| 1. |
- Nicolás, César, et al.
(författare)
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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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Ingår i: Plant and Soil. - : Springer Science and Business Media LLC. - 0032-079X .- 1573-5036. ; 419:1-2, s. 113-126
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Tidskriftsartikel (refereegranskat)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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| 2. |
- Almeida, Juan Pablo, et al.
(författare)
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Ectomycorrhizal community composition and function in a spruce forest transitioning between nitrogen and phosphorus limitation
- 2019
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Ingår i: Fungal ecology. - : Elsevier. - 1754-5048 .- 1878-0083. ; 40, s. 20-31
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Tidskriftsartikel (refereegranskat)abstract
- Nitrogen is the main limiting nutrient in boreal ecosystems, but studies in southwest Sweden suggest that certain forests approach phosphorus (P) limitation driven by nitrogen (N) deposition. We added N, P or N + P to a Norway spruce forest in this region, to push the system to N or P limitation. Tree growth and needle nutrient concentrations indicated that the trees are P limited. EMF biomass was reduced only by N + P additions. Soil EMF communities responded more strongly to P than to N. Addition of apatite to ingrowth meshbags altered EMF community composition and enhanced the abundance of Imleria badia in the control and N plots, but not when P was added. The ecological significance of this species is discussed. Effects on tree growth, needle chemistry, and EMF communities indicate a dynamic interaction between EMF fungi and the nutrient status of trees and soils. (C) 2018 Elsevier Ltd and British Mycological Society. All rights reserved.
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| 3. |
- Almeida, Juan Pablo, et al.
(författare)
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Nitrophobic ectomycorrhizal fungi are associated with enhanced hydrophobicity of soil organic matter in a Norway spruce forest
- 2022
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Ingår i: Biogeosciences. - : Copernicus GmbH. - 1726-4170 .- 1726-4189. ; 19:15, s. 3713-3726
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Tidskriftsartikel (refereegranskat)abstract
- In boreal forests an important part of the photo assimilates are allocated belowground to support symbiosis of ectomycorrhizal fungi (EMF). The production of EMF extramatrical mycelium can contribute to carbon (C) sequestration in soils, but the extent of this contribution depends on the composition of the EMF community. Some species can decrease soil C stocks by degrading soil organic matter (SOM), and certain species may enhance soil C stocks by producing hydrophobic mycelia which can reduce the rate of SOM decomposition. To test how EMF communities contribute to the development of hydrophobicity in SOM, we incubated sand-filled fungal-ingrowth mesh bags amended with maize compost for one, two or three growing seasons in non-fertilized and fertilized plots in a young Norway spruce (Picea abies) forest. We measured hydrophobicity as determined by the contact angle and the C/N ratios in the mesh bags contents along with the amount of new C entering the mesh bags from outside (determined by C3 input to C4 substrate), and related that to the fungal community composition. The proportion of EMF species increased over time to become the dominant fungal guild after three growing seasons. Fertilization significantly reduced fungal growth and altered EMF communities. In the control plots the most abundant EMF species was Piloderma olivaceum, which was absent in the fertilized plots. The hydrophobicity of the mesh bag contents reached the highest values after three growing seasons only in the unfertilized controls plots and was positively related to the abundance of P. olivaceum, the C/N ratios of the mesh bag contents and the amount of new C in the mesh bags. These results suggest that some EMF species are associated with higher hydrophobicity of SOM and that EMF community shifts induced by fertilization may result in reduced hydrophobicity of soil organic matter, which in turn may reduce C sequestration rates.
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| 4. |
- Almeida, Juan Pablo, et al.
