| 1. |
- Baskaran, Preetisri, et al.
(author)
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Modelling the influence of ectomycorrhizal decomposition on plant nutrition and soil carbon sequestration in boreal forest ecosystems
- 2017
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In: New Phytologist. - : Wiley. - 0028-646X .- 1469-8137. ; 213:3, s. 1452-1465
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Journal article (peer-reviewed)abstract
- Tree growth in boreal forests is limited by nitrogen (N) availability. Most boreal forest trees form symbiotic associations with ectomycorrhizal (ECM) fungi, which improve the uptake of inorganic N and also have the capacity to decompose soil organic matter (SOM) and to mobilize organic N (ECM decomposition'). To study the effects of ECM decomposition' on ecosystem carbon (C) and N balances, we performed a sensitivity analysis on a model of C and N flows between plants, SOM, saprotrophs, ECM fungi, and inorganic N stores. The analysis indicates that C and N balances were sensitive to model parameters regulating ECM biomass and decomposition. Under low N availability, the optimal C allocation to ECM fungi, above which the symbiosis switches from mutualism to parasitism, increases with increasing relative involvement of ECM fungi in SOM decomposition. Under low N conditions, increased ECM organic N mining promotes tree growth but decreases soil C storage, leading to a negative correlation between C stores above- and below-ground. The interplay between plant production and soil C storage is sensitive to the partitioning of decomposition between ECM fungi and saprotrophs. Better understanding of interactions between functional guilds of soil fungi may significantly improve predictions of ecosystem responses to environmental change.
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| 2. |
- Bödeker, Inga, et al.
(author)
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Ectomycorrhizal Cortinarius species participate in enzymatic oxidation of humus in northern forest ecosystems
- 2014
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In: New Phytologist. - : Wiley. - 0028-646X .- 1469-8137. ; 203, s. 245-256
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Journal article (peer-reviewed)abstract
- In northern forests, belowground sequestration of nitrogen (N) in complex organic pools restricts nutrient availability to plants. Oxidative extracellular enzymes produced by ectomycorrhizal fungi may aid plant N acquisition by providing access to N in macromolecular complexes. We test the hypotheses that ectomycorrhizal Cortinarius species produce Mn-dependent peroxidases, and that the activity of these enzymes declines at elevated concentrations of inorganic N.In a boreal pine forest and a sub-arctic birch forest, Cortinarius DNA was assessed by 454-sequencing of ITS amplicons and related to Mn-peroxidase activity in humus samples with- and without previous N amendment. Transcription of Cortinarius Mn-peroxidase genes was investigated in field samples. Phylogenetic analyses of Cortinarius peroxidase amplicons and genome sequences were performed.We found a significant co-localization of high peroxidase activity and DNA from Cortinarius species. Peroxidase activity was reduced by high ammonium concentrations. Amplification of mRNA sequences indicated transcription of Cortinarius Mn-peroxidase genes under field conditions. The Cortinarius glaucopus genome encodes 11 peroxidases - a number comparable to many white-rot wood decomposers.These results support the hypothesis that some ectomycorrhizal fungi - Cortinarius species in particular - may play an important role in decomposition of complex organic matter, linked to their mobilization of organically bound N.
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| 3. |
- Bödeker, Inga, et al.
