| 1. |
- Boberg, Johanna, et al.
(författare)
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Fungal C translocation restricts N-mineralization in heterogeneous environments
- 2010
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Ingår i: Functional Ecology. - : Wiley. - 0269-8463 .- 1365-2435. ; 24, s. 454-459
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Tidskriftsartikel (refereegranskat)abstract
- P>1. In forest soils, fungi generally dominate the decomposer community, but their specific, filamentous physiology is often not recognized in nitrogen (N) cycling models. Many litter degrading fungi form large mycelia and have a well-developed capacity to translocate resources within their mycelia. Fungi may thus connect substrates that differ with respect to carbon (C) and nitrogen (N) availability and, thereby, overcome local resource limitation through translocation.2. Here we test whether the ability of fungi to translocate carbohydrates within their mycelia prevents local C limitation in a low C:N ratio substrate, thereby reducing N mineralization. The capacity of fungi to translocate N to a high C:N ratio substrate in order to increase the decomposition, was also assessed. Two litter decomposing fungi, Marasmius androsaceus and Mycena epipterygia were grown in axenic laboratory microcosms containing spatially separated substrates: pine needles (C:N = 135) and glycine (C:N = 2).3. In the absence of needles both fungi mineralized the glycine N. When connecting the two substrates, both fungi were able to overcome local C-deficiency on the glycine medium by translocating carbohydrates from the needles. In the presence of needles, N mineralization from glycine was negligible, although the glycine was utilized. Only trace amounts of N were translocated from glycine to the needles.4. A basic assumption of N cycling models is that substrates of different qualities decompose in an independent manner. Our observations imply that this assumption may be violated in heterogenic environments dominated by fungi.
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| 2. |
- Boberg, Johanna, et al.
(författare)
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Nitrogen and Carbon Reallocation in Fungal Mycelia during Decomposition of Boreal Forest Litter
- 2014
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Ingår i: PLOS ONE. - : Public Library of Science. - 1932-6203. ; 9:3, s. e92897-
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Tidskriftsartikel (refereegranskat)abstract
- Boreal forests are characterized by spatially heterogeneous soils with low N availability. The decomposition of coniferous litter in these systems is primarily performed by basidiomycete fungi, which often form large mycelia with a well-developed capacity to reallocate resources spatially-an advantageous trait in heterogeneous environments. In axenic microcosm systems we tested whether fungi increase their biomass production by reallocating N between Pinus sylvestris (Scots pine) needles at different stages of decomposition. We estimated fungal biomass production by analysing the accumulation of the fungal cell wall compound chitin. Monospecific systems were compared with systems with interspecific interactions. We found that the fungi reallocated assimilated N and mycelial growth away from well-degraded litter towards fresh litter components. This redistribution was accompanied by reduced decomposition of older litter. Interconnection of substrates increased over-all fungal C use efficiency (i.e. the allocation of assimilated C to biomass rather than respiration), presumably by enabling fungal translocation of growth-limiting N to litter with higher C quality. Fungal connection between different substrates also restricted N-mineralization and production of dissolved organic N, suggesting that litter saprotrophs in boreal forest ecosystems primarily act to redistribute rather than release N. This spatial integration of different resource qualities was hindered by interspecific interactions, in which litters of contrasting quality were colonised by two different basidiomycete species. The experiments provide a detailed picture of how resource reallocation in two decomposer fungi leads to a more efficient utilisation of spatially separated resources under N-limitation. From an ecosystem point of view, such economic fungal behaviour could potentially contribute to organic matter accumulation in the litter layers of boreal forests.
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| 3. |
- Boberg, Johanna, et al.
(författare)
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Nitrogen availability affects saprotrophic basidiomycetes decomposing pine needles in a long term laboratory study
- 2011
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Ingår i: Fungal Ecology. - : Elsevier BV. - 1754-5048 .- 1878-0083. ; 4, s. 408-416
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Tidskriftsartikel (refereegranskat)abstract
- Fungi, especially basidiomycetous litter decomposers, are pivotal to the turnover of soil organic matter in forest soils. Many litter decomposing fungi have a well-developed capacity to translocate resources in their mycelia, a feature that may significantly affect carbon (C) and nitrogen (N) dynamics in decomposing litter. In an eight-month long laboratory study we investigated how the external availability of N affected the decomposition of Scots pine needles, fungal biomass production, N retention and N-mineralization by two litter decomposing fungi - Marasmius androsaceus and Mycena epipterygia. Glycine additions had a general, positive effect on fungal biomass production and increased accumulated needle mass loss after 8 months, suggesting that low N availability may limit fungal growth and activity in decomposing pine litter. Changes in the needle N pool reflected the dynamics of the fungal mycelium. During late decomposition stages, redistribution of mycelium and N out from the decomposed needles was observed for M. epipterygia, suggesting autophagous self degradation. (C) 2011 Elsevier Ltd and The British Mycological Society. All rights reserved.
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