| 1. |
- Bahr, Adam, et al.
(author)
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Growth of ectomycorrhizal fungal mycelium along a Norway spruce forest nitrogen deposition gradient and its effect on nitrogen leakage
- 2013
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In: Soil Biology and Biochemistry. - : Elsevier BV. - 0038-0717 .- 1879-3428. ; 59, s. 38-48
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Journal article (peer-reviewed)abstract
- Almost all boreal and temperate forest tree species live in symbiosis with ectomycorrhizal fungi (EMF); the trees transfer carbon (C) to the fungi in exchange for nutrients and water. Several studies have shown that experimental application of inorganic nitrogen (N) represses production of EMF extramatrical mycelia (EMM), but studies along N deposition gradients are underrepresented. Other environmental variables than N may influence EMM production and in this study we included 29 thoroughly monitored Norway spruce stands from a large geographical region in Sweden in order to evaluate the importance of N deposition on EMM growth and N leaching in a broader context. It was concluded that N deposition was the most important factor controlling EMM production and that the amounts typically deposited in boreal and boreo-nemoral regions can be sufficient to reduce EMM growth. Other factors, such as phosphorus status and pH, were also correlated with EMM production and should be considered when predicting EMM growth and N leaching. We also showed that EMM production substantially contributed to the C sequestration (320 kg ha(-1) yr(-1)), suggesting that it should be included in C cycle modelling. Furthermore, EMF are probably important for the N retention capacity since high N leaching coincided with low EMM growth. However, it was not possible to differentiate between the effects of EMF and the direct effect of N deposition on N leaching in the present study.
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| 2. |
- Bahr, Adam, et al.
(author)
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Long-term changes in vegetation and soil chemistry in a calcareous and sandy semi-natural grassland
- 2012
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In: Flora: Morphology, Distribution, Functional Ecology of Plants. - : Elsevier BV. - 0367-2530. ; 207:5, s. 379-387
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Journal article (peer-reviewed)abstract
- Calcicole plant species are vulnerable to acidification and fertilization, caused by deposition and changes in land use, since they are adapted to nutrient-poor calcareous conditions. In this study we used vegetation data (vascular plants, bryophytes and lichens) from 1964 and 1985 and stored soil samples from 1966 to investigate long-term soil chemistry and vegetation changes in a semi-natural, sandy calcareous grassland in southern Sweden. In the re-investigation in 2008 we found that increased decalcification due to acidification could not be verified. The plant community had changed from stress-tolerant calcareous grassland towards a community promoted by higher nutrient availability. Furthermore, the cover of species indicating calcareous conditions had decreased. A decline in the cover of species adapted to alkaline, phosphorus-poor conditions may be due to increased nutrient availability, but there were also indications that the vegetation had changed due to overgrowth by woody plants. This long-term impoverishment of the plant community highlights the need for appropriate management of calcareous grasslands, in order to limit the nutrients available in the soil and prevent overgrowth by shrubs and trees. (C) 2012 Published by Elsevier GmbH.
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| 3. |
- Bahr, Adam, et al.
(author)
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Nitrogen leaching and ectomycorrhizal nitrogen retention capacity in a Norway spruce forest fertilized with nitrogen and phosphorus
- 2015
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In: Plant and Soil. - : Springer Science and Business Media LLC. - 0032-079X .- 1573-5036. ; 390:1-2, s. 323-335
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Journal article (peer-reviewed)abstract
- To estimate the production of external ectomycorrhizal mycelia (EMM) in Norway spruce forests with varying nitrogen (N) and phosphorus (P) levels, and to relate this to the N retention capacity of ectomycorrhizal fungi (EMF) and N leaching. Seasonal changes in EMF production (in ingrowth mesh bags) and soil water N (in suction lysimeters) were analyzed after fertilization with N or N combined with P. The EMF N retention capacity was estimated by the addition of isotopically labeled N to the mesh bags. No relationship was found between the seasonal variation in EMF growth and N leakage from the soil. However, in the mesh bags, the total assimilation of N-15 by EMF was almost halved by N fertilization, while twice as much N-15 leached through. We found a high specific N assimilation capacity per unit weight of EMF mycelia. This was unaffected by N fertilization, but the total assimilation of N by EMF was drastically reduced due to reduced production of EMM. However, N-retaining processes other than N assimilation by EMF must be taken into account to explain the losses of N after fertilization.
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| 4. |
- Brulin, Göran, et al.
