| 1. |
- Limpens, J., et al.
(författare)
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Glasshouse vs field experiments : do they yield ecologically similar results for assessing N impacts on peat mosses?
- 2012
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Ingår i: New Phytologist. - : Wiley. - 0028-646X .- 1469-8137. ; 195:2, s. 408-418
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Tidskriftsartikel (refereegranskat)abstract
- Peat bogs have accumulated more atmospheric carbon (C) than any other terrestrial ecosystem today. Most of this C is associated with peat moss (Sphagnum) litter. Atmospheric nitrogen (N) deposition can decrease Sphagnum production, compromising the C sequestration capacity of peat bogs. The mechanisms underlying the reduced production are uncertain, necessitating multifactorial experiments. We investigated whether glasshouse experiments are reliable proxies for field experiments for assessing interactions between N deposition and environment as controls on Sphagnum N concentration and production. We performed a meta-analysis over 115 glasshouse experiments and 107 field experiments. We found that glasshouse and field experiments gave similar qualitative and quantitative estimates of changes in Sphagnum N concentration in response to N application. However, glasshouse-based estimates of changes in production even qualitative assessments diverged from field experiments owing to a stronger N effect on production response in absence of vascular plants in the glasshouse, and a weaker N effect on production response in presence of vascular plants compared to field experiments. Thus, although we need glasshouse experiments to study how interacting environmental factors affect the response of Sphagnum to increased N deposition, we need field experiments to properly quantify these effects.
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| 2. |
- Limpens, J., et al.
(författare)
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Climatic modifiers of the response to nitrogen deposition in peat-forming Sphagnum mosses : a meta-analysis
- 2011
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Ingår i: New Phytologist. - : Wiley. - 0028-646X .- 1469-8137. ; 191:2, s. 496-507
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Tidskriftsartikel (refereegranskat)abstract
- Peatlands in the northern hemisphere have accumulated more atmospheric carbon (C) during the Holocene than any other terrestrial ecosystem, making peatlands long-term C sinks of global importance. Projected increases in nitrogen (N) deposition and temperature make future accumulation rates uncertain. Here, we assessed the impact of N deposition on peatland C sequestration potential by investigating the effects of experimental N addition on Sphagnum moss. We employed meta-regressions to the results of 107 field experiments, accounting for sampling dependence in the data. We found that high N loading (comprising N application rate, experiment duration, background N deposition) depressed Sphagnum production relative to untreated controls. The interactive effects of presence of competitive vascular plants and high tissue N concentrations indicated intensified biotic interactions and altered nutrient stochiometry as mechanisms underlying the detrimental N effects. Importantly, a higher summer temperature (mean for July) and increased annual precipitation intensified the negative effects of N. The temperature effect was comparable to an experimental application of almost 4 g N m(-2) yr(-1) for each 1 degrees C increase. Our results indicate that current rates of N deposition in a warmer environment will strongly inhibit C sequestration by Sphagnum-dominated vegetation.
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| 3. |
- Mitchell, E. A. D, et al.
(författare)
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Contrasted effects of increased N and CO2 supply on two keystone species in peatland restoration and implications for global change
- 2002
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Ingår i: Journal of Ecology. - : Wiley. - 0022-0477 .- 1365-2745. ; 90:3, s. 529-533
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Tidskriftsartikel (refereegranskat)abstract
- 1 Significant areas of temperate bogs have been damaged by peat harvesting but may regenerate. These secondary mires, if well managed, may act as strong C sinks, regulate hydrology and buffer regional climate.2 The potential effects of bog regeneration will, however, depend on the successful establishment of the principal peat formers –Sphagnum mosses. The influence of hydrology and microclimate on Sphagnum re-growth is well studied but effects of elevated CO2 and N deposition are not known.3 We carried out two in-situ experiments in a cutover bog during three growing seasons in which we raised either CO2 (to 560 p.p.m.) or N (by adding NH4NO3, 3 g m−2 year−1). The two treatments had contrasting effects on competition between the initial coloniser Polytrichum strictum (favoured by high N) and the later coloniser Sphagnum fallax (favoured by high CO2).4 Such changes may have important consequences for bog regeneration and hence for carbon sequestration in cutover bogs, with potential feedback on regional hydrological and climatic processes.
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| 4. |
- Schenkel, D., et al.
