| 1. |
- Tyler, Torbjörn, et al.
(författare)
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Climate warming and land-use changes drive broad-scale floristic changes in Southern Sweden
- 2018
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Ingår i: Global Change Biology. - : Wiley. - 1354-1013. ; 24:6, s. 2607-2621
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Tidskriftsartikel (refereegranskat)abstract
- Land-use changes, pollution and climate warming during the 20th century havecaused changes in biodiversity across the world. However, in many cases, the environmental drivers are poorly understood. To identify and rank the drivers currentlycausing broad-scale floristic changes in N Europe, we analysed data from two vascularplant surveys of 200 randomly selected 2.5 9 2.5 km grid-squares in Scania,southernmost Sweden, conducted 1989–2006 and 2008–2015, respectively, andrelated the change in frequency (performance) of the species to a wide range ofspecies-specific plant traits. We chose traits representing all plausible drivers ofrecent floristic changes: climatic change (northern distribution limit, flowering time),land-use change (light requirement, response to grazing/mowing, response to soildisturbance), drainage (water requirement), acidification (pH optimum), nitrogendeposition and eutrophication (N requirement, N fixation ability, carnivory, parasitism,mycorrhizal associations), pollinator decline (mode of reproduction) andchanges in CO2 levels (photosynthetic pathway). Our results suggest that climatewarming and changes in land-use were the main drivers of changes in the flora duringthe last decades. Climate warming appeared as the most influential driver, withnorthern distribution limit explaining 30%–60% of the variance in the GLMM models.However, the relative importance of the drivers differed among habitat types,with grassland species being affected the most by cessation of grazing/mowing andspecies of ruderal habitats by on-going concentration of both agriculture and humanpopulation to the most productive soils. For wetland species, only pH optimum wassignificantly related to species performance, possibly an effect of the increasinghumification of acidic water bodies. An observed relative decline of mycorrhizal species may possibly be explained by decreasing nitrogen deposition resulting in lesscompetition for phosphorus. We found no effect of shortage or decline of pollinatinglepidopterans and bees.
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| 2. |
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| 3. |
- 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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| 4. |
- Hydbom, Sofia, et al.
(författare)
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The use of conservation tillage in an agro-intensive region : results from a survey of farmers in Scania, Sweden
- 2020
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Ingår i: Renewable Agriculture and Food Systems. - 1742-1705. ; 35:1, s. 59-68
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Tidskriftsartikel (refereegranskat)abstract
- Conventional agricultural practices can lead to soil erosion and a reduction in soil organic carbon (SOC) content. It has been suggested that less intensive agricultural practices, such as conservation tillage (including no-till and reduced till without soil inversion) may reduce both erosion and loss of SOC. The aim of this study was to determine whether, and why, conservation tillage is used in Scania, which is one of the most agro-intensive regions in Sweden. We also investigated how information on tillage practices is obtained, why one type of tillage may be favored over another, and whether some farmers are more likely to use conservation tillage. The result of this study will benefit policy makers and researchers by pinpointing factors that influence the use of conservation tillage. To collect data, a questionnaire was sent to farmers in Scania in 2016. We found that the majority of the responding farmers used conservation tillage, and that it was more likely to be used if the farmer was highly educated and spent more than 50% of their annual working time on crop production. The use of conservation tillage was also more common if the farm was large and clay soil dominated. Crop rotation was often highlighted as the most important factor influencing the choice of tillage practice, which may be due to crop species requirements. When asked to compare the consequences of reduced tillage and plowing, the perception of farmers using conservation tillage was in general more positive, indicating skepticism toward the practice of reduced tillage until it had been tried. We show that the use of conservation tillage, sometimes in combination with plowing, is widespread in Scania. However, unless changes in, for example, crop rotation and labor requirements occur, the use of conservation tillage will most likely remain the same as today, or only increase slightly in the near future. Farm enlargement may result in an increased conservation tillage use, and so may efforts to educate advisors, increased opportunities for peer-to-peer meetings, and the development of economically viable small farm solutions. Increased conservation tillage may be part of the solution for sustainable crop production, but drawbacks such as increased pesticide use must be addressed further, as well as factors such as crop rotation development and practical knowledge that influence conservation tillage use at the farm level.