(author)
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Mycorrhizal and saprotrophic fungal guilds compete for the same organic substrates but affect decomposition differently
- 2016
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In: Functional Ecology. - : Wiley. - 0269-8463 .- 1365-2435. ; 30, s. 1967-1978
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Journal article (peer-reviewed)abstract
- 1. Communities of litter saprotrophic and root-associated fungi are vertically separated within boreal forest soil profiles. It is unclear whether this depth partitioning is maintained exclusively by substrate-mediated niche partitioning (i.e. distinct fundamental niches), or by competition for space and resources (i.e. distinct realized niches). Improved understanding of the mechanisms driving spatial partitioning of these fungal guilds is critical, as they modulate carbon and nutrient cycling in different ways.2. Under field settings, we tested the effects of substrate quality and the local fungal species pool at various depths in determining the potential of saprotrophic and mycorrhizal fungi to colonize and exploit organic matter. Natural substrates of three qualities-fresh or partly decomposed litter or humus -were incubated in the corresponding organic layers of a boreal forest soil profile in a fully factorial design. After one and two growing seasons, fungal community composition in the substrates was determined by 454-pyrosequencing and decomposition was analyzed.3. Fungal community development during the course of the experiment was determined to similar degrees by vertical location of the substrates (24% of explained variation) and by substrate quality (20%), indicating that interference competition is a strong additional driver of the substrate-dependent depth partitioning of fungal guilds in the system. During the first growing season, litter substrates decomposed slower when colonized by root-associated communities than when colonized by communities of litter saprotrophs, whereas humus was only slightly decomposed by both fungal guilds. During the second season, certain basidiomycetes from both guilds were particularly efficient in localizing and exploiting their native organic substrates although displaced in the vertical profile. This validates that fungal community composition, rather than microclimatic factors, were responsible for observed depth-related differences in decomposer activities during the first season.4. In conclusion, our results suggest that saprotrophic and root-associated fungal guilds have overlapping fundamental niches with respect to colonization of substrates of different qualities, and that their substrate-dependent depth partitioning in soils of ectomycorrhiza-dominated ecosystems is reinforced by interference competition. Through competitive interactions, mycorrhizal fungi can thus indirectly regulate litter decomposition rates by restraining activities of more efficient litter saprotrophs.
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| 4. |
- Castaño, Carles, et al.
(author)
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Contrasting plant–soil–microbial feedbacks stabilize vegetation types and uncouple topsoil C and N stocks across a subarctic–alpine landscape
- 2023
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In: New Phytologist. - : John Wiley & Sons. - 0028-646X .- 1469-8137. ; 238:6, s. 2621-2633
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Journal article (peer-reviewed)abstract
- Global vegetation regimes vary in belowground carbon (C) and nitrogen (N) dynamics. However, disentangling large-scale climatic controls from the effects of intrinsic plant–soil–microbial feedbacks on belowground processes is challenging. In local gradients with similar pedo-climatic conditions, effects of plant–microbial feedbacks may be isolated from large-scale drivers. Across a subarctic–alpine mosaic of historic grazing fields and surrounding heath and birch forest, we evaluated whether vegetation-specific plant–microbial feedbacks involved contrasting N cycling characteristics and C and N stocks in the organic topsoil. We sequenced soil fungi, quantified functional genes within the inorganic N cycle, and measured 15N natural abundance. In grassland soils, large N stocks and low C : N ratios associated with fungal saprotrophs, archaeal ammonia oxidizers, and bacteria capable of respiratory ammonification, indicating maintained inorganic N cycling a century after abandoned reindeer grazing. Toward forest and heath, increasing abundance of mycorrhizal fungi co-occurred with transition to organic N cycling. However, ectomycorrhizal fungal decomposers correlated with small soil N and C stocks in forest, while root-associated ascomycetes associated with small N but large C stocks in heath, uncoupling C and N storage across vegetation types. We propose that contrasting, positive plant–microbial feedbacks stabilize vegetation trajectories, resulting in diverging soil C : N ratios at the landscape scale.
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| 5. |
- Castaño Soler, Carles, et al.
