| 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. |
- 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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| 3. |
- Sheldrake, Merlin, et al.
(författare)
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A phosphorus threshold for mycoheterotrophic plants in tropical forests
- 2017
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Ingår i: Proceedings of the Royal Society B: Biological Sciences. - : The Royal Society. - 0962-8452 .- 1471-2954. ; 284:1848
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Tidskriftsartikel (refereegranskat)abstract
- The majority of terrestrial plants associate with arbuscular mycorrhizal (AM) fungi, which typically facilitate the uptake of limiting mineral nutrients by plants in exchange for plant carbon. However, hundreds of non-photosynthetic plant species—mycoheterotrophs—depend entirely on AM fungi for carbon as well as mineral nutrition. Mycoheterotrophs can provide insight into the operation and regulation of AM fungal relationships, but little is known about the factors, fungal or otherwise, that affect mycoheterotroph abundance and distribution. In a lowland tropical forest in Panama, we conducted the first systematic investigation into the influence of abiotic factors on the abundance and distribution of mycoheterotrophs, to ask whether the availability of nitrogen and phosphorus altered the occurrence of mycoheterotrophs and their AM fungal partners. Across a natural fertility gradient spanning the isthmus of Panama, and also in a long-term nutrientaddition experiment, mycoheterotrophs were entirely absent when soil exchangeable phosphate concentrations exceeded 2 mg P kg21. Experimental phosphorus addition reduced the abundance of AM fungi, and also reduced the abundance of the specific AM fungal taxa required by the mycoheterotrophs, suggesting that the phosphorus sensitivity of mycoheterotrophs is underpinned by the phosphorus sensitivity of their AM fungal hosts. The soil phosphorus concentration of 2 mg P kg21 also corresponds to a marked shift in tree community composition and soil phosphatase activity across the fertility gradient, suggesting that our findings have broad ecological significance.
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| 4. |
- Sheldrake, Merlin, et al.
(författare)
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Arbuscular mycorrhizal fungal community composition is altered by long-term litter removal but not litter addition in a lowland tropical forest
- 2017
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Ingår i: New Phytologist. - : Wiley. - 0028-646X .- 1469-8137. ; 214:1, s. 455-467
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Tidskriftsartikel (refereegranskat)abstract
- Tropical forest productivity is sustained by the cycling of nutrients through decomposing organic matter. Arbuscular mycorrhizal (AM) fungi play a key role in the nutrition of tropical trees, yet there has been little experimental investigation into the role of AM fungi in nutrient cycling via decomposing organic material in tropical forests. We evaluated the responses of AM fungi in a long-term leaf litter addition and removal experiment in a tropical forest in Panama. We described AM fungal communities using 454-pyrosequencing, quantified the proportion of root length colonised by AM fungi using microscopy, and estimated AM fungal biomass using a lipid biomarker. AM fungal community composition was altered by litter removal but not litter addition. Root colonisation was substantially greater in the superficial organic layer compared with the mineral soil. Overall colonisation was lower in the litter removal treatment, which lacked an organic layer. There was no effect of litter manipulation on the concentration of the AM fungal lipid biomarker in the mineral soil. We hypothesise that reductions in organic matter brought about by litter removal may lead to AM fungi obtaining nutrients from recalcitrant organic or mineral sources in the soil, besides increasing fungal competition for progressively limited resources.
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| 5. |
- Williams, Alwyn, et al.
(författare)
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Long-term agricultural fertilization alters arbuscular mycorrhizal fungal community composition and barley (Hordeum vulgare) mycorrhizal carbon and phosphorus exchange
- 2017
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Ingår i: New Phytologist. - : Wiley. - 0028-646X .- 1469-8137. ; 213:2, s. 874-885
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Tidskriftsartikel (refereegranskat)abstract
- Agricultural fertilization significantly affects arbuscular mycorrhizal fungal (AMF) community composition. However, the functional implications of community shifts are unknown, limiting understanding of the role of AMF in agriculture. We assessed AMF community composition at four sites managed under the same nitrogen (N) and phosphorus (P) fertilizer regimes for 55 yr. We also established a glasshouse experiment with the same soils to investigate AMF–barley (Hordeum vulgare) nutrient exchange, using carbon (13C) and 33P isotopic labelling. N fertilization affected AMF community composition, reducing diversity; P had no effect. In the glasshouse, AMF contribution to plant P declined with P fertilization, but was unaffected by N. Barley C allocation to AMF also declined with P fertilization. As N fertilization increased, C allocation to AMF per unit of P exchanged increased. This occurred with and without P fertilization, and was concomitant with reduced barley biomass. AMF community composition showed no relationship with glasshouse experiment results. The results indicate that plants can reduce C allocation to AMF in response to P fertilization. Under N fertilization, plants allocate an increasing amount of C to AMF and receive relatively less P. This suggests an alteration in the terms of P–C exchange under N fertilization regardless of soil P status.
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