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| 5. |
- Olsson, Ola, et al.
(författare)
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Phosphorus and carbon availability regulate structural composition and complexity of AM fungal mycelium.
- 2014
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Ingår i: Mycorrhiza. - : Springer Science and Business Media LLC. - 1432-1890 .- 0940-6360. ; 24:6, s. 443-451
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Tidskriftsartikel (refereegranskat)abstract
- The regulation of the structural composition and complexity of the mycelium of arbuscular mycorrhizal (AM) fungi is not well understood due to their obligate biotrophic nature. The aim of this study was to investigate the structure of extraradical mycelium at high and low availability of carbon (C) to the roots and phosphorus (P) to the fungus. We used monoxenic cultures of the AM fungus Rhizophagus irregularis (formerly Glomus intraradices) with transformed carrot roots as the host in a cultivation system including a root-free compartment into which the extraradical mycelium could grow. We found that high C availability increased hyphal length and spore production and anastomosis formation within individual mycelia. High P availability increased the formation of branched absorbing structures and reduced spore production and the overall length of runner hyphae. The complexity of the mycelium, as indicated by its fractal dimensions, increased with both high C and P availability. The results indicate that low P availability induces a growth pattern that reflects foraging for both P and C. Low C availability to AM roots could still support the explorative development of the mycelium when P availability was low. These findings help us to better understand the development of AM fungi in ecosystems with high P input and/or when plants are subjected to shading, grazing or any management practice that reduces the photosynthetic ability of the plant.
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| 6. |
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| 7. |
- Aliasgharzad, Nasser, et al.
(författare)
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Acidification of a sandy grassland favours bacteria and disfavours fungal saprotrophs as estimated by fatty acid profiling
- 2010
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Ingår i: Soil Biology & Biochemistry. - : Elsevier BV. - 0038-0717. ; 42:7, s. 1058-1064
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Tidskriftsartikel (refereegranskat)abstract
- We have investigated the structure of a microbial community in semi-natural sandy grassland in southeast Sweden. The sand is rich in lime, but in most places the soil is decalcified in the upper layers, and therefore this site shows a large variation in pH within short distances. We collected samples at three different soil depths (0-10 cm, 10-20 cm and 20-30 cm) and found the pH to range from 5 to 8 in the topsoil and from 4.5 to 9.5 in the deepest layer. The abundance of saprophytic fungi and bacteria was investigated using signature phospholipid fatty acids and arbuscular mycorrhizal fungi (AMF) using the neutral lipid fatty acid 16:1 omega 5. The PLFA pattern of the topsoil was different from that in the other two layers, as indicated by principal component analysis. The saprotrophic fungi were associated with high pH, and bacteria with low pH in these sandy soils. No relation was found between pH and AMF in the topsoil, while a positive relation was found in the deepest soil layer. The saprophytic fungi-to-bacteria ratio was constant with depth, while the AMF-to-bacteria ratio increased with soil depth. The results showed that high soil pH favoured fungal saprophytes in sandy grasslands and that AMF are relatively more abundant than the other two groups in deeper soil layers: particularly so when the pH is high. (C) 2010 Elsevier Ltd. All rights reserved.
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| 8. |
- Aliasgharzad, Nasser, et al.
