| 1. |
- Bahram, Mohammad, et al.
(författare)
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Structure and function of the global topsoil microbiome
- 2018
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 560:7717, s. 233-7
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Tidskriftsartikel (refereegranskat)abstract
- Soils harbour some of the most diverse microbiomes on Earth and are essential for both nutrient cycling and carbon storage. To understand soil functioning, it is necessary to model the global distribution patterns and functional gene repertoires of soil microorganisms, as well as the biotic and environmental associations between the diversity and structure of both bacterial and fungal soil communities(1-4). Here we show, by leveraging metagenomics and metabarcoding of global topsoil samples (189 sites, 7,560 subsamples), that bacterial, but not fungal, genetic diversity is highest in temperate habitats and that microbial gene composition varies more strongly with environmental variables than with geographic distance. We demonstrate that fungi and bacteria show global niche differentiation that is associated with contrasting diversity responses to precipitation and soil pH. Furthermore, we provide evidence for strong bacterial-fungal antagonism, inferred from antibiotic-resistance genes, in topsoil and ocean habitats, indicating the substantial role of biotic interactions in shaping microbial communities. Our results suggest that both competition and environmental filtering affect the abundance, composition and encoded gene functions of bacterial and fungal communities, indicating that the relative contributions of these microorganisms to global nutrient cycling varies spatially.
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| 2. |
- Hammer, Edith, et al.
(författare)
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Elemental composition of arbuscular mycorrhizal fungi at high salinity.
- 2011
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Ingår i: Mycorrhiza. - : Springer Science and Business Media LLC. - 1432-1890 .- 0940-6360. ; 21, s. 117-129
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Tidskriftsartikel (refereegranskat)abstract
- We investigated the elemental composition of spores and hyphae of arbuscular mycorrhizal fungi (AMF) collected from two saline sites at the desert border in Tunisia, and of Glomus intraradices grown in vitro with or without addition of NaCl to the medium, by proton-induced X-ray emission. We compared the elemental composition of the field AMF to those of the soil and the associated plants. The spores and hyphae from the saline soils showed strongly elevated levels of Ca, Cl, Mg, Fe, Si, and K compared to their growth environment. In contrast, the spores of both the field-derived AMF and the in vitro grown G. intraradices contained lower or not elevated Na levels compared to their growth environment. This resulted in higher K:Na and Ca:Na ratios in spores than in soil, but lower than in the associated plants for the field AMF. The K:Na and Ca:Na ratios of G. intraradices grown in monoxenic cultures were also in the same range as those of the field AMF and did not change even when those ratios in the growth medium were lowered several orders of magnitude by adding NaCl. These results indicate that AMF can selectively take up elements such as K and Ca, which act as osmotic equivalents while they avoid uptake of toxic Na. This could make them important in the alleviation of salinity stress in their plant hosts.
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| 3. |
- Hammer, Edith, et al.
(författare)
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Tit for tat? A mycorrhizal fungus accumulates phosphorus under low plant carbon availability.
- 2011
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Ingår i: FEMS Microbiology Ecology. - : Oxford University Press (OUP). - 1574-6941 .- 0168-6496. ; 76, s. 236-244
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Tidskriftsartikel (refereegranskat)abstract
- The exchange of carbohydrates and mineral nutrients in the arbuscular mycorrhizal symbiosis must be controlled by both partners in order to sustain an evolutionarily stable mutualism. Plants down-regulate their carbon flow to the fungus when nutrient levels are sufficient, while the mechanism controlling fungal nutrient transfer is unknown. Here we show that the fungus accumulates nutrients when connected to a host that is of less benefit to the fungus, indicating a potential of the fungus to control the transfer of nutrients. We used a monoxenic in vitro model of root organ cultures associated with G. intraradices, in which we manipulated the carbon availability to the plant. We found that G. intraradices accumulated up to 7 times more nutrients in its spores, and up to 9 times more in its hyphae, when the carbon pool available to the associated roots was halved. The strongest effect was found for phosphorus, considered to be the most important nutrient in the arbuscular mycorrhizal symbiosis. Other elements such as potassium and chorine were also accumulated, but to a lesser extent, while no accumulation of iron or manganese was found. Our results suggest a functional linkage between carbon and phosphorus exchange.
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| 4. |
- Olsson, Pål Axel, et al.
(författare)
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Phosphorus Availability Influences Elemental Uptake in the Mycorrhizal Fungus Glomus intraradices, as Revealed by PIXE Analysis.