(author)
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Optimized metabarcoding with Pacific biosciences enables semi-quantitative analysis of fungal communities
- 2020
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In: New Phytologist. - : Wiley. - 0028-646X .- 1469-8137. ; 228, s. 1149-1158
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Journal article (peer-reviewed)abstract
- Recent studies have questioned the use of high-throughput sequencing of the nuclear ribosomal internal transcribed spacer (ITS) region to derive a semi-quantitative representation of fungal community composition. However, comprehensive studies that quantify biases occurring during PCR and sequencing of ITS amplicons are still lacking. We used artificially assembled communities consisting of 10 ITS-like fragments of varying lengths and guanine-cytosine (GC) contents to evaluate and quantify biases during PCR and sequencing with Illumina MiSeq, PacBio RS II and PacBio Sequel I technologies. Fragment length variation was the main source of bias in observed community composition relative to the template, with longer fragments generally being under-represented for all sequencing platforms. This bias was three times higher for Illumina MiSeq than for PacBio RS II and Sequel I. All 10 fragments in the artificial community were recovered when sequenced with PacBio technologies, whereas the three longest fragments (> 447 bases) were lost when sequenced with Illumina MiSeq. Fragment length bias also increased linearly with increasing number of PCR cycles but could be mitigated by optimization of the PCR setup. No significant biases related to GC content were observed. Despite lower sequencing output, PacBio sequencing was better able to reflect the community composition of the template than Illumina MiSeq sequencing.
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| 6. |
- Engelbrecht Clemmensen, Karina, et al.
(author)
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A tipping point in carbon storage when forest expands into tundra is related to mycorrhizal recycling of nitrogen
- 2021
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In: Ecology Letters. - : Wiley. - 1461-023X .- 1461-0248. ; 24, s. 1193-1204
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Journal article (peer-reviewed)abstract
- Tundra ecosystems are global belowground sinks for atmospheric CO2. Ongoing warming-induced encroachment by shrubs and trees risks turning this sink into a CO2 source, resulting in a positive feedback on climate warming. To advance mechanistic understanding of how shifts in mycorrhizal types affect long-term carbon (C) and nitrogen (N) stocks, we studied small-scale soil depth profiles of fungal communities and C-N dynamics across a subarctic-alpine forest-heath vegetation gradient. Belowground organic stocks decreased abruptly at the transition from heath to forest, linked to the presence of certain tree-associated ectomycorrhizal fungi that contribute to decomposition when mining N from organic matter. In contrast, ericoid mycorrhizal plants and fungi were associated with organic matter accumulation and slow decomposition. If climatic controls on arctic-alpine forest lines are relaxed, increased decomposition will likely outbalance increased plant productivity, decreasing the overall C sink capacity of displaced tundra.
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| 7. |
- Engelbrecht Clemmensen, Karina, et al.
(author)
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Carbon sequestration is related to mycorrhizal fungal community shifts during long-term succession in boreal forests
- 2015
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In: New Phytologist. - : Wiley. - 0028-646X .- 1469-8137. ; 205, s. 1525-1536
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Journal article (peer-reviewed)abstract
- Boreal forest soils store a major proportion of the global terrestrial carbon (C) and below-ground inputs contribute as much as above-ground plant litter to the total C stored in the soil. A better understanding of the dynamics and drivers of root-associated fungal communities is essential to predict long-term soil C storage and climate feedbacks in northern ecosystems. We used 454-pyrosequencing to identify fungal communities across fine-scaled soil profiles in a 5000yr fire-driven boreal forest chronosequence, with the aim of pinpointing shifts in fungal community composition that may underlie variation in below-ground C sequestration. In early successional-stage forests, higher abundance of cord-forming ectomycorrhizal fungi (such as Cortinarius and Suillus species) was linked to rapid turnover of mycelial biomass and necromass, efficient nitrogen (N) mobilization and low C sequestration. In late successional-stage forests, cord formers declined, while ericoid mycorrhizal ascomycetes continued to dominate, potentially facilitating long-term humus build-up through production of melanized hyphae that resist decomposition. Our results suggest that cord-forming ectomycorrhizal fungi and ericoid mycorrhizal fungi play opposing roles in below-ground C storage. We postulate that, by affecting turnover and decomposition of fungal tissues, mycorrhizal fungal identity and growth form are critical determinants of C and N sequestration in boreal forests.See also the Commentary by Christopher W. Fernandez and Peter G. Kennedy
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| 8. |
- Engelbrecht Clemmensen, Karina, et al.