(författare)
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Lack of arbuscular mycorrhizal colonisation in tea (Camellia sinensis L.) plants cultivated in Northern Iran
- 2011
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Ingår i: Symbiosis. - : Springer Science and Business Media LLC. - 0334-5114 .- 1878-7665. ; 55:2, s. 91-95
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Tidskriftsartikel (refereegranskat)abstract
- Soil and roots associated with different tea clones and nearby weeds (Veronica sp., Setaria sp., Salvia sp., Senecio sp. and Tripogon sp.) were sampled for arbuscular mycorrhizal fungi (AMF) in the tea gardens of Northern Iran. Spores were searched for in the soil and AMF colonisation determined microscopically and fatty acid signatures in roots was determined. Root samples from mycorrhizal and non-mycorrhizal clover were used as positive and negative controls. AMF spores were abundant in the tea garden soils; the genera Glomus and Acaulospora dominated. Microscopic observations of stained tea roots showed no sign of AMF. To confirm this, the roots were analysed for fatty acid signature compounds. The average level of PLFA 16:1 omega 5 as signature molecule for AMF in tea roots was 2 nmol g(-1) dry root, while the NLFA 16: 1 omega 5 was not detectable. In mycorrhizal and non-mycorrhizal clover roots, the PLFA 16:1 omega 5 was 141 and 5.74 nmol g(-1) dry root, respectively. In roots of weeds in tea plantations, the amount of PLFA 16:1 omega 5 was in the range 4.9 to 31.1 nmol g(-1) dry root. Thus, there was no evidence for AMF association in tea roots and weeds are thought to be the source of the spores in the soils. Finally, no mycorrhizal colonisation was found when tea plant seedlings were inoculated with AMF in pot cultures.
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| 9. |
- Antonsen, H, et al.
(författare)
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Relative importance of burning, mowing and species translocation in the restoration of a former boreal hayfield: responses of plant diversity and the microbial community
- 2005
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Ingår i: Journal of Applied Ecology. - : Wiley. - 1365-2664 .- 0021-8901. ; 42:2, s. 337-347
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Tidskriftsartikel (refereegranskat)abstract
- 1. The extensive loss of species-rich grasslands in Europe as a result of agricultural intensification has triggered a desire to recreate more diverse and natural grassland systems in set-aside fields. Appropriate management and species introductions are necessary to overcome residual soil fertility, lack of suitable plant propagules and dominance of undesirable invasive species. 2. A field experiment was performed in a boreal former hayfield to test the effect of turf inoculation, mowing (twice annually) and spring burning. We surveyed changes in plant diversity, composition and productivity over a 3-year period. Signature fatty acids and soil respiration measurements were employed to survey changes in the soil community. 3. Few changes in the vegetation and soil communities could be related to inoculation of turf monoliths. Most of the measured variables in mown plots differed from the set-aside (control) plots, while burned plots displayed mainly similar responses. Mowing increased plant species richness and diversity, mainly by enhancing the number and frequency of forb species. Small-statured forb species were promoted by mowing, whereas tall leafy grasses declined. Effects of mowing on soil communities comprised an increased soil respiration and stimulation of arbuscular mycorrhizal fungi. 4. Synthesis and applications. The results demonstrate the importance of reducing sward height in order to promote plant species coexistence in former boreal hayfields. In such systems, eliminating accumulated litter by spring burning has little influence on species composition when the sward is allowed to grow tall. Mowing is therefore the most efficient way of enhancing biodiversity. The results also show that mowing-mediated changes in above-ground plant communities may stimulate below-ground symbiotic micro-organisms, potentially resulting in a positive feedback on ecosystem development.
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| 10. |
- 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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| 11. |
- 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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| 12. |
- Bao, Xiaozhe, et al.
(författare)
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Arbuscular mycorrhiza under water — Carbon‒phosphorus exchange between rice and arbuscular mycorrhizal fungi under different flooding regimes
- 2019
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Ingår i: Soil Biology and Biochemistry. - : Elsevier BV. - 0038-0717. ; 129, s. 169-177
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Tidskriftsartikel (refereegranskat)abstract
- Arbuscular mycorrhizal fungi (AMF) are commonly present in wetlands, but their functional role there is not well understood. We have quantified the carbon (C) allocation from rice to AMF under different flooding regimes, using stable isotope labeling (13CO2), and assessed the potential phosphorus (P) delivery from AMF to rice by profiling the expression of plant and fungal P transporter genes. The results showed that the plant-assimilated C was allocated to AMF under all flooding regimes, as evidenced by the significant enrichment of 13C in the AMF signature fatty acids. The plant C allocation to AMF declined at increased flooding intensity, and was strikingly greater at the growth stage when the rice plants had a higher nutrient requirement. The gene expression profiles and rice P levels strongly indicated that a considerable amount of P was transported to plants via the mycorrhizal pathway under wetland conditions, although AMF colonization did not improve rice growth. This work provides the first solid evidence of C‒P exchange in AM symbiosis under flooded conditions, although it is reduced compared to non-flooded conditions. Nonetheless, this means that AMF may have an important function in wetlands, which opens new perspectives on the application of symbiotic AMF in wetlands.