- 2008
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Ingår i: Applied and Environmental Microbiology. - 0099-2240. ; 74:13, s. 4144-4148
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Tidskriftsartikel (refereegranskat)abstract
- We investigated element accumulation in the arbuscular mycorrhizal fungus Glomus intraradices. Fungal spores and mycelium growing in monoxenic cultures were analyzed. The elemental composition was quantified using particle-induced X-ray emission (PIXE) in combination with scanning transmission ion microscopy. In the spores, Ca and Fe were mainly associated with the spore wall; while P and K showed patchy distributions and their concentrations were correlated. Excess of P in the hyphal growth medium increased the P and Si concentration in spores, and increased the K:Ca ratio in spores. Increased P availability decreased the concentration of Zn and Mn in spores. We conclude that the availability of P influences the uptake and accumulation of several elements in spores. It is demonstrated that PIXE analysis is a powerful tool for quantitative analysis of elemental accumulation in fungal mycelia.
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| 5. |
- Pallon, Jan, et al.
(författare)
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Symbiotic fungi that are essential for plant nutrient uptake investigated with NMP
- 2007
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Ingår i: Nuclear Instruments & Methods in Physics Research. Section B: Beam Interactions with Materials and Atoms. - : Elsevier BV. - 0168-583X. ; 260:1, s. 149-152
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Tidskriftsartikel (refereegranskat)abstract
- The nuclear microprobe (NMP) technique using PIXE for elemental analysis and STIM on/off axis for parallel mass density normalization has proven successful to investigate possible interactions between minerals and ectomycorrhizal (EM) mycelia that form symbiotic associations with forest trees. The ability for the EM to make elements biologically available from minerals and soil were compared in field studies and in laboratory experiments, and molecular analysis (PCR-RFLP) was used to identify ectomycorrhizal species from the field samplings. EM rhizomorphs associated with apatite in laboratory systems and in mesh bags incubated in forest ecosystems contained larger amounts of Ca than similar rhizomorphs connected to acid-washed sand. EM mycelium produced in mesh bags had a capacity to mobilize P from apatite-amended sand and a high concentration of K in some rhizomorphs suggests that these fungi are good accumulators of K and may have a significant role in transporting K to trees. Spores formed by arbuscular mycorrhizal (AM) fungi in laboratory cultures were compared with spores formed in saline soils in Tunisia in Northern Africa. We found lower concentrations of P and higher concentrations of Cl in the spores collected from the field than in the spores collected from laboratory cultures. For the case of laboratory cultures, the distribution of e.g. P and K was found to be clearly correlated.
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| 6. |
- Ekroos, Johan, et al.
(författare)
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Sparing land for biodiversity at multiple spatial scales
- 2016
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Ingår i: Frontiers in Ecology and Evolution. - : Frontiers Media SA. - 2296-701X. ; 3
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Tidskriftsartikel (refereegranskat)abstract
- A common approach to the conservation of farmland biodiversity and the promotion of multifunctional landscapes, particularly in landscapes containing only small remnants of non-crop habitats, has been to maintain landscape heterogeneity and reduce land-use intensity. In contrast, it has recently been shown that devoting specific areas of non-crop habitats to conservation, segregated from high-yielding farmland (“land sparing”), can more effectively conserve biodiversity than promoting low-yielding, less intensively managed farmland occupying larger areas (“land sharing”). In the present paper we suggest that the debate over the relative merits of land sparing or land sharing is partly blurred by the differing spatial scales at which it is suggested that land sparing should be applied. We argue that there is no single correct spatial scale for segregating biodiversity protection and commodity production in multifunctional landscapes. Instead we propose an alternative conceptual construct, which we call “multiple-scale land sparing,” targeting biodiversity and ecosystem services in transformed landscapes. We discuss how multiple-scale land sparing may overcome the apparent dichotomy between land sharing and land sparing and help to find acceptable compromises that conserve biodiversity and landscape multifunctionality.
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| 7. |
- Olsrud, Maria, et al.
(författare)
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Response of ericoid mycorrhizal colonization and functioning to global change factors
- 2004
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Ingår i: New Phytologist. - : Wiley. - 1469-8137 .- 0028-646X. ; 162:2, s. 459-469
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Tidskriftsartikel (refereegranskat)abstract
- Here, we investigated effects of increased atmospheric CO2 concentration, increased temperatures, and both factors in combination on ericoid mycorrhizal colonization, mycorrhizal functioning and below-ground carbon allocation in a subarctic forest understorey, to evaluate the hypothesis that photosynthesis is a primary driver for mycorrhizal colonization. Treatment effects on ecosystem processes were investigated using C-14-pulse labelling and photosynthesis measurements in combination with analysis of ergosterol content in roots. The effects on delta(15)N in leaves were also studied. Ergosterol content in hair roots was positively correlated with ecosystem photosynthesis and was higher in heat- and CO2-treated plots. Leaves from CO2 Plots tended to be more depleted in N-15 compared with controls both for Vaccinium myrtillus and V. vitis-idaea. Our results suggest that changes in ecosystem photosynthesis, plant carbon (C) Allocation may give rise to changing mycorrhizal colonization under elevated CO2 and temperature. The role of mycorrhizas in ecosystem N-cycling may change on a long-term basis as inorganic N availability declines with increasing levels of atmospheric CO2.