(författare)
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Phosphorus regulates ectomycorrhizal fungi biomass production in a Norway spruce forest
- 2023
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Ingår i: Biogeosciences. - : Copernicus Publications. - 1726-4170 .- 1726-4189. ; 20:7, s. 1443-1458
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Tidskriftsartikel (refereegranskat)abstract
- Ectomycorrhizal fungi (EMF) are important components of soil microbial communities, and EMF biomass can potentially increase carbon (C) stocks by accumulating in the soils as necromass and producing recalcitrant structures. EMF growth depends on the C allocated belowground by the host trees, and the nutrient limitation on tree growth is expected to influence this allocation. Therefore, studying EMF production and understanding the factors that regulates it in natural soils are important to understand C cycling in forests.Fungal mycelium collected from ingrowth mesh bags is commonly used to estimate EMF biomass, but these measurements might not reflect the total EMF production since turnover rates of the hyphae are not considered. Here we estimated EMF production and turnover in response to P fertilization (applied as superphosphate) in a Norway spruce forest where nitrogen (N) deposition has resulted in phosphorus (P) limitation of plant production by using a combination of mesh bags with different incubation periods and with Bayesian inferences. To test how localized patches of N and P influence EMF production and turnover we amended some bags with a nitrogen source (methylene urea) or P source (apatite). Additionally, the Bayesian model tested the effect of seasonality (time of mesh-bag harvesting) on EMF production and turnover.We found that turnover of EMF was not affected by P fertilization or mesh-bag amendment. P fertilization had a negative effect on EMF production in all the mesh-bag amendments, suggesting a reduced belowground C allocation to the EMF when P limitation is alleviated. Apatite amendment significantly increased EMF biomass production in comparison with the pure quartz bags in the control plots but not in the P-fertilized plots. This indicates that P-rich patches enhance EMF production in P-limited forests, but not when P is not limiting. Urea amendment had a generally positive effect on EMF production, but this was significantly reduced by P fertilization, suggesting that a decrease in EMF production due to the alleviated P limitation will affect N foraging. Seasonality had a significant effect on EMF production, and the differences registered between the treatments were higher during the warmer months and disappeared at the end of the growing season.Many studies highlight the importance of N for regulating belowground C allocation to EMF in northern coniferous forests, but here we show that the P status of the forest can be equally important for belowground carbon allocation to EMF production in areas with high N deposition.
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| 5. |
- Forsmark, Benjamin, et al.
(författare)
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Anthropogenic nitrogen enrichment increased the efficiency of belowground biomass production in a boreal forest
- 2021
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Ingår i: Soil Biology and Biochemistry. - : Elsevier BV. - 0038-0717 .- 1879-3428. ; 155
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Tidskriftsartikel (refereegranskat)abstract
- Anthropogenic nitrogen (N) enrichment in boreal forests has been shown to enhance aboveground net primary production and downregulate soil respiration, but it is not well understood if these effects are driven by reduced belowground C allocation or shifts between biomass production and respiration in fine-roots and ectomycorrhizal fungi (EMF). We utilized an experiment in a Pinus sylvestris (L.) forest simulating anthropogenic N enrichment with additions of low (3, 6, and 12 kg N ha−1 yr−1) and high (50 kg N ha−1 yr−1 × 12 yr) doses of N (n = 6) and measured the production of needles, fine-roots, and EMF mycelium during the 12th and 13th year of the experiment. We created a biomass production efficiency index by relating the biomass production rate to root-associated respiration, including both root and EMF respiration. The high N treatment enhanced the production of both needles and fine-roots, with a relatively larger increase in fine-roots, and strongly increased fine-root biomass production efficiency but had no effect on the fungal biomass in fine-roots or the production of EMF mycelium. The low N treatments had no effect on any of the measured variables. These results show that high levels of N enrichment drive shifts in the use of C allocated below ground, with less C going towards metabolic functions that result in rapid C emissions, and more C going towards the production of new tissues.
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| 6. |
- Forsmark, Benjamin, et al.