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| 13. |
- Barceló, Milagros, et al.
(författare)
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Mycorrhizal tree impacts on topsoil biogeochemical properties in tropical forests
- 2022
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Ingår i: Journal of Ecology. - : Wiley. - 0022-0477 .- 1365-2745. ; 110:6, s. 1271-1282
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Tidskriftsartikel (refereegranskat)abstract
- In tropical regions, the patterns of carbon (C) and nutrient properties among ecosystems dominated by distinct mycorrhizal associations are unknown. We aim to reveal whether the dynamics differ and the ecological drivers and ecosystem functioning implications of such differences. Based on a dataset of 97 tropical forest sites, we related EcM trees abundance (as a proxy for the transition from AM to EcM trees dominance) to different topsoil properties, climatic conditions and microbial abundance proxies through Generalized Additive Models. Higher abundances of EcM trees were correlated with higher topsoil concentrations of total nitrogen and C, extractable phosphorus and potassium, δ13C, mean annual temperature, precipitation, microbial (bacterial and fungal) biomass and the relative abundance of saprotrophic fungi. Synthesis. Our results reveal consistent differences in carbon and nutrient content between arbuscular mycorrhizal (AM-) and EcM-dominated vegetation across the tropical biome, pointing to lower soil fertility and lower rates of C and nutrient transformation processes in EcM-dominated forests. These patterns associate with lower topsoil C accumulation when compared to AM vegetation, which contrasts with patterns reported for temperate forests. We suggest that different mechanisms of soil organic matter accumulation explain the contrasting impacts of EcM dominance on topsoil properties of temperate and tropical biomes. Global vegetation and C models should account for the contrasting impacts of distinct mycorrhizal vegetation in different climatic zones.
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| 14. |
- Barin, Mohsen, et al.
(författare)
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Abundance of arbuscular mycorrhizal fungi in relation to soil salinity around Lake Urmia in northern Iran analyzed by use of lipid biomarkers and microscopy
- 2013
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Ingår i: Pedobiologia. - : Elsevier BV. - 1873-1511 .- 0031-4056. ; 56:4-6, s. 225-232
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Tidskriftsartikel (refereegranskat)abstract
- Saline soils around Lake Urmia in northern Iran constitute a stressed environment for plants and microbial communities, including arbuscular mycorrhizal (AM) fungi. Soil and root samples were collected from fields cultivated with the glycophytes Allium cepa L. and Medicago sativa L, and sites dominated by the halophyte Salicornia europaea L. Soil and root samples were analyzed for the AM fungal signature neutral lipid fatty acid (NLFA) 16:1 omega 5. The roots were also examined microscopically for mycorrhizal colonization. Each plant species was sampled across a salt gradient. Microscopic examination showed no AM fungal structures in the roots of S. europaea. The highest root colonization was recorded for M. sativa. The highest NLFA 16:1 omega 5 values were found in soil around M. sativa roots and the lowest in soil around S. europaea roots. We found evidence for stimulation of vesicle formation at moderate salinity levels in M. sativa, which is an indication of increased carbon allocation to mycorrhiza. On the other hand, we found a negative correlation between salinity and arbuscule formation in A. cepa, which may indicate a less functional symbiosis in saline soils. (C) 2013 Elsevier GmbH. All rights reserved.
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| 15. |
- Barin, Mohsen, et al.