(författare)
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Linking soil's volatilome to microbes and plant roots highlights the importance of microbes as emitters of belowground volatile signals
- 2019
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Ingår i: Environmental Microbiology. - : Blackwell Publishing Ltd. - 1462-2912 .- 1462-2920. ; 21:9, s. 3313-3327
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Tidskriftsartikel (refereegranskat)abstract
- Plants and microbes release a plethora of volatiles that act as signals in plant–microbe interactions. Characterizing soil's volatilome and microbiome might shed light on the nature of relevant volatile signals and on their emitters. This hypothesis was tested by characterizing plant cover, soil's volatilome, nutrient content and microbiomes in three grasslands of the Swiss Jura Mountains. The fingerprints of soil's volatiles were generated by solid-phase micro-extraction gas chromatography/mass spectrometry, whereas high-throughput sequencing was used to create a snapshot of soil's microbial communities. A high similarity was observed in plant communities of two out of three sites, which was mirrored by the soil's volatilome. Multiple factor analysis evidenced a strong association among soil's volatilome, plant and microbial communities. The proportion of volatiles correlated to single bacterial and fungal taxa was higher than for plants. This suggests that those organisms might be major contributors to the volatilome of grassland soils. These findings illustrate that key volatiles in grassland soils might be emitted by a handful of organisms that include specific plants and microbes. Further work will be needed to unravel the structure of belowground volatiles and understand their implications for plant health and development.
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| 5. |
- Mazier, Florence, et al.
(författare)
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Multidisciplinary approach to reconstructing local pastoral activities : an example from the Pyrenean Mountains (Pays Basqueq)
- 2009
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Ingår i: The Holocene. - : SAGE Publications. - 0959-6836 .- 1477-0911. ; 19:2, s. 171-188
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Tidskriftsartikel (refereegranskat)abstract
- In this study archaeology, history and palaeoecology (modern and fossil data sets of pollen and non-pollen palynomorphs) were used to reconstruct small-scale pastoral activities in the Pyrenees Mountain during the last two millennia. Modern pollen assemblages from the major vegetation units (both natural and anthropogenic) are studied on one restricted watershed area. A correlative model (RDA) of 61 modern pollen spectra and 35 external variables distinguishes two groups of taxa, providing information on the nature and spatial extent of human impact on the landscape. The first pool indicates local pastoral activities, and the second one implies regional input from outside the studied watershed, and is not characteristic of a specific land use. These pools are described as 'Local Pastoral Pollen Indicators' (LPPI) for this particular mountain region on crystalline bedrock and 'Regional Human Activities Pollen Indicators' (RHAPI). The modern data set is used to aid interpretation of the local pollen sequence of Sourzay that covers the last 2000 calendar years BP, using RDA reconstructions, and best modern analogues as a means of comparing modern and fossil spectra. The study also demonstrates agreement between the independent interpretations of two fossil proxies, LPPI and corophilous fungi.
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| 6. |
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| 7. |
- Berendse, F, et al.
(författare)
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Raised atmospheric CO2 levels and increased N deposition cause shifts in plant species composition and production in Sphagnum bogs
- 2001
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Ingår i: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486. ; 7:5, s. 591-598
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Tidskriftsartikel (refereegranskat)abstract
- Part of the missing sink in the global CO2 budget has been attributed to the positive effects of CO2 fertilization and N deposition on carbon sequestration in Northern Hemisphere terrestrial ecosystems. The genus Sphagnum is one of the most important groups of plant species sequestrating carbon in temperate and northern bog ecosystems, because of the low decomposability of the dead material it produces. The effects of raised CO2 and increased atmospheric N deposition on growth of Sphagnum and other plants were studied in bogs at four sites across Western Europe. Contrary to expectations, elevated CO2 did not significantly affect Sphagnum biomass growth. Increased N deposition reduced Sphagnum mass growth, because it increased the cover of vascular plants and the tall moss Polytrichum strictum. Such changes in plant species composition may decrease carbon sequestration in Sphagnum-dominated bog ecosystems.
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| 8. |
- Mazier, Florence, et al.
(författare)
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Pollen productivity estimates and relevant source area of pollen for selected plant taxa in a pasture woodland landscape of the Jura Mountains (Switzerland)
- 2008
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Ingår i: Vegetation History and Archaeobotany. - : Springer Science and Business Media LLC. - 0939-6314 .- 1617-6278. ; 17:5, s. 479-495
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Tidskriftsartikel (refereegranskat)abstract
- Abstract in UndeterminedRelevant source area of pollen (RSAP) and pollen productivity for 11 key taxa characteristic of the pasture woodland landscape of the Jura Mountains, Switzerland, were estimated using pollen assemblages from moss polsters at 20 sites. To obtain robust pollen productivity estimates (PPEs), we used vegetation survey data at a fine spatial-resolution (1 x 1 m(2)) and randomized locations for sampling sites, techniques rarely used in palynology. Three Extended R value (ERV) submodels and three distance-weighting methods for plant abundance calculation were applied. Different combinations of the submodels and distance-weighting methods provide slightly different estimates of RSAP and PPEs. Although ERV submodel 1 using 1/d (d = distance in meters) best fits the dataset, PPE values for heavy pollen types (e.g. Abies) were sensitive to the method used for distance-weighting. Taxon-specific distance-weighting methods, such as Prentice's model, emphasize the intertaxonomic differences in pollen dispersal and deposition, and are thus theoretically sound. For the dataset obtained in this project, Prentice's model was more appropriate than other distance-weighting methods to estimate PPEs. Most of the taxa have PPEs equal to (Fagus, Plantago media and Potentilla-type), or higher (Abies, Picea, Rubiaceae and Trollius europaeus) than Poaceae (PPE = 1). Acer, Cyperaceae, and Plantago montana-type are low pollen producers. This set of PPEs will be useful for reconstructing heterogeneous, mountainous pasture woodland landscapes from fossil pollen records. The RSAP for moss polsters in this semi-open landscape region is ca. 300 m.