(author)
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Policy Programmes to promote Entrepreneurship and Innovation : A study of the art, design and impact issues
- 2011
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In: Proceedings of 56:th ISCB world conference. - 9780981902838 ; , s. 1-11
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Conference paper (other academic/artistic)abstract
- Europe 2020 strategy EU puts forward three mutually reinforcing priorities smart, sustainable and inclusive growth. A main driving force are innovation programmes. Our understanding of programme-drivingwill always be tentative but can be improved. Analysis of programmedriving provides an alternative way of tackling the problem. It is an approach that enhances the understanding – contextually, practically and theoretically. Rather than heading for final, concrete and onedimensionaloften quantitative knowledge we should get used to the fact that our understanding always will be fragmentary and imperfect though, on a higher level! Knowledge on innovation programme-driving should improve innovation institutions/practices/ethos in different respects.
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| 5. |
- Elg, Mattias, et al.
(author)
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Sustainable development in organizations
- 2015. - 1
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In: Sustainable development in organizations. - Cheltenham : Edward Elgar Publishing. - 9781784716882 - 9781784716899 ; , s. 1-15
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Book chapter (other academic/artistic)
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| 6. |
- Ellström, Magnus
(author)
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Effects of nitrogen deposition on the growth, metabolism and activity of ectomycorrhizal fungi
- 2014
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Doctoral thesis (other academic/artistic)abstract
- Elevated nitrogen (N) deposition is an environmental problem that can affect plants and microorganisms, which are vital for the terrestrial N and carbon (C) cycles. This thesis has investigated the response of ectomycorrhizal fungi (EMF) to increased N deposition. Ectomycorrhizal fungi form mutualistic interactions with the roots of woody plants, including almost all boreal and temperate forests tree species. Trees transfer photosyntetically-derived carbohydrates to EMF, which in exchange provide trees with water and nutrients, particularly N. In soil, a major part of N is present in organic forms, embedded in recalcitrant organic matter (OM), and it is believed that trees are dependent on degrading activities of EMF to gain access to this pool of N. This thesis provides evidences that EMF disrupt OM complexes when assimilating N using an oxidation mechanism. In order to release organic N, EMF can deploy a mechanism including Fenton chemistry involved in the production of hydroxyl radicals. It was also demonstrated that EMF can be equally efficient in degrading OM as saprotrophic brown-rot fungi. Little is known about how the ability of EMF to modify OM is affected by increased N deposition. Many studies have shown that degradation of OM decreases with increasing N deposition. However, in this thesis it was demonstrated that N addition did not decrease the oxidation of OM by EMF when grown in axenic cultures with sufficient amounts of readily available C. Furthermore, work in this thesis showed that elevated N deposition decrease the biomass of EMF, which has been interpreted as a result of reduced C allocation from the tree host. It was further demonstrated that during C-starvation, EMF can metabolize C and other nutrients from dying parts of its mycelia. This can influence the nutrient status of dead mycelia and affect the recalcitrance of EMF necromass, which is important to consider when studying C and N dynamics in forest soils, especially under increased N deposition when EMF are exposed to decreasing C supply from tree hosts. Taken together, it is suggested that the most important factor regulating growth, activity and metabolism in EMF, is the C allocation from the tree host. However, most experiments were conducted in non-symbiotic systems and symbiotic experiments are needed to understand how plant C allocation affects EMF processes in natural systems. One gram of boreal forest soil typically contains hundreds of meters of ectomycorrhizal hyphae, thus, a shift in their capacity to assimilate organically bound N through the modification of OM can have major impacts on the cycling of carbon and other nutrients in forest ecosystems.
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| 7. |
- Ellström, Magnus, et al.
(author)
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The carbon starvation response of the ectomycorrhizal fungus Paxillus involutus.
- 2015
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In: FEMS Microbiology Ecology. - : Oxford University Press (OUP). - 1574-6941. ; 91:4
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Journal article (peer-reviewed)abstract
- The amounts of carbon allocated to the fungal partner in ectomycorrhizal associations can vary substantially depending on the plant growth and the soil nutrient conditions, and the fungus may frequently be confronted with limitations in carbon. We used chemical analysis and transcriptome profiling to examine the physiological response of the ectomycorrhizal fungus Paxillus involutus to carbon starvation during axenic cultivation. Carbon starvation induced a decrease in the biomass. Concomitantly, ammonium, cell-wall material (chitin) and proteolytic enzymes were released into the medium, which suggest autolysis. Compared with the transcriptome of actively growing hyphae, about 45% of the transcripts analyzed were differentially regulated during C-starvation. Induced during starvation were transcripts encoding extracellular enzymes such as peptidases, chitinases, and laccases. In parallel, transcripts of N-transporters were upregulated, which suggest that some of the released nitrogen compounds were re-assimilated by the mycelium. The observed changes suggest that the carbon-starvation response in P. involutus is associated with complex cellular changes that involves autolysis, recycling of intracellular compounds by autophagy and reabsorption of the extracellular released material. The study provides molecular markers that can be used to examine the role of autolysis for the turnover and survival of the ectomycorrhizal mycelium in soils.