(författare)
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Salinity-induced differences in soil microbial communities around the hypersaline Lake Urmia
- 2015
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Ingår i: Soil Research. - 1838-675X. ; 53:5, s. 494-504
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Tidskriftsartikel (refereegranskat)abstract
- Lake Urmia in north-western Iran is one of the largest hypersaline lakes in the world, and agricultural production in the surrounding area is limited by soil salinity. We investigated the effects of salinity on belowground microbial communities in soils collected from fields of cultivated onions (Allium cepa L.) and lucerne (Medicago sativa L.), and sites with the native halophyte samphire (Salicornia europaea L.). We tested the hypotheses that salinity reduces microbial biomass and changes the structure of the microbial community. The physical and chemical properties of soil samples were analysed, and phospholipid fatty acids were identified as signatures for various microbial groups. We found that the organic carbon (OC) content was the dominant determinant of microbial biomass. We also found linear relationships between OC and the biomass of various groups of organisms across the wide salinity gradient studied. Salinity, on the other hand, caused changes in the microbial fatty acid composition that indicated adaptation to stress and favoured saprotrophic fungi over bacteria, and Gram-negative bacteria over Gram-positive. Principal component analysis showed that salinity variables and microbial stress indices formed one group, and OC and microbial biomass another. The importance of OC for high microbial biomass in severely stressed soils indicates that OC amendment may be used to mitigate salt stress and as a method of managing saline soils.
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| 16. |
- Birgander, Johanna, et al.
(författare)
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Activity of temperate grassland plants and symbiotic fungi during the winter - implications for community structure and carbon cycling in a changing climate
- 2012
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Ingår i: Nordic Journal of Botany. - : Wiley. - 0107-055X. ; 30:5, s. 513-521
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Tidskriftsartikel (refereegranskat)abstract
- Several investigations have revealed surprisingly high activities during the winter in vegetation and soil in temperate and subarctic areas. Plants have been found to photosynthesize even under snow cover and at temperatures below freezing, and decomposer microorganisms can function, at low rates, all year around. In temperate grasslands, the vegetation includes winter annual herbs as well as bryophytes, which have the potential to be active and are thus susceptible to changing temperatures during winter. If temperatures stay below freezing and there is a snow cover, an increase in temperatures could in fact decrease the soil temperature due to reduced insulation by snow cover. On the other hand, if winter temperatures initially fluctuate around the freezing point, an increase by a few degrees might produce frost-free conditions. Based on available data, the composition of plant communities are strongly influenced by temperature conditions in the preceding winter. We conclude that the winter season in grasslands needs more research attention, to start to resolve which species are active and how they respond to a changing climate.
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| 17. |
- 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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| 18. |
- Birgander, Johanna, et al.
(författare)
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Temporal patterns of carbon flow from grassland vegetation to soil microorganisms measured using 13C-labelling and signature fatty acids
- 2021
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Ingår i: Plant and Soil. - : Springer Science and Business Media LLC. - 0032-079X .- 1573-5036. ; 462:1-2, s. 245-255
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: We investigated how the C flow from plants to microorganisms varies throughout the year in a temperate grassland. Additionally, we investigated how the C flow relates to saprotrophic activity and vegetation changes. Methods: In situ stable isotope pulse labelling (13CO2) was employed to estimate the flow of recently plant-derived C to soil microorganisms by using signature fatty acids. Bacterial and fungal growth was estimated using radio-labelling in laboratory incubations. Results: The C flow from plants to arbuscular mycorrhizal (AM) fungi peaked during the warmer parts of the year, but saprotrophic microorganisms showed little temporal variation in C flow. Also saprotrophic fungi received considerable amounts of C from plants throughout the year. Bacterial and fungal growth showed temporal variation with a growth peak in August for both. This suggests a shift in the C source from mainly rhizosphere C in colder parts of the year, to older C-sources in warmer parts of the year (August). Conclusion: We conclude that AM fungi, saprotrophic fungi and bacteria differ in the amount of recently-fixed C they receive from plants throughout the year. Hence, temporal patterns need to be considered to understand ecosystem functioning. The studied plant community included winter annuals, which potentially maintain a high C flow to saprotrophic fungi during the cold season.
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| 19. |
- Birgander, Johanna, et al.