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| 9. |
- Mitchell, EAD, et al.
(författare)
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Relationships among testate amoebae (Protozoa), vegetation and water chemistry in five Sphagnum-dominated peatlands in Europe
- 2000
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Ingår i: New Phytologist. - : Wiley. - 0028-646X .- 1469-8137. ; 145:1, s. 95-106
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Tidskriftsartikel (refereegranskat)abstract
- To study the relationships between groups of organisms and the degree to which these relationships are consistent across major climatic gradients, we analysed the testate amoeba (Protozoa) communities, vegetation and water chemistry of one peatland in five countries: Switzerland, The Netherlands, Great Britain, Sweden and Finland, as part of the BERI (Bog Ecosystem Research Initiative) project. The relationships between the different data sets and subsets were investigated by means of detrended correspondence analysis, canonical correspondence analysis and Mantel permutation tests. The comparison of data on vegetation and testate amoebae showed that inter-site differences are more pronounced for the vegetation than for the testate amoebae species assemblage. Testate amoebae are a useful tool in multi-site studies and in environmental monitoring of peatlands because: (1) the number of species in Sphagnum-dominated peatlands is much higher than for mosses or vascular plants; (2) most peatland species are cosmopolitan in their distributions and therefore less affected than plants by biogeographical distribution patterns, thus differences in testate amoeba assemblages can be interpreted primarily in terms of ecology; (3) they are closely related to the ecological characteristics of the exact spot where they live, therefore they can be used to analyse small-scale gradients that play a major role in the functioning of peatland ecosystems. This study revealed the existence of small-scale vertical gradients within the vegetation and life-form niche separation in response to water chemistry. The deep-rooted plants such as Carex spp. and Eriophorum spp. are related to the chemistry of water sampled at or near the ground water table, whereas the mosses are not. Testate amoebae were shown to be ecologically more closely related to the chemistry of water sampled at or near the water table level and to the mosses than to the deep-rooted plants.
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| 10. |
- Robroek, Björn J. M., et al.
(författare)
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Taxonomic and functional turnover are decoupled in European peat bogs
- 2017
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Ingår i: Nature Communications. - : NATURE PUBLISHING GROUP. - 2041-1723. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- In peatland ecosystems, plant communities mediate a globally significant carbon store. The effects of global environmental change on plant assemblages are expected to be a factor in determining how ecosystem functions such as carbon uptake will respond. Using vegetation data from 56 Sphagnum-dominated peat bogs across Europe, we show that in these ecosystems plant species aggregate into two major clusters that are each defined by shared response to environmental conditions. Across environmental gradients, we find significant taxonomic turnover in both clusters. However, functional identity and functional redundancy of the community as a whole remain unchanged. This strongly suggests that in peat bogs, species turnover across environmental gradients is restricted to functionally similar species. Our results demonstrate that plant taxonomic and functional turnover are decoupled, which may allow these peat bogs to maintain ecosystem functioning when subject to future environmental change.
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| 11. |
- van Dijk, Jacintha G. B., et al.
(författare)
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Herd immunity drives the epidemic fadeout of avian cholera in Arctic-nesting seabirds
- 2021
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Ingår i: Scientific Reports. - : Springer Nature. - 2045-2322. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- Avian cholera, caused by the bacterium Pasteurella multocida, is a common and important infectious disease of wild birds in North America. Between 2005 and 2012, avian cholera caused annual mortality of widely varying magnitudes in Northern common eiders (Somateria mollissima borealis) breeding at the largest colony in the Canadian Arctic, Mitivik Island, Nunavut. Although herd immunity, in which a large proportion of the population acquires immunity to the disease, has been suggested to play a role in epidemic fadeout, immunological studies exploring this hypothesis have been missing. We investigated the role of three potential drivers of fadeout of avian cholera in eiders, including immunity, prevalence of infection, and colony size. Each potential driver was examined in relation to the annual real-time reproductive number (Rt) of P. multocida, previously calculated for eiders at Mitivik Island. Each year, colony size was estimated and eiders were closely monitored, and evaluated for infection and serological status. We demonstrate that acquired immunity approximated using antibody titers to P. multocida in both sexes was likely a key driver for the epidemic fadeout. This study exemplifies the importance of herd immunity in influencing the dynamics and fadeout of epidemics in a wildlife population.
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