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| 8. |
- Monadjem, Ara, et al.
(author)
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The activity of an insectivorous bat Neoromicia nana on tracks in logged and unlogged forest in tropical Africa
- 2010
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In: African Journal of Ecology. - : Wiley. - 1365-2028 .- 0141-6707. ; 48:4, s. 1083-1091
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Journal article (peer-reviewed)abstract
- Logging activities and the associated creation of roads and tracks can disturb and fragment forests, which may lead to a loss of forest-dependent species and possibly favour nonforest generalists and edge species. The effects of such disturbance are poorly known for African insectivorous bats. We studied the activity patterns of insectivorous bats in a tropical African forest at Kibale National Park, Uganda, using an Anabat bat detector. The echolocation calls of the vespertilionid bat Neoromicia nana were the most frequently detected. This species was most active in the first 5 h after sunset with activity declining rapidly after midnight until sampling finished at 01:00 h. There was no difference in activity of N. nana levels between logged or undisturbed forest; however, this species exhibited higher levels of activity along the wide tracks running through the two forests than either 30 m off these tracks or along the narrow forest trails. The wing morphology and echolocation call of N. nana may be constraining it to flying in uncluttered space on the edge of the forest, penetrating mostly along wider tracks and roads. Further research (in particular radio-telemetry) is required to test and validate these data.Resume
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| 9. |
- Nicolás, César, et al.
(author)
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Chemical changes in organic matter after fungal colonization in a nitrogen fertilized and unfertilized Norway spruce forest
- 2017
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In: Plant and Soil. - : Springer Science and Business Media LLC. - 0032-079X .- 1573-5036. ; 419:1-2, s. 113-126
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Journal article (peer-reviewed)abstract
- Background and aims: Decomposition and transformation of organic matter (OM) in forest soils are conducted by the concomitant action of saprotrophic and mycorrhizal fungi. Here, we examine chemical changes in OM after fungal colonization in nitrogen fertilized and unfertilized soils from a Norway spruce forest. Methods: Sand-filled bags amended with composted maize leaves were placed in the forest soil and harvested after 17 months. Infrared and near edge X-ray absorption fine structure spectroscopies were used to study the chemical changes in the OM. Fungal community composition of the bags was also evaluated. Results: The proportion of ectomycorrhizal fungi declined in the fertilized plots, but the overall fungal community composition was similar between N treatments. Decomposition of the OM was, independently of the N level or soil horizon, accompanied by an increase of C/N ratio of the mesh-bag content. Moreover, the proportions of carboxylic compounds in the incubated OM increased in the mineral horizon, while heterocyclic-N compounds decreased, especially in unfertilized plots with higher N demand from the trees. Conclusions: Our results indicate that more oxidized organic C and less heterocyclic-N proportions in the OM remain after fungal colonization in the mineral layers, and suggest that ectomycorrhizal fungi transfer less heterocyclic-N from the mesh bags to the host trees under high N levels.
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| 10. |
- Persson, Sofia, et al.
(author)
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Comparison between RT droplet digital PCR and RT real-time PCR for quantification of noroviruses in oysters.
- 2018
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In: International Journal of Food Microbiology. - : Elsevier BV. - 0168-1605 .- 1879-3460. ; 284, s. 73-83
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Journal article (peer-reviewed)abstract
- Oysters are frequently associated with norovirus outbreaks, but the presence of norovirus RNA in oysters does not necessarily imply a health risk to humans. There is a close link between human illness and consumption of oysters with high levels of norovirus RNA, but oysters with low levels of norovirus RNA are more unlikely to be associated with illness. Reliable and precise quantification methods are therefore important for outbreak investigations and risk assessments. This study optimised and validated RT droplet digital PCR (RT-ddPCR) assays for quantification of norovirus genogroups I and II in artificially contaminated oysters, and compared them with the standard method, RT real-time PCR (RT-qPCR). The two methods had comparable 95% limits of detection, but RT-ddPCR generally showed greater precision in quantification. Differences between fluorometric measurements and quantification with RT-ddPCR were determined on in vitro transcribed RNA with targets for norovirus genogroups I and II. Quantification by RT-ddPCR was on average 100 times lower than the fluorometric value for norovirus GI and 15.8 times lower than the fluorometric value for norovirus GII. The large inter-assay difference observed highlights the need for monitoring the RT efficiency in RT-ddPCR, especially when results from different assays are compared. Overall, this study suggests that RT-ddPCR can be a suitable method for precise quantification of norovirus genogroups I and II in oysters.
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