(författare)
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The responses of microbial temperature relationships to seasonal change and winter warming in a temperate grassland
- 2018
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Ingår i: Global Change Biology. - : Wiley. - 1354-1013. ; 24:8, s. 3357-3367
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Tidskriftsartikel (refereegranskat)abstract
- Microorganisms dominate the decomposition of organic matter and their activities are strongly influenced by temperature. As the carbon (C) flux from soil to the atmosphere due to microbial activity is substantial, understanding temperature relationships of microbial processes is critical. It has been shown that microbial temperature relationships in soil correlate with the climate, and microorganisms in field experiments become more warm-tolerant in response to chronic warming. It is also known that microbial temperature relationships reflect the seasons in aquatic ecosystems, but to date this has not been investigated in soil. Although climate change predictions suggest that temperatures will be mostly affected during winter in temperate ecosystems, no assessments exist of the responses of microbial temperature relationships to winter warming. We investigated the responses of the temperature relationships of bacterial growth, fungal growth, and respiration in a temperate grassland to seasonal change, and to 2 years’ winter warming. The warming treatments increased winter soil temperatures by 5–6°C, corresponding to 3°C warming of the mean annual temperature. Microbial temperature relationships and temperature sensitivities (Q10) could be accurately established, but did not respond to winter warming or to seasonal temperature change, despite significant shifts in the microbial community structure. The lack of response to winter warming that we demonstrate, and the strong response to chronic warming treatments previously shown, together suggest that it is the peak annual soil temperature that influences the microbial temperature relationships, and that temperatures during colder seasons will have little impact. Thus, mean annual temperatures are poor predictors for microbial temperature relationships. Instead, the intensity of summer heat-spells in temperate systems is likely to shape the microbial temperature relationships that govern the soil-atmosphere C exchange.
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| 20. |
- Birgander, Johanna, et al.
(författare)
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Warmer winters increase the rhizosphere carbon flow to mycorrhizal fungi more than to other microorganisms in a temperate grassland
- 2017
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Ingår i: Global Change Biology. - : Wiley. - 1354-1013. ; 23:12, s. 5372-5382
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Tidskriftsartikel (refereegranskat)abstract
- A decisive set of steps in the terrestrial carbon (C) cycle is the fixation of atmospheric C by plants and the subsequent C-transfer to rhizosphere microorganisms. With climate change winters are expected to become milder in temperate ecosystems. Although the rate and pathways of rhizosphere C input to soil could be impacted by milder winters, the responses remain unknown. To address this knowledge-gap, a winter-warming experiment was established in a seminatural temperate grassland to follow the C flow from atmosphere, via the plants, to different groups of soil microorganisms. In situ 13CO2 pulse labelling was used to track C into signature fatty acids of microorganisms. The winter warming did not result in any changes in biomass of any of the groups of microorganisms. However, the C flow from plants to arbuscular mycorrhizal (AM) fungi, increased substantially by winter warming. Saprotrophic fungi also received large amounts of plant-derived C—indicating a higher importance for the turnover of rhizosphere C than biomass estimates would suggest—still, this C flow was unaffected by winter warming. AM fungi was the only microbial group positively affected by winter warming—the group with the closest connection to plants. Winter warming resulted in higher plant productivity earlier in the season, and this aboveground change likely induced plant nutrient limitation in warmed plots, thus stimulating the plant dependence on, and C allocation to, belowground nutrient acquisition. The preferential C allocation to AM fungi was at the expense of C flow to other microbial groups, which were unaffected by warming. Our findings imply that warmer winters may shift rhizosphere C-fluxes to become more AM fungal-dominated. Surprisingly, the stimulated rhizosphere C flow was matched by increased microbial turnover, leading to no accumulation of soil microbial biomass.
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| 21. |
- Fransson, Ann-Mari, et al.