(författare)
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Shifts in microbial community composition and metabolism correspond with rapid soil carbon accumulation in response to 20 years of simulated nitrogen deposition
- 2024
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Ingår i: Science of the Total Environment. - 0048-9697. ; 918
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Tidskriftsartikel (refereegranskat)abstract
- Anthropogenic nitrogen (N) deposition and fertilization in boreal forests frequently reduces decomposition and soil respiration and enhances C storage in the topsoil. This enhancement of the C sink can be as strong as the aboveground biomass response to N additions and has implications for the global C cycle, but the mechanisms remain elusive. We hypothesized that this effect would be associated with a shift in the microbial community and its activity, and particularly by fungal taxa reported to be capable of lignin degradation and organic N acquisition. We sampled the organic layer below the intact litter of a Norway spruce (Picea abies (L.) Karst) forest in northern Sweden after 20 years of annual N additions at low (12.5 kg N ha−1 yr−1) and high (50 kg N ha−1 yr−1) rates. We measured microbial biomass using phospholipid fatty-acid analysis (PLFA) and ergosterol measurements and used ITS metagenomics to profile the fungal community of soil and fine-roots. We probed the metabolic activity of the soil community by measuring the activity of extracellular enzymes and evaluated its relationships with the most N responsive soil fungal species. Nitrogen addition decreased the abundance of fungal PLFA markers and changed the fungal community in humus and fine-roots. Specifically, the humus community changed in part due to a shift from Oidiodendron pilicola, Cenococcum geophilum, and Cortinarius caperatus to Tylospora fibrillosa and Russula griseascens. These microbial community changes were associated with decreased activity of Mn-peroxidase and peptidase, and an increase in the activity of C acquiring enzymes. Our results show that the rapid accumulation of C in the humus layer frequently observed in areas with high N deposition is consistent with a shift in microbial metabolism, where decomposition associated with organic N acquisition is downregulated when inorganic N forms are readily available.
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| 7. |
- Gundale, Michael, et al.
(författare)
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Differences in endophyte communities of introduced trees depend on the phylogenetic relatedness of the receiving forest
- 2016
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Ingår i: Journal of Ecology. - : Wiley. - 0022-0477 .- 1365-2745. ; 104:5, s. 1219-1232
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Tidskriftsartikel (refereegranskat)abstract
- Plant species sometimes perform extraordinarily well when introduced to new environments, through achieving higher growth rates, individual biomasses or higher densities in their receiving communities compared to their native range communities. One hypothesis proposed to explain enhanced performance in species’ new environments is that their soil microbial communities may be different and provide greater benefit than microbial communities encountered in species’ native environments. However, detailed descriptions of soil biota associated with species in both their native and introduced environments remain scarce. We established a global network of sites in regions where the tree species Pinus contorta has been introduced (Chile, New Zealand, Finland, Scotland and Sweden), as well as native range sites where the introduced populations originated (Canada and USA). We conducted pyrosequencing analysis to compare the root fungal endophyte communities associated with P. contorta in its native environments and in introduced environments with phylogenetically similar and dissimilar tree species (i.e. P. sylvestris in Europe and Nothofagus spp. in the Southern Hemisphere). Fungal communities associated with P. contorta consistently differed between its introduced and native environments. In Europe, P. contorta associated with the same community as P. sylvestris, where one particular species (Piloderma sphaerosporum) was particularly abundant relative to Canadian sites. In the Southern Hemisphere, P. contorta fungal communities were composed primarily of North American taxa and exhibited very little overlap with fungal communities associated with native Nothofagus spp. Synthesis. Our work shows that plants exhibit considerable plasticity in their interaction with fungi, by associating with different fungal communities across native and introduced environments. Our work also indicates that fungal communities associated with introduced plants can assemble through different mechanisms, that is by associating with existing fungal communities of phylogenetically close species, or through reassembly of co-introduced and co-invading fungi. The identification of different fungal communities in a plant species new environment provides an important step forward in understanding how soil biota may impact growth and invasion when a species is introduced to new environments.
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| 8. |
- Maaroufi, Nadia, et al.