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| 8. |
- Bahr, Adam, et al.
(författare)
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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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Ingår i: Flora: Morphology, Distribution, Functional Ecology of Plants. - : Elsevier BV. - 0367-2530. ; 207:5, s. 379-387
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Tidskriftsartikel (refereegranskat)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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| 9. |
- Birgander, Johanna, et al.
(författare)
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Comparison of fertility and seasonal effects on grassland microbial communities
- 2014
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Ingår i: Soil Biology & Biochemistry. - : Elsevier BV. - 0038-0717. ; 76, s. 80-89
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Tidskriftsartikel (refereegranskat)abstract
- The activity of saprotrophic fungi and bacteria, and the balance between them, can affect decomposition. Arbuscular mycorrhizal (AM) fungi are also important for the nutrient and energy transfer in soil. Microbial community composition and activity are believed to have seasonal patterns, and are known to be highly influenced by environmental factors such as pH and nutrient conditions. To evaluate the importance of season for the variation in microbial decomposer community in a context of well-known environmental factor variation, we studied microbial growth, biomass and community structure along a fertility gradient (pH 5.9-8.1; NH4-N 3-19 mu g g(-1) soil, f.w.) in a sandy grassland during one year. The microbial community structure (phospholipid fatty acid (PLFA) composition) and biomass (PLFA and neutral lipid fatty acid (NLFA) signatures) as well as fungal (acetate incorporation in ergosterol) and bacterial (leucine incorporation) growth rates were investigated at eight seasonal time points during one year. The environmental factors pH and NH4 concentrations explained a larger share of the variation in the microbial community structure. Together they explained 37% of the variation, while season (proxied by temperature) only explained 6% of the variation in PLFA composition. Bacterial and fungal biomass were both highest in early spring, while AM fungal biomass peaked in early summer. Bacterial growth rate, on the other hand, was highest during the autumn, while fungal growth rate showed no clear seasonal pattern. In conclusion, the influence of seasonal variation on microbial communities proved to be relatively small compared to that which could be assigned to pH and NH4 in the studied ranges. (C) 2014 Elsevier Ltd. All rights reserved.
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| 10. |
- Hammer, Edith, et al.
(författare)
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A mycorrhizal fungus grows on biochar and captures phosphorus from its surfaces
- 2014
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Ingår i: Soil Biology & Biochemistry. - : Elsevier BV. - 0038-0717. ; 77, s. 252-260
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Tidskriftsartikel (refereegranskat)abstract
- Biochar application to soils has potential to simultaneously improve soil fertility and store carbon to aid climate change mitigation. While many studies have shown positive effects on plant yields, much less is known about the synergies between biochar and plant growth promoting microbes, such as mycorrhizal fungi. We present the first evidence that arbuscular mycorrhizal (AM) fungi can use biochar as a physical growth matrix and nutrient source. We used monoxenic cultures of the AM fungus Rhizophagus irregularis in symbiosis with carrot roots. Using scanning electron microscopy we observed that AM fungal hyphae grow on and into two contrasting types of biochar particles, strongly attaching to inner and outer surfaces. Loading a nutrient-poor biochar surface with nutrients stimulated hyphal colonization. We labeled biochar surfaces with P-33 radiotracer and found that hyphal contact to the biochar surfaces permitted uptake of P-33 and its subsequent translocation to the associated host roots. Direct access of fungal hyphae to biochar surfaces resulted in six times more P-33 translocation to the host roots than in systems where a mesh prevented hyphal contact with the biochar. We conclude that AM fungal hyphae access microsites within biochar, that are too small for most plant roots to enter (<10 mu m), and can hence mediate plant phosphorus uptake from the biochar. Thus, combined management of biochar and AM fungi could contribute to sustainable soil and climate management by providing both a carbon-stable nutrient reservoir and a symbiont that facilitates nutrient uptake from it. (C) 2014 Elsevier Ltd. All rights reserved.
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