(författare)
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Plantago lanceolata L. and Rumex acetosella L. differ in their utilisation of soil phosphorus fractions
- 2003
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Ingår i: Plant and Soil. - 0032-079X. ; 248:1-2, s. 285-295
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Tidskriftsartikel (refereegranskat)abstract
- To establish relationships between soil phosphorus (P) fractions and leaf P, a mycorrhizal species (Plantago lanceolata L.) was compared with a typically non-mycorrhizal species (Rumex acetosella L.) in a glasshouse experiment. The plants were grown in 40 soils from non-fertilised, abandoned pastures or abandoned arable fields and leaf P concentration were found to be related to various soil P fractions after six weeks of growth. The differences in the P fractions in soil can account for a large share of the variation in leaf P concentration in both species, but the two species differed in their utilisation of P fractions. Leaf P concentration of R. acetosella was more related to extractable soil P than that of P. lanceolata. Rumex acetosella showed a higher maximum P concentration. The P fractions accounting for the largest share of the variation in leaf P concentration was the Bray 1 extractable and the weak oxalate (1 mM) extractable P, and for P. lanceolata also the Na2SO4+NaF extractable P fraction. P extracted with these methods accounted for up to 80% of the variation in P concentration in leaves of R. acetosella and 65% of the variation in leaves of P. lanceolata. More P extractable with weak oxalate, Na2SO4+NaF and strong oxalate (50 mM) was released from the soil than was taken up by the plants during the experimental period. The Bray 1 extractable P fraction, however, decreased in both unplanted and planted soils. Phosphatase release was not induced in any of the plants during the experimental period, indicating that they were not mobilising soil organic P. However, some of the methods extracted a large share of the organic P and still explained much of the variation in leaf P concentration. Mycorrhizal colonisation of P. lanceolata was inversely related to the extractable soil P. The consistently fast P uptake of R. acetosella indicates that this species have a high demand for P. The differences in P utilisation between R. acetosella and P. lanceolata could be caused by their different mycorrhizal status.
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| 22. |
- Gavito, Mayra, et al.
(författare)
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Allocation of plant carbon to foraging and storage in arbuscular mycorrhizal fungi
- 2003
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Ingår i: FEMS Microbiology Ecology. - 1574-6941. ; 45:2, s. 181-187
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Tidskriftsartikel (refereegranskat)abstract
- Foraging strategies, the cost-benefit associated with the search for new resources, have only begun to be explored in arbuscular mycorrhizal fungi (AMF). We show the use of C-13-labelling, via shoot photosynthesis, of the 16: 1omega5 fatty acid biomarker (the dominant and rather specific fatty acid in AMF storage lipids) to study the immediate patterns of carbon allocation to fungal lipids in response to inorganic and organic nutrient amendments. Signature fatty acid measurements, the incorporation of the label and complementary hyphal length density measurements showed that the extraradical mycelium of AMF proliferated in response to all the amendments provided whereas its development into unamended sand was minor in all treatments. We demonstrate the foraging capacity of AMF, linked to plant carbon, through their hyphal proliferation and accumulation of energy reserves.
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| 23. |
- Gavito, Mayra, et al.
(författare)
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Foraging strategies of the external mycelium of the arbuscular mycorrhizal fungi Glomus intraradices and Scutellospora calospora
- 2008
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Ingår i: Applied Soil Ecology. - : Elsevier BV. - 0929-1393. ; 39:3, s. 282-290
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Tidskriftsartikel (refereegranskat)abstract
- The responsiveness of the external mycelium of Glomus intraradices and Scutellospora calospora was tested in a multiple-choice experimental system in which mycelium encountered patches amended with nitrogen (N) or phosphorus (P), either alone or in combination with a host plant. We hypothesised that only AMF mycelium with sufficient supply of photo-synthate from an actively growing host would respond to the amendments provided. Mycelium was allowed to grow either 11 or 21 weeks before we analysed hyphal proliferation in amended patches introduced in mesh bags that were not reached by roots but by foraging mycelium only. Hyphal length, the AMF signature fatty acid 16:1w5, and root colonisation in new host plant seedlings were used to measure AMF growth and resource allocation in the patches. Mycelium from both fungal strains was able to colonise new host roots and sand in all patches but S. calospora was overall more responsive to the amendments than G. intraradices. G. intraradices grew equally into all patches, including the unamended control, whereas S. calospora produced significantly more hyphal length in the patch containing a host plant than in the rest of the patches. Both strains showed lower hyphal growth at the second harvest and mycelium of G. intraradices lost almost entirely its capacity to develop new mycelium in all choices presented. Lipid measurements showed this fungus did not use storage lipids to exploit the patches. S. calospora mycelium had reduced growth and colonisation ability but still showed some growth in the patches at the second harvest. A reduction in the content of NLFA 16:1w5 from the first to the second harvest suggested that S. calospora mycelium likely used storage lipids to sustain proliferation in the patches. The results indicated that S. calospora was more active and used more resources for foraging than G. intraradices; and that external mycelium foraging was maintained mainly with recently acquired plant carbon (C). This supported in general our hypothesis but showed as well that the two AMF strains had different strategies and resource allocation to forage. The overall low response of both AMF to the choices presented suggested that the responsiveness of mycelium searching freely in the substrate is lower than that observed in experimental systems in which the amendments have been placed in close contact with actively growing mycelium fronts in close vicinity with host roots.
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| 24. |
- Gavito, Mayra, et al.
(författare)
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Temperature constraints on the growth and functioning of root organ cultures with arbuscular mycorrhizal fungi
- 2005
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Ingår i: New Phytologist. - : Wiley. - 1469-8137 .- 0028-646X. ; 168:1, s. 179-188
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Tidskriftsartikel (refereegranskat)abstract
- (.) In this study we investigated the effects of temperature on fungal growth and tested whether the differences in fungal growth were related to the effects of temperature on carbon movement to, or within, the fungus. (.) Growth curves and C uptake-transfer-translocation measurements were obtained for three arbuscular mycorrhizal fungi (AMF) isolates cultured within a 6-30 degrees C temperature range. A series of experiments with a model fungal isolate, Glomus intraradices, was used to examine the effects of temperature on lipid body and 33 P movement, and to investigate the role of acclimation and incubation time. (.) Temperature effects on AMF growth were both direct and indirect because, despite clear independent root and AMF growth responses in some cases, the uptake and translocation of 13 C was also affected within the temperature range tested. Root C uptake and, to a lesser extent, C translocation in the fungus, were reduced by low temperatures (< 18 C). Uptake and translocation of 33 P by fungal hyphae were, by contrast, similar between 10 and 25 C. (.) We conclude that temperature, between 6 and 18 C, reduces AMF growth, and that C movement to the fungus is involved in this response.
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| 25. |
- Gormsen, Dagmar, et al.
(författare)
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The influence of collembolans and earthworms on AM fungal mycelium
- 2004
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Ingår i: Applied Soil Ecology. - : Elsevier BV. - 0929-1393. ; 27:3, s. 211-220
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Tidskriftsartikel (refereegranskat)abstract
- Arbuscular mycorrhizal (AM) mycelia are dependent on contact with plant roots for spore formation. In this study, earthworms and collembolans were regarded as potential dispersal vectors of AM fungal spores and hyphae, and we determined how they influenced the extension of AM fungi from host plant roots. Plantago lanceolata seedlings were grown in a mesh bag with an AM inoculurn of dried soil and root pieces from a set-aside agricultural field. The bag was placed in a growth box that was filled with a mixture of irradiated soil and sand, into which fungal hyphae could grow while roots were retained by the mesh. Three treatments with 15 replicates each were established with an addition of either Lumbricus rubellus, Folsomia candida or no soil fauna into the root-free soil. Five replicates of each treatment were harvested after 6, 10 and 15 weeks. The extension of the AM fungi was determined by measuring PLFA 16:1w5 and NLFA 16:1w5 as signature compounds of AM fungal biomass, spore production and mycorrhizal inoculum potential on P lanceolata seedlings. After 10 weeks, all indicators of AM fungal growth showed that the fungi had extended into the whole growth box. Plant shoot biomass of the host plants was greater in the presence of earthworms than other treatments, and the contents of PLFA 16:1w5 were greater in the earthworm than in the collembolan treatment. The reduced amount of PLFA 18:2w6,9 in the collembolan treatment relative to other treatments suggests that saprophytic fungi provided a food source for the collembolans. Spore production and mycorrhizal inoculurn potential were not affected by the presence of soil fauna. We conclude that the biomass of AM fungi was stimulated by earthworms, but that fungal dispersal over 20 cm was not influenced. (C) 2004 Elsevier B.V. All rights reserved.
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