(författare)
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Anthropogenic nitrogen enrichment enhances soil carbon accumulation by impacting saprotrophs rather than ectomycorrhizal fungal activity
- 2019
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Ingår i: Global Change Biology. - : John Wiley & Sons. - 1354-1013 .- 1365-2486. ; 25:9, s. 2900-2914
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Tidskriftsartikel (refereegranskat)abstract
- There is evidence that anthropogenic nitrogen (N) deposition enhances carbon (C) sequestration in boreal forest soils. However, it is unclear how free-living saprotrophs (bacteria and fungi, SAP) and ectomycorrhizal (EM) fungi responses to N addition impact soil C dynamics. Our aim was to investigate how SAP and EM communities are impacted by N enrichment and to estimate whether these changes influence decay of litter and humus. We conducted a long-term experiment in northern Sweden, maintained since 2004, consisting of ambient, low N additions (0, 3, 6, and 12 kg N ha(-1) year(-1)) simulating current N deposition rates in the boreal region, as well as a high N addition (50 kg N ha(-1) year(-1)). Our data showed that long-term N enrichment impeded mass loss of litter, but not of humus, and only in response to the highest N addition treatment. Furthermore, our data showed that EM fungi reduced the mass of N and P in both substrates during the incubation period compared to when only SAP organisms were present. Low N additions had no effect on microbial community structure, while the high N addition decreased fungal and bacterial biomasses and altered EM fungi and SAP community composition. Actinomycetes were the only bacterial SAP to show increased biomass in response to the highest N addition. These results provide a mechanistic understanding of how anthropogenic N enrichment can influence soil C accumulation rates and suggest that current N deposition rates in the boreal region (<= 12 kg N ha(-1) year(-1)) are likely to have a minor impact on the soil microbial community and the decomposition of humus and litter.
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| 9. |
- Manoharan, Lokeshwaran, et al.
(författare)
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Agricultural management practices influence AMF diversity and community composition with cascading effects on plant productivity
- 2017
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Ingår i: Applied Soil Ecology. - : Elsevier BV. - 0929-1393. ; 115, s. 53-59
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Tidskriftsartikel (refereegranskat)abstract
- Understanding the effects of different agricultural practices on the mycorrhizal symbiosis is important for agricultural production and the sustainable use of soil. We investigated the composition and diversity of arbuscular mycorrhizal fungi (AMF) in soils from fields under different agricultural practices (conventional and organic cereal fields, leys and permanent pastures) in southern Sweden. The diversity of AMF was found to be greatest in permanent pastures, corroborating evidence that agricultural practices such as tillage impair AMF diversity. Neither geographical location nor soil type nor any of the major soil characteristics we measured impacted AMF diversity or community composition. AMF community composition was significantly affected by the different agricultural practices, particularly conventional management, which reduced AMF diversity. Of the cereal fields sampled, those under organic management held the greatest AMF diversity, and in a glasshouse experiment this greater diversity was positively related to barley phosphorus uptake and grain biomass production. Our results demonstrate the impact of different agricultural practices on AMF communities. In particular, we demonstrate the ability of organic farming to sustain greater AMF diversity relative to conventional farming, and the potential importance of this increased diversity for sustainable cereal production.
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| 10. |
- Rog, Ido, et al.
(författare)
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Share the wealth : Trees with greater ectomycorrhizal species overlap share more carbon
- 2020
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Ingår i: Molecular Ecology. - : Wiley. - 0962-1083 .- 1365-294X. ; 29:13, s. 2321-2333
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Tidskriftsartikel (refereegranskat)abstract
- The mutualistic symbiosis between forest trees and ectomycorrhizal fungi (EMF) is among the most ubiquitous and successful interactions in terrestrial ecosystems. Specific species of EMF are known to colonize specific tree species, benefitting from their carbon source, and in turn, improving their access to soil water and nutrients. EMF also form extensive mycelial networks that can link multiple root-tips of different trees. Yet the number of tree species connected by such mycelial networks, and the traffic of material across them, are just now under study. Recently we reported substantial belowground carbon transfer between Picea, Pinus, Larix and Fagus trees in a mature forest. Here, we analyze the EMF community of these same individual trees and identify the most likely taxa responsible for the observed carbon transfer. Among the nearly 1,200 EMF root-tips examined, 50%–70% belong to operational taxonomic units (OTUs) that were associated with three or four tree host species, and 90% of all OTUs were associated with at least two tree species. Sporocarp 13C signals indicated that carbon originating from labelled Picea trees was transferred among trees through EMF networks. Interestingly, phylogenetically more closely related tree species exhibited more similar EMF communities and exchanged more carbon. Our results show that belowground carbon transfer is well orchestrated by the evolution of EMFs and tree symbiosis.
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