(author)
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Carbon sequestration potential and the multiple functions of Nordic grasslands
- 2023
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In: Climatic Change. - 0165-0009 .- 1573-1480. ; 176
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Journal article (peer-reviewed)abstract
- Grasslands are important carbon sinks, but the underlying processes for their soil carbon sequestration potential are still not well understood, despite much attention given to this topic. In Europe, grasslands, especially semi-natural grasslands, are also important for promoting biodiversity. Moreover, recent global reports have highlighted the importance of biodiversity in supporting climate actions. In boreal and alpine regions in the Nordic countries, grasslands also play an important role in milk and meat production and food security. Certain grassland features and management practices may enhance their soil carbon sequestration potential. Semi-natural grasslands maintained by optimized livestock grazing are vital for aboveground biodiversity and show promise for belowground biodiversity and carbon sequestration potential. It is essential to assess the multiple functions of grasslands, particularly semi-natural grasslands, to facilitate the optimization of policy measures across policy areas. Climate and biodiversity policies should not counteract each other, as some do today. This essay addresses the multiple functions of grasslands and calls for more knowledge about carbon sequestration in Nordic grasslands. This will enable the management of these ecosystems to align with climate mitigation, maintain biodiversity, and satisfy the global need for increased food supply.
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| 9. |
- Engelbrecht Clemmensen, Karina
(author)
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Conference for mycologists
- 2017
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In: Scandinavian Journal of Forest Research. - 0282-7581 .- 1651-1891. ; 32, s. 197-197
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Journal article (other academic/artistic)
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| 10. |
- Engelbrecht Clemmensen, Karina
(author)
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Ectomycorrhizal Fungal Responses to Forest Liming and Wood Ash Addition: Review and Meta-analysis
- 2017
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In: Sustainability in Plant and Crop Protection. - Cham : Springer International Publishing. ; , s. 223-252
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Conference paper (peer-reviewed)abstract
- Large-scale liming and wood ash addition are common practices to mitigate soil and water acidification in temperate and boreal forests. In addition, wood ash recycles nutrients removed at harvest to the forest ecosystem. Both liming and wood ash applications typically increase soil pH by 1-2 units. Therefore, they affect a range of soil processes and organisms including ectomycorrhizal (EM) fungi which are vital for the nutrition of many tree species. Here we review field studies reporting the effects of lime and wood ash amendments on EM fungi. We systematically compiled studies where known amounts of ash or lime were distributed to plots paired with comparable control plots, and where mycorrhizal variables were recorded. For a subset of studies meeting explicit criteria, we performed meta-analyses using overall mycorrhizal abundance, species richness or the abundance of specific fungal taxa as response variables. Guided by availability of data, the focus is on Nordic coniferous forests. Although the reviewed field studies varied widely in dosage and experimental setup they clearly demonstrated that liming and wood ash amendments influence EM fungal species composition. Across studies, species belonging to the lineages Cortinarius and Russula-lactarius (Basidiomycota), particularly Russula ochroleuca, decreased in relative abundance, while species within the Tuber-helvella (Ascomycota) increased. Particular species within the Amphinema-tylospora lineage responded in opposite directions; Tylospora fibrillosa decreased in relation to the control, while Amphinema byssoides increased. The significant changes in species or clade abundances were in the range of 5-20% compared to non-treated plots. In contrast, neither the belowground mycorrhizal biomass nor species richness responded to liming or wood ash applications. We conclude that liming and wood ash amendments cause consistent EM fungal species dominance shifts, but that a high EM fungal biomass and species and phylogenetic richness is maintained on the tree roots. Given the large dispersal potential of many EM fungi, we therefore suggest that these treatments at normal recommended dosages do not pose any immediate threats to EM fungal biodiversity, at least not when applied at relatively small spatial scales. Whether the observed dominance shifts among EM fungal clades have consequences for the functioning of the EM fungal guild, e.g. in relation to nutrient cycling or tree nutrition, is an important question that should be further investigated.
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