Science Park, Tvistevägen 48, Umeå, 10:00 (English)
Available from: 2011-05-11 Created: 2011-05-09 Last updated: 2011-05-11Bibliographically approved

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