| 1. |
- Asplund, Johan, et al.
(författare)
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Simulated nitrogen deposition influences gastropod grazing in lichens
- 2010
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Ingår i: Ecoscience. - : Informa UK Limited. - 1195-6860. ; 17:1, s. 83-89
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Tidskriftsartikel (refereegranskat)abstract
- Lichens are often important photosynthetic organisms in oligotrophic environments where high-quality fodder plants are rare. A strong herbivore defence and/or low nutritional quality allows the accumulation of a high lichen biomass in such areas. However, it is not known how N deposition influences lichen palatability. This study analyzes possible changes in gastropod grazing preference after 3 months simulated N deposition on 3 foliose (Lobaria scrobiculata, Platismatia glauca, and Xanthoria aureola) and 1 pendulous lichen species (Alectoria sarmentosa). Lichens were daily irrigated in the field with rainwater containing 1.625 mM NH4NO3 from June to September, equivalent to a deposition of 50 kg N·ha-1·y-1. Irrigations applied at night, morning, or noon simulated different C-gain regimes. Afterwards in the lab, we offered 2 common lichen-feeding gastropods the choice between N-fertilized thalli and control thalli irrigated with artificial rainwater. The gastropods clearly preferred the unfertilized thalli of the 3 foliose species. For the pendulous A. sarmentosa, the gastropods preferred N-enriched thalli (irrigated at night) to controls. In conclusion, N-enrichment changes the palatability of lichens in species-specific ways.
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| 2. |
- Johansson, Otilia, 1979-
(författare)
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Epiphytic lichen responses to nitrogen deposition
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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| 3. |
- Johansson, Otilia, 1979-, et al.
(författare)
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Lichen responses to nitrogen and phosphorus additions can be explained by the different symbiont responses
- 2011
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Ingår i: New Phytologist. - : Wiley. - 0028-646X .- 1469-8137. ; 191:3, s. 795-805
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Tidskriftsartikel (refereegranskat)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 N2-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.
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| 4. |
- Johansson, Otilia, et al.
(författare)
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Nitrogen deposition drives lichen community changes through differential species responses
- 2012
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Ingår i: Global Change Biology. - : Wiley-Blackwell. - 1354-1013 .- 1365-2486. ; 18:8, s. 2626-2635
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Tidskriftsartikel (refereegranskat)abstract
- Nitrogen (N) deposition has increased globally over the last 150 years and further increases are predicted. Epiphytic lichens decline in abundance and diversity in areas with high N loads, and the abundance of lichens decreases along gradients of increased deposition. Thus, although N is an essential nutrient for lichens, excessive loads may be detrimental for them. However, these gradients include many correlated pollutants and the mechanisms behind the decline are thus poorly known. The aim of this study was to assess effects of N deposition, alone, on the epiphytic lichen community composition in a naturally N-poor boreal forest. For this purpose, whole spruce trees were fertilized daily with N at five levels, equivalent to 0.6, 6, 12.5, 25, and 50 kg N ha-1 yr-1, during four consecutive growing seasons (20062009), and changes in the abundance of lichens were monitored each autumn from the preceding year (2005). The studied lichen communities were highly dynamic and responded strongly to the environmental perturbation. N deposition detectably altered the direction of succession and reduced the species richness of the epiphytic lichen communities, even at the lowest fertilization application (6 kg N ha-1 yr-1). The simulated N deposition caused significant changes in the abundance of Alectoria sarmentosa, Bryoria spp., and Hypogymnia physodes, which all increased at low N loads and decreased at high loads, but with species-specific optima. The rapid decline of A. sarmentosa may have been caused by the added nitrogen reducing the stability of the lichen thalli, possibly due to increases in the photobiont: mycobiont ratio or parasitic fungal attacks. We conclude that increases in nitrogen availability, per se, could be responsible for the reductions in lichen abundance and diversity observed along deposition gradients, and those community responses may be due to physiological responses of the individual species rather than changes in competitive interactions.
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| 5. |
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| 6. |
- Johansson, Otilia, et al.
(författare)
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Responses of epiphytic lichens to an experimental whole-tree nitrogen-deposition gradient
- 2010
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Ingår i: New Phytologist. - : Wiley. - 0028-646X .- 1469-8137. ; 188:4, s. 1075-1084
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Tidskriftsartikel (refereegranskat)abstract
- • 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.
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| 7. |
- Johansson, Otilia
(författare)
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Skogsskador till följd av våtmarkskalkning: omfattning och orsaker
- 2004
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Kalkningen av vattendrag expanderade kraftigt i slutet på 1980-talet och i början på 1990- talet. Våtmarkskalkning visade sig vara den effektivaste metoden för att höja pH-värdet i försurade vattendrag och blev snabbt den mest använda metoden. Redan i detta skede varvegetationsskador på myrarna en välkänd bieffekt. Främst drabbades vitmossan som i det närmaste utrotades inom spridningsområdena. Kunskapen kring urvalet av lämpligakalkningsobjekt var tyvärr underutvecklad genom stora delar av expansionsfasen, vilket innebar att såväl olämpliga som onödigt stora områden kom att kalkas.Under 1990-talet skedde en successiv kunskapsuppbyggnad avseende urval av lämpliga spridningsytor och beräkning av arealdoser. Samtidigt ökade också medvetenheten avseendebehovet att minimera de negativa effekterna på vegetationen och för att minska olägenheternaför jägare och det rörliga friluftslivet. Övergång från kalkmjöl till granulerad kalk var ett mycket viktigt steg. Västerbotten var föregångslän och genomförde övergången redan 1997. I och med användandet av granuler så undveks påverkan på kantzonerna runt de kalkade våtmarkerna. Dessutom reducerades olägenheterna för jägare och bärplockare till ett minimum.Hösten 2000 kontaktades Länsstyrelsen av en markägare som berättade att det fanns skadade tallar på och i anslutning till Jämmerdalsmyran, som är en kalkad våtmark i Umeå kommun. En utredning initierades i form av ett examensarbete som utfördes av Otilia Johansson,student på Mark- och miljöprogrammet vid Skogshögskolan (SLU) i Umeå. Handledare för utredningen var Peter Högberg som är professor vid institutionen för skogsekologi på SLU i Umeå. Utredningen visade att de skadade träden led av borbrist. Bristen på bor var en effekt av den pH-höjning som kalken åstadkommit i marken.Under hösten 2002 genomförde Länsstyrelsen en länsomfattande inventering av skogsskador i anslutning till kalkade våtmarker. Inventeringen genomfördes av Otilia Johansson. I föreliggande rapport redovisas resultaten. Resultaten ska utgöra underlag dels för åtgärder som syftar till att minimera skadorna och dels för de påbörjade diskussionerna om ekonomiskkompensation till drabbade markägare.
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| 8. |
- Nybakken, Line, et al.
(författare)
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Defensive compound concentration in boreal lichens in response to simulated nitrogen deposition
- 2009
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Ingår i: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486. ; 15:9, s. 2247-2260
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Tidskriftsartikel (refereegranskat)abstract
- Nitrogen (N) deposition is expected to increase in northwestern Europe the next 50–100 years. The effects of higher N availability on lichens will presumably depend on their capacity to acquire carbon (C), that is, of the timing and duration of the wet and active state. If lichens respond like plants, their C and N status may affect their concentration of carbon-based secondary compounds (CBSCs), and thus their defence against herbivores, detrimental radiation, pathogens and parasites. In the present study we have manipulated N availability and timing and duration of the metabolically active state by spraying lichen transplants in an old spruce forest with rainwater or rainwater with added N corresponding to 50 kg N ha−1 yr−1. The spraying was applied either at night, in the morning or at noon to also investigate the effect of timing and duration of the active state. Concentrations of N, chlorophyll a (Chl a) and CBSCs were measured before and after one summer's spraying of 10 thalli in each of four different lichen species; Alectoria sarmentosa, Lobaria scrobiculata, Platismatia glauca, and Xanthoria aureola. The added N was readily taken up by all the lichen species. A. sarmentosa, P. glauca, and X. aureola increased their Chl a concentration in response to increased N, while L. scrobiculata increased Chl a in response to increased active time. None of the studied species 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 those that got only rainwater. The results are consistent with a high degree of constitutive defence in three of four species, and we conclude that all the investigated lichens seem to have rather robust chemical defence systems despite considerable manipulation of the environmental